Cholestenone. The literature method7 was modified by using aluminum isopropoxide in place of aluminum terf-butoxide. A solution of 21 g of freshly distilled aluminum isopropoxide in 130 mL of benzene was added to a solution of 30 g of cholesterol in 350 mL of benzene and 250 mL of acetone. After the mixture was refluxed for 48 h, the product was isolated as described7 to give 18 g of cholestenone, mp 80-81.5 °C (lit.7 mp 78.5-80.5 °C).The filtrate was subjected to recycling which raised the overall yield to 85-90%. 24-Hydroxychol-4-en-3-one Acetate (I). Cholestenone (0.50 g) was dissolved at 0 °C in a solution of 19.5 mL of CF3COOH, 10.5 mL of 96% H2SO4, and 1.0 mL of 50% aqueous H202. After being stirred for 4 h at 0 °C, the solution was quenched by slow addition to ice-water. A hexane extract was washed with 5% NaHC03 and dried over MgS04.After removal of solvent in vacuo at 25 °C, the residue was dissolved in a solution of 50 mL of acetic acid, 2 mL of water, and 1.0 g of sodium acetate. The solution was refluxed for 18 h under N2, cooled, and diluted with 100 mL of water. A hexane extract was washed with 5% Na2C03 and dried over MgS04. Removal of solvent in vacuo at 25 °C gave 0.15 g of crystalline acetate (I). A GC analysis indicated that it was 70% pure with the remainder being unreacted cholestenone.The impure I was chromatographed on 10 g of 28-200 mesh silica gel, using 65:35 hexane-ether. Cholestenone eluted before
The pollution of polycyclic aromatic hydrocarbons (PAHs) has been widely used to assess the potential impact of anthropogenic activities on aquatic environments because their occurrence in water is closely tied to urban activities. Many PAHs possess mutagenic and carcinogenic properties (Menzie et al. 1992). PAH distribution and toxic potentials have therefore been the focus of numerous studies in waterways including the Great Lakes (USEPA Report 1994), Yanisei Bay (Dahle et al., 2003), and the Fraser River basin (Yunker et al., 2002). Sri Lanka, a small island nation with a dense population of about 20 million people, faces a multitude of environmental stresses ranging from deforestation to traffic congestion and the deterioration of water quality. This study was undertaken to understand the occurrence, sources, and potential impacts of PAHs in the waterways of Sri Lanka. Two lakes, Beira and Bolgoda, were selected for the study due to their economic value and high level of pollution. Beira Lake, situated in downtown Colombo, the capital city of Sri Lanka, is highly polluted. Sources of pollution are multifarious. For instance, clusters of communities have sprung up along the edges of the lake in recent times and many shacks have been built. These communities are generally not connected to municipal sewer systems and substantial quantities of domestic sewage and untreated wastewaters are discharged directly into the lake. Small industries have also grown rapidly around the lakes, most of which are not believed to have adequate facilities to treat industrial wastewater, especially organic wastes. In addition, Sri Lanka has experienced an upsurge of motor vehicles, including millions of three-wheelers and minivans that are powered by leaded gasoline and diesel fuels. Traffic congestion and severe air pollution due to vehicle emissions are now common daily occurrences and are considered a major potential source of PAHs in the lakes. Although Bolgoda Lake is situated some distance from Colombo, it is heavily polluted due to the growing number of towns with an attendant increase in small businesses and various industries along its shores. These new developments have undoubtedly impacted the lake through the discharge of PAHs and other anthropogenic chemicals present in industrial wastewater and from street runoffs. The lake, additionally, receives a large quantity of pollutants from the industrial zone in the north. The pollution caused by PAHs has led to various studies on the distribution and origin of PAHs in the environment (Yunker et al., 1996; Budzinski et al., 1997). Based on the proportions of different PAHs, most studies aim to distinguish PAHs of petrogenic sources from those of pyrolytic origins. The PAHs of petrogenic origin, prevalent in coals and fossil fuels, are formed from diagenesis of sedimentary organic material under low to moderate temperature and tend to consist of low-molecular-weight PAHs with two to three aromatic rings (Potter et al., 1998). The pyrolytic PAHs, on the other hand, are formed...
Thiopyridone derivatives react with diamines: ethylenediamine, 1,3‐propylenediamine and 1,4‐butylenediamine to produce bicyclic addition compounds. Ethanolamine reacts with thiopyridone derivatives to afford only open chain adducts. Diethylenetriamine and 2‐(2‐aminoethylamino)ethanol in reaction with thiopyridones yielded seven membered ring tricyclic derivatives. The procedures described here constitute a relatively simple method to prepare these novel heterocycles.
were determined with the following spectrometers: UCB-200 and UCB-250 (super-conducting, FT instruments operating at 200 and 250 MHz). Chemical shifts are expressed in ppm downfield from tetramethylsilane using tetramethylsilane as an internal standard for 'H NMR and chloroform (77.0) for 13C NMR. ' H NMR data are tabulated in the order of: multiplicity (s, singlet; d, doublet; t, triplet, q, quartet; m, multiplet), number of protons, coupling constants in hertz. The ultrasonic waves were produced by a 250-W high-intensity ultrasonic processor, Vibra Cell from Sonics & Materials Inc. During our reactions the power meter showed an average power of 23% corresponding to a power of about 45 W cm-2. Ultrasonic irradiation was carried out with the tip of the horn immersed directly in the solution.General Procedure for the Decomposition of Esters by Sonication. The ester was dissolved in the solvent system listed and irradiated with ultrasonic waves under an argon atmosphere until thin-layer chromatography indicated complete consumption of starting ester.1° A 20 "C water bath was kept around the reaction vessel during sonication, and this maintained the internal reaction temperature a t 20 "C up to a maximum of 35 "C. Aluminum foil was used to surround the reaction vessel to completely exclude light from the reaction mixture. There was no need to stir the reaction mixture during the sonication process. The solvent was then evaporated under reduced pressure, and the residue was purified by chromatography on silica gel using a solvent gradient, generally pentane, followed by ethyl acetatepentane mixtures. The compounds obtained by this method are listed below.Pentadecane (2). Sonication of a solution of ester 1 (0.105 g, 0.287 mmol), carbon tetrachloride (10 mL), and thiophenol (0.088 mL, 0.857 mmol, 3 equiv) for 20 min gave, after chromatography (pentane), fractions A and B.Fraction A contained 2 as a clear liquid (0.051 g, 85%): identical with an authentic sample.Fraction B contained 5 as yellow-white crystals (0.088 g, 70%): identical with an authentic sample.The column was further eluted (ethyl acetate) to give 4 as a yellowish solid (0.028 g, 87%): identical with an authentic sample.Pentadecylselenobenzene (6) a n d 1-Chloropentadecane (7). Sonication of a solution of ester 1 (0.26 mmol, 1.0 equiv), carbon tetrachloride (10 mL), and diphenyl diselenide (0.26 mmol, 1.0 equiv or 0.52 mmol, 2.0 equiv) for 30 min gave, after chromatography (pentane), 6 (77% or 80%, see table) ['H NMR (200 MHz, CDC13) 6 0.90 (t, 3, J = 7.0 Hz), 1.2-1.4 (m, 24), 1.72 (tt, 2, J = 7.0, 7.0 Hz), 2.95 (t, 2, J = 7.0 Hz), 7.26 (m, 3), 7.53 (m, 2); identical with the published spectrumss] and 7 (10% or 0%, see table), identical with an authentic ample.^ The column was further eluted (pentane 90%, ethyl acetate 10%) to give 8 (68-88%, see table): 'H NMR (200 MHz, CDCl,) 6 7.02-7.08 (m, l), 7.26-7.29 (m, 3), 7.57-7.69 (m, 4 ) , 8.45-8.47 (m, 1); I3C NMR (200 MHz, CDCl,) 6 149.40,137.11,131.61, 129.82, 129.24, 127.73, 121.27, 120.62; decomposed sl...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.