An unprecedented benzannulation of oxindoles with enalcarbenoids: a regioselective approach to functionalized carbazoles

Abstract

A novel Rh(II)/Brønsted acid catalyzed tandem benzannulation of oxindoles with enaldiazo carbonyls led to the formation of valuable 1-hydroxy-2-acylcarbazoles. This reaction is proposed to involve a formal insertion of a rhodium enalcarbenoid into an oxindole sp² C–O bond, an oxa-Michael addition, Friedel–Crafts reaction and a semipinacol type 1,2-carbonyl migration.