An unusual hydrogen addition of indolo-2,3-quinodimethanes to dimethylindoles in the presence of 1,3-azoles

Indolo-2,3-quinodimethane generated in situ from bis-(bromomethyl)indole with NaI/DMF at 70C was expected to undergo cycloaddition with 1,3-azoles to give carboline derivatives, which form the backbone of many indole alkaloids. However, the reaction did not give the anticipated product but proceeded via hydrogen addition to exocyclic methylene groups, furnishing dimethylindoles in good yields.