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

Abstract

Different from classical allylic substitutions requiring a vicinal leaving group, an olefin bearing a remote leaving group is scarcely viewed as a potential allylation substrate. Here we describe feasible protocols to achieve the regiodivergent allylic C-H functionalizations via palladium-catalyzed remote substitution, which provides a novel strategy for seldomly studied migratory Tsuji-Trost reaction. With the dictation of a suitable ligand, a processinvolved 4,3-hydrofunctionalization of the generated conjugated diene intermediate via metal walking is observed in generally >20:1 regioselectivity. Unexpectedly, related 1,4-hydrofunctionalization pathway is tuned to work as a major route with a newly synthesized electron-rich bisphosphine ligand, which breakouts the conventional viewpoint on the potential regioselectivity of hydrofunctionalizations of linear internal conjugated dienes via ƞ3-substitution. A series of deuterium experiments and kinetic studies provide preliminary insight into the potential catalytic cycle.