- NMR and DFT study on onium ions derived from substituted fluoranthenes and benzo[κ]fluoranthenes
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Fluoranthene and benzo[k]fluoranthene (3) are nonalternant polyaromatic hydrocarbons. Their derivatives, 3-acetyl, 8-acetyl, 3-nitro, and 3-aminofluoranthenes (4, 5, 7, and 8) were reacted in FSO3H/SO 2ClF and the solutions were observed by NMR measurements at low temperatures, which showed the formation of PAH-substituted onium ions. The most deshielded 13C peaks in fluoranthene frames were observed at 155.7 and 148.7 ppm for 4H+, 154.4 ppm for 5H+, 159.1 and 139.6 ppm for 7H+, and 139.7 ppm for 8H+. Distribution of the positive charges were estimated on the basis of changes in 13CNMR chemical shifts between onium ions and their corresponding parent compounds. Only limited delocalization of positive charges into the aromatic rings was found to occur. GIAO-derived NMR chemical shifts calculated by the DFT method were generally consistent with the experimental chemical shifts. DFT calculations suggested that benzo[k]fluoranthene (3) is favored to be protonated at C-3/C-7 positions. GIAO-derived NICS(1)zz were computed to elucidate aromaticity/antiaromaticity, and the results suggested that the five-membered rings are antiaromatic for cations 4H+, 7H+, 8H +, and 3aH+ (3-benzo[k]fluoranthenium ion).
- Okazaki, Takao,Adachi, Taisuke,Kitagawa, Toshikazu
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p. 464 - 471
(2013/05/22)
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- A new class of heterogeneous platinum catalysts for the chemoselective hydrogenation of nitroarenes
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A new series of nanostructured platinum catalysts able to catalyze the selective reduction of nitroarenes has been developed. The materials, made of organosilica physically doped with nanostructured platinum(0), are stable and efficient. Reactions in general proceed with high yield and often go to completion, while the catalysts can be reused in further reaction runs. This establishes a new class of relevant solid catalysts for synthetic organic chemistry named SiliaCat Platinum-Hydrogel.
- Pandarus, Valerica,Ciriminna, Rosaria,Beland, Francois,Pagliaro, Mario
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scheme or table
p. 1306 - 1316
(2011/06/25)
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- Efficient method for the synthesis of N-cyclic maleamic acids and N-cyclic maleimides
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Provided are methods for the synthesis of N-cyclic maleamic acids and N-cyclic maleimide derivatives, as well as N-cyclic maleamic acids and N-cyclic maleimides synthesized thereby. The method for synthesis of an N-cyclic maleamic acid involves reacting an amino group-containing N-cyclic compound with maleic anhydride in acetic acid to obtain an N-cyclic maleamic acid. An N-cyclic maleimide can be formed by adding hexamethyldisilazane to an N-cyclic maleamic acid prepared according to the above-described method, thereby cyclizing a maleamic acid site of the N-cyclic maleamic acid. The described methods allow for the products to be obtained at high yields.
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- Metabolic activation of the genotoxic environmental contaminants 2- and 3-nitrofluoranthene in variants of Salmonella typhimurium TA98
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The mutagenic environmental pollutants 2-nitrofluoranthene (2-NFA) and 3-nitrofluoranthene (3-NFA), labelled with 3H and 14C respectively, were incubated with Salmonella typhimurium strain TA98, its nitroreductase-deficient variant TA98NR and its O-acetytransferase-deficient variant TA98/1,8-DNP6, to investigate the activity of these metabolic pathways under conditions approximating those of the Ames assay, hence their contribution to mutagenic potency. 2-Aminofluoranthene (2-AFA) was the major metabolite of 2-NFA (4 μM) in all three TA98 variants, isolated by reverse-phase HPLC and identified by UV-vis and NMR spectroscopy and mass spectrometry. 2-AFA was formed more slowly in TA98NR (65 pmol/h/ml resting phase bacterial broth, 1 to 2E9 bacteria/ml) than in TA98 (295 pmol/h/ml) or TA98/1,8-DNP6 (82 pmol/h/ml). 2-Acetamidofluoranthene (2-AAFA) was also identified in incubations with TA98 (80 pmol/h/ml), TA98NR (21 pmol/h/ml), and TA98/1,8-DNP6 (8 pmol/h/ml). 3-Aminofluoranthene (3-AFA, confirmed by UV-vis and NMR spectroscopy and mass spectrometry) was formed by all three variants from 3-NFA (4 μM): TA98, 1.76 nmol/h/ml; TA98NR, 0.55 nmol/h/ml; TA98/1,8-DNP6, 2.93 nmol/h/ml. 3-Acetamidofluoranthene (3-AAFA) was not detected in any of the variants. 3-AFA and 3-AAFA were less mutagenic than 3-NFA, and required S9 for activation. Mutagenicity of 3-NFA relative to initial nitroreduction rate was similar in TA98 and in TA98NR, but almost 10-fold lower in TA98/1,8-DNP6; hence O-acetylation considerably anhances the mutagenicity of reduction products of 3-NFA. Mutagenicity of 2-NFA relative to initial nitroreduction rate was similar in TA98 and in TA98/1,8-DNP6; the bacterial genotoxicity of 2-NFA is therefore largely independent of O-acetyltransferase activity. Ratios of mutagenicity to nitroreduction rate were similar in TA98 for 2-NFA and 3-NFA; differences in the potency of these isomers arise primarily from their respective suitabilities as substrates for nitroreductase enzymes.
- Ball, L. M.,Stocking, L. M.,Kohan, M. J.,Warren, S. H.,Lewtas, J.
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p. 497 - 504
(2007/10/03)
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- Synthesis and characterization of nitro-, nitroso-, and aminofluoranthenes
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The synthesis is reported of the five mononitrofluoranthenes. 1-Nitrofluoranthene was synthesized in 20percent from fluoranthene, 2-nitrofluoranthene in 24percent from 1,2,3,10b-tetrahydrofluoranthene, 3-nitrofluoranthene in 13percent from fluoranthene and 7- and 8-nitrofluoranthene in 34percent from 1,2,3,10b-tetrahydrofluoranthene.The pure nitrofluoranthenes were converted into their nitroso and amino analogues.The nitrosopyrenes were also synthesized.Characterisation of each compound is described.
- Haeringen, C. J. van,Aten, N. F.,Cornelisse, J.,Lugtenburg, J.
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p. 335 - 344
(2007/10/02)
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