Achiral Cp*Rh(III)/Chiral Lewis Base Cooperative Catalysis for Enantioselective Cyclization via C–H Activation

An
enantioselective [4+3] cyclization via C­(sp2)–H
activation with a cooperative catalytic system consisting of a Cp*Rh­(III)
complex and a chiral Lewis base is described. An α,β-unsaturated
acyl ammonium intermediate is generated from a chiral isochalcogenurea
catalyst and an acyl fluoride reacts with a metallacycle generated
from the Cp*Rh catalyst and a benzylamine derivative. This cooperative
catalytic system gives a variety of benzolactams in good yields with
excellent enantioselectivities (up to 99:1 er). The results demonstrated
that chiral Lewis base catalysis is a powerful tool for controlling
the enantioselectivity of transition metal-catalyzed C–H functionalizations.