Cross coupling reactions arylzinc halides

The cross-coupling of organozinc compounds has been accomplished using a number of metal enolate complexes, namely Rh(acac)(H2C=CH2)2 (6) , Co(acac)3 (30) °, Ni(acac)2 (47) , Li(acac) (107) and Cr(acac)3 (108) . For instance, complex 47 proved to be an extremely effective catalyst system for the Negishi cross-coupling of arylzinc halides (109) with aryl (110), heteroaryl and alkenyl halides, triflates and nonaflates to give the corresponding biaryl compounds (111) (equation 30). The solvent played an important role in these reactions and optimal conditions were found with 8 1 mixtures of THF and A-ethylpyrrolidinone (nep). Only 0.05 mol% of the nickel complex... 

Scheme 4.61 Ni-catalyzed cross-coupling of arylzinc halides with a-bromoglycosides [207]. 4.5.1.3 Rhodium-Catalyzed Cross-Coupling Reactions...

The procedure described above is based on a paper reporting the Ni- or Pd-catalyzed reaction of arylzinc derivatives with aryl halides. The Ni- or Pd-catalyzed cross coupling reaction represents one of the most general and satisfactory routes to unsymmetrica1 biaryls. 

The Reformatsky reagents, i.e. zinc enolates of esters, undergo Ni catalysed cross-coupling with aryl halides.53 The Ni catalysed reaction of arylzincs with a-bromoacetates also permits a-arylation of esters54 (Scheme 11.13). However, a-alkenylation of enolates of ketones, aldehydes, and esters has been less satisfactory. Its further development is clearly desirable. Alternatively, a-alkenylation of a-iodoenones in conjunction with conjugate reduction discussed earlier should be considered. 

Nickel (0) reagents have been employed in the symmetrical coupling of aryl halides in sterically unencumbered cases. An efficient cross coupling reaction between an arylzinc halide and an ortho-iodoaryllmlne under mild conditions mediated by N1(0) has been reported. Thallium(III)... 

Scheme 4.37 Cross-coupling reactions of arylzinc halides catalyzed by palladium nanoparticles [141, 142].

Knochel reported that a combination of diethyl phosphite-DMAP and Ni(II) salts formed a very effective catalytic system for the cross-coupling reactions of arylzinc halides with aryl, heteroaryl, alkenyl bromides,... 

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