Allylic nucleophilic substitution reactions in sugars. III. Uncatalysed displacements in hexamethylphosphoramide

Abstract

The uncatalysed displacement of allylic benzoyloxy groups with azide in unsaturated sugars has been studied by using hexamethylphosphoramide as solvent. Tri-O-benzoylglycals and 4,6-O-benzylidene-3-O-benzoylglycals were investigated. The former gave rise to mixtures of 3-azido-glycals and hex-2-enopyranosyl azides, whereas the latter gave only glycal products. The mechanism of the reactions is considered in some detail. Displacements on allylic trimethylsilyl ethers were not successful.