- Facile one-pot fluorination of polycyclic aromatic hydrocarbons (PAHs) with N-fluoro-2,4-dinitroimidazole; scope and limitation
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The synthetic utility of N-fluoro-2,4-dinitro-imidazole NF-2,4-DNT, a recently introduced NF fluorinating agent, has been tested for direct one-pot fluorination of several classes of polycyclic aromatic hydrocarbons, PAHs, namely pyrene, crowded alkyl(cycloalkyl)-pyrenes; hexahydro-and tetrahydro-pyrene; benzo[a]anthracene; benzo[a]-and benzo[e] pyrene; perylene; 2,7-di-tert-butylphenanthrene;chrysene; 9-imethylanthracene and anthracene, as well as trans-15:16-dimethyl-dihydropyrene: azulene[2-a]lacenaphthylene and azulene. Although the isolated yields are modest, the ease of handling of the reagent, simple operation (reflux in dichloroethane for 3 days) and the use of 1.1 equivalent of the reagent makes the procedure quite attractive for polynuclear aromatics, avoiding multi-step operations (NO2-PAH → NH2-PAH → N2+-PAH → F-PAH) or the use of toxic or costly reagents (CF3OF, XeF2, etc.); it provides direct one-pot access to a variety of F-PAHs that are not readily made using: other fluorinating agents.
- Laali, Kenneth K.,Tanaka, Mutsuo,Forohar, Farhad,Cheng, Michael,Fetzer, John C.
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p. 185 - 190
(2007/10/03)
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- Synthesis and N.M.R. study of l-, 4-, 5- and 6-fluoroazulenes
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The preparation of four of the five possible fluoroazulenes is described. The 19F chemical shifts are compared with those of related aromatic systems. The 1H and 13C n.m.r. spectra have been assigned on the basis of 19F/13C coupling and of 1H/13C correlation. Problems with attempted syntheses of 2-fluoroazulene are outlined.
- Le, Van Phuc,Wells, Peter R.
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p. 1119 - 1122
(2007/10/03)
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- Synthesis and Properties of Fluoroazulenes. II. Electrophilic Fluorination of Azulenes with N-Fluoro Reagents
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1-Fluoro- and 1,3-difluoroazulenes were synthesized for the first time by the electrophilic fluorination of azulenes with N-fluoro reagents. Selective preparation of 1-fluoroazulenes were performed by the fluorination of methyl azulene-1-carboxylates, followed by demethoxycarbonylation in 100% H3PO4 2-Substituted azulenes were fluorinated in higher yields. In the 1HNMR of 1-fluoroazulene, long-range .JFH values were not observed at H-2 and H-8, in contrast to those for 1-fluoronaphthalene. The 1-fluorine atom causes significant bathochromic shifts in the visible absorption of azulene, due to the so-called +Iπ effect.
- Ueno, Tetsuya,Toda, Haruhiko,Yasunami, Masafumi,Yoshifuji, Masaaki
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p. 1645 - 1656
(2007/10/03)
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- The First synthesis of 1-Fluoro- and 1,3-Difluoroazulenes
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1-Fluoro- and 1,3-difluoroazulenes were synthesized by the reaction of azulene with N-fluoropyridinium salts in acetonitrile.Methyl azulene-1-carboxylates were also fluorinated to give the corresponding 3-fluoro derivatives.On the basis of the UV-visible acsorption spectra, the fluorine atom acts as an electron-donating group to the azulene ?-system due to the +I? effect.
- Ueno, Tetsuya,Toda, Haruhiko,Yasunami, Masafumi,Yoshifuji, Masaaki
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p. 169 - 170
(2007/10/02)
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