DFT study on the mechanism of selectively oxidative C(sp2)–H/C(sp3)–H cross-coupling of benzamides with amides by nickel catalyst: Oxidant-controlled regioselectivity

Abstract

The mechanisms of Ni-catalyzed selective oxidation of C(sp2)-H/C(sp3)-H cross-coupling of benzamide with amide are investigated using density functional theory (DFT) calculations. The calculations show that the reaction involves the sequential steps of NH activation, CH activation, oxidative addition of free radicals, reductive elimination, protonation, and oxidation. Based on the DFT calculations, the CH cleavage occurs via the concerted metalation-deprotonation (CMD) mechanism. Moreover, we have also conducted a detailed study on the mechanisms of the formation of two different free radicals, α-C(sp3) carbon radical RA and free radical RB that is adjacent to nitrogen atom. These theoretical insights into the oxidant-controlled mechanisms may inspire future discovery of oxidants for coupling reactions.