β-Cyclodextrin based polyurethane as eco-friendly polymeric phase transfer catalyst in nucleophilic substitution reactions of benzyl halides in water: An efficient route to synthesis of benzyl thiocyanates and acetates

Abstract

β-Cyclodextrin, a cyclic sugar with a hydrophobic central cavity that has extensive applications in the pharmaceutical, food and biomedical industries, was polymerized with hexamethylene diisocyanate in dry dimethylformamide. Water-insoluble β-cyclodextrin-polyurethane (β-CDPU) polymer has demonstrated the ability to catalyst the nucleophilic substitution reaction of benzyl halides with thiocyanate and acetate anions in water. No evidence for the formation of by-product, for example isothiocyanate, was observed and the products were obtained in pure form without further purification. The polymeric phase transfer catalyst, easily recovered by simple filtration, shows no appreciable loss of activity when recycled several times.