Cross-coupling organic electrophiles

The late Professor J. K. Stille pioneered the development of a very effective and versatile palladium-mediated C-C bond forming method - the palladium-catalyzed cross-coupling of organic electrophiles with organostannanes.48 This process continues to enjoy much success in organic synthesis because it proceeds in high yields under mild reaction conditions and because it tolerates a... 

Transition metal catalysed cross-coupling reactions of organometalUc reagents containing Zn, Si, Mg, Sn or B with organic electrophiles in the presence of group 8-10 metals, notably Ni and Pd, are routinely the method of choice, both in academia and industry, for the preparation of C-0, C-S, C-H, C-N and C-C bonds [1]. 

Cross-coupling reactions resulting in C-C bond formation are normally classified according to the nature of the organometallic reagent and the organic electrophile. Scheme 6.4 summarises, broadly, the names and reaction partners of the most common of these transformations. 

Hydroboration of alkenes or alkynes followed by cross-coupling with organic electrophiles provides a straightforward method for the carbon-carbon bond formation (Scheme 1-19). The hydroboration of thioalkynes with catecholborane in the presence of a nickel or palladium catalyst yields P-(aLkylthio)-l-alkenylboronates (72a)... 

Several microwave-assisted protocols for soluble polymer-supported syntheses have been described. Among the first examples of so-called liquid-phase synthesis were aqueous Suzuki couplings. Schotten and coworkers presented the use of polyethylene glycol (PEG)-bound aryl halides and sulfonates in these palladium-catalyzed cross-couplings [70]. The authors demonstrated that no additional phase-transfer catalyst (PTC) is needed when the PEG-bound electrophiles are coupled with appropriate aryl boronic acids. The polymer-bound substrates were coupled with 1.2 equivalents of the boronic acids in water under short-term microwave irradiation in sealed vessels in a domestic microwave oven (Scheme 7.62). Work-up involved precipitation of the polymer-bound biaryl from a suitable organic solvent with diethyl ether. Water and insoluble impurities need to be removed prior to precipitation in order to achieve high recoveries of the products. 

For reviews of the Pd-catalyzed acylation and other cross-coupling reactions with a-hetero-substituted organic electrophiles, see ... 

Stille, J. K. The Palladium-Catalysed Cross-Coupling Reactions of Organo-tin Reagents with Organic Electrophiles, Angew. Chem. Int. Ed. Engl. 1986, 25, 508-524. 

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. 

Suzuki, A. Recent advances in the cross-coupling reactions of organoboron derivatives with organic electrophiles. J. Organomet. 

Palladium or nickel catalysed cross-coupling between unsaturated organozincs and unsaturated organic electrophiles... 

Palladium(0)-catalyzed cross-coupling reactions between organic electrophiles (usually vinyl or aryl halides or triflates) and a variety of organometallic reagents and boronic acids have become a popular... 

A. R. Martin, Y. Yang, Palladium Catalyzed Cross-Coupling Reactions of Organoboronic Acids with Organic Electrophiles "Acta Chem. Scand. 1993, 47, 221-230. 

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