Crosslinked poly(ionic liquid) as high loaded dual acidic organocatalyst

A dual acidic heterogeneous organocatalyst was synthesized by copolymerization of acidic ionic liquid monomer (vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate [VSim][HSO4]) and ionic liquid crosslinker (1,4-butanediyl-3,3'-bis-l-vinyl imidazolium dihydrogen sulfate). The resulting ionic heterogeneous catalyst is shown to be an efficient dual acidic organocatalyst for synthesis of dihydropyrimidines using the Biginelli synthetic route under mild reaction conditions in high yields. Since monomers make the catalyst bed, crosslinked poly(ionic liquid) will have high loading level of acidic groups comparing to other heterogeneous acid catalysts. Despite of conventional heterogeneous ionic liquid catalysts, present poly(ionic liquid) catalyst shows good thermal stability and good reusability. The crosslinked poly(ionic liquid) organocatalyst represents a novel class of high loaded heterogeneous catalyst which are particularly attractive in green chemistry. (C) 2012 Elsevier B.V. All rights reserved.