Access to Benzo[a]carbazoles and Indeno[1,2-c]quinolines by a Gold(I)-Catalyzed Tunable Domino Cyclization of Difunctional 1,2-Diphenylethynes.

The cyclization order of the difunctional 1,2-diphenylethynes was precisely tuned under the catalysis of gold by changing the nitrogen substitution of the substrates, leading to the facile preparation of benzo[a]carbazole and indeno[1,2-c]quinoline derivatives. The mechanisms of these domino cyclizations were probed by control experiments, and an insight into the selectivity of the cyclization was gained by density functional theory (DFT) calculations. This research represents a unified and common method to access benzo[a]carbazoles and indeno[1,2-c]quinolines.