Silica gel flash column chromatography

The reaction was performed in flame-dried modified Schlenk (Kjeldahl shape) flask fitted with a glass stopper or rubber septum under a positive pressure of argon. Trifluoromethanesulfonic anhydride (1.4 equiv) was added to a solution of giycosyl donor (0.191 mmol, 1 equiv) and diphenyl sulfoxide (2.8 equiv) in a mixture of toluene and dichloromethane (8 ml, 3 1 vol/vol) at — 78 °C. The reaction mixture was stirred at this temperature for 5 min and then at —40 °C for 1 h. At this time, 2-chloropyridine (5.0 equiv) and the giycosyl acceptor (3.0 equiv) were added sequentially at —40 °C. The solution was stirred at this temperature for 1 h, then at 0 °C for 30 min and finally at 23 °C for lh before the addition of excess triethylamine (10 equiv). The reaction was diluted with dichloromethane (100 ml) and was washed sequentially with saturated aqueous sodium bicarbonate solution (2 x 100 ml) and saturated aqueous sodium chloride (100 ml). The organic layer was dried (sodium sulfate) and concentrated. The residue was purified by silica gel flash column chromatography. 

Purification by silica gel flash column chromatography (eluent ethyl acetate/cyclohex-ane, 2 8) gave (/ )-4,4-diethoxy-l-nitrobutan-2-ol (245 mg, 1.18 mmol) in 49 % yield, and 92 % ee. 

Most of the A,M-dimethylformamide was removed by distillation under reduced pressure. The solution was extracted with diethyl ether (three times). The combined organic layers were washed with brine, and dried over sodium sulfate. After concentration in vacuo, the residue was purified by silica gel flash column chromatography (hexane/ethyl acetate = 10/1-3/1) to give (aS,R)-5 (2.12 g, 62 %) as a yellow solid. 

A 10 mL round-bottomed flask was charged with (5)-6,6 -[oxybis(ethylene) dioxy]biphenyl-2,2 -diol (1) (98% ee, 225.6 mg, 0.78 mmol), quinine (127.0 mg, 0.39 mmol) and ethanol (2mL). The mixture was warmed until the mixture suspension turned to a clear solution, and was allowed to settle for 12 h. The solid residue [crystals of (5)-l-quinine complex] was collected by filtration. To a mixture of aqueous 1 M HCl and ether was added the obtained crystals of (5 )-l-qumine complex. This was stirred for 15 min at room temperature, and the solution was extracted with ether (twice). The combined organic layers were washed with brine, and dried over sodium sulfate. After concentration in vacuo, the residue was purified by silica gel flash column chromatography (hexane/ethyl acetate = 20/1-3/1) to give optically pure (5)-l (167.8 mg, 74%, 99% ee) as a colourless solid. The enantiomeric excess of (5)-l was determined by chiral stationary-phase HPLC analysis DAICEL CHIRALCEL... 

The mixture was extracted with ethyl acetate (twice) and the combined organic layers were washed with brine and dried over sodium sulfate. Evaporation of solvent gave a crude mixture of epoxides. After purification by silica gel flash column chromatography (hexane/ethyl acetate 100/1-50/1), the corresponding a, S-epoxy ester 3a was obtained (212.7mg, 1.11 mmol, 89%) as a colourless oil. The enantiomeric excess of 3a was determined by chiral stationary-phase HPLC analysis Daicel Chiralpak AD-H, /-PrOH/ hexane 2/98, flow rate 0.4mL min-1, r 31.5 min [(25,5/ )-isomer] and 38.0 min [(2/ ,35)-isomer], detection at 254 nm. [oc]r> —158.8° [c= 1.06, CHCI3 (99% ee)]. 

Lyophilized, pulverized leaves (5.35 kg) of S. divinorum were extracted with ether. The nonpolar components were removed from the concentrated extract through partition between hexanes and 90% aqueous methanol. The dried methanolic fraction was crudely purified by silica gel flash column chromatography (hexanes-ethyl acetate 2/1). Further purification of the biologically active fractions by additional silica gel flash column chromatography (methylene chloride-methanol 20/1) followed by repeated recrystallization yielded pure divinorin A (1) (1.2 g) and B (3) 50mg. 

Diastereomers and optical isomers of hexahyd ropyrido[3,2,1-z) ]qu inazoline 44 were separated by using silica gel flash column chromatography... 

The best chiral controller has been shown to be the 2,4,6-triisopropylphenylsul-finyl group, obtained by the DAG methodology. The two diastereomers of the DAG 2,4,6-triisopropylbenzenesulfinate were separable by silica gel flash-column chromatography, giving the (S)-sulfmate 106(S) as an oil and the (/ )-sulfmate 106(fi) as a solid149 (Scheme 35). Treatment of 106(5) with methyl magnesium iodide affords the R isomer of triisopropylphenyl methyl sulfoxide 107. 

Purification silica gel flash column chromatography (30% ethyl acetate in n-hexane). 

The mixture of 900 mg l-0-(tert-butyldimethylsilyl)-2-methyl-3-methoxy-hex-4-yn-l-ol (3.5 mmol) and 2.6 g 3-butenyloxycarbonyloxy-2,2,2-trichloroethane (10.5 mmol) in 7.0 mL acetone was treated with 76 mg CpRu(CH3CN)3PF6 (0.18 mmol) for 20 min at room temperature. The reaction mixture was concentrated and purified by silica gel flash column chromatography using ether/petroleum ether (1 9 to 1 3) as the eluent to afford 1.49 g (2E,5E)(7S,8S)-9-(f rf-butyldimethylsilyloxy)-7-methoxy-5,8-di-methylnona-2,5-dienoxycarbonyloxy-2,2,2-trichloroethyl, in a yield of 85%. 

Benzaldehyde (1 mmol), aniline (1 mmol), and dimethyl H-phosphonate (2 mL) were added into a 25-mL three-necked flask. The mixture was then heated at 80 °C for 2 min at 180 W in a multimood microwave oven. The reaction mixture was diluted with water and extracted with CH2CI2 (20 mL). The organic layer was washed with H2O (3 X 10 mL), dried over anhydrous Na2S04, filtered, concentrated, and the crude product was purified by silica gel flash column chromatography eluted with 2 1 petroleum ether/acetone to give pure a-aminophosphonate in 98% yield, with melting point at 90-91 C. 

A mixture of the Y-aminoalkene (1 equiv), Selectfluor (2 equiv), and NaHCOs (1 equiv) is dissolved in acetonitrile or propionitrile or butyronitrile (0.02 M) and HjO (2 equiv), followed by addition of PhsPAuSbFg (0.05 equiv). The mixture is stirred for 1.5 h at 80 and the reaction is monitored by TLC. Upon consumption of the starting material, the mixture is diluted with CH2CI2 (5 mL) and filtered over Celite (washing with CH2CI2 (2.5 mL) and EtOAc (2.5 mL)). The solvent is evaporated under reduced pressure and the residue is purified through silica gel flash column chromatography (hexane/EtOAc = 1/1 to 0/100) to yield the desired aminoamides. ... 

To a stirred suspension of Zn(OTf)2 (0.3 mmol) and cyclohexanone (1 mmol) in CH2CI2 (5 mL) was added TMSCl (3 mmol) at 0 °C under argon. The heterogeneous mixture was stirred for 5 min at 0 °C, then 2-morpholinoethyl isonitrile (70) (1.05 mmol) was added. The reaction mixture was warmed to rt and stirred for 24 h. Saturated aqueous NaHCOs (5 mL) was added and the mixture was stirred for another 20 min. The layers were separated, and the aqueous phase was extracted twice with CH2CI2 (10 mL). The combined organic layers were washed with brine, dried over MgS04, and filtered. The solvent was evaporated and the residue purified by silica gel flash column chromatography to afford 69 (57%). 

To a 4 mL clear vial charged with vanadium(III) oxide (3.0 mg, 0.02 mmol, 10 mol%), Select-fluor (106.3 mg, 0.3 mmol, 1.5 equiv) in anhydrous acetonitrile (2.0 mL), and the alkane (1 0.2 mmol, 1.0 equiv) were added. The reaction mixture was degassed thrice by Freeze-Pump-Thaw cycles and then stirred at room temperature for 6-48 h. Upon completion, the reaction mixture was poured into diethyl ether (20 mL), filtrated, concentrated and purified by silica gel flash column chromatography using diethyl ether/pentane as the eluent to afford fluorinated alkane 2, characterized by spectral studies. 

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