[Cl:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[Cl:13])[CH2:5][CH2:6][C:7](O)=[S:8].OS(O)(=O)=O.ClC(Cl)C.[NH2:23][OH:24].C[O-].[Na+]>CO>[Cl:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[Cl:13])[CH2:5][CH2:6][C:7]([NH:23][OH:24])=[S:8]
20.2 g (0.08 mol) of 3,4-dichlorobenzylthioacetic acid are esterified with 10 ml of methanol, 0.6 ml of concentrated H2SO4 and 100 ml of dichloroethane. The mixture is heated under reflux for 4 hours, washed with water and with dilute bicarbonate solution, and dried. The mixture is evaporated in vacuo. The oily residue, in methanol, is treated with a solution of hydroxylamine (0.1 mol) in the presence of 0.18 mol of sodium methylate. After leaving the reactants in contact overnight, the mixture is evaporated to dryness in vacuo, the residue is taken up in water, the mixture is filtered over charcoal and the filtrate is precipitated with 3N HCl, the product is extracted with ether, the extract is dried and evaporated and the product is crystallised in diisopropyl ether. 15 g of the stated product are obtained (yield 71%). Melting point: 75°-76° C.
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