A combined experimental–theoretical study on the lithiation/electrophilic quench reaction of benzylic position of (η5-tetramethylcyclohexadienyl)-Mn(CO)3

Abstract

An [(η⁶-1,2,4,5-tetramethylbenzene)Mn(CO)₃]⁺ BF₄⁻ complex treated with hydride gives a neutral (η⁵-1,2,4,5-tetramethylcyclohexadienyl)Mn(CO)₃ complex whose X-ray analysis is described. Functionalization of the latter complex at a “benzylic” position using a lithiation/electrophilic quench sequence affords two regioisomers of which the major one corresponds to the functionalization at the C9 carbon. Theoretical computations show that the regioselectivity of lithiation is governed by the stability of the carbanion and thus by its conjugation.