Aryl sulfonates alkyl sulfoxides

Various diaUsyl, alkyl aryl and diaryl sulfoxides were readily oxidized to the corresponding sulfone in excellent yields under mild conditions at —30°C by 51. Interestingly,... 

A Cr(VI) sulfoxide complex has been postulated after interaction of [CrOjtClj] with MejSO (385), but the complex was uncharacterized as it was excessively unstable. It was observed that hydrolysis of the product led to the formation of dimethyl sulfone. The action of hydrogen peroxide on mesityl ferrocencyl sulfide in basic media yields both mesityl ferrocenyl sulfoxide (21%) and the corresponding sulfone (62%) via a reaction similar to the Smiles rearrangement (165). Catalytic air oxidation of sulfoxides by rhodium and iridium complexes has been observed. Rhodium(III) and iridium(III) chlorides are catalyst percursors for this reaction, but ruthenium(III), osmium(III), and palladium(II) chlorides are not (273). The metal complex and sulfoxide are dissolved in hot propan-2-ol/water (9 1) and the solution purged with air to achieve oxidation. The metal is recovered as a noncrystalline, but still catalytically active, material after reaction (272). The most active precursor was [IrHClj(S-Me2SO)3], and it was observed that alkyl sulfoxides oxidize more readily than aryl sulfoxides, while thioethers are not oxidized as complex formation occurs. 

Oxidation of Sulfoxides. Dialkyl, alkyl aryl, and diaryl sulfoxides are readily oxidized to sulfones in excellent yields under mild conditions (—30 °C) in MeCN by the peroxy intermediate (1). Oxidation of the unsaturated sulfoxide (11) was chemose-lective it furnished the sulfone (12) in 70% yield when reacted with (1) for 5 h. The double bond was not epoxidized. Similar chemoselective epoxidation has been carried out with only one other reagent (potassium hydrogen persulfate). ... 

An improved route has been described for the synthesis of 5 -5-aryl (or alkyl)-5 -thionucleosides,7 and it has been shown that the S-aryl compounds can be oxidized directly to 5 -fluoro-5 -thionucleoside derivatives using XeP2, in addition to the two-stage process involving oxidation to the sulfoxide and then treatment with DAST to induce a Pummerer-type process (see Vol. 22, p.212). Further oxidation of the a-fluorosulfides gives sulfones such as (9l).li3 Another reference to the use of such intermediates was discussed earlier, and there has been a further report on the preparation of 5 -(fluoromethylthio)adenosine and 5 -fluoro-5 -methylthioadenosine from the methylsulfinyl derivative and DAST (see Vol. 23, p.216)H - 5 -(Di- and trifluoromethylthio)adenosine have been prepared by alkylation with the appropriate chlorofluoromethane,H as have fluorinated 5-ethyl compounds of type (92),115.ll6 and the 5-(3-fluoropropyl)analogue.H9 The cyclic... 

Alkyl- and aryl-thiopyridazines are oxidized to sulfoxides, sulfones or sulfonic acids, depending on the reaction conditions. N- Oxidation can take place simultaneously. 

Colona and coworkers oxidized a variety of alkyl aryl and heterocyclic sulfides to the sulfoxides using t-butyl hydroperoxide and a catalytic amount of a complex (97) derived from a transition metal and the imines of L-amino acids. Of the metals (M = TiO, M0O2, VO, Cu, Co, Fe), titanium gave the highest e.e. (21%), but molybdenum was the most efficient catalyst. The sulfoxides were accompanied by considerable sulfone. ... 

Since the classical paper of Meyerson and coworkers in 1964 on the electron impact(EI) mass spectra of diaryl sulfones, only some more than one hundred original reports dealing with the mass spectra of sulfoxides and sulfones have been published. These data have been reviewed quite extensively, most recently by Khmel nitskii and Efremov in a review on The rearrangements in sulfoxides and sulfones induced by electron impact and by Porter. Several less comprehensive surveys have also been presented " . Since Reference 2 and to a lesser extent Reference 4 cover the El mass spectra of alkyl and aryl sulfoxides and sulfones up to 1974 fairly completely, and Reference 3 together with Reference 2 the mass spectra of heterocyclic sulfoxides and sulfones and their nitrogen-containing counterparts up to 1980, the present chapter will mainly concentrate on the most recent developments and some complementary material not described in the above-mentioned reviews. 

A further catalytic method for asymmetric sulfoxidation of aryl alkyl sulfides was reported by Adam s group, who utilized secondary hydroperoxides 16a, 161 and 191b as oxidants and asymmetric inductors (Scheme 114) . This titanium-catalyzed oxidation reaction by (S)-l-phenylethyl hydroperoxide 16a at —20°C in CCI4 afforded good to high enantiomeric excesses for methyl phenyl and p-tolyl alkyl sulfides ee up to 80%). Detailed mechanistic studies showed that the enantioselectivity of the sulfide oxidation results from a combination of a rather low asymmetric induction in the sulfoxidation ee <20%) followed by a kinetic resolution of the sulfoxide by further oxidation to the sulfone... 

Recently, Feng and co-workers reported an asymmetric sulfide oxidation" catalyzed by titanium complexes bearing HydrOx ligands, for example, 576 (Scheme 8.199). ° Enantioselectivities approached a level of synthetic utility for oxidation of aryl alkyl sulfides 632 although the yields of the sulfoxide 633 were poor due to overoxidation to the sulfone 634. The overoxidation is especially significant for reactions with high enantioselectivity. 

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