Cobalt-Catalyzed Regiodivergent Heck-Type Reaction of Simple Unactivated Alkenes

Abstract

Regiocontrol has been a long-standing challenge in the Heck-type reaction of unactivated alkenes due to the presence of multiple detachable β-hydrogens, but it also represents an intriguing research topic owing to the potential for accessing structurally diverse internal aliphatic alkenes. Herein, a cobaltcatalyzed regiodivergent Heck-type reaction of simple unactivated alkenes and fluoroalkyl bromides is reported, yielding a variety of internal aliphatic olefins containing biologically relevant fluorinated moieties. This directing-group-free protocol shows a broad substrate scope encompassing terminal, 1,1-disubstituted, and internal alkenes, as well as di-, per-, and monofluoroalkyl bromides, and exhibits a good functional group tolerance even toward unprotected polar functionalities. Mechanistic investigations reveal a portfolio strategy involving an initial atom transfer radical addition (ATRA) process followed by a remarkably tunable site-selective H−Br elimination, leading to either vinyl or contrathermodynamic allylic Heck-type products based on the presence of different external additives.