Rhodium(III)-Catalyzed C(sp2)-H Chemoselective Annulation to O-Cyclized Isochromen-imines from Benzamides.

Through the development of ligands and reaction conditions, the Rh(III)-catalyzed selective annulation of benzamides with internal alkynes has been achieved to the formation of O-cyclized isochromen-imines. Various substituents are well-tolerated under mild reaction conditions. Density functional theory calculations indicate that silver carbonate could act as a Lewis acid to assist the ligand to improve the chemical selectivity of the reaction in a catalytic system.