Mechanistic exploration of Rh(III)-catalyzed C-H allylation of benzamides with allyl bromide

Abstract

The allylation of various benzamides under the catalysis of transition metal by the C-H activation is an attractive tool for the functionalization of aromatic system. One such reaction under the catalysis of Rh(III)-complex using allyl bromide as the allylating reagent was studied theoretically by employing density functional theory (DFT) to find out the plausible mechanistic path. The metal mediated allylation of various benzamides includes six steps – coordination of substrate with the catalyst, N-H metalation, C-H metalation, addition of allyl bromide, proton transfer and demetalation. Our calculations reveal that, the path involving the insertion of allyl bromide is energetically favorable compared to that of oxidative addition of allyl bromide. The effect of electron withdrawing and electron releasing substituents was also explained which nicely agrees with the experimental report.