The syntheses of 4-arylamino-1,2,3-triazoles and stable 6-sydnonyl verdazyls from sydnone derivatives and their fragments

alpha -Chloroformylarylhydrazones 1 and alpha -chloroformylarylhydrazones o f sydnonecarbaldehydes 3 have been prepared by a new synthetic route: alpha -chloroformylarylhydrazines hydrochlorides 2 reacted with corresponding ca rbonyl compounds. Reactions of compounds 3 with various hydrazines to give 6-sydnonyl-1,2,4,5-tetrazinan-3-ones 7 and/or carbazones 8 were also invest igated. By oxidization with lead dioxide, compounds 7 were transformed to s table 6-sydnonyl-3,4-dihydro-3-oxo-1,2,4,5-tetrazin-1(2H)-yl radical deriva tives 9 (sydnonyl verdazyls). Furthermore, sydnonecarbaldehydes arylhydrazo nes 5 through acidic conditions could be transferred to 4-arylamino-1,2,3-t riazoles 6 Which were also obtained by means of acidic decompositions of 4- formylsydnones 10.