Chromatography on silica gel

Hydrocarbon groups (FIA method) NF M 07-024 ISO/DIS 3837 ASTM D 1319 Chromatography on silica gel with fluorescent indicators... 

The irradiation of tetra-/-butylcyclopentadienone with 254 nm light at 77 K produced a tricyclopentanone which, upon extended irradiation, lost carbon monoxide. Tetra-f-butyltetrahedrane was formed. This derivative of the second fundamental hydrocarbon of molecular formula (CH), namely tetrahedrane, is stable at room temperature and could be isolated after chromatography on silica gel in crystalline form (G. Maier, 1978). 

A solution of benzyl indole-5-carboxylate(1.0g, 3.98 mmol) and methyl 4-(bro-momethyl)-3-methoxybenzoate (2.06 g, 7.97 mmol) in dry DMF (10 ml) was heated at 80°C for 24 h. The reaction solution was cooled, poured into water (100 ml) and the product extracted with EtOAc (3 x 75 ml). The extract was washed with water and brine and dried over MgSO, . The product was obtained by evaporation of the solvent and purified by chromatography on silica gel using 1 4 EtOAc/hexane for elution. The yield was 1.11 g (32%) and some of the indole (30%) was recovered unreacted. 

Potassium hydride (1 eq.) was washed with hexanes and suspended in anhydrous ether at 0°C. 7-Bromoindole was added as a solution in ether. After 15 min, the solution was cooled to — 78°C and t-butyllithium (2 eq.) which had been precooled to — 78°C was added by cannula. A white precipitate formed. After 10 min DMF (2 eq.) was added as a solution in ether. The reaction mixture was allowed to warm slowly to room temperature and when reaction was complete (TLC) the suspension was poured into cold 1 M H3PO4. The product was extracted with EtOAc and the extract washed with sat. NaHCOj and dried (MgS04). The product was obtained by evaporation of the solvent and purified by chromatography on silica gel (61% yield). 

To a stirred ice-cold solution of ethyl 3,6-dihydro-5-hydroxy-8-methyl-6-(phenylsulfonyl)benzo[l,2-b 4,3-b ]dipyrrole-l-carboxylate (368 mg, 0.85 mmol) in TEA (3ml) was added EtjSiH (1.5 ml), After 15 min the solution was allowed to come to room temperature and stirred for an additional 2h. The solution was evaporated in vacuo and the residue dissolved in CH2CI2 (10 ml), washed.with aq. NaHCOj and dried over MgS04. The solution was mixed with AcjO (1ml) and CH2C12 (1ml) and kept at room temperature for 2 h. The reaction mixture was evaporated and the residue purified by chromatography on silica gel using CHjClj-EtOAc (3 1) for elution. The product (271 mg) was obtained in 71 % yield. 

To a solution of indoline (20 mM in MeOH) was added Co(salen) (0.10 equiv.) and O2 was bubbled through the suspension at 25°C. After 1 h the suspension became homogeneous and the solvent was removed in vacuo and the product purified by chromatography on silica gel. 

This ester is formed by standard procedures and is readily cleaved with Pd(Ph3P)4 in CH2CI2 to form trimethylsilyl esters that readily hydrolyze on treatment with water or alcohol or on chromatography on silica gel (73-98% yield). Amines can be protected using.the related carbamate. ... 

A-(9-Acridinyl)maleiinide (NAM) [49759-20-8] M 274.3, m 248 , 255-258 . Purified by chromatography on silica gel using CH2CI2 as eluant. Evaporation of pooled fractions that gave the correct NMR spectra gave a solid which was recrystd from Me2CO as pale yellow prisms. IR v (nujol) 1710 (imide) UV (MeOH) (nm), (e M- cm ) 251 (159 500), 343 shoulder (7 700), 360 (12 400) and 382shoulder (47... 

Anthrarufin [l,5-dihydroxy-9,10-anthraquinone] [117-12-4] M 240.1, m 280 (dec), pKj 9.90, pK 11.05. Purified by column chromatography on silica gel with CHCl3/Et20 as eluent, followed by recrystn from acetone. Alternatively recrystd from glacial acetic acid [Flom and Barbara J Phys Chem 89 4489 1985]. 

Bismethylaminoanthraquinone (Disperse Blue 14) [2475-44-7] M 266.3, A,max 640 (594)nm. Purified by thin-layer chromatography on silica gel plates, using toluene/acetone (3.1) as eluent. The main band was scraped off and extracted with MeOH. The solvent was evapd and the dye was dried in a drying pistol [Land, McAlpine, Sinclair and Truscott J Chem Soc, Faraday Trans I 72 2091 7976]. 

Purified by chromatography on silica gel in CHCl3/pet ether (1 2) followed by crystn from aqueous EtOH. [Phillips and Cohen J Am Chem Soc 108 2023 7956.]... 

VinyIanthracene [2444-68-0] M 204.3, m 65-67 , b 61-66 /10mm. Purified by vacuum sublimation. Also by chromatography on silica gel with cyclohexane as eluent, and recrystd from EtOH [Werst et al. J Am Chem Soc 109 32 1987],... 

Dibenzyl-14-crown-4 (lithium ionophore VI 6,6-dibenzyl-l,4,8,ll-tetra-oxa-cyclo-tetradecane) [106868-21-7] M 384.5, m 102-103°. Dissolve in CHCI3, wash with saturated aqueous NaCl, dry with MgSOa, evaporate and purify by chromatography on silica gel and gradient elution with C6Hg-MeOH followed by preparative reverse phase HPLC on an octadecyl silanised silica (ODS) column and eluting with MeOH. It can be crystd from MeOH (v Br 120 cm , C-O-C). [7 Chem Soc Perkin Trans 1 1945 1986.]... 

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.]... 

The resulting product is purified by thin layer chromatography on silica gel in methylene dichloride yielding 8)S-di-5a-cholestane-3,6-dione (162) 13 mg, overall yield 26% mp 160-164°, which consists of 83% of dj-species. 

When the reaction of S2CI2 with ammonia is carried out in a polar solvent, e.g., DMF, the hydrolysis of the reaction mixture with aqueous HCl produces a mixture of the cyclic sulfur imides S7NH, 1,3-, 1,4- and 1,5-S6(NH)2 and 1,3,5- and 1,3,6-S5(NH)3, which can be separated by chromatography on silica gel using CS2 as eluant (Section 6.2.1). °... 

B. Methyl indole-4-carboxylate (30). A mixture of 7.0 g (28 mmol) of methyl trans-2-[ -(dimethylamino)vinyl]-3-nitrobenzoate(29) in 140 mL of dry benzene which contained 1.4 g of 10% Pd/C was shaken in a Parr apparatus under Hj (50 psi) for 1.5 h. The catalyst was removed by filtration, and the benzene solution was washed with 30 mL of 5% aq. HCl, brine and dried over MgS04. After removal of the solvent under reduced pressure, the residue was purified via chromatography on silica gel to furnish 6.9 g (82%) of methyl indole-4-carboxylate (30). 

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... 

Benzhydryl 3Sodium hydride, 24 mg (4B mg of a 50% suspension of NaH in mineral oil, which has been washed with hexane to remove the oil), is added. When hydrogen evolution has ceased, 126 mg dimethyl sulfate is added. The solution is stirred for one hour at room temperature,diluted with 100 ml benzene and washed six times with water the last wash is made to pH B, if necessary, by adding sodium bicarbonate. The solution is dried over MgS04, filtered and evaporated, leaving benzhydryl 3eluting with 25 1 chloroform-ethyl acetate. 

After further working up there is obtained an oily crystalline residue which is subjected to chromatography on silica gel. The 16a-methyl-6a,9a-difluoro-A -pregnadien-11/3,21-diol-3,20-dione is eluated with ethyl acetatereacted with valeric acid chloride to give the valerate ester. 

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