Preparation and application of 4′-carboxybenzo-15-crown-5, a drift-type crown ether phase transfer catalyst

Abstract

A new "drift-type" crown ether phase transfer catalyst, 4′-carboxybenzo-15-crown-5 adsorbed on poly(styrene/divinylbenzene)-NR2 resin, was synthesized and applied to catalyze the oxidation of benzhydrol with NaMNO4 as an oxidant. Before the reaction, the drift-type crown ether catalyst was adsorbed on the resin with ion-pair (resin-NR2H+−O2C-monobenzo-15-crown-5) formation. During the reaction period the crown ether catalyst was released from the resin into the reaction solution as a homogeneous catalyst by adjusting the acidity of the solution to 10−1 M HCl to destroy the ion pair between the catalyst and the resin. After the reaction, the crown ether catalyst could be readsorbed on the resin by adjusting the concentration of HCl to 10−5 M and could be readily recovered by filtration. The catalyst, 4′-carboxybenzo- 15-crown-5, was found to be a more effective catalyst than other crown ethers, such as 15-crown-5, 18-crown-6, monobenzo-15-crown-5, and dibenzo-18-crown-5.