Silica-gel column

There is a reported example of using an open silica gel column for the puriAcation of nitenpyram. The extract containing nitenpyram is evaporated and applied to a silica gel column (silica gel 10 g and anhydrous sodium sulfate 5 g). Nitenpyram is eluted... 

A. 3,5-Dimethylphenyl 1-bromo-2-naphthoate (3). Under a nitrogen atmosphere, a 250-mL, oven-dried, round-bottomed flask containing anhydrous dichloromethane (100 mL) is charged with 1-bromo-2-naphthoic acid (1, 2.51 g, 10.0 mmol), 3,5-dimethylphenol (2, 1.23 g, 10.1 mmol), dicyclohexylcarbodiimide (DCC, 2.26 g. 11.0 mmol), and 4-(dimethylamino)pyridine (DMAP, 244 mg, 2.00 mmol) (Note 1). After the mixture is stirred for 12 hr at room temperature, the white precipitate that forms (Note 2) is discarded by filtration through a Buchner funnel. From the clear filtrate, the solvent is removed by rotary evaporation (35°C, 720 mbar, 540 mm) to give a colorless solid. RItration through a short silica gel column (5 x 40-cm column, silica gel 0.063 - 0.2 mm, 150 g eluent hexane / diethyl ether 5 1) delivers 3.35 g (94%) of the ester 3, which Is recrystallized from diethyl ether / hexane to give 3.28 g (92%) of a colorless solid (Note 3). 

B. 1,3-Dimethyl-6H-benzo[b]naphtho[1,2-d]pyran-6-one (4). Under an argon atmosphere, a 250-mL, oven-dried, round-bottomed flask, equipped with a reflux condenser, is charged with freshly distilled N,N-dimethylacetamide (DMA, 130 mL), 3,5-dimethylphenyl 1-bromo-2-naphthoate (3, 3.24 g, 9.12 mmol), palladium(ll) acetate (205 mg, 0.913 mmol), triphenylphosphine (481 mg, 1.83 mmol), and sodium acetate (1.50 g, 18.3 mmol) (Notes 4 and 5). The orange suspension is degassed three times, placed in a preheated (130°C) oil bath (Note 5), and stirred at 130°C for 12 hr (Note 6). Removal of the solvent at 40°C (0.1 mbar, 0.075 mm) gives a black oily residue, which is Chromatographed (5 x 40 cm column, silica gel 0.063 - 0.2 mm, 170 g, 1 cm of charcoal at the top of the column eluent hexane / diethyl ether 5 1), to yield 2.00 g (80%) of the lactone 4 as a slightly yellow solid. Recrystallization from diethyl ether / hexane delivers 1.63 g (65%) of colorless or pale yellow crystals (Note 7). 

The solution is evaporated to dryness under reduced pressure and the residue is purified by thin layer chromatography (PF-254G silica gel with 1 4 dichloromethane-hexane eluant). Three yellow bands are eluted. The second band is removed and product extracted from it is recrystallized from hexane. Yield 0.12-0.15 g (30-33%) of the desired product. Checkers used column chromatography (35 x 3-cm column, Silica Gel 60, 70-230mesh, Merck) to give the product as the second band when eluting with 1 4 dichloromethane-hexane. 

A suspension of 12 (25 g, 100 mmol) in CC13F (450 mL) was cooled to — 75 C and N2-diluted (10%) F2 gas (a total of 50 mmol P2) was bubbled into the mixture for about 10 h to give, after completion of the reaction, a brown suspension of IF and 1,. A cold solution of the alkene (10-20 mmol) in CHC13 (20 mL) was added, in one portion, to the mixture at — 75 C. After a few minutes at this temperature, the mixture was poured into dil aq Na2S203 (500 mL) it was washed with H20 until neutral, dried (MgS04) and evaporated. The crude product was purified by chromatography on a short column (silica gel. petroleum ether). 

To a stirred soln of diazirine 43 (5.0 g, 24.98 mmol) in CQ4 (100 mL) was added powdered NBS (4.44 g, 24.98 mmol) and the mixture warmed to 70 °C. AIBN (100 mg) was added and the temperature was gradually raised to reflux. After 20min, the mixture was cooled, the succinimide separated by filtration, and the filtrate concentrated in vacuo. Purification of the residue on a column (silica gel, petroleum ether/CH2Cl2 20 1) afforded the product as a colorless oil, which crystallized at -30 °C, but melted on warming to rt yield 4.8 g (69%). 

Diethyl 2-(acetylamino)malonate (3.85 g, 17.74 mmol) was added portionwise to Na (408 mg, 17.74 mmol) in absolute EtOH (30 mL). A soln of diazirine 46 (4.5 g, 16.1 mmol) in EtOH (10 mL) was added and the mixture was heated to 65 °C for 2h and then concentrated in vacuo. The residue was partially purified on a column (silica gel, CHCl /EtOH 20 1). The fractions containing the product were concentrated in vacuo and the residue was crystallized (EtOAc/Et20/petroleum ether) yield 3.33 g. Rechromatography of the mother liquor followed by crystallization gave further product (1.53 g total yield 73% mp 110-111 °C. 

A stirred soln of 20 (R1 = 3-methylindolyl 5.3 mmol) and freshly prepared NaOMe (5.8 mmol) in MeOH (40 mL) was treated with acrylonitrile (5.8 mmol). After 3 h of stirring at rt the mixture was neutralized with AcOH and the solvents were removed. The residue was purified on a column (silica gel, EtOAc/ hexane 1 2) to give 21 (R1 = 3-methylindolyl R2=CNEt) as a homogeneous syrup yield 74%. 

A solution of Et3N (1.87 g, 18.5 mmol) in CH2Cl2 (30 mL) was added portionwise over 5 min to a solution of r/A-3.4-dilluoro-l, 5-dioxaspiro[5.5]undecan-2-one in CH2C12 (60 mL) at rt. After stirring for 10 min, the mixture was washed with H20 and the organic layer dried (MgS04) and evaporated in vacuo. The residue was purified by column chromatography (short column, silica gel, hexane/F.lOAc 3 1) yield 1.55 g (47%) mp 61-62 C. 

Aldicarb, metabolites Hydrolysis, partition, column (silica gel) Sugarbeets GC 14... 

Carbaryl Column (silica gel) Cl8 cartridge Apples HPLC 52... 

Fig. 15. GPC elution curves for cellulose diacetate (CDA) whole polymers, run through a series of columns (silica gel SI-1000, 500, 150, and 50) in acetone at 25°C17>. Solid line CDA synthesized from wood pulp dotted line from cotton liner. GPC curves exhibit multiple peaks...

Apply the residue on a chromatography column (silica gel 300 g, CH2CI2 hexane, 1 1 as eluent). Di-protected alcohol 16b is obtained with CH2Cl2 hexane 75 25 as eluent. Increase the polarity to CH2Cl2 0-5% ethyl acetate to obtain pure compound 16a (37% yield). CH2CI2 10% ethyl acetate gives the dialdehyde compound 16c. 

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