Reductive lithiation phenyl thioethers

Dialkoxymethyllithium compounds, for example 2-lithio-l,3-dioxan (311), are generated in situ as shown in equation 69, either by reductive lithiation of a phenyl thioether with a lithium arene or by transmetallation of the corresponding trialkylstannyl compound. Subsequent quenching with electrophiles leads to the usual alkylated or functionalized species ... 

In this context Cohen and coworkers have reported that a homoaflyllithium, generated by reductive lithiation (see below) from phenyl thioether 153, adds to a-methylstyrene and the resulting benzyllithium is able to cyclize, giving rise to sesquiterpene ( )-cuparene (Scheme 43)77. 

So far we have considered sulfur-containing carbanions obtained by metallation with appropriate bases of a to sulfur atom(s) acidic C-H bonds. For synthetic purposes this method has been by far the most used. Among the variety of other routes to such carbanions [203] we shall consider two methods which seem to be general and promising the reductive lithiation of phenyl thioethers and the thiophilie addition of organometallics to thiocarbonyl compounds (vide infra Section 4.1.2). 

It is assumed that this reaction involves a radical reductive process. Displayed below is the lithiation of an alkyl phenyl thioether with lithium naphthalene. 

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