Phosphine-Catalyzed Modular Synthesis of (E)‑Allyl Hydrazones, Tetrahydropyridazines, and Pyridazines

A novel phosphine-catalyzed three-component reaction has been developed for the efficient construction (E)-allyl hydrazones/oximes. This transformation proceeds with excellent chemo- and regioselectivity while exhibiting remarkable functional group tolerance and broad substrate scope. Biologically relevant tetrahydropyridazines and pyridazines could also be readily synthesized via allylation/6-endo-trig processes in either a stepwise or one-pot manner. The utility of this methodology is further demonstrated by the use of N-allyl (pyridin-2-yl)­hydrazones as configurationally stable ligands for Ullmann C–N coupling.