Ethyllithium

In some cases, however, the use of ethyllithium-diethyl ether-LiSr is to be... 

The lithiation of allene can also be carried out with ethyllithium or butyl-lithium in diethyl ether (prepared from the alkyl bromides), using THF as a cosolvent. The salt suspension which is initially present when the solution of alkyllithium is cooled to -50°C or lower has disappeared almost completely when the reaction between allene and alkyllithium is finished. 

C. The mixture was cooled to -70°C and the allene (0.22 mol) was added in 5-10 min while maintaining the temperature between -60 and -70°C. After stirring for an additional 30 min at -60°C the solution was ready for further conversions. In the raetallation with ethyllithium the salts initially present had disappeared almost completely after this period. During the lithiation with commercial butyl-lithium the reaction mixture was continuously homogeneous. The solution of the lithiated allenes should be kept below -60°C and used within a few hours. 

In some experiments the presence of hexane is undesirable in view of the volatility of the products. In these cases one can use butyllithium in pentane (prepared from butyllithium in hexane, by replacing the hexane with pentane see Exp. 10) or ethyllithium in diethyl ether, prepared from ethyl bromide and 11thiurn (see Exp. 1). 

To a solution of 0.30 mol of ethyllithium (note 1) in about 270 ml of diethyl ether (see Chapter II, Exp. 1) v/as added 0.30 mol of methoxyallene at -20°C (see Chapter IV, Exp. 4) at a rate such that the temperature could be kept between -15 and -2Q°C. Fifteen minutes later a mixture of 0.27 mol of >z-butyl bromide and 100 ml of pure, dry HMPT ivas added in 5 min with efficient cooling, so that the temperature of the reaction mixture remained below 0°C. The cooling bath was then removed and the temperature was allowed to rise. After 4 h the brown reaction mixture was poured into 200 ml of ice-water. The aqueous layer was extracted twice with diethyl ether. The combined solutions were washed with concentrated ammonium chloride solution (which had been made slightly alkaline by addition of a few millilitres of aqueous ammonia, note 2) and dried over potassium carbonate. After addition of a small amount (2-5 ml) of... 

Note 1. This relatively low yield is probably due to the difficult separation of hexane and the product. Better results can presumably be obtained if the lithiation of methoxyallene is performed with ethyllithium in diethyl ether (see Chapter 11, Exp. 1). 

A solution of 0.60 mol of ethyllithium (note 1) in about 400 ml of diethyl ether (see Chapter II, Exp. 1) was added in 30 min to a mixture of 0.25 mol of 1,4-diethoxy-2-butyne (see Chapter VIII-6, Exp. 8) and 100 ml of dry diethyl ether. The temperature of the reaction mixture was kept between -40 and -45°C. Fifteen minutes after the addition had been completed, 0.5 mol of methyl iodide was added at -40 C, then 100 ml of dry HMPT (for the purification see ref. 1) were added dropwise in 15 min while keeping the temperature at about -40°C. Thirty minutes after this addition the cooling bath was removed, the temperature was allowed to rise and stirring was continued for 3 h. The mixture was... 

To a solution of 0.50 tnol of ethyllithium in about 450 tnl of diethyl ether (see Chapter II, Exp. 1) was added 0.20 mol of 1-heptyne or butylallene (see Chapter VI, Exp. 1) with cooling below Q°C. After the addition the cooling bath was removed and the thermometer-gas outlet combination was replaced with a reflux condenser. The solution was heated under reflux for 6 h. The thermometer-gas outlet was again placed on the flask and the yellow suspension was cooled to -50°C. Trimethylchlorosilane (0.20 mol) was added dropwise in 10 min, while keeping the temperature between -40 and -35°C. After having kept the mixture for an additional 30 min at -30°C, it was poured into 200 ml of ice-water. The aqueous layer was extracted three times with small portions of diethyl ether. 

A suspension of di1ithiohexyne in diethyl ether was made from 0.20 mol of 1-hexyne and 0.5 mol ethyllithium in 400 ml of diethyl ether in the same way as described for 1-heptyne (see this chapter, Exp. 27). The suspension was cooled to -40°C and at this temperature a solution of 0.20 mol of ethylene oxide in 50 ril of diethyl ether was added in 15 min, the brown colour changing into yellow. Subsequently the temperature was allowed to rise graduallyduring 1 h to +5°C. 

A solution of 0.40 mol of ethyllithium in about 350 ml of diethyl ether (see Chapter II, Exp. 1) was transferred into the flask, which previously had been filled with nitrogen. The solution was cooled to -50°C and a cold solution (-30°C) of 0.43 mol of propyne in 50 ml of dry diethyl ether was added at a rate such that the temperature could be kept below -20°C. A solution of 0.45 mol of cyanogen chloride in 100 ml of diethyl ether, cooled at about 0°C, was then added in... 

Note 1. Butyl- or ethyllithium in diethyl ether, prepared from the alkyl bromide, contains LiBr, which may react with chlorine to form bromine, so that RCeC-Br will also be formed. 

A solution of (CH3)3C-CH=C=CLi, obtained by addition at -60°C of 0.20 mol of tert.-butylallene (see Chapter VI, Exp. 2) to a solution of 0.25 mol of ethyllithium in about 200 ml of diethyl ether (see Chapter II, Exp. 1) was warmed to 25°C and held at this temperature for 15 min. Subsequently the solution was cooled to below 0°C and 50 ml of saturated NH,C1 solution were added dropwise with vigorous stirring, keeping the temperature below 2o C. The upper layer v as separated off and the aqueous layer was extracted twice with 25-ml portions of diethyl ether. The combined solutions were dried over a small amount of magnesium sulfate. Slow distillation through a 40-cm Widmer column gave neopentyl acetylene (b.p. 76°C/750 mmHg, 20... 

To a solution of 0.05 mol of 4-phenyl-1,2-butadiene (see Chapter V, Exp. 19) was added in 10 min at -25 to -35°C a solution of 0.10 mol of ethyllithium in 80 ml of diethyl ether (see Chapter II, Exp. 1). After the addition the cooling bath was removed and the reaction mixture was warmed to 30 C in about 15 min and held at this temperature for an additional 15 min. The brown solution was then cautiously poured into 200 ml of ice-water. After separation of the layers four extractions with diethyl ether were carried out. The combined ethereal solutions... 

To a mixture of 0.20 mol of 1,1,4-triethoxy-2-butyne [see Chapter III, Exp. 40), 60 ml of dry THF and 50 ml of dry diethyl ether was added at -45 to -50°C a solution of 0.42 mol of ethyllithium in about 280 ml of diethyl ether (see Chapter II, Exp. 1). Stirring at -5o°C was continued for 30 min, then the reaction mixture was poured into 300 ml of saturated ammonium chloride solution. After shaking, the layers were separated and the aqueous layer was extracted twice with small portions of diethyl ether. The combined ethereal solutions were dried over magnesium sulfate and concentrated in a water-pump vacuum and the residue wasdistilled at about... 

Oq 1.4783, yield 84 ) was prepared by lithiating propargyl chloride with ethyllithium (see Chapter 11, Exp. 1 and 16) in diethyl ether and subsequently adding pivalyl aldehyde. 

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. 

Pentafluoroethanesulfonic acid (penrflic acid) is prepared by an improved procedure over previously reported methods through the use of pentafluoro-ethyllithium [64] (equation 31). 

In accord with the Felkin-Anh model, a-chiral ketones react more diastereoselectively than the corresponding aldehydes. Increasing steric demand of the acyl substituent increases the Cram selectivity. Due to the size of the acyl substituent, the incoming nucleophile is pushed towards the stereogenic center and therefore the diastereoface selection becomes more effective (see also Section 1.3.1.1.). Thus, addition of methyllithium to 4-methyl-4-phenyl-3-hexanonc (15) proceeds with higher diastercoselectivity than the addition of ethyllithium to 3-methyl-3-phenyl-2-pen-tanone (14)32. 

The enantiomerically pure (/ )- and (iS )-ketones are prepared from the corresponding enantiomer of mandelic acid by catalytic hydrogenation, treatment of the resulting hexahydroman-delic acid with ethyllithium, and subsequent introduction of the silyl protecting group33. 

Trimethylsilyloctan-4-ol. To a solution of vinyltrimethylsilane (6.77mmol) in THF (15 ml), cooled to -78°C, was added a solution of ethyllithium (8.8mmol, 1.15m in ether) with stirring. The mixture was stirred at -78 °C for 2h, warmed to -30°C over 1 h, and then cooled again to -78 °C. n-Butanal (7.5 mmol) was added, and then the reaction mixture was allowed to come to ambient temperature and stirred for 3 h. It was then partitioned between brine and ether. The layers were separated, and the organic layer was dried, concentrated and the residue distilled (oven temperature 120 °C) to give the /i-hydroxysilane (6.3 mmol, 89% based on n-butanal), as a 2 1 mixture of threo and erythro diastereoisomers. 

Enolate generation, 106-7 Enolate trapping, 99-101 Enones, 34-5 Epoxidation, 21-3 a/3-Epoxysilanes, 21-4, 78 -Ethoxy acylsilane, 110 1-Ethoxy-l-trimethylsilyloxycyclo-propane,133 Ethyl bromoacetate, 123 Ethyl 2-chloropropanoate, 133 Ethyl glycinate, 87,88-9 Ethyl m-nitrobenzene, 137 Ethyl irimethylsilylacetate. 71, 123-4, 134 Ethyllithium, 66... 

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