Pd-Catalyzed de Novo Assembly of Diversely Substituted Indole-Fused Polyheterocycles.

Here we describe a facile, tandem synthetic route for indolo[3,2-c]quinolinones, a class of natural alkaloid analogues of high biological significance. A Ugi four-component reaction with indole-2-carboxylic acid and an aniline followed by a Pd-catalyzed cyclization yields tetracyclic indoloquinolines in good to moderate yields. Commercially available building blocks yield highly diverse analogues in just two simple steps.