Regioselective π-extension of indoles with rhodium enalcarbenoids - synthesis of substituted carbazolesElectronic supplementary information (ESI) available: Experimental details, characterization and NMR spectral data. CCDC 1005568-1005570. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4ob01693a

An efficient Rh( ii ) carboxylate and Brønsted acid catalyzed direct π-extension of indoles to 4-substituted carbazoles is developed. The reaction involves a regioselective C-3 functionalization of indole by a rhodium enalcarbenoid and a Brønsted acid assisted cyclocondensation. In addition a twofold regioselective π-extension of pyrroles to 4,8-disubstituted carbazoles has also been developed. The utility of the methodology was demonstrated with the synthesis of analogues of an hepatitis C virus replication inhibitor and a secreted phospholipase A2 (sPLA2) inhibitor. An efficient Rh( ii ) carboxylate and Brønsted acid catalyzed direct π-extension of indoles to 4-substituted carbazoles is developed.