Synthesis of Hindered Phenolic Esters over Ion-Exchange Resins

The esterification of 3,5-di-tert-butyl-4-hydroxybenzoic acid with 1-hexadecanol over a series of ion-exchange resins was investigated, in which resin D072 exhibited excellent catalytic performance. The influence of water on the reaction was also investigated, and it was found that water could improve the selectivity and increase the yield of the target product. Treatment of resins with aqueous sodium hydroxide could improve the selectivity of the target product but remarkably decreased the conversion of 3,5-di-tert-butyl-4-hydroxybenzoic acid. This result indicated that strong Brønsted acid sites played an important role in the reaction. Furthermore, D072 was efficiently recycled four runs by simple treatment with mineral acid. Finally, a series of hindered phenolic esters were successfully synthesized under the optimal reaction conditions. Therefore, a simple and versatile method for the synthesis of hindered phenolic esters has been established over ion-exchange resins and the target products were obtained in good yields.