Reactivity organic halides

Wiberg has described the reactions of the silene Me2Si=C(SiMe3)2 with a wide variety of reagents and has reported on their relative rates of reaction (see Table VIII).98 174 Some silenes will add chlorogermanes and chlorostannanes174 as well as reactive organic halides such as chloroform, carbon tetrachloride, and benzyl chloride. 

Another approach, recently described, consists in the electrochemical preparation of a very active zinc with the use of a mediator3. This zinc is able to react with low reactive organic halides. This electrochemical process is analogous to the chemical reaction developed by Rieke in which the naphthalene anion radical is used to activate metals such as zinc4. 

Scheme 17 illustrates enantioselective synthesis of a-amino acids by phase-transfer-catalyzed alkylation (46). Reaction of a protected glycine derivative and between 1.2 and 5 equiv of a reactive organic halide in a 50% aqueous sodium hydroxide-dichloromethane mixture containing 1-benzylcinchoninium chloride (BCNC) as catalyst gives the optically active alkylation product. Only monoalkylated products are obtained. Allylic, benzylic, methyl, and primary halides can be used as alkylating agents. Similarly, optically active a-methyl amino acid derivatives can be prepared by this method in up to 50% ee. 

The catalyst for the reaction between PVC and the high cis-1,4-polybutadiene was a dialkylaluminum halide—e.g., Et2AlCl—or sesquihalide. The catalyst could be added from an external source or could be generated in situ—e.g., by the reaction of an aluminum alkyl with either titanium tetrachloride or a reactive organic halide such as benzyl chloride or tert-butyl chloride. The concentration of Et2AlCl was varied from 0.2-5% by weight based on PVC, although the preferred concentration was between 0.5 and 1.5 wt %. 

Hydrogen fluoride alone undergoes exchange reactions only with very reactive organic halides. However,. because it reacts with antimony chloride to form antimony fluoride and hydrogen chloride,34 it can be used to transform a large amount of organic halide to the fluoride with the aid of only small.amounts of antimony salts. This is the method used in industry for the preparation of dichlorodifluoromethane.34-36... 

Interaction of trichlorogermane, and especially its etherates and aminates, with reactive organic halides results in nucleophilic substitution on organic halides by the trichlorogermyl group (equation 8)43,44. 

The direct reaction of tin (as foil, powder, or alloy) with organic halides has been used to produce organotin halides. Catalysts and promoters are required for all but the most reactive organic halides MePh3PBr and KI were used as catalyst and promoter, respectively, for the formation of... 

Rapid and nearly complete alkylation of carboxylate salts with reactive organic halides has been demonstrated in nonpolar and polar solvents. With less reactive alkyl halides, the use of dipolar aprotic solvents for alkylation has been marginally successful. The rate of alkylation of potassium 2-methyl-2-propylpentanoate with 1-chlorohexane in four dipolar aprotic solvents at 60 °C decreased in the order HMPA > iV-methylpyrrolidone > DMSO > DMF. ... 

With the more reactive organic halides, side reactions occur however the allyl adducts RInXa (diox), where R = allyl or benzyl and X = Cl, Br, or I, are obtained by shaking InX with a mixture of RX and dioxane. The aryl halides do not react with InX. To prepare arylindium halides from InX, it is necessary to use organomercurials ... 

Allyl and benzylzinc bromides are also useful for preparing hydrocarbons by crossed Wurtz coupling with reactive organic halides. 

Alkylating potency of the organophosphorus compounds was determined by measurement of rate constants of nucleophilic displacement reactions (SN) between the test compounds and 4-nitrobenzylpyridine (4-NBP) as nucleophile. Chemical reactivity towards 4-NBP was previously used in a QSAR analysis of reactive organic halides by Mermens et al. (1985a). The procedure used here was slightly different from the one described in the previous study. The most remarkable difference was the temperature at which the reactions were carried out (22°C instead of 80°C). 

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