Wurtz reaction coupling reactions

In addition to its uses in photography and medicine, iodine and its compounds have been much exploited in volumetric analysis (iodometry and iodimetry, p. 864). Organoiodine compounds have also played a notable part in the development of synthetic organic chemistry, being the first compounds used in A. W. von Hofmann s alkylation of amines (1850), A. W. Williamson s synthesis of ethers (1851), A. Wurtz s coupling reactions (1855) and V. Grignard s reagents (1900). 

Polysilanes with functionalities Z directly attached to the silicon main chain are generally more difficult to synthesize and less stable, due to the reactivity of both the Si-Z and Si-Si linkages. Such polymers are usually not accessible via the Wurtz-type coupling reaction, and alternative synthetic strategies (see Sections 3.11.4.1 and subsequent) or postpolymerization techniques have to be employed. 

Most polysilanes are synthesized by the Wurtz-type coupling reaction, which is non-stereospecific, and hence the configuration is usually undefined, although in a few cases, stereochemically defined polysilanes have been synthesized (ROP of all-anti l,2,3,4-tetramethyl-l,2,3,4-tetraphenylcyclotetrasilane99 101 and masked disilene polymerization).61... 

The Wurtz-type coupling reactions, which were one of the original methods for the formation of Ge-Ge bonds, are still in use.337 Various other synthetic techniques have been developed and improved upon in recent years as well. 

THF at -78 °C.[55] The reaction excludes the effect of the Wurtz-type coupling reaction,... 

Narrowly distributed Pl-ft-PS-i-PI triblock copolymer chains with both of their ends capped with bromobutyl groups were prepared by sequential addition of living anionic polymerization and terminated by excess of 1,4-dibromobutane (PS block Mw = 3.5 x 103 g/mol PI blocks Mw = 3.1 x 103 g/mol Mw/Mn = 1.12 The degree of end-functionalization was 92% characterized by HNMR). Figure 6 shows the SEC profile of such prepared triblock copolymer chains. The small but a detectable amount ( 5%) of Pl-i-PS-i-PI dimers, PI-Z>-PS-Z>-PI-c-PI-Z>-PS-Z>-PI, is presumably formed via the Wurtz-type coupling reaction. 

Carboranylene-1, l, 2,2-tctraructhyl-1,2-digcrruacyclobutanc has been prepared using the Wurtz-type coupling reaction of >-bis(chlorodimethylgermyl)-carborane with sodium (Equation 21) <2002IC3084>. 

SCHEME 1. Wurtz-type coupling reaction of dialkyldichlorogermanes... 

Wurtz-type coupling reactions of bis(halodiorganogermanium)-ethene, -thiophene and -benzene derivatives 32 were reported to give soluble polymers 33108 with molecular weights in the range of A/w = 2.1 to 3.3 x 104 (Scheme 18). 

R. G. Jones and S. Holder, Synthesis of polysilanes by the Wurtz reductive coupling reaction , in Reference 4, pp. 353-374. 

Wurtz-type coupling reactions of bis(halodiorganogermanium)-ethene, -thiophene and... 

The new copolymeric materials were synthesized via a Wurtz-type coupling reaction (equation 9)... 

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)... 

Di- and trigermanes have been synthesized in 73-75% yields by the Wurtz-type-coupling reactions of phenyl chlorogermane or phenyl dichlorogermane with amalgamated magnesium [82]. 

Forou, M. A., Reynolds, J. L. The Wurtz cross-coupling reaction revisited. Main Group Metal Chem. 1994, 17, 399-402. 

Missing compounds in the series of six-membered stannylsilanes containing tin atoms in the 1,2,3- (4), 1,2,4,5- (5) or in 1,3,5-positions (6) could not yet be obtained via the reaction type described. A retrosynthethic analysis (Scheme 2) reveals that the compounds should be obtainable by a Wurtz-type coupling reaction of halogen-substituted stannylsilane synthons. 

Similar to polystannanes a number of poly(dialkylgermane)s have also been prepared by the Wurtz-type coupling reaction (see Eq. 1.9) [23,24]. 

Synthesis of Polysilanes by Wurtz-type Coupling Reactions... 

In spite of its many drawbacks (as will be evident during the course of this discussion), the alkali metal-assisted Wurtz-type coupling reaction remains by far the most widely used procedure for the preparation of polysilanes... 

The Wurtz-type coupling reaction of diorganodichlorosilanes is characterized by the appearance of an intense blue-purple color in the reaction mixture. Although the initial suggestions for the origin of the blue color related to the possibility of F-centered defects in the sodium chloride that was formed, careful experimentation by EPR and UV-Visible spectroscopy indicated that colloidal sodiiun formed in the reaction is responsible for the color [37]. 

The Wurtz-type coupling reaction of R2GeCl2 with sodium in high-boiling solvents such as toluene at reflux temperatures affords polygermanes (see Eq. 8.2). 

These authors demonstrated that, under carefully controlled reaction conditions, stable allylic-magnesium halides could be formed. The Wurtz-type coupling reaction which leads to the formation of 1,5-hexadiene and which is responsible for the loss of most, if not all, of the allylic halide could be suppressed almost completely ... 

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