[Cl:1][C:2]1[C:7]([Cl:8])=[C:6]([O:9][CH3:10])[CH:5]=[CH:4][C:3]=1[SH:11].[H-].[Na+].Br[CH:15]([CH2:19][CH3:20])[C:16]([OH:18])=[O:17].Cl>CN(C)C=O.O>[Cl:1][C:2]1[C:7]([Cl:8])=[C:6]([O:9][CH3:10])[CH:5]=[CH:4][C:3]=1[S:11][CH:15]([CH2:19][CH3:20])[C:16]([OH:18])=[O:17]
To a solution of 4.4 g of 2,3-dichloro-4-methoxythiophenol in 30 ml of anhydrous dimethylformamide is added 1.2 g of sodium hydride in small portions. The mixture is stirred at room temperature until gas evolution subsides (20-30 minutes) and 3.34 g of α-bromobutyric acid in 10 ml of dimethylformamide is added. After stirring at room temperature for 1 hour, the mixture is diluted with water and acidified with conc. hydrochloric acid. The white crystalline solid is filtered, air dried and recrystallized from acetone-hexane to give 5.32 g of α-(2,3-dichloro-4-methoxyphenylthio)butyric acid as granular crystals, mp 143°-145°.
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