Halogen-metal exchange reactions

H - Metal exchange or Halogen - Metal exchange or Sulfoxide - Metal exchange reaction... 

Substituted 1,2,3-triazole 1-oxides 448 have been reported to undergo electrophilic and nucleophilic aromatic substitution and are subject to debromination, proton-metal exchange, and halogen-metal exchange followed by electrophilic addition. Transmetallation and cross-coupling have not been described. 3-Substituted 1,2,3-triazole 1-oxides 448 can be proton-ated or alkylated at the O-atom and they can be deoxygenated and deal-kylated. The individual reactions are described in Section 4.2.7.1-4.2.7.14. 

In neither case was it possible to propose definitive mechanisms due to the complexity of the systems in the 7-alumina study, it is suggested that adsorption-desorption processes are slow relative to rapid dismutation between two adsorbed species [105], while from the chromia study mono-molecular halogen exchange reactions with metal halide surface sites are indicated [38], The latter mechanism is reminiscent of the halogen exchange model proposed [95] for C2 CFCs on fluorinated chromia. 

The halogen-metal exchange reaction was pioneered by Gilman and co-... 

The metal-halogen exchange reaction is useful in the synthesis of numerous perfluoroalkylmagnesium halides, some of which are shown in Table 2... 

Although the metal-halogen exchange reaction is the preferred method of synthesis, the conventional Grignard synthesis through the reaction of a per-fluoroorgano halide and magnesium occasionally is still used [49, 50]... 

Novel polyfluoroethyl Gngnard reagents containmg fluonne, chlorine, and bromine are prepared through the metal-halogen exchange reaction [46] (equation 20)... 

To avoid this competing reaction, the metal-halogen exchange is performed in diethyl ether with either secondary or tertiary butyllithium at -60 °C to give the trifluorovinyllithium compound in near quantitative yield [59],... 

An example of intramolecular conjugate addition of aryllithium generated by halogen metal exchange reaction of 92 is illustrated in equation 7966. 

It seems likely that the mechanism of the Wurtz reaction consists of two basic steps. The first is halogen-metal exchange to give an organometallic compound (RX -(- M —+ RM), which in many cases can be isolated (12-36). Following this, the organometallic compound reacts with a second molecule of alkyl halide (RX + RM —> RR). This reaction and its mechanism are considered in the next section (10-94). 

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