Organocatalyzed enantioselective formal [4 + 2] cycloaddition of 2,3-disubstituted indole and methyl vinyl ketone.

A formal [4 + 2] cycloaddition of 2,3-disubstituted indoles with vinyl methyl ketone was realized in the presence of a catalytic amount of quinine-derived primary amine and pentafluorobenzoic acid. This method provides bridged-ring indoline scaffolds containing two quaternary carbon centers with excellent yields and enantioselectivity (up to 98% yield and 98% ee).