To further understand stereoselection in the alkylation of sulfenate anions, a protected cysteinesulfenate was generated in THF solution at low temperature. Introduction of a reactive alkylating agent brings about a cysteinyl sulfoxide in 51-75% yield, with diastereomeric ratios at the sulfinyl group ranging from 83:17 to 95:5. An internally complexed lithium counterion is proposed to account for the stereoselectivity.
An increasing number of reactions of sulfenic acid anions are being demonstrated in the literature. As such, mild, general and reliable means for the generation of sulfenates are due. In the current paper, an addition/elimination of 2-sulfinyl acrylates using various nucleophiles is demonstrated and evaluated as a protocol for alkane- and arenesulfenate generation. Cyclohexanethiolate, methoxide and n-butyllithum each exhibit some merit for the reaction, and the thiolate is established as a mild, selective and effective reagent to release sulfenates from 2-sulfinyl acrylates. The stereospecificity of the addition/elimination of each nucleophile is recognized, and an explanation for the specificity is offered for thiolate and methoxide.
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