Cooling bath, Dry Ice and ethylene glycol

Cooling bath, Dry Ice and ethylene glycol monomethyl ether, 32,43 Dry Ice and methylene chloride, 34, 38... 

A 250-mL poly(chlorotrifluoroethylene) vessel was charged with TaFj (2.2 g, 8 mmol). The vessel was evacuated, cooled in liquid Nj and charged by distillation with HF (20.0 g, 1.0 mol). The vessel was filled with N2 and immersed in a bath of water and ethylene glycol at 5 C. Trichloroethene (108 g, 0.8 mol), cooled to 0 C, was added in one portion. The resulting mixture was stirred for 2.5 h. The mixture was poured over cracked ice (40 g). The organic layer was separated, washed with HjO, and dried (anhyd CaCl2) to give 116.7 g of crude product, which was distilled yield 108.1 g (89%) bp 87-89 C. 

For flash points below 55 F (13 C) or above 140 F (60 C), use as bath liquid a 1 + 1 mixture of water and ethylene glycol. For flash points between 55F(13C) and 140 F (60 C), either water or water-glycol mixture may be used as bath liquid (Note 4). The temp of the liquid in the bath shall be at least 20 F(ll C) below the expected fl p at the rime of introduction of the sample into the test cup. Do not cool the bath liquid by direct contact with carbon dioxide or "dry ice". Place the test cup in position in the bath... 

B. 2-Naphthalenethiol. In a 250-ml. flask, fitted with a diffusion tube2 and swept with nitrogen, is placed 23.1 g. (0.10 mole) of O-2-naphthyldimethylthiocarbamate (Note 4). The flask is heated at 270-275° for 45 minutes in a salt bath (Note 5). After cooling, a solution of 8.4 g. (0.15 mole) of potassium hydroxide in 10 ml. of water and 75 ml. of ethylene glycol is added to the flask. The diffusion tube is replaced by a condenser, and the mixture is heated at reflux for 1 hour (Note 6). The cooled reaction mixture is poured onto 150 g. of ice. After the ice has melted, the mixture is shaken two times with 150-ml. portions of chloroform. The chloroform layers are discarded, and the aqueous layer is cautiously acidified with concentrated hydrochloric acid (Note 7) and shaken three times with 75-ml. portions of chloroform. The organic layers are combined and dried by filtration through anhydrous magnesium sulfate. The solvent is removed by distillation to yield 13-15 g. of crude product. Distillation yields 10.3-12.8 g. (71-80%) of pure 2-naphthalenethiol, b.p. 92-94° (0.4 mm.), m.p. 80-81° (Note 8). 

Urea (4.0 g., 0.067 mole) is dissolved in 50 ml. of distilled ethylene glycol (Note 1) contained in a 125-ml. Erlenmeyer flask. Finely divided recrystallized tetracyanoethylene 2 (25.6 g., 0.20 mole) is added, and the flask is heated on a steam bath at 70-75° with frequent stirring by hand with a thermometer until solution is complete (about 15 minutes). The resultant brownish-yellow solution is then cooled in ice water, and the precipitated dieyanoketene ethylene acetal is collected on a Buchner funnel. The acetal is first washed with two 25-ml. portions of cold ethylene glycol and then washed thoroughly with cold water to remove the ethylene glycol. The dieyanoketene ethylene acetal, which may be dried in air or in a vacuum desiccator, is obtained in (he form of large slightly pink needles, m.p. 115-116.5° (Note 2) yield 21 -23 g. (77-85%). 

A 500-mL, round-bottomed flask is flame-dried and flushed with nitrogen. The flask is equipped with a magnetic stirring bar and a rubber septum and charged with 4.14 g (60.9 mmol) of furan (Note 1) and 300 mL of dry tetrahydrofuran (Note 2). The solution is stirred and cooled in an ethylene glycol-dry ice bath (-15°C) and 24.17 mL (55.6 mmol) of 2.3 M butyllithium is added slowly by means of a syringe pump (rate = 1.5 mL/min). After complete addition, the solution is stirred an additional 30 min. The ethylene glycol-dry ice bath is replaced with an ice bath and the solution stirred for 1.5 hr at 0°C. The flask is then cooled to -78°C in a dry ice-acetone bath. 

A solution of 0.144 g of the 3-ethylene glycol ketal of 5a,lip,17a,21 -tetrahydroxy-6p-fluoro-16a-methylallopregnane-3,20-dione-21 acetate in 12 ml of chloroform and 0.1 ml of absolute alcohol was cooled to -10°C in an ice-salt bath and a stream of anhydrous hydrochloric acid was gently bubbled through the solution for 2.5 hours while the temperature was maintained between -5°C and -15°C. The solution was then diluted with 25 ml of chloroform, washed with dilute sodium bicarbonate and water, dried over anhydrous sodium sulfate, and evaporated to dryness under reduced pressure at 60°C or less to give 6a-fluoro-lip,17a,21-trihydroxy-16a-methyl-4-pregnene-3,20-dione 21-acetate. 

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