Harnessing dipolar microenvironment engineering of PTSA for alkenylation of indole in butyl acetate

Abstract

The thiophene sulfone-functionalized hyper-crosslinked polymer (HCP) was prepared, characterized, and used as an additive to regulate the catalytic activity of p-toluenesulfonic acid (PTSA) in the alkenylation of indole with carbonyl compounds. A kinetic study demonstrated that addition of the above HCP not only accelerated the reaction but also improved its selectivity. The absorption of PTSA resulted in a local increase in the concentration of the catalyst and the polarity of HCP, determined by Nile red, accounted for the enhancement of catalytic activity. Together with providing a green protocol for the alkenylation of indole, supported by green chemistry metric evaluation, this work paved the way for extending the application of Brønsted acid in catalysis.