Theoretical Exploration of Rh/Cu Cooperative Catalysis in C–H Allylation of Benzamide with 1,3-Diene

Abstract

Density functional theory has been employed to study the mechanism of the Rh/Cu cooperative catalyzed C−H allylation of benzamide with 1,3-diene. The plausible catalytic cycles encompass C−H activation, diene insertion, oxidative addition for catalyst recovery, and ene reaction for the formation of product. Our calculations conclusively support that the complex between Cp*Rh(OAc)Cl and Cu(OAc) 2 (DMA), denoted as CAT-A, is the most likely active catalyst, facilitating the formation of the Rh(η 3 -allyl) intermediate easily. Following this, the anion [Cu(OAc) 2 (Cl)(DMA)] − , which is dissociated from the Rh coordination site in the first step, returns to the Rh center, providing an OAc group to the Rh coordination center. Subsequently, the Cl atom in [Cu(OAc) 2 (Cl)-(DMA)] − enters the Rh coordination sphere to facilitate catalyst regeneration and separate the precursor of final product 3a. This precursor undergoes an ene reaction with Cu(OAc) 2 (DMA), resulting in the formation of product 3a. We propose a Rh III −Rh IV −Rh III catalytic cycle to elucidate the mechanism governing the titled reaction. Additionally, we explored the subsequent reactions of the generated product 3a and the substituent effects, providing a comprehensive explanation for the experimental observed yields.