Unsaturated carbohydrates. Part 20. Direct conversion of phenyl 1-thiohexoside esters into phenyl 1-thiohex-1-enopyranosid-3-ulose esters

Abstract

Treatment of phenyl 1-thiohexoside esters with an excess of N-bromosuccinimide in refluxing carbon tetrachloride and under bright visible light caused them to be converted directly into the corresponding phenyl 1-thiohex-1-enopyranosid-3-ulose esters. Whereas the reactions with benzoates proceeded smoothly and in high yield, acetates gave mixtures of products which contained minor proportions of 2-monobromoacetyl analogues of the main enones. Glycosides with equatorial phenylthio-groups reacted appreciably faster than did their anomers.