Sulfonium salts cross-coupling

Sulfonium salts have been prepared on insoluble supports by S-alkylation of thioethers (Figure 8.2) only as synthetic intermediates. These compounds can be used to alkylate carboxylates [168] and halides [65], or as electrophiles for the Suzuki cross-coupling reaction (see Entry 7, Table 3.48 [169]). Sulfonium salts are also C,H-acidic, and can be used as intermediates for the synthesis of epoxides (Entry 7, Table 15.1 [170]). 

For Pd-catalyzed cross-coupling reactions the organopalladium complex is generated from an organic electrophile RX and a Pd(0) complex in the presence of a carbon nucleophile. Not only organic halides but also sulfonium salts [38], iodonium salts [39], diazonium salts [40], or thiol esters (to yield acylpalladium complexes) [41] can be used as electrophiles. With allylic electrophiles (allyl halides, esters, or carbonates, or strained allylic ethers and related compounds) Pd-i73-jt-allyl complexes are formed these react as soft, electrophilic allylating reagents. 

In addition to the -SAr groups, the scope of cross-coupling reactions was extended to -S02Ar and -S-COOMe groups. The reaction of sulfonium acid salts with... 

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