Metal-mediated coupling reactions

Many of the modern vinylallene syntheses involve metal-mediated coupling reactions, as shown by several typical examples summarized in Scheme 5.11. The treatment of the propargyl carbonate 83 with the alkenylborane 84 in the presence of a palladium catalyst furnished the substituted vinylallene 85 in excellent yield (Scheme 5.11) [28],... 

To expand the diversity of their libraries Brill et al.16 also modified various heterocycles by alkylation, acylation, or metal-mediated coupling reaction prior to resin capture. A remaining chloro substituent was still available for nucleophilic displacement or a palladium-mediated coupling reaction with anilines, phenols, and boronic acids on solid phase [see Fig. 10 for the preparation of purine derivative (62)]. 

The use of hypervalent iodine reagents in carbon-carbon bond forming reactions is summarized with particular emphasis on applications in organic synthesis. The most important recent methods involve the radical decarboxylative alkylation of organic substrates with [bis(acyloxy)iodo]arenes, spirocyclization of para- and ortho-substituted phenols, the intramolecular oxidative coupling of phenol ethers, and the reactions of iodonium salts and ylides. A significant recent research activity is centered in the area of the transition metal-mediated coupling reactions of the alkenyl-, aryl-, and alkynyliodonium salts. 

Numerous reactions of alkenyl(phenyl)iodonium salts leading to the formation of new C-C bond have been reported in the literature. The most important and synthetically useful reactions include the generation and subsequent cyclization of alkylidenecarbenes, alkenylation of carbon substrates via nucleophilic vinylic substitution, and transition metal-mediated coupling reactions. 

It can be anticipated that these areas of synthetic application will continue to attract significant research activity in the future. The increasing use of the transition metal-mediated coupling reactions of iodonium salts may add a new dimension to the field of polyvalent iodine chemistry. 

Kanomata N, Suzuki J, Kubota H, Nishimura K, Enomoto T (2009) Synthesis of planar-chiral bridged bipyridines and terpyridines by metal-mediated coupling reactions of pyridinophanes. Tetrahedron Lett 50 2740-2743... 

More elaborate coupling reactions see Organic Synthesis Using Metal-mediated Coupling Reactions) include the... 

Complexes of the type [Cp Rh(R)(/4-CH2)]2 have been studied to probe details of the coupling of alkyl and methylene groups that could be relevant to mechanisms for the Fischer-Tropsch process (see Organic Synthesis Using Metal-mediated Coupling Reactions) Reaction... 

Cp Rh(MeCN)(/r-CH2)]2 +, both methylene units couple with two alkyne molecules see Organic Synthesis Using Metal-mediated Coupling Reactions) to form (146). ... 

A considerable number of reactions of CpRh(/x-CO)(/x- ) ) -F3CC=CCF3)RhCp have been reported which illustrates the diversity of products that can be obtained in transition metal alkyne chemistry see Organic Synthesis Using Metal-mediated Coupling Reactions). Reaction of this complex with dimethyldiazomethane forms a mixtme of (147) and (148), and on recrystallization (148) converts to (149) by... 

Organic Synthesis Using Metal-mediated Coupling Reactions... 

ORGANIC SYNTHESIS USING METAL-MEDIATED COUPLING REACTIONS... 

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