[SH:1][CH2:2][C:3]([O:5][CH2:6][CH3:7])=[O:4].CC[O-].[Na+].C(O)C.Br[CH2:16][C:17]1[CH:22]=[CH:21][C:20]([CH3:23])=[CH:19][CH:18]=1>ClCCl>[CH3:16][C:17]1[CH:22]=[CH:21][C:20]([CH2:23][S:1][CH2:2][C:3]([O:5][CH2:6][CH3:7])=[O:4])=[CH:19][CH:18]=1Ethyl 2-mercaptoacetate (8.5 cc) is added in the course of 15 minutes at a temperature in the region of 20° C. to a stirred solution, through which a stream of nitrogen is passed, of a 2M ethanolic solution of sodium ethylate (37.5 cc) and ethanol (50 cc). The mixture is left with stirring for 15 minutes at the same temperature, and α-bromo-p-xylene (13.9 g) is then added in the course of 20 minutes at a temperature in the region of 20° C. Stirring is maintained for 60 minutes at this temperature, and the reaction mixture is then evaporated to dryness at 50° C. under reduced pressure (20 mm Hg; 2.7 kPa). The residue obtained is dissolved in dichloromethane (100 cc), and the organic phase is dried over anhydrous magnesium sulphate, filtered and concentrated to dryness at 40° C. under reduced pressure (20 mm Hg; 2.7 kPa). Ethyl (4-methylbenzylthio)acetate (15.6 g) is thereby obtained, and is used in the crude state in the subsequent syntheses.
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