Selective Oxidation of Thioether Mustard (HD) Analogs bytert-Butylhydroperoxide Catalyzed by H5PV2Mo10O40Supported on Porous Carbon Materials

Abstract

The polyoxometalate H5PV2Mo10O40(1) supported on porous carbons forms selective and recoverable heterogeneous catalysts for the rapid room temperature oxidation of thioether mustard (HD) analogs. Both selectivities (95 to 99% for sulfoxide) and rates (∼20%) vary with the carbon support at parity of all other parameters. A 99% selectivity for the sulfoxide product, even at 75% conversion of the thioether substrate, is seen for the most selective system, 10 wt% 1 on Rohm and Haas Ambersorb (1/Ambersorb). Washing for 125 h in the solvent for catalysis, toluene, results in no significant loss in catalytic activity and a recovery and reusability study at high turnover also indicates that the catalysts are very stable. The polyoxometalate/carbon catalysts can be reactivated between uses by heating to ∼80°C. The oxidation of tetrahydrothiophene (THT) to THTO bytert-butylhydroperoxide (TBHP) catalyzed by 1/Ambersorb is first order in substrate and oxidant and proportional to the concentration of active sites on the 1/Ambersorb. The activation parameters for the process are ΔH‡=11.4±0.05 kcal/mol and ΔS‡=−38.8±0.22 cal/K mol.