Subtle stereochemical and electronic effects in iridium-catalyzed isomerization of C-allyl glycosides.

Stereoselective isomerization of C-allyl glycosides into (E)-C-vinyl glycosides or (Z)-exo-glycals was carried out in the presence of the cationic iridium(I) catalyst [(Ph2MeP)2Ir(cod)PF6]. The products of the isomerization were affected by the relative 1,2-stereochemical relationships and by the nature of the protecting groups. These effects are discussed along with a plausible reaction mechanism.