Sequential Sonogashira/intramolecular aminopalladation/cross-coupling of ortho-ethynyl-anilines catalyzed by a single palladium source: rapid access to 2,3-diarylindoles.

Abstract

We have developed a practical and efficient one-pot protocol for the synthesis of 2,3-diarylindoles via Pd-catalyzed bis-arylative cyclization of various o-ethynylanilines with aryl iodides. Mechanism studies showed that a Pd-catalyzed Sonogashira reaction took place firstly, giving an internal alkyne intermediate, which subsequently underwent intramolecular aminopalladation/cross-coupling to give access to 2,3-diarylindoles. The present methodology exhibits a broad substrate scope, producing various 2,3-diaryl indoles bearing two different aryl groups.