Since toluene gave low activity and poor sulfoxide selectivity and both t-BuOHand CH3CN led to inhibitory effects of the catalyst, the best choice seems CH2Cl2.The reaction was also carried out at 0 and -10 C using Si–VO(salen) as catalystand CH2Cl2 as solvent (entries 6 and 7). The decrease of the reaction temperatureresults in a decrease in the sulfide conversion with an increase in sulfoxideselectivity. The decrease in the sulfide conversion can be explained by the decreaseof the oxidation reaction rate at low reaction temperature with the parallel increasein sulfoxide selectivity by the decrease of the rate of the oxidation of sulfoxide tosulfone.
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