Cross-coupling aryl hahdes, palladium-catalyzed

The palladium-catalyzed arylation and alkenylation of terminal alkynes with aryl or alkenyl hahdes in presence of a copper(l) co-catalyst is called Sonogashira reaction. In the same way as in the other cross-coupling reactions described before, it is possible to immobihze the alkyne or the aromatic bromides, iodides or triflates on sohd supports (Scheme 3.15). 

Suzuki couphng, the palladium-catalyzed cross-coupling of aryl or vinyl hahdes with organoboronates, is employed widely in organic synthesis. The reaction is most often carried out in an organic solvent (benzene) in the presence of a base [228]. Because of the reasonable stabihty of boronic acids and esters towards hydrolysis, Suzuki couphng can also be carried out in aqueous media. An extensive study of the reaction has shown that similar results are obtained in aqueous and non-aqueous systems [229]. 

Pentacoordinated silicate TASF, one of the best activators of organosilicon compounds in the Pd-catalyzed cross-coupUng reaction as we have seen, is found to be involved in the coupling reaction with aryl hahdes in the absence of other organosilanes to give methylated arenes (Scheme 1A)S Recently, DeShong and co-workers also reported that tetrabutylammonium triphenyldifluorosilicate, another pentacoordinated silicate, is applicable for the phenylation of allyl benzoates and aryl haUdes in the presence of a palladium catalyst. 

Also in 1977, Kosugi, Migita and coworkers reported on the use of organotin compounds for the palladium-catalyzed cross-couplings of aryl [89] and acyl hahdes [90]. The allylation of haloarenes and the arylation of acyl hahdes displayed again a remarkable wide substrate scope (Scheme 1.26) [91]. 

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