Novel pyrimidinediones and thiazolidinones as anti depressants.

2-Mercapto-5-[4'-methoxy phenyl thiourea]-1,3,4-thiadiazole (2a-c) prepared by the condensation of 2-amino-5-mercapto-1,3,4-thiadiazole (1) with substituted phenyl isothiocyanates. Further on cyclisation with malonic acid in the presence of acetyl chloride gave the corresponding 2-mercapto-5-[3-(4-methoxy phenyl)-2-thioxo-2-5-dihydro-4, 6-pyrimidionoyl]-1,3,4-thiadiazole (3a-c) [sequence: see text]. This on further reaction with substituted aryl aldehydes in presence of zinc chloride gave 2-mercapto-5-[3-(4'-methoxy phenyl)-2'-thioxo-2',5'-dihydro-4',6' -pyrimidionoyl 5'-phenyl carboxaldehyde]-1,3,4- thiadiazole (4a-g) [sequence: see text]. The compounds were screened for antidepressant activity and compared with antidepressant (imipramine).