Displacement of sulfur functions

Reactions of organomagnesium compounds with thioethers usually take other pathways, and uncatalysed reactions involving displacement of thiolate are rare. On the other hand, several examples of nickel(ii)-catalysed reactions have been described, and analogous reactions of selenoethers have also been reported, e.g. 

The nickel-catalysed reaction of organomagnesium compounds with dithioacetals, in which the initial substitution leads to elimination, giving a substituted alkene, is potentially useful [23, 24], as in the following procedure. Elimination of p-alkoxy or alkylthio groups from the 

It should be noted, however, that the regiochemistry of the elimination cannot always be completely controlled [27], and that replacement of both sulfur functions may occur, e.g. [28], 

These types of reactions have also been applied to orthothioesters [29] and a tetrathioorthocarbonate [30], e.g. [29], 

Reactions of organomagnesium compounds with sulfoxides often result in ligand exchange [31], and may be complicated by a- or ortho metallation. However, in some cases, notably with 2-pyridyl aryl sulfoxides, reactions with arylmagnesium halides give useful yields of products from displacement of the aryl sulfoxido group [32, 33], e.g. [32] 

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