Non-coordinating-Anion-Directed Reversal of Activation Site: Selective C-H Bond Activation of N-Aryl Rings.

Abstract

An Rh-catalyzed selective C-H bond activation of diaryl-substituted anilides is described. In an attempt to achieve C-H activation of C-aryl rings, we unexpectedly obtained an N-aryl ring product under non-coordinating anion conditions, whereas the C-aryl ring product was obtained in the absence of a non-coordinating anion. This methodology has proved to be an excellent means of tuning and adjusting selective C-H bond activation of C-aryl and N-aryl rings. The approach has been rationalized by mechanistic studies and theoretical calculations. In addition, it has been found and verified that the catalytic activity of the rhodium catalyst is obviously improved by non-coordinating anions, which provides an efficient strategy for obtaining a highly chemoselective catalyst. Mechanistic experiments also unequivocally ruled out the possibility of a so-called "silver effect" in this transformation involving silver.