Aryl halides with lithium

The reaction of strong bases with aryl halides results in the generation of an aryne through loss of HX, Arynes can also be formed by reaction of aryl halides with lithium and organolithium compounds. 

The same order of ease of replacement applies to reduction of aryl halides with lithium aluminum hy-dride and with zinc (equations 22 and 23). ... 

Aryllithium reagents are familiar to us as the products of the reaction of aryl halides with lithium. A second route to aryllithiums is by deprotonation of an aromatic ring with an alkyllithium reagent. This process is called metalation. 

Sonication of aryl halides with lithium with low intensity ultrasonic gives organolithium reagents. These are used in Bouveault reaction giving higher yields of aldehydes (Scheme 27) than the traditional methods." ... 

The well-documented effects of ultrasound on heterogeneous systems have been exploited to produce beneficial increases in the rates of a number of reactions that would more commonly be executed under homogeneous conditions. For instance, the reduction of aryl halides with lithium aluminium hydride occurs extremely slowly in THF solution. However, Han and Boud-jouk have reported that the reaction can be carried out in a fraction of the time if the reaction mixture is sonicated in dimethoxyethane (DME) solution [6]. Sonolysis of the heterogeneous reaction mixture gives high yields (70-99 %) of the reduced product. The effect was particularly marked in the case of deactivated aryl halides for example, p-bromotoluene gave a 97 % yield of toluene in 5 h. In contrast, the yield of the stirred reaction was a modest 21 % after 24 h at room temperature in THF (Scheme 112). 

Aryl sulfides are prepared by the reaction of aryl halides with thiols and thiophenol in DMSO[675,676] or by the use of phase-transfer catalysis[677]. The alkenyl sulfide 803 is obtained by the reaction of lithium phenyl sulfide (802) with an alkenyl bromide[678]. 

Preparation Using Metallic Lithium. Most simple organolithium reagents can be prepared by reaction of an appropriate halide with lithium metal. The method is applicable to alkyl, aryl, and alkenyl lithium reagents. 

Insertion of zinc dust into aryl or heteroaryl iodides is also possible, but polar cosolvents are required in some cases [48, 49]. The use of highly activated zinc (Rieke zinc) prepared by reduction of zinc halides with lithium results in faster insertion (Scheme 2.24) [50-52]. 

At this time the applicability of organozinc chemistry had been limited to those zinc reagents that could be prepared by insertion of zinc powder into the corresponding alkyl iodide.20 Further developments, notable the use of highly reactive zinc (Rieke zinc), obtained by the reduction of zinc halides with lithium naphthalenide, allowed the preparation of zinc reagents from otherwise unreactive organic substrates, such as aryl iodides and aryl bromides (Scheme 1.7).21... 

The alkyls and aryls may be obtained by interaction of copper(I) halides with lithium or Grignard reagents. The alkyls usually decompose readily but methyl copper, a bright yellow polymer insoluble in organic solvents, is reasonably stable it can be used in certain organic syntheses, but the use of lithium alkyl cuprates... 

There are very few studies of the Barbier reaction mechanism with magnesium as the metallic source. However, with the discovery that the reaction will often proceed to a greater extent with other metals such as lithium, some good mechanistic studies have been conducted. The focus of most of these studies has been the reaction of an alkyl or aryl halide with a ketone. The conclusions drawn from these studies are considered to be valid for magnesium as well, and they will be referenced in this section. 

Ketones. Organomangane benzyl, aryl, heteroaryl ) with R halides with lithium naphthalenid ketones. 

Ketones. Organomanganese reagents are formed by reaction of various halides (e.g., benzyl, aryl, heteroaryP) with Rieke Mn, which is prepared by reduction of manganese(II) halides with lithium naphthalenide in THF. Such reagents react with acid chlorides to afford ketones. 

Except the metallation of aryl halides with the lithium metal and the Grignard reaction, the arylmetallics can be alternatively prepared by ... 

Homocoupling of organometallic generated in situ by the reaction of alkyl, aryl of vinyl halides with lithium in THF takes place on sonication (Scheme 19). No reaction takes place in absence of ultrasound. 

It should also be noted that copper-catalyzed Ullmann-type coupling of aryl halides with amines yields substituted products [206], and reaction with diphenylamine has been used to form triaryl-amines [207], Triarylamines may also be formed in a variation of the Meyers reaction [47] by displacement by lithium amides of fluoro- or methoxy-substituents activated by an ort/io-ester function [208], The oxidation of a-adducts is discussed in Chapter 11, but it should also be mentioned that aminated products may also be produced by the oxidation of adducts formed by the addition of amide or alkylamide ions at ring carbon atoms carrying hydrogen [209]. 

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