Synthesis of 1‐amino‐[1,2,3]oxadiazolo[4,3‐α]phthalazin‐4‐ium chloride and substituted dihydro derivatives. New annelated sydnonimines

Abstract

Abstract The sydnonimine 5 has been prepared by an original one‐pot nitrosation and cyclisation procedure of the carbonyl chloride Reissert adduct 14 of phthalazine. This synthetic method could be extended to the preparation of dihydro derivatives 7a to 7f and represents a new access to annelated sydnonimines. The para anisoyl and ethoxycarbonyl derivatives of these sydnonimines were also prepared with analogy to molsidomine 1 or pirsidomine 2 .