Theoretical insights into Rh-catalyzed hydroamidation: Mechanism and chemoselectivity

Rh-catalyzed hydroamidation of unactivated alkenes were investigated by a density functional theory study. The catalytic cycle proceeds through β-H elimination, alkene addition, CO2 extrusion, nitrene migratory insertion and protodemetalation. CO2 extrusion is the rate-determining step for the overall reaction. More importantly, the hydroamidation-to-aziridination and hydroamidation-to-amidation chemoselectivities have been investigated and the origins of impossibilities of CC bond aziridination and C(sp2/sp3)H bond amidations have been elucidated. The Rh-nitrene group is more inclined to insert RhC bond rather than CC and C(sp2/sp3)H bonds to form the new CN bond of hydroamidation products. These calculation results provide valuable information for further selective synthesis of amides.