Suzuki cross-coupling, alkyl electrophile

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]). 

The Suzuki cross-coupling methods described in Sect. 2.1 establish that palladium complexes that bear electron-rich trialkylphosphines of the appropriate size can serve as effective catalysts for reactions of alkyl electrophiles. Naturally, it was of interest to determine if non-phosphine ligands that are bulky and electron-rich can also furnish active catalysts. 

Lundin PM, Fu GC. Asymmetric Suzuki cross-couplings of activated secondary alkyl electrophiles arylations of racemic a-chloroamides. J. Am. Chem. Soc. 2010 132(32) 11027-11029. 

Han has comprehensively reviewed the use of nickel catalysts for the Suzuki-Miyaura cross-coupling reaction/ and found that the nickel mediated process can tolerate a broad range of aryl electrophiles, for example, sulfamates, carbamates, carboxylates, ethers, carbonates, phosphoramides, phosphonium salts, phosphates, phenols, and a broad range of alkyl substrates including both secondary and primary alkyl iodides, bromides, and chlorides. Many of these electrophiles have been found to be incompatible with traditional palladium catalysed processes. 

Suzuki Reaction Polymerizations. The Pd-catalyzed cross-coupling reaction of an organic electrophile and an organoboron compound in the presence of base has been extensively applied to the synthesis of polyphenylenes and related polymers. Well defined structures are obtained as a result of the regiospecificity of the Suzuki reaction (84) (230). The solubility of the polymers is commonly enhanced by the presence of alkyl or other types of substituents [for example see equations 85-87 (231,232,233 respectively and 254)]. 

The Suzuki-Miyaura reaction involves the palladium-catalyzed cross-coupling between organoboron compounds and halides. In most cases, aryl halides are used as electrophiles, but recent developments have broadened the scope and alkyl, alkenyl, and alkynyl halides can be successfully used as reaction partners. Among C—C coupling reactions, Suzuki-Miyaura reaction has become one of the most appealing because the reactants are air stable, nontoxic and tolerant of a variety of functional groups. 

Alternatively, boranes can be prepared in solution and then coupled with support-bound carbon electrophiles. The Suzuki coupling of alkylboranes, generated in situ from 9-BBN and alkenes, with brominated cross-linked polystyrene has been used to link substituted alkyl chains directly to the polymer (Entry 4, Table 5.3). Alkylboranes have also been used to alkylate polystyrene-bound aryl iodides (Entries 3 and 5, Table 5.3). 

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