# US 7,745,631 B2 · Process for producing 2-(phenyl methyl thio)-3-pyridine carboxylic acid

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- Number: US 7,745,631 B2
- Document ID: US7745631B2
- Status: Granted
- Kind: B2
- Application number: 11/547,407
- Filed: 2004-06-17
- Published: 2008-06-12
- Granted: 2010-06-29
- Earliest claimed: 2004-04-12
- Assignees: Jubilant Organosys Limited
- Inventors: Shailendra Kumar Singh; Ashutosh Agarwal
- Web page: https://patentgrep.com/patent/US7745631B2

## CPC

- C07D 213/80: in position 3
- C07D 213/85: in position 3
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)

## Abstract

The invention discloses an improved process for producing an intermediate to produce large quantity of 2-(Phenyl methyl thio)-3-pyridine carboxylic acid. The process comprises reacting 2-chloro-3-cyanopyridine with benzyl mercaptan in presence of a base and an aprotic solvent. The resulting intermediate 2-(phenyl methyl thio)-3-cyanopyridine is hydrolyzed in presence of a base in an autoclave and isolated under acidic condition to get the desired product.

## Claims

### Claim 1

A process for producing 2-(Phenyl methyl thio)-3-pyridine carboxylic acid, consisting essentially of:
reacting 2-chloro-3-cyanopyridine with benzyl mercaptan in the presence of a base and an aprotic solvent;
separating inorganic cake by filtration;
recovering the aprotic solvent to obtain an intermediate;
hydrolyzing resulting intermediate in the presence of a base in autoclave;
isolating the resultant under acidic conditions followed by washing and drying to produce 2-(Phenyl methyl thio)-3-pyridine carboxylic acid.

### Claim 2 (depends on 1)

The process according to claim 1, wherein the intermediate is 2-(Phenyl methyl thio)-3-cyanopyridine.

### Claim 3 (depends on 1)

The process according to claim 1, wherein the aprotic solvent is dimethyl formamide.

### Claim 4 (depends on 1)

The process according to claim 1, wherein the reaction is carried out at a temperature of 70°-150° C.

### Claim 5 (depends on 4)

The process according to claim 4, wherein the preferred range of temperature is 80°-140° C.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the reaction time for producing the intermediate is 2 to 8 hours.

### Claim 7 (depends on 6)

The process according to claim 6, wherein the preferred reaction time is 2 to 5 hours.

### Claim 8 (depends on 1)

The process according to claim 1, wherein the molar ratio of 2-chloro-3-cyanopyridine to benzyl mercaptan is in the range of 1:0.5-1:3.

### Claim 9 (depends on 8)

The process according to claim 8, wherein the preferred molar ratio is in the range of 1:0.9-1:1.2.

### Claim 10 (depends on 1)

The process according to claim 1, wherein the mole ratio of 2-chloro-3-cyanopyridine to base is 1:0.6-1:2.

### Claim 11 (depends on 10)

The process according to claim 10, wherein the preferred mole ratio is 1:1-1:1.5.

### Claim 12 (depends on 1)

The process according to claim 1, wherein said intermediate produced is usable for hydrolyzing to obtain 2-(Phenyl methyl thio)-3-pyridine carboxylic acid, without purifying the same after the recovery of aprotic solvent.

### Claim 13 (depends on 1)

The process according to claim 1, wherein the reaction temperature for producing 2-(Phenyl methyl thio)-3-pyridine carboxylic acid from intermediate is 100° C. to 180° C.

### Claim 14 (depends on 13)

The process according to claim 13, wherein the preferred reaction temperature is 130° C. to 160° C.

### Claim 15 (depends on 1)

The process according to claim 1, wherein the reaction time for producing 2-(Phenyl methyl thio)-3-pyridine carboxylic acid from intermediate is 4 to 12 hours.

### Claim 16 (depends on 15)

The process according to claim 15, wherein the preferred reaction time is 6 to 9 hours.

### Claim 17 (depends on 1)

The process according to claim 1, wherein the reaction pressure for producing 2-(Phenyl methyl thio)-3-pyridine carboxylic acid from intermediate is 30 to 100 psig.

### Claim 18 (depends on 17)

The process according to claim 17, wherein the preferred reaction pressure is 55 to 75 psig.

### Claim 19 (depends on 1)

The process according to claim 1, comprising acidifying the reaction mass obtained after the base hydrolysis, filtering the acidified reaction mass, washing the resultant with water, followed by drying to obtain 2-(Phenyl methyl thio)-3-pyridine carboxylic acid.

### Claim 20 (depends on 1)

The process according to claim 1, wherein the process comprising isolating the resultant in acidic condition by adding hydrochloric acid till pH 3.0.