Lewis Acid Catalyzed Annulation of Cyclopropane Carbaldehydes and Aryl Hydrazines: Construction of Tetrahydropyridazines and Application Toward a One-Pot Synthesis of Hexahydropyrrolo[1,2‑<i>b</i>]pyridazines

In this report, a facile synthesis of tetrahydropyridazines via a Lewis acid catalyzed annulation reaction of cyclopropane carbaldehydes and aryl hydrazines has been demonstrated. Moreover, the generated tetrahydropyridazine further participated in a cycloaddition reaction with donor–acceptor cyclopropanes to furnish hexahydropyrrolo­[1,2-b]­pyridazines. We also performed these two steps in one pot in a consecutive manner. In addition, a monodecarboxylation reaction of hexahydropyrrolo­[1,2-b]­pyridazine was achieved with a good yield.