Catalytic Conversion of a Chitin-Derived Sugar Alcohol to an Amide-Containing Isosorbide Analog

Chitin is an attractive feedstock for the production of organonitrogen compounds. The hydrolysis of chitin produces N-acetylglucosamine, and subsequent hydrogenation gives a sugar alcohol, 2-acetamide-2-deoxysorbitol (ADS). However, the transformation of these compounds to useful chemicals has remained a challenge due to the complicated reactivity of the N-containing molecules. Here, we report the catalytic conversion of ADS to 2-acetamide-2-deoxyisosorbide (ADI), which is a potential platform chemical for the production of organonitrogen compounds such as polymers. This study shows that ADS hardly undergoes the dehydration condensation to ADI under the reaction conditions used for a widely studied dehydration reaction of a similar sugar alcohol, sorbitol. Instead, a large amount of a super strong acid, CF3SO3H, under vacuum conditions is required to produce ADI from ADS. Density functional theory calculations indicate that acetamide groups in the substrate trap acid protons, and therefore, a large amount of strong acid is necessary to compensate for this neutralization effect. Moreover, the decrease in pressure facilitates water removal and inhibits deacetylation side reactions.