Selective oxidation of thioether mustard (HD) analogs by tert-butylhydroperoxide catalyzed by H5PV2Mo10O40 supported on porous carbon materials

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 (similar to 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 similar to 80 degrees C. The oxidation of tetrahydrothiophene (THT) to THTO by tert-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 Delta H double dagger = 11.4 +/- 0.05 kcal/mol and Delta S double dagger = -38.8 +/- 0.22 cal/K mol. (C) 1996 Academic Press, Inc.