Adaptations of the Andersen procedure

Enantiomerically pure methyl phenyl sulfoxide and methyl p-tolyl sulfoxide in diethyl ether or dimethoxyethane were reacted with alkyllithium reagents. The exchange reactions were found to proceed with inversion of configuration at sulfur. The yields are somewhat variable, but Johnson s work did indicate that special procedures are necessary for the generation of hthium a-sulfinyl carbanions for use in other synthetic purposes for example, Johnson recommended the use of lithium dialkylamides as bases, since nucleophilic substitution can occur either on the neutral molecule or on the carbanion with alkyllithium reagents. 

Another drawback of the classical Andersen procedure is that it allows for isolation of diastereoisomerically pure (5)-(-)-menthyl p-toluene sulhnate in a poor 30% yield. An early improvement pioneered by Hebrandson employed the known racemization of sulfoxides by HCl in an epimerization/equilibration technique to increase the yield of (5)-(-)-menthyl p-toluene sulhnate to 90% from the initial (R) and (5) diastereoisomeric mixture [14]. This adaptation has been described in detail by Solladie and the proposed epimerization/equilibration is 

Both enantiomers of Whitesell s chiral auxiliary (8) are available by enzymatic resolution of commercially available racemic rrarw-2-phenylcyclohexanol [20,21], allowing ready and equal access to dialkyl, alkyl aryl and diaryl sulfoxides of high optical purity and with either absolute configuration. 

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