Rh(II)-Catalyzed Highly Diastereoselective Cascade Transannulation of N-Sulfonyl-1,2,3-triazoles and Vinyl Benzoxazinanones.

An efficient, Rh(II)-catalyzed, denitrogenative reaction of 4-vinyl benzoxazinanones with N-sulfonyl-1,2,3-triazoles has been developed for the synthesis of structurally diverse tricyclic 2-imidazolones in moderate to good yields with excellent diastereoselectivities. The reaction consists of the sequential formation of four new bonds: two C-N and two C-O bonds in a cascade fashion. The reaction works under operationally simple conditions and also represents the first catalytic nondecarboxylative cyclization of vinyl benzoxazinanones with triazoles.