Purification, general procedures ethers

General Procedure for Microwave-Induced Fries Rearrangement. Neat substrate (0.01 mol) was mixed with the support (1 3, w/w) in a beaker and was exposed to microwave irradiation for 7 min. After cooling to room temperature the product was extracted with diethyl ether. Evaporation of the solvent gave almost pure product. Further purification was carried out by recrystallization or column chromatography on silica gel. 

As a general procedure if the olefin is impure, the oxymercura-tion-reduction process may include an olefin purification step. Alternatively, this process may be used to purify the olefin for other purposes. - In such cases, acetone is substituted for ether and, after oxymercuration for the same length of time as suggested above, the solution is poured with stirring into two volumes of water containing one equivalent each of sodium bicarbonate and sodium chloride. The mercury derivative is filtered, recrystallized from ethanol-water, ether, dioxane, or ethyl acetate-heptane and then either reduced as described above (in 70-80% yield) to produce pure alcohol, or deoxy-mercurated with cold 6N HCl, with ethereal lithium aluminum hydride (added cautiously), or high concentrations of alkali halides - to produce the pure olefin. 

General procedure for insertion reaction of alkynes into 2,6-dia-zasemibullvalene 6-la. 2,6-Diazasemibullvalene 6-la (0.5 mmol, 136 mg) in 2 mL of toluene was treated with dimethyl acetylenedicarboxylate (1.0 mmol, 123 pi) or diethyl analogue (1.0 mmol, 160 pi), and the reaction mixmre was stirred at 90 °C for 3 h. After the removal of solvent in vacuum, purification by column chromatography (silica gel, petroleum ether/diethyl ether/triethylamine = 100 3 1) gave 6-7a or 6-7b as pure products. 

General procedure To a stirred solution of appropriate (9-methyl (1-hydroxy-alkyl)methylphosphinates M12 (0.005 mol) and triethylamine (0.0072 mol) in 5 mL of trichloromethane, (5-methyl-isoxazol-3-yl)oxyacetyl chloride M16 (0.006 mol) in 5 mL of trichloromethane was added dropwise below 0 °C. The mixture was stirred at room temperature for 4—6 h. Normal workup and purification by column chromatography on silica gel and elution with petroleum ether/acetone (5/1, v/v) gave the corresponding pure tide compound. IIIJ-l-IIIJ-8 could be obtained by this procedure in 23-55 % yields [32]. 

In a typical procedure the sulfonyl chloride in ether is added to an etheral solution of the diazoalkane and triethylamine. Filtration and evajroration gives the relatively pure thiirane dioxide. Further purification can be easily achieved by recrystallizations preferentially below room temperature in order to avoid fragmentation of the product into sulfur dioxide and the olefin. In general, when the temperature of the above reaction is lowered, the yields are improved without a drastic decrease in reactivity Many thiirane dioxides have been successfully synthesized through this method and a detailed list of them can be found elsewhere. ... 

All solvents used for general applications were of reagent grade. For special purposes, purification of solvents was effected using standard procedures. All other reagents were used as supplied commercially except as noted. A solution of chloromethyl methyl ether (6 mmole/mL) in methyl acetate was prepared by adding acetyl chloride (141.2 g, 1.96 mol) to a mixture of dimethoxy methane (180 mL, 2.02 mol) and anhydrous methanol (5.0 mL, 0.12 mol).20 The solution was diluted with 300 mL of 1,1,2,2-tetrachloroethane and used as a stock solution for the chloromethylation experiments. 

Volatile hydrides may be prepared from ether solutions by the reaction of the appropriate chlorides with lithium tetrahydroaluminate. In this general method, it is necessary to work with strictly anhydrous reagents and solvents because of the great reactivity of lithium tetrahydro-aluminate toward water. The procedures described below are believed to be much more convenient because the reducing agent employed is potassium tetrahydroborate, which is relatively insensitive toward water. Since only aqueous solutions are involved, there are no solvent-purification steps and there is no dissolution or contamination of stopcock grease, etc. 

Liquid-liquid partitioning cleanup is generally carried out at alkaline conditions using ethyl acetate, ethyl acetate-tert-butanol mixture, diethyl ether, or tert-butyl methyl ether/n-butanol as extraction solvents. " The organic extracts are then either concentrated to dryness or repartitioned with dilute acid to facilitate back extraction of the analytes into the acidic solution. A literature survey shows that liquid-liquid partitioning cleanup resulted in good recoveries of substituted anilines such as clenbuterol, " but it was less effective for more polar compounds such as salbutamol. Diphasic dialysis can be also used for purification of the primary sample extract. This procedure was only applied in the determination of clenbuterol residues in liver using tert-butyl methyl ether as the extraction solvent. ... 

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