Compound alkyllithium

Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

The kinetics of initiation reactions of alkyllithium compounds often exhibit fractional kinetic order dependence on the total concentration of initiator as shown in Table 2. For example, the kinetics of the initiation reaction of //-butyUithium with styrene monomer in benzene exhibit a first-order dependence on styrene concentration and a one-sixth order dependence on //-butyUithium concentration as shown in equation 13, where is the rate constant for... 

Silanes react with alkyllithium compounds, forming various alkylsilanes. Complete substitution is generally favored however, less substituted products can be isolated by proper choice of solvent. AH four methylsHanes, vinylsHane [7291-09-1and divinylsilane [18142-56-8] have been isolated from the reaction of SiH and the appropriate alkyllithium compound with propyl ether as the solvent (35). MethylsHane and ethyldisHane [7528-37-2] have been obtained in a similar reaction (36). 

Chromium alkyls [(>j -(3-t-Bu-5-Mepz)3B)CrR] (R = Et, CH2SiMc3, Ph) follow from the corresponding homoleptic complexes and alkyllithium compounds (97CEJ1668). 

Alkyllithium compounds have been used to give ketones from carboxylic esters. The reaction must be carried out in a high-boiling solvent, such as toluene, since... 

There is evidence that the mechanism" of the reaetion of alkyllithium compounds with alkyl and aryl iodides involves free radicals." ... 

The latter reagent also methylates certain heterocyclic compounds (e.g., quinoline) and certain fused aromatic compounds (e.g., anthracene, phenanthrene). The reactions with the sulfur carbanions are especially useful, since none of these substrates can be methylated by the Friedel-Crafts procedure (11-12). It has been reported that aromatic nitro compounds can also be alkylated, not only with methyl but with other alkyl and substituted alkyl groups as well, in ortho and para positions, by treatment with an alkyllithium compound (or, with lower yields, a Grignard reagent), followed by an oxidizing agent such as Bra or DDQ (P- 1511). 

Isocyanides that do not contain an a hydrogen react with alkyllithium compounds, as well as with Grignard reagents, to give lithium (or magnesium) aldimines. These metalated aldimines are versatile nucleophiles and react with various substrates as follows ... 

Reaction between lithium carboxylates and alkyllithium compounds... 

As with organomagnesium reagents, there is usually loss of stereochemical integrity at the site of reaction during the preparation of alkyllithium compounds.25 Alkenyllithium reagents can usually be prepared with retention of configuration of the double bond.26,27... 

The interpretation of the basis for this stereoselectivity can be made in terms of the steric, torsional, and stereoelectronic effects discussed in connection with reduction by hydrides. It has been found that crown ethers enhance stereoselectivity in the reaction of both Grignard reagents and alkyllithium compounds.119 This effect was attributed to decreased electrophilicity of the metal cations in the presence of the crown ether. The attenuated reactivity leads to greater selectivity. 

These coupling reactions can also be done with boronate esters activated by conversion to ate reagents by reaction with alkyllithium compounds.279 For example, analogs of leukotrienes have been synthesized in this way. 

Alkyllithium compounds are only rarely used for the preparation or organogermanes or... 

Using alkyllithium compounds, some organometallic bis(p-hydroxyphenyl) derivatives 4 of Ge, Sn and Pb can be obtained in yields of 55 to 80% (Scheme 1). 

Using alkyllithium compounds, a distannane with a very long Sn—Sn bond, 3.03A, and a syw-peripheral conformation122 was prepared. Thus, reaction of di-t-butyl(chloro)2,4,6-triisopropylphenyl)tin, 78, with f-butyllithium gives 1,1,2,2-tetra-f-butyl-l,2-(2,4,6-triisopropylphenyl)ditin, 79, which displays a restricted rotation about the Sn—C bond as well as the Sn—Sn bond, even at high temperatures. 

Since alkyllithium compounds and their carbanions have an isoelectronic structure with alkoxides, their reaction behavior with carbenes is expected to be similar to that of alkoxides, showing enhanced reactivity in both C-H insertion and hydride abstraction.35 In this reaction, the hydride abstraction cannot be followed by recombination and, therefore, can be differentiated from the insertion. Indeed, the reaction of alkyllithium compounds 70 or nitrile anions (see Section IV.B) with ethyl(phenylthio)carbenoid, which is generated by the reaction of 1-chloropropyl sulfide 69 with BuLi, takes place at the -position of 70 more or less in a similar manner giving both insertion product 71 and hydride abstraction products 72 and 73, respectively. This again supports a general rule C-H bonds at the vicinal position of a negatively charged atom are activated toward carbene insertion reactions (Scheme 22). 

Aliphatic solvents, alkyllithium compounds and, 14 250-251 Aliphatic sulfonates, 26 145 Aliquot samples, 13 413-415 analysis of, 13 416 Aliskren, 5 158 Alitame, 12 42 24 232 Alite, phase in Portland cement clinker, 5 471, 472t, 473t Alitretinoin, 25 790 Alizarin, color of, 7 331 Alizarin derivatives, 9 337 Alizarin pure Blue B, 4 361t Alkadienes, metathesis of, 26 923 Alkali/alkaline-earth cation recognition,... 

Anionic guest inclusion compounds, 24 170 Anionic halide complexes, 24 540 Anionic initiators, 24 244-265 alkali metals, 24 245-248 alkyllithium compounds, 24 248-255 1,1-diphenylmethylcarbanions as,... 

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]. 

Abdul-Sada, A.K. Greenway, A.M. Sed-don, K.R. The Extent of Aggregation of Air-Sensitive Alkyllithium Compounds As Determined by Fast-Atom-Bombardment-MS. J. Organomet. Chem. 1989, 375, C17-C19. 

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. 

Plavsic, Srzic and Klasinc performed a detailed electron impact mass spectrometric investigation of alkyllithium compounds . They have concluded that MeLi, /-PrLi, 5-BuLi and r-BuLi consist of tetrameric clusters only, while n-PrLi, n-BuLi and i-BuLi form mixtures of tetramers and hexamers, in the gas phase. Fast atom bombardment (FAB) mass spectrometry was used by Abdul-Sada, Greenway and Seddon to show that the extent of aggregation of f-BuLi is tetrameric while n-BuLi is hexameric (Table 1). Nevertheless, for both alkyllithium compounds the ion corresponding to (RLi)Li+ is the most abundant in the spectrum, as also shown in other studies of alkyllithium vapor. 

In their papers Rodionov and coworkers described the polymerization of organolithium compounds in terms of the formation of lithium bonds (Scheme 1), analogous to hydrogen bonds, which brought about cyclic or linear association of these compounds in solution . However, the strong association of alkyllithium compounds, persisting even in the vapour phase, indicates that their association takes place through the formation of... 

When bidentate solvents are present, the clusters may crystallize forming linear polymers by linking clusters together, as in complexes 292-295. This further diminishes solubility and reactivity of the alkyllithium compound, making the unassociated RLi species the most probable reactive form in synthetic processes. MeLi dissolved in diethoxymethane shows at room temperature a single Li NMR peak, that resolves into four distinct peaks at —80°C, pointing to temperature-dependent monomer/oligomer/polymer equilibria . 

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