Theoretical study on Rh(III)-catalyzed reaction of allenylsilanes with N-methoxybenzamides

The reaction mechanism of the Rh(III)-catalyzed C−H functionalization of N-methoxybenzamides with allenes have been computationally investigated by employing density functional theory (DFT) calculations. Two reaction mechanisms have been calculated. The reaction mechanism involving β‒H elimination first followed by protonation is calculated to be preferred to the one in which protonation occurs first followed by β‒H elimination. The catalytic cycle consists of seven major processes: N‒H deprotonation, C‒H activation, alkene insertion, β‒H elimination and, N‒H bond-forming reductive elimination, MeOH elimination, and N‒H bond-forming oxidative addition. The C(sp2)‒H activation is the rate-determining transition state with a free energy barrier of 19.5 kcal/mol. The electronic effect could account for the observed regioselectivity. In addition, the reaction mechanisms for the formation of other side products have been calculated and compared.