p-Sulfonic acid calix[n]arenes as organocatalysts for the transesterification reaction of Passiflora seed oil

Abstract

The catalytic activity of p-sulfonic acid calix[4]arene was studied in the transesterification reactions of Passiflora seed oil with methanol or ethanol. Calix[n]arenes are highly versatile organocatalysts and conversion rates >98 % were obtained for the transformation of Passiflora seed oil to its methyl or ethyl esters after 5 h of reaction in the presence of p-sulfonic acid calix[4]arene (3.52 mol % in ethanol; 5.28 mol % in methanol). Moreover, the organocatalyst was recovered and reused in two subsequent cycles without a significant decrease in the activity or selectivity. The use of a non-corrosive and reusable organocatalyst is the positive aspect of this process.