Asymmetric Synthesis of Chiral Seven-Membered NHCs, Their Transition-Metal Complexes and Application in Asymmetric ­Catalysis

A series of new chiral seven-membered NHCs were synthesized via Ru-catalyzed asymmetric hydrogenation reactions as the key step. Transition metal such as Rh, Ir and Au can coordinate to the developed NHCs. The crystal structures of the chiral seven-membered NHCs and their transition-metal complexes show a nonplanar framework with torsional twist. Furthermore, the chiral NHCs were applied in asymmetric hydrosilylation reactions, and the corresponding product was obtained with >95% yield and up to 83% ee.