A facile synthesis of multi-functionalized benzothiazonine was achieved by rhodium-catalyzed denitrogenative annulation of 1-sulfonyl-1,2,3-triazole and thiochromone. In view of excellent atom economy, broad substrate scope and easily availability of starting...

An efficient rhodium(II)-catalyzed [4+3] cyclization reaction of 1-sulfonyl-1,2-3-triazoles and indoles was developed. Azepino [5,4,3cd]indoles, which are widely distributed in ergot alkaloids with various biological activities, could be obtained in good to excellent yields. In addition, the total synthesis of (±)-aurantioclavine was completed in four steps from the known compound 1a adopting this [4+3] cyclization as a key step.

Formal 1,3-migration of hydroxy and acyloxy groups initiated by α-imino rhodium carbene was achieved, and the following selective annulations of the corresponding zwitterions could efficiently afford azepane derivatives. Benefiting from a timesaving procedure as well as a good functional group tolerance, this unique migration−annulation protocol could provide an efficient tool for synthesizing seven-membered N-heterocycles. The plausible mechanism is discussed.