Enantioselective Palladium-Catalyzed Carbene Insertion into the N-H Bonds of Aromatic Heterocycles.

C3-substituted indoles and carbazoles react with aaryl-alpha-diazoesters under palladium catalysis to form alpha-(N-indolyl)-alpha-arylesters and alpha-(N-carbazolyl)-alpha-arylesters. The products result from insertion of a palladium-carbene ligand into the N-H bond of the aromatic N-heterocycles. Enantio-selection was achieved using a chiral bis(oxazoline) ligand, in many cases with high enantioselectivity (up to 99% ee). The method was applied to synthesize the core of a bioactive carbazole derivative in a concise manner.