Lithium ethanol

In order to understand the formation of compounds now being discussed one has to realize that tris(trimethylsilyl)phosphane originating in the desilylation of [l-(trimethylsiloxy)benzylidene]-trimethylsilylphosphane (Scheme 1) reacts slowly with lithium ethanolate to give lithium bis(trimethylsilyl)phosphanide again (Eq. 13). This compound must then be considered a continuous source for the phosphaalkyne H5Q-C P, provided that a sufficient amoimt of ethyl benzoate is present in solution. 

TMS-cyclohexa-1,4-diene (112) can be synthesized (yield 85%) from l,3-bis(TMS)-benzene (111) via treatment with lithium/ethanol and liquid ammonia at — 70°C (Birch reaction) under partial desilylation (equation 55)75,76. 1-TMS-cyclohex-l-ene (115) can... 

The lithium which remains on the glass-wool should be destroyed immediately with a mixture of ethanol and water. 

Iodine Acetaldehyde, acetylene, aluminum, ammonia (aqueous or anhydrous), antimony, bromine pentafluoride, carbides, cesium oxide, chlorine, ethanol, fluorine, formamide, lithium, magnesium, phosphorus, pyridine, silver azide, sulfur trioxide... 

Lithium Peroxide. Lithium peroxide [12031 -80-0] Li202, is obtained by reaction of hydrogen peroxide and lithium hydroxide in ethanol (72) or water (73). Lithium peroxide, which is very stable as long as it is not exposed to heat or air, reacts rapidly with atmospheric carbon dioxide releasing oxygen. The peroxide decomposes to the oxide at temperatures above 300°C at atmospheric pressure, and below 300°C under vacuum. 

Cationic rings are readily reduced by complex hydrides under relatively mild conditions. Thus isoxazolium salts with sodium borohydride give the 2,5-dihydro derivatives (217) in ethanol, but yield the 2,3-dihydro compound (218) in MeCN/H20 (74CPB70). Pyrazolyl anions are reduced by borohydride to pyrazolines and pyrazolidines. Thiazolyl ions are reduced to 1,2-dihydrothiazoles by lithium aluminum hydride and to tetrahydrothiazoles by sodium borohydride. The tetrahydro compound is probably formed via (219), which results from proton addition to the dihydro derivative (220) containing an enamine function. 1,3-Dithiolylium salts easily add hydride ion from sodium borohydride (Scheme 20) (80AHC(27)151). 

The lithium ethoxide solution is prepared by dissolving f.40 g. of lithium wire in 1 1. of anhydrous ethanol. 

Krapcho and Bothner-By made additional findings that are valuable ii understanding the Birch reduction. The relative rates of reduction o benzene by lithium, sodium and potassium (ethanol as proton donor) wer found to be approximately 180 1 0.5. In addition, they found that ben zene is reduced fourteen times more rapidly when methanol is the protoi donor than when /-butyl alcohol is used. Finally, the relative rates of reduc tion of various simple aromatic compounds by lithium were deteiTnined these data are given in Table 1-2. Taken together, the above data sho that the rate of a given Birch reduction is strikingly controlled by the meta... 

A competing reaction in any Birch reduction is reaction of the alkali metal with the proton donor. The more acidic the proton donor, the more rapid IS the rate of this side reaction. Alcohols possess the optimum degree of acidity (pKa ca. 16-19) for use in Birch reductions and react sufficiently slowly with alkali metals in ammonia so that efficient reductions are possible with them. Eastham has studied the kinetics of reaction of ethanol with lithium and sodium in ammonia and found that the reaction is initially rapid, but it slows up markedly as the concentration of alkoxide ion in the mixture... 

A solution of hydrazoic acid (prepared from about 30 g sodium azide) in ca. 200 ml chloroform is prepared in a well-ventilated hood. Cholesterol (15 g) is dissolved in the hydrazoic acid solution and 3.5 ml of triethylamine is added. The reaction mixture is then stirred at room temperature while 7 g of A-chlorosuccinimide is added. The reaction mixture is allowed to stand overnight and then the chloroform solution is washed successively with dilute sodium bisulfite, dilute soldium bicarbonate solutions and finally with water. The chloroform extract is then dried (Na2S04) and the solvent removed in vacuo. The residue is crystallized from ethanol to yield ca. 8.5 g of (101) in colorless needles mp 138-139°. The chloro azide is reduced to the aziridine by lithium aluminum hydride according to the foregoing procedure. 

A setup similar to the preceding one is used in this experiment except that provision should be made for heating the reaction vessel (steam bath, oil bath, or mantle). Lithium aluminum hydride (10 g, 0.26 mole) is dissolved in 200 ml of dry -butyl ether and heated with stirring to 100°. A solution of 9.1 g (0.05 mole) of ra j-9-decalin-carboxylic acid (Chapter 16, Section I) in 100 ml of dry -butyl ether is added dropwise over about 30 minutes. The stirring and heating are continued for 4 days, after which the mixture is cooled and water is slowly added to decompose excess hydride. Dilute hydrochloric acid is added to dissolve the salts, and the ether layer is separated, washed with bicarbonate solution then water, and dried. The solvent is removed by distillation, and the residue is recrystallized from aqueous ethanol, mp 77-78°, yield 80-95 %. 

Excess lithium is destroyed by the c irc/w/addition of 1-2 ml of ethanol, and hydrolysis of the reaction mixture is then effected by the addition of a mixture of ice (50 g) and water (100 ml). The solution is then acidified to pH 2 by the addition of 5 A hydrochloric acid, followed by rapid stirring for 1 or 2 minutes to hydrolize the HMPT. The aqueous solution is extracted with ether, the ether solution is dried with magnesium sulfate, then filtered, and the ether is evaporated. The product is isolated by distillation of the residue. 

A 250-mI round-bottom flask fitted with a condenser (drying tube) is charged with a mixture of 2-bromocholestanone (4.7 g, 0.01 mole), lithium carbonate (7.4 g, 0.10 mole), and 100 ml of dimethylformamide. The system is flushed with nitrogen and then refluxed (mantle) for 18-24 hours. After the reflux period, the solution is cooled and poured into 500 ml of water. The aqueous mixture is extracted with 50 ml of ether, the ether extract is dried (sodium sulfate), and the ether is removed (rotary evaporator). The residue may be recrystallized from ethanol or methanol. J -Cholestenone is a white solid, mp 98-100°. 

Step B Preparation of 3-Methoxy-17a-Methyl-19-Nor-A ° -Pregn3diene-20-ol — 500 cc of ammonia and a solution of 20 grams of 3-methoxy-17a -methyl-19-nor-A , ( >-pregna-triene-20-one were admixed with 400 cc of THF, and 10 cc of ethanol were added. The temperature was lowered to -35°C. 2.150 grams of lithium were added under an inert atmosphere and the reaction mixture was agitated for 15 minutes, after which 10 cc of ethanol and... 

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