- Thermal cyclodehydrogenations to form 6-membered rings: Cyclizations of [5]helicenes
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Flash vacuum pyrolysis (FVP) of [5]helicene induces a thermal cyclodehydrogenation to form benzo[ghi]perylene. Evidence is presented that supports an electrocyclization-rearomatization mechanism and is inconsistent with mechanistic alternatives involving the intermediacy of aryl radicals or carbenes in the helicene fjord region.
- Xiang, Xue,Scott, Lawrence T.
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- Reactions of Perylene with Aryne Intermediates
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The Diels-Alder reactions of perylene (diene) with 1,2-didehydrobenzene and 4,5-dimethoxy-1,2-didehydrobenzene (dienophiles) generated in situ by two methods were studied. According to the first method, diazonium salts derived from anthranilic acids and stabilized by 4-dodecylbenzenesulfonic acid were treated with potassium fluoride in toluene in the presence of 18-crown-6 on heating. The second method involved generation of arynes directly from substituted anthranilic acids by the action of isoamyl nitrite in toluene on heating. The corresponding Diels-Alder adducts, naphtho[1,2,3,4-ghi]perylene and 10,11-dimethoxynaphtho-[1,2,3,4-ghi]perylene, were isolated in up to 77% yield. The yield was higher when the aryne intermediate was generated from the stabilized diazonium salts. 4,5-Difluoro-1,2-dehydrobenzene and 2,3-dehydronaphthalene generated by both methods failed to react with perylene.
- Pavlyuk,Gundala,Kovalev,Kopchuk,Krinochkin,Budeev,Zyryanov,Venkatapuram,Rusinov,Chupakhin
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- Gas-phase Diels-Alder cycloaddition of benzyne to an aromatic hydrocarbon bay region: Groundwork for the selective solvent-free growth of armchair carbon nanotubes
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Benzyne, generated in the gas phase by pyrolysis of phthalic anhydride, has been shown to undergo Diels-Alder cycloaddition to the bay region of perylene, a typical polycyclic aromatic hydrocarbon, under solvent-free conditions in a high temperature flow system. The initial cycloadduct spontaneously loses two hydrogen atoms, thereby rearomatizing to give naphtho[1,2,3,4-ghi]perylene. Analogous Diels-Alder cycloadditions of benzyne to bay regions on the rims of suitable cylindrical hydrocarbon templates, when followed by rearomatizations and thermal cyclodehydrogenations to join adjacent benzo groups, are proposed as key steps for a directed chemical synthesis of uniform diameter armchair carbon nanotubes.
- Fort, Eric H.,Scott, Lawrence T.
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- Oxidative Intramolecular C-C Bond Formation Reactions of 1,2-Diarylbenzenes: Syntheses of Highly Conjugated Double-Bridged Polycyclic Aromatic Hydrocarbons
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Oxidation reactions of 1,2-diarylbenzenes induce intramolecular C-C bond formation. The substrates studied were prepared by the stepwise Suzuki-Miyaura coupling reaction that introduced 2-naphthyl, 2-anthranyl, and 2-pyrenyl groups on the ortho -positions
- Islam, Md. Rafikul,Nishinaga, Tohru,Hirabayashi, Kazunori,Shimizu, Toshio,Sugiura, Ken-Ichi
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p. 383 - 392
(2021/10/05)
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- Photochemical Intramolecular Acylation of Polycyclic Aromatic o-Dicarboxylic Anhydrides
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The light-induced Diels-Alder addition of maleic anhydride to naphthochrysene (1) yields the same dicarboxylic anhydrides 2 and 4 as the thermal Diels-Alder addition. 4 is further isomerized by light to give the fluorenone carboxylic acid 6, as was revealed by isolation of compounds 7 and 8 after decarboxylation of the mixture 2 + 4.Analogously, 12 is formed by irradiation of the dicarboxylic anhydride 10; decarboxylation of 12 yields 13 and 14.The simpler systems 15 and 17 did not undergo an analogous light-induced isomerization.Photophysical examination of 4, 10, 15, and 17 gave no clue to the reasons for this difference in behaviour.
- Bunte, Reinhard,Gundermann, Karl-Dietrich,Leitich, Johannes,Polansky, Oskar E.,Zander, Maximilian
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p. 3521 - 3527
(2007/10/02)
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