Disclosed herein is the design of an unprecedented electrophilic rhodium enalcarbenoid which results from rhodium(II)-catalyzed decomposition of a new class of enaldiazo compounds. The synthetic utility of these enalcarbenoids has been successfully demonstrated in the first transition-metal-catalyzed [4+2] benzannulation of pyrroles, thus leading to substituted indoles. The new benzannulation has been applied to the efficient synthesis of the natural product leiocarpone as well as a potent adipocyte fatty-acid binding protein inhibitor.

A novel rhodium catalyzed pyridannulation of 3-substituted indoles with diazoenals furnished privileged pyrido[1,2-a]indoles. The reaction is proposed to involve a [4 + 2]-annulation of the diacceptor rhodium enalcarbenoid via C-2 functionalization of the indole. The utility of the methodology was demonstrated with a short synthesis of the tetrahydropyrido[1,2-a]indole core, present in a large number of biologically important polycyclic indole alkaloids.

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 sp(2) C-O bond, an oxa-Michael addition, Friedel-Crafts reaction and a semipinacol type 1,2-carbonyl migration.