Column cliromatography

R. E. Robinson, D. Tong, R. Moulder, K. D. Battle and A. A. Clifford, Unified open tubular column cliromatography sequential gas chromatography, at normal pressures and supercritical fluid cliromatography on the same column , J. Microcolumn. Sep. 3 403-409(1991). 

A. Walhagen and F.-E. Edholm, Coupled-column cliromatography of immobilized protein phases for direct separation and determination of dmg enantiomers in plasma , 7. Chromatogr. 473 371-379 (1989). 

Figure 12.11 Coupled SEC-RPLC separation of compound Chemigum mbber stock (a) SEC ti ace (b) RPLC trace of fraction 1, dibutylphthalate (c) RPLC trace of fraction 2, elemental sulfur. Coupled SEC conditions MicroPak TSK 3000H (50 cm) X 2000H (50 cm) X 1000 H (80 cm) columns (8 mm i.d.) eluent, THE at a flow rate of 1 mL/min UV detection at 215 nm (1.0 a.u.f.s.) injection volume, 200 p-L. RPLC conditions MicroPak MCH (25 cm X 2.2 mm i.d.) column flow rate, 0.5 mL/min injection volume, lOpL gradient, acetonitrile-water (20 80 v/v) to 100% acetonitrile at 3% acetonitrile/min UV detection at 254 nm (0.05 a.u.f.s.). Reprinted from Journal of Chromatography, 149, E. L. Jolmson et al., Coupled column cliromatography employing exclusion and a reversed phase. A potential general approach to sequential analysis , pp. 571-585, copyright 1978, with permission from Elsevier Science.

Benzoin la (2 mmol) and zeolite A (2 g) were mixed thoroughly in a mortar and tlie mixture was transfered to a beaker and inadiated for 6 min. The progress of tlie reaction was monitored by TLC using CH2CI2 as solvent. The mixture was extracted into methylene chloride and then filtered. The solvent was removed under reduced pressure to afford pure benzil 2a (340 mg, 80%). Further purification was carried out by column cliromatography (CH2Cl2-light petroleum, 80 20, v/v) and crystallization in EtOH. 

The sulfide 1 (0.75 mmol) is dissolved in dichlorometiiane (2-3 mL) and adsorbed over silica supported sodium periodate (20%, 1.36 g, 1.28 mmol) tliat is wetted with 0.3 mL of water by thoroughly mixing on a vortex mixture. The adsorbed powdered material is transferred to a glass test tube and is inserted in an alumina bath (alumina 100 g, mesh 65-325, Fisher scientific bath 5.7 cm diameter) inside tlie microwave oven. The compound is irradiated for the time specified in the table and the completion of the reaction is monitored by TLC examination. After completion of the reaction, the product is extracted into etliyl acetate (2x15 mL). The removal of solvent at reduced pressure affords crude sulfoxide 2 tliat contains less than 5% sulfone. The final purification is achieved by column cliromatography over silica gel column or a simple crystallization. 

To tlie ketene silyl (thio)acetal (1 equiv.) was added at room temperature neat etliyl propynoate, dimethyl acetylenedicarboxylate or etliynyl methyl ketone (1 equiv.). The mixture was stirred for 5 h at room temperature. The volatile products were removed at room temperature in vacuo (0.1 Torr) for 30 min. Purification of the crude reaction mixture by silica gel column cliromatography (ethyl acetate-hexane, 5 95) afforded cycloadducts. 

Aldehyde 1 (0.2 mmol), alkeiie 2 (1.0 mmol), 2-amiiio-3-picoliiie (0.08 mmol), benzoic acid (0.02 mmol) and RhCl(PPli3)3 (0.01 mmol) were mixed in the absence of any organic solvent and then submitted for 10 min to microwave irradiation inside a domestic microwave oven (Samsung, RE-43 IH, 700 W) or in a monomode Syntliewave 402 Prolabo where power is enslaved to temperature at 140 °C. After the reaction, tlie product 3 was purified by column cliromatography 38-85%. 

A mixture of substituted 2 -hydroxychalcone (1 mmol), the corresponding support (5 g) and the additive (5 mg) in a Pyrex tube was subjected to irradiation at 45 W for 20 min in a Maxidigest 350 Prolabo monomode, focused microwave (2.45 GHz) reactor witli continuous rotation. The cooled mixture was washed with methylene chloride (2xl0mL) and concentrated in vacuo. The residue was purified by two subsequent column cliromatographies (silica gel) by using hexane-acetone (4 1, v/v) and toluene or toluene-etliyl metliyl ketone (30 1, v/v) as eluent. 

The powdered crystals of (+)-l (1 g) were irradiated with tlie Hg-lamp. The photoproduct (+)-2, after purification by column cliromatography, received 93% enantiomeric excess, 74% chemical yield (0.74 g), [a]D-i-123 °(c 0.5, CHCI3), and mp 149-150 °C. 

All equimolar mixture of an aldehyde 1, an amine acetate, and a malonic acid derivative 3 (without solvent) was irradiated in an open glass vessel in a micro-wave oven (Funai M0785VT, 170 W) for several minutes (until the release of CO2 was complete). The reaction was monitored by TLC. The reaction products were separated by column cliromatography on silica gel with a benzene-ethyl acetate eluent (2 1). Note that an increase in tlie microwave power up to 350 W resulted in a decrease in tlie yield of the target amino ester. 

To a freshly prepared catalyst (1 g, 0.2 mmol of iodine) under stilling, a mixture of benzaldehyde la (2 mmol) and etliane-l,2-dithiol (2.2 mmol) was added and stirring continued for 10 min or till tlie reaction was complete. For TLC monitoring, a small amount of tlie solid reaction mixture was taken out with a spatula and washed witli a little amount of ethyl acetate to get a solution. On completion the reaction mixture was loaded on a short column of silica gel (60 to 120 mesh) and eluted witli etliyl acetate. The organic layer was washed with a dilute solution of sodium thiosulfate followed by water and dried over anliydrous sodium sulfate. Evaporation of the solvent under reduced pressure and purification of the residue by column cliromatography yielded the pure product. 

A mixture of benzaldehyde (1.06 g, 10 mmol), ethaiieditliiol (0.94 g, 10 mmol) and commercial grade cadmium iodide (1.85 g, 5 mmol) was mixed thoroughly in an Erlenmeyer flask and placed in a commercial microwave oven operating at 2450 MHz frequency. The whole operation was canied out in a fume-cupboad. After iiTadiation of the mixture for 75 s (monitored by TLC) it was cooled to room temperature and extracted with dichloromethane. Evaporation of the solvent gave almost pure products. Fuilher purification was achieved by column cliromatography on silica gel using chloroform-petroleum ether (1 5) as eluent. 

Typical procedure for the cleavage of sulfonate Piperoiiyl-toluenesulfonate la (2.92 g, 10 mmol) and 37% KF on AI2O3 (3 weight equivalents of sulfonate) were admixed in a Pyrex test tube and subjected to microwave irradiation for 3 min. After cooling down to room temperature, tlie solid mass was extracted with etliyl acetate and concenttated in vacuo. The crude product was subsequently purified by column cliromatography on silica gel (100-200 mesh, ethyl acetate-hexane, 2 8) to afford sesmol 2a (1.22 g, 88% yield) as white solid. 

Montmorillonite K-10 (1 g) was mixed thoroughly with Fe(N02)3 -9H20 (0.404 g, 1 mmol) using a pestle and mortar. This mixture was added to neat tetrahydro-pyranyl ether 1 (1 mmol) in a beaker and was placed into a microwave oven (900 W). The mixture was irradiated for the indicated time. After completion of the reaction, which was monitored by TLC or GC, the crude product was extracted with dichloromethane. GC analysis of the cioide product showed that 2 were obtained in high to excellent yields. Final purification was achieved by column cliromatography using hexane-ethyl acetate as eluent. 

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