CYCLOHEXENES

CLAIM OF PRIORITY

[0001] The present application claims the benefit of the filing date of US Provisional Application No. 61/423,383 (filed 15 December 2010) the contents of which are hereby incorporated by reference in their entirety.

FIELD OF INVENTION

[0002] The present invention relates to the preparation of benzene 1 ,4-dicarboxylate compounds by continous dehydrogenation of 1 ,4-dicarboxylate based cyclohexene compounds.

BACKGROUND OF THE INVENTION

[0003] Terephthalic acid and trimellitic acids comprise a benzene ring with carboxylate groups at the 1 and 4 and the 1, 2, and 4 positions respectively. Phenylterephthalic acid comprises a benzene ring with carboxylate groups at the 1 and 4 positions and a phenyl group at the 2 position. These acids and their carboxylate derivatives are useful in a variety of commercial products such as polyesters, polyamides and plasticizers which are useful in a variety of uses, such as fibers, textiles, high performance plastics and the like. At the present time these acids and their carboxylate derivatives are synthesized commercially from petroleum based starting materials, such as p-xylene. Due to volatility in hydrocarbon markets and the limited amount of hydrocarbons available for future use it is desirable that methods of preparing such important compounds from renewable resources be developed.

[0004] Some large agricultural crops such as corn and sugar cane and the by-products associated with their harvesting and processing which cannot be used as a food source contain starch or cellulosic materials which can be broken down to simple sugars which can then be converted to useful products. See, for instance, Frost et. al. US 5,629,181; Frost US 5,168,056; Frost et. al. US 5,272,073; Frost US Patent publication 2007/0178571, and Frost et. al. US 5,616,496, incorporated herein by reference.

[0005] There is a need for improved processes for preparing such compounds from starting materials that can be made or derived from renewable resources, such as, for example, biomass or simple sugars which can then be derived from biomass. SUMMARY OF THE INVENTION

[0006] The present invention provides a method for preparing compounds containing at least one benzene ring and carboxylate derivatives at the 1 and 4 positions of the benzene ring, and optionally at the 2 position of the benzene ring and which also contain a detectable amount of carbon 14 ( ¹⁴ C) and at least 6 carbon atoms per monomer unit derived from renewable resources. Such compounds include substituted and unsubstituted terephthalic acid and carboxylate derivatives thereof. Substituted terephthalates include compounds having a benzene ring with carboxylic acid groups or carboxylate derivatives thereof at the 1 and 4 position wherein the benzene ring may be substituted on other carbons. In one preferred embodiment, the benzene ring is substituted at the 2 position. One preferred subsituent at the 2 position is a carboxylic acid or carboxylate derivative thereof. Another preferred group of substituents comprise a phenyl, an alkyl or a halogen group. Included in more preferred substituted terephthalates are trimellitic acid and phenylterephthalic acid. As used herein, the term carboxylate refers to any group which contains a carbonyl group (C=0) wherein the carbonyl group is bonded to an anion so as to form a salt, to a heteroatom, such as oxygen, nitrogen, sulfur or one or more halogens. The heteroatom may be further bonded by a covalent bond to one or more other groups, such as hydrogen or hydrocarbyl groups which may optionally contain one or more heteroatoms, or may be electronically bonded to a cation to form a salt. Alternatively, the carboxylate derivative can be a nitrite. Preferably, the carboxylate is an acyl halide, carboxylic acid, amide, ester, thiol ester, mercaptocarbonyl, anhydride, nitrile, salt with an anion or salt with a cation. Preferred cations include alkali metals and unsubsituted and hydrocarbyl substituted ammonium ions. The term carboxylate as used herein includes the carboxylic acid form of carboxylate derivatives. The term carboxylic acid or acid is used herein in contexts wherein the acid form is distinguished from other carboxylate forms. The particular use hereinafter is clear from the context. The method comprises: contacting the cyclohexene ring containing compounds having carboxylate derivatives at the 1 and 4, and optionally the 2, position with one or more dehydrogenation catalysts, optionally in the presence of one or more oxidants, in a continuous flow mode under conditions such that compounds containing an aromatic ring with carboxylate derivatives at the 1 and 4 position, and optionally the 2 position, are prepared. Where there are carboxylate derivatives at the 1 and 4 position, the compounds are referred to herein as terephthalic acid or carboxylate derivatives thereof. Where the final compounds additionally contain a carboxylate at the 2 position of the aromatic ring in addition to the carboxylate derivatives at the 1 and 4 positions, the compounds are referred to herein as a trimellitic acids or carboxylate derivatives thereof. In a preferred embodiment, the carboxylate derivatives are esters of the carboxylic acids, preferably hydrocarbyl carboxylates. [0007] In another embodiment the invention is a method for preparing a polyester comprising: a) obtaining microbially-derived muconic acid or muconic acid; b) optionally forming one or more dihydrocarbyl muconates from muconic acid; c) contacting the muconic acid or one or more dihydrocarbyl muconates with one or more dienophiles at under conditions such that the one or more muconic acid or dihydrocarbyl muconates and the one or more dienophiles form a cycloaddition product comprising a cyclohexene ring or a cyclohexadiene ring; and exposing the cycloaddition product comprising a cyclohexene ring or a cyclohexadiene ring to dehydrogenation conditions in a continuous manner.

[0008] In one preferred embodiment, the invention is a method for preparing a substituted or unsubstituted benzene 1,4 dicarboxylate (terephthalic acid or terephthalate carboxylate ester based compound) comprising a) contacting cis,cis muconic acid and iodine in the presence of ultraviolet light in a protic or aprotic solvent at a temperature for a period of time such that the cis,cis muconic acid isomerizes to the trans,trans muconic acid; b) recovering the trans,trans muconic acid; and c) contacting the trans,trans muconic acid with one or more alkanols in the presence of one or more strong acids under conditions that one or more trans,trans dialkyl muconates are formed; d) contacting the one or more dialkyl muconates with one or more dienophiles at a temperature of about 130°C to about 170°C under conditions such that the dialkyl muconates and dienophiles form one or more cyclohexene ring containing compounds; and contacting the one or more cyclohexene ring containing compounds with one or more dehydrogenation catalysts, optionally in the presence of one or more oxidants, in a continuous flow mode under conditions such that one or more compounds containing a benzene ring with hydrocarbyl carboxylate esters or carboxylic acid groups at the 1 and 4 position are prepared.

[0009] In a preferred embodiment the fluid mixture comprises one or more cyclohexene ring containing compounds with carboxylate derivatives at the 1 and 4, and optionally at the 2 position, dissolved in a solvent which is inert under reaction conditions. Preferably, the dehydrogenation catalyst is disposed on a support. Preferably, the fluid mixture is contacted with the dehydrogenation catalyst in the presence of an inert gas in sufficient amount to significantly reduce the amount of hydrogen gas that reacts with the cyclohexene ring containing compounds.

[0010] In one preferred embodiment the cyclohexene ring containing compounds are prepared by contacting one or more muconic acid dienes or carboxylate derivatives thereof with one or more dienophiles under conditions such that the one or more muconic acid dienes or carboxylate derivatives thereof and one or more dienophiles form one or more cyclohexene ring containing compounds. Preferably, the step of contacting one or more muconic acid dienes or carboxylate derivatives thereof with one or more dienophiles and the dehydrogenation step are performed in the same solvent.

[0011] In a preferred embodiment, the one or more dienophiles are reacted with one or more trans,trans muconic acids or carboxylate derivatives thereof, wherein the one or more of muconic acid or carboxylate derivates thereof are prepared by a process including the step of isomerizaton of one or more of cis,cis muconic acid or carboxylate derivatives thereof and cis,trans muconic acid and carboxylate derivatives thereof to trans,trans muconic acid and carboxylate derivatives thereof. Preferably, the one or more of muconic acid, or carboxylate esters thereof, are prepared from one or more of cis,trans and cis, cis muconic acid which process comprises contacting one or more of cis,cis and cis,trans muconic acids or carboxylate esters thereof, with one or more isomerization catalysts, a source of ultraviolet radiation or both in a solvent for a period of time such that the cis,cis and/or cis,trans muconic acid, or carboxylate esters thereof, isomerize to trans,trans muconic acid or carboxylate esters thereof.

[0012] In another embodiment the invention relates to the products prepared by the processes described herein. In those embodiments wherein the starting muconic acid is prepared from biomass, the resulting products of the process contain a significant percentage of carbon derived from renewable resources. Such products are unique because the products contain a detectable trace or amount of ¹⁴ C, and preferably up to about I part per trillion, as determined according to ASTM D6866-08. The resulting products preferably contain 6 or greater carbons, more preferably 8 or greater carbons, derived from renewable resources, such as biomass, preferably by microbial synthesis. The resulting products are prepared from renewable resources prepared by microbial synthesis. In embodiments wherein the products are utilized to prepare polymers, the monomer units preferably contain 6 or greater carbons, and more preferably 8 or greater carbons, derived from renewable resources, such as biomass.

BRIEF DESCRIPTION OF FIGURES

[0013] Figure 1 shows the concentration of materials at various time intervals in Example 27.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] The following discussion applies to the teachings as a whole. Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", inclusive of at least the specified endpoints. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. References to the term "consisting essentially of to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist essentially of the elements, ingredients, components or steps. Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps. Likewise, any reference to "first" or "second" items is not intended to foreclose additional items (e.g., third, fourth, or more items); such additional items are also contemplated, unless otherwise stated. All references herein to elements or metals belonging to a certain Group refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc., 1989. Any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups. Monomer units as used herein refer to the repeating unit of a polymeric structure. Derived from means prepared from or prepared using. Hydrocarbyl as used herein refers to a group containing one or more carbon atom backbones and hydrogen atoms, which may optionally contain one or more heteroatoms. Where the hydrocarbyl group contains heteroatoms, the heteroatoms may form one or more functional groups well known to one skilled in the art. Hydrocarbyl groups may contain cycloaliphatic, aliphatic, aromatic or any combination of such segments. The aliphatic segments can be straight or branched. The aliphatic and cycloaliphatic segments may include one or more double and/or triple bonds. Included in hydrocarbyl groups are alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, alkaryl and aralkyl groups. Cycloaliphatic groups may contain both cyclic portions and noncyclic portions. Substituted terephthalates include compounds having a benzene ring with carboxylic acid groups or carboxylate derivatives thereof at the 1 and 4 position wherein the benzene ring may be substituted on other carbons. As used herein, the term carboxylate refers to any group which contains a carbonyl group (C=0) wherein the carbonyl group is bonded to an anion so as to form a salt, to a heteroatom, such as oxygen, nitrogen, sulfur or one or more halogens. The heteroatom may be further bonded by a covalent bond to one or more other groups, such as hydrogen or hydrocarbyl groups which may optionally contain one or more heteroatoms, or may be electronically bonded to a cation to form a salt. Alternatively, the carboxylate derivative can be a nitrile. Preferably, the carboxylate is an acyl halide, carboxylic acid, amide, ester, thiol ester, mercaptocarbonyl, anhydride, nitrile, salt with an anion or salt with a cation. Preferred cations include alkali metals and unsubsituted and hydrocarbyl substituted ammonium ions. The term carboxylate as used herein includes the carboxylic acid form of carboxylate derivatives. The term carboxylic acid or acid is used herein in contexts wherein the acid form is distinguished from other carboxylate forms. The particular use hereinafter is clear from the context. Where there are carboxylate derivatives at the 1 and 4 position, the compounds are referred to herein as terephthalic acid or carboxylate derivatives thereof. Where the Final compounds additionally contain a carboxylate at the 2 position of the aromatic ring in addition to the carboxylate derivatives at the 1 and 4 positions, the compounds are referred to herein as a trimellitic acids or carboxylate derivatives thereof. Tn a preferred embodiment, the carboxylate derivatives are esters of the carboxylic acids, preferably hydrocarbyl carboxylates.

[0015] The present invention pertains generally to the synthesis of monomelic materials. In one aspect, the invention is directed at synthesis that uses as a source of at least one starting material a biomass-derived product. For example, one preferred approach that is addressed herein pertains to the use of at least one dicarboxylic acid (e.g., muconic acid) or carboxylate derivative thereof derived from, or derived from, microbial synthesis. Examples of microbial synthesis processes taught in the art include, without limitation. Frost et al. U.S. Patent No. 5,616,496, International Patent Publication No. WO2011/08531 1, and U.S. Patent Publication No. 201 1/0124911, each of which are incorporated herein by reference. In one aspect the invention relates to the formation of one or more carboxylate derivatives of one or more cyclohexene ring containing compounds. In particular, the teachings herein describe reactions for dehydrogenating one or more cyclohexene containing compounds (e.g., derived from one or more muconic acids or carboxylate derivatives thereof) to form cyclohexene dehydrogenation products thereof (e.g. substituted benzene products) using a continuous dehydrogenation process. Preferably, the dehydrogenation products are one or more products selected from substituted or unsubstituted terephthalic acid or carboxylate derivatives thereof.

[0016] Another aspect of the invention relates to the formation of one or more cyclohexenes from one or more muconic acids or carboxylate derivatives thereof. For example, pursuant to this aspect a trans,trans muconic acid or one or more carboxylate derivatives thereof (e.g., the muconic acid or a carboxylate derivative thereof described above, optionally derived from biomass), preferably in the trans, trans isomeric form, may be reacted to form a cyclohexene having a carboxylate derivatives located in at least two positions, such as the 1 and 4 positions, of the cyclohexene rings. [0017] The processes of the invention include the preparation of compounds having at least one benzene ring and carboxylatcs at the 1 and 4, and optionally at the 2 position of the benzene ring. In preferred embodiments these products can be referred to as substituted or unsubstituted terephthalic acid or carboxylate derivatives thereof. Several other process steps may be included with this step. The following steps may be included in the preparation of the desired products: conversion of sugars, carbohydrates or cellulosic matter contained in biomass to muconic acid, typically the cis,cis and/or cis.trans isomer of muconic acid; isomerization of cis,cis and/or cis,trans muconic acid, or an ester thereof, to the trans. trans isomer; esterification of the one or more muconic acids to form one or more dihydrocarbyl esters of muconic acid; conversion of the one or more carboxylic acids or carboxylate esters thereof to another carboxylate derivative form; reaction of one or more muconic acids or carboxylate derivatives thereof with one or more dienophiles to form of one or more cyclohexene ring containing compounds having carboxylates at the 1 and 4, and optionally at the 2 position, of the rings; dehydrogenation of the one or more cyclohexene compounds to form benzene ring containing compound; and esterification of one or more benzene or cyclohexene compounds having carboxylate groups at the 1 and 4, and optionally at the 2 position.

[0018] Muconic acid can be prepared from biomass by any means known in the art, including the process described in Frost et al. US Patent 5,616,496, International Patent Publication No. WO2011/085311, and U.S. Patent Publication No. 201 1/0124911. The resulting product is typically recovered by filtration techniques, preferably in the form of the cis,cis isomer of muconic acid, or as a mixture of cis,cis and cis.trans isomers. The cis,cis and cis.trans isomers of muconic acid do not generally react with dienophiles in an efficient manner and it is preferably to be isomerize muvconic acid to the trans,trans isomer for use in the reaction with dienophiles as described herein. Other methods of preparing muconic acid are known and muconic acid prepared by these processes can be used as the starting material in the processes of this invention. Preferably, the muconic acid used in the process steps described herein is prepared from biomass and more preferably by a microbial synthesis itself utilizing biomass or compounds dereived from biomass such as, for example carbohydrates.

[0019] In the embodiment where cis,cis and/or cis.trans muconic acids are used as the starting materials, they may be used in crude form or in purified form. When used in crude form it is preferred to remove microorganisms used in the preparation of muconic acid from sugars, starches, cellulosic materials and the like. The microorganisms are removed to prevent their interference with the various synthetic steps performed in the process. The microorganisms may be removed by means well known in the art, such as by filtration. The crude muconic acids may contain proteins, inorganic salts and the like. In certain processing sequences, as described hereinafter, it is preferable to purify the muconic acids. Preferably, purified cis,cis and/or cis.trans muconic acid are used for these processes: for the in situ isomerization of muconic acid and subsequent reaction with a dienophile in the same reaction vessel and where the cis,cis or cis.trans isomers are esterified before isomerization to the trans,trans isomeric form.

[0020] Crude cis,cis and/or cis,trans muconic acid can be purified by dissolution in water or organic solvents and subsequent recrystallizaton from solution. Generally, the crude muconic acid and water or organic solvents need to be heated to dissolve the muconic acid. Cooling to ambient temperature, about 23°C, typically results in precipitation of purified muconic acid. Cooling to less than ambient, down to about 0°C facilitates higher recovery or yields of purified muconic acids. The mixture of crude muconic acid and water or organic solvent is preferably heated to about 50°C or greater to dissolve the muconic acid. The upper limit on heating of the mixture is limited by decomposition of the muconic acid and practicality. Preferred organic solvents for this process step are polar aprotic solvents, with alkanols and ethers such as tetrahydrofuran (THF) being more preferred. Alkanols useful as solvents comprise straight and branched hydrocarbon chain further containing compounds further one or more, preferably one, hydroxyl groups. Preferred alkanols are C _1-6 straight and branched chain alkanols, with methanol, ethanol, and isopropanol most preferred. After precipitation of the purified muconic acid, the solvent is decanted off and the solid muconic acid is further dried, that is the residual solvent is removed by evaporation under reduced pressure. Preferably, the feedstock for this process is crude cis,cis muconic acid.

[0021] cis,cis Muconic acid can be isomerized directly to trans,trans muconic acid or isomerized to cis.trans muconic acid and then the cis.trans muconic acid can be isomerized to trans,trans muconic acid. Mixtures of cis,cis and cis.trans muconic acid can be isomerized to trans,trans muconic acid. Either muconic acid, or a carboxylate thereof, may be reacted with dienophiles to prepare the desired compounds. When a carboxylate derivative is used, the muconic acid can either be isomerized first, or converted to the carboxylate form first, and then the other process step performed subsequently.

[0022] In one embodiment, the cis,cis muconic acid, or carboxylate thereof, may be converted to the cis.trans isomer in a discrete step. In such discrete step, the cis,cis muconic acid or carboxylate thereof is dissolved or dispersed in water and exposed to elevated temperatures to convert the cis,cis muconic acid, or carboxylate thereof, to the cis.trans isomer. Preferably this is performed in an acidic water reaction mixture. More preferably the pH of the reaction mixture is about 4 to about 5.5, most preferably about 4. Temperatures which may be used for this process steps include any temperature at which the isomerization proceeds. In one embodiment, the process is performed under reflux conditions. This process step is performed as long as required to convert the desired amount of cis,cis muconic acid or carboxylate thereof to the cis,trans isomer. Preferably, this process step is performed for about 10 minutes or greater. Preferably, this process step is performed for about 60 minutes or less and more preferably about 30 minutes or less. The pH of the reaction mixture, the reaction temperature and the reaction time are interdependent. Preferably, the temperature, pH and reaction time are chosen to minimize the time required to perform the isomerization, while avoiding unwanted reactions or impractical operations.

[0023] In one embodiment, the starting muconic acid or carboxylate derivative thereof, are contacted with one or more isomerization catalysts, a source of ultraviolet radiaton or both, in solvent to form the trans,trans muconic acid. The starting muconic acid or carboxylate derivative thereof can be in the cis,cis, or cis.trans isomeric form or any combination of both isomeric forms. Any source of ultraviolet radiation which generates a radical under the conditions of the process may be used. Among preferred sources of ultraviolet radiation are light bulbs, xenon lamps, medium pressure mercury lamps or electrodeless lamps, natural light and the like. To enhance radical formation, where the radical former is ultraviolet radiation, a photoinitiator may be used in combination with the ultraviolet radiation source. Any commonly known photointiator useful with olefinically unsaturated compounds may be used in the processes described herein. Included in photoinitiators useful in this process are those disclosed in Baikerikar et al. US Patent Publication 2007/0151178 paragraphs 0029, 0030 and 0032 incorporated herein by reference. Among preferred photointiators are alpha aminoketones, alpha hydroxyketone, phosphine oxides, phenylglyoxalates, thioanthones, benzophenones, benzoin ethers, oxime esters, amine synergists, maleimides, mixtures thereof and the like. Isomerization catalysts include any compounds which form radicals in unsaturated compounds when exposed to the reaction conditions, preferably under thermal conditions. Any isomerization catalyst with a suitable half life at the reaction temperatures of this process step can be used. Among preferred isomerization catalysts are compounds contained in the following classes: elemental halogens; dialkyl peroxides, such as di-tertiary- butyl peroxide, 2,5-dimethyl-2,5-di-tertiary-butyl-peroxyhexane, di-cumyl peroxide; alkyl peroxides, such as, tertiary-butyl hydroperoxide, tertiary-octyl hydroperoxide, cumene hydroperoxide; aroyl peroxides, such as benzoyl peroxide; peroxy esters, such as tertiary- butyl peroxypivalate, tertiary-butyl perbenzoate; and azo compounds, such as azo-bis- isobutyronitrile, and the like. More preferred compounds useful as isomerization catalysts are elemental halogens; with bromine, chlorine and iodine even more preferred; and iodine most preferred. Alternatively, the isomerization catalyst can be a hydrogenation catalyst as described hereinafter. Among preferred hydrogenation catalysts useful as an isomerization catalyst are nickel, platinum and palladium in homogeneous and heterogeneous forms. More preferred are heterogeneous catalysts, with carbon as the most preferred support. A most preferred catalyst for this purpose is palladium on carbon. The amount of isomerization catalyst used is that amount which catalyzes the isomerization of the muconic acid or a carboxylate derivative thereof. If too little is used the reaction does not proceed at a practical rate. If too much is used the isomerization catalyst may add to one of the double bonds of the muconic acid or carboxylate derivative thereof. The isomerization catalysts are preferably present in the reaction mixture in an amount of about 0.0001 equivalents or greater based on the equivalents of muconic acid or carboxylate derivatives thereof, more preferably about 0.001 equivalents or greater and most preferably about 0.005 equivalents or greater. The isomerization catalysts are preferably present in the reaction mixture in an amount of about 1.0 equivalent or less based on the equivalents of the muconic acid or carboxylates thereof, more preferably about 0.1 equivalents or less and about 0.01 equivalents or less. Any temperature at which isomerization of the muconic acid or carboxylates thereof to the trans,trans isomeric form occurs may be used. Preferably, the temperature is about 23°C or greater and most preferably about 60°C or greater. Preferably, the temperature is about 150°C or less, more preferably about 120°C or less and most preferably about 100°C or less. This process step is preferably performed at ambient temperatures or elevated temperatures. The limiting factor is solubility of the starting muconic acid or carboxylates thereof in the solvents. Preferably, the solvent is saturated with muconic acid or one or more carboxylate derivatives thereof. The use of elevated temperatures renders the process more efficient by allowing a greater amount of starting muconic acid or carboxylates thereof to contact the isomerization catalyst. Preferably this process step is performed in a solvent. Any solvent which dissolves or disperses the reactants and which does not interfere in the desired reaction may be used for this step. Preferably, the solvent is polar and may be protic or aprotic. Protic in regard to a solvent means the solvent has a proton which freely dissociates, such as an active hydrogen. Aprotic in regard to a solvent means the solvent does not have a proton which freely dissociates. Among preferred solvents are cyclic ethers, acyclic ethers, acetonitrile, dimethyl sulphoxide, N-methylpyrrolidone, ketones, alkyl acetates, alkanols or dimethylformamide and the like. More preferred solvents include C _1-4 alkanols, cyclic ethers, acyclic ethers, ethyl acetate, acetone and acetonitrile. This process step is performed as long as required to convert the desired amount of cis,cis and/or cis,trans muconic acid or carboxylate thereof to the trans,trans isomer. In one preferred embodiment wherein cis.trans muconic acid is the starting material, the solvent used is aprotic and is more preferably an aprotic solvent from which trans,trans muconic acid precipitates at ambient temperatures. In this embodiment, the preferred solvents are cyclic ethers, alkyl acetates, and nitriles; with tetrahydrofuran, alkyl substituted tetrahydrofuran , dioxane, and acetonitrile more preferred; and tetrahydrofuran and methyl tetrahydrofuran most preferred. In a preferred embodiment, the starting muconic acid or carboxylate derivatives thereof are contacted with an isomerization catalyst and a source of ultraviolet radiation at elevated temperatures. The trans,trans muconic acid or carboxylate derivatives thereof are insoluble in the preferred solvents and precipitate from the reaction mixture. It can be recovered by simple removal, for instance by decantation, of the solvent from the reaction mixture. Preferably, the yield of trans,trans muconic acid or carboxylate thereof is about 80 percent by weight or greater based on the weight of the starting muconic acid or ester thereof, more preferably about 90 percent by weight or greater and most preferably about 99 percent by weight or greater. Preferably, the trans,trans muconic acid or carboxylate thereof recovered exhibits a purity of about 99 percent by weight or greater. Preferably the trans,trans muconic acid or carboxylate thereof exhibits a detectable trace of ¹⁴ C and more preferably up to about 1 part per trillion of ¹⁴ C. In a preferred embodiment, the recovered trans,trans muconic acid or carboxylate thereof has about 6 carbon atoms or greater derived from renewable resources such as biomass.

[0024] In the embodiment wherein muconic acid, or an carboxylate thereof, is in the cis,trans isomeric arrangement, a preferred means of converting the cis,trans muconic acid, or carboxylate thereof, to the trans,trans muconic acid or an ester thereof comprises contacting the cis.trans muconic acid, or an carboxylate thereof, with an isomerization catalyst in an organic solvent. This is because cis.trans muconic acid or an carboxylate thereof exhibit a higher solubility in organic solvents than the cis,cis and trans,trans isomers. In this process step the preferred carboxylate derivative is an ester.

[0025] Muconic acid and the esters of muconic acid can be represented by the following formulas

wherein R ¹ is independently in each occurrence hydrogen, a hydrocarbyl group optionally containing a heteroatom containing functional group wherein the hydrocarbyl group does not interfere in the formation of a cyclohexene compound.

[0026] Muconic acid is esterified by contact with an eslerifying agent under conditions that a hydrocarbyl group replaces the hydrogen on the oxygen of the carboxylic acid. The esterifying agent can be any compound which under the reaction conditions forms an ester on the carboxyoxy groups (-C(O)-O-) of the muconic acid. The esterification agent can be any hydroxyl containing compound which reacts to form an ester under reaction conditions. Preferred esterification agents include hydrocarbon compounds having hydroxyl groups bonded thereto. More preferred esterifying agents include compounds corresponding to the formula R ¹ OH wherein R ¹ is a hydrocarbyl group, optionally containing a heteroatom containing functional group, wherein the hydrocarbyl group does not interfere in the formation of the cyclohexene compound. Preferred classes of esterifying agents include alkanols, aryl alcohols and aryl substituted alkanols. Preferred esterifying agents include alkanols, with C _1-10 alkanols being more preferred and methanol being most preferred. Among preferred aryl substituted alkanols is benzyl alcohol. Among preferred aryl alcohols are phenol and the various isomers of dihydroxy benzene. In another embodiment, the esterifying agent can be a polyglycol having one or more hydroxyl groups and one or more ether groups.

[0027] Muconic acid in one or more of its isomeric forms is contacted with one or more esterifying agents in the presence of one or more acids. The acids utilized can be any acids which facilitate the replacement of the hydroxyl group on the carboxylic acids with hydrocarbyloxy groups. Preferred acids are Bronsted acids. Bronsted acids are acids containing a protonic hydrogen that disassociates in solution. The acids are preferably strong acids. Strong acids as used herein mean acids with a pKa of lower than about 0. In a more preferred embodiment, the acids are strong mineral acids. Preferred strong mineral acids include sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, with sulfuric acid being most preferred. The acids are present in a sufficient amount to facilitate the esterification reaction. Where the esterification agent is in the liquid state no solvent is required. If the esterification agent is a solid or cannot function as a solvent, a solvent may be utilized. Preferred solvents are polar aprotic solvents as described hereinbefore which solubilize the muconic acid. More preferred solvents are cyclic and acyclic ethers, with cyclic ethers, such as tetrahydrofuran, more preferred. The esterification agent is preferably present in a sufficient amount to convert substantially all of the muconic acid to the carboxylate ester form. In a more preferred embodiment, the esterification agent is present in greater than an equivalent ratio based on the equivalents of muconic acid. Preferably, the esterification agent is present in a two to one molar ratio or greater as compared to the muconic acid. Where the esterification agent is also the solvent, the equivalent and molar ratios are much greater. The reaction can take place at any temperature wherein the esterification reaction proceeds at a reasonable rate. Preferably, the temperature is elevated. Elevated temperatures increase the amount of muconic acid which can be dissolved and contacted with the esterification agent. Preferably the temperature of the reaction is about 23°C or greater, more preferably about 50°C or greater and most preferably about 120°C or greater. Preferably the temperature of the reaction is about 200°C or less and most preferably about 150°C or less. The reaction time utilized is chosen to give the desired yield of product. The product recovered may be a monohydrocarbyl muconate, a dihydrocarbyl muconate or a mixture thereof, in a more preferred embodiment the product is substantially dihydrocarbyl muconate. More preferred dihydrocarbyl muconates include dialkyl muconates, more preferably a C _1-10 dialkyl muconates and most preferably dimethyl muconate. The hydrocarbyl groups can be substituted with substituents which do not interfere with the reaction of the dihydrocarbyl muconate with one of more dienophiles. The trans,trans muconate esters precipitate from the solution upon cooling. Preferably the reaction mixture is cooled to less than about 40°C to facilitate precipitation, and preferably to ambient (23°C) or less. The dihydrocarbyl muconate may be recovered by simple removal of the solvent or excess esterification agent, such as by decantation. Preferably, the yield of dihydrocarbyl muconate is about 70 percent by weight or greater based on the weight of the starting muconic acid. Preferably, dihydrocarbyl muconate recovered exhibits a purity of about 99 percent by weight or greater and most preferably about 99.5 percent by weight or greater. Preferably, the dihydrocarbyl muconate exhibits a detectable amount of ^l4 C and preferably of up to about one part per trillion. In a preferred embodiment, the recovered dihydrocarbyl muconate has about 6 carbon atoms or greater derived from renewable resources, such as biomass.

[0028] In another embodiment, muconic acid may be contacted with an esterifying agent in an aqueous base solution to form a dihydrocarbyl muconate. Preferably this reaction is performed at a temperature of from ambient to (about 23°C) to about 40°C. The base can be any base which binds the protons of the carboxyl groups of muconic acid. Preferably, the esterifying agents are present in an equivalent ratio of about 2:1 or greater. The upper limit on the equivalents is practicality. The dihydrocarbyl muconate is recovered by extraction into organic solvent and subsequent evaporation of the extracting organic solvent.

[0029] The one or more muconic acids or esters thereof can be converted to other forms of carboxylate derivative groups using reaction sequences known to those skilled in the art. As used herein the term carboxylate derivative refers to any group which contains a carbonyl group (C=0) or a nitrile group ( ^— C≡N ), wherein the carbonyl group is bonded to an anion so at to form a salt or to a heteroatom, such as oxygen, nitrogen, sulfur or one or more halogens. The heteroatom may be further bonded by a covalent bond to one or more other groups, such as hydrocarbyl groups which may optionally contain one or more heteroatoms, or may be electronically (electrostatically) bonded to a cation to form a salt. Preferably, the carboxylate derivative is an acyl halide, carboxylic acid, amide, ester, thiol ester, mercaptocarbonyl, an anhydride, a nitrile, a salt with an anion or a salt with a cation. Preferred cations include alkali metal ions and unsubsituted and hydrocarbyl substituted ammonium ions. Preferred carboxylate derivatives comprise carboxylic acids, acyl halides, amides, anhydrides and esters. More preferred carboxylate derivatives include carboxylic acids and esters, with esters most preferred. Preferred carboxylate derivative groups correspond to the formula

wherein R* is independently in each occurrence hydrogen, a hydrocarbyl group optionally containing one or more heteroatoms or a cation;

Z is independently in each occurrence an anion, oxygen, nitrogen, sulfur, a nitrile, or a halogen; and, b is independently in each occurrence 0, 1 or 2 with the proviso that b is 0 when Z is an anion, halogen or nitrile; 1 when Z is oxygen or sulfur and 2 when Z in nitrogen. R ¹ is preferably hydrogen or a C hydrocarbyl group which may contain one or more heteroatoms, more preferably hydrogen or a C,.| ₀ alkyl group which may contain one or more heteroatoms, more preferably hydrogen or a C _1-3 alkyl group and most preferably hydrogen or methyl.

Acyl halides (acid halides) preferably correspond to the formula

wherein X is a halogen. X is preferably chlorine or bromine, with chlorine most preferred.

Amides preferably correspond to the formula

wherein c is separately in each occurrence 0, 1 or 2, with 0 or 1 being preferred.

Esters preferably correspond to the formula

Mercaptocarbonyls preferably correspond to the formula

Thiol esters preferably correspond to the formula

Anhydrides preferably correspond to the formula

Nitriles preferably correspond to the formula: -C≡N . [0030] Carboxylate derivatives of muconic acid can be represented by the following formulas

wherein R ¹ is as defined herein before. In alternative embodiments, the dihydrocarbyl muconates, especially the trans,trans isomeric versions, can be prepared from muconic acid by any known synthetic sequence. For example the dihydrocarbyl muconates may be prepared by the processes disclosed in the following sections of Jerry March, Advanced Organic Chemistry. 2 ^nd Edition, Wiley, 1 77, at pages 361-367, incorporated herein by reference: section 0-22 alcoholysis of acyl halides, section 0-23 alcoholysis of anhydrides, and section 0- 24 esterification of acids. Amide based carboxylate derivatives may be prepared by processes known to those skilled in the art including those disclosed in March, ibid, in sections 0-S2 amination of alkanes, 0-53 formation of nitriles, 0-54 acylation of amines by acyl halides, and 0-55 acylation of amines by anhydrides at pages 381 to 384, incorporated herein by reference. Acyl halides may be prepared by processes known to those skilled in the art including those disclosed in March, ibid, section 0-75 formation of acyl halides from acids at page 398 incorporated herein by reference. Thiolesters of muconic acid may be prepared by processes known to those skilled in the art, including those disclosed in March, ibid, wherein muconic acid is converted to acyl halides as described above and then converted to a thiol or a thiol ester by the process disclosed in section 0-40 on pages 375 and 376, incorporated herein by reference. Muconic acids may be converted to di anhydride analogs by processes known to those skilled in the ait such as disclosed in March, ibid, section 0-29 acylation of acids with acyl halides and section 0-30 acylation of acids with acids, at pages 369 and 370 incorporated herein by reference. Muconic acids may be converted to nitriles by processes known to those skilled in the art such as disclosed in March, ibid, section 6-63 at pages 883 and 884 conversion of acid salts to nitriles.

[0031] One or more muconic acid or carboxylate derivatives thereof are reacted with one or more dienophiles to prepare a cyclohexene compound having carboxylate groups j _n th _e ] and 4 positions, and optionally in the 2 position. One or more muconic acids means that a mixture of isomers may be used. In one preferred embodiment the starting muconic acid or carboxylate thereof is in the trans,trans isomeric form. Preferably such carboxylates are in the trans,trans isomeric arrangement. In one embodiment, the cis,cis and/or cis.trans isomers of muconic acid or carboxylate derivatives thereof may be utilized as starting materials. In this embodiment, it is believed that the muconic acid or carboxylate derivatives thereof isomerize in situ before reacting with the dienophile. Carboxylate esters are preferred as starting materials in this reaction. The dienophile can be any compound having unsaturation which reacts with muconic acid or a carboxylate derivative thereof to form a cyclohexene compound. Preferred dienophiles correspond to the following formula

wherein

R ² is independently in each occurrence hydrogen, halogen, a hydrocarbyl group optionally containing one or more heteroatoms or heteroatom containing functional groups wherein the hydrocarbyl group does not interfere in the formation of the cyclohexene compound; and R ³ is independently in each occurrence hydrogen, halogen or a hydrocarbyl group optionally containing one or more heteroatoms or heteroatom containing functional groups wherein the hydrocarbyl group does not interfere in the formation of the cyclohexene compound; with the proviso that R ² and R ³ may be combined to form a cyclic ring which may contain heteroatoms. Preferred classes of dienophiles include alkenes, unsaturated cyclic compounds, alkynes, aromatic compounds having unsaturated substituents. and the like. Preferred alkenes useful as dienophiles include any straight or branched aliphatic compound containing at least one double bond wherein such compounds may contain heteroatoms or heteroatom containing functional groups which do not interfere in the formation of the compounds having 6 membered cyclic rings. Such heteroatoms include oxygen, nitrogen, phosphorous, sulfur and halogens. Preferred halogens include chlorine and bromine, with chlorine preferred. Preferred alkenes include unsaturated acids, carbonates containing unsaturation, unsaturated esters, unsaturated nitriles, vinyl chloride, vinyl acetate, unsaturated aliphatic hydrocarbons having one or more double bonds (including ethylene, propylene, all isomers of butene, pentene, hexane, heptene, octene), and the like. Alkenes useful herein can have unsaturation at any point of the carbon chain. Preferred alkenes are those having unsaturation at the terminal end of a chain, which is between the 1 and 2 carbon atoms. Among preferred unsaturated carbonates is vinylidene carbonate. Among unsaturated acids are any carboxylic acids having unsaturation in the backbone of the carbon chain including methacrylic and acrylic acids. Ethylene and propylene are more preferred unsaturated aliphatic hydrocarbons, and ethylene is most preferred. Preferred unsaturated cylic compounds include cyclopropene, cyclobutene, cyclopentene, cyclohexene which may optionally contain a heteroatom or be substituted with a heteroatom containing subsituent as described hereinbefore. Any unsaturated ester which reacts with muconic acid, or a carboxylate derivative thereof, may be used as a dienophile in this process. Preferred unsaturated acids or esters correspond to the formula

wherein R ³ is as described hereinbefore, and R ⁴ is independently in each occurrence hydrogen, a hydrocarbyi group optionally containing a heteroatom containing functional group. Preferred unsaturated esters include hydrocarbyi acrylates, hydrocarbyi alkylacrylates and the like. Preferably, the double bond is located on a terminal carbon. More preferred unsaturated esters include hydrocarbyi acrylates and hydrocarbyi alkylacrylates, such as methyl methacrylate, with the hydrocarbyi acrylates being more preferred. The unsaturated esters may contain heteroatoms or heteroatom containing functional groups which do not interfere in the formation of the compounds having 6 membered cyclic rings as described hereinbefore. Preferred hydrocarbyi acrylates include C io alkyl acrylates with methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate being more preferred. The aromatic compounds having unsaturated subsituents useful as dienophiles include any aromatic compound having an unsaturated subsituent which reacts with muconic acid or a carboxylate derivative thereof under the reaction conditions defined herein. Among preferred aromatic compounds containing unsaturated subsituents are styrene, alpha- methylsryrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ar-ethylstyrene, ar- vinylstyrene, ar-chlorostyrene or ar-bromostyrene, and the like. Preferably, the unsaturated aromatic compound corresponds to the formula

wherein

R ⁵ is independently in each occurrence a hydrocarbyi group optionally containing a heteroatom containing functional group or a halogen; and R ⁶ is an alkenyl group optionally containing a heteroatom containing functional group. Another preferred class of cyclic unsaturated compounds is cyclic unsaturated anhydrides. Among preferred cyclic anhydrides is maleic anhydride, and the like, with maleic anhydride preferred. The alkyne containing compounds useful as dienophiles include any compound containing a triple bond (— C=C— ) which reacts with muconic acid or a carboxylate derivative thereof under the reaction conditions. The triple bond can be located at any position in the carbon chain of the alkyne, and is preferably between two terminal carbon atoms. Preferably alkyne containing compounds include all isomers of C _2-n alkynes, acetylenecarboxylic acid and carboxyate derivatives thereof and acetylene dicarboxylic acid and carboxylate derivatives thereof. More preferable alkynes include acetylene, acetylenic esters, propyne, butyne and the like, with acetylenic esters being most preferred. Preferred alkynes correspond to the formula wherein R ² and R ³ are as described herein before.

Preferred acetylenic esters correspond to one of the formulas and more preferably wherein R ¹ , R ² , R ³ , Z and b are as described hereinbefore.

Preferred acetylenic esters comprise one or more carboxylate esters bonded directly to carbons of the triple bond.

[0032] Preferably the reactants are contacted at a temperature at which they are in liquid form so as to mix intimately or are in a solvent which dissolves the starting materials. Preferably, the reaction is performed neat, that is, in the absence of solvent. The one or more muconic acids, or carboxylate derivatives thereof, and one or more dienophiles are contacted at elevated temperatures. Any temperature at which the one or more muconic acids, or carboxylate derivatives thereof, and dienophiles are in the same phase and react at a reasonable rate may be used. Preferably, the temperature is about 100°C or greater, more preferably about 130°C or greater and more preferably about 140°C or greater. Preferably, the temperature is sufficiently high to permit the Diels Alder reaction to proceed at a useful rate, while avoiding thermal decomposition or unwanted side-reactions of the reactants. The reaction can take place neat, that is, in the absence of a solvent, or in the presence of a solvent. In those embodiments wherein a solvent is used, any solvent which facilitates the reaction and which does not interfere in the reaction may be used. Preferred solvents are hydrocarbons, acyclic ethers, alkyl polyethers, and cyclic ethers which can be used at the temperatures and pressures of the reaction, that are liquid at the reaction temperatures, that is, have a boiling point above the reaction temperature at the pressure used for the reaction. Among preferred solvents are xylene, decaline, toluene, cyclic ethers, glycol ethers and polyglycol ethers and the like. In the embodiment where trans,trans muconic acid is used as a starting material it is preferable to perform the reaction in water or in a solvent which does not transesterify the acid groups of the muconic acid to avoid side reactions and in which the muconic acid is soluble. The reaction is allowed to proceed until the desired yield of product is obtained. Optionally, and more preferably, the Diets Alder reaction may be performed using water as the solvent. In this case, it is preferred to use the diene in the form of the di- carboxylic acid. When using ethylene as the dienophile, the initial charge of ethylene may be between 100 psi and 4,000 psi, and is preferably between 2S0 psi and 1,250 psi, and more preferably between 750 and 1,000 psi. Reactions temperatures may be above the boiling point of water under standard conditions (i.e. 100°C) and may be between 100°C and 300°C, and preferably between 120°C and 250°C. In addition to the above optional reaction conditions, the reactants are reacted in the presence of a catalyst that is not incompatible with the solvent or reaction conditions of temperature or pressure or the like. The catalyst may be present in a sufficient amount to allow the reaction to preoceed at a useful rate. The catalyst may be homogeneous or heterogeneous and is preferably heterogeneous. The catalyst may be a Lewis acid. In a preferred embodiment, the reaction is carried out in the presence of the one or more compounds which inhibit the polymerization of unsaturated compounds. Any compound which prevents the polymerization of unsaturated compounds may be used in the reaction. Among preferred classes of compounds which prevent the polymerization of unsaturated compounds are hydroquinones, benzoquinones, phenothiazines and anisoles, mixtures thereof and the like. Among preferred compounds which prevent the polymerization of unsaturated compounds are benzoquinone, hydroquinone, ί-butyl benzoquinone, methyl ether of hydroquinone, catechol, alkylated catechols, butylated hydroxy ani soles and the like, with hydroquinone being more preferred. The compounds which inhibit the polymerization of unsaturated compounds are present in the reaction mixture in a sufficient amount to prevent polymerization. Preferably, compounds which inhibit the polymerization of unsaturated compounds are present in an amount of about 0.05 percent by weight or greater based on the weight of the muconic acid, or carboxylate derivative thereof, most preferably about 0.01 percent by weight or greater. Preferably, compounds which inhibit the polymerization of unsaturated compounds are present in an amount of about 10.0 percent by weight or less based on the weight of the one or more muconic acids or carboxylate dereivalive thereof, more preferably about 2.0 percent by weight or less and most preferably about 1.0 percent by weight or less. The ratio of the one or more muconic acids or carboxylate derivatives thereof to one or more dienophiles is selected to maximize the yield of the desired products. The upper limit of the mole ratio of dienophiles to muconic acid and carboxylate derivatives thereof is based on practicality and is preferably about 10.0: 1.0 or less. In those embodiments wherein a solvent is utilized, the concentration of the one or more muconic acids, or carboxylate derivatives thereof, in the solvent is preferably about 0.2 Molar (M) or greater, and most preferably about 0.5 M or greater. In those embodiments wherein a solvent is utilized, the concentration of one or more muconic acids or carboxylate derivatives thereof in the solvent is dictated by solubility of the muconic acid in the solvent. The concentration of dienophile in the solvent is chosen in accordance with the concentration of the one or more muconic acids or carboxylate derivatives thereof in the solvent and the desired mole ratios of dienophiles to muconic acids or carboxylate derivatives thereof as described hereinbefore. The concentration of dienophile in the solvent is preferably about 0.5 M or greater and most preferably about 1.0 M or greater. The upper limit of the concentration of dienophile in the solvent is practicality. Preferably the dienophile is also used as the solvent.

[0033] The cyclohexene compound may be recovered by any means which allows isolation of the cyclohexene compound in a manner wherein the cyclohexene compound is recovered in the desired purity and yields, where the reaction is performed neat, the cyclohexene compound may be recovered by distillation or contacting the mixture with a low polar solvent, such as an ether, in a manner such that the cyclohexene compound dissolves, filtering off the unreacted materials which do not dissolve and concentrating the solvent by evaporation to give relatively pure cyclohexene compound. Where a solvent is used, recovery is performed by distillation of the reaction mixture or by chromatographic separation. Preferably, the yield of cyclohexene compound is about 70 percent by weight or greater based on the weight of the starting muconic acidor dcarboxylate derivative thereof. Preferably, cyclohexene compound recovered exhibits a purity of about 90 percent by weight or greater and most preferably about 99 percent by weight or greater. Preferably the cyclohexene compound exhibits a detectable amount of ^l4 C and preferably up to about 1 part per trillion. In a preferred embodiment the recovered cyclohexene compound has about six or greater, preferably about eight or greater, of its carbon atoms derived from renewable resources such as biomass.

[0034] In the embodiment wherein the muconic acid or carboxylate derivatives thereof are in the cis,cis or cis.trans isomeric form, the reaction with dienophiles is preferably performed in solvent. Preferably, in this embodiment carboxylate esters of muconic acid are reacted with the dienophiles. In this embodiment the process can be performed in the presence of an isomerization catalyst and/or the presence of second catalyst such as a Lewis acid, as described herein.

[0035] In the embodiment wherein the starting dienophile is an alkene which is in the gaseous form at ambient pressure and temperature, the one or more muconic acids or carboxylate derivatives thereof are preferably dissolved in a solvent, as described hereinbefore, and the solution is contacted with the alkene gas. Where the alkenes are liquid under the reaction conditions, the one or more muconic acids or carboxylates thereof are preferably dissolved in a solvent or alkene in as high a concentration as possible, the concentration is limited by the solubility of the one or more muconic acids or carboxylate derivatives thereof. The process is performed at ambient or elevated pressures. Elevated pressures are preferred as this allows the use of a significant excess of alkene. When elevated pressures are utilized, it is preferred to utilize a closed system and elevate the pressure by adding the alkene up to the chosen reaction pressure. Preferably, after the reaction system, containing one or more muconic acids and/or carboxylate derivatives thereof in the solvent of choice, optionally in the presence of a catalyst, is closed, it is evacuated at normal pressure to remove air and refilled with the gaseous alkene. This evacuation/refilling cycle is preferably repeated several times. The reaction system is then filled up to the chosen gaseous alkene pressure and stirred for up to 30 minutes so as to saturate the solvent with the gaseous alkene. Then the reaction system closed and heated to the desired reaction temperature. Air or an inert gas may also be present in the system but this is not desirable because this lowers the reaction rate. The pressure chosen is limited by the equipment used in the reaction and the equipment used to deliver the alkene and any other gas present. Preferably, the pressure is about 14.7 psi (O. lOlMPa) or greater, more preferably 100 psi (0.689 MPa) or greater and most preferably about 250 psi (1.72 MPa) or greater. Preferably, the pressure is about 50,000 psi (345 MPa) or less, more preferably 15,000 psi ( 103 MPa) or less, even more preferably about 10,000 psi (68.9 MPa) and most preferably about 1,000 psi (6.89 MPa) or less. Where the alkene is a gas, the alkene is preferably introduced in a significant excess and the desired pressure to be used dictates the amount of the excess utilized. If the alkene is liquid it is preferred to use the alkene as the solvent provided the muconic acid or carboxylate derivatives thereof are soluble in the alkene at reaction temperatures. Preferably the resulting product is soluble in the liquid alkene where used as the solvent. The reaction rate is significantly impacted by the reaction temperature and the pressure of the alkene present where it is a gas. Thus the reaction temperature is chosen such that the reaction rate is reasonable. Preferably, the reaction temperature is about 100°C or greater, more preferably about 120°C or greater and most preferably about 150°C or greater. Preferably, the reaction temperature is less than that causing thermal decomposition or unwanted side-reactions. The reaction time is selected to allow preparation of the cyclohexene compounds in the desired yield. The cyclohexene compound may be recovered by removing the solvent by evaporation. Where the reaction is performed neat the resulting product is recoverd by distillation. Preferably, the yield of cyclohexene compound is about 90 percent by weight or greater based on the weight of the starting muconic acid or carboxylate derivatives thereof and more preferably about 95 percent by weight or greater. Preferably, cyclohexene compound recovered exhibits a purity of about 95 percent by weight or greater and most preferably about 99 percent by weight or greater. Preferably, the cyclohexene compound exhibits a detectable amount of ¹⁴ C and preferably up to about one part per trillion. In a preferred embodiment, the recovered cyclohexene compound has about six or greater, preferably about eight or greater, of its carbon atoms derived from renewable resources such as biomass. In one preferred embodiment, the alkene is derived from renewable resources, such as ethylene derived from ethanol. Processes for the preparation of alkenes from renewable resources are well known in the art. In such embodiments, the number of renewable carbon atoms in the final product is about 8 or greater.

[0036] In the embodiment wherein the alkene dienophiles are reacted with muconic acid in water as a solvent, the product undergoes partial tautomerization. The resulting product mix includes products with the double bond between the 1 and 2 carbons of the cyclohexene ring and products with a double bond between the 2 and 3 carbons of the cyclohexene ring. In the embodiment wherein muconic acid is the starting material and the solvent is an esterifying agent, such as an alkanol, the resulting cyclohexene product undergoes esterification.

[0037] In the embodiment wherein the one or more dienophiles includes one or more alkynes which are in the gaseous form, such as acetylene, the one or more dienophiles are dispersed or dissolved in one or more solvents, such as those used for the reaction of dienophiles with alkenes. The reaction can be performed at atmospheric pressure or at elevated pressures by providing the alkyne in sufficient amount to pressurize the reaction mixture. Alternatively the alkyne can be introduced in admixture with an inert gas. Any gas which is inert and which can carry the dienophiles can be used. Among preferred gases are air, nitrogen, argon, and the like. Where the alkyne is liquid, the alkyne may be used as the solvent or the one or more alkynes and dienophiles may be contacted in one or more solvents. Preferred solvents are non polar solvents which are liquid under reaction conditions. Preferred solvents are cyclic and acyclic ethers and hydrocarbon solvents, such as xylene or decalin. Preferably, the reaction is performed with an excess of the alkyne as the reaction medium. Preferably, the reaction is performed in a closed reactor under pressure. The pressure is chosen to provide an excess of the alkyne and to keep liquid alkynes in the liquid state under the reaction conditions, such as at elevated temperatures. Preferably, the alkyne is present in a molar excess. More preferably, the alkyne is present in a molar excess or about 3.0: 1.0 or greater and more preferably about 5.0:1.0 or greater. The upper limit on the excess of the alkyne is practicality and the ratio is preferably about 6.0: 1.0 or less. The temperature of the reaction is chosen such that the reaction rate is reasonable and to be below the decomposition temperature of the reactants and the products. Preferably, the temperature is about 130°C or greater, more preferably about 140°C or greater and most preferably about 150°C or greater. The resulting product has a six membered aromatic ring in the desired products. The products may be separated by column chromatography. Preferably, the yield of desired products is about 80 percent by weight or greater based on the weight of the starting muconic acid or carboxylate derivatives thereof and more preferably about 90 percent by weight or greater. Preferably, desired compounds recovered exhibit purity of about 90 percent by weight or greater and most preferably 99 percent by weight or greater. Preferably the desired product exhibits a detectable amount of l ⁴ C and preferably up to about one part per trillion. In a preferred embodiment, the recovered compound has about six or greater, preferably about 8 or greater, of its carbon atoms derived from renewable resources such as biomass.

[0038] In a preferred embodiment, the cyclohexene compounds prepared correspond to one the

wherein R ¹ , R ² ' R ³ , Z and b are as described herein before.

[0039] In a more preferred embodiment, the cyclohexene compounds prepared correspond to one of the formula

wherein R ¹ , R ² and R ³ are as described herein before. In the embodiment wherein the dienophile is an unsaturated ester the cyclohexene compound preferably corresponds to one of the formulas

wherein R ¹ , R ³ and R ⁴ are as described hereinbefore. In the embodiment, the wherein the starting dienophiles comprise maleic anhydride or an analog thereof the cyclohexene formed preferably corresponds to one of the formulas

wherein R ¹ is as described hereinbefore. In the embodiment, wherein the starting dienophile is an aromatic compound having an unsaturated substituent the cyclohexene formed preferably corresponds to one of the formulas

wherein R ¹ , R ³ and R ⁵ are as described hereinbefore. In the embodiment where the starting dienophile is an acetylenic ester the product is a trimellitate or a derivative thereof which corresponds to the formula

wherein R ¹ , R ² , R ³ , Z and b are as described hereinbefore.

[0040] Preferably R ¹ is independently in each occurrence hydrogen, or an alkyl, haloalkyl, aryl, haioaryl, alkylaryl, alkyloxy, or carboxyl group containing not more than 10 carbon atoms. Even more preferably, R ¹ is independently in each occurrence a C _1-10 alkyl group; and most preferably R ¹ is methyl. Preferably, R ² and R ³ are independently in each occurrence hydrogen, halogen, alkyl, alkaryl, aryl, carboxyoxy alkyl or may be combined to form a cyclic ring which may contain one or more hetero atoms. More preferably, R ² and/or R ³ are independently in each occurrence hydrogen, halogen, or an alkyl, haloalkyl, aryl, haioaryl, alkylaryl, alkyloxy, or carboxyl group containing not more than 10 carbon atoms. Even more preferably, R ² and R ³ are independently in each occurrence hydrogen, chloro, bromo, C _1-8 alkyl, phenyl, or carboxyoxy C _1-8 alkyl or may be combined to form a cylic anhydride. R ² is even more preferably hydrogen, chloro, methyl, ethyl or phenyl. Preferably, R* is independently in each occurrence a C _1-10 alkyl group. More preferably, R ⁴ is independently in each occurrence a C _1-8 alkyl group. Most preferably, R ⁴ is independently in each occurrence methyl, butyl or ethylhexyl. Preferably, R ^S is independently in each occurrence a hydrocarbyl group optionally containing a heteroatom containing functional group. More preferably, R ^S is independently in each occurrence a C _1-10 alkyl group. Preferably, a is independently in each occurrence 0 or 1, and most preferably a is 0. In one embodiment, R ² is independently in each occurrence halogen, an alkyl, haloalkyl, aryl, haloaryl, alkylaryl, alkyloxy, or carboxyl group containing not more than 10 carbon atoms and R ³ is hydrogen; even more preferably, R ² is independently in each occurrence chloro, bromo, C _1-8 alkyl, phenyl, or carboxyoxy C _1-8 alkyl and R ³ is hydrogen; and R ² is even more preferably chloro, methyl, ethyl or phenyl while R ³ is hydrogen. In some embodiments R ² and R ³ are both hydrogen.

[0041] To prepare compounds having at least one benzene ring having carboxylate groups at the 1 and 4, and optionally at the 2 position, such as substituted or unsubstituted terephthalic acid or carboxylate derivatives thereof (including trimellitic acid or carboxylate derivatives thereof), from the cyclohexene compounds prepared by the reaction of muconic acid and/or carboxylate derivatives thereof with dienophiles as described herein, the cyclohexene compounds are subjected to dehydrogenation, which can also be called oxidation or aromatization. In the dehydrogenation step, the cyclohexene compounds are contacted with one or more dehydrogenation catalysts. In one embodiment, the cylcohexene compound is contacted with an oxidant and one or more dehydrogenation catalysts, at elevated temperatures. In one preferred embodiment, the cyclohexene compound is contacted with the dehydrogenation catalyst in the absence of an oxidant. Preferably, an inert gas is passed through the reactor to carry away hydrogen gas generated in the dehydrogenation process. Oxidants as used herein refer to any compound that shifts the dehydrogenation equilibrium to the desired aromatic products by reacting with the hydrogen removed from the cyclohexene compound. Preferably the oxidation of the cyclohexene ring results in the formation of an aromatic ring. Among preferred oxidation agents are oxygen, monoclinic sulfur, nitric acid, peroxides, hypochlorites, persulfates, chloranial and dicyanodichlorobenzoquinone. Oxygen in the form of air is a preferred oxidant. The oxidation agent is present in stoichiometric or greater amounts, preferably greater than stoichiometric amounts. The excess is chosen so as to drive the rate of the reaction. In one preferred embodiment the reaction is performed in the presence of an oxidant that reacts with the hydrogen generated in the process. Oxidants that react with hydrogen include oxygen. The reactants can be contacted neat or in a solvent. Preferable solvents are aprotic solvents with hydrocarbons (including alkenes), ethers (such as tetrahydrofuran) and pyrolidones (such as N-methylpyrolidone). Where the solvents are alkenes the hydrogen generated during the process may react with the unsaturated groups of the alkenes. Preferably, the solvents are liquid under reaction conditions. The cyclohexene ring containing compound concentration in solvent is at a concentration below the concentration at which disproportionation occurs. Preferably, the cyclohexene ring containing compound concentration in solvent is about 3.0 M or less. Preferably, the cyclohexene ring containing compound concentration in solvent is about 0.05 M or greater and most preferably about 0.10 M or greater. In one embodiment the reaction is performed at atmospheric pressure (14.7 psi, 0.101 MPa). At atmospheric pressure, the reaction can be performed at reflux of the solvent, provided the solvent boils at acceptable temperatures. Alternatively, the reaction can be performed at elevated pressures. Preferably, the oxidation agents are present in a molar excess of greater than about 2.0:1.0. Preferably, the oxidation agents are present in a molar excess of about 8.0: 1.0 or less. Suitable temperatures are those at which hydrogen is abstracted from the cyclohexene compound to form double bonds in the ring of the cyclohexene containing compound. Preferably, the temperature is about 120°C or greater and more preferably about 130°C or greater. Preferably, the temperature is about 400°C or less, more preferably about 350°C or less and most preferably about 325 °C or less. If the reaction is performed at elevated pressures, the pressure is preferably about 14.7 (about 15) psi (0.101 MPa) or greater and more preferably about 100 psi (0.689 MPa) or greater. If the reaction is performed at elevated pressures, the pressure is preferably about 1,000 psi (6.89 MPa) or less, more preferably about 600 psi (4.14 MPa) or less and most preferably about 500 psi (3.45 MPa) or less. The reaction time is chosen to facilitate preparing the desired compounds in the desired yield. The catalyst can be any dehydrogenation catalyst which under the reaction conditions abstracts hydrogen from the cyclohexene ring to form an aromatic ring. Preferred dehydrogenation catalysts are based on metals, more preferably Group VIII metals. The metals can be present in pure form, as alloys, in the form of metal oxides or mixtures thereof. The catalysts can also contain modifiers to impact or enhance the catalytic effect or selectivity of the catalyst. Such modifiers are well known in the art. Preferred reaction modifiers are transition metals and compounds containing transition metals. Preferred metals upon which the catalysts are based are platinum, palladium and nickel, with palladium most preferred. The catalyst can be used in a homogeneous manner but is preferably a heterogeneous catalyst on a support. The catalysts can also be in the form of sponge metals which are known to those of skill in the art. The support can be any support useful for heterogeneous catalysts. Among preferred supports are aluminum oxides, spinels, zeolites, silica gels, titanium oxides, zirconium oxides and carbon. The most preferred supports are carbon supports. Preferably the carbon supports are activated carbon supports. The dehydrogenation reaction can be performed in a solvent, that is liquid and has useful solvating properties at the temperature and pressure of the dehydrogenation reaction. Where the reaction is performed in a solvent at reflux, oxygen, preferably in the form of air, may be bubbled through the refluxing solvent. The catalyst is present in a sufficient amount such that the reaction proceeds in a reasonably efficient manner to give the desired product in the desired yield. The catalyst is preferably present in an amount of about 0.01 mole percent or greater based on the amount of the cyclohexene containing compound, more preferably about 0.03 mole percent or greater and most preferably about 1 mole percent or greater. The catalyst is preferably present in an amount of about 10 mole percent or less based on cyclohexene ring containing compound, more preferably about S mole percent or less and most preferably about 3 mole percent or less. The product is recovered by any means known in the art which allows isolation of the desired product at the desired yields and purity. Preferred means of recovering the desired products include filtering the reaction medium to remove the catalyst, concentrating the product by evaporation and separating the products recovered by chromatographic separation, distillation, and/or recrystallization from a suitable solvent. Preferably, the yield of products is about 60 percent by weight or greater based on the weight of the starting cyclohexene compound and more preferably about 65 percent by weight or greater. Preferably, the products recovered exhibit a purity of about 90 percent by weight or greater and most preferably about 99 percent by weight or greater. Preferably, the products exhibit a detectable amount of ^l4 C, preferably up to about one part per trillion. In a preferred embodiment, the recovered products have greater than about 6 carbon atoms derived from renewable resources such as biomass and more preferably greater than about 8 carbon atoms derived from renewable resources such as biomass.

[0042] Preferably, the dehydrogenation is performed in a continuous flow mode. Generally the conditions discussed hereinbefore may be used for continuous flow mode dehydrogenation. In a continuous flow mode process a fluid mixture containing the cyclohexene compound having carboxylate groups at the 1 and 4, and optionally at the 2 position, is contacted with a catalyst by flowing the fluid mixture over and/or through a bed containing the dehydrogenation catalyst. In this embodiment the dehydrogenation is performed at a temperature at which reasonable rates occur. Preferably, the temperature is about 150°C or greater, more preferably about 200°C or greater and most preferably about 300°C or greater. Preferably, the temperature is about 600°C or less, more preferably about 400°C or less and most preferably about 350°C or less. Preferably the dehydrogenation is performed under the flow of an inert gas, preferably nitrogen. Preferably the catalyst is a heterogeneous catalyst and the reactants are flowed through a bed of catalyst. Any apparatus which allows contacting a fluid containing the cyclohexene compound having carboxylate groups at the 1 and 4, and optionally at the 2 position with a catalyst bed may be utilized. Examples of useful reactor systems include fixed bed, fluidized bed and multiple fixed bed tray reactors, and the like. Preferably the reactors allow the reaction environment to be superatmospheric as described hereinbefore. The flow rates, reactions temperatures and concentrations of the reactions impact the rate of reaction. The flow rates are dependent upon the type of reactor, the size, the concentration of reactants in solvent and the catalyst loading level. Once these parameters are defined the flow rate can be determined. The product stream can be recirculated to enhance the product yield.

[0043] The reaction of one or more of muconic acid and carboxylate derivatives thereof with one or more dienophiles and the dehydrogenation reaction step may be performed without recovery of the cyclohexene from the solvent after the first reaction step. Both reactions can be performed as described hereinbefore. In the embodiment wherein the reaction of one or more of muconic acid and carboxylate derivatives thereof with one or more dienophiles is performed in the presence of a catalyst, preferably the catalyst, is removed prior to dehydrogenation. The dehydrogenation catalyst is added to the reaction mixture containing the cyclohexene compound before the dehydrogenation step is initiated. In this embodiment the solvent comprises ethers, cyclic ethers ( tetrahydrofuran), polyethers, glycol ethers, polyglycol ethers, hydrocarbons (xylene), and the like. More preferred classes of solvents are glycol ethers, polyglycol ethers, cyclic ethers, polyethers and ethers. More preferred solvents are dimethyl glycol ether and xylene. The dehydrogenation catalyst may be added to the reaction at any temperature up to the desired reaction temperature.

[0044] In a preferred embodiment the product recovered corresponds to the formula

wherein R ¹ , R ² , Z and b are as described hereinbefore.

[0045] In a more preferred embodiment the product recovered corresponds to the formula

wherein R ¹ , R ² and R ³ are as described hereinbefore. In the embodiment wherein the starting dienophile is an unsaturated ester the product is a trimellitate preferably corresponding to the formula

wherein R ¹ , R ³ and R ⁴ are as described hereinbefore. In the embodiment wherein the starting dienophile is maleic anhydride the resulting product preferably corresponds to the formula

wherein R ¹ , R ³ and R ⁴ are as described hereinbefore. Wherein the starting dienophile used to make the cyclohexene was an aromatic compound with an unsaturated subsituent the product preferably corresponds to the formula

wherein R ¹ , R ³ and R ⁵ are as described hereinbefore.

[0046] The benzene, cyclohexene and cyclohexane compounds having carboxylic acid groups at the 1 and 4 positions and optionally the 2 position; can be esterified to add hydrocarbyl groups at the 1 and 4 positions and optionally the 2 position to form carboxylate groups at these positions. The esterification reaction can be performed by any esterification process known to those skilled in the art including the processes discloses at March, ibid, pages 363 to 365 and the processes disclosed hereinbefore. In one embodiment an esterifying agent, an alcohol as described hereinbefore, is contacted with the benzene, cyclohexene and cyclohexane compounds having carboxylic acid groups at the 1 and 4 positions and optionally the 2 position in the presence of a strong acid with removal of the water and ester formed or a significant excess alcohol. The acidic catalysts are described hereinbefore.

[0047] The benzene, cyclohexene and cyclohexane compounds having carboxylic acid or carboxylate groups at the 1 and 4 positions and optionally the 2 position; may have the acid or carboxylate groups converted to acide halide groups utilizing processes known to those skilled in the art. In one preferred embodiment the benzene, cyclohexene and cyclohexane compounds have carboxylic acid or ester groups at the 1 and 4 positions and optionally the 2 position. The processes for conversion of such compounds to acid halides are disclosed hereinbefore. In particular, amide based carboxylate derivatives may be prepared by processes known to those skilled in the art including those disclosed in March, ibid, in sections 0-75 formation of acid halides from acids at page 398, incorporated herein by reference. The resulting acid haldes of embodiment the benzene, cyclohexene and cyclohexane compounds are islustrated by the formulas provided hereinbefore wherein the

substituent is replaced with the substiuent of the formula wherein X is a halogen.

[0048] The compounds prepared in this invention can be used as monomers to prepare a variety of known polymers. Some of the compounds can be used as plasticizers for various polymeric systems. The phenyl substituted terephthalates may be used to prepare liquid crystal polymers as described in US Patent 4,391,966, relevant disclosure incorporated herein by reference. The benzene compounds having carboxylic acid groups at the 1 and 4, and optionally the 2, positions, preferably terephthalic acid or dimethyl terephthalates, can be reacted with alkylene glycols, such ethylene glycol or 1,4-butane diol, to prepare polyesters. Processes for preparing such polyesters are well known in the art. For instance, terephthalic acid can be reacted with ethylene glycol to prepare polyethylene terephalate as described in "Contemporary Polymer Chemistry" Second Edition, Harry R. Alcock, Frederick W. Lampe, 1990, Prentice-Hall at pages 27 and 28, incorporated herein by reference. In a preferred embodiment the polyesters can be prepared according to copending and commonly owned patent application United States Application Serial Number 12/816,701 filed June 16, 2010 titled "BIOBASED POLYESTERS" incorporated herein by reference. The benzene compounds having carboxylic acid groups at the 1 and 4, and optionally the 2, positions, preferably terephthalic acid or dimethyl terephthalates, can be reacted with diamines, such as hexane diamine, to prepare polyamides. Preferably, the polyamides of the invention may be prepared from benzene, cyclohexene and/or cyclohexane compounds having amide forming carboxylate groups at the 1 and 4 positions and optionally the 2 position, and one or more diamines utilizing processes known to those skilled in the art. Among preferred processes are those disclosed in Oka et al. US 6,846,868; Keske US 5,763,561; Nakamura US 6,291,633; Kosinski et al. US 5,665,854; Chen US 5,194,577; Akkapeddi et al. US 5,276,131; Riemann et al. US 5,218,082; Raum et al. US 3,627,736; Poppe et al. US4,617,342 and Buehler US 7,053,169, and Kirk-Othmer Encyclopedia of Chemical Technology, 3d Edition, 1982 John Wiley and Sons, inc., Volume 18, pp 353-357, all incorporated herein by reference. . In a preferred embodiment the polymides can be prepared according to copending and commonly owned patent application PCT Application tided "BIOBASED POLYAMIDES" based on US Provisional application serial number 61/423,380 filed Decemer 15, 2010, and incorporated herein by reference.

[0049] The novel compounds of the invention and those prepared by the novel processes of the invention are preferably derived from renewable resources. Compounds prepared from renewable resources exhibit a characteristic ¹³ C/ ¹² C ratio as described in US 7,531,593 Column 6 line 60 to column 8 line 42, incorporated herein by reference.

[0050] It is understood that the above description is intended to be illustrative and not restrictive. Many embodiments as well as many applications besides the examples provided will be apparent to those of skill in the art upon reading the above description. It is further intended that any combination of the features of different aspects or embodiments of the invention may be combined. The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the invention, its principles, and its practical application. Those skilled in the art may adapt and apply the invention in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present invention as set forth are not intended as being exhaustive or limiting of the invention. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. Other combinations are also possible as will be gleaned from the following claims, which are also hereby incorporated by reference into this written description. The omission in the following claims of any aspect of subject matter that is disclosed herein is not a disclaimer of such subject matter, nor should it be regarded that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

SPECIFIC EMBODIMENTS

[0051] Unless otherwise stated, all parts and percentages are by weight.

[0052] Example 1 - Purification of crude cis,cis Muconic Acid In two separate 125 ml Erlenmeyer flask, a suspension in each of crude cis,cis muconic acid (10.0 g each for a total of 20.0 g) in methanol (50 ml) is heated to reflux with a heat-gun. The hot suspension is filtered. Additional methanol (30 ml) is added to the residue. It is heated again to reflux and filtered through the same filter paper into the same round-bottom flask. All solid present on the filter paper is now moved back into the Erlenmeyer flask, additional methanol (30 ml) is added and the heating to reflux followed by filtering sequence is repeated. The combined methanol solution (110 ml) is allowed to cool to room temperature, then placed into an ice bath. After warming to room temperature overnight, the mother liquid is decanted to reveal a microcrystalline beige solid, which after drying under high vacuum weights 4.84 g. This exact sequence is now repeated with the second 10 g batch of cis,cis- muconic acid to obtain 4.23 g. The mother liquids from both recrystallizations are then combined and evaporated to dryness. A single recrystallization of the remaining residue from methanol (75 ml) yields an additional 2.82 g. In total, 11.89 g (59% mass recovery) of pure cis,cis muconic acid.

[0053] Examples 2 to 9 - Synthesis of trans,trans Muconic Acid from crude cis,cis or cis.trans Muconic Acid

[0054] Dried, purified cis,cis muconic acid (5.0 g, 35.2 mmol) is suspended in THF (44 ml, 0.8 M). Either pure water (1 , 5, 10, or 20 weight percent) or (NH ₄ ) ₂ SO ₄ (1, 5, 10, or 20 weight percent) is added. I ₂ (45 mg, 0.5 mol percent) is added and the mixture is heated to reflux for 4 hour. After cooling to room temperature, the precipitated trans,trans muconic acid is collected by filtration and dried. In the case of the (NH ₄ ) ₂ SO ₄ experiments, the mass of collected trans,trans muconic acid is corrected for the presence of (NH ₄ ) ₂ SO ₄ . A sample of the mother liquid is concentrated and all of the residue is dissolved in DMSO-d ₆ for Ή NMR analysis. Integration allowed an estimation of the composition of the mother liquid. The results are compiled in Table 1.

[0055] Example 10 - Synthesis of trans,trans Muconic Acid from cis,cis Muconic Acid A mixture containing purified cis,cis muconic acid (0.50 g), a catalytic amount of iodine (25 mg), and acetonitrile (35 ml) is heated to reflux for 36 hours. The reaction is performed in the presence of ambient light in the laboratory. The precipitated solid is filtered off from the still hot solution and washed with cold acetonitrile. After drying under high vacuum, 0.40 g (80% yield) of pure trans,trans muconic acid are present as a tan-colored powder. [0056] Example 1 1 - Synthesis of trans,trans Dimethyl Muconate from trans,trans Muconic Acid

Concentrated H ₂ SO ₄ (0.52 ml, 0.1 volume percent) is added to a stirred suspension of trans,trans muconic acid (60 g, 0.42 mol) in methanol (0.52 1, 0.8 M). The reaction mixture is stirred at reflux for 16 hours. This reaction transforms a low solubility solid into another low solubility solid. The density of crystalline trans,trans dimethyl muconate is higher than that of crystalline trans,trans muconic acid: trans,trans muconic acid is suspended throughout the stirring methanol reaction mixture whereas trans,trans dimethyl muconate remains accumulated on the bottom of the flask at all investigated stirring rates. After cooling to room temperature, the mother liquid is decanted and the precipitate is washed with methanol. To remove all traces of H ₂ SO ₄ , fresh methanol (200 ml) is introduced and the mixture is heated to reflux for 10 minutes. After cooling to room temperature, the mother liquid is again decanted and the precipitate is washed with methanol. Drying under high vacuum provides clean trans,trans dimethyl muconate (68 g, 0.40 mol, 95% yield).

[0057] Example 12 - Synthesis of trans,trans Dimethyl Muconate from cis,cis Dimethyl Muconate

A solution of cis,cis dimethyl muconate (0.60 g, 3.43 mmol) and a catalytic amount of iodine (30 mg, 3.3 mole percent) in acetonitrile (10 ml) is heated to reflux for 15 hours. The reaction is performed in the presence of ambient light in the laboratory. Removal of all solvent on a rotary evaporator followed by high vacuum, washing with 15 ml diethyl ether and hexane in a 3/2 volumetric ratio to remove all of the iodine, and drying under high vacuum yields an off- white crystalline solid (0.58 g, 3.41 mmol, 97% yield), which is identified as pure trans,trans dimethyl muconate.

[0058] Example 13 - Synthesis of trans,trans Dimethyl Muconate from cis.trans Dimethyl Muconate

A solution of cis.trans dimethyl muconate (0.60 g, 3.53 mmol) and a catalytic amount of iodine (43 mg, 4.8 mole percent) in acetonitrile (10 ml) is heated to reflux for 25 hours. The reaction is performed in the presence of ambient light in the laboratory. Removal of all solvent on a rotary evaporator is followed by applying a high vacuum, washing with 15 ml diethyl ether and hexane in a 3/2 volumetric ratio to remove all iodine, and drying under high vacuum yields an off-white crystalline solid (0.60 g, 3.53 mmol, 100% yield) which is identified as pure trans,trans dimethyl muconate.

[0059] Example 14 - Preparation of Trimethyl Trimellitate via Reaction between trans,trans Dimethyl Muconate and Methyl Acrylate

In a 5 ml pressure tube, a solution of trans,trans dimethyl muconate (1.0 g, 5.9 mmol) in methyl acrylate (2.5 ml, 29.4 mmol, 5 eq.) is heated to 160 °C for 19 hour. ^] H NMR analysis of the cooled reaction solution reveals that no unreacted trans,trans dimethyl muconate remains. Three substances are found to be present in near equal quantities. Repeated column - chromatography (Si35, SF25-40g, AnaLogix column with 13 percent ethyl acetate/hexane isocratic eluent) of the crude reaction mixture, and analysis of single fractions, allows the identification of the three distinct reaction products: trimethyl trimellitate (23%), arising by an oxidation of the initially formed diene product, dimethyl 2-(2-methoxy-2- oxoethylidene)cyclopenta-3,5-diene-1,3-dicarboxyIate (29%), arising from a cheletropic addition (end-on) of the alkyne to the diene followed by oxidation, and an E/Z mixture of methyl 3-(2-methoxy-2-oxoethylidene)cyclopenta-1,4-dienecarboxylate (27%), arising from an attack of the alkyne onto the β-carbon of the ene, followed by methanol elimination to form a cumulene which undergoes rearrangement under expulsion of CO. Similar experiments with cis,cis and cis.trans dimethyl muconate only produce the products derived from trans,trans dimethyl muconate due to initial isomerization to trans,trans dimethyl muconate followed by addition.

[0060] Example 15 - Diels-Alder Reaction between trans,trans Muconic Acid and Acrylic Acid

A stirred mixture of trans,trans muconic acid (1.0 g, 7.0 mmol) and acrylic acid (0.96 ml, 14.0 mmol, 2.0 eq.) in a 5 ml round-bottom flask equipped with a reflux condenser is heated to 140 °C for 3 hours. To achieve a larger amount of conversion, more acrylic acid is added over the course of the reaction ( 1.0 eq. at 2 hours). In order to facilitate the characterization of the product, the reaction mixture is esterified in methanol overnight. GC-MS analysis of the crude esterified product shows the presence of trimethyl cyclohex-S-ene-1,2 _t 4-tricarboxylate, thus confirming the formation of cyclohex-5-ene-1,2,4-tricarboxylic acid via reaction between trans,trans muconic acid and acrylic acid.

[0061] Example 16- Preparation of Trimethyl Cyclo-5-ene-1,2,4-tricarboxylate Trans.trans dimethyl muconate (1 g, 5.9 mmol), methyl acrylate (1.6 ml, 17.6 mmol, 3 eq) and hydroquinone (65 mg, 0.59 mmol, 0.1 eq) are mixed in m-xylene (30 ml). The reaction mixture is refluxed under nitrogen for 72 hours. The reaction mixture is then concentrated down to a clear colorless gel, which is purified by column chromatography using the Analogix BSR SimpliFlash system (hexanes/ethyl acetate, 8:2). A mixture of the two diastereomers of the desired product is isolated as a clear colorless and colorless oil with a 61% yield, 0.9g, 3.6 mmol.

Example 17 to 19- Preparation of dimethyl cyclohex-2-ene-1,4-dicarboxylate In a Parr pressure reactor, a rapidly stirred solution of trans,trans dimethyl muconate (2.58 g, 15.2 mmol) in m-xylene (120 ml) is heated under an ethylene atmosphere (260 psi at 23°C after the solution is saturated with ethylene) at a 150 °C set-point temperature (151 - 168°C observed) for 24 hours. Ή NMR analysis of the near-colorless cooled reaction solution revealed about 96 percent conversion to dimethyl cyclohex-2-ene-1,4-dicarboxylate. Removal of the solvent provided a white, cloudy oil. The precipitated traces of trans,trans dimethyl muconate are separated by taking up the oil in tert-butyl-methyl-ether and filtering it to provide, after removal of the solvent, an over 98% pure product (near-colorless oil). Another batch is purified by column chromatography (Si35, SF25-40g, AnaLogix column with 13 percent ethyl acetate/hexane isocratic eluent) to obtain an analytical sample. Diastereomers of dimethyl cyclohex-2-ene-1,4-dicarboxylate are detected by GC. The results are compiled in Table 2.

[0090] Table 2 shows the amount of dimethyl muconate, pressure (psi), c(M), solvent, set and reaction temperatures, reaction time in hours and the result of the reaction.

[0062] Examples 20 to 21 - Reaction Between Free trans,trans Muconic Acid and Ethylene In a Parr pressure reactor, a rapidly stirred (155 rpm) mixture of trans,trans muconic acid (2.10 g, 14.7 mmol) and water (120 ml) is heated under an ethylene atmosphere (270 psi at 23°C after the solution was saturated with ethylene) at a 150°C set-point temperature for 3 days. After opening the cooled Parr reactor, an orange solid is present on the ground of a yellow solution. The yellow solution is decanted and the orange solid is dried (paper towel) to provide 0.85 g (5.0 mmol, 34% yield). Ή NMR analysis identifies it to be the tautomerized Diels- Aider addition product. An additional quantity of the tautomerized product was present in the yellow solution. In addition, the yellow solution also contained a small quantity of the untautomerized initial Diels-Alder addition product and decomposed material. A subsequent reaction (Example 21) at 125°C for 1 day shows that at such lower temperature more (44%) untautomerized initial Diels-Alder addition product is present at the time the reaction is worked-up; in addition, 13% tautomerized product is present, 41% unreacted starting material was recovered, and only 2% decomposed material is present. The results of Examples 20 and 21 are shown in Table 2.

Table 2

[0063] Example 22 - Dimethyl 2-Phenyl-cyclohexene-1,4-dicarboxylate, Dimethyl Phenyl- terephthalate, and Dimethyl 2-Phenyl-cyclohexane-1,4-dicarboxylate

In a 75 ml sealed tube, a stirred suspension of trans,trans dimethyl muconate (10.0 g. 58.8 mmol), two equivalents of styrene (13.5 ml, 117.6 mmol), neutral A1 ₂ O ₃ (300 mg of Aldrich 199974, 3 mass percent), and tert-butyl catechol (25 mg, 0.2 mol percent) in diglyme (20 ml, 2.9 M) is heated to 150°C for 24 hours. After cooling to room temperature, the reaction mixture is filtered, transferred to a flask, and concentrated. The residue is redissolved in triglyme (0.5 M). Pd/Al ₂ O ₃ catalyst is added [636 mg (0.5 mol percent) of Johnson-Matthey 5 percent Pd/Al ₂ O ₃ # 12] at room temperature. The flask is equipped with a reflux condenser, fritted gas dispersion tube, and internal temperature probe. Under N ₂ flow (190 ml/min) and stirring (190 rpm) the mixture is heated to reflux for 63 hours whereby dimethyl phenyl- terephthalate is formed. Some dimethyl 2-phenyl-cyclohexane-1,4-dicarboxylate is also produced.

[0064] Examples 23 - One-Pot Isomerization and Diels-Alder followed by Esterification

In a Parr pressure reactor, a stirred suspension of cis,cis muconic acid (8.6 g, 60.6 mmol) and I ₂ ( 114 mg, 0.7 mol percent) in diglyme (diglycol methyl ether, 120 ml, 0.5 M) is heated under ethylene pressure (270 psi (1.86 MPa) at 23°C) to 200°C for 48 hours. All solvent is removed, and methanol (200 ml) and a catalytic amount of concentrated H ₂ SO ₄ (0.2 ml) are added. After reflux for 14 hours, the solution is analyzed by GC to quantify the amounts of dimethyl cyclohex-2-ene-1,4-dicarboxylate ( 13 - 19%) and dimethyl cyclohex-1-ene-1,4- dicarboxylate (74 - 76%) present. Removal of the solvent and distillation provides clean product.

[0065] Example 24 - Synthesis of Dimethyl Cyclohex-2-ene-1,4-dicarboxyIate from trans,trans Dimethyl Muconate - Larger Scale

In a Parr pressure reactor, a stirred suspension of trans,trans dimethyl muconate (40.8 g, 240 mmol) in diglyme (120 ml, 2.0 M) is heated under ethylene pressure (270 psi (1.86 MPa) at 23°C) to 165°C for 24 hours. Analysis of the reaction mixture by GC allows quantification of the products; dimethyl cyclohex-2-ene-1,4-dicarboxylate (75 percent) and dimethyl cyclohex- l-ene-1,4-dicarboxylate (1%) are present. Removal of the solvent and distillation provides clean product.

[0066] Example 25 - Preparation of Terephthalic Acid by Oxidation of the Reaction Products between trans,trans Muconic Acid and Ethylene

In a Parr pressure reactor, the product of example 50 (0.85 g, 5.0 mmol) is suspended in H ₂ O (120 ml, 0.04 M) and Pt/C (390 mg, 5 percent Pt/C, 2 mole percent Pt) powder is added. The reactor is pressurized with air (240 psi at 23°C after saturation of the liquid phase) and its contents heated to 150°C set-point temperature for 3 days under rapid stirring (155 rpm). After opening the cooled Parr reactor, a white solid, partly submerged under the aqueous Pt/C suspension, is present on the surface of the glass reaction vessel. The combined material is filtered and repeatedly washed using copious quantities of hot methanol to provide, after concentration to dryness, a near white solid (0.43 g). ¹ H NMR analysis shows the presence of 55% terephthalic acid, 40% trans-, and 5% cis-cyclohexane-1,4-dicarboxylic acid.

[0067] Example 26 - Preparation of Dimethyl Terephthalate - Oxidation with Air at Normal Pressure

Air is bubbled through a refluxing solution of dimethyl cyclohex-2-ene-1,4-dicarboxylate (0.25 g, 1.26 mmol) in acetic acid (20 ml) containing a catalytic amount of platinum on carbon powder (200 mg, 5 percent Pt/C, 10 mg Pt, 4 mole percent) for a period of 87 hours. Ή NMR analysis of the cooled reaction suspension reveals about 69% conversion to the desired oxidation product. Filtration and removal of the solvent provides a near-white solid (0.24 g). Purification by column chromatography (Si35, SF40-80g, AnaLogix column with 13% ethyl acetate/hexane isocratic eluent) provides an analytical sample of dimethyl terephthalate.

[0068] Example 27 - Reaction of trans,trans Dimethyl Muconate with Ethylene and Dehydrogenation in the Same Solvent

In a Parr reactor, a mixture of trans,trans dimethyl muconate (6.13 g, 36.0 mmol) and diglyme (120 ml, 0.30 M) is heated to 165°C for 24 hours under ethylene pressure (p _RT = 259 psi (1.79 MPa)). After cooling to room temperature, the weakly yellow, clear solution is diluted using diglyme to 200 ml in a volumetric flask, transferred into a round-bottom flask equipped with a magnetic stirring bar, and catalytic palladium on carbon (Pd/C) is added (356 mg of Johnson-Matthey 5% Pd/C # 6, 0.2 mole percent) at room temperature. The flask is equipped with a reflux condenser, fritted gas dispersion tube, and internal Temperature probe. Under N ₂ flow (190 ml/min) and stirring (190 rpm) the mixture is heated to reflux (T _{max, observed} = 169°C) while samples were taken at appropriate intervals (r = 0.0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0 h) to monitor the progress of the reactions occurring. Rapid (r < 1 h) disappearance of the dimethyl cyclohex-2-ene-1,4-dicarboxylate, delta-2, 2-ene is observed concurrent with some material undergoing tautomerization to its thermodynamicatly more stable isomer (dimethyl cyclohex-1-ene-l,4-dicarboxylate, delta- 1, 1-ene), while also the desired oxidation/dehydrogenation/aromatization product dimehyl terephthalate (DMT) and some reduced material (dimethyl cyclohexane-1,4-dicarboxylate CHa) are formed. After 8 hours reaction time, 77% DMT, 17% cyclohexane, and 5% tautomer are present. The graph of Figure 1 shows the concentration of materials at various time intervals.

[0069] Examples 28 and 29 - High Yield Synthesis of Dimethyl Cyclohexane- 1 , 4- Dicarboxylate

A solution of dimethyl cyclohex-2-ene-l,4-dicarboxylate and dimethyl cyclohex- 1-ene- 1,4- dicarboxylate is hydrogenated under balloon pressure at room temperature over Pd/C catalyst. If methylene chloride is used as the solvent, primarily the 2-ene tautomer is reduced, whereas most of the 1-ene tautomer remains unreacted. If ethanol is used as the solvent both tautomers are reduced.

[0070] Example 30 - Dimethyl 2-Phenyl-cyclohexene-1,4-Dicarboxylate, Dimethyl Phenyl- terephthalate, and Dimethyl 2-Phenyl -Cyclohexane- 1,4-Dicarboxylate

In a 75 ml sealed tube, a stirred suspension of trans,trans dimethyl muconate (10.0 g, 58.8 mmol), two equivalents of styrene (13.5 ml, 117.6 mmol), neutral Al ₂ O ₃ (300 mg of Aldrich 199974, 3 mass percent), and /erf-butyl catechol (25 mg, 0.2 mol percent) in diglyme (20 ml, 2.9 M) is heated to 150°C for 24 hours. After cooling to room temperature, the reaction mixture is Altered, transferred to a flask, and concentrated. The residue is redissolved in triglyme (0.5 M). Pd/Al ₂ O ₃ catalyst is added (636 mg (0.5 mol percent) of Johnson-Matthey 5 percent Pd/Al ₂ O ₃ # 12) at room temperature. The flask is equipped with a reflux condenser, fritted gas dispersion tube, and internal temperature probe. Under N ₂ flow (190 ml/min) and stirring (190 rpm) the mixture is heated to reflux for 63 hours whereby dimethyl phenyl- terephthalate is formed. Some dimethyl 2-phenyl-cyclohexane-1,4-dicarboxylate is also produced. [0071] Example 31 - Preparation of Trimethyl Trimellitate

Trimethyl cycIohex-5-ene-1,2,4-tricarboxylate (200 mg, 0.78 mmol) is mixed with 305 mg of 5 percent by weight platinum on a carbon support in m-xylene (30 ml). The reaction mixture is re fluxed with the reflux apparatus being open to air for 4 days. T e residual platinum on carbon is then filtered off and the filtrate is concentrated down to a clear colorless gel. The desired product is obtained with a 65% yield. The yield is determined by GC/MS using a dodecane as an internal standard.

[0072] Example 34 - Synthesis of Dimethyl Terephthalate (DMT) - Continuous Flow Reaction

In an Autoclave Engineers BTRS-Jr continuous flow reactor, a 0.2 M solution of dimethyl cyclohexene-1,4-dicarboxylate, containing both the 2-ene and 1-ene tautomer, is passed over hot Pd/Al ₂ O ₃ [2.5 g of 5 percent Pd/Al ₂ O ₃ (Johnson-Matthey # 13, uniform metal location, 20 microns mean particle size, 1.23 percent H ₂ O) in a 10 mi catalyst chamber] in an up-stream flow direction under N ₂ pressure. Selected reaction conditions are shown in the Table 3.

[0073] Example 35-38c/s.c/j-Muconic acid is reacted with ethylene in water in the manner described in Examples 20 and 21, with reaction conditions altered according to the parameters listed in Table 4. The results are also compiled in Table 4.