The Relative Reactivity of Thioethers and Sulfoxides toward Oxygen Transfer Reagents: The Oxidation of Thianthrene 5-Oxide and Related Compounds by MoO5HMPT

Abstract

The oxidation of thianthrene 5-oxide (SSO) by M0O5HMPT has been studied in 1,2-dichloroethane at 40 °C. Under conditions of excess substrate over the oxidant, three products are formed, i.e., two isomeric cis and trans bissulfoxides (SOSO) and sulfide-sulfone (SSO2) which quantitatively account for the active oxygen of M0O5HMPT consumed. The rates of appearance of the products at different reactant concentrations have been measured. A second-order rate law has been established. The ratios of the rate constants and of the final concentrations of the three products, i.e., &2(cis-S0S0):&2(fr'cms-S0S0):&2(SS02) = l.0:4.0:1.0; [ds-S0S0L:[£rcms-S0S0U:[SS02]~= 1.0:4.5:1.2, are in good agreement. The frans-SOSO-forming reaction is only 4-fold faster than that leading to SSO2. cis-SOSO and SSO2 are produced at almost the same rate. Evidence is presented that all the oxidation reactions are electrophilic processes taking place via a simple bimolecular mechanism not involving the coordination of the substrate to the metal. The low selectivity is due to the scarce reactivity of the thioether center in thianthrene 5-oxide. The investigation of the oxidative behavior of structurally related compounds reveals that such a low reactivity results from a combination of stereoelectronic effects. These findings provide a rationale to some ambiguous results obtained when thianthrene 5-oxide is employed as a mechanistic probe of the electronic character of the oxidants.

Mechanism of oxidation of aryl methyl sulfoxides with sodium hypochlorite catalyzed by (salen)MnIII complexes

“…By contrast, sulfoxides are oxidized to sulfones by both electrophiles and nucleophiles [3][4][5]. With many oxidants it has been established that the ratio of reactivity, k s /k so , is very large and the nucleophilic reactivity of thioether is more affected by structural effects than that of sulfoxides [2,[4][5][6]. We have initiated a systematic study on the oxygenation reactions of the organic sulfides and sulfoxides with oxometal complexes by taking Cr, Mn and Ru as metal ions.…”

Novel aspects of carbonyl oxide chemistry

“…It has also been pointed out that thianthrene 5-oxide (20) is not always an ideal probe because the reactivities of sulfide and sulfoxide groups in 20 are considerably modified by the electronic effect between them through the -system or transannular interaction. 61 In this respect, earlier results obtained from intermolecularly competitive trapping experiments seem to be more reliable.…”

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“…Solv-Materials: All chemicals are commercially available, except for the ation is again confirmed to play a major role in the ob-following: PhSOtBu and tBu 2 SO were prepared by oxidation of served effect. the corresponding sulfides with acidic H 2 O 2 /EtOH; [44] PhStBu was…”