Regio- and Diastereoselective Indium-Catalyzed Conia-Ene Reaction of ortho-Alkynyl Diketopiperazines to Access Fused Diketopiperazinoindolines.

An efficient synthesis of diketopiperazinoindolines through an indium-catalyzed intramolecular 5-exo-dig cyclization of ortho-alkynyl diketopiperazines has been reported. The formation of diketopiperazinoindolines proceeds via a regio- and diastereoselective Conia-ene reaction. This synthetic method opens a new door for easy access to functionalized fused diketopiperazinoindolines in high to excellent yields with exclusive Z diastereoselectivity.