Catalytic Asymmetric Four-Component Reaction for the Rapid Construction of 3,3-Disubstituted 3-Indol-3'-yloxindoles.

A Rh(II)/chiral phosphoric acid cocatalyzed four-component reaction of indoles, 3-diazooxindoles, arylamines, and ethyl glyoxylate is developed, offering an extremely efficient strategy for the construction of 3,3-disubstituted 3-indol-3'-yloxindoles with excellent diastereoselectivities and high to excellent enantioselectivities. This transformation is proposed to proceed through a Mannich-type trapping of the zwitterionic intermediate generated from a metal carbene and an indole with an iminoester derived from an arylamine and a glyoxylate.