Benzylsulfonium salts

The benzylsulfonium salt is cleaved by hydrogenolysis (H2/Pd-C, MeOH) the 4-methoxybenzylsulfonium salt is cleaved by methylamine (100%). ... 

Campbell, S. J., Danvish, D. Asymmetric induction in the Sommelet rearrangement of chiral benzylsulfonium salts. Can. J. Chem. 1976, 54,... 

These rearrangements involve 1,2-shifts, and benzylsulfonium salts (24) behave like the corresponding benzyl sulfides in undergoing 1,2-shifts (Scheme 13) (Stevens (i) or Sommelet (ii) rearrangement). The direction of the rearrangement is sensitive to the experimental conditions, the Stevens pathway (i) being favoured at higher temperatures (Scheme 13). 

Solid-phase-bound benzylsulfonium salts can also undergo Pd(0)-mediated Suzuki couplings with boronic acids, leading to biarylmethane analogues (Scheme 43). 

Wagner and coworkers developed a traceless sulfur-based linker by applying the chemistry of benzylsulfonium salts [90]. Various benzyl bromides were attached to a thiol linker synthesized in four steps starting from Merrifield resin. Reaction of the resulting resin 96 with triethyloxonium tetrafluoroborate gave the solid supported sulfonium salt 97, which could be cleaved by reaction with boronic acids to afford biphenylmethyl derivatives 98 (Scheme 16.23). The alkylation can be regarded as an activation step and the linker as a safety-catch system. 

Monodebenzylation of the resin-attached Tyr(P03Bzl2) residue occurred under Boc deprotection conditions, but this side reaction did not preclude the synthesis of a 13-mer phosphotyrosyl peptide in good yield [98]. A major 5-benzylsulfonium salt by-product (66 to 83% of the crude material as determined from the HPLC chromatogram peaks) was identified... 

Using a phosphazene base, an optically active benzylsulfonium salt in the presence of ethyl acrylate provided an aryl-C moiety for the trans-2-arylcyclo-propanecarboxylate that is formed in 98-100% ee, while in the presence of acrolein, trans-2-aryl vinyl epoxide was the major product [50]. In contrast to the action of LDA on a pyrido[l,2-a]azepinone, Ps-t-Bu transforms this starting material to the enolate shown in Scheme 4 [51]. 

Benzylic Electrophiles. Benzylic chlorides and bromides are widely and readily available. They are therefore the reagents of choice in most cases. Less readily available benzylic iodides and fluorides have hardly been used. More recently, the use of benzylsulfonium salts in Pd- or Ni-catalyzed cross-couphng has been reported. 

Benzylic Electrophiles. BenzyUc chlorides and bromides are widely and readily available. They are therefore the reagents of choice in most cases. Less readily available benzylic iodides and fluorides have hardly been used. More recently, the use of benzylsulfonium salts in Pd- or Ni-catalyzed cross-coupling has been reported. These results are interesting in view of the fact that metal-mediated cleavage of the C—S bond has been shown to be an important biological process. It is not clear, however, in what cases this reaction would turn out to be the synthetic method of choice in preference to the corresponding reactions of benzyl chlorides and bromides. 

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