Wurtz-Fittig coupling

Two mechanisms have been proposed for the Wurtz reaction (compare Section III,7) and for the Wurtz-Fittig reaction. According to one, sodium reacts with the alkyl halide to produce a sodium halide and a free radical, which subsequently undergoes coupling, disproportionation, etc. ... 

Sodium and magnesium do not react with tetrachlorosilane at room temperature, but do so at elevated temperatures and ia the presence of polar aprotic solvents at moderately elevated temperatures. The Wurtz-Fittig coupling of organosilanes to form disilanes (168) and polysdanes (169) is usually accomphshed usiag molten sodium ia toluene or xylene. 

The coupling of alkyl halides 1 upon treatment with a metal, e.g. elemental sodium, to yield symmetrical alkanes 2, is called the Wurtz reaction. Aryl alkanes can be prepared by the Wurtz-Fittig reaction, i.e. the coupling of aryl halides with alkyl halides. 

The synthetic applicability is rather limited, due to the various side-reactions observed, such as eliminations and rearrangement reactions. The attempted coupling of two different alkyl halides in order to obtain an unsymmetrical hydrocarbon, usually gives the desired product in only low yield. However the coupling reaction of an aryl halide with an alkyl halide upon treatment with a metal (the Wurtz-Fittig reaction) often proceeds with high yield. The coupling of two aryl halides usually does not occur under those conditions (see however below ) since the aryl halides are less reactive. 

In the Wurtz Reaction, both halides are alkyl. For the Wurtz-Fittig Reaction, there is one alkyl and one aryl group, while in the Fittig Reaction, both coupling partners are aryl halides. 

An alternative to produce H-H arranged PIB is the coupling via the Wurtz-Fittig reaction. This is the coupling of alkyl halides by the treatment with metallic sodium or other metals such as lithium and zinc. However, this type of reaction results in substantially branched polymers with a comparatively low molecular weight (19). 

Wurtz-Fittig reactions are C-C coupling reactions of alkyl halides with alkali metals. This synthetic procedure is often applied for Si-Si coupling of silicon halides. See (a) A. Wurtz, Ann. Chim. Phys. 44, 275 (1855). (b) B. Tollens, R. 

The coupling of alkyl halides by treatment with sodium to give a symmetrical product is called the Wurtz reaction. Side reactions (elimination and rearrangement) are so common that the reaction is seldom used. Mixed Wurtz reactions of two alkyl halides are even less feasible because of the number of products obtained. A somewhat more useful reaction (though still not very good) takes place when a mixture of an alkyl and an aryl halide is treated with sodium to give an alkylated aromatic compound (the Wurtz-Fittig reaction)... 

The rather unreactive arylcadmium reagents, ArCdCl, do react satisfactorily with both primary and secondary a-bromo esters and with secondary allylic bromides, but curiously they react much more poorly with allyl and benzyl bromide, and a-chloro ethers ca. 40% yields) no coupling occurs using primary alkyl bromides. Finally, the old Wurtz-Fittig mediodology, whereby an aryl bromide and an alkyl iodide are coupled in the presence of elemental sodium, can sometimes lead to acceptable yields (40-60%) no rearrangement products are formed, and it is likely that free radicals are not involved. 

Wurtz-Fittig reaction The coupling of an alkyl and an aryl halide with sodium to give the alkylaromatic compound. 

In conclusion it should be pointed out that the unusual success of the Wurtz-Fittig reaction in coupling two unlike halides can be understood if we assume that phenyl sodium predominates over the alkyl sodium in the first phase of the reaction and that phenyl sodium reacts preferentially with alkyl halides in the second phase of the reaction. These assumptions seem very reasonable, since arbmatic halides are always more inert to displacement reactions than alkyl halides and ethyl sodium has been shown to react even with benzene to give phenyl sodium and ethane.11 Consequently, when a solution of ethyl bromide and bromo-... 

PPP was first synthesized by Goldschmiedt (1886). He applied the Wurtz-Fittig reaction which coupled para-dibromobenzene using sodium, and the product was determined to be a tridecamer (13 subunits) by elemental analysis. In 1936, the same monomer was used and a PPP containing up to 16 benzene rings was obtained (Busch et al. 1936). 

Metal-catalyzed coupling reactions (Grignard, Ullmann, Wurtz-Fittig, Yamamoto and Suzuki)... 

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