Suspension, evaporative cooling

The suspension may be warmed to dissolve the alkene more rapidly. (E)-Stilbene dissolves completely at ca. 65°. If the suspension is warmed, it must be cooled below 30° before proceeding further to prevent a vigorous reaction when the N-bromo-succinimide is added. The submitters recommend that the warm suspension be cooled under an atmosphere of nitrogen. If a volatile alkene is used, the mixture should be cooled prior to and during the addition of N-bromosuccinimide to prevent losses by evaporation. 

The suspension 1s cooled to 20°C on 1ce and then 800 mL of 1.4 M aqueous sulfuric acid is cautiously added over 0.75 hr so that the temperature remains below 45°C. The resulting solution is stirred for 5 min and then 600 mL of ether is added. Both phases are transferred to a 4-L separatory funnel and the layers are separated. The aqueous phase is extracted twice with 400-mL portions of ether and all ether layers are individually washed in series with two 1-L portions of water and once with 800 mL of saturated sodium chloride solution. The combined organic extracts are dried over magnesium sulfate and concentrated by rotary evaporation. The yellow-brown residue is purified by short path distillation to afford 82-86 g (91-94 yield) of 3-trimethylsilyl-2-propyn-l-ol as a clear, colorless liquid (Note 7), bp 76°C (20 mm) (Note 8). 

A solution of the 2p,3[3-epoxy-5a-androstan-17-one (30.0 g) in ethanol (130 ml), water (15 ml) and liquid ammonia was heated in an autoclave at 150°C for 6 h and the resultant crystalline suspension evaporated to dryness. Water (35 ml) and acetic acid (36 ml) were added and the solution kept at 90°C for 1 h, cooled and excess water added. The precipitated material was filtered off and the filtrate made alkaline with aqueous 10 N potassium hydroxide solution to precipitate a white solid which was filtered off, washed neutral with water, dissolved in methylene chloride, the solution dried (Na2S04) concentrated and ether added to give 2p-hydroxy-3a-amino-5a-androstan-17-one (14.3 g), melting point I92°-195°C. 

Chlorocarbonylphenyl Phenyl Tellurium1 16.2 g (0.05 mol) of 2-carboxyphenyl phenyl tellurium are suspended in 80 ml of dichloromethane and the suspension is cooled to 0°. Then 12 ml of butyl dichloromethyl ether and 0.2 g of anhydrous zinc chloride are added, the mixture is allowed to warm to 20°, and is held at that temperature for 1 h. When all the acid has dissolved, charcoal is added, the mixture is filtered, the filtrate is evaporated, and the resultant product is recrystallized from hexane/benzene yield 11 g (64%) m.p. 89 91°. 

Tetraphenyl Tellurium3,7 0.51 g (1.9 mmol) of tellurium tetrachloride is suspended in 3 ml of anhydrous diethyl ether under nitrogen and the suspension is cooled to 70°. 10.5m/(10.5 mmol)ofa 1 molar solution of lithium halide-free phenyl lithium in diethyl ether is added dropwise to the cooled, stirred suspension, the mixture is allowed to warm to 20° over 30 min, and is centrifuged. The solution is decanted under nitrogen and concentrated by evaporation of the solvent in a stream of nitrogen at 20°. The concentrate is cooled to — 70°, the crystals are collected under an inert atmosphere, washed once with 3 ml of cold diethyl ether, and dried. The product should be handled under an inert atmosphere yield 0.57 g (70%) m.p. 98-102° with softening at > 60°. 

Diacenaphtho[l,2-A l -ej-l -ditellurin1 A mixture of 256 mg (2.0 mmol) of tellurium, 106 mg (2.2 mmol) sodium hydride (60% suspension in oil washed thoroughly with dry hexane to remove the mineral oil), and 3 ml dry dimethylformamide is heated at 140J for 1 h. The resulting pale-yellow suspension is cooled to 20" and mixed with 808 mg (2.0 mmol) of 1,2-diiodoacenaphthalene in 3 ml dimethylformamide. The mixture is stirred at 20° for 24 h. The reaction is quenched with 10 ml 10% aqueous solution of ammonium sulfate. The mixture is extracted with 10 m/diethyl ether. The extract is washed with water, dried with anhydrous sodium sulfate, filtered, and the filtrate evaporated. The crude productis chromatographed on silica gel with benzene as the mobile phase yield 35% m.p. 283-287° (from benzene). 

In the suspension process, the polymer is suspended in the monomer propylene. This process offers the advantages of being able to operate at higher solids owing to the lower viscosity of a suspension compared with a solution at comparable solids. Other advantages are simple heat removal by the evaporative cooling of the propylene, more uniform... 

A,A-Dimethylaminothiocarbonyl Ethenyl Tellurium Under an argon atmosphere 6.38 g (50 mmol) of tellurium are added in one portion to 45.5 ml (23 mmol) of a 0.5 molar solution of vinylmagncsium bromide in tetrahydrofuran at — 78°. The mixture is stirred at — 78° for 1 h, warmed to 0°, and stirred at 0° for I h. The resultant yellowish-brown suspension is cooled to —78°, a solution of 6.18 g (50 mmol) of N,N-dimethylamino-(thiocarbonyl) chloride in 25 ml of tetrahydrofuran (freshly distilled from sodium) is added dropwise to the stirred suspension, and the mixture is stirred at — 78° for 0.5 h, at 0° for 1 h, and at 20" for 0.5 b. The mixture is then poured into ice/water and glacial acetic acid is added dropwise until the magnesium hydroxide has dissolved. The mixture is extracted three times with 150 ml portions of diethyl ether, the combined extracts arc washed three times with water, the ether solution is dried, and evaporated. The dcep-orange-red solid residue is the pure product yield 8.7 g (72%) m.p. < 25°... 

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