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.