Allylic C(sp 3)–H arylation of olefins via ternary catalysis

Abstract

Transforming C(sp 3)–H bonds efficiently and selectively into C(sp 3)–C(sp 3) or C(sp 3)–X bonds is a highly relevant task. The direct arylation of allylic C(sp 3)–H bonds provides an elegant method for the formation of unconjugated aryl-substituted olefins. Although both ionic- and radical-based transition metal catalysis has been applied to achieve this transformation, numerous challenges remain. The requirement for persistent radical coupling partners, moderate selectivity and the need for tri- or tetrasubstituted olefins have limited the generality of existing methods. Now we report a ternary catalytic method that combines organic photoredox, hydrogen atom transfer and nickel catalysis, and can directly arylate allylic C(sp 3)–H bonds of readily available olefins. This process operates under mild conditions and exhibits a remarkable reaction scope in both aryl halide and olefin coupling partners. Mechanistic experiments, coupled with density functional theory calculations of Ni-oxidation states and reaction energetics allowed the elucidation of a ternary catalytic cycle and the origin of regioselectivity. [Figure not available: see fulltext.]