An umpolung sulfoxide reagent for use as a functionalized benzyl carbanion equivalent

N-Methyl ortho-carbamoylaryl benzyl sulfoxides can be used as synthetic equivalents for a-hydroxy, a-chloro, and a-acetammido benzyl carbanions by means of a two-step sequence involving highly diastereoselective a-C-alkylation with alkyl halides followed by displacement of the sulfinyl residue (which can be recovered and recycled) by a hydroxyl, a chlorine or an acetamido, respectively, under nonoxidative Pummerer conditions. The scope and limits of the method, including a stereoselective version of the reaction, as well as the mechanism of the process are discussed in detail.