One-Pot Transannulation of N-Sulfonyl-1,2,3-triazoles to Dihydro-β-carbolines and Dihydroisoquinolines via Rhodium-Catalyzed C-H Insertion-cum-Base-Mediated Aza-Michael Reaction.

Efficient one-pot rhodium-catalyzed and base-mediated transannulation of N-sulfonyl-1,2,3-triazoles with a Michael acceptor-tethered indole derivative have been achieved for the synthesis of dihydro-β-carboline derivatives. The present methodology involves an efficient rhodium-catalyzed insertion of azavinyl carbenes to C3-H bond of indole followed by base-mediated intramolecular aza-Michael reaction. The optimized conditions tolerate various functional groups and afford the diverse dihydro-β-carbolines in good yield. The method was successfully extended to the synthesis of dihydroisoquinolines employing Michael acceptor-tethered aniline derivatives. The potential of the developed method was demonstrated through one-pot cascade synthesis of dihydro-β-carbolines from alkyne and their conversion to vital carboline derivatives.