Synthesis of Isosorbide Esters from Sorbitol with Heterogeneous Catalysts

Sulfonic solids of different nature (alkyl, aryl and perfluoroalkyl sulfonic) are able to catalyze the dehydration of sorbitol under solvent free conditions at moderate temperature (130 degrees C) under vacuum and the esterification of isosorbide with carboxylic acids, either acetic or octanoic acids. Yields around 80% of isosorbide can be obtained from sorbitol with only 1 mol% catalyst after 24 h. Yields of dicarboxylates from isosorbide were in the range of 70-80% for diacetate and up to 97% for dioctanoate. The two-step one-pot process from sorbitol is highly efficient for isosorbide diacetate (up to 71% yield), whereas the esterification with octanoic acid is more sensitive to the presence of by-products (up to 57% yield).