NC(N)=[S:3].[F:5][C:6]1[CH:13]=[CH:12][C:9]([CH2:10]Cl)=[CH:8][CH:7]=1.[OH-].[Na+].Cl[CH2:17][C:18]([O-:20])=O.[Na+].Cl>O.C(Cl)Cl.C1CCCCC1>[F:5][C:6]1[CH:13]=[CH:12][C:9]([CH2:10][CH2:17][C:18]([OH:20])=[S:3])=[CH:8][CH:7]=1A solution of 15.2 g (0.2 mol) of thiourea in 100 ml of water is introduced into a 1 liter 3-necked flask equipped with a magnetic stirrer, a condenser and dropping funnel, and 28.9 g (0.2 mol) of p-fluorobenzylchloride are introduced, at 50°-60° C., in a single operation. The mixture is heated to reflux and boiling is maintained for about 15 minutes; the solution becomes limpid. Thereafter the mixture is cooled and a solution of 32 g (0.8 mol) of NaOH in water is added dropwise at about 60° C. The whole is heated under reflux for about 30 minutes and cooled and a solution of about 0.28 mol of sodium chloroacetate (obtained by neutralising 26.46 g of chloroacetic acid in 200 ml of water with 23.52 g of sodium bicarbonate) is added dropwise at 60°-70° C. Thereafter the whole is heated under reflux for 30 minutes, and then cooled. The mixture is acidified with 3 N HCl, the oil obtained is taken up in methylene chloride, the solution is washed with a dilute solution of sodium bicarbonate, filtered over charcoal and acidified once more with 3 N HCl and p-fluorobenzylthioacetic acid thus precipitates and is filtered off. After recrystallisation from cyclohexane, 33.4 g (yield: 83%) of the said acid are collected. Instantaneous melting point: 68°-69° C.
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