Palladium-and nickel-catalyzed cross-coupling reactions

8 Palladium- and nickel-catalyzed cross-coupling reactions 

A dominant theme since the mid-1980s in the chemistry of five-membered rings with one heretoatom has been the application of transition metal catalysis, especially the use of Pd or Ni as catalysts for bond formation (for review see (92S413)). 

The reaction of heterocyclic lithium derivatives with organic halides to form a C-C bond has been discussed in Section 3.3.3.8.2. This cannot, however, be extended to aryl, alkenyl or heteroaryl halides in which the halogen is attached to an sp2 carbon. Such cross-coupling can be successfully achieved by nickel or palladium-catalyzed reaction of the unsaturated organohalide with a suitable heterocyclic metal derivative. The metal is usually zinc, magnesium, boron or tin occasionally lithium, mercury, copper, and silicon derivatives of thiophene have also found application in such reactions. In addition to this type, the Pd-catalyzed reaction of halogenated heterocycles with suitable alkenes and alkynes, usually referred to as the Heck reaction, is also discussed in this section. 

2-Thienylmagnesium or zinc derivatives can be coupled with vinyl halides, bromo- or iodo-benzene, or ethynyl bromide under Ni or Pd catalysis (Equation 8). The reaction can be extended to the synthesis of (3-styrylthiophene in this case the double-bond configuration is retained in the product. 

An interesting application of acetylene coupling is the preparation of the per(acetylenated)thiophene (Equation 9) (88JOC2489). 

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PALLADIUM- AND NICKEL-CATALYZED CROSS-COUPLING REACTIONS... 

General Considerations and Mechanism In 1977, Fauvarque/Jutand reported the first palladium- and nickel-catalyzed cross-coupling reaction of aiyl halides with a zinc ester enolate the Reformatsky reagent (Scheme 19.29) [26b, 32]. When PdCljCPPhj) and NiCljjPPhj) are used... 

Palladium and Nickel-Catalyzed Cross-Coupling Reactions... 

Palladium- or nickel-catalyzed cross-coupling reactions with organozincs and related organometals... 

Nagishi, E. and Liu, F., Palladium- or Nickel-catalyzed Cross-coupling with Organo-metals Containing Zinc, Magnesium, Aluminium and Zirconium , in Metal-catalyzed Cross-coupling Reactions, Wiley-VCH, Weinheim, 1998, pp. 1-47. 

Introduction of the silylmethyl group into organic halides, tosylates, and epoxides is achieved by nickel, palladium-, or copper-catalyzed cross-coupling reactions. 

The history of the discoveries and developments of the palladium-catalyzed crosscoupling reactions has been documented in many reviews, book chapters, and monographs. Palladium-catalyzed processes can be traced back to Nickel-catalyzed cross-coupling reactions of organomagnesium derivatives reported in 1972 by Tamao, Sumitani, and Kumada as well as by Corriu and Masse. Some groups led by Murahashi et Fauvarque, and Sekiya and Ishikawa independently... 

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