Selective Ammonolysis of Bioderived Esters for Biobased Amide Synthesis

Amidation is an important reaction for bioderived platform molecules, which can be upgraded for use in applications such as polymers. However, fundamental understanding of the reaction especially in the presence of multiple groups is still lacking. In this study, the amidation of dimethyl fumarate, maleate, and succinate through ester ammonolysis was examined. The reaction networks and significant side reactions, such as conjugate addition and ring closing, were determined. A preliminary kinetic comparison among additional C₄ and C₆ esters showed a significant correlation between molecular structure and ammonolysis reactivity. Esters with a C=C double bond in the molecule backbone were found to have higher ammonolysis reactivity. To improve the selectivity to unsaturated amides rather than byproducts, the effects of thermal conditions and additives in dimethyl fumarate ammonolysis were examined. Lower temperature and decreasing methoxide ion concentration in the solution relative to the base case conditions increased the fumaramide selectivity from 67.1 to 90.6%.