Abstract
AbstractLinear end‐blocked and crosslinked siloxane copolymers containing dimethylsiloxyl and methyl(1‐oxypyridin‐3‐yl)siloxyl groups were prepared and characterized thermally (TGA) and spectroscopically. These hydrophobic copolymers were found to be highly effective transacylation catalysts in the synthesis of carboxylic anhydrides and the hydrolysis of diphenyl phosphoro‐chloridate (DPPC) under phase‐transfer catalysis (PTC) conditions, i.e. CH2Cl2‐H2O suspension. The insolubility of the copolymers in water and the preference of the intermediate, polymeric 1‐acyloxypyridinium ion for the more lipophilic carboxylate ion in anhydride formation suggest that the reaction occurs at the CH2Cl2‐H2O interphase. The rapid rate of hydrolysis of DPPC under PTC conditions and in water provides evidence for initial hydrophobic binding or association of the hydrophobic catalyst prior to reaction with a water‐insoluble substrate.
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