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.