Ligand-Dictated Regiodivergent Allylic Functionalizations via Palladium-Catalyzed Remote Substitution

Different from classical allylic substitutions that require a vicinal leaving group, an olefin bearing a remote leaving group is scarcely viewed as a potential allylation substrate. Herein, we describe feasible protocols to achieve regiodivergent allylic C-H functionalizations via palladium-catalyzed remote substitution, which provides a novel strategy for the seldomly studied migratory Tsuji-Trost reaction. Dictated by a suitable ligand, a process that involved 4,3-hydrofunctionalization of the generated conjugated diene intermediate via metal walking is observed in generally >20 : 1 regioselectivity. Unexpectedly, a related 1,4-hydrofunctionalization pathway is found to be a major route with a newly synthesized electron-rich bisphosphine ligand, which challenges the conventional viewpoint on the potential regioselectivity of hydrofunctionalizations of linear internal conjugated dienes via eta(3)-substitution. A series of deuterium experiments and kinetic studies provide a preliminary insight into the potential catalytic cycle.