Electrophilic reactions organometallic compounds

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Pa]ladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natmal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

Netherton M, Fu GC (2005) Palladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Neumann H, see Jacobi von Wangelin A (2006) 18 207-221... 

The general term metallation describes that process in which reaction of an unsaturated system with a metal or an electrophilic metal salt results in formation of an unsaturated organometallic compound by formal replacement of a C—H bond by a C—metal bond, as for example in the mercuration of benzene (Scheme 3). The term oxymetallation is used to describe the... 

Beside these free radical reactions of sulfur dioxide, its electrophilic reactions generating sulfmates with organometallic compounds - or sulfinic acids with arenes under Friedel-Crafts conditions are well known. To complete these three-component syntheses, the sulfmates prepared first are transformed to sulfones by reactions with appropriate electrophiles, discussed earlier in this chapter, i.e. equation 82. 

A further interesting, and synthetically useful, reaction of carbanions— and of organometallic compounds acting as sources of negative carbon—is addition to the very weak electrophile C02, to form the corresponding carboxylate anion (36)—carbonation ... 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Very often the configuration of the organometallic reagent used is unknown. But even if it is known, predictions are difficult to make, since the bonding character or the ion-pair structure of organometallic compounds, and therefore the selectivity, is not only influenced by the character of the metal but also by important external factors such as solvent, complexation and temperature24. In addition, the nature of the electrophile itself influences the mode of reaction. Complexation of the electrophile at the metal atom (electrophilic assistance) in general is believed to favor metalloretentive attack. 

Three-component reactions between organic electrophile (halide, ester, etc.), carbon monooxide, and organic nucleophile (organometallic compound) (Equation (1)) catalyzed by transition metal complexes afford a powerful method for the synthesis of various ketones. The pioneering works in this area appeared in the early 1980s. 

Application of 7r-allylpalladium chemistry to organic synthesis has made remarkable progress[l]. As described in Chapter 3, Section 3,7r-allylpalladium complexes react with soft carbon nucleophiles such as malonates, /3-keto esters, and enamines in DMSO to form carbon-carbon bonds[2, 3], The characteristic feature of this reaction is that whereas organometallic reagents are considered to be nucleophilic and react with electrophiles, typically carbonyl compounds, 7r-allylpalladium complexes are electrophilic and react with nucleophiles such as active methylene compounds, and Pd(0) is formed after the reaction. 

The first results of anionic polymerization (the polymerization of 1,3-butadiene and isoprene induced by sodium and potassium) appeared in the literature in the early twentieth century.168,169 It was not until the pioneering work of Ziegler170 and Szwarc,171 however, that the real nature of the reaction was understood. Styrene derivatives and conjugated dienes are the most suitable unsaturated hydrocarbons for anionic polymerization. They are sufficiently electrophilic toward carbanionic centers and able to form stable carbanions on initiation. Simple alkenes (ethylene, propylene) do not undergo anionic polymerization and form only oligomers. Initiation is achieved by nucleophilic addition of organometallic compounds or via electron transfer reactions. Hydrocarbons (cylohexane, benzene) and ethers (diethyl ether, THF) are usually applied as the solvent in anionic polymerizations. 

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