Ethyl acetate bromide

Didodecyldimetbylammonium bromide [3282-73-3] M 463.6, m 157-162 . Recrystd from acetone, acetone/ether mixture, then from ethyl acetate, washed with ether and dried in a vacuum oven at 60° [Chen et al. J Phys Chem 88 1631 1984 Rupert et al. J Am Chem Soc 107 2628 1985 Halpern et al. J Am Chem Soc 108 3920 1986- Allen et al. J Phys Chem 91 2320 1987]. 

Phenylphenacyl bromide [135-73-9] M 275.2, m 126°. Crystd (charcoal) from EtOH (15mL/g), or ethyl acetate/pet ether (b 90-100°). 

Tetra-n-butylammonium iodide [311-28-4] M 369.4, m 146". Crystd from toluene/pet ether (see entry for the corresponding bromide), acetone, ethyl acetate, EtOH/diethyl ether, nitromethane, aq EtOH or water. Dried at room temperature under vac. It has also been dissolved in MeOH/acetone (1 3, lOmL/g), filtered and allowed to stand at room temperature to evaporate to ca half its original volume. Distilled water (ImL/g) was then added, and the ppte was filtered off and dried. It was also dissolved in acetone, ppted by adding ether and dried in vac at 90" for 2 days. It has also been recrystallised from CH2Cl2/pet ether or hexane, or anhydrous methanol and stored in a vacuum desiccator over H2SO4. [Chau and Espenson J Am Chem Soc 108 1962... 

A total of 50 ml (0.15 moles) of a 3 ethereal solution of methylmagnesium bromide is added slowly to a vigorously stirred solution of 5.8 g (12.5 mmoles) or 3,3 20,20-bisethylenedioxy-5a,6a-epoxy-5a-pregnane-ll/l,17a,21-triol in 400 ml of tetrahydrofuran. The solution is heated under reflux for 24 hr, cooled and treated with 32 ml of saturated ammonium chloride solution. The supernatant is decanted and the residue is washed with several portions of tetrahydrofuran. The combined supernatants are evaporated and extracted with ethyl acetate, washed with saturated salt solution, dried and concentrated to give 4,55 g (75%) of 3,3 20,20-bisethylenedioxy-6 -methyl-5a-pregnane-5a,ll, 17a,21-tetrol mp 170-172° after crystallisation from acetone-petroleum ether. The analytical sample is crystallized from acetone-petroleum ether mp 175-177° [aJo —11° (CHCI3). 

A-Homo-estra-, 4, )-triene-3, l-dione (50). A solution of bromo ketone (49 0.2 g), silver perchlorate (0.5 g) and 20% aqueous acetone (30 ml) is heated at reflux with stirring for 30 min and then allowed to cool to room temperature. The mixture is filtered to remove precipitated silver bromide (ca. 0.19 g) and the filtrate is diluted with water (200 ml) and then extracted with chloroform. The chloroform extracts are washed, successively with water, 5% sodium bicarbonate solution, water and saturated salt solution. After being dried over anhydrous magnesium sulfate, the solvents are removed at reduced pressure to give a solid. Recrystallization from ethyl acetate gives A-homo-estra-l,4,5(10)-triene-3,17-dione (50 0.17 g) mp 193-197°. 

Cyclopropyltriphenylphosphonium Bromide (5). The lactone salt is pyrolyzed by placing it in a round-bottom flask fitted with an adaptor attached to a vacuum source (aspirator is sufficient). The flask is heated (oil bath) to 180-190° for 48 hours. The residue is a virtual quantitative yield of the tan product, which may be crystallized from ethyl acetate giving cream crystals, mp 189-190°. An alternate setup is convenient if a drying pistol (Abderhalden) is available. The compound is placed in the pistol, which is then evacuated. Decalin (bp approx. 187°) is refluxed over the pistol to provide the heating source. The work-up is the same. 

The methyl bromide quaternary was prepared by saturating a solution of the base in dry ethyl acetate with methyl bromide. After standing for 9 days the resulting crystalline solid was filtered and recrystallized from butanone and from ethyl acetate MP 193° to 194.5°C. 

A mixture of 10 mmol of the allyl bromide and 10-15 mmol of the aldehyde, dissolved in 20 mL of THF, is added dropwise at — 5 to 0°C to the chromium(II) chloride solution in THF prepared by method A or B. The mixture is stirred for 36 h at this temperature and then 15 mL of sat. sodium hydroxide and 20 g of anhyd Na2S04 are added stirring is continued for 20 min at 201C. The mixture is filtered over a pad of Celite/Na2S04 (7 l). The filtrate is concentrated and the residue purified, usually by chromatography on silica gel with pentane/diethyl ether or hexane/ethyl acetate. 

A solution of the 0-silylketone (1 mmol) in chloroform (3 ml) was added to a suspension of copper(n) bromide (2 mmol) in boiling ethyl acetate (3 ml). The mixture was heated under reflux for 0.75 h, and then cooled, diluted with carbon tetrachloride (10ml), filtered, and the precipitate... 

Tetrabutylammonium bromide (TBABr), recrystallize from ethyl acetate Ultrapure water for HPLC analysis... 

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture.74 In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in 1.5 h, while the same reaction gave only less than 50% yield in a variety of other organic solvents such as ether, benzene, or ethyl acetate, even after a reaction time of 10 h. The reaction was equally successful with a combination of allyl bromide, tin metal, and a catalytic amount of hydrobromic acid. In the latter case, the addition of metallic aluminum powder or foil to the reaction mixture dramatically improved the yield of the product. The use of allyl chloride for such a reaction,... 

After the final filtration the product is washed with two 100-ml. portions of ethyl acetate and two 100-ml. portions of anhydrous ether and dried for 24 hours at 80°. The dried, analytically pure vinyl triphenylphosphonium bromide, m.p. 186-190°, weighs 122-158 g. (66-86%). 

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