Alkyllithium compounds bromides

In contrast to the non-trivial routes for the syntheses of pure aluminum(I) or gallium(I) subhalides, indium(I) chloride or bromide can simply be prepared by melting mixtures of elemental indium and indium trihalides [39]. When these in-dium(I) halides were treated with bulky alkyllithium compounds, deep violet orga-noelement indium dusters (13-18) were obtained [Eq. (3)] [40, 41]. 

For example, Kharasch found that phenylmagnesium bromide reacts with acetone slightly faster than with acetaldehyde (krel 1.4)65a). In other cases, aldehydes are somewhat more reactive65b). The polar and highly reactive alkyllithium compounds 64b) are even less selective 66) (Equation 7). 

Just as aromatically bonded hydrogen is more acidic than aliphatically bonded hydrogen, it is observed that aromatically bonded halogen is more cationic than the halogen in alkyl halides. Thus aryl bromides react with alkyllithium compounds to form aryllithium derivatives and alkyl bromides ... 

Aryl—alkyl coupling. The reaction of aryl bromides with alkyllithium compounds in ether results mainly in halogen—metal exchange. However, when THF is used as solvent aryl bromides react with primary alkyUithiums (1 hr., 25°) to give the cross-coupled products in 50-70% yields ... 

The reaction was also successful with alkyllithium compounds butyl-lithium, n-butyl bromide, and phosphorus gave dibutyl- and tributyl-phosphines in 10% and 39% yields, respectively. 

Most alkyllithium compounds are prepared by the direct synthesis method shown in equation (1). For example, lithium metal reacts with bromomethane in ether to form methyl lithium and lithium bromide (equation 16). ... 

Alkyllithium compounds and Grignard reagents are rarely isolated they are formed in solution and used immediately in the desired reaction. Sensitive to air and moisture, they must be prepared and handled under rigorously air- and water-free conditions. Simple examples, such as methyllithium, methylmagnesium bromide, butyllithium, and others, are commercially available. 

The preparation of benzyllithium from benzyl halides and alkyllithiums is not feasible because the benzyllithium initially formed reacts with the starting benzyl halides, producing 1,2-diphenylethane. Metalation of toluene with n-BuLi in the presence of TMEDA at 30 °C results in a 92 8 ratio of benzyllithium and ring metalated products. Metalation of toluene with n-BuLi in the presence of potassium rert-butoxide, and treatment of the resultant organopotassium compound with lithium bromide, affords pure benzyllithium in 89% yield. Alternatively, benzyllithiums are accessible by cleavage of alkyl benzyl ethers with lithium metal. " ... 

A redox cyclopentadienyl iron moiety can also be introduced into the poly(vinyl chloride) backbone by a similar technique.Many other attempts were reported at replacing the halogens of poly(vinyl chloride), poly(vinyl bromide), and poly(vinyl iodide) with an alkali metal or with a hydrogen. For instance, in an effort to form poly(vinyl lithium), the polymers were reacted with organolithium compounds and with metallic lithium. The reactions with alkyllithium, however, resulted in substitutions by the alkyl groups, similarly to the reactions shown previously ... 

In the research groups of Seebach [67, 153] and Tidwell [154], alkyl and aryl lithium compounds were found to add readily to ketenes 153 that are accessible by various methods, as, for example, treatment of acid chlorides with triethy-lamine or acid bromides with zinc. As a result, ketone enolates 154 are formed. Due to the high reactivity of the ketenes, the protocol permits to access even sterically hindered trisubstituted enolates, the configuration of which depends on the steric demand of the substituents and R. Thus, alkyllithium reagents add from the sterically less hindered side, so that enolates 154 form with high diastereoselectivity. Of course, the ketone enolates thus generated are pure regioisomers. 

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