Transition metal intermediates

C. W. Bird, Transition Metal Intermediates in Organic Synthesis, Logos Press, London, UK, 1968. 

Secondary bromides and tosylates react with inversion of stereochemistry, as in the classical SN2 substitution reaction.24 Alkyl iodides, however, lead to racemized product. Aryl and alkenyl halides are reactive, even though the direct displacement mechanism is not feasible. For these halides, the overall mechanism probably consists of two steps an oxidative addition to the metal, after which the oxidation state of the copper is +3, followed by combination of two of the groups from the copper. This process, which is very common for transition metal intermediates, is called reductive elimination. The [R 2Cu] species is linear and the oxidative addition takes place perpendicular to this moiety, generating a T-shaped structure. The reductive elimination occurs between adjacent R and R groups, accounting for the absence of R — R coupling product. 

In view of the extensive and fruitful results described above, redox reactions of small ring compounds provide a variety of versatile synthetic methods. In particular, transition metal-induced redox reactions play an important role in this area. Transition metal intermediates such as metallacycles, carbene complexes, 71-allyl complexes, transition metal enolates are involved, allowing further transformations, for example, insertion of olefins and carbon monoxide. Two-electron- and one-electron-mediated transformations are complementary to each other although the latter radical reactions have been less thoroughly investigated. 

For reviews, see Collman Hegedus Norton Finke Principles and Applications of Organotransition Metal Chemistry. Universily Science Books Mill Valley. CA, 1987, pp. 768-775 Baird, in Patai The Chemistry of Functional Groups, Supplement B, pt. 2 Wiley New York, 1979, pp. 825-857 Tsuji, in Wender Pino Organic Syntheses Via Metal Carbonyls, vol. 2 Wiley New York, 1977, pp. 595-654 Tsuji Ohno Synthesis 1969, 157-169 Bird Transition Metal Intermediates in Organic Synthesis Academic Press New York. 1967, pp. 239-247. 

Synthesis of Heterocyclic Compounds via Transition Metal Intermediates C. W. Bird, J. Organomet. Chem., 1973, 47, 281-309. 

Early general reviews in this area (a) C. W. Bird, Transition Metal Intermediates in Organic Synthesis, Academic Press, New York, 1967, chap. 8 (b) W. Httbel, in Organic Synthesis via Metal Carbonyls , ed. I. 

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