Frit filtration

The following describes a typical preparation of 2. In the dry box, lithium (5.3144 g, 0.76587 mol), cut into many small pieces, and naphthalene (49.0802 g, 0.382914 mol) were loaded into a 500 ml three-necked flask equipped with a septum, vacuum adapter, and fritted filtration tube. This flask was removed from the dry box, immersed in the ultrasonic cleaner, and attached to the manifold. Freshly distilled TMEDA (115 ml, 0.762 mol) and freshly distilled toluene (200 ml) were added to a flask by syringe. The reaction proceeded for 4 days... 

A l-Iiter, three-necked, round-bottom flask is equipped with a mechanical stirrer, a thermometer immersed in the reaction mixture, a dropping funnel, and a gas vent. In the flask is placed a mixture of 96% sulfuric acid (25.5 ml, 470 g, 4.8 mole), carbon tetrachloride (100 ml), and adamantane (13.6 g, 0.10 mole), and the mixture is cooled to 15-20° with rapid stirring in an ice bath. One milliliter of 98% formic acid is added and the mixture is stirred until the evolution of carbon monoxide is rapid (about 5 minutes). A solution of 29.6 g (38 ml, 0.40 mole) of t-butyl alcohol in 55 g (1.2 mole) of 98-100% formic acid is then added dropwise to the stirred mixture over 1-2 hours, the temperature being maintained at 15-20°. After stirring for an additional 30 minutes, the mixture is poured onto 700 g of ice, the layers are separated, and the aqueous (upper) layer is extracted three times with lOO-ml portions of carbon tetrachloride. The combined carbon tetrachloride solutions are shaken with 110 ml of 15 A ammonium hydroxide, whereupon ammonium 1-adamantanecarboxylate forms as a crystalline solid. This precipitate is collected by filtration through a fritted glass funnel and washed... 

After 30 minutes the solid sulfinic acid is separated on a fritted-glass filter. The sulfinic acid is dissolved from the filter by a mixture of 750 ml. of ether and 750 ml, of methylene chloride. The solution is dried over calcium chloride and evaporated to dryness under reduced pressure (bath temperature 25°) (Note 5). The residue is suspended in 50 ml. of water, and small portions of dilute ammonia are added to the well-stirred suspension until it has a pH of 9 (Note 6). Insoluble impurities are separated by filtration, and 2-nitrobenzenesulfinic acid is precipitated from the filtrate by adding 5-ml. portions of 6N hydrochloric acid with cooling the sulfinic acid precipitated by each portion of acid is separately collected on a Buchner funnel (Note 7). The acid, a pale yellow solid, is dried on a clay plate in a vacuum desiccator over potassium hydroxide pellets, m.p. 120-125° (dec.), weight 9.4-14.9 g. (50-80%). If the 2-nitrobenzenesulfinic acid is to be used for the hydrogenation of the next step high purity is required, and it is generally advisable to reprecipitate the acid once more in the same way (Note 8). 

This operation is the separation of the precipitate from the mother liquor, the object being to get the precipitate and the filtering medium quantitatively free from the solution. The media employed for filtration are (1) filter paper (2) porous fritted plates of resistance glass, e.g. Pyrex (sintered-glass filtering crucibles), of silica (Vitreosil filtering crucibles), or of porcelain (porcelain filtering crucibles) see Section 3.24. 

N-Methylimidazole is then removed from the reaction mixture with Amberlyst 15 ion exchange resin (Note 9) using the following procedure. To a 2-cm diameter column equipped with a glass frit (Note 1) is added 7 g of Amberlyst 15, which is rinsed with 25 mL of methylene chloride. The reaction mixture is added and the resin mixture is rinsed with 50 mL of methylene chloride. The filtrate is collected in a 250-mL flask (Note 10) and the solvent is removed on a rotary evaporator to afford 1.63-1.66 g (96-98%) of the desired ester 1 as a deep red foam. HPLC analysis showed a purity of 98% (Notes 11, 12, 13, 14). 

Mixtures containing polystyrene resins should either be shaken or stirred with a mechanical stirrer. Stirring with a magnetic stir bar results in destruction of resin beads and the resulting debris can clog frits during filtrations. 

The filtering operation can also be conveniently done in a high-quality nitrogen atmosphere dry box by vacuum filtration through a 90-mm., 60-ml., medium-porosity fritted-disk Buchner funnel. 

Filtration tubes (6-mL capacity) containing a (20-pm pore size) polyethylene frit, VWR (cat. NO.JT7121-6)... 

Partition the sample in methanol twice with 2mL of dichloromethane (DCM), remove the DCM after each partition step and pass the sample in DCM through a 6-mL filtration tube containing a polyethylene frit and packed with 1 g of anhydrous sodium sulfate. The use of the anhydrous sodium sulfate can be eliminated if great care is taken when removing the DCM from each partition step so that no water is included with the DCM. If water droplets are present in the DCM fraction, carefully remove them with a small pipet. The DCM is then concentrated in a Turbovap to 0.1 mL at 50 °C. Note there is the potential for loss of analytes if the samples go to dryness at this step. 

Filter the petroleum ether extract through 1 or 2 cm. of anhydrous sodium sulfate contained in a glass Buchner funnel equipped with a 30-mm. fritted-glass plate of coarse porosity. This filtration may be carried out rapidly without the aid of suction. (A small amount of filtering aid may be mixed with the sodium sulfate to remove plant pigments.)... 

Filter the cold acetone rapidly into a glass-stoppered test tube by means of suction through a 2- or 3-ml. micro Buchner funnel, fitted with a fritted-glass plate of medium porosity. Wash the tube and funnel with 3 ml. of cold acetone and combine it with the filtrate. 

A prototype of a microwave reaction vessel that takes advantage of bottom filtration techniques was presented by Erdelyi and Gogoll in a more recent publication. Therein, the authors described the use of a modified reaction vessel (Fig. 7.2) for the Emrys instruments (see Section 3.5.1) with a polypropylene frit, suitable for the filtration /cleavage steps in their microwave-mediated solid-phase Sonogashira coupling (see Scheme 7.19) [21]. 

Filtration Test. The filtration test equipment consisted of a glass column, with a fritted disc 2 cm. diameter, fitted with a stopcock and a 25 ml graduated cylinder. After mixing the MCC sols with electrolyte solution, the mixture was immediately poured into the glass column with the stopcock closed. The time required to collect water (blank) and filtered sol between 5 to 25 mis in the graduated cylinder after 2 hrs. was determined. The fritted glass was backwashed with water thoroughly after each measurement and a new blank was established. The relative filtration time between sample and water was used to compare differences between samples. 

The reaction vessels were removed from the reaction module, placed in a shaker rack and treated with 1.00 mL of 9.3 mM HMDS in TFA/CDC13 (1 1). After shaking for 1 h, the contents of the vessels were transferred to 15 mL polypropylene vessels equipped with a filter frit, and the filtrate was collected in 4 mL analytical vials. The cleaved resins were washed three times with... 

To the Wang resin (100 mg, 0.070 mmol) in a 3-mL polypropylene filtration tube with polyethylene frit was added 1 mL 0.4 N CDI in anhydrous THF (note 1), capped with a yellow polyethylene cap, and shaken at room temperature for 6 h (note 2). The resin was thoroughly washed with CH2C12 (3x1 mL) and THF (3x1 mL) to remove the excess CDI and then treated with 1 mL 0.4 N piperazine in THF at room temperature for 15 h. The resulting resin was washed with DMF (3x1 mL), MeOH (4x1 mL),... 

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