New access to pyrazole, oxa(thia)diazole and oxadiazine derivatives

1,4-Disubstituted thiosemicarbazides 1b-f reacted with ethenetetracarbonitrile (5) in dimethylformamide with formation of 2-substituted 5-phenyl-1,3,4-thiadiazoles 2a-f and 2-substituted 5-phenyl-1,3,4-oxadiazoles 4a-f. Upon addition of 5 to 1c-e in chlorobenzene, 3-amino-2-benzoyl-4,5,5-tricyano-2,5-dihydro-1H-pyrazole-1-[N-(4-tricyanovinyl)phenyl]carbothioamide (12), 5-benzylamino-, and 5-allylamino-4-benzoyl-2,3-dihydro-[1,3,4]thiadiazol- 2,2-dicarbonitrile (13a,b) and 5-amino-1-benzoylpyrazole-3,4-dicarbonitrile (14) as well as 2-phenyl-4H-[1,3,4]-oxadiazine-5,6-dicarbonitrile (15) were formed. Rationales for the role of the solvent and the conversions observed are presented. (C) 2005 Wiley Periodicals, Inc.