Brønsted Acid Catalyzed [3+2]‐Cycloaddition of 2‐Vinylindoles with In Situ Generated 2‐Methide‐2<i>H</i>‐indoles: Highly Enantioselective Synthesis of Pyrrolo[1,2‐<i>a</i>]indoles

Abstract

Pyrrolo[1,2-a]indoles are privileged structural elements of many natural products and pharmaceuticals. An efficient one-step process for their highly diastereo- and enantioselective synthesis, comprising a direct [3+2]-cycloaddition, has been developed. A chiral BINOL-derived phosphoric acid catalyzes the reaction of in situ-generated 2-methide-2H-indoles with 2-vinylindoles, furnishing the target products incorporating three contiguous stereogenic centers as single diastereoisomers and with excellent yields and enantioselectivities.