N‑Heterocyclic Carbene-Catalyzed Oxidative Annulations of α,β-Unsaturated Aldehydes with Hydrazones: Selective Synthesis of Optically Active 4,5-Dihydropyridazin-3-ones and Pyridazin-3-ones

A novel and efficient
method for the highly enantioselective synthesis
of chiral 4,5-dihydropyridazin-3-one derivatives has been developed
based on the chiral N-heterocyclic carbene-catalyzed oxidative annulation
between α,β-unsaturated aldehydes and hydrazones. Meanwhile,
the selective synthesis of either 4,5-dihydropyridazin-3-ones or pyridazin-3-one
derivatives from the same reactants has been achieved by simply varying
catalytic and reaction conditions.