Sulfones, alkylation with Grignard reagents

The oxidative dimerization of the anion of methyl phenyl sulfone (from a Grignard reagent) in ethereal solution in the presence of cupric chloride in 5% yield has been reported47. Despite the reported48 poor stability of the a-sulfonyl C-centered radicals, Julia and coworkers49 provoked the dimerization (in 13 to 56% yields) of the lithiated carbanion of alkyl phenyl sulfones using cupric salts as oxidants. The best results are obtained with cupric triflates in THF-isobutyronitrile medium (56% yield for R = H). For allyl phenyl sulfones the coupling in the 3-3 mode is predominant. 

Synthetically useful alkylation of Grignard reagents can also be carried out with alkyl sulfonates and sulfates. 

Although an a-CF3 group is known to retard. S n2 reactions of carbon nucleophiles with alkyl sulfonates, it has now been found that y-trifluoromethylated allylic acetals undergo 5k2 -type reactions with Grignard reagents in presence of catalytic amounts of CuCN and TMS-C1 without formation of 5N2 products.110 This provides an alternative means of introducing a carbon nucleophile adjacent to a CF3 group. 

Reactions of organomagnesium compounds with dialkyl sulfates or alkyl sulfonates often give satisfactory yields of the products of displacement of sulfate or sulfonate. Side-reactions have been observed, but they can often be avoided for example, an excess of the sulfate or sulfonate should be used with Grignard reagents, as some is consumed by nucleophilic attack by halide ion [A]. The dialkyl sulfates are reactive, but hazardous. Toluenesulfonates (tosylates) are less reactive, but their reactions are catalysed by copper complexes the reactions of trifluoromethanesulfonates (triflates) are catalysed by nickel complexes. Reactions of Grignard reagents with secondary tosylates appear to follow an Sn2 mechanism, with inversion of configuration [43],... 

Tosylates and other sulfonates and sulfates couple with Grignard reagents, most often those prepared from aryl or benzylic halides.Alkyl sulfates and sulfonates generally make better substrates in reactions with Grignard reagents than the corresponding halides (10-57). The method is useful for primary and secondary R. 

Trost [76] reported the alkylation of allylic sulfones with Grignard reagents in the presence of a catalytic amount of CuCN in Et20, with high regio- and stereoselectivity in favor of the 8 2 product [Eq. (68)]. 

Coupling of alkyl halides with Na, supplanted by the coupling of alkyl halides or sulfonates with Grignard reagents or RLi in the presence of Cu(l) salts (see 1st edition). 

Synthetically useful alkylations of Grignard reagents also occur with alkyl sulfates and sulfonates ... 

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