C(=O)([O-])[O-].[K+].[K+].Cl[C:8]1[N:16]=[CH:15][CH:14]=[CH:13][C:9]=1[C:10]([OH:12])=[O:11].[CH2:17]([SH:24])[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1.O>CS(C)=O>[C:18]1([CH2:17][S:24][C:8]2[C:9]([C:10]([OH:12])=[O:11])=[CH:13][CH:14]=[CH:15][N:16]=2)[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1In a stirred suspension of 96.37 gm potassium carbonate in 700 gm dimethyl sulphoxide, 100 gm 2-chloro nicotinic acid was charged. A solution of 82.38 gm benzyl mercaptan in 300 gm dimethyl sulphoxide was added in a period of two hours maintaining reaction temperature 80-90 deg. c. The temperature of the reaction was raised up to 140 deg. c. and then maintained for another three hours. 500 gm water was added after completion of the reaction and solvent recovery. Product precipitation achieved by lowering the pH of the reaction mass by using dilute HCl. Product 2-(Phenyl methyl thio)-3-pyridine carboxylic acid precipitated completely till pH 4.5. After filtration and washing, cake was dried to get 75.5 gm white to off white solid product 2-(Phenyl methyl thio)-3-pyridine carboxylic acid with 49.07% yield (Assay by HPLC 99.16%).
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