Ethyl hexane

DIMETHYL-HEXANE 3-ETHYL-2-METHYLPENTANE 3-ETHYL-3-METHYLPENTANE... 

The best separation of plastid pigments were received chloroform -hexane - ethyl alcohol (20 100 1) solvent mix. 

Geraniol [106-24-1] M 154.3, b 230 , d 0.879, n 1.4766. Purified by ascending chromatography or by thin layer chromatography on plates of kieselguhr G with acetone/water/liquid paraffin (130 70 1) as solvent system. Hexane/ethyl acetate (1 4) is also suitable. Also purified by GLC on a silicone-treated column of Carbowax 20M (10%) on Chromosorb W (60-80 mesh). [Porter Pure Appl Chem 20 499 7969.] Stored in full, tightly sealed containers in the cool, protected from light. 

In a 500-ml round-bottom flask is placed a mixture of 25 g (0.178 mole) of dimedone, 21.8 g (0,22 mole, 25 % excess) of pulverized maleic anhydride, 0.1 g of /7-toluenesulfuric acid, and 150 ml of isopropenyl acetate. The mixture is refluxed for 72 hours, then cooled, and the acetone is removed at room temperature on a rotary evaporator. The resulting solution is cooled to —20° in a Dry Ice bath, whereupon the product crystallizes. It is collected by filtration to yield the crude product in about 80% yield. Recrystallization from hexane-ethyl acetate and decolorization by Norit gives colorless crystals, mp 164-166°. 

The precursors dissolved in a hexane/ethyl acetate mixture (90 10, v/v) are adsorbed on a silica gel column that has been packed with hexane. The precursors were eluted with hexane/ethyl acetate mixtures, 80 20, 70 30, and 60 40 (v/v), in that order. 

A solution of 0.11 mol of 1.5M butyllithium in hexane is added to 30 mL of THF under a layer of argon or nitrogen at —78 C, followed by 0.10 mol of (4S,5/ )-1-allyl-3,4-dimcthyl-5-phenyl-2-imidazolidinone in 75 mL of THF. After 25 min, a solution of 0.11 mol of chlorotris(diethylamino)titanium in 30 mL of THF is introduced. The mixture is stirred at — 20 °C for 45 min, then 0.11 mol of the aldehyde or ketone in 10 mL of THF is added. After 2 h. 20 mL of water and 200 mL of diethyl ether are added. The ethereal solution is separated, washed with 20 mL of 10% aq NaHS03 followed by 20 mL of water, dried over Na2S04 and concentrated, whereupon the product crystallizes. Diastereomerically pure samples are prepared by recrystallization from hexane or hexane/ethyl acetate. 

A mixture of 10 mmol of the allyl bromide and 10-15 mmol of the aldehyde, dissolved in 20 mL of THF, is added dropwise at — 5 to 0°C to the chromium(II) chloride solution in THF prepared by method A or B. The mixture is stirred for 36 h at this temperature and then 15 mL of sat. sodium hydroxide and 20 g of anhyd Na2S04 are added stirring is continued for 20 min at 201C. The mixture is filtered over a pad of Celite/Na2S04 (7 l). The filtrate is concentrated and the residue purified, usually by chromatography on silica gel with pentane/diethyl ether or hexane/ethyl acetate. 

Conjugate Addition. To a solution of 1.5 mmol of lithium dialkylcuprate at — 25 CC is added 1 mmol of methyl ( )-3-[(25,45,55)-3-benzyloxycarbonyl-4-methyl-5-phenyl-2-oxazolidinyl]-propenoate dissolved in 1 mL of dry diethyl ether. After 30 ntin at — 25 C, the mixture is treated with an aq NH3/NH4C1 pH 8 buffer solution and then stirred at r.t. for 15 min. After diethyl ether extraction, the organic layers are dried over Na,S()4 and filtered and the solvent is evaporated under reduced pressure. The crude products are checked by H- and l3C-NMR analyses in order to determine the diastereomer ratios (g 95 5) and then purified by flash chromatography (hexane/ethyl acetate 80 20) yield 70-72%. 

A solution of 4.5 g (19.9 mmol) 4-(fm-butyldimethylsilyloxy)-2-cyclohexenone and 452 mg (1 mmol) of mercury(II) iodide is stirred at r.t. for 15 min and then cooled to — 78 °C. 5.03 g (24.8 mmol) of 1-ethoxy-1-(tm-bulyl(iimethylsilyloxy)ethene are added dropwise during 15 min. The mixture is stirred at — 78 °C for 2 h, quenched with 302 mg (3 mmol) of triethylamine and allowed to warm to r.t. The mixture is filtered through a short (3 cm) column of silica gel (deactivated with a 5% triethylamine solution in hexane/ethyl acetate, 10 1) eluting with hexane/ethyl acetate (10 1) and concentrated in vacuo. Purification of the crude material by flash chromatography (silica gel, hcxanc/cthyl acetate 30 1) gave the adduct as a colorless oil yield 7.98 g (18.7 mmol, 94%) d.r. (cisjtrans) 95.2 4.8. 

Isolation of Citronellal and Citral. At the close of each experiment (7 to 10 days), the nests were frozen intact. Groups of 200 workers were placed in a micro-Soxhlet apparatus and extracted for 8 hours with methylene chloride. A few milligrams of carrier citronellal and citral were added and the mixture was applied to a thin-layer chromatoplate (silica gel G) which was developed with hexane-ethyl acetate (92 to 8) to separate citronellal and citral (3). The aldehydes were detected by spraying with a solution of 2, 4-dini-trophenylhydrazine in tetrahydrofuran (20) and the citronellal and citral peaks were scraped off and allowed to react with excess dinitro-phenylhydrazine reagent for a further 12 hours. 

TLC analysis (elution with 1 1 hexanes ethyl acetate) indicated that the reaction was not complete after 5 hr heating was continued overnight. 

TLC analysis indicated that the reaction was complete. TLC was performed on pre-coated plates with silica gel 60 F254 purchased from EM Sciences (Merck) using hexanes/ethyl acetate (1/1) as the eluent. 

The Diels Alder reactions of maleic anhydride with 1,3-cyclohexadiene, as well the parallel reaction network in which maleic anhydride competes to react simultaneously with isoprene and 1,3-cyclohexadiene [84], were also investigated in subcritical propane under the above reaction conditions (80 °C and 90-152 bar). The reaction selectivities of the parallel Diels-Alder reaction network diverged from those of the independent reactions as the reaction pressure decreased. In contrast, the same selectivities were obtained in both parallel and independent reactions carried out in conventional solvents (hexane, ethyl acetate, chloroform) [84]. 

Succinimide (9.9 g, 100 mmol), ethyl cyanoacetate (21.28 mb, 200 mmol), HMDS 2 (42.2 mb, 200 mmol), and (NH4)2S04 (0.7 g, 5 mmol) are heated for 34 h under reflux with magnetic stirring. After cooling the colored residue is chromatographed on a silica gel column (25 cm X 6 cm i.d.) with hexane-ethyl acetate (1 1) as mobile phase. The first fractions contain ca 3% pure bis-product 382,... 

MesSiNs 19 (0.34 rtiL, 2.,4 mmol) and of Et2NCOCl (0.32 mL, 2.4 mmol) are added, in this sequence, under argon, to a solution of 3-aminopyrazine-l-oxide 934 (1 mmol) in abs. MeCN (8 mL) and the reaction mixture is heated under reflux for 18 h with exclusion of humidity. After evaporation in vacuo the residue is chromatographed with hexane-ethyl acetate (10 1 to 3 1) on a column of 20 g silica gel to give almost quantitative yield of microcrystalline 2-amino-3-azidopyrazine 935, m.p. 225 °C (dec.) [55] (Scheme 7.56). 

TMSOTf 20 (0.11 g, 0.5 mmol) is added to a solution of a-phenyl-N-methylni-trone 976a (0.68 g, 5.0 mmol) and allyltrimethylsilane 82 (0.69 g, 6 mmol) in dry CH2CI2 (5 mL). After 36 h at room temperature the reaction mixture is quenched with 3 M aqueous HCl and stirred for 1 h. After neutralization with 3 M NaOH, extraction with Et20 (2x25 mL), and evaporation the residue is purified by flash chromatography on silica gel with hexane-ethyl acetate (7 3) to give 0.763 g (86%) 978a as a crystaUine solid, m.p. 93-95°C [70] (Scheme 7.59). 

A solution of 1 mmol 1017 in 4 mL dry DMF is treated with MesSiCl 14 (0.63 mL, 5 mmol) then with triethylamine (0.7 mL, 5 mmol) at room temperature. After stirring until completion of the reaction the mixture is poured into dilute HCl, extracted with ethyl acetate, and the product isolated by column chromatography on sihca gel with hexane-ethyl acetate (3 1) as mobile phase to give, on crystallization from ethyl acetate, 91% N-hydroxyindole 1019, m.p. 218-220 °C (dec.) [93, 94] (Scheme 7.63). 

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