Highly para-Selective C−H Alkylation of Benzene Derivatives with 2,2,2-Trifluoroethyl α-Aryl-α-Diazoesters

Compared to the most popular directing-group-assisted strategy, the “undirected” strategy for C−H bond functionalization represents a more flexible but more challenging approach. Reported herein is a gold-catalyzed highly site-selective C(sp²)−H alkylation of unactivated arenes with 2,2,2-trifluoroethyl α-aryl-α-diazoesters. This protocol demonstrates that high site-selective C−H bond functionalization can be achieved without the assistance of a directing group. In this transformation, both the gold catalyst and trifluoroethyl group on the ester of the diazo compound play vital roles for achieving the chemo- and regioselectivity.