Isocanthine Synthesis via Rh(III)-Catalyzed Intramolecular C–H Functionalization

An efficient synthesis of substituted isocanthines has been achieved using an intramolecular Rh­(III)-catalyzed C–H functionalization of alkyne-tethered indoles in the presence of catalytic tris­(acetonitrile)­pentamethylcyclopentadienylrhodium­(III) hexafluoroantimonate and stoichiometric copper­(II) acetate. This isocanthine synthesis tolerates a variety of electronically diverse 5- or 6-substituted indoles with N-tethered alkyne coupling partners and can also be extended to pyrrole derivatives for the synthesis of annulated 5-azaindoles.