Prins condensation for synthesis of nopol from β-pinene and paraformaldehyde on novel Fe–Zn double metal cyanide solid acid catalyst

The present work describes the novel application of Fe–Zn double metal cyanide complexes as solid acid catalysts for the synthesis of nopol from β-pinene. The series of Fe–Zn double metal cyanide complexes were prepared from aqueous solutions of ZnCl2 and K4Fe(CN)6·3H2O in the presence of tert-butanol, iso-butanol and n-butanol (complexing agent) and tri-block copolymer EO20PO70EO20 (average molecular weight, 5800; co-complexing agent). The catalysts prepared were characterized by X-ray diffraction, thermal analysis, diffuse reflectance UV–vis and FT-IR spectroscopy. All the catalysts were found to be active solid acid catalyst for Prins condensation reaction between paraformaldehyde and β-pinene in the synthesis of nopol. Coordinatively unsaturated Zn2+ ions in the framework of Fe–Zn double metal cyanide complexes are found to be possible active sites.

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