Ethers lithium bromide

A solution of 0.21 mol of butyllithium in about 140 ml of hexane (note 1) was cooled below -40°C and 90 ml of dry THF ivere run in. Subsequently a cold (< -20 C) solution of 0.25 nol of propyne in 20 ml of dry THF was added with cooling below -20°C and a white precipitate was formed. A solution of 0.10 mol of anhydrous (note 2) lithium bromide in 30 ml of THF was added, followed by 0.20 mol of freshly distilled cyclopentanone or cyclohexanone, all at -30°C. The precipitate had disappeared almost completely after 20 min. The cooling bath was then removed and when the temperature had reached 0°C, the mixture was hydrolyzed by addition of 100 ml of a solution of 20 g of NHi,Cl in water. After shaking and separation of the layers four extractions with diethyl ether were carried out. The extracts were dried over magnesium sulfate and the solvents removed by evaporation in a water--pump vacuum. Careful distillation of the remaining liquids afforded the following... 

In the flask were placed 0.40 mol of dry, powdered copper(I) cyanide, 9 g of anhydrous lithium bromide (note 1), 50 ml of dry THF and 0.30 mol of l-bromo-2--heptyne (prepared from the corresponding alcohol and PBrs in diethyl ether, see VIII-2, Exp. 10). The mixture was heated until an exothermic reaction started, which occurred at about 80°C. The solid dissolved gradually. The mixture was kept... 

Ethereal methyl1ithiurn (as the lithium bromide complex) was obtained by the submitters from Aldrich Chemical Company Inc. The checkers used 1.19 M methyl1ithiurn-lithium bromide complex in ether supplied by Alfa Products, Morton/Thiokol, Inc. The concentration of the methyllithium was determined by titration with 1.0 M tert-butyl alcohol in benzene using 1,10-phenanthroline as indicator. The submitters report that ethereal methyllithium of low halide content purchased from Alfa Products, Morton/Thiokol, Inc., gave similar results. 

Although ethereal solutions of methyl lithium may be prepared by the reaction of lithium wire with either methyl iodide or methyl bromide in ether solution, the molar equivalent of lithium iodide or lithium bromide formed in these reactions remains in solution and forms, in part, a complex with the methyllithium. Certain of the ethereal solutions of methyl 1ithium currently marketed by several suppliers including Alfa Products, Morton/Thiokol, Inc., Aldrich Chemical Company, and Lithium Corporation of America, Inc., have been prepared from methyl bromide and contain a full molar equivalent of lithium bromide. In several applications such as the use of methyllithium to prepare lithium dimethyl cuprate or the use of methyllithium in 1,2-dimethyoxyethane to prepare lithium enolates from enol acetates or triraethyl silyl enol ethers, the presence of this lithium salt interferes with the titration and use of methyllithium. There is also evidence which indicates that the stereochemistry observed during addition of methyllithium to carbonyl compounds may be influenced significantly by the presence of a lithium salt in the reaction solution. For these reasons it is often desirable to have ethereal solutions... 

To a solution of 2 g. of rhodium(III) chloride trihydrate in 70 ml. of ethanol is added 12 g. of triphenylphosphine in 250 ml. of hot ethanol. After refluxing until the red solution begins to lighten in color (about 5 minutes), 8 g. of lithium bromide dissolved in 50 ml. of hot ethanol is added and the mixture refluxed for an hour. The orange prisms of the complex are collected by filtration, washed with 50 ml. of anhydrous ether, and dried in vacuum yield 5.1 g. (64% based on rhodium). 

The combination of equimolar amounts of tris(trimethylsilyl)methyllithium and zinc bromide in a THF/diethyl ether mixture, Scheme 27, furnished tris(trimethylsilyl)methylzinc bromide, as a lithium bromide/ether adduct.43 The compound, which may also be formulated as a lithium alkyldibromozincate, showed no ligand redistribution reactions. It is monomeric in solution and can be treated with 1 equiv. of an organolithium reagent to afford heteroleptic diorganozinc compounds. 

Ethyl (2Z)-3-bromopropenoate. To a three-necked, round-bottomed flask are added lithium bromide (10.0 g, 0.115 mol, Note 1), acetonitrile (100 mL, Note 2), acetic acid (7.0 g, 0.116 mol, Note 3), and ethyl 2-propynoate (9.0 g, 0.092 mol, Notes 4, 5) under nitrogen. The reaction is carried out with magnetic stirring under reflux and monitored by GLC (Note 6). The reaction is complete after 24 hr. The reaction is cooled, water (20 mL) is added to the flask, and the mixture is cautiously neutralized with solid potassium carbonate, added in portions (Note 3). The organic layer is separated, and the aqueous layer Is extracted with ether (3 x 20 mL) (Note 3). The combined organic layers are dried with magnesium sulfate and filtered. After removal of the solvent, ethyl (2Z)-3-bromopropenoate is obtained by vacuum distillation (14.0 g, yield, 85%, Note 7). 

Bromobenzotellurophene ° A mixture of 2.0 g (19.6 mmol) of phenylacetylene, 1.0 g (6.3 mmol) of tellurium dioxide, 2.0 g (23 mmol) of lithium bromide aud 50 uiL of acetic acid is heated uuder reflux for 20 h, cooled to 20°C, aud poured iuto 150 uiL of diethyl ether. Aqueous sodium hydrogeu carbouate solutiou (5%) is added uutil all the acid has beeu ueutralized. The orgauic phase is separated, dried with auhydrous calcium chloride, fdtered aud evaporated. The browu, oily residue is dissolved iu a mixture of 30 mL of carbou tetrachloride aud 10 mL of petroleum ether (b.p. 30 0°C). Chloriue is carefully bubbled through this solutiou uutil precipitatiou of the product ceases. The yellow precipitate is filtered and recrystallized from acetonitrile. Yield 2.2 g (92%) m.p. 263-265°C. 

Preparation of 3,5-dimethyl-4-(trifluoromethyl)-2,5-heptadien-4-ol. A 1-L, three-necked, round-bottomed flask, equipped with a reflux condenser, a magnetic stir bar and an addition funnel is flame dried under an atmosphere of argon. After the apparatus has cooled, 350 mL of anhydrous diethyl ether (freshly distilled from sodium benzophenone10 under argon) is added. Lithium wire (6.9 g, 1.0 mol, 3.2-mm diameter, 0.01% Na content, Aldrich Chem. Co., Milwaukee, WI), which is cut into 5- to 10-mm pieces and washed with hexanes, is added to the flask under a counterstream of argon gas. The reaction flask is cooled to 0°C in an ice bath and 68.9 g (0.51 mol) of 2-bromo-cis-2-butene (prepared in the previous step9) in 50 mL of anhydrous diethyl ether is added dropwise over a 45-min period while the reaction mixture is stirred. The reaction solution becomes cloudy due to the formation of lithium bromide. Stirring is continued for an additional 1.5-2 h at 0°C. 

Chlorotrimethylsilane (2.7 g, 25 mmol) (1) (CAUTION) is added to a solution of lithium bromide (1.74g, 20 mmol) in dry acetonitrile (20 ml) (2) with good stirring under a nitrogen atmosphere. Cinnamyl alcohol (1.34 g, 10 mmol) is then added and the reaction mixture heated under reflux for 12 hours. The progress of the reaction is monitored by t.l.c. on silica gel plates with hexane as the eluant. On completion of the reaction (12 hours), the reaction mixture is taken up in ether (50 ml), washed successively with water (2 x 25 ml), sodium hydrogen carbonate solution (10%, 50 ml) and finally brine, and dried over anhydrous sodium sulphate. Evaporation of the ether affords the pure bromide in 93 per cent yield. The product may be recrystallised from ethanol and has m.p. 31-32 °C CAUTION this compound is lachrymatory. 

Tetraphenyl Tellurium1 3.53 g (10 mmol) of diphenyl tellurium dichloride are suspended in 30 ml of anhydrous diethyl ether and, under dry nitrogen, 25 ml (26 mmol) of a lithium bromide-free solution of phenyl lithium in diethyl ether are added. Crystals of tetraphenyl tellurium are filtered off, the filtrate is concentrated, the concentrate is cooled to — 10°, and the precipitated product is collected. The combined crystals are dissolved in benzene, the solution is filtered, and the filtrate is evaporated to dryness under reduced pressure. The residue is recrystallized from 35 ml of anhydrous diethyl ether yield 2.3 g (52%) m.p. 104-106° (dec.). 

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