Catalyst-Controlled Product Selectivity for Cycloaddition of Bis(indol-3-yl)-allenes to Fused Spiroindolines and Mechanistic Studies.

Abstract

A catalyst-controlled cycloaddition reaction of bis(indol-3-yl)-allenes gives rise to two different types of fused spiroindolines bearing a spiro quaternary stereocenter, affording a range of fused spiroindolines in good yields. The asymmetric desymmetrization of bis(indol-3-yl)-allenes with very high regioselectivities and excellent enantioselectivities has been successfully established and catalyzed by (R)-DTBM-Segphos(AuNTf2)2. Mechanistic studies through control experiments and DFT calculations provide plausible mechanistic proposals.