Lithium bromide preparation

After the air in the flask had been completely replaced with nitrogen, it was cooled in a liquid nitrogen bath and a solution of 25 g of acetylene in 160 ml of dry THF was introduced. The solution had been prepared by dissolving acetylene (freed from acetone by means of a cold trap) in THF cooled at -80 to -90°C. A solution of 0.21 mol of butyl lithium in about 150 ml of hexane was added in 5 min to the vigorously stirred solution. During this addition the temperature of the mixture was kept between -80 and -100°C by occasionally dipping the flask into the liquid nitrogen. To the white suspension were successively added at -80°C a solution of 10 g. of anhydrous lithium bromide (note 1) in 30 ml of THF and 0.20 mol of freshly distilled benzaldehyde. The reaction mixture was kept for 3 h at -69°C, after which the temperature was allowed to rise to +10°C over a period of 2 h. 

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... 

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... 

Metal halide salts other than sodium iodide have been used sparsely to prepare halodeoxy sugars from sulfonate esters. Lithium chloride (107) and lithium bromide (33) have found limited application. Potassium fluoride (dihydrate) in absolute methanol has been used (51, 52) to introduce fluorine atoms in terminal positions of various D-glucose derivatives. The reaction is conducted in sealed tube systems and requires... 

When 2,2-dimethylpropanal is used to prepare the azomethine moiety, the corresponding azaallyl anion may be obtained when l,8-diazabicyclo[5.4.0]undec-7-ene/lithium bromide is used as base. The subsequent addition to various enones or methyl ( )-2-butenoate proceeds with anti selectivity, presumably via a chelated enolate. However, no reaction occurs when triethylamine is used as the base, whereas lithium diisopropylamide as the base leads to the formation of a cycloadduct, e.g., dimethyl 5-isopropyl-3-methyl-2,4-pyrrolidinedicarboxylate using methyl ( )-2-butenoate as the enone84 89,384. 

US patent 6,677,453, Production of polymorphic forms I and II of finasteride by complexation with group I or II metal salts [97]. Finasteride Form I of was prepared by first forming a substantially insoluble complex of the compound and a Group I or Group II metal salt (such as lithium bromide), and then dissociating the complex by dissolving away the salt component with water to obtain substantially pure crystalline finasteride Form I. 

The method is similar to that for the chloride except that lithium bromide is added to the preparation. 

Phenyl(p-methoxyphenyltelluro)acetylene (typical procedure To a solution of lithium phenylacetylide (20.0 mmol), prepared as described above, is added dropwise a solution of p-methoxyphenyltellurenyl bromide (prepared by adding bromine (1.60 g, 10.0 mmol)) in benzene (5 mL) to a solution of the corresponding ditelluride (4.69 g, 10 mmol) in THF (10 mL) at 0°C under Nj. The reaction mixture is stirred for 1 h at room temperature and then treated as described above to give the product (4.90 g (73%)), which is recrystallized from EtOH (m.p. 71-72°C). 

Lithium bromide is prepared by neutralizing lithium hydroxide or hthium carbonate with an aqueous solution of hydrobromic acid, followed by concentration and crystallization ... 

Preparation of Alkynenitriles by Reaction of l-Bromoalkynes with Copperd) Cyanide in the Presence of Lithium Bromide... 

A heterogeneous mixture of lithium tribromodicuprate(I) (6.0 mmol), prepared by adding 2.4 mL (6.0 mmol) of a 2.5 M solution of dry lithium bromide in THF to 1.72 g (12.0 mmol) of copper(I) bromide in 2.5 mL of THF under nitrogen, is added to a solution of 5.0 mmol of l-methylsulfonyloxy-l-pbenyl-2-propyne (100% ee) in THF immediately after its preparation in situ as follows ... 

Subsequent work on the deuteration and methylation of (methylsulfinylmethyl)benzene showed indeed that the proportions of the diastereomers produced depend on many factors. The 15 1 diastereomeric mixture of (rnethvlsulfinylmethyl-J) benzene from the deuteration with re-tention/methylation with inversion of (methylsulfinylmethyl)benzenc result45 was obtained in THK with methyllithium prepared from chloromethane (low content of lithium salts). When the methyllithium w as prepared from bromomethane (one equivalent of lithium bromide is present in the mixture), the ratio was reduced to 3 151. The same effect was produced by addition of one equivalent of lithium bromide to the reaction mixture prior to the addition of methyllithium prepared from chloromethane. Excess of lithium bromide reverses the ratio to 0.45 1. 

Recently a practical and convenient synthesis was described starting from linalool via linalyl acetate [8]. It involves the ene-type chlorination of linalyl acetate prepared from linalool which results in the formation of y-chloro-a-linalyl acetate (Scheme 13.8). Dehydrochloronation with lithium bromide and lithium carbonate in dimethylformadide followed by hydrolysis of dehydro-a-linalyl ac-ylate results in hotrienol. 

Dibromopropan-l-ol has been prepared by reaction of allyl alcohol, bromine, and aqueous lithium bromide (Jenkner Rabe, 1967 Thomas Levek, 1972). 

Lithium bromide also combines with gaseous ammonia to form four solid deliquescent substances. The monammine, [Li(NH3)]Br, is formed above 95° C. the diammine, [Li(NIi3)2]Br, between 87° and 95° C. the triammine, [Li(NH3)3]Br, between 71° and 87° C. and the tetrammine about —18° C.2 Ephraim prepared other ammino-salts of lithium, as, for example, tetrammino-lithium nitrate, [Li(NH3)J(N03), which is a colourless syrup at ordinary temperature and is more stable than the chloride tetrammino-lithium chlorate, [Li(NII3)Ll]C103, which is a fairly mobile liquid and tetrammino-lithium perchlorate, [Li(NH3)4]C104, a white solid which liquefies and decomposes at ordinary temperature.3... 

Eluent solution (DMF +0.1M LiBr) for GPC analysis was prepared with HPLC grade dimethylformamide (Burdick and Jackson) and lithium bromide (Fisher Scientific Co.), which were used without further purification. 

The preparation oi the alkali bromides.—While V. Merz and W. Weith 2 found that metallic sodium reacts very slowly with bromine such that even after the two elements have been kept for 8 hrs. at 200°, the conversion of sodium into the bromide is but superficial potassium, caesium, and rubidium unite with bromine more quickly, forming the alkali bromide. The bromides are also formed when hydro-bromic acid is neutralized with the alkali hydroxide or carbonate, and the soln. evaporated. This method, for example, has been used for preparing rubidium bromide, RbBr. C. Chaubrie and N. N. Beketofi made a soln. of caesium bromide, CsBr, by the double decomposition of caesium sulphate, and barium bromide. P. Klein 3 made lithium bromide by digesting calcium bromide with lithium carbonate... 

Ortho-lithiated halobenzenes, prepared by lithium-bromide exchange, undergo rapid benzyne formation at -30, -40, and -50°C for bromo, chloro, and fluoro derivatives [57JA(79)2625]. They normally require... 

Procedure. Equation 1 indicates that it is necessary to determine the concentration, resistance, dielectric constant, viscosity, and temperature of the system. These data were acquired for five different solvent systems. A series of measurements, in which the concentration of lithium bromide was varied from about 10 5N to 10 3N, was made on each system. The solvents used were acetone (I), 0.02063m bromosuccinic acid in acetone (II), 0.05009m bromosuccinic acid in acetone (III), 0.09958m bromosuccinic acid in acetone (IV), and 0.05047m dimethyl bromosuccinate in acetone(V). Each solvent was used to prepare stock solutions of 10-2 and 10 3m lithium bromide. All mixed solvents and solutions were prepared in the dry box. 

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