Mechanistic understanding of Rh-catalyzed N-sulfonylaldimine insertion into aryl C-H bonds

A detailed investigation is presented to understand the catalytic pathway of our recently reported Rh(III)-catalyzed N-tosylaldimine insertion into aryl C-H bonds. Herein, the key intermediates were isolated and determined by X-ray crystallography of their single crystals. The kinetic characterization of each factor in this catalytic reaction was conducted. The studies indicate that N-tosyl aldimine insertion into the C-Rh bonds rather than C-H bond activation or protonolysis is the rate-determining step. These mechanistic insights have significant implications for the development of a more efficient catalytic reaction system to realize the addition of C-H bonds to normal aldehydes and ketones, to achieve sp(3) C-H bond activation, and to implement asymmetric catalysis in the near future.