A novel and facile synthesis of mesoionic 1,2,4-triazolium-3-thiolate derivatives

Mesoionic 1,2,4-triazolium-3-thiolate derivatives were synthesized from the reaction of N-substituted-2-phenylhydrazinocarbothioamides with tetracyanoethylene (TCNE) to give tricyanovinyl intermediates, followed by heterocyclization to afford 5-(1-amino-2,2-dicyano-vinyl)-4-substituted-1-phenyl-4H-1,2,4-triazol-1-ium-3-thiolates in 67–76% yields. The structures of the products have been confirmed unambiguously by single crystal X-ray structure analyses. A rationale for the formation of the products is presented.