Copper-Catalyzed Enantioselective Markovnikov Protoboration of α-Olefins Enabled by a Buttressed N-Heterocyclic Carbene Ligand

Abstract

Reported is a highly enantioselective copper-catalyzed Markovnikov protoboration of unactivated terminal alkenes. A variety of simple and abundant feedstock α-olefins bearing a diverse array of functional groups and heterocyclic substituents can be used as substrates, and the reaction proceeds under mild reaction conditions at ambient temperature to provide expedient access to enantioenriched alkylboronic esters in good regioselectivity and with excellent enantiocontrol. Critical to the success of the protocol was the development and application of a novel, sterically hindered N-heterocyclic carbene, (R,R,R,R)-ANIPE, as the ligand for copper.

Keywords: N-heterocyclic carbenes; asymmetric synthesis; copper; ligand design; olefins.