Palladium‐Catalysed Norbornene‐Mediated Regioselective Direct C−H Glycosylation of Free (N−H) Pyrrole Derivatives.

A palladium‐catalyzed norbornene‐mediated regioselective direct C−H glycosylation of free N−H pyrrole and electron‐deficient pyrrole derivatives has been developed. The reaction involves the use of a PdII catalyst and norbornene as a transpositional co‐catalyst, in which a pyrrole‐ and norbornyl‐fused palladaheterocycle forms as the key intermediate. The 2‐substituted pyrroles, and other 2,3‐disubstituted pyrroles underwent the selective C5 glycosylation. This reaction is compatible with various types of glycosyl chlorides including D‐mannose, L‐rhamnose, D‐mannofuranose, and D‐ribofuranose. The viability of this strategy is showed by gram‐scale, various synthetic transformation and functionalization. [ABSTRACT FROM AUTHOR]