Palladium-Catalyzed Imidoylative Cyclization of Tryptophan-Derived Isocyanides: Access to β-Carbolines.

A palladium-catalyzed imidoylative cyclization of ethyl-3-(1H-indol-3-yl)-2-isocyanopropanoates, derived from readily available tryptophan, to afford β-carboline derivatives has been developed. The reaction proceeds smoothly under mild conditions through sequential isocyanide insertion, intramolecular C-H imidoylation, and aerobic dehydrogenative aromatization with a decent substrate scope. This method provides a general approach for the synthesis of molecules containing the β-carboline fragment.