Brønsted acid on a USY zeolite boosts the direct alkenylation of 2-methylquinoline with aldehydes

Abstract

Development of an environmentally friendly catalyst system is a highly attractive strategy for modern organic synthesis. In this work, the direct alkenylation of 2-methylquinoline and benzaldehyde was achieved over a USY zeolite in the absence of any additive. The abundant accessible Brønsted acid sites promoted the adsorption and activation of 2-methylquinoline and benzaldehyde, leading to the formation of highly reactive intermediates of 2-methylene-1,2-dihydroquinoline and protonated benzaldehyde, respectively, through electrostatic interactions of the protic hydrogens at the Brønsted acid sites with N or O atoms in the substrates. The activity of the USY zeolite outperformed that of mesoporous HBeta and HZSM-5 zeolites with fewer accessible Brønsted acid sites.