Nickel-Catalyzed Reductive Arylalkylation of Alkenes: 5-Exo Cyclization vs. 6-Endo Cyclization vs. 1,2-Aryl Migration to 6-Endo Product

Abstract

The detailed mechanisms of Ni-catalyzed reductive arylalkylation of unactivated alkenes with aryl bromides to synthesize benzene-fused 5-exo and 6-endo cyclic compounds were systematically investigated by DFT calculations. Our finding reveals that, under the catalysis of a Ni/biOx system with Zn as a reductant, bromobenzene containing a terminal olefins unit preferentially undergoes traditional Heck cyclization and cross-coupling reactions, favoring the formation of 5-exo cyclization products. In contrast, when Zn is absent, NiIII-alkyl species play a pivotal role, facilitating a rare 1,2-aryl migration followed by H-atom abstration, which selectively yields 6-endo cyclization products.