Lewis acid Sn-Beta catalysts for the cycloaddition of isoprene and methyl acrylate: a greener route to bio-derived monomers

Abstract

Sn-Beta zeolite catalysts were unprecedently used for the Diels–Alder cycloaddition reaction between bio-available methyl acrylate and isoprene affording intermediates to bio-terephthalates. The use of the solid Lewis acid Sn-Beta allows for a greener process which is also more feasible for industrial implementation, when compared to the presently used homogeneous and often hazardous catalysts. Incorporating Sn^IV in the zeolite beta framework by dealumination followed by solid-state ion-exchange, resulted in an efficient cycloaddition catalyst with a selectivity favoring the para-adduct. Detailed characterization combined with computational DFT studies revealed that the tetrahedral framework Sn-sites in Sn-Beta zeolites are responsible for the superior catalytic activity and selectivity, which is maintained even at elevated temperatures.