Lithium bromide periodate

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. 

A solution of 16jS-methyl-l la,17a,21-trihydroxy-5j5-pregnane-3,20-dione 21-acetate (52), 45 g, in dioxane (297 ml) is cooled to 15° and treated over a 5 min period with a solution of bromine (34.2 g) in dioxane (594 ml) precooled to 18°. After 2 min a solution of sodium acetate (60 g) in water (600 ml) is added and the mixture poured into ice water (8 liters). The precipitate is filtered off, washed to neutrality with water, and dried to give the crude dibromide (53), 55.7 g mp 125-126° (dec.) [aJu 58°. A mixture of dibromide (53), 55.5 g, lithium bromide (27.8 g), lithium carbonate (27.8 g) and DMF (1.11 liters) is refluxed under rapid stirring for 6 hr. The mixture is concentrated under vacuum to about 250 ml, poured into ice water (8 liters) containing hydrochloric acid (250 ml), and extracted with methylene dichloride. The extracts are washed to neutrality with water and evaporated to dryness. The residue is dissolved in acetone, evaporated to dryness under reduced pressure, redissolved in acetone and crystallized by the additon of hexane. This gives the dienone (54) 24.4 g, mp 236-239°. 

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. 

Schmidt and Zimmerman [44] have prepared C20-eryfAro-sphingosine (44) from 4,6-0-benzylidene-D-galactose. This was cleaved with periodate to give the D-threose derivative (41) which, with a Wittig reagent in the presence of lithium bromide, gave predominantly the /raw-olefin (42). This was converted via the trifluoromethane... 

It has been noted elsewhere that the order of addition of reagents is the most important single variable to influence product distribution. A procedure which is convenient and normally reliable is based on the addition of small pieces of metal to a mixture of substrate, ammonia, solvent and (if appropriate) alcohol at less than -70 °C until the blue colour persists for a reasonable period (approximately 10 min). For less reactive substrates, lithium should be used and the addition of the alcohol delayed so that a higher concentration of metal is maintained during the reduction process. Quenching is best effected by 1,3-penta-diene (or similar substance), followed either by ammonium chloride or another electrophile. In reactions where in situ alkylations are performed these are best carried out on lithium derivatives, so in cases where other metals have been used for reduction carefully dried lithium bromide is added before the electrophile. 

A more complete extraction " of polysaccharides was attempted by refluxing the soil for two 30-minute periods with 98 % formic acid containing lithium bromide. The organic matter extracted was precipitated by the addition of isopropyl ether and was redispersed in lithium chloride solution. The colored humic substances were then precipitated with hexadecyltri-methylammonium bromide, while the acidic and neutral polysaccharides were kept in solution by the lithium chloride. The possible degradative effects of hot formic acid on soil polysaccharides have not yet been investigated. 

The sodium periodate-mediated oxidation of alkali halides is a useful method to accomplish the halogenation of aromatic compounds. Accordingly, NaCl is successfully employed as a chlorine source for the chlorination of various aromatic compounds, although mixtures of regioisomers are sometimes obtained on the other hand, the related sodium periodate-mediated bromina-tion reaction, which uses lithium bromide or sodium bromide as halogen source, affords the expected brominated products in a regioselective fashion (eq 33). ... 

Remove the inert gas needle and vent needle from the rubber septum after 15 to 30 minutes, but do not remove the rubber septum. Store the round-bottom flask on a cork ring in a place in the laboratory recommended by your instructor. Allow the reaction to proceed for at least 24 hours or until the next laboratory period. During that time the solution becomes cloudy (formation of lithium bromide), and the mixture retains a yellow color. Be sure to maintain anhydrous conditions during this time period. The mechanism for the reaction of the lithium enolate with the 2-bromo-6-methoxynaphthalene is shown in eqs 4,5, and 6. 

LiBr, lithium bromide Mg(I04)2, magnesium periodate AgN03, silver nitrate MnCl3, manganese(III) chloride Hg2Br2, mercuryfl) bromide... 

To a solution of about 0.07 mol of ethylmagnesium bromide in 120 ml of THF (prepared from 0.08 mol of ethyl bromide, see Chapter II, Exp. 6) was added in 15 min at -50 C a solution of 10.0 g of copper(I) bromide and 6 g of anhydrous lithium bromide in 30 ml of THF. Fifteen minutes later a solution of 0.05 mol of the sulfinate from 1-ethynylcyclohexanol (see Chapter VIII-3, Exp. 2) in 30 ml of THF was introduced at -40°C over a period of 15 min. The cooling bath was then removed and when the temperature had risen to -10 C, the mixture was hydrolyzed by adding slowly a solution of 25 g of ammonium chloride and 15 g of NaCN or KCN in 150 ml of water with vigorous Stirring. The layers were separated and three... 

The first pyrrolylphosphazenes were apparently prepared by McBee and coworkers in 1960, and although the work was never documented in the chemical literature, hexakis-(pyrrolyl)cyclotriphosphazene (1) and octakis-(pyrrolyl)cyclotetraphosphazene were described in a Technical Report of the Defense Technical Information Center.19 Compound 1 was reported to be produced in 26% yield from the interaction of hexachlorocyclotriphosphazene [(NPC 2)3] with excess potassium pyrrolide in refluxing benzene over a 24 hour period. Lithium pyrrolide and pyrrolyl magnesium bromide were found to be unsatisfactory reagents for the preparation of 1. 

A 2-1. fouir-necked flask equipped with a sealed, Teflon-paddle stirrer, a merrcury thermometer, a gas inlet tube, and a dropping funnel is charged with 1.21. of anhydrous tetrahydrofuran (Note 1) and 50 g. (7.1-g. atoms) of lithium pieces (Note 2) under an atmosphere of prepurified nitrogen. The stirred mixture is cooled to —20° by means of a dry ice-acetone bath and a mixture of 100 g. (1.00 mole) of methyl methacrylate (Note 3), and 411 g. (3.0 moles) f n-butyl bromide (Note 4) is added dropwise over a period off 3-4 hours. During this addition, an exothermic reaction ensues which is controlled at —20° (Note 5), and on completion of the addition, the vessel is maintained at this temperature, with stirring, for an additional 30 minutes. The contents oF the flask are then liltered with suction through a... 

H. Stamm also measured the solubilities of the salts of the alkalies in liquid ammonia —potassium hydroxide, nitrate, sulphate, chromate, oxalate, perchlorate, persulphate, chloride, bromide, iodide, carbonate, and chlorate rubidium chloride, bromide, and sulphate esesium chloride, iodide, carbonate, and sulphate lithium chloride and sulphate sodium phosphate, phosphite, hypophosphite, fluoride, chloride, iodide, bromate, perchlorate, periodate, hyponitrire, nitrite, nitrate, azide, dithionate, chromate, carbonate, oxalate, benzoate, phtnalate, isophthalate ammonium, chloride, chlorate, bromide, iodide, perchlorate, sulphate, sulphite, chromate, molybdate, nitrate, dithionate, thiosulphate, persulphate, thiocyanate, phosphate, phosphite, hypophosphite, arsenate, arsenite, amidosulphonate, ferrocyanide, carbonate, benzoate, methionate, phenylacetate, picrate, salicylate, phenylpropionate, benzoldisulphonate, benzolsulphonate, phthalate, trimesmate, mellitate, aliphatic dicarboxylates, tartrate, fumarate, and maleinate and phenol. 

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