Atom economical green synthesis of chloromethyl-1,3-dioxolanes from epichlorohydrin using supported heteropolyacids

Abstract

Bioglycerol can be valorized to different products, among which epichlorohydrin is an important intermediate used in a variety of industries. Chloromethyl-1,3-dioxolane is one of the important pharmaceutical intermediates, which is obtained by cycloaddition reactions of epichlorohydrin with ketones. Chloromethyldioxolane derivatives are used as tranquilizers, as plasticizers, as a new class of adrenoceptor antagonists, and also as potential monomers for polymerization and ploycondensation. In the present work, study of the cycloaddition reaction of epichlorohydrin with acetone using 20% (w/w) cesium-substituted dodecatungstophosporic acid (Cs_2.5H_0.5PW₁₂O₄₀, Cs-DTP) supported on K10 clay has been done. Different catalysts such as K10 clay, 20% (w/w) dodecatungstophosporic acid (DTP)/K10, 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/K10, and 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀/HMS were synthesized, and their efficacies were studied. The 20% (w/w) Cs_2.5H_0.5PW₁₂O₄₀ (Cs-DTP)/K10 clay was found to be highly active. The catalyst was well characterized by different techniques, viz., FTIR, XRD, SEM, and NH₃-TPD. A temperature of 70 °C and mole ratio of epichlorohydrin to acetone of 1:8 should be used. The reaction is 100% atom economical and green. The catalyst is reusable. A kinetic model for the cycloaddition reaction has been developed. The reaction mechanism is of the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type with very weak adsorption of both reactants in the absence of any diffusion resistance. The energy of activation is 15.77 kcal/mol.