Thioether-Directed Selective C4 C-H Alkenylation of Indoles under Rhodium Catalysis.

A thioether-directed Rh(III)-catalyzed C4 selective C-H alkenylation of indoles via the formation of 5-membered metallacycle intermediates is reported. This protocol allows a wide functional group compatibility and broad substrate scope. The directing group can be readily removed or transformed into other functional groups after the C-H functionalization event. The catalytic method is also applicable to related heterocyclic systems involving benzo[ b]thiophene and benzo[ b]furan scaffolds.