Lithiated carbon

All the investigations that have been performed so far suffer from the fact that the deprotonation of the imines by strong bases gives metalation—after which an electrophilic reaction takes place on the less substituted a-carbon. Lithiation that does not depend on the degree of substitution on the a-carbon was developed by Wender and co workers3 9,40 using a,/ - unsaturated ketones 23 via 24, 25 and the lithium salt 26 (equation 7) or primary allyl imines via 29, 30 and the lithium salt 31 (equation 8). The products 27 and 32 are obtained after alkylation and hydrolysis. 

In fact, the ability of layer-structured carbon to insert various species was well known by the latter half of the 1800s. The ability of graphite to intercalate anions promoted exploration into the use of a graphite cathode for rechargeable batteries. Juza and Wehle described carbon lithiation studies in the middle of last century. ... 

Note 1. The lithiation of monoalky1al 1 enes is not completely regiospecific. The ratio of a- to ylithiated allene varies from about 80 20 for methyl-allene to 93 7 for hexylallene. tert.-Butylallene, however, is metallated exclusively on the terminal carbon atom. 

A solution of 0.20 mol of butyl lithium in about 140 ml of hexane was cooled to -6Q°C and 140 ml of dry THF were added. The mixture was cooled to about -80 C (liquid nitrogen bath) and 0.23 mol of the allenic hydrocarbon (see Chapter VI, Exp. 1, 2, 44) was added in 5 min (methylal1ene was added as a 1 1 solution in THF). The solutions were kept for 1 h at -55°C. Into another 1-1 flask (see also Fig. 1, but without a dropping funnel), cooled at -90°C by immersion in liquid nitrogen, was poured a solution of dry carbon dioxide (from a cylinder) in 130 ml of dry THF. This solution was obtained by introducing about 40 g of carbon dioxide (note 1) into the THF at -90°C. The gas inlet was removed from the second flask and the solution of the lithiated allene (still cooled below -60 C) was poured... 

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. 

Propargylic alcohol, after lithiation, reacts with CO2 to generate the lithium carbonate 243, which undergoes oxypalladation. The reaction of allyl chloride yields the cyclic carbonate 244 and PdC. By this reaction hydroxy and allyl groups are introduced into the triple bond to give the o-allyl ketone 245[129]. Also the formation of 248 from the keto alkyne 246 with CO2 via in situ formation of the carbonate 247 is catalyzed by Pd(0)[130]. 

Other large monocarbaboranes include /<7( -6-(NR3)-6-CB2H [f/oj o-l-CB H J [38192-43-7] and closo-C ]H. ][ [39102-46-0]. The closo monocarbaboranes can be functionalized at carbon via lithiation using reagents such as -butyl lithium in a manner similar to the dicarbaboranes. The small monocarbaboranes /oj o-l-CB H [25301-90-0], nido-2-C [12385-35-2], and a variety of their alkylated derivatives are also known (127,128). 

Competitive metallation experiments with IV-methylpyrrole and thiophene and with IV-methylindole and benzo[6]thiophene indicate that the sulfur-containing heterocycles react more rapidly with H-butyllithium in ether. The comparative reactivity of thiophene and furan with butyllithium depends on the metallation conditions. In hexane, furan reacts more rapidly than thiophene but in ether, in the presence of tetramethylethylenediamine (TMEDA), the order of reactivity is reversed (77JCS(P1)887). Competitive metallation experiments have established that dibenzofuran is more easily lithiated than dibenzothiophene, which in turn is more easily lithiated than A-ethylcarbazole. These compounds lose the proton bound to carbon 4 in dibenzofuran and dibenzothiophene and the equivalent proton (bound to carbon 1) in the carbazole (64JOM(2)304). 

Introduction of an iodine to C-2 of indole can be accomplished using lithium derivatives. Since direct iodination tends to give mixtures it is essential to activate the 2-position at the expense of the inherently more reactive 3-position. This has been done by lithiating 1-f-butoxycarbonylin-doles (25) and then converting them into iodo derivatives before deprotection (85JHC505) (Scheme 19). Alternatively carbon dioxide can be used... 

During electrochemical reduction (charge) of the carbon host, lithium cations from the electrolyte penetrate into the carbon and form a lithiated carbon Li rCn. The corresponding negative charges are accepted by the carbon host lattice. As for any other electrochemical insertion process, the prerequisite for the formation of lithiated carbons is a host material that exhibits mixed (electronic and ionic) conductance. 

The electrochemical performance of lithiated carbons depends basically on the electrolyte, the parent carbonaceous material, and the interaction between the two (see also Chapter III, Sec.6). As far as the lithium intercalation process is concerned, interactions with the electrolyte, which limit the suitability of an electrolyte system, will be discussed in Secs. 5.2.2.3,... 

Apart from manifold structures, carbons can have various shapes, forms, and textures, including powders with different particle size distributions, foams, whiskers, foils, felts, papers, fibers [76, 77], spherical particles [76] such as mesocarbon microbeads (MCMB s) [78], etc. Comprehensive overviews are given, for example in [67, 71, 72], Further information on the synthesis and structures of carbonaceous materials can be found in [67, 70, 72, 75, 79]. Details of the surface composition and surface chemistry of carbons are reviewed in Chapter II, Sec. 8, and in Chapter III, Sec. 6, of this handbook. Some aspects of surface chemistry of lithiated carbons will also be discussed in Sec. 5.2.2.3. 

The first lithiated graphitic carbons (lithium-graphite intercalation compounds, abbreviated as Li-GIC s),... 

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