Mechanistic Study Of Iridium-Catalyzed Ketone ?-Alkylation With Unactivated Olefins

Directing group assisted C-H activation is currently the most commonly used method to activate specific C-H bonds.In this thesis,density functional theory calculations were performed to investigate the iridium-and rhodium-catalyzed intermolecular ketone?-alkylation with unactivated olefins via an enamide directing strategy.For iridium-catalyzed reaction,the computations show that Ir(III)intermediate was formed through an initial C-H oxidative addition.The subsequent C=C bond of propylene migratory insertion into the Ir-C bond/C-H reductive elimination led to the branched products.The calculations reproduced quite well the experimentally observed chemo-and regioselectivities.The origins of the chemoselectivity of the reaction taking place exclusively with the alkene C(sp~2)-H bond could be mainly due to the difference in the ring size of the forming metallacycles,and can be explained by the fact that the aromatic C(sp~2)-H oxidative addition to form five-and seven-membered metallacycles suffers from higher strain energy than the alkene C(sp~2)-H oxidative addition to form a six-membered metallacycle.The regioselectivity of the reaction is mainly due to the electronic and steric effect of methyl group,which makes the insertion of 2,1-migration into Ir-C bond much more favored than that of 1,2-migration into Ir-C bond,leading to the experimentally observed excellent branched selectivity.The relativistic effect in Rh being weaker than that in Ir results in the catalytic activity of the Rh catalyst much less efficient compared to the Ir catalyst and mechanistic change of rhodium-catalyzed?-alkylation reaction to the migratory insertion into the Rh-H bond/C-C reductive elimination to generate the linear product.