Phosphine-catalyzed [3+2] and [3+3] Annulations of Azomethine Imines with Ethyl 2-Butynoate

The phosphine-catalyzed [3 + 2] and [3 + 3] annulation reactions of azomethine imines and ethyl 2-butynoate were developed, providing 1,2-dinitrogen-containing heterocycles tetrahydropyrazolopyrazolones and tetrahydropyrazolopyridazinones in moderate to good yields.