Environmentally benign esterification and disproportionation using activation of acid anhydrides by molecular sieves...

Molecular sieves 3A (MS 3A) activate the carbonyl group of an acid anhydride to undergo esterification upon treatment with an alcohol under mild conditions without any detectable byproducts. This method can be applied to both aromatic and aliphatic anhydrides, obtaining their corresponding esters. Less nucleophilic phenol and carboxylic acids can be used as nucleophiles, leading to phenyl esters and mixed anhydrides, respectively. When Boc₂O was used as the anhydride, unsymmetrical carbonates and anhydrides were readily obtained. This method requires simple experimental manipulations in the absence of other additives, such as metal and acid catalysts. The used MS can be recovered using cylindrical filter paper, which facilitates its reuse without any treatment up to eight times, with over 90% yields.