Lithium bromide-methanol solutions

In 1910 Serkov (15) determined the conductance of several salts (including lithium bromide) at 25°C in water, methanol, ethanol, acetone, and binary mixtures of these solvents, reporting a value of 144 12 1 cm2 eq-1 for Ao for lithium bromide in acetone. He found that, unlike the other mixtures, acetone solutions exhibit no parallelism between conductance and fluidity, and concluded that when the surveyed ionophores are dissolved in acetone, the complexity of the solvates formed increases as Aq for the ionophores decreases. 

Silicon tetrachloride (Aldrich, 99.998%), allylamine (Aldrich, 99.8%), lithium aluminum hydride solution (1.0M in tetrahydrofuran, Aldrich), toluene (Aldrich, 99.8%, dehydrated), methanol (Aldrich, 99%), hydrogen hexachloroplatinate (Aldrich, 99.995%), isopropyl alcohol (Aldrich, 99.5%, anhydrous), sodium boro-hydride (Fluka) and tetraoctylammonium bromide (TOAB) (Sigma, 99%) were purchased from Sigma-Aldrich and used without further purification. 

Stock solutions of lithium bromide and of the five Lewis bases are prepared in the concentration range 0.05-0.1 g mP in methanol. The working ESI solution is obtained by dilution of 2 to 8 pi of LiBr stock solution and two competing ligand stock solutions in 1 ml of methanol, to obtain respective concentrations in the range (1-5) x 10 mol 1 . The final concentration is not critical but may be adjusted according to the instrument and the ESI source conditions so as to obtain an optimum intensity of the cation bound dimer [L1 M+-l2]. 

Lithium mesitylhydroborate was prepared by reaction of mesitylmagnesium bromide with trimethoxyborane and subsequent reduction with LiAlH4. The polymerization was performed by adding a THF solution containing a slight excess of lithium mesitylhydroborate to oligo(ethylene oxide) in THF. After treatment with alcohol, the lithium borate polymers were obtained as transparent soft solids soluble in methanol, THF, and chloroform. 

B (Alternative) 20 g of the unrefluxed precipitate (ethyl-ester of (1)) from last part of step A in 100 ml ether. Add dropwise to a solution of 4 g lithium aluminum hydride in 900 ml ether at 0°. Reflux three hours and isolate the resulting tryptophol as described earlier. Dissolve 3 g of the tryptophol in 140 ml ether and stir at 0°. Add dropwise 1.8 g PBr3 in 30 ml ether and let stand sixteen hours at room temperature. Decant the ether and wash the precipitate with ether. Wash ether w ith water, NaHC03 and water, and dry, evaporate in vacuum the ether to get the bromide (recrystallize-ethanol). 2 g of the bromide and 1.5 g piperidine (or equimolar amount DEA. etc.) in 65 ml methanol and heat in sealed tube fifteen... 

The third synthetic route reported by Husson and co-workers 140) is as follows Amino nitrile 472 obtained from the ketal (471) was converted to the 2,6-dialkylpiperidine (473) by catalytic hydrogenation followed by alkylation with lithium diisopropylamide and pentyl bromide. Refluxing a solution of 473 in methanol containing hydrochloric acid led to the formation of 9-benzyladaline (475) in 90% yield. Debenzylation of 475 gave d/-adaline (107) in nearly quantitative yield (Scheme 59) 140). 

Methyl triphenyl phosphonium bromide (0.56 mmol) was dissolved in 10 ml of THF and treated with 1.6 M -butyl lithium (0.64 mmol) in hexane solution at 0°C. The solution was stirred for 30 minutes at 0°C and then treated with the step 2 product (0.36 mmol) and stirred an additional 2 hours at ambient temperature. The solution was treated with dilute hydrochloric acid, extracted with chloroform, dried over MgSC>4, and concentrated. The residue was purified by silica gel column chromatography using chloroform/hexane, 2 1, respectively, recrystallized using CH2CI2/ methanol, and 100 mg of product isolated. 

Note Highly polar solvent sweet, ethereal odor soluble in water flammable, burns with a luminous flame highly toxic by ingestion, inhalation and skin absorption miscible with water, methanol, methyl acetate, ethyl acetate, acetone, ethers, acetamide solutions, chloroform, carbon tetrachloride, ethylene chloride, and many unsaturated hydrocarbons immiscible with many saturated hydrocarbons (petroleum fractions) dissolves some inorganic salts such as silver nitrate, lithium nitrate, magnesium bromide incompatible with strong oxidants hydrolyzes in the presence of aqueous bases and strong aqueous acids. Synonyms methyl cyanide, acetic acid nitrile, cyanomethane, ethylnitrile. 

The industrial production of Crixivan (9 H2S04) took advantage of the chirality of (IS,2R)-aminoindanol to set the two central chiral centers of 9 by an efficient diastereoselective alkylation-epoxidation sequence.17 The lithium enolate of 12 reacted with allyl bromide to give 13 in 94% yield and 96 4 diastereoselective ratio. Treatment of a mixture of olefin 13 and V-chlorosuccinimide in isopropyl acetate-aqueous sodium carbonate with an aqueous solution of sodium iodide led to the desired iodohydrin in 92% yield and 97 3 diastereoselectivity. The resulting compound was converted to the epoxide 14 in quantitative yield. Epoxide opening with piperazine 15 in refluxing methanol followed by Boc-removal gave 16 in 94% yield. Finally, treatment of piperazine derivative 16 with 3-picolyl chloride in sulfuric acid afforded Indinavir sulfate in 75% yield from epoxide 14 and 56% yield for the overall process (Scheme 24.1).17-22... 

The cyclic vinyl ether 2,3-dihydro-1,4-dioxin is converted into its cyclic hemiacetal hydration product, tetrahydro-2-hydroxy-1,4-dioxin, in aqueous solution by an acid-catalyzed reaction <870K2746, 89JP043). Treatment of an alcohol with excess of 2,3-dihydro-1,4-dioxin at room temperature in the presence of copper(II) bromide in tetrahydrofuran leads to the corresponding acetal. This new protective group for alcohols, which is stable towards lithium aluminum hydride and organolithium reagents, can be removed by treatment with acidified aqueous methanol <85S806>. 

Lithium organocupmtes. House et al. have found that certain undesirable side reactions in the preparation of lithium organocuprates can be minimized by use of this complex rather than commercial cuprous bromide itself, which apparently contains some impurities. The complex is readily prepared in 90% yield from (CH3)2 S and CuBr. It is insoluble in ether, hexane, acetone, methanol, and water, but dissolves in several solvents in the presence of excess (CH3)2S. Thus a solution of the complex in ether and (CH3)2S is used the excess sulfide is readily separated from reaction products. The soluble copper reagent t-BuC CCu can also be used instead of CuBr, but the precursor, t-butylacetylene, is expensive. The use of the complex was illustrated for reactions of (CH3)2CuLi and (CH2=CH)2CuLi. 

To a suspension of 77.7 mg 4-amino-l-(3,4-dihydroxy-5-hydroxymethyltetra-hydrofuran-2-yl)-lH-pyrimidin-2-one 3-oxide (cytidine -oxide, 0.30 mmol) and 12.6 mg 95% pure lithium hydride (1.5 mmol) in 5 mL dry methanol was added 40 /xL 98% pure benzyl bromide (0.33 mmol) the mixture was stirred at 37°C for 1 day under an argon atmosphere. TLC analysis of the reaction mixtures with chloroform/methanol/acetic acid (16 6 3) and chloroform/methanol (10 1) as the developing solvents showed complete consumption of the starting material for almost quantitative conversion to a less polar compound. After being neutralized with 1 N HCl solution and subsequent removal of the solvent under reduced pressure, the resulting residue was subjected to a short silica gel column by eluting with chloroform/methanol (20 1) to isolate 99.5 mg l-(3,4-dihydroxy-5-hydroxymethyltetrahydrofuran-2-yl)-17/-pyrimidin-2,4-dione 4- 0-benzyl oxime (uridine 4-0-benzyloxime) as a colorless amorphous powder, in a yield of 95%, m.p. 123-125°C (from methanol). 

Following a procedure similar to Dileone s, we have reacted diepoxides, including BADGE, with MDI. The catalysts used were lithium butoxide and tetraethylammonium bromide. Products were isolated by additions to the DMF solution of first water and then, in some reactions, methanol. 

Addition methods were used for the determination of m-saturated compounds and olefins. The methods are based on the additions of bromine to unsaturated bonds, and the waves for the brominated compounds corresponding to the reduction of o, j8-dibromides (involving elimination) are measured. Their heights are proportional to the concentration of the unsaturated compound. Thus vinylchloride and 1,2-dichloroethylene were transformed into l-chloro-l,2-dibromoethane and l,2-dichloro-l,2-dibromoethane, by the action of a 3 M solution of bromine in methanol saturated with sodium bromide. The excess of bromine was removed with ammonia and the polarographic analysis was performed with sodium sulphite or lithium chloride as a supporting electrolyte. On the other hand, acetylene, vinyl-chloride, 1,2-dichloroethylene and 1,1,2-trichloroethylene were determined ) after a 24 hr reaction with bromine in glacial acetic acid (1 1). The excess bromine was removed with a stream of nitrogen or carbon dioxide. An aliquot portion is diluted (1 10) with a 3 M solution of sodium acetate in 80 per cent acetic acid and after deaeration the curve is recorded. 

Lithium tetrafluoroborate in wet acetonitrile has been described as an effective combination for the hydrolysis of acetals under mild weakly acidic conditions. Dithians were unaffected. Methods for the hydrolysis of thioacetals continue to appear. Reagents that have been described include a polystyryl-mercury(n) trifluoroacetate combination, which retains the metal on the resin, lead(iv) dioxide and boron trifluoride etherate, aqueous hydrochloric acid in dioxan containing dimethyl sulphoxide, methyl-bis(methylthio)sulphonium hexa-chloroantimonate, and iodoxybenzene, catalysed by toluene-p-sulphonic acid. Dithioacetals derived from ethane-1,2-dithiol may be cleaved with dimethyl sulphoxide in combination with either t-butyl or trimethylsilyl bromides and iodides. Regeneration of ketones from ethanediyl-S S -acetals via the lithium-di-isopropylamide-promoted fragmentation to the thioketone and subsequent hydrolytic work-up only gives satisfactory yields for aryl methylketone derivatives. Dithioacetal SS-dioxides are rapidly cleaved in hot methanolic hydrochloric acid solution. ... 

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