A telescoped protocol for the synthesis of new pyrrolo [3,4-d]pyridazinones by cascade reactions

Abstract

A new one-pot method, for the synthesis of polysubstituted pyrrolo[3,4-d]pyridazinones, is presented. The protocol consists in cascade reactions performed in the same media: (i) the thermal in situ pyrrole formation by the reaction of vinyl azides with 1,3-dicarbonyl compounds, via the 1,2-addition of 1,3-dicarbonyl compounds to 2H-azirine intermediates; (ii) the nucleophilic addition of hydrazines to the ketone group present in the pyrroles previously formed, followed by intramolecular cyclization with the bordering ester, which furnishes the respective pyrrolo[3,4-d]pyridazinones, substituted at the pyrrole and/or pyridazinone rings. All transformations occur in a two-step one-pot methodology, and a series of ten new compounds were obtained at yields of 42–87%.