Acid-catalyzed Oxidation of Levulinate Derivatives to Succinates under Mild Conditions

Levulinate derivatives are an attractive platform for the production of renewable chemicals. Here we report on the oxidation of methyl levulinate into dimethyl succinate with peroxides under mild conditions using BrOnsted and Lewis acid catalysts. Selectivities to succinate and acetate derivatives of approximately 60 and 40%, respectively, were obtained with strong BrOnsted acids in methanol. Although the molecular structure (i.e., carbon-chain length and branching around the CO group) and the oxidant type affect the product distribution, solvent choice has the strongest impact on changing the location of oxygen insertion into the carbon backbone. Specifically, switching the solvent from methanol to heptane resulted in a decrease in the succinate/acetate ratio from 1.6 to 0.3. In contrast to BrOnsted acids, we demonstrate that the nature of the metal cation is responsible for changing the reaction selectivity of water-tolerant Lewis acidic triflate salts.