The present invention belongs to the technical field of synthesis of amides, and more particularly to one pot manufacturing of amides. The present invention relates to a solvent free manufacturing of amides in a one-pot procedure. The products are formed in high yield and can be used in application areas such as components in paints, lacquers or polymer blends without further purification.

Background

Amidines and amides are among others useful components in coating formulations, as additives in thermoplastics and as components in flame retardants. Solvents and/or metal complex catalysts are frequently used in order to ensure safe and reliable manufacturing processes.

WO 17105449 Al describes methods of synthesis of amidines, amidine-metal complexes, thin metal films formed using amidine-metal complexes on semiconductor devices, and semiconductor devices and systems with thin metal films formed using amidine-metal complexes. The synthesis comprises solvents.

US 9988482 BB and EP 3131992 Bl disclose a catalyst containing at least one amidine or guanidine group, which is bound to a siloxane residue. At room temperature, the catalyst is liquid, odourless and suitable as a cross-linking catalyst for curable compositions, in particular for silane group-containing compositions. It is particularly good at accelerating the hardening of such compositions without impairing stability in storage, and displays little volatility but good compatibility. Lanthanum(lll)-trifiuoromethanesulfonate is used as metal complex catalyst in the synthesis of the catalyst containing an amidine group.

KR 790000508 Bl discloses a process for the manufacture of N, N'-disubstituted amidines with anti-inflammatory activity. An imino-compound is reacted with amines in organic solvent.

WO 2004/087124 discloses amidine compounds for treating schizophrenia. Manufacturing of such amidine compounds is feasible by condensation of amine with substituted formamide in a solvent. EP 2264012 Al discloses heteroarylamidines and their use in microorganisms control. A process for the preparation of the heteroarylamidines comprises the conversion of a heteroarylamine with either aminoacetal, amide or amine/orthoformate in solvent.

DE 1267467 discloses the preparation of cyclic amidines by a condensation reaction of dicarboxylic acid semi-amide with diamine in hydrocarbon solvent. The cyclic amidines are useful as fuel additives and biocides.

DE 2036181 discloses a method for the preparation of benzamidines wherein benziminochlorides are reacted with aromatic amines in an inert solvent.

DE 2256755 Al discloses a method for preparation of amidines by reacting silylated amides or lactams with ammonia or amines. Mercury, tin, zinc and titanium chloride are used as catalyst and toluene, xylene, chlorobenzene and anisole as solvent.

EP 0617054 Bl discloses amine functional polymers which are vinyl based terpolymers made up of randomly linked units with formamidine or formamidinium formate, formamide and either amine or ammonium formate as functional groups. The polymers are prepared by aqueous hydrolysis of poly(N-vinylformamide) at a temperature in the range of 90 °C to 175 °C, preferably in the presence of a minor amount of ammonia or volatile amine.

EP0919555A1 a process for preparing a bicyclic amidine by reacting a lactone and a diamine. Water formed during the elimination reaction is distilled from the reaction mixture together with a considerable excess of diamine, which acts as non-reacting solvent.

W00078725 Al provides a process for preparing amidines starting from carboxylic acid derivatives, in which the carboxylic acid containing moiety is attached to a sp ³ -, or sp ² - or sp- hybridized carbon atom. The sp ² -hybridized carbon atom, to which the carboxylic acid containing moiety is attached to may be part of an aromatic or heteroaromatic or olefinic system. The process comprises use of solvent and purification of intermediates.

EP2260078 Bl, WO 2006045713, EP 1740643 Bl, EP 1756202 Bl, EP 1943293 Bl and EP 3341339 Bl disclose methods for preparing polymers comprising siloxane. The methods comprise conversion of amine bound to hydrolysed siloxane with carboxylic acid derivates. Considerable amounts of solvent are used for lowering viscosity and removal of water or alcohol from elimination reactions. EP 1943293 Bl claims a hybrid polymer which is suitable as UV absorber. The disclosed data for the preparation of the UV-absorber shows that the product is a mixture of solvent, hybrid polymer with claimed amide structure and hybrid polymer with claimed amidine structure.

None of the prior art discloses methods for the preparation of amides from amidines without using solvents and/or metal complex catalysts. Products manufactured by these methods require frequently purification from solvents and catalyst residue. Stripping and recrystallization may be applied. Apart from its negative environmental impact such purification is time consuming and costly. Hence, the useful industrial application of such products is frequently impaired. There are many different methods to prepare amides from amines and carboxylic acids or carboxylic acid derivatives by using catalysts, azeotropic distillation, and water binding means. There is still a need for methods for manufacturing of amides from amidines without using solvents and/or metal complex catalysts.

Objects

It is therefore an object of the present invention to provide a method for preparation of amides from amidines, in which neither the use of solvent nor the use of metal complex catalyst is mandatory. It is a further object to provide amides, which essentially are free of solvent residues and metal complex catalyst residues without a need of post-reactor purification.

The present invention

The above mentioned objects are achieved by a method as defined in claim 1.

According to another aspect, the present invention concerns amide as defined by claim 11.

Yet another aspect the present invention concerns use of the products as defined by claim 14. Preferred embodiments of the different aspects of the invention are disclosed by the dependent claims.

The present invention concerns the preparation of two amides from one amidine in a one-pot conversion. Neither the use of solvent nor the use of metal complex catalyst is mandatory. Amidines of formula (4a) or formula (4b) are used as starting materials. They may be prepared in a one-pot conversion without using solvents or metal complex catalysts.

(4b).

R ₁ , R ₂ and R4 independently from each other are selected from a group consisting of C ₁ -C ₃₀ alkyl, C ₅ -C ₃₀ aryl, C ₆ -C ₃₀ alkylated aryl and optionally interrupted by heteroatoms selected from the group consisting of 0, S and NH and optionally bound to one or more functional groups of formula (5)

R ₅ -R ₇ are chosen among C ₁ -C ₈ alkoxy, C ₁ -C ₃₀ alkyl, C ₅ -C ₃₀ aryl and C ₆ -C ₃₀ alkylated aryl,

R ₃ is H, C ₁ -C ₃₀ alkyl, C ₅ -C ₃₀ aryl, C ₆ -C ₃₀ alkylated aryl where two of R ₁ , R ₂ and R4 may be covalently be bound to each other and form ring structures. The amidines of formula (4a) or formula (4b) are converted with a carboxylic acid of formula (10)

R-COOH (10).

R is selected from a group consisting of H, C ₁ -C ₃₀ alkyl, C ₅ -C ₃₀ aryl, C ₆ -C ₃₀ alkylated aryl and optionally interrupted by heteroatoms selected from the group consisting of 0, S and NH. Formula (14a) and formula (14b) show the corresponding amides which are formed by the conversion of amidines of formula (4a) and formula (4b) with a carboxylic acid R-COOH (formula (10)).

A mechanism is shown below. Solvent free prepared amidine is converted with a carboxylic acid in order to obtain two amides per amidine group.

Conversion of methyl salicylate with ethylene diamine to a salicylamidine. Water and methanol are distilled off.

Conversion of the salicylamidine with propionic acid to an intermediate

The final diamide as product of the conversion of the salicylamidine with propionic acid

Two of the residues R ₁ , R ₂ or R4 connected to the amidine are covalently bound to each other and form a 5-membered ring. Thus, the two amide groups formed by the conversion above are covalently bound to each other, too.

Amidine prepared from siloxane functionalised monoamine and hydroxybenzoic acid and its conversion with fatty acid is shown below.

Conversion of amidine with fatty acid

To separate amides, which are not connected with a covalent bond are formed. Both amides are covalently bound to an hydrolysable silane. After the amidine formation step and at the end of the conversion shown above, the hydrolysis of the hydrolysable silane may still be negligible. Water formed during the amidine formation step is frequently evaporated too fast and a hydrolysis of the hydrolysable silane does rarely occur. In fact the fatty acid in the conversion shown above preferably reacts with the Si-OEt group instead of with the amidine group. Provided that no water is present in the reaction mixture a Si-OC(O)R and ethanol are formed and no conversion of the amidine group would happen. However small amounts of water, which are present under normal industrial conditions regenerate the fatty acid by hydrolysis and the amidine group can be converted to amides. The conversion depicted above is therefore not comprehensive, since the presence or addition of water is pre-assumed.

At the end of the conversion shown above, the hydrolysis of the hydrolysable silane may be at least partially performed by addition of a substance selected from the group consisting of water, water containing substances and water forming substances. Water containing substances may be selected from non-dried clay or water comprising metal salts, metal oxides, hydroxides or chlorides. Substances forming water may be selected from acids, alcohols, sugars or hydroxyl acids capable of intramolecular and/or intermolecular condensation reactions.

At least two amidine groups may be covalently bound together as amidine dimer, trimer, tetramer, oligomer or polymer. Examples are amidines, which can be polymerized by known means such as siloxane cross-linking or other types of cross-linking, which do not interfere with the presence of amidine groups. Amidine dimer, trimer, tetramer, oligomer or polymer can be converted with carboxylic acid R-COOH. Use of carboxylic acid R-COOH in a stoichiometric deficit related to the total amount of amidines will lead to a hydrogen bonding network comprising amides and amidines. Of special interest are such hydrogen bonding networks when R and/or R ₁ - R4 comprise hydroxyaromatic groups, which will form an extended hydrogen bonding network including the hydroxyaromatic groups. Hydrogen bonding networks provide essential and demanded properties in polymer coatings and polymer blends such as barrier properties and recyclability.

The carboxylic acid R-COOH may be provided by partial oxidative degradation or hydrolytic degradation of a polymer selected from the group consisting of polyethylene, polypropylene, polyamide, polyester, cellulose and lignin. Oxidative degradation frequently leads to chain scission in polyolefins such as polyethylene and polypropylene. Oxidized carbon end-groups of cleaved polymer chains may comprise -COOH groups, which are suitable as carboxylic acid reactants according to the present invention. Similar is true for other polymers such as polyamides, polyesters, cellulose and lignin. Lignin is a naturally occurring polymer made by crosslinking of phenolic precursors. Oxidation, optionally combined with hydrolysis yields polymer material with -COOH groups, which are suitable as carboxylic acid reactants according to the present invention. Polyamides and polyesters are able to form -COOH groups when submitted to hydrolytic degradation conditions.

Amides prepared according to the present invention have preferably a molecular weight of at least 1000 g/mole, more preferred at least 1500 g/mole and most preferred at least 2000 g/mole. Their role and use in polymer coatings and polymer blends is highly appreciated at these molecular weights due to easy handling and processing. Amide according to the present invention may be represented by the dimer of formula (9a) or the polymer of (9b) wherein n is an integer of 8-200, R ¹ -R ⁵ is H or OH, R ⁶ is C ₁ -C ₃₀ alkyl, C ₅ -C ₃₀ aryl, C ₆ -C ₃₀ alkylated aryl and optionally interrupted by heteroatoms chosen among the group of 0, S and NH. Amide as manufactured according to the present invention may in bulk form intermolecular hydrogen bonds. The influence of hydrogen bonds on crystallisation behaviour is known from block copolymers such as polyurethaneurea (PUU) block copolymers. PUU block copolymers are made up of soft segments based on polyether or polyester and hard segments based on the reaction of diisocyanate and diamine extender. They can be divided into polyether- and polyester-based PUU depending on the soft segments used. Polyester-based PUU have stronger hydrogen bonds between hard and soft segments for phase mixing than polyether-based PUU.

The hydrogen bonds cause an increased cohesion between the hard and soft segments with increasing hard segment contents, and higher hard-soft segment mixing present in these systems may also prevent the crystallization of the soft segments (Hydrogen bonding and crystallization behaviour: Xiu Yuying et al. POLYMER, 1992, Volume 33, Number 6).

Intermolecular hydrogen bonds between amides may have a major influence on the crystallisation behaviour of these amidines or amides. The amorphous parts in amides will increase. Amorphous domains in the solidified amides are likely to withhold solvent residues and metal complex catalysts. As a result, a post-reactor purification by recrystallization or stripping might be impaired. It is therefore a considerable advantage of the present invention to provide a safe and convenient high yield method for the preparation of solvent free and metal complex catalyst free amides from amidines.

It is expected that the influence of hydrogen bonds increases with increasing molecular weight of the amidine or amide. In a ninth embodiment the molecular weight of the amidine or amide is preferably at least 1000 g/mole, more preferred at least 1500 g/mole and most preferred at least 2000 g/mole.

Examples to support the patent claims

Example 1:

Preparation of salicylamidine from methyl salicylate and ethylene diamine. Water and methanol are distilled off Salicylamidine has strong intramolecular hydrogen bonds between the phenolic HO-group and the amidine group. The molecular structure is about plane and easily crystallizing due to the intramolecular hydrogen bonds.

2 moles of diethylene amine (is introduced in a 1000 ml 3-necked reaction flask and mixed with 2 moles of methyl salicylate. A clear solution is obtained at room temperature. The mixture is heated to 180 °C under stirring and about 100 g of distillate is collected. A clear slightly yellow and product is obtained. Melting range is 200 °C - 205 °C.

Example 2:

Preparation of N-(2-N'-propylamidoethyl)salicylic amide from salicylamidine and propionic acid.

N-(2-N'-propylamidoethyl)salicylic amide has strong intermolecular hydrogen bonds between the phenolic HO-group and the amide groups. 2 moles of freshly prepared salicylamidine are at around 150 °C and prior to its crystallization mixed with 2 moles of propionic acid. After initial turbidity, a clear, slightly yellow product is obtained after heating to 190 °C under stirring. No distillate of propionic acid (boiling point

141 °C) is collected. Melting range is 85 °C - 88 °C. N-(2-N'-propylamidoethyl)salicylic amide is not easily crystallizing due to the intermolecular hydrogen bonds. However wires of 100-500 pm diameter and several tenths of centimetre can be easily drawn. This is a strong indication for the presence of intermolecular hydrogen bonds.

Example 3: The reactions in example 1 and example 2 have been characterized by measurement of pH values. 0.1 moles of each mixture of starting materials and each product have been dispersed or dissolved in 100 ml of water by high shear mixing. The obtained dispersions or solutions have been directly measured with a calibrated pH electrode. Table 1 shows the measured pH values and an explanation for the measured pH values on the base of the expected chemical structures of starting materials and products.

Table 1: pH values and explanation pH measurement clearly indicates an about quantitative conversion from amine to amidine and finally to amide.

1H-NMR, 13C-NMR and FT-IR data have been evaluated as a support for the obtained amidines.

However hydrogen bonds and along with them sample concentration, pH-value, necessary solvents for sample preparation and temperature have a considerable influence on peak shape and position. Data from routine measurements are therefore no reliable proof or dis-proof of the formation of amidines. Reliable 1H-NMR, 13C-NMR and FT-IR data have to be based on a comprehensive scientific work on sample preparation, sample measuring and interpretation of spectra. This would exceed the scope of examples in a patent application. However such work is very welcome and will surely give valuable insights and probably contribute to new inventions.

Example 4:

Preparation amidines from an amine, which is covalently bound to hydrolysable silane and 4- hydroxybenzoic acid methyl ester

2 moles of 3-aminopropyltriethoxysilane are introduced in a 1000 ml 3-necked reaction flask and heated to 80 °C under stirring. 1 mole of 4-hydroxymethyl benzoate is added as powder within 5- 10 minutes. Heating is increased and the reaction mixture becomes clear at 120 °C. The reaction mixture is slowly heated to 180 °C and about 50 g of distillate is collected. A clear colourless and slightly viscous amidine is obtained.

After cooling to 60 °C 3 moles of H2O are added under vigorous stirring within 10-20 minutes. A clear product with reduced viscosity is obtained.

0.5 mole oleic acid are added and the mixture with initial turbidity becomes clear upon heating to 180 °C. A polymeric amide is formed with alternating groups of 4-hydroxybenzoic amid and oleic amide on a propylenesiloxane core.

The product is insoluble in water. However, after deprotonation of 40 molepercentage of the hydroxyl groups with NaOH a homogenous easy flowing mixture with water is obtained. The pH value of the mixture is 10.0. The dry content of the mixture measured as loss on dry at 120 °C is 60% w/w.

Example 5:

Preparation amidines from an amine, which is covalently bound to hydrolysable silane and methyl salicylate

1 mole of N-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane is introduced in a 1000 ml 3-necked reaction flask and heated to 80 °C under stirring. 1 mole of methyl salicylate is added within 5-10 minutes. Heating is increased and the reaction mixture becomes clear at 120 °C. The reaction mixture is slowly heated to 180 °C and about 50 g of distillate is collected. A clear colourless and slightly viscous amidine is obtained.

After cooling to 60 °C 3 moles of H ₂ O are added under vigorous stirring within 10-20 minutes. A clear product with reduced viscosity is obtained.

0.5 mole oleic acid are added and the mixture with initial turbidity becomes clear upon heating to 180 °C. A polymeric amide is formed with alternating groups of 2-hydroxybenzoic amid and oleic amide on a propylenesiloxane core.

The product is insoluble in water. However, after deprotonation of 40 mole% of the hydroxyl groups with NaOH a homogenous easy flowing mixture with water is obtained. The pH value of the mixture is 9.6. The dry content of the mixture measured as loss on dry at 120 °C is 58% w/w.

Example 6

Burning test of cardboard

Packaging type cardboard (ca. 300 g/m ² ) has been coated with amidines obtained in Example 4 and 5 (Amidine Ex4, Ex5) and the corresponding amides (Amide Ex4, Ex5) and subjected to flame testing. The cardboard samples are about 8 cm in width and 20 cm in length. They are coated by brushing two times on the front side, which is exposed to the flame and one time on the backside. Drying has been performed for 10 min in an air stream at 80°C.

Flame: butane lighter with about 20 mm flame, top of flame in contact with cardboard sample for 60 seconds.

Table 2: Weight of burning test samples before and after fire test

A clear difference between the uncoated reference and the amidine coated samples has been found. The amidine-coated samples were self-extinguishing within 5 seconds after removal of the butane flame and showed a maximum flame height of 5 cm. The amidine-coated samples are suitable as flame retardant coatings. The amide-coated samples do not show a significant flame retardancy compared to the uncoated cardboard. The burning test results indicate a more or less quantitative conversion of amidine to amide. Example 7

Preparation of amidines from an amine, which is covalently bound to hydrolysable silane and methyl salicylate in the presence of clay

1 mole of N-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane is introduced in a 1000 ml 3-necked reaction flask and heated to 80 °C under stirring. 10 g of clay (montmorillonite K-10, Aldrich) is added. Thereafter 1 mole of methyl salicylate is added within 5-10 minutes. Heating is increased and the reaction mixture becomes clear at 120 °C. The reaction mixture is slowly heated to 180 °C and about 50 g of distillate is collected. A transparent and slightly viscous amidine is obtained.

Example 8

Preparation of amidines and amides with methyl 4-hydroxybenzoate as carboxylic acid derivative

Two amidines and two amides thereof have been prepared similar to the procedures in example

1 and example 2. Starting materials, melting range and observations are shown in table 3.

Table 3:

The use of methyl 4-hydroxybenzoate provides products in which intramolecular hydrogen bonds are not possible. This is in contrast to the use of methyl 2-hydroxybenzoate (methyl salicylate) in example 1 where intramolecular hydrogen bonds dominate in the product. The absence of intramolecular hydrogen bonds leads in this case to the stronger presence of intermolecular hydrogen bonds. The melting behaviour and feasibility of drawing wires from molten product can be explained by the presence of intermolecular hydrogen bonds. The extreme temperature stability of example 8c in combination with a melting range comparable to thermoplastic resins reflects the presence of intramolecular hydrogen bonds, too.