Acid/Base-Tuned\nAsymmetric Reductive Heck and\nDenitrogenative Heck Reactions of In\nSitu-Formed α,β-Unsaturated Hydrazone

Despite significant progress in the catalytic asymmetric\n1,4-additions\nbetween various Michael donors and acceptors, the exploration of organohalide\ndonors remains elusive. Herein, we report the Pd(0)-catalyzed asymmetric\nintramolecular 1,4-additions of vinyl/aryl iodides to α,β-unsaturated\nhydrazones, featuring in situ-formed hydrazone and acid/base-tuned\nreaction pathways. Due to its strong coordination ability, the hydrazone\nis capable of steering the C–C bond formation to follow the\n1,4-addition mechanism instead of the conventional alkene insertion,\nthus enabling the generation of vinylhydrazinyl–Pd<sup>2+</sup> species via the Zimmerman–Traxler chairlike transition state.\nNotably, this species preferentially undergoes protonation under acidic\nconditions, furnishing a reductive Heck reaction with the aid of a\nnative hydrazine reductant, while it is susceptible to β-H<sub>N</sub> elimination under basic conditions to achieve a denitrogenative\nHeck reaction. The catalytic protocol affords highly enantioselective\naccess to diverse heterocycles, with alkene and hydrazone groups poised\nfor further chemical manipulations.