The Organic Halide

Organic Synthesis Using Transition Metals, Second Edition. Roderick Bates. 2012 John Wiley Sons, Ltd. Published 2012 by John Wiley Sons, Ltd. 

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The organic halide that reacts with the arene must be an alkyl halide (Section 12 6) or an acyl halide (Section 12 7)... 

Organolithium reagents (Section 14 3) Lithi um metal reacts with organic halides to pro duce organolithium compounds The organic halide may be alkyl alkenyl or aryl Iodides react most and fluorides least readily bro mides are used most often Suitable solvents include hexane diethyl ether and tetrahy drofuran... 

Grignard reagents are normally prepared by the slow addition of the organic halide to a stirred suspension of magne.sium turnings in the appropriate solvent and with rigorous exclusion of air and moisture. The reaction, which usually begins slowly after an induction period, can be initiated by addition of a small crystal of iodine this penetrates the protective layer of... 

The postulated steps that constitute the Suzuki coupling process are shown in Scheme 25. After oxidative addition of the organic halide to the palladium(o) catalyst, it is presumed that a metathetical displacement of the halide substituent in the palladium(ii) complex A by ethoxide ion (or hydroxide ion) takes place to give an alkoxo-palladium(ff) complex B. The latter complex then reacts with the alkenylborane, generating the diorganopalladium complex C. Finally, reductive elimination of C furnishes the cross-coupling product (D) and regenerates the palladium(o) catalyst. 

The I9e electron-reservoir complexes Fe Cp(arene) can give an electron to a large number of substrates and several such cases have been used for activation. After ET, the [FenCp(arene)]+ cation left has 18 valence electrons and thus cannot react in a radical-type way in the cage as was the case for 20e Fe°(arene)2 species. Thus the 19e Fe Cp(arene) complexes react with the organic halide RX to give the coupled product and the [FeCp(arene)]+ cation. Only half of the starting complex is used e.g., the theoretical yield is limited to 50% [48] (Scheme VI) contrary to the reaction with Fe°(arene)2 above. 

The most convenient route for introducing organo-ligands which do not contain strongly nucleophilic groups (e.g., -SH or -NH2), is from the organic halide (Section l,a, below) in most cases -SH and -NHj groups... 

Meehanistieal studies on the reaction of stable stannylenes with organic halides have been performed by M. F. Lappert and his group161 163>. On the basis of ESR spectroscopic data they proposed a radicalic pathway for this reaction. Initially, one electron of the stannylene is transferred to the organic halide the... 

Low-valent nickel complexes of bpy are also efficient electrocatalysts in the reductive coupling reaction of aromatic halides.207 Detailed investigations are in agreement with a reaction mechanism involving the oxidative addition (Equation (40)) of the organic halide to a zero valent complex.208-210 Starting from [Nin(bpy)2(X)2]0 with excess bpy, or from [Nin(bpy)3]2 +, results in the [Ni°(bpy)2]° complex (Equations (37) and (38)). However, the reactive complex is the... 

Following the reactions in Scheme 4, the olefin 13 would have to be generated before the formation of the 7r-crotyl species 2. Because the amount of the catalyst present is usually small as compared to the amount of product formed (1000 moles of product/mole catalyst), the quantity of 13 produced will not be significant and should be readily separable from the desired product. In the special case when crotyl chloride is used as the activator, hexadiene can be produced during the very first cycle of reaction, i.e., 13 = 1,4-hexadiene. Among the organic halides, the chloride derivatives are the most effective activators. Bromides are somewhat effective, while fluorides and iodide are rather ineffective (77). 

Allenones have also been transformed into substituted furans via Pd-catalyzed heteroannulation. Ma and Zhang converted 1,2-dienyl ketones and organic halides to substituted furans under the agency of Pd(Ph3P)4 and Ag2C03. Addition of 10 mol% of Ag2C03 was crucial for the reaction of the organic halide. For example, allenone 134 and 5-bromopyrimidine were converted to pyrimidylfuran 135 in excellent yield [106]. 

If one wants to use only a metal halide as the initiator for an alkene polymerisation, an analysis similar to ours can be made for the metal halide alone. In addition, there is a 1 2 equilibrium for the organic halide [35, 36] and a molecular aggregate <-> single molecule equilibrium associated with the metal halide. Thus, a solution of a carbocation salt is more exactly described by the series of linked equilibria summarised in Scheme 5. 

The errors involved in the above analysis of the Born-Haber cycle for the organic halide + metal halide are, of course, so large (of the order of 100 kj mol 1) that to convert the derived energy change into an equilibrium constant would be meaningless, but the analysis is still worthwhile since, as has been demonstrated, it provides the basis for a comparison between systems it permits predictions as to the effectiveness of untried systems and it provides explanations for some of the established experimental results. 

After multiple steps, an organic halide can be converted to a carboxylic acid. The organic halide converts to a Grignard reagent, which reacts with carbon dioxide and then acidification forms the acid. Figures 12-13 and 12-14 illustrate the steps in this process. 

As usual, the reactivity order with respect to halogen in C=C-X is I > Br > Q. The organic halide in the couplings with alkynylzinc halides is usnaily an iodide, though also activated vinylic bromides (e.g. BrCH=CHCOOC2H5) have been found to react smoothly. We... 

The reaction of the organic halide with magnesium is carried out in a non-protic polar solvent, usually diethyl ether or THF. Typical by-products are RR, RH and R(-H) (alkene), resulting from coupling and disproportionation reactions of the organic moiety. Also, by-products resulting from solvent attack are sometimes formed, but usually to a lesser extent. 

The reactions of massive zinc with the organic halides are relatively fast. Moreover, the rate of the reaction can be increased with a low current intensity being applied during the process between the cathode and the anode. 

The production of a stable or a transient intermediary of the type RNiXLn proves the activation of the organic halide RX. 

In the light-induced reactions with diazoalkanes, methylene, the photolytic fragment from diazomethane, may be interposed between the halogen atom in the organic halide and the carbon atom to which it is attached,289 290 or may add to the double bonds in the aromatic ring.58 69... 

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