Influence of structural differences and acidic properties of phosphotungstic acids on their catalytic performance for acylation of pyruvate ester to α-acyloxyacrylate ester

Various heteropolyacids, including Keggin-type (H3PW12O40), Dawson-type (H6P2W18O62) and Preyssler-type (H14[NaP5W30O110]) phosphotungstic acids, were examined as catalysts for acylation of ethyl pyruvate with acetic anhydride to synthesize ethyl α-acetoxyacrylate in liquid phase. This compound is one of candidate monomers for bio-based polymers bearing high thermal durability and transparency. Catalytic performances correlated to the acid strength, the proton number and the stability of the phosphotungstic acids. Notably, performance of Preyssler-type phosphotungstic acid per unit mole of catalyst was higher than that of Keggin-type.