An efficient synthesis of 2,3-dideoxy-α,β-unsaturated carbohydrate enals by mixed Lewis acid (HfCl4 and ZnI2) catalyzed hydration of glycals

A new, efficient method has been developed for converting acyl-, arylalkyl- and alkyl-protected glycals into corresponding 2,3-dideoxy-α,β-unsaturated carbohydrate enals utilizing the in situ generated push–pull effect resulting from the synergistic combination of HfCl4 and ZnI2 in catalytic amounts. This new procedure eliminates the use of highly toxic Hg2+ ions and acidic conditions (0.01–0.02 N H2SO4), besides radically shortening the reaction time.