Physically mixed catalytic system of amino and sulfo-functional porous organic polymers as efficiently synergistic co-catalysts for one-pot cascade reactions

Abstract

In this article, acid/base bi-functional polymeric materials were prepared using physically mixed porous poly(divinylbenzene-co-4-vinylbenzenesulfonic acid) (P(DVB-VBS)) with sulfonic acid groups and poly(divinylbenzene-co-4-vinylbenzyl amine) (P(DVB-VBA)) with amino groups, which were synthesized by solvothermal polymerization of crosslinker DVB with either phenyl 4-vinylbenzenesulfonate (PVBS) or 4-vinylbenzyl amine hydrochloride (VBAH) functional monomers together with subsequent hydrolyzation or alkaline treatment. The bi-functional polymeric materials were utilized as a synergistic catalytic system for one-pot cascade reactions including deacetalization–Henry condensation reaction, deacetalization–Knoevenagel condensation reaction and the transformation of 3,4-dihydropyran derivatives to α-ester cyclohexenone compounds. The crosslinked polymeric frameworks effectively isolated sulfonic acid and primary amine groups to ensure their roles as both acid and base catalyst simultaneously in a one-pot system. The hierarchical porosity of a physically mixed acid/base co-catalyst system provided the possibility for the multi-step transformation of more complex substrates.