Mechanism Study of Sugar and Sugar Alcohol Hydrogenolysis Using 1,3-Diol Model Compounds

摘要

Knowledge of the bond cleavage mechanism governing sugar and sugar alcohol hydrogenolysis is important to control of the selectivity of sugar and sugar alcohol hydrogenolysis. Previous work by others has resulted in the suggestion of a variety of mechanisms to explain the C-C cleavage in sugar and sugar alcohol hydrogenolysis, and has not provided any definitive evidence to elucidate either the C-C or C-O cleavage mechanism. In this work, we present a mechanism study carried out using 1,3-diol model compounds. Our experimental results indicate that cleavage of the C-C and C-O bonds in hydrogenolysis is through retro-aldolization and dehydration of a β-hydroxyl carbonyl, respectively. The structure of this β-hydroxyl carbonyl is already contained in an open-chain sugar molecule, and is generated from the sugar alcohol molecule by dehydrogenation. The intermediates from both C-C and C-O cleavage are subsequently hydrogenated to yield alcohols or polyols. This mechanism of sugar and sugar alcohol hydrogenolysis provides us a good background to understand factors that control the selectivity in sugar and sugar alcohol hydrogenolysis. Based on this understanding, a rational approach to control of the selectivity of sugar and sugar alcohol hydrogenolysis may be developed.