Pyrazole, pyrazolo[1,2-c]-1,3,4-thiadiazole and thiadiazepine derivatives from thiosemicarbazides

Thiosemicarbazides 1a-c reacted with tetracyanoethene 2 in ethyl acetate with admission of air to form the 7-amino-2-organylimino-2,3-dihydro-1,3,4-thiadiazepine-5,6-dicarbonitriles 6a, b, 7-amino- 1-organylimino-3-oxopyrazolo[1,2- c]-1,3,4-thiadiazole-5,5,6-tricarbonitriles 7a - c, 7-amino- 1-organyl-iminopyrazolo[1,2- c]-1,3,4-thiadiazole-3,3,5,5,6-pentacarbonitriles 8a - c and 3-amino- 1H-pyrazole-4,5-dicarbonitriles (9) in moderate yields. Rationales for the observed conversations are presented.