Silica flash chromatography

Spiro-prorocentrimine was isolated from Prorocentrum cells by Lu et al. [7] by methanolic extraction and subsequent partition against hexane, chloroform, and 1-butanol. Combined chloroform and butanol phases were subjected to flash chromatography on silica, RP-HPLC on ODS, GPC, again silica flash chromatography, and RP-HPLC on ODS. 

This material Is purified by recrystallization from ethyl acetate acetone 2 1 (v v) to give a first crop (6.8 g), and by flash chromatography of the residue from the mother liquor, using 150 g of 230-400 mesh silica gel (Merck), a 40-mm diameter column, and elution with 10 1 (v v) ethyl acetate methanol. A fast moving orange band and a slower moving lemon-yellow band can be clearly seen on the column. The lemon-yellow hand is collected from the column and evaporation gives a second crop (1.4 g) of comparably pure material. The total yield of the pale yellow isoquinoline is 8.2 g (86t), mp 135-137°C (Note 10). 

Carbonate ionophore I [ETH 6010] (heptyl 4-trifluoroacetylbenzoate) [129476-47-7] M 316.3, b 170°/0.02 Torr, d 0.909. Purified by flash chromatography (2g of reagent with 30g of Silica Gel 60) and eluted with EtOAc/hexane (1 19). The fractions that absorbed at 260nm were pooled, evapd and dried at room temp (10.3 Torr). The oily residue was distd in a bubbled-tube apparatus (170°/0.02 Torr). Its IR (CHCI3) had peaks at 1720, 1280, 940cm and its sol in tetrahydrofuran is 50mg/0.5mL. It is a lipophilic neutral ionophore selective for carbonate as well as being an optical humidity sensor. [Anal Chim Acta 233 41 1990.]... 

Chromoionophore I [ETH 5294] [9-diethylamino-5-octadecanoyl-imino-5-//-benzo[a]-phenoxazine] [125829-24-5] M 583.9. Purified by flash chromatography (Silica Gel) and eluted with EtOAc. The coloured fractions are pooled, evaporated and recrystd from EtOAc. It is a lipophilic chromoionophore and is a selectophore for K and Ca ions. [Anal Chem 62 738 7990.]... 

M 340.6. Purified by flash chromatography (at 40 kPa) on silica and eluting with EtOH-hexane (4 1). IR has v(CHCl3) 1630cm. [Helv Chim Acta 63 2271 1980.] It is a good magnesium selectophore compared with Na, K and Ca [Anal Chem 52 2400 7950]. 

Magnesium ionophore II (ETH 5214), [A/,A/"-octamethylene-bis(A/ -heptyl-)V"-methyl methylmalonamide)] 1119110-37-1] M 538.8. Reagent ca 700mg) can be purified by flash chromatography on Silica Gel 60 (30g) and eluting with CH2Cl2-Me2CO (4 1). [Anal Chem 61 574 1989.]... 

To a solution of m-ethyl cinnamate (44, 352 mg, 85% pure, 1.70 mmol) and 4-phenylpyridine-A-oxide (85.5 mg, 29 mol%) in 1,2-dichloromethane (4.0 mL) was added catalyst 12 (38.0 mg, 3.5 mol%). The resulting brown solution was cooled to 4°C and then combined with 4.0 mL (8.9 mmol) of pre-cooled bleach solution. The two-phase mixture was stirred for 12 h at 4°C. The reaction mixture was diluted with methyl-t-butyl ether (40 mL) and the organic phase separated, washed with water (2 x 40 mL), brine (40 mL), and then dried over Na2S04. The drying agent was removed by filtration the mother liquors concentrated under reduce pressure. The resulting residue was purified by flash chromatography (silica gel, pet ether/ether = 87 13 v/v) to afford a fraction enriched in cis-epoxide (45, cis/trans . 96 4, 215 mg) and a fraction enriched in trans-epoxide cis/trans 13 87, 54 mg). The combined yield of pure epoxides was 83%. ee of the cis-epoxide was determined to be 92% and the trans-epoxide to be 65%. 

POCI3 was added to a solution of amide 62 (0.075g, 0.02 mmol) in toluene (5 mL). The reaction mixture was heated to 110 °C with stirring for 5 h, then cooled to rt. A solution of 2 N NaOH (10 mL) was added and the mixture was extracted with ether (3 x 15 mL). The combined organic extracts were dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The crude product was then purified by flash chromatography on silica gel (40% Ethyl acetate/hexanes) to afford the 68 mg (95%) of the title compound as... 

Flash chromatography is widely employed for the purification of crude products obtained by synthesis at a research laboratory scale (several grams) or isolated as extracts from natural products or fermentations. The solid support is based on silica gel, and the mobile phase is usually a mixture of a hydrocarbon, such as hexane or heptane, with an organic modifier, e.g. ethyl acetate, driven by low pressure air. (Recently the comparison of flash chromatography with countercurrent chromatography (CCC), a technique particularly adapted to preparative purposes, has been studied for the separation of nonchiral compounds [90].)... 

A solution of 2 -(bromomethyl)biphenyl-2-carbaldehyde (45 1 g 3.6 mmol) and 25 % aq NH3 (20 mL) in EtOH (100 mL) was heated under reflux for 5 h. The mixture was cooled and stirred for 15 min with 10% aq NaOH (20 mL). The basic solution was extracted with CH2C12, the extract dried, and the solvent evaporated to give the product as an oil which was purified by flash chromatography (silica gel, Et20/ hexane) yield 0.667 g (95%) mp 84-85 C... 

The only 5//-1,3,6-triazonine system which has been reported and is fully supported by spectral data and elemental analysis is obtained by reaction of the imine 1 with chloroacetic acid and polyphosphoric acid.22 From a mixture of products, 2-chloro-6-(chloromethyl)-13-phenyl-dibenzo[e/, h [, 3,6]triazonine (2) was separated by silica-gel flash chromatography in poor yield. 

Trapping the reaction mixture with 3.9 g (12.0 mmol) of tributyltin chloride affords, after aqueous workup and flash chromatography (silica gel, pentane/diethyl ether 20 1) a mixture of the (1Z.3/ )- and (1 ,3S)-isomers yield 2.34 g (48%). For further conversions see Section D.l.3.3.3.8.2.3. 

To a —78 °C solution of (4/C5/ )-2-[(.S )-l-chloro-2-propcnyl]-4,5-dicyclohcxyl-l, 3,2-dioxaborolanc (6) (theoretically 2.0 mmol) in THF are added 0.20 mL (2.0 mmol) of benzaldehydc. The mixture is allowed to reach r.t. overnight and is then treated with 0.30 g (2.0 mmol) of triethanolamine. After stirring for 3 h, 15 mL of sat. aq NH4C1 are added. The phases are separated and the aqueous phase is extracted with three 20-mL portions of diethyl ether. The combined extracts are dried over MgS04 and concentrated. The oily residue is purified by flash chromatography (silica gel, petroleum ether/diethyl ether 6 1) yield 0.26 g (79%) >99% ee [capillary GC of the carbamates obtained with (5 )-(l-isoCyanoethyl)benzene],... 

A solution of 1.5 mol equiv of butyllithium in hexane is added to 1.5 mol equiv of a 1 M solution of hexabutylditin in THF at 0 C under nitrogen, and the mixture is stirred for 20 min. The solution is cooled to — 78 °C and a solution of 1.5 mol equiv of diethylaluminum chloride in toluene is added. After stirring for 1 h at — 78 °C, a solution of 0.05 mol equiv of [tetrakis(triphenyl)phosphine]palladium(0) in THF is added followed by a solution of the allyl acetate in THF. The mixture is warmed to r.t., and stirred until the allyl acetate has reacted (TLC). The solution is cooled to 0°C, and an excess of aq ammonia slowly added. After an aqueous workup, the products arc isolated and purified by flash chromatography on silica gel using 1 % triethylamine in the solvent to avoid acid-induced loss of stannane. 

A mixture of 200 mg (1.9 mmol) of benzaldehyde and 1.35 g (3.8 mmol) of ( )-tributyl(l-mcthyl-2-butenyl)stannane [containing ca. 10% of its (Z)-isomer] is heated to 150 °C for 18 h in a sealed tube. Flash chromatography of the orange residue (silica gel, Ei20/peti oIeuni ether 1 5) gives a pale yellow oil yield 240 mg (72%) analyses by H NMR. 

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