CATALYST PRIORITY CLAIM

[0000] This Application claims benefit of priority of U.S. Provisional Application No. 62/259,118, filed November 24, 2015, the contents of which is incorporated herein by reference.

FIELD OF INVENTION

[0001] The present disclosure relates to the preparation of oligomers from sugar-derived carboxylic acids and glycols. In particular, the invention involves preparing oligomers of 2,5-furan-dicarboxylic acid (FDCA) and glycols in an esterification-transesterification process.

BACKGROUND

[0002] The commercial production of organic chemicals, such as polymers and pharmaceutical compounds, has traditionally been derived from petro-chemical sources. In recent years, considerable effort has been directed to develop more efficacious ways of exploiting relatively abundant and inexpensive biomass as a feedstock in the fabrication of organic chemicals as interest in renewable and sustainable technologies has grown. In particular, researchers have turned toward bio-based sources of hydrocarbons such as sugars (i.e., sucrose, fructose, dextrose, etc.) from biomass as alternatives to fossil-based or petroleum-derived precursors. The conversion of sugars to value-added chemicals holds tremendous economic promise when one considers the downstream processing (e.g., purification) technologies. Efforts to convert sugars to furan derivatives more efficiently have developed some major routes for achieving sustainable energy supply and chemicals production. Scheme A illustrates an example of such processes.

Scheme A.

[0003] Scheme A exhibits a schematic representation of a process for converting biomass into furanic intermediates, 5-hydroxymethylfurfural (HMF), 2,5-furan-dicarboxylic acid (FDCA) and 2,5- dimethylfurandicarboxlate (FDME). These "green" building blocks have demonstrated versatility in an array polymer applications, such as potential molecular scaffolds for use in the production of renewably sourced plastics and chemicals. For instance, furan 2,5-dicarboxylic acid (FDCA) manifests a sui generis polytropicity that enables one to deploy the molecule as a core component for various renewable plasticizers and as a surrogate pre-polymer to terephthalic acid (TP A), among others, such as polymer subunits, plasticizers, lubricants, dispersants, emulsifiers, adhesives coatings, resins, humectants and surfactants.

[0004] Over the years, chemists have sought approaches for producing and manipulating FDCA, given the problems associated with handling FDCA, such as its poor solubility in common organic solvents. An encumbrance that arises when using FDCA in melt polymerizations, for example, is the tendency for the molecule to decompose when temperatures arise to greater than about 200°C, leading to poor product quality. Such challenges can be partially resolved by esterifying FDCA.

Esterification through autocatalysis has shown promise as a viable synthetic methodology, but typically necessitates high temperatures and protracted reaction times, which is associated with excessive cost of manufacture on the commercial scale. Bransted Acid catalysis enhances the esterification process, affording high substrate conversions and ester yields, but poses downstream processing issues of removal and recycle.

[0005] Alternatives for esterification of FDCA require its activation as a diacyl chloride, which enable high conversions to the diester but limits the process scope as being neither sustainable nor economical. The synthesis of an acyl chloride (i.e., COC1 moiety) entails treating an acid with a stoichiometric amount of thionyl chloride or oxalyl chloride, then converting it to an ester via alcohol additions. Safety concerns can arise when employing each of the chlorinating agents at an industrial scale, as the byproducts of acylation are SO2, CO and HC1 depending on the reactant used. A significant drawback for conversion of FDCA to the corresponding diacyl chloride is an inherent instability, which facilitates side product formation. Additionally, the diacyl chloride is sensitive to water and, if produced in copious amounts, would require special storage conditions.

[0006] In view of these disadvantages of the current technique, a need exists for an alternate method of esterifying FDCA that employs a simple and non-toxic process, and enables easy conversion of the esters to an array of unique industrial chemicals.

SUMMARY OF INVENTION

[0007] The present disclosure describes, in part, a method for converting furan-2,5 dicarboxylic acid (FDCA) into oligomers. In particular, the method involves: reacting FDCA with at least an alcohol or a mixture of different alcohols in the presence of a homogeneous water tolerant Lewis acid catalyst, specifically a metal triflate species, for a time and temperature sufficient to esterify the FDCA and produce an intermediate ester; removing any unreacted alcohol; contacting a glycol to the intermediate ester in the presence of the metal triflate catalyst for a time and temperature sufficient to trans-esterify the intermediate ester and form an oligomer. An advantageous feature of the method is that it can be performed as a one-pot esterification-transesterification operation using relatively small amounts (e.g., < 1.0 mol. % relative to starting amount of FDCA) of the metal triflate catalysts. [0008] In another aspect, the present disclosure also pertains to a material that encompasses oligomer molecules that can be produced according to the present method. An oligomer of FDCA and glycols has a general formula according to:

wherein R' is the carbon core of either a linear or cyclic glycol, and n is an integer > 1.

[0009] Additional features and advantages of the present synthesis method and material compounds will be disclosed in the following detailed description. It is understood that both the foregoing summary and the following detailed description and examples are merely representative of the invention, and are intended to provide an overview for understanding the invention as claimed.

BRIEF DESCRIPTION OF FIGURES

[0010] FIG. 1 shows an ultra-high performance liquid chromatography photodiode array (UPLC- PDA) spectrum of a product mixture generated by autocatalytic esterification FDCA (methanol) according to Comparative Example 1.

[0011] FIG. 2A shows a ¾ NMR (400 MHz, d ⁶ -DMSO) spectrum of product from Ga(OTf) ₃ catalyzed methyl esterification of FDCA to FDME.

[0012] FIG 2B shows ¾ NMR (400 MHz. d ⁶ -DMSO) spectra of FDCA starting material (upper chart) superimposed over the product from Ga(OTf)j catalyzed methyl esterification of FDCA (lower chart) to FDME.

[0013] FIG 3 A shows a ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectrum of the product from Ga(OTf) catalyzed methyl esterification of FDCA to FDME.

[0014] FIG 3B shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of FDCA starting material (upper chart) and the product from Ga(OTf)3 catalyzed methyl esterification (lower chart) to FDME.

[0015] FIG 4A shows superimposed ^L, C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Ga(OTf) ₃ catalysis (lower chart).

[0016] FIG 4B shows superimposed ¹ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart).

[0017] FIG 4C shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart). [0018] FIG 4D shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart).

[0019] FIG 5 A shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf) ₃ catalysis (lower chart).

[0020] FIG 5B shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of 1,3-PDO starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf) ₃ catalysis (lower chart)

[0021] FIG 5C shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf) ₃ catalysis (lower chart).

[0022] FIG 5D shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf) ₃ catalysis (lower chart).

[0023] FIG 6A shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isoidide oligomer from Ga(OTf) ₃ catalysis (lower chart).

[0024] FIG 6B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isoidide oligomer from Ga(OTf) ₃ catalysis (lower chart)

[0025] FIG 7A shows superimposed *H NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Hf(OTf) ₄ catalysis (lower chart)

[0026] FIG 7B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Hf(OTf) ₄ catalysis (lower chart).

[0027] FIG 7C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Hf(OTf) ₄ catalysis (lower chart).

[0028] FIG 7D shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Hf(OTf) ₄ catalysis (lower chart).

[0029] FIG 8A shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf) ₄ catalysis (lower chart)

[0030] FIG 8B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf) ₄ catalysis (lower chart). [0031] FIG 8C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf)4 catalysis (lower chart).

[0032] FIG 8D shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf) ₄ catalysis (lower chart).

[0033] FIG 9A shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf>4 catalysis (lower chart)

[0034] FIG 9B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of isosorbide starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf) ₄ catalysis (lower chart)

[0035] FIG 9C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf) ₄ catalysis (lower chart).

DETAILED DESCRIPTION OF INVENTION

Section I. Description

[0036] The present disclosure describes, in part, a highly efficient one-pot process for preparation of mono and diesters of furan-2,5-dicarboxylic acid (FDCA), and oligomers of FCDA and glycols. One- pot synthesis is a strategy to improve the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one reactor. The strategy avoids a lengthy separation process and purification of the intermediate chemical compounds, and saves time and resources while increasing chemical yield. "One-pot reactions where several reaction sequences are conducted in the same reaction flask are one of the methods that can be used in order to conduct synthesis in a greener fashion. The chemistry is greener due to the reduction of work-up procedures and purification steps required compared to a more stepwise approach. In reactions that require a catalyst it is possible to combine several catalytic processes in the same reaction vessel." "One-Pot Reactions: A Step Towards Greener Chemistry." CURRENT GREEN CHEMISTRY, 1(3): 216-226.

[0037] The nature of the present method is conducive for a one-pot process. Scheme 1 shows a general representation of the esterification and transesterification reactions according to the present method. First, FDCA contacts an alcohol in the presence of a homogeneous water tolerant Lewis acid catalyst to produce an ester (i.e., a mono-ester (minor product) and/or diester (major product)). The homogeneous water-tolerant Lewis acid catalyst is composed of a metal triflate (M-(OTf) _x ). Second, the ester intermediate is further transesterified with a glycol to form an oligomer of the FDCA and glycol, catalyzed by the integrated metal triflate. The transesterification can be performed with biomass derived glycols to produce novel oligomers, which potentially can be used in renewable surfactants and plasticizers. The synthesis is efficacious and affords quantitative yields of diesters and depending on reaction times allows one to achieve targeted oligomer molecular weight distributions (i.e., tunability).

R = alkyl, alkenyl, alkynyl, allyl, aryl minor

M = metal

x = 2, 3, 4

n > 2

[0038] According to embodiments, the process involves using homogeneous water-tolerant Lewis acid catalysts to engender both the esterification of FDCA and subsequent transesterification using biomass-derived branched and/or straight-chain glycols, such as ethylene glycol (EG), propylene glycols (PG), butane diols (BDO), propane diols (PDO), pentane diols (including isopentanediols), hexane diols (including isohexanediols), furan-2,5-dimethanol, cis/trans bis-2,5- hydroxymethyltetrahydrofuran (bHMTF), and isohexides (i.e., isosorbide, isomannide, isoidide).

[0039] Water-tolerant Lewis acids have received attention in facilitating many chemical transformations, and are reviewed thoroughly in Chem Rev, 2002, 3641-3666, the contents of which are incorporated herein by reference. Traditionally, Lewis acids favor conditions in which virtually no water moisture is present, as they can quickly hydrolyze and lose their catalytic function even in with minor or trace amounts of water. As used herein, the term "water-tolerant" refers to a characteristic of a metal ion of a particular catalyst to resist being hydrolyzed by water to a high degree. Metal trifluoromethanesulfonate (CF3SO3 ^" ), also commonly referred to as triflates (-OTf), possess this remarkable trait, (e.g., see, J. Am. Chem. Soc. 1998, 120, 8287-8288, the content of which is incorporated herein by reference).

[0040] The metals of the triflates have +2 to +4 oxidations states, with +3 being predominant. Efficacious metals may include, for example: lanthanum, cerium, praseodymium neodymium, samarium, europium, gadolinium, terbium, dysprodium, holmium, erbium, ytterbium, lutetium, gallium, scandium, bismuth, hafnium, mercury, iron, nickel, copper, zinc, thallium, tin, and indium. Certain favored metal triflates for the esterification-transesterification process include (in order of their relative activity): hafnium (IV), gallium (III), scandium (III), bismuth (III), indium (III), tin (II) and aluminum.

[0041] As distinguished from heterogeneous catalysts, which are immobilized usually on carbon or aluminum supports, homogeneous metal triflate catalysts are monophasic with the reagents and demonstrate different mechanisms of catalysis than supported metal catalyst species. A cost advantage of metal triflate catalysis over insoluble heterogeneous catalysts is that the homogeneous species does not require filtration after use, which is an extra unit operation that can be avoided.

[0042] The present one pot process is able to convert FDCA to the corresponding diesters in reasonably high molar yields of at least 60% or 65%. Typically, the molar yield ranges from about 70% or 75% to about 95% or 99%, or any combination of ranges therein (e.g., about 80% to about 90%, about 82% or 85% to about 92% or 97%), depending on the reaction conditions, and with the residue being the corresponding monoester. In particular examples, homogeneous metal triflate catalysts of hafnium, gallium, scandium, bismuth, and indium can produce complete conversions of FDCA to a furanic ester (e.g., 2,5-furandimethyl ester, FDME, when the alcohol is methanol) in quantitative amounts.

[0043] Furthermore, an additional advantage of the one-pot system employing a homogeneous water- tolerant catalyst is that one can generate a relatively clean product mixture containing minimal amounts of side products. In contrast for instance, in strong Bransted acid (e.g., HC1, H2SO4) catalyzed processes one would need to perform extensive downstream separation or purification processing to remove side products and the catalysts from the product before the product mixture could be used in synthesis of other or additional compounds. In conventional processes, one uses catalyst in amounts that can be up to about 50 mol.% relative to the starting amount of FDCA. At such amounts, downstream processing will require catalyst removal.

[0044] A feature of the present process is that one need not remove the metal triflate catalyst (e.g., hafnium or gallium) from the reaction vessel. The crude furanic ester mixture, still containing the catalyst after residual alcohol is removed, shows pronounced activity in driving the transesterification of furanic ester with various glycols to form novel oligomers. Advantageous attributes of the metal triflates lie not only in their effectiveness in spurring esterification but also making unnecessary catalyst extraction from the mixture when further executing, for example, polymerization or other later transformations. For instance, no additional catalyst is necessary for to facilitate

transesterification.

[0045] In comparison to conventional catalyst loadings, the product can tolerate a certain amount of organometallic compounds remaining in the product mixture but it is usually limited to a maximum of about 10-15 mol.% or 20 mol.%. In the present process the metal triflate catalysts can be used in relatively low loads of about 1 mol.% or less, such as in amounts in a range of about 0.5 mol.% to 0.8 mol.% or less, relative to the starting amount of FDCA. Typically, the catalysts amount ranges from about 0.01 mol.% to about 0.1 mol.%, desirably, about 0.05 to about 0.08 mol.%. This feature of the present reaction system enables one to let the catalyst remain in the product mixture after esterification without need for removal. This simplifies and can expedite further downstream transformation or workings of the esters.

[0046] The esterification and/or transesterification reactions can be conducted either in an inert atmosphere (e.g., nitrogen or argon) or in air without detrimental effect on either reaction. One can conduct the reaction in a stainless steel Parr vessel at a temperature in a range from about 130°C to about 250°C, typically about 150°C or 160°C to about 225°C or 235°C, more typically about 170°C to about 200°C (e.g., about 175°C or 180°C to about 190°C or 195°C). Both the esterification and transesterification can be performed within about 20 hours overall reaction time, typically within about 14 or 15 hours. More typically, the total reaction time ranges from about 6 or 8 hours to about 10 or 12 hours; particular durations can be about 7-9 hours or about 8-10 hours. The separate, individual esterification or transesterification reaction may take up to about 6 or 8 hours, typically about 3-5 hours, depending on scale and apparatus.

[0047] The alcohols used for esterification of FDCA can be selected from various species, including, alkyl, alkenyl, alkynyl, allyl, or aryl alcohols. Certain inexpensive and commonly used alcohol species, for example, may include, but are not limited to: methanol, ethanol, propanol, isopropanol, butanol, cyclohexanol. The glycols used in transesterification may include at least: ethylene glycol, propylene glycol, 1,3-propanediol (1,3-PDO), butane diols, pentane diols, hexane diols, furan-2,5- dimethanol, cis/trans bis-2,5-hydroxymethyltetrahydrofuran, and an isohexide (i.e., isosorbide, isomannide, isoidide).

Section II. Examples

[0048] In the following examples, we further illustrate the present method of preparing esters and oligomers from transesterification. To reiterate, in general, sugar-derived oliogmers can be prepared by a) catalytically esteriiying FDCA in the presence of an alcohol with a homogeneous water-tolerant Lewis acid catalyst by b) transesterifying an intermediate ester product with a glycol catalyzed by the existent water-tolerant Lewis acid catalyst retained in the intermediate ester mixture. For purpose of illustration the particular examples presented herein use methanol in the esterification, but as stated above the process is not necessarily limited to such as other kinds of alcohols are also applicable.

[0049] Comparative Example 1 shows a conventional technique involving autocatalysis of FDCA.

Experimental: A 300 cc 316 SS autoclave was charged with 10 g of furan-2,5-dicarboxylic acid (64.1 mmol), 130 g of CH ₃ OH. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psig) and then charged with N2 to 200 psig. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 6 hours, pressure read 483 psig. After this time, the reaction mixture was cooled to ~100°C, then quickly transferred to a 250 mL

Wheaton™ bottle. UPLC analysis indicated that -99% of FDCA had converted to approximately 70% FDME, 30% of the corresponding monomethyl ester. Figure 1 is the spectral validation using ultra-performance liquid chromatography photodiode array (UPLC -PDA). Large spikes at about 4.30 minutes and at 6.059 minutes, respectively, indicate formation of monoester and diesters, with some residual FDCA at about 2.75 minutes.

I. Esterification of FDCA with methanol, catalyzed by metal triflates

[0050] Example #1 :

According to an embodiment, esterification of FDCA to FDME was executed using

Ga(OTf>3, as showing:

FDCA FDME

[0051] Experimental: A 75 cc 316 SS Parr reactor was charged with 2 g of FDCA (12.8 mmol), 66 mg of gallium triflate (Ga(OTf>3, 0.0128 mol) and 35 g of methanol. The reactor was sealed, purged three times with 200 psi N ₂ , then pressurized to 200 psi with N ₂ . While stirring at 500 rpm, the mixture was heated to 175°C for 2h. After this time, the vessel was cooled to 50°C, degassed, transferred to a 250 cc Wheaton bottle and placed in a refrigerator for 15 min. When removed, a profusion of colorless needles was observed. A small sample was analyzed by ¾ NMR indicating that all the FDCA had converted to >95% FDME, with a minor amount of FMME.

[0052] Figures 2A, 2B, 3A, and 3B, present the NMR spectral validation of the generation of esters, with the predominant product comprising the diester. Fig. 2A shows a ^: H NMR (400 MHz, d ⁶ - DMSO) spectrum of product from Ga(OTf)3 catalyzed methyl esterification of FDCA to FDME. Fig. 2B shows ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of FDCA starting material (top chart) superimposed over the product from Ga(OTf)3 catalyzed methyl esterification of FDCA (lower chart) to FDME. Fig. 3A shows a ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectrum of the product from Ga(OTf) ₃ catalyzed methyl esterification of FDCA to FDME. Fig. 3B shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of FDCA starting material (upper chart) and the product from Ga(OTf)3 catalyzed methyl esterification (lower chart) to FDME. [0053] Example #2.

In an alternate embodiment, the esterification of FDCA to FDME can be performed using Hf(OTf)4, as illustrat

FDCA FDME

Experimental: A 75 cc 316 SS Parr reactor was charged with 2 g of FDCA (12.8 mmol), 99 mg of hafnium triflate (Hf(OTf)4, 0.0128 mol) and 35 g of methanol. The reactor was sealed, purged three times with 200 psi N2, then pressurized to 200 psi with N2. While stirring at 500 rpm, the mixture was heated to 175°C for 2h. After this time, the vessel was cooled to 50°C, degassed, transferred to a 250 cc Wheaton bottle and placed in a refrigerator for 15 min. When removed, a profusion of colorless needles was observed. A small sample was analyzed by ¾ NMR indicating that all the FDCA had converted to >95% FDME, with a minor amount of FMME.

II. FDME polymerizations with integrated (i.e., already present) metal triflate catalysts. [0054] Example #1 : Oligomerization of gallium triflate integrated FDME with ethylene glycol.

Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial gallium triflate from methyl esterification of FDCA and 35 mL of ethylene glycol. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N ₂ to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, then transferred to a 250 mL Wheaton™ bottle.

[0055] Using ¾ and ¹³ C NMR analyses we validated the product structures. Fig. 4A shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart). Fig. 4B shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart). FIG 4C shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart). FIG 4D shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Ga(OTf)3 catalysis (lower chart).

[0056] Example #2: Oligomerization of gallium triflate integrated FDME with 1,3 -propanediol.

Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial gallium triflate from methyl esterification of FDCA and 35 mL of 1,3- propanediol. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N ₂ to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, then transferred to a 250 mL Wheaton™ bottle.

[0057] Again we used ¾ and ¹³ C NMR analyses to validate the product structures. Fig. 5 A shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf)3 catalysis (lower chart). Fig. 5B shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of 1,3-PDO starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf)3 catalysis (lower chart). Fig. 5C shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf)3 catalysis (lower chart). Fig. 5D shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-l,3-PDO oligomer from Ga(OTf)3 catalysis (lower chart).

[0058] Example #3. Oligomerization of gallium triflate integrated FDME with isoidide.

[0059] Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial gallium triflate from methyl esterification of FDCA, 3 g of isoidide (19.2 mmol), and 35 g of toluene. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N ₂ to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, excess toluene removed under reduced pressure, and the residue then transferred to a 10 mL Wheaton™ bottle.

[0060] Structural validation using ¾ and ¹³ C NMR analyses are presented in Figure 6A and 6B. Fig. 6A shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isoidide oligomer from Ga(OTf)3 catalysis (lower chart). Fig. 6B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isoidide oligomer from Ga(OTf)3 catalysis (lower chart).

[0061] Example #4. Oligomerization of hafnium triflate integrated FDME with ethylene glycol.

Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial hafnium triflate from methyl esterification of FDCA and 35 mL of ethylene glycol. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N2 to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, then transferred to a 50 mL Wheaton™ bottle.

[0062] Figures 7A-7D present ¾ and ¹³ C NMR analyses that validate the structures of the product. Fig. 7A shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Hf(OTf)4 catalysis (lower chart). Fig. 7B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 7C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-EG oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 7D shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-EG oligomer from Hf(OTf>4 catalysis (lower chart).

[0063] Example #5. Oligomerization of hafnium triflate integrated FDME with 1,3-propanediol.

Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial hafnium triflate from methyl esterification of FDCA and 35 mL of 1,3- propanediol. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N ₂ to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, then transferred to a 250 mL Wheaton™ bottle.

[0064] Figures 8A-8D present structural validation of the products using ¾ and ¹³ C NMR analyses. Fig. 8A shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 8B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 8C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-l,3-PDO oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 8D shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aliphatic region of EG.

[0065] Example #6. Oligomerization of hafnium triflate integrated FDME with isosorbide.

Experimental: A 75 cc 316 SS autoclave was charged with 1 g of FDME (5.43 mmol) containing an unknown amount of vestigial hafnium triflate from methyl esterification of FDCA, 3 g of isosorbide (19.2 mmol), and 30 mL of toluene. After the vessel was secured to the reactor, the head space was purged with nitrogen (x3, 500 psi) and then charged with N ₂ to 200 psi. While overhead stirring at 500 rpm the vessel was heated to 175°C, at which temperature the reaction proceeded for 5 hours. After this time, the reaction mixture was cooled to room temperature, excess toluene removed under removed pressure, and oily residue transferred to a 10 mL Wheaton™ bottle. [0066] Figures 9A-9C present ¾ and ¹³ C NMR analyses that validate the product structures. Fig. 9A shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 9B shows superimposed ¾ NMR (400 MHz, d ⁶ -DMSO) spectra of the aliphatic region of isosorbide starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf>4 catalysis (lower chart). Fig. 9C shows superimposed ¹³ C NMR (100 MHz, d ⁶ -DMSO) spectra of the aromatic region of FDCA starting material (upper chart) and FCDA-isosorbide oligomer from Hf(OTf)4 catalysis (lower chart).

[0067] Although the present invention has been described generally and by way of examples, it is understood by those persons skilled in the art that the invention is not necessarily limited to the embodiments specifically disclosed, and that modifications and variations can be made without departing from the spirit and scope of the invention. Thus, unless changes otherwise depart from the scope of the invention as defined by the following claims, they should be construed as included herein.