- Palladium-catalyzed domino coupling reactions of aryl halides with norbornene and norbornene derivatives - A simple route to polycyclic aromatic compounds
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Under palladium-catalysis, norbornene 1, dicyclopentadiene 10, norbornenol 13, and norbornenone 15 react with unsubstituted as well as substituted bromo- and iodobenzenes to give 1 : 3 coupling products with 4-aryl-9,10-dihydrophenanthrene units with up to 70% isolated yields. The structures of two such products 4a and 4e were proved by X-ray crystal structure analysis. 2-Bromothiophene 17 reacts with 1 and 10 to yield a mixture of 2 : 1 and 3 : 1 coupling products, while 3-iodopyridine 22a, 3-iodo-6-methylpyridine 22b and 4-iodopyridine 25 give only 2 : 1 coupling products with 5,6-dihydro-3,8-phenanthroline and 5,6-dihydro-2,9-phenanthroline units, respectively. Some new mechanistic insights into this interesting four-component domino coupling reaction are presented. The products can easily be transformed by photocyclization/dehydrogenation and/or flash vacuum pyrolysis to a variety of cyclopentadiene-anellated polycyclic aromatic compounds in very high yields. The reported sequence also presents the easiest access to benzo[e]pyrene.
- Albrecht, Karsten,Reiser, Oliver,Weber, Martin,Knieriem, Burkhard,De Meijere, Armin
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p. 383 - 401
(2007/10/02)
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- 1H and 13C Nuclear Magnetic Resonance Reinvestigation of the Dibenzocyclononatetraenyl Anion and Its 5,9-Diphenyl Derivative. Planarity vs Nonplanarity
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It is found that the dibenzocyclononatetraenyl anion is readily transformed into the stable 1H-cyclopentaphenanthren-1-yl anion.Earlier reported NMR data of this compound were incorrectly assigned to a planar structure of the dibenzocyclononatetraenyl anion.The nonplanarity of the initially formed nine-membered ring anion was confirmed both experimentally and theoretically.The ring-closure process does not take place in the anion of the 5,9-diphenyl derivative, which retains a nonplanar conformation of the nine-membered ring.
- Eliasson, Bertil,Nouri-Sorkhabi, M. Hossein,Trogen, Lars,Sethson, Ingmar,Edlund, Ulf,et al.
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p. 171 - 175
(2007/10/02)
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