Acid Catalyzed Competitive Esterification and Ketalization of Levulinic Acid with 1,2 and 1,3-Diols: The Effect of Heterogeneous and Homogeneous Catalysts

Condensation reactions of levulinic acid (LA) with 1,2-ethanediol (1,2-ED), 1,2-propanediol (1,2-PD), and 1,3-propanediol (1,3-PD) were studied using Amberlyst-15 as well as p-toluenesulfonic acid catalysts in benzene under Dean-Stark conditions. In Amberlyst-15 catalyzed reactions the products are ketals and ketal-esters, whereas p-toluenesulfonic acid catalyzed reactions produce esters and ketal-esters as products. In p-toluenesulfonic acid catalyzed reactions with 1,2-ED and 1,3-PD, LA monoester product is formed as the major product after 180 min in 75 and 97 % yields respectively. Unlike the previously reported acid catalyzed ketalization of ethyl levulinate with diols, combined ketalization-esterification of LA with diols is a complex process.