Process for producing 1-hydroxythienoimidazole carboxylic acid and thienoimidazole carboxylic acid

Abstract: A process for producing 1-hydroxythienoimidazole carboxylic acid represented by formula (2): wherein R 1 and R 2 are as defined in the specification; wherein said process comprises the steps of: (a) reacting thienoimidazole represented by formula (1) with 1,4-dihalogenodimagnesium butane, in the presence of tetrahydrofuran or a mixed solvent comprising tetrahydrofuran and an aromatic solvent to produce a reaction mixture: wherein R 1 and R 2 are as defined above; (b) adding the reaction mixture obtained in said step (a) and, optionally, carbon dioxide, to: (i) a solution comprising carbon dioxide and tetrahydrofuran, or (ii) a solution comprising carbon dioxide, tetrahydrofuran and an aromatic solvent to give a reaction liquid; and (c) hydrolyzing said reaction liquid. Alternatively, a process for producing 1-hydroxythienoimidazole carboxylic acid represented by formula (2), wherein the process comprises the steps of: (a) reacting a thienoimidazole represented by formula (1) with 1,4-dihalogenodimagnesium butane, in the presence of tetrahydrofuran or a mixed solvent comprising tetrahydrofuran and an aromatic solvent to produce a reaction mixture, and wherein the thienoimidazole represented by formula (1) is added to the 1,4-dihalogenodimagnesium butane either solely or in cake state or slurry state, wherein the cake state and slurry state are made by adding a small amount of either tetrahydrofuran or a mixed solvent comprising tetrahydrofuran and an aromatic solvent; (b) reacting the reaction mixture obtained in step (a) with carbon dioxide to produce a reaction liquid; and (c) hydrolyzing the reaction liquid. Additionally, a process of producing thienoimidazole carboxylic acid represented by formula (3): wherein R 1 and R 2 are as defined above utilizing the above processes.

Description: The present invention relates to a process for producing 1-hydroxythienoimidazole carboxylic acid and thienoimidazole carboxylic acid. More particularly, the present invention relates to a process for producing 1-hydroxythienoimidazole carboxylic acid (represented by formula (2) below) and thienoimidazole carboxylic acid (represented by formula (3) below) which are useful as intermediates for the production of biotin (vitamin H). Hitherto, there has been known a process for producing 1-hydroxythienoimidazole carboxylic acid involving the reaction of 4,6-dibenzyl-1,5-dioxohexahydro-1H-thieno[3,4-d]im idazole with 1,4-dihalogenodimagnesium butane, followed by reacting carbon dioxide (Japanese Patent Publication (Kokai) Mo.61-151194). However, as the above process involves the formation of a large amount of byproducts, the yield of 1-hydroxythienoimidazole carboxylic acid is low. As a result, from an industrial perspective, the above process is not ideal. An object of the present invention is to provide a process for producing 1-hydroxythienoimidazole carboxylic acid (2) in good yield and with industrial advantage. The process of this invention is the result of extensive studies relating to solving the problems of, for example, insufficient yield from an industrial perspective. The present invention provides a process (referred to herein as "Process A") for producing a 1-hydroxythienoimidazole carboxylic acid of formula (2): wherein R' and R 2 , which may be the same or different, each represent a C7-C20 aralkyl group or an allyl group, wherein the C7-C20 aralkyl group and allyl group are unsubstituted or are substituted by at least one alkyl group, alkoxy group, nitro group, or halogen atom, wherein the alkyl and alkoxy groups are straight or branched chain and contain from 1 to 6 carbon atoms; which process comprises: (a) reacting a thienoimidazole of formula (1): wherein R 1 and R 2 are as defined above; with 1,4-dihalogenodimagnesium butane, in the presence of tetrahydrofuran; (b) reacting the product thus obtained with carbon dioxide in the presence of tetrahydrofuran, by adding the reaction mixture obtained in step (a) and carbon dioxide to (i) a solution comprising carbon dioxide and tetrahydrofuran, or (ii) a solution comprising carbon dioxide, tetrahydrofuran and an aromatic solvent; and (c) hydrolyzing the product thus obtained to produce the 1-hydroxythienoimidazole carboxylic acid of formula (2). Step (a) and/or step (b) may be carried out in tetrahydrofuran or in a mixed solvent comprising tetrahydrofuran and an aromatic solvent. The present invention also provides processes for producing a thienoimidazole carboxylic acid of formula (3): wherein R 1 and R 2 are as defined above. These processes include using Process A, wherein the thienoimidazole carboxylic acid of formula (3) is obtained through a 1-hydroxythienoimidazole carboxylic acid of formula (2). The present invention is hereinafter described in detail. The thienoimidazole of formula (1), which is used in Process A as a starting material, may be either optically active or racemic, and can be obtained, for example, by a method as described in Japanese Patent Publication (Kokoku) No. 53-27279. The protective groups R 1 and R 2 , which are used in the thienoimidazole of formula (1) to produce the 1-hydroxythienoimidazole carboxylic acid of formula (2) and the thienoimidazole carboxylic acid of formula (3), may each be an aralkyl group or an allyl group. The aralkyl group contains from 7 to 20 carbon atoms, and each of the aralkyl group and allyl group may be unsubstituted or substituted by at least one alkyl group, alkoxy group, nitro group, or halogen atom, the alkyl and alkoxy groups being straight or branched chain and containing from 1 to 6, preferably 1 to 4, carbon atoms. Preferred examples of the unsubstituted or substituted aralkyl group are a benzyl group, α-methylbenzyl group, p-methoxybenzyl group, p-nitrobenzyl group, p-bromobenzyl group, p-chlorobenzyl group, p-methylbenzyl group, naphthylmethyl group, triphenylmethyl group. The benzyl group is particularly preferred. In addition, preferred examples of the unsubstituted or substituted allyl group are allyl group, 2-butenyl group and 3-methyl-2-butenyl group. The solution of 1,4-dihalogenodimagnesium butane in tetrahydrofuran or in a mixed solvent of tetrahydrofuran and aromatic solvent can be prepared by an ordinary Grignard reagent preparing method, for example, by reacting an approximately 0.5 mole of dihalogenobutane, such as 1,4-dichlorobutane and 1,4-dibromobutane, with 1 mole of metal magnesium in tetrahydrofuran or a mixed solvent of tetrahydrofuran and an aromatic solvent. In the present invention, the use of tetrahydrofuran or the use of a mixed solvent of tetrahydrofuran and an aromatic solvent in Process A are collectively referred to as "reaction solvent". When using an aromatic solvent in the reaction solvent of Process A, the weight ratio of the aromatic solvent to tetrahydrofuran is generally in the range of 0.01 to 0.5, preferably 0.02 to 0.25. Examples of the aromatic solvents which can be used in the reaction solvent of Process A include: benzene; alkylbenzenes such as toluene, o-xylene, m-xylene, p-xylene, mixed xylene, ethylbenzene, cumene, cymene and trimethylbenzene; alkoxybenzenes such as anisole; and the like. Of these, benzene, toluene, p-xylene, o-xylene, m-xylene are mixed in Process A. Process A - Production of 1-hydroxythienoimidazole carboxylic acid represented by formula (2) Thienoimidazole represented by formula (1) is added to a solution of (i) 1,4-dihalogenodimagnesium butane in (ii)the aforementioned reaction solvent to produce a reaction mixture. Optionally, a tertiary amine is added to the solution of 1,4-dihalogenodimagnesium butane in the aforementioned reaction solvent. Next, the reaction mixture and carbon dioxide, are added to: (i) a solution comprising carbon dioxide and tetrahydrofuran, or (ii) a solution comprising carbon dioxide, tetrahydrofuran and an aromatic solvent to produce a reaction liquid. Finally, the 1-hydroxythienoimidazole carboxylic acid represented by formula (2) is produced by hydrolyzing the resulting reaction liquid with, for example, water or an aqueous solution such as aqueous ammonium chloride. Preferably, the addition of thienoimidazole represented by formula (1) is made by adding such directly to the solution of 1,4-dihalogenodimagnesium butane, or by adding such in a cake state or slurry state. The cake state and slurry state are prepared by adding a small amount of reaction solvent to the thienoimidazole represented by formula (1). Preferably, an industrially advantageous yield is achieved when the thienoimidazole represented by formula (1) is directly added to the solution of 1,4-dihalogenodimagnesium butane in reaction solvent. The amount to be used for the cake and slurry state of the thienoimidazole represented by formula (1) is no more than 10 times by weight, preferably, no more than 7 times by weight, based on the amount of the thienoimidazole represented by formula (1). Preferred examples of the tertiary amines which may be added to the solution containing the 1,4-dihalogenodimagnesium butane are as follows: trialkyl amines such as triethylamine; N,N,N',N'-alkyl substituted alkylenediamines such as N,N,N',N' -tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediami ne, N,N,N',N'-tetramethyl-1,3-propanediamine; and dialkylamino aromatic compounds such as N,N-dimethylaniline, 1,8-bis(dimethylamino)naphthalene, and the like. Especially preferred is the use of N,N,N',N'-tetramethylethylenediamine. When the tertiary amine is used, the amount of the tertiary amine is generally 0.0001 to 10 mole equivalents, preferably 0.01 to 2 mole equivalents, based on the amount of the thienoimidazole represented by (1). The amount of reaction solvent to be used in this reaction is normally 3 to 50 times by weight, preferably 8 to 20 times by weight, more preferably 10 to 15 times by weight, based on the amount of the thienoimidazole represented by formula (1). The addition time for the thienoimidazole represented by formula (1) to the solution of 1,4-dihalogenodimagnesium butane is generally about 0.1 to 10 hours. The reaction temperature is generally -78 to 10°C, preferably, -50 to -20°C. After the addition of thienoimidazole represented by formula (1), the reaction mixture may be stirring for some time before such is subjected to the reaction with carbon dioxide. Generally, however, the reaction mixture is promptly subjected to the reaction with carbon dioxide. After the reaction mixture is prepared, such is added to either: (i) a solution comprising carbon dioxide and tetrahydrofuran; or (ii) a solution comprising carbon dioxide, tetrahydrofuran and an aromatic solvent (examples include those set forth hereinabove) to give a reaction liquid. The amount of either the tetrahydrofuran or total amount of tetrahydrofuran and aromatic solvent is generally 0.1 to 20 times, preferably, 1 to 10 times, more preferably, 2 to 4 times by weight, based on the weight of the thienoimidazole represented by formula (1). Carbon dioxide may separately be added to the above solutions of: (i) carbon dioxide and tetrahydrofuran; or (ii) carbon dioxide, tetrahydrofuran and an aromatic solvent. The carbon dioxide is added to the above solutions by separately blowing carbon dioxide gas into the above solutions while dropwise adding the reaction mixture. The total amount of the carbon dioxide to be used is generally 1 to 20 equivalents, preferably, 3 to 8 equivalents, based on the amount of the thienoimidazole represented by formula (1). The concentration of carbon dioxide dissolved in the carbon dioxide solution is generally not less than 0.001 kg, preferably, not less than 0.01 kg, more preferably not less than 0.04 kg, based on 1 Kg of either the tetrahydrofuran or the combination of tetrahydrofuran and aromatic solvent. The upper limit of carbon dioxide is determined by that amount of carbon dioxide necessary to prepare a saturated carbon dioxide/tetrahydrofuran solution or a saturated carbon dioxide/tetrahydrofuran/aromatic solvent solution. From the viewpoint of simplification, it is preferred to dissolve the amount of carbon dioxide (in either tetrahydrofuran or tetrahydrofuran and aromatic solvent) necessary to produce a saturated carbon dioxide solution. Dissolution of carbon dioxide in either tetrahydrofuran or the combination of tetrahydrofuran and aromatic solvent is accomplished by, for example, blowing carbon dioxide gas into the tetrahydrofuran or into the combination of the tetrahydrofuran and aromatic solvent. The reaction temperature between the reaction mixture and the carbon dioxide (in the carbon dioxide solution) is generally in the range of -78 to 10°C, preferably -50 to -20°C and the reaction time is generally about 0.1 to 5 hours. If necessary, stirring of the reaction mixture during the addition can be maintained. After the reaction, the reaction liquid is hydrolyzed to give 1-hydroxythienoimidazole carboxylic acid represented by formula (2). This may be accomplished by adding the reaction liquid to water or an aqueous solution such as aqueous ammonium chloride. 1-Hydroxythienoimidazole carboxylic acid represented by formula (2) can be isolated by carrying out ordinary after-treatments such as phase separation, concentration and purification by column chromatography. Alternatively, without isolation, the reaction liquid before hydrolyzation may be directly utilized in the production of thienoimidazole carboxylic acid represented by formula (3). Production of thienoimidazole carboxylic acid represented by formula (3) Thienoimidazole carboxylic acid represented by formula (3) can generally be obtained by dehydrating 1-hydroxythienoimidazole carboxylic acid represented by formula (2) or by hydrolyzing and dehydrating the aforementioned reaction liquid obtained in Process A. When the aforementioned reaction liquid obtained in Process A is used for the reaction, co-existence of proton donor such as water, acid and alcohols, is necessary because of the necessity of hydrolyzation of the reaction liquid prior to dehydration reaction. The amount of proton donor such as water, acid and alcohol is generally 0.1 to 50 times by weight, preferably, 1 to 20 time by weight, more preferably 5 to 10 times by weight, based on the weight of thienoimidazole represented by formula (1). The solvents which can be used in the process may be those referred to hereinabove as the reaction solvent, and aromatic solvents (e.g., xylene, toluene, benzene, and the like). The amount of the solvent is generally 0 to 50 times by weight, preferably, 2 to 20 times by weight, more preferably, 5 to 10 times by weight, based on the weight of thienoimidazole represented by formula (1). Generally, an acidic catalyst is used in the dehydration reaction. As the acidic catalyst, conventional inorganic acid and organic acid may be used. Examples of the acidic catalyst are sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid, hydrogen bromide, p-toluenesulfonic acid, benzene sulfonic acid and methane sulfonic acid. The amount of the acidic catalyst is generally 0.01 to 6 equivalents, preferably, 0.02 to 0.3 equivalent, based on the weight of 1-hydroxythienoimidazole carboxylic acid represented by formula (2). The reaction temperature is generally 10 to 120°C, preferably 20 to 100°C. It is advantageous to carry out the reaction while removing water through azeotropic distillation. Completion of the reaction can be confirmed, for example, by liquid chromatography, thin layer chromatography, and the like. After the reaction, thienoimidazole carboxylic acid represented by formula (3) can be obtained by conventional after-treatments, for example, extracting by aqueous alkali, followed by extracting by organic solvent in neutral or acidic state. If necessary or desired, thienoimidazole carboxylic acid represented by formula (3) may be purified, for example, by recrystallization, column chromatography, and the like. The thienoimidazole carboxylic acid represented by formula (3) can easily be converted into biotin by reduction and then deprotection under acidic conditions in accordance with the methods as described, for example, in Japanese Patent Publication (Kokai) No. 61-151194 or Japanese Patent Publication (Kokoku) No. 63-8954 (=USP 4,537,973). 1-Hydroxythienoimidazole carboxylic acid represented by formula (2) and thienoimidazole carboxylic acid represented by formula (3) are useful as the intermediates for biotin. According to the present invention, such can be produced in high yield and with industrial advantage. Examples of the present invention are provided below. However, the present invention is not to be limited by these examples. Unless otherwise indicated, all parts, percentages, and the like, are by weight. Example 1 To a suspension of 6.9g of magnesium and 80g of tetrahydrofuran, 3g of 1,4-dichlorobutane, and then a solution comprising 0.1g of iodine and 2g of tetrahydrofuran were dropwise added at 50°C. 65g of tetrahydrofuran was added to the resulting solution, and then 14.2g of 1,4-dichlorobutane was added while refluxing for 30 minutes. After completion of the addition, the mixture was stirred at 60 - 65°C for 3 hours. The solution was dropwise added to the solution comprising 20g of tetrahydrofuran and 23g of toluene, which was cooled to -25 - -20°C at the same temperature in 0.5 hours, after which 25.4g of (3aS, 6aR)-4,6-dibenzyl-1,5-dioxohexahydro-1H-thieno[3,4-d]imidazole was added thereto at a liquid temperature of -35°C in 0.5 hour. The resulting mixture was dropwise added to 85 g of a solution of tetrahydrofuran (cooled to -25 to -5°C) in which carbon dioxide gas (1.5 equivalents to (3aS, 6aR)-4,6-dibenzyl-1,5-dioxohexahydro-1H-thieno[3,4-d]imidazole) was previously blown and dissolved thereto, simultaneously with the blowing in of carbon dioxide gas (3.5 equivalents) at the same temperature in an hour. The resulting reaction liquid was dropwise added to 15% sulfuric acid, incorporated with 28g of toluene, and the mixture was stirred for 1 hour, followed by separating the aqueous layer. The organic layer was incorporated with 160g of toluene, and concentrated under reduced pressure. The residue was incorporated with 5% sodium hydroxide, stirred, and the mixture was phase-separated, after which toluene was added to the aqueous layer, which was adjusted to pH 6.5 with 30% sulfuric acid, and then phase-separated. The organic layer was concentrated to give 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imidazole-1-ylidene)pentanoic acid as an oily substance. Calculating the net yield of pure 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imidazole-1-ylidene)pentanoic acid using liquid chromatography, we found that it was 29.5g. The resulting compound was recrystallized with 2-propanol and hexane to show the physical properties of 84-85°C of melting point; [α]D 20 = 236.2°(C = 1.0, methanol). Example 2 In the same manner as in Example 1 except that the temperature in the addition of (3aS, 6aR)-4,6-dibenzyl-1,5-dio xohexahydro-1H-thieno(3,4-d]imidazole was set at -25°C, the reaction and after-treatment were carried out to obtain 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imida zole-1-ylidene)pentanoic acid as an oily substance. Calculating the net yield of pure 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imidazole-1-ylidene)pentanoic acid using liquid chromatography, we found that it was 28.5g. Example 3 In the same manner as in Example 1 except that the temperature in the addition of (3aS, 6aR)-4,6-dibenzyl-1,5-dio xohexahydro-lH-thieno[3,4-d]imidazole is set at -45°C, the reaction and after-treatment are carried out to obtain 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imida zole-1-ylidene)pentanoic acid as an oily substance. Reference Example 1 To a suspension of 6.9g of magnesium and 80g of tetrahydrofuran, 3g of 1,4-dichlorobutane, and then a solution comprising 0.1g of iodine and 2g of tetrahydrofuran were dropwise added at 50°C. 65g of tetrahydrofuran was added to the resulting solution, and then 14.2g of 1,4-dichlorobutane was dropwise added while refluxing for 30 minutes. After completion of the addition, the mixture was stirred at 60 to 65°C for 3 hours. The solution was dropwise added to the solution comprising 20g of tetrahydrofuran and 23g of toluene, which was cooled to -25 - -20°C, at the same temperature in 0.5 hour, after which 25.4g of (3aS, 6aR)-4,6-dibenzyl-1,5-dioxohe xahydro-1H- thieno[3,4-dlimidazole was added thereto at a liquid temperature of -35°C in 0.5 hours. Thereafter, carbon dioxide gas (6 equivalents to (3aS, 6aR)-4,6-dibenzyl-1,5-diox ohexahydro-1H-thieno[3,4-d]imidazole) was introduced in an hour. The reaction liquid was poured into 15% sulfuric acid, incorporated with 28g of toluene, and the mixture was stirred for an hour, followed by separating the aqueous layer. The organic layer was incorporated with 160g of toluene and concentrated under reduced pressure. The residue was incorporated with 5% sodium hydroxide, and the mixture was stirred and phase-separated, after which toluene was added to the aqueous layer, which was adjusted to pH 6.5 with 30% sulfuric acid, and the liquid was phase-separated. The organic layer was concentrated to obtain 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imidazole-1-ylidene)-pentanoic acid as an oily substance. Calculating the net yield of pure 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro-1H-thieno[3,4-d]imidazole-1-ylidene)-pentanoic acid using liquid chromatography, we found that it was 28.5g. The resulting compound was recrystallized with 2-propanol and hexane to show the physical properties of 84-85°C of melting point; [α]D 20 = 236.2°(C = 1.0, methanol). Example 4 In the same manner as in Reference Example 1, 1,4-dichlorodimagnesium butane was prepared, to which 90g of tetrahydrofuran was added, and the mixture was cooled to -35°C. To the mixture, a slurry comprising 25.4g of (3aS, 6aR)-4,6-dibenzyl-1,5-dioxohexahydro-1H-thieno[3,4-d]imidazole and 120g of tetrahydrofuran cooled to -30°C was dropwise added while the temperature in the reactor was kept at -35°C over 0.5 hour. Thereafter, the reaction and after-treatments were carried out in the same manner as in Example 1 to obtain 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro- 1H-thieno[3,4-d]imid azole-1-ylidene)pentanoic acid as an oily substance. Calculating the net yield of pure 5-((3aS,6aR)-4,6-dibenzyl-5-oxohexahydro- 1H-thieno[3,4-d]imidazole-1-ylidene)pentanoic acid using liquid chromatography, we found that it was 28.5g. Example 5 To a suspension of 6.9g of magnesium and 80g of tetrahydrofuran, 3g of 1,4-dichlorobutane, and then a solution comprising 0.1g of iodine and 2g of tetrahydrofuran were dropwise added at 50°C. 65g of tetrahydrofuran was added to the resulting solution, and then 14.2g of 1,4-dichlorobutane was dropwise added while refluxing for 30 minutes. After completion of the addition, the mixture was stirred at 60-65°C for 3 hours. The solution was dropwise added to the solution comprising 20g of tetrahydrofuran and 23g of toluene which was cooled to -25 - -20°C at the same temperature in 0.5 hours, after which 25.4g of (3aS, 6aR)-4,6-dibenzyl-1,5-dioxoh exahydro-1H- thieno[3,4-d]imidazole was added thereto at a liquid temperature of -35°C in 0.5 hours. The resulting mixture was dropwise added to 85 g of a solution of tetrahydrofuran cooled to -25 to -5°C in which carbon dioxide gas (1.5 equivalents to (3aS, 6aR)-4,6-dibenzyl-1,5-dioxohexah ydro-1H- thieno[3,4-d]imidazole) was previously blown and dissolved thereinto, simultaneously with the blowing in of carbon dioxide gas (3.5 equivalents) at the same temperature in an hour. The reaction mixture was poured into water, incorporated with 28g of toluene, and the mixture was stirred for 1 hour, followed by separating the aqueous layer. The organic layer was concentrated to obtain 5-(4,6-dibenzyl-1-hydroxy-5-oxohexahydro-1H-thieno[3,4-d]imidazol-1-yl)pentanoic acid as an oily substance. Calculating the net yield of pure 5-(4,6-dibenzyl-1-hydroxy-5-oxohexahydro-1H-thieno[3,4-d]imida zol-1-yl)pentanoic acid using liquid chromatography, we found that it was 30.8 g.

Claims: A process for producing a 1-hydroxythienoimidazole carboxylic acid of formula (2): wherein R 1 and R 2 , which may be the same or different, each represent a C7-C20 aralkyl group or an allyl group, wherein the C7-C20 aralkyl group and allyl group are unsubstituted or are substituted by at least one alkyl group, alkoxy group, nitro group, or halogen atom, wherein the alkyl and alkoxy groups are straight or branched chain and contain from 1 to 6 carbon atoms; which process comprises: (a) reacting a thienoimidazole of formula (1): wherein R 1 and R 2 are as defined above; with 1,4-dihalogenodimagnesium butane, in the presence of tetrahydrofuran; (b) reacting the product thus obtained with carbon dioxide in the presence of tetrahydrofuran, by adding the reaction mixture obtained in step (a) and carbon dioxide to (i) a solution comprising carbon dioxide and tetrahydrofuran, or (ii) a solution comprising carbon dioxide, tetrahydrofuran and an aromatic solvent; and (c) hydrolyzing the product thus obtained to produce the 1-hydroxythienoimidazole carboxylic acid of formula (2). A process according to claim 1, wherein step (a) and/or step (b) are carried out in a mixed solvent comprising tetrahydrofuran and an aromatic solvent. A process according to claim 2, wherein the aromatic solvent is selected from the group consisting of benzene, toluene, o-xylene, m-xylene, p-xylene and mixed xylene. A process according to claim 1, wherein the solution comprising carbon dioxide and tetrahydrofuran and the solution comprising carbon dioxide, tetrahydrofuran and aromatic solvent are saturated with carbon dioxide. A process according to any one of the preceding claims, wherein the thienoimidazole of formula (1) is added to the reaction in step (a) either directly or as a cake or slurry, wherein the cake or slurry is made by adding to the thienoimidazole of formula ( I ) either tetrahydrofuran or a mixed solvent comprising tetrahydrofuran and an aromatic solvent in an amount of no more than 10 times the amount by weight of the thienoimidazole of formula (1). A process according to any one of the preceding claims, wherein step (a) is carried out in the presence of a tertiary amine. A process according to claim 6, wherein the tertiary amine is N,N,N',N'-tetramethylethylenediamine. A process for producing a thienoimidazole carboxylic acid of formula (3): wherein R 1 and R 2 are as defined in claim 1, which process comprises hydrolyzing and dehydrating the product obtained in step (b) of a process according to any one of claims 1 to 7. A process according to any one of the preceding claims, wherein at least one of R 1 and R 2 is a benzyl group. A process according to claim 8 or 9, followed by the step of converting the thienoimidazole carboxylic acid of formula (3) into biotin.

Inventors: HIRATA NORIHIKO, MIYAMOTO YASUNOBU, MIZUNO MASAHIKO, TAKAHASHI TOSHIYA, HIRATA, NORIHIKO, MIYAMOTO, YASUNOBU, MIZUNO, MASAHIKO, TAKAHASHI, TOSHIYA
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY, LIMITED
Application year: 1996
Main classification: C07D495
IPC codes: C07D495