Organometallic compounds with disulfides

If the normal addition procedure is applied, the initial product may be deprotonated by the original organometallic compound and the newly generated intermediate will react with the disulfide ... 

These subsequent reactions can be avoided by applying inversed-order addition, i.e., by adding the organometallic compound to the electrophilic reagent, the latter preferably used in excess. In this way excellent yields are obtained in the reactions of bis(methylthio)methyllithium with dimethyl disulfide and trimethylchlorosilane (compare Ref. [2]). 

The desulfurization of organosulfur compounds with trivalent organophospho-rus compounds has been studied for more than four decades [118]. A variety of such reagents has been used to convert disulfides to monosulfides, trisulfides to disulfides or monosulfides, /3-keto sulfides to ketones, and sulfenimides to amines. They have also been used to remove sulfur from thioethers, thiols, and organometallic dithiocarboxylates, and oxygen from sulfones. 

In sharp contrast to the thioketenes, carbon disulfide S=C=S, carbon oxysulfide 0=C=S and the isothiocyanates R-N=C=S are stable compounds although highly reactive, and are widely used in organosulfur chemistry. Some of their reactions with organometallics have been mentioned previously (see Section 2.8.3). 

The 2-sulfonyloxaziridine (57) is a more selective oxidant than peracids. The reagent has been employed in the oxidation of sulfides to sulfoxides, disulfides to thiolsulfinates, selenides to selenoxides, thiols to sulfenic acids, organometallic reagents to alcohols and phenols, ketone and ester enolates to a-hydroxycarbonyl compounds (equation 31)41. The oxidation of chiral amide enolates gives optically active a-hydroxy carboxylic acids with 93-99% enantiomeric excess42. 

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