Alkyl lithium compounds

The only currently unrefuted evidence even suggestive of an optically active carbanion is the report of optically active 2-octyl-lithium.899 It should be recalled, however, that ordinary alkyl lithium compounds are volatile, soluble in non-polar solvents, and generally more covalent than ionic in their behavior. 

In the preceding chapter the formation of the less stable of two isomeric acids on rapid neutralization of an organometallic compound was explained in terms of a free ion or ion pair as the reagent. The compounds involved were the salts of comparatively strong acids, however, and the media were highly polar. The ion or ion pair would be less likely to be the reagent in the case of the salt of a very weak acid, such as an alkyl lithium compound, in a non-polar solvent. Salts of unsaturated but weak acids might exist in either of two partly covalent forms this possibility provides an alternative explanation for the formation of the less stable of the two isomeric acids on neutralization. Presumably the bulk of the covalent or partly covalent... 

The reactions of alkyl lithium compounds, although closely related to those of the Grignard reagents, are somewhat easier to study because of the greater simplicity of the organometallic reagent. They are very fast reactions but some rates have been successfully measured by resort to the flow method. The reaction is second order and a transition state like LXXII has been suggested.891... 

This is a catalytic-chain mechanism because the agent which adds to the olefins is regenerated in the last step.The addition reaction of the anion to the olefin is similar to the noncatalytic reaction of alkyllithium compounds with ethylene as reported by Ziegler and Gellert 37) and by Bartlett et al. 38). In this reaction (5), the less stable secondary and tertiary alkyl lithium compounds add most readily. 

The development of electrospray ionization (ESI) enabled multiply charged ions, solvated ions, and metal-coordinated species to be formed in the gas phase. Recently, Kass and coworkers showed that collision-induced dissociation (CID) of RC02Li containing ions (e.g. 1) leads to the loss of carbon dioxide and the attachment of Li to R (Scheme 1) . This is an exceptionally stable alkyl lithium compound that could be synthesized, in the gas phase, under relatively mild conditions. 

The electrophilic reactivity of lithium carbenoids (reaction b) becomes evident from their reaction with alkyl lithium compounds. A, probably metal-supported, nucleophilic substitution occurs, and the leaving group X is replaced by the alkyl group R with inversion of the configuration . This reaction, typical of metal carbenoids, is not restricted to the vinylidene substitution pattern, but occurs in alkyl and cycloalkyl lithium carbenoids as well ". With respect to the a-heteroatom X, the carbenoid character is... 

Step-wise replacement of all three hydrogen atoms in phosphine by lithium can be obtained by the reaction of phosphine with an alkyl lithium compound in the corresponding molar ratio. The preparations of LiaP and Na3 from the elements were described by Brauer and Zintl. ... 

The preparation of an aryl lithium compound from an aryl halide and an alkyl lithium compound also produces an alkyl halide. The alkyl halide may react subsequently with the lithium arenetellurolate to yield aryl alkyl tellurium compounds. In these cases the tellurolate has only a transitory existence. 

The reaction of alkyl phenylethynyl telluriums with alkyl lithium compounds or alkyl magnesium bromides in diethyl ether at 20° leads to the replacement of the ethynyl groups by alkyl groups2. The yields in these reactions range from 68 to 95%. 

Organometallic compounds (except for alkyl aluminium and alkyl lithium compounds)... 

According to this study54, one model for studying the complex reactions of alkyl lithium compounds, involving aggregation and interactions with the solvent molecules, could be the reaction between vinylamine and LiH. The complex formed between lithium... 

High values of cage effects (Table 1) close to those detected in the reactions of alkyl-lithium compounds suggest that, similarly to n-BuLi, organogermanium derivatives of alkali metals enter the reaction in the associated state. It is necessary to note that without this assumption it would be difficult to explain the large cage effect values generally uncharacteristic for the reactions of free radicals in solution ". ... 

Examples of insertion reactions include Grignard or alkyl lithium compounds which react with carbodiimides to give formamidines 389 after hydrolysis. ... 

Sequential reaction of azines with alkyl hthium compounds and chloroformates usually affords the expected Reissert-type products 136, together with minor amounts of doubly acylated compounds 135 (Scheme 18b). Isoquinoline is likely to react directly with the alkyl-lithium compound to generate the alkylated lithio-enamine intermediate E, and this species may account for the formation of dihydroisoquinolines 135 and 136, through interaction with the electrophihc partner. Mamane recently expanded this concept by replacing the acylating agent with different electrophiles. These combinations lead exclusively to isomers 134 (Scheme 18) [118-120]. 

The syntheses of siloxanes with vinyl groups at the silicon atoms of the chain was performed by anionic ring-opening polymerization of vinyl group-containing cyclotri- or cyclotetrasiloxanes (03, 04 ) with alkyl lithium compounds as initiators. The polymerizations were terminated by chlorosilanes with additional silico- or carbofunctional groups or octyl groups. In the block copolymerizations we used 03 or 04 and hexamethylcyclotrisiloxane (D3) (Scheme 1 and 2). 

The dependence of the propagation rate on initiator concentration is more complex, however, and can be explained as reflecting the existence of more than one kind of active center in media that can solvate the counterion. The simplest situation, which is used here for illustration, corresponds to an equilibrium between free ions and ion pairs. [It is likely that various kinds of ion pairs exist (cf. Eq. 9-1) but these ramifications can be neglected in this simple treatment.] The reactions involved in the actual propagation steps in the polymerization of a monomer M by an alkyl lithium compound RLi can then be represented as... 

Lithium alkanetellurolates, prepared from tellurium and an alkyl lithium compound or dialkyl ditellurium derivatives and hthium, and sodium arenetellurolates, obtained from diaryl ditellurium compounds and sodium borohydride ", reacted with triorganosilyl, -germyl, -stannyl, and -plumbyl chlorides to produce, for instance, organo triorganosilyl tellurium compounds. 

Solution-polymerized SBR is made by termination-free, anionic/live polymerization initiated by alkyl lithium compounds. Other lithium compounds are suitable (such as aryl, alkaryl, aralkyl, tolyl, xylyl lithium, and ot/p-naphtyl lithium as well as their blends), but alkyl lithium compounds are the most commonly used in industry. The absence of a spontaneous termination step enables the synthesis of polymers possessing a very narrow molecular weight distribution and less branching. Carbon dioxide, water, oxygen, ethanol, mercaptans, and primary/secondary amines interfere with the activity of alkyl lithium catalysts, so the polymerization must be carried out in clean, near-anhydrous conditions. Stirred bed or agitated stainless steel reactors are widely used commercially. 

Optimum Conditions for Preparing Phenyllithium from Benzene. The optimum procedure for metalation of an aromatic compound in high yield was to use the aromatic compound itself as the solvent. The alkyl-lithium compound used mainly in this study was n-butyllithium because it was convenient and economical. 

In 1971 the second perlithio compound, C5Li4, was obtained by lithiation of 1,3-pentadiyne (7, 8). When the latter is treated with alkyl-lithium compounds in the absence of TMEDA, addition of alkyllithium reagents to one of the triple bonds is the main reaction, and no highly metalated products form. However with TMEDA, polylithiation takes... 

Polylithiation of aromatic compounds offers much promise for future research. It is evident that perlithioaromatics can be prepared, albeit only mixed with less-highly lithiated species. Moreover the perlithio aromatics seem to be stable species once formed. A major problem limiting further advance in this area is the lack of a polar solvent inert to alkyl-lithium compounds at moderate temperatures. Activation of organo-lithium compounds by chelating diamines seems likely to play an important role in the further development of lithiocarbon chemistry, both in the aliphatic and aromatic series. 

Alkyl Aryl-Halogen Substitution. Reactions of (NPCla)a with MeLi are supposed to proceed via methyl-halogen substitution and not via metal-halogen exchange, thus giving rise to extensive ring cleavage. An important factor responsible for the low yields of reactions of (NPXa)s (X = Cl, F) with alkyl-lithium compounds... 

Lithium is also frequently used as alkyl lithium compounds. These are useful in substitution reactions for organic chemistry and have the unique capacity to invert the polarity of the functional carbon atom. Upon reduction, it s converted from an electrophilic species to a nucleophilic species. 

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