Rhodium-Catalyzed Denitrogenative Transannulation of N-Sulfonyl-1,2,3-triazoles with Glycals Giving Pyrroline-Fused N-Glycosides.

Described here is a selective synthesis of 2,3-dihydropyrrole-fused N-glycosides through rhodium-catalyzed denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles with glycals. A series of pyrroline-fused N-glycosides are afforded in moderate to excellent yields with exclusive regioselectivity and stereoselectivity. Functional application of such a resultant product by oxidative addition and epoxidation is also explored. Notably, the treatment of a pyrroline-fused N-glycoside (3a) with TMSOTf efficiently leads to an interesting unexpected C-nucleoside (9) via a TMSOTf-inducing ring opening/acetyl migration/ring closing reaction sequence.