- Synthesis of 1- and 3-nitrobenzo[a]pyrene
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The synthesis of the important carcinogens 1-nitrobenzo[α]-pyrene and 3-nitrobenzo[α]pyrene was achieved in four steps starting from the parent compound. A hexyl ester functionality was introduced as a removable blocking group, controlling the regioselectivity of the synthesis. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Dyker, Gerald,Kadzimirsz, Daniel,Thoene, Andreas
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- First examples of fluorinated and chlorinated polycyclic aromatic hydrocarbon (PAH) dications from benzo[a]pyrene, pyrene, and their alkyl- substituted derivatives
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Two-electron oxidations (SbF5/SO2ClF) of 6-fluoro-benzo[a]pyrene, 3, 6-chloro-benzo[a]pyrene 4, and their corresponding 7-methyl derivatives 5 and 6 as well as 1-fluoropyrene, 7, 1-chloropyrene, 8, and 1-fluoro-2,7-di-tert- butylpyrene, 9, allowed the charge delocalization mode, substituent effects, one-bond and long-range C/F coupling constants, and the tropicity of the resulting persistent PAH dications to be examined by NMR for the first time. For comparison, detailed NMR studies of the dications of 7- methylbenzo[a]pyrene, 2, and the parent benzo[a]pyrene, 1, are also reported. Total deshieldings ΣΔδ 13C in the resulting dications are ca. 195-211 ppm/e for the benzo[a]pyrenium and ca. 200-209 ppm/e for the pyrenium dications, respectively. Their AM1-calculated ΔΔH(f)(o) values are between 421 and 427 kcal/mol and 444 and 449 kcal/mol, respectively, well within the previously predicted dication formation limit of 463 ± 4 kcal/mol.
- Laali, Kenneth K.,Tanaka, Mutsuo,Hansen, Poul Erik
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- Behavior and prediction of photochemical degradation of chlorinated polycyclic aromatic hydrocarbons in cyclohexane
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The photochemical degradation of 11 chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and the corresponding 5 parent PAHs was examined to simulate the compound's fate on aerosol surfaces. All the ClPAHs and PAHs decayed according to the first-order reaction rate kinetics. The photolysis rates of ClPAHs varied greatly according to the skeleton of PAHs; the rates of chlorophenanthrenes (ClPhes) and 1-chloropyrene were higher than those of corresponding parent PAHs, whereas chlorofluoranthenes, 7-chlorobenz[a]anthracene and 6-chlorobenzo[a]pyrene were more stable under irradiation compared to respective parent PAH. Considering the photoproducts of ClPhes detected, the oxidation could occur immediately at positions of the highest frontier electron density. Finally, the quantitative structure-property relationship models were developed for direct photolysis half-lives and average quantum yields of the ClPAHs and parent PAHs, in which the significant factors affecting photolysis were ELUMO+1, total energy and surface area, and ELUMO, ELUMO - EHOMO and total energy, respectively.
- Ohura, Takeshi,Amagai, Takashi,Makino, Masakazu
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p. 2110 - 2117
(2008/09/19)
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- Radical Cations of Benzopyrene and 6-Substituted Derivatives: Synthesis and Reaction with Nucleophiles
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Radial cations of benzopyrene (BP) and 6-substituted derivatives were synthesized by two methods: reaction of the hydrocarbon with I2 and AgClO4 in benzene, and reaction of the hydrocarbon with NOBF4 in CH3CN/CH2Cl2.Both the radical cation perchlorates and tetrafluoroborates were stable for prolonged periods of time when stored under argon at subzero temperatures.The radical cations were reacted with nucleophiles of various strengths, namely H2O, AcO(1-) and F(1-), as a means of best characterizing these intermediates, as well as determining their chemical properties.Reaction of BP, 6-FBP, 6-ClBP, and 6-BrBP radical cation perchlorates with H2O produced BP 1,6-, 3,6-, and 6,12-dione, whereas the radical cation derived from 6-CH3BP yielded 6-CH2OHBP.When BP(.1+)ClO4(1-) and 6-FBP(.1+)ClO4(1-) were reacted with NaOAc in H2O/CH3CN (9:1), 6-OAcBP was formed, in addition to the quinones. 6-ClBP(.1+)ClO4(1-) formed a small amount of 1-OAc-6-ClBP and 3-OAc-6-ClBP, in addition to the diones, whereas for 6-BrBP(.1+)ClO4(1-) and 6-CH3BP(.1+)ClO4(1-) the reaction products were BP diones and 6-CH2OHBP, respectively.Reactions conducted under anhydrous conditions, using tetramethylammonium acetate in CH3CN, gave similar results, except that no quinones were formed.These results confirm the reactivity of nucleophiles at the postions of high charge localization in the BP(.1+), i.e.C-6, followed by C-1 and C-3.
- Cremonesi, Paolo,Stack, Douglas E.,Rogan, Eleanor G.,Cavalieri, Ercole L.
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p. 7683 - 7687
(2007/10/02)
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- One-Electron Oxidation of 6-Substituted Benzopyrenes by Manganic Acetate. A Model for Metabolic Activation
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Radical cations of benzopyrene (BP) and 6-substituted derivatives were generated by one-electron oxidation with 2 equiv of Mn(OAc)3*2H2O.Some of the properties of these radical cations were investigated by nucleophilic trapping with acetate ion.BP produced predominantly 6-OAcBP and small amounts of BP 1,6-, 3,6-, and 6,12-dione. 6-FBP yielded 6-OAcBP, a mixture of 1,6-(OAc)2BP and 3,6-(OAc)2BP, and BP diones.In the case of 6-ClBP and 6-BrBP the major products obtained were a mixture of the 1-OAc and 3-OAc derivatives, and BP diones, while substantial starting material remained unreacted. 6-CH3BP afforded mostly 6-OAcCH2BP, a mixture of 1-OAc and 3-OAc derivatives of 6-CH3BP, and a mixture of 1-OAc and 3-OAc derivatives of 6-OAcCH2BP.These results indicate that nucleophilic substitution of BP-radical-cation and 6-FBP-radical-cation occurs exclusively at C-6.For 6-ClBP-radical-cation and 6-BrBP-radical-cation substitution at C-1 and C-3, which are the positions of second highest charge density in their radical cations after C-6, complete successfully for nucleophilic substitution.For 6-CH3BP-radical-cation charge localization at C-6 activates the methyl group rendering it the most reactive toward nucleophilic attack.Competitive acetoxylation of 6-CH3BP-radical-cation also occurs to a minor extent at C-1 and C-3.These mechanistic studies have been useful in clarifying some aspects of the metabolism of BP and its halogeno derivatives by cytochrome P-450 and peroxidases.Furthermore, this chemistry can provide some guidance in understanding the mechanism of tumor initiation by these compounds.
- Cremonesi, Paolo,Cavalieri, Ercole L.,Rogan, Eleanor G.
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p. 3561 - 3570
(2007/10/02)
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