ONIOM study on reaction mechanism of desymmetrization of meso anhydrides catalyzed by bifunctional Bronsted Acid/Base organocatalyst

초록

The reaction between anhydride and methanol catalyzed by bifunctional Bronsted acid/base organocatalyst was investigated theoretically by ONIOM method. Calculations indicate that the energy barrier is quite high without catalyst, i.e. 30.8 kcal/mol. In the presence of catalyst, the reaction proceeds through a 2-step mechanism with the energy barrier of 19.0 kcal/mol and 0.9 kcal/mol. The pyridine moiety works as a Bronsted base to activate methanol substrate, and the N atom attached to P atom works as a Bronsted acid to activate anhydride by hydrogen bonding.