Wurtz-like reactions

The possibilities of synthesis are limited by the general properties of the Si-Si bond to a small number of reaction types. Disilane derivatives were usually synthesized by a Wurtz-like reaction of monosilane halide derivatives with alkali or alkaline-earth elements. Some pyrolysis reactions that have yielded disilane derivatives are also known. Often, new disilane derivatives were prepared from common derivatives by an exchange of substituents. Some rearrangements have been observed in recent years. 

Wurtz-like reactions were carried out with many organohalosilanes and it is not possible in this review to present details on all the compounds formed. Some examples of the general reaction... 

The results of the Wurtz-like reaction depend on the reaction conditions. An important factor is the kind of solvent The ethers are generally better than hydrocarbons, but with the cyclic ethers like tetrahydrofuran (THF), dioxane and other frequently used agents, a cleavage reaction of the ethers was observed392. Hexamethylphosphoricacid amide was recently used with good results in combination with lithium497. ... 

Gilman s significant observation that triphenylchlorosilane is a catalyst in Wurtz-like reactions forming cyclic silanes appears to be due to intermediate formation of triphenylsilyl lithium (see Chapter 9 Cyclic Silanes). The triphenyl compounds are particularly good catalysts because the corresponding alkali-triphenylsilyl compounds are the most stable among the alkali-organo-silicon compounds. 

The Hungarian chemist Mezaros1 states that pyrophoric lead can be prepared by reaction of lead oxide with furfural vapors at 290°. It can be purified by washing with benzene and aqueous alcohol. It is described as a new reagent for Wurtz-like reactions, for example ... 

Zinc has a specific role to play in some special cases for removal of halogen in a Wurtz-like reaction.347 It is used especially for the synthesis of smallring compounds, e.g., of cyclopropanes from 1,3-dihalogen compounds.348 Shortridge348 describes the preparation of 1,1-dimethylcyclopropane as follows ... 

Polycarbosilanes can be obtained by a Wurtz-like condensation of dichloro-silanes in mixture with a dihalomethane. The products obtained in these reactions do contain not only the desired Si-C-Si linkages but also oligosilane units -(SiR2)x- and -(CH2)x- units [93] ... 

Higher members like [23](l,4)cyclophane (34) are available in a modified Wurtz coupling reaction [38]. Cram [32] described the complexation of only one benzene ring of 34, while Elschenbroich [39] succeeded in the complexation of the second and third benzene ring by variation of stoichiometry and prolonged reaction time (Fig. 6b). 

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). 

The mechanism is not known with certainty. It seems likely that it is basically a two-step process, similar to that of the Wurtz reaction (10-93), which can be represented schematically by... 

Most recently, a simple, mild, one-pot immobilization method was developed to attach the rigid rod-like helical polysilane, poly( -decyl-/-butylsilylene), via a siloxy linkage to hydrophilic quartz or mica substrate surfaces.28 195 Triethylamine was used as a catalyst to couple the Si-H and/or Si-OR termini of the dialkylpolysilane chains (which are generated during the course of Wurtz-type synthesis and workup)51,195 with the surface -OH groups. AFM, UV, and IR data were used to analyze the reactions. 

It is both a pleasure and a privilege to have been invited to write the Foreword to a book of such importance as Dr. Comyns dictionary of named processes in the chemical industry. For many years, chemists have had access to books with titles like Named Reactions in Organic Chemistry. Here the busy student or researcher can discover immediately the nature of the Wurtz reaction, the Cannizzaro reaction, and such curiosities as the Hell-Volhard-Zelinsky reaction. Until the first edition of the present book appeared in 1993, no such literary assistance was available to the multitudes who labored in the chemical industry. Six years later, a second edition took into account the many novelties that had appeared in that short period. Now a third edition is expanded still further, particularly by inclusion of many biological processes that industry now uses. 

The characteristic properties and reactions of ammonia are also true of the amines. They have a strong fishy, ammonia-like odor, but unlike ammonia the lower ones are inflammable. It was this fact which led to their discovery. Wurtz supposed that the volatile substance he had obtained was ammonia until a flame was accidentally brought near it when it ignited. They are readily soluble in water, and their solutions are alkaline to litmus. 

Further evidence of monomer adsorption on a metal surface is provided by the extensive studies of Richards and his co-workers (14). As is well known, alkyl bromides in tetrahydrofuran vigorously react with alkali metals, say lithium, yielding the Wurtz coupling products. The violent reaction slows down on addition of aromatic monomers like styrene, and the nature of... 

Although the classical Wurtz-Fittig synthesis has been widely replaced by procedures using milder reaction conditions (see following chapters), alkali metals like potassium in dimethoxyethane (DME) have been used in the dimerization of 1,1 binaphthyls (e.g. 47, see Scheme 21) to perylene derivatives (e.g. 

The Wurtz reaction constitutes the direct coupling of the nucleophilic carbon of an alkylsodium compound and the electrophilic carbon in a haloalkane. It is an unselective reaction. There is no way to control it to prevent coupling of two like alkyl groups while attempting to couple two different ones. In other words, the reaction between chloroethane and 1-chloropropane gives a statistical mixture of butane (from two ethyls), pentane (from an ethyl and a propyl), and hexane (from two propyls). 

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