Asymmetric Cycloisomerization of o-Alkenyl-N-Methylanilines to Indolines by Iridium-Catalyzed C(sp(3))-H Addition to Carbon-Carbon Double Bonds

摘要

Highly enantioselective cycloisomerization of Nmethylanilines, bearing o-alkenyl groups, into indolines is established. An iridium catalyst bearing a bidentate chiral diphosphine effectively promotes the intramolecular addition of the C(sp(3))-H bond across a carbon-carbon double bond in a highly enantioselective fashion. The reaction gives indolines bearing a quaternary stereogenic carbon center at the 3position. The reaction mechanism involves rate-determining oxidative addition of the N-methyl C-H bond, followed by intramolecular carboiridation and subsequent reductive elimination.