Properties and Reactions of Sulphoxides

Properties and Reactions of Sulphoxides.—Simple reactions resulting in the reduction of sulphoxides to sulphides, reported recently, concern SnCU-HCl, NaHSOj (SO2 is ineffective), RCS2H, and MeCOCl. During the reaction of butyl methyl sulphoxide with L-cysteine, ( -)-2 ner-captopropionic acid, or other optically active thiols, the (-HR)-sulphoxide accumulates, indicating that the (S)-enantiomer is reduced faster by the thiol.  

Bregant, K. Balenovic, and V. Polak, Bull. Sci. Cons. Acad. Sci. Arts. R.S.F. Yugoslav., 

Regioselectivity in acetic-anhydride-induced Ptimmerer reactions of steroidal sulpho ddes is determined by steric factors with axial 6/3-alkylsul-phinyl-5a-cholestanes, only 6-alkylthiocholest-5-enes are formed, representing acetoxylation of the more highly substituted a-carbon atom, RSO-CH2X RS(OAc)CH2X RS=CHX RSCH(OAc)X. 

Resolution of dl-methyl p-tolyl sulphoxide to the extent of 2.25 0.25% enrichment of the (R)-(+)-enantiomer is achieved by irradiation in the presence of the chiral sensitizer (R)-(+)-N-acetyi-l-(l-naphthyl)ethylamine during 50h. The process is one of equilibration rather than selective destruction of the (S)-enantiomer. Racemization parameters for sulphox-ides in comparison with sulphimides and sulphonium ions and comparisons with analogous species from elements near S in the Periodic Table 

Oxidation of sulphoxides to sulphones is readily accomplished using familiar oxidants a novel observation, that iV-oxides of tertiary and heterocyclic amines are reduced by sulphoxides (R sN—O + R aSO R sN—O—SR a—O -  

R gN + R aSOa), may be as valuable in amine chemistry as in organosulphur chemistry. Its value is enhanced since the intermediate adduct may be captured by a nucleophile, thus giving a Sulphinate as an oxidation product of the sulphoxide.  

Mehmet and J. B. Hyne, Preprints, Div. Petrol. Chem., Amer. Chem. Soc., 1974, 19, 187. M. Nojima, T. Nagata, and N. Tokura, Bull. Chem. Soc. Japan, 1975, 48, 1343. 

Tetraco-ordinate sulphur(iv) species are increasingly coming to mind when hypothetical reaction mechanistic schemes are being devised. The formation of di(/7-tolyl) sulphide, /7,/ -bitolyl, and w,/7 -bitolyl from di(/7-tolyl) sulphoxide and /)-tolyl-lithium suggests a 3-toluyne intermediate, formed from the sulphur(iv) precursor TolgSO Li+. The (5)-( - )-sulphoxide (44), on treatment with 

Janczewski and S. Dacka, Roczniki Chem., 1974, 48, 753 M. Janczewski and B. Dziur-zynska, ibid., p. 409. 

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