Cyclopentane Ethyl acetate

To a stirred solution at 20°C of 75 g of (+)-2p,4p-dihydroxy-3a-iodo-5a -(methoxymetyl)cyclopentane-ip-acetic acid y-lactone (M.P. 101-102°C, [a]D = -50° (c 0.98, CHCI3) in 135 ml of dry pyridine was added 30.4 ml of benzoyl chloride. After 30 min, 250 ml of toluene was added and the resulting solution evaporated to dryness under reduced pressure. The residue was dissolved in 1000 ml of ethyl acetate. The organic solution was washed with 200 ml 20% of aqueous sulfuric acid and 200 ml of brine. The aqueous solution was washed with 200 ml of ethyl acetate. The ethyl acetate solution was dried and evaporated under reduced pressure to give 95 g of oil which crystallized. The crude product was recrystallized to give 90 g of the white solid, M.P. 84-86°C, [a]D = +5° (c 1.03, CHCI3). 

To a solution of 20 g of (-)-3a,5a-dihydroxy-2p-(hydroxymethyl)cyclopentane-la-acetic acid y-lactone 3-benzoate in 320 ml of methylene chloride under nitrogen atmosphere and cooled in an ice bath was added dropwise 24.8 ml of boron trifluoride in 320 ml of methylene chloride. After 1 hour to the solution was added 78 g of sodium carbonate in 200 ml of water and then 66 g of solid sodium chloride. The aqueous phase was extracted with ethyl acetate. Yield of (-)-3a,5a-dihydroxy-2p-(methoxymethyl)cyclopentane-la-acetic acid... 

To a solution of 0.50 g of (-)-3a,5a-dihydroxy-2p-[(3RS)-3-hydroxy-3-methyl-trans-octenyl]cyclopentane-la-acetic acid - lactone 3-benzoate in 15 ml of tetrahydrofuran at -78°C under nitrogen was added 10 ml of 10% diisobutylaluminum hydride in toluene. After a gas evolution was ceased, the reaction was quenched by addition of 10 ml of saturated aqueous ammonium chloride. The resulting mixture was stirred at room temperature, filtered through Celite, and extracted with ethyl acetate. Extract was evaporated to give 0.48 g of (-)-3a,5a-dihydroxy-2p-[3-(RS)-3-hydroxy-3-methyl-trans-octenyl]cyclopentane-l-a-acetaldehyde y-lactol 3-benzoate as an oil. 

Four frequently used normal-phase (NP) solvents will be discussed in detail hexane, dichloromethane, isopropyl alcohol, and ethyl acetate. Hexane is one of the most frequently used NP solvents. As in the case of acetonitrile, the low UV cutoff wavelength of 195 nm and the low background absorbance at and above 210nm make hexane an excellent choice for the majority of compounds analyzed in the NP mode (see Fig. 1.2). (Note that cyclopentane, cyclohexane, and heptane have similar UV characteristics.) In addition, under normal circumstances hexane has excellent long-term chemical stability. Because of the limited solubility of hexane, and of related hydrocarbons, in water and acetonitrile, their use in reversed-phase separations is rare. 

A modification of this method utilizes the direct conversion of l,2-bis(trimethyl-siloxy)cyclobutene in one step to 2,2-disubstituted cyclopentane-1,3-diones. For example, 2-ethyl-2-methylcyclopentane-l,3-dione (3) was obtained in 91% yield from 1.2-bis(trimethyl-siloxy)cyclobutene and butan-2-one 2,2-dimethylpropane-l,3-diyl acetal.41 Further examples... 

Cyclopentan 2-(l-Ethylthio-1 -methyl-ethyl)-2-oxo- E19c, 342 (S,S-Acetal + O-Si-enol)... 

Concurrently, Noels had reported that rhodium carboxylates smoothly catalyze the intermolecular C—H insertion of ethyl diazoacetate into alkanes. Following up on this report, Taber demonstrated that the open chain a-diazo 3-keto ester (60) cyclizes smoothly under rhodium acetate catalysis to give the corresponding cyclopentane (61 equation 24). In contrast to the copper-mediated cyclization cited above (equation 22), the six-membered ring product is not observed. The insertion shows significant electronic selectivity. Although there is a 3 1 statistical preference for methyl C—H, only the methylene C—H insertion product (61) is observed (equation 24). 

Acetone Ethyl formate Methyl acetate 1 -Chloropropane Isopropyl nitrite Propyl nitrite Isopropyl alcohol Methylal tert-Butyl alcohol Ethyl ether Cyclopentane Pentane... 

Isobutyl alcohol Ethyl sulfide Cyclopentane 2-Methyl-2-butene 3>Pentanone Isobutyl formate Methyl isobutyrate Propyl acetate l-Bromo-3-methylbutane... 

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