Organic halides reaction with metals

Table I. Organic Halide Reactions with Metal Atoms...

The facilitation of ultrasound in many organic reactions involving metals before 1998 has been reviewed by Luche and colleagues. " In many reactions that involve organic halides reacting with metals, mechanisms which do not involve a direct carbon-to-metal bond have found more general acceptance. In this chapter, these reactions are excluded and only new reports that are not covered in Refs 71 and 90 are discussed. 

The discovery by Grignard that organic halides react with metallic magnesium to give nucleophilic organomagnesium compounds was a landmark in organic synthesis. The reaction of a halide with metallic magnesium in diethyl ether remains the principal method of synthesis. The order of reactivity is RI > RBr > RCl. 

The Bouveault reaction is the preparation of an aldehyde by a one pot reaction between an organic halide and lithium metal in dimethylformamide. Ultrasound has been found to markedly enhance this reaction when it is performed in tetrahydrofuran [93]. Use of an ultrasonic bath at 10-20 °C affords short reaction times of between 5 and 15 min and generates yields in the range 70-88%. Using this methodology the conversion of 1-bromobutane to pentanal (88%) can be achieved in only 5 minutes. This must be contrasted with the yield of less than 10 % which is obtained under the normal stirred conditions in the same time period. This result confirms that the effect of irradiation goes beyond mere agitation (Eq. 3.11). 

The most systematic study of reactions of transition metal atoms with halogen compounds has been the work of Klabunde on oxidation of nickel and palladium atoms. Some work has been done with copper, silver, gold, and platinum, but only scattered results have been reported for other metals. Klabunde s research has shown that perfluoroorgano-halides form isolable organometallic compounds on reaction with metal atoms much more commonly than nonfluorinated halides. The types of reactions observed with different classes of organic halides are considered next. 

Sodium Condensation. The coupling of an organic halide and a silicon halide by reaction with metallic sodium (the so-called Wurtz reaction) vras first applied by Pape in 1884. Silicon tetrachloride and isoamyl or isobutyl chloride were found to react with sodium at reflux temperatures when a little ethyl acetate was added to get the reaction started ... 

Formation of Carbon-Transition and Inner Transition Metal Bond 121 5.8.2.9. from Organic Halides, Tosylates and Acetates 5.8.2 9.2. by Reaction with Metal-Complex Anions... 

Binary ionic or covalent hydride reduction of organic halides is important in organic syntheses . Reactions of metal hydrides with alkyl halides in ethers occur ... 

Subsequently, kinetic studies reported by Whitesides and collaborators [81] provided further support for the view that the rate-determining step in formation of alkyl Grignard reagents involves electron transfer from the metal surface. The kinetics of the reaction of an organic halide RjX with magnesium were described by Eq. (3), in which S g accounted for the characteristics of magnesium surface that influence the rate, and an analogous... 

Monoorganozinc halides (RZnX) can be synthesized by oxidative addition of organic halides to zinc metal. The oxidative addition rate is strongly affected by the reaction conditions (solvent, concentration) [16] and by activation of the zinc [15,17]. Zinc powder or zinc foil, which is activated by treatment with 1,2-dibromoethane and then with trimethylsilyl chloride, will oxidatively add alkyl iodides [18]. The reaction of alkyl bromides, on the other hand, requires more active zinc, which may be prepared by the reduction of zinc chloride with either lithium naphthalenide [19] or lithium metal under ultrasonic.irradiation [20, 21]. 

If the reactions of organic halides and Mg metal are performed in hydrocarbons with the addition of 1 or a few equiv of an electron-pair donor base, they occur much more... 

Organolithium compounds are of particular importance among the group 1 organometallics. They may be synthesized by treating an organic halide, RX, with Li (equation 18.5) or by metallation reactions (equation 18.6) using n-butyllithium which is commercially available as solutions in hydrocarbon (e.g. hexane) solvents. 

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