Cl.[CH2:2]([O:4][C:5]1[CH:6]=[C:7]([CH:16]=[CH:17][C:18]=1[O:19][CH2:20][CH3:21])[CH2:8][CH:9]1[S:13][C:12](=N)[NH:11][C:10]1=[O:15])[CH3:3].[OH2:22]>C(O)C>[CH2:2]([O:4][C:5]1[CH:6]=[C:7]([CH:16]=[CH:17][C:18]=1[O:19][CH2:20][CH3:21])[CH2:8][CH:9]1[S:13][C:12](=[O:22])[NH:11][C:10]1=[O:15])[CH3:3]In a mixture of 60 ml ethanol and 60 ml 1N-HCl is dissolved 5.0 g of the 5-(3,4-diethoxybenzyl)-2-iminothiazolidin-4-one prepared above and the solution is heated under reflux for 8 hours. The reaction solution is cooled, and water is added thereto. The aqueous mixture is subjected to extraction with chloroform to give 4.3 g (86.0%) of 5-(3,4-diethoxybenzyl)thiazolidine-2,4-dione as crystals. Recrystallization from ethyl acetate-n-hexane yields colorless prisms melting at 98°-99° C.
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