Asymmetric Diels-Alder reaction of 2-methyl-3-indolylmethanols via in situ generation of o-quinodimethanes.

An asymmetric Diels-Alder reaction of 2-methyl-3-indolylmethanols and α,β-unsaturated aldehydes has been developed that relies on in situ generation of active indole-2,3-quinodimethane intermediates under mild acidic conditions and uses a secondary chiral amine as iminium activation catalyst. An array of highly enantioenriched tetrahydrocarbazoles have been efficiently produced in fair to good yields.