Temperature lithiated carbons

While the rationale for the above order remains to be well-understood, the authors speculated that the relative effectiveness and solubility of the SEI as well as the reactivity of these bulk solvents might be responsible.Overall, this study showed that the reaction between the electrolyte and the lithiated carbon could trigger thermal runaway, except at much higher onset temperatures than those of lithium electrodes. 

With this acetal, instead of hydrolyzing the intermediate benzyllithium, one can let it warm to room temperature, and an internal nucleophilic substitution takes place, whereby the acetal moiety behaves as a leaving group, and a trans-disubstituted cyclopropane is formed in 60-70% yield [39,41]. The first-formed stereogenic center remains unaffected in this second step, whereas the benzylic lithiated carbon is able to epimerize [38,39], leading to the more stable trans-cyclopropane [42-44] (Scheme 20). 

In case of an inerease in operating temperature with a strong current or because of poorly-eontrolled or uncontrolled environmental conditions, the phenomenon leading to thermal runaway is linked primarily to the deeomposition of the SEI of the lithiated carbon electrode, leaving exposed the electrode, whieh deeomposes by reaction between the inserted lithium and the eleetrolyte. Gas formation occurs, once again leading to an increase in the internal pressure of the element. 

Following the thermal behavior of lithiated carbons in electrolyte solutions clearly shows that there are three stages in the reactions developed in these systems as the temperature is raised. 

A solution of 0.10 mol of lithiated methoxyallene in about 70 ml of hexane and 50 ml of THF (see Chapter II, Exp. 15) was cooled to -40°C. Ory, pure acetone (0.12 mol) was added dropwise during 10 min, while keeping the temperature at about -30°. Five minutes after the addition 100 ml of saturated NHi,Cl solution, to which 5 ml of aqueous ammonia had been added (note 1), were run in with vigorous stirring. The product was extracted three times with diethyl ether. The combined organic solutions were dried over potassium carbonate and subsequently... 

Chiral 2-oxazolidones are useful recyclable auxiliaries for carboxylic acids in highly enantioselective aldol type reactions via the boron enolates derived from N-propionyl-2-oxazolidones (D.A. Evans, 1981). Two reagents exhibiting opposite enantioselectivity ate prepared from (S)-valinol and from (lS,2R)-norephedrine by cyclization with COClj or diethyl carbonate and subsequent lithiation and acylation with propionyl chloride at — 78°C. En-olization with dibutylboryl triflate forms the (Z)-enolates (>99% Z) which react with aldehydes at low temperature. The pure (2S,3R) and (2R,3S) acids or methyl esters are isolated in a 70% yield after mild solvolysis. 

The temperature at which a cycloaddition reaction of a neopentylsilene takes place (detected by the elimination of LiCl) has turned out to be dependent on the reaction partners added as substrate. This implies that an interaction between the substrate and A or B or the substrate and C occurs somewhere along the reaction pathway depicted above. For the system Cl3SiCH=CH2/LiBut/R2C=NR it was observed that the imine initiates and supports the salt elimination from the species A/B. Based on the knowledge that silenes are stabilized by external donors [1] we conclude that with carbon unsaturated compounds x-donor interactions instead of cr-donor complexes may be possible as well for the lithiated species (D) as for the silene itself (E). 

Fluorinated carbonates were also used by Smart et al. as low-temperature cosolvents (Table 12), in the hope that better low-temperature performances could be imparted by their lower melting points and favorable effects on SEI chemistry. Cycling tests with anode half-cells showed that, compared with the ternary composition with nonfluorinated carbonates, these fluorinated solvents showed comparable and slightly better capacity utilizations at room temperature or —20 °C, if the cells were charged at room temperature however, pronounced differences in discharge (delithiation) capacity could be observed if the cells were charged (lithiated) at —20 °C, where one of these solvents, ethyl-2,2,2-trifluoroethyl carbonate (ETFEC), allowed the cell to deliver far superior capacity, as Figure 63 shows. Only 50% of the capacity deliverable at room temperature was... 

Only the most reactive organolithium compound, e.g. f-BuLi, is able to attack the carbon-nitrogen triple bond at temperatures below —20°C. For the other less reactive species, namely PhLi and n-BuLi, higher temperatures in ordinary solvents like pentane would be more appropriate to synthesize their lithiated Schiff bases. Flowever, for their detection IR spectroscopy seems to be unsuitable, since the relevant C=N stretching mode will be hidden by strong CH deformation modes of the solvent. 

The naphthalene-catalyzed (2.5%) lithiation of phthalan 330 (or its substituted derivatives ) in THF at room temperature allowed the preparation of the functionalized benzyllithium intermediate 331, which reacted with electrophiles at —78°C to give, after hydrolysis, the corresponding functionalized benzyl alcohols 332 (Scheme 97). When carbon dioxide was used as the electrophilic reagent, the corresponding 5-lactone was directly obtained . When carbonyl compounds were used as electrophiles, the cyclization of the resulting products 332 under acidic conditions (85% H3PO4) allows the synthesis of substituted isochromans. 

When 2,2-diphenyl-l,3-dioxolane (410, R = Ph) was lithiated with lithium and a catalytic amount of naphthalene (4%) in THF at —40°C (see Section VI.F.l) and then reacted with an aldehyde as electrophile, intermediates 437 were generated. The further lithiation of these compounds at the same temperature cleaved the second benzylic carbon-oxygen bond giving new organolithium intermediates 438, and a second electrophile could be introduced to give 439, after hydrolysis. In these products, two different electrophilic fragments have been incorporated, so the starting material behaves as the 1,1-diphenylmethane dianion synthon (Scheme 122) °. 

The generation of 1,2-dUithioalkanes by a double chlorine-lithio exchange is not possible, because after the first lithiation the chloro-lithio intermediate suffers spontaneously -elimination, even at temperatures as low as — 100°C3°3. However, when one of the two chlorine atoms is attached to a sp -hybridized carbon atom, as... 

Dilithium compound 210, obtained from the lithiation of hexasilylfulvene 209 in THF at room temperature (Scheme 72), represents the first X-ray structural analysis of a dUithi-ated fulvene derivative. In the solid state, one lithium centre is capping the central five-membered ring, while the second lithium centre is located at the exocyclic carbon atom of the fulvene unit (Figure 27) . 

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