- Gold-catalyzed 6-exo-dig cycloisomerization: A versatile approach to functionalized phenanthrenes
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A novel gold-catalyzed 6-exo-dig cycloisomerization of o-propargylbiaryls has been developed that provides ready access to functionalized phenanthrenes in largely good to excellent yields. Notable features of this method are readily available starting materials, mild reaction conditions, and broad substrate scope. Golden cat: A novel gold-catalyzed 6-exo-dig cycloisomerization of o-propargylbiaryls has been developed that provides ready access to functionalized phenanthrenes in largely good to excellent yields. Notable features of this method are readily available starting materials, mild reaction conditions, and broad substrate scope.
- Shu, Chao,Li, Long,Chen, Cheng-Bin,Shen, Hong-Cheng,Ye, Long-Wu
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p. 1525 - 1529
(2014/06/09)
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- Emission factors and importance of PCDD/Fs, PCBs, PCNs, PAHs and PM 10 from the domestic burning of coal and wood in the U.K.
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This paper presents emission factors (EFs) derived for a range of persistent organic pollutants (POPs) when coal and wood were subject to controlled burning experiments, designed to simulate domestic burning for space heating. A wide range of POPs were emitted, with emissions from coal being higher than those from wood. Highest EFs were obtained for particulate matter, PM10, (~ 10 g/kg fuel) and polycyclic aromatic hydrocarbons (~ 100 mg/ kg fuel for ΣPAHs). For chlorinated compounds, EFs were highest for polychlorinated biphenyls (PCBs), with polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) being less abundant. EFs were on the order of 1000 ng/kg fuel for ΣPCBs, 100s ng/ kg fuel for ΣPCNs and 100 ng/kg fuel for ΣPCDD/Fs. The study confirmed that mono- to trichlorinated dibenzofurans, Cl1,2,3DFs, were strong indicators of low temperature combustion processes, such as the domestic burning of coal and wood. It is concluded that numerous PCB and PCN congeners are routinely formed during the combustion of solid fuels. However, their combined emissions from the domestic burning of coal and wood would contribute only a few percent to annual U.K. emission estimates. Emissions of PAHs and PM 10 were major contributors to U.K. national emission inventories. Major emissions were found from the domestic burning for Cl1,2,3DFs, while the contribution of PCDD/F-ΣTEQ to total U.K. emissions was minor.
- Lee, Robert G. M.,Coleman, Peter,Jones, Joanne L.,Jones, Kevin C.,Lohmann, Rainer
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p. 1436 - 1447
(2007/10/03)
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- A new efficient route to the phenolic derivatives of chrysene and 5-methylchrysene, precursors to dihydrodiol and diol epoxide metabolites of chrysene and 5-methylchrysene, through Suzuki cross-coupling reaction
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A new, abbreviated synthesis of 5-methylchrysene (17), 2-hydroxychrysene (16), 8-hydroxy-5-methylchrysene (23), and 2-hydroxy-5-methylchrysene (24) is reported. The phenolic derivatives 16, 23, and 24 can easily be converted to carcinogenic dihydrodiol and diol epoxide metabolites of chrysene and 5-methylchrysene. The method entails the initial Suzuki cross-coupling reaction of naphthalene-2-boronic acid (1) and/or 6-methoxynaphthalene-2-boronic acid (2) with 2-bromo-5-methoxybenzaldehyde (3), methyl 2-bromophenylacetate (4), 2-bromophenylacetone (5), and/or 2-iodo-5-methoxyphenylacetone (6) to produce 2-(2-naphthyl)-5-methoxybenzaldehyde (7), methyl 2-(6-methoxy-2-naphthyl)phenylacetate (8), 2-(2-naphthyl)phenylacetone (9), 2-(2-naphthyl)-5-methoxyphenylacetone (10), and 2-(6-methoxy-2-naphthyl)phenylacetone (11) in 55-98% yields. 2-Methoxychrysene (15) was obtained with high regioselectivity by two different procedures. In the first procedure, the aldehyde function of 7 was elongated with trimethylsulfonium iodide under phase transfer conditions to generate the ethylene oxide 12 which after methanesulfonic acid treatment produced 15. The second procedure involved modification of ester 8 to its aldehyde analogue 14 which was subsequently treated with methanesulfonic acid to produce 15. Phenylacetone 10 was converted by methanesulfonic acid treatment into 8-methoxy-5-methylchrysene (18) with 90% regioselectivity. However, the similar cyclization of phenylacetones 9 and 11 to 5-methylchrysene (17) and 2-methoxy-5-methylchrysene (19) occurred with only 33-50% regioselectivity. The separation of 17 and 19 from their chromatographically similar 6-methylbenz[a]anthracene byproducts 20 and 22 was readily achieved by a chemical method. The methoxy derivatives of chrysene were finally demethylated with boron tribromide to the corresponding phenolic compounds in 90-98% yields.
- Kumar, Subodh
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p. 3157 - 3161
(2007/10/03)
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- A new abbreviated synthesis of 5-methylchrysene and its 2-hydroxy- and 8-hydroxy derivatives
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The Suzuki reaction has been applied to provide a highly abbreviated synthesis of 5-methylchrysene and its 2-hydroxy- and 8-hydroxy derivatives from easily accessible starting materials.
- Kumar, Subodh
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p. 6271 - 6274
(2007/10/03)
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- A NEW SYNTHESIS OF POLYCYCLIC AROMATIC HYDROCARBONS VIA TITANIUM(IV)-CATALYZED ALDOL-TYPE CONDENSATION OF SILYL ENOL ETHERS WITH 2-ARYLACETALDEHYDES
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Anovel one-pot synthesis of angular polycyclic hydrocarbon ring systems involving Ti(IV)-catalyzed aldol-type condensation of silyl enol ethers with 2-arylacetaldehydes and cyclization of the adducts is described.
- Raddo, Pasquale Di,Harvey, Ronald G.
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p. 3885 - 3886
(2007/10/02)
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