A “Perturbed [16]annulene”—this is one way to view the much discussed dipleiadiene, 1, which has finally been obtained in the course of an investigation having an entirely different goal. Although 1 is formally a naphthalene that is peri‐bridged by butadiene structural units, it exhibits pronounced paratropism.
1,6‐Methano[10]Annulene intermediate: 1,4,5,8‐ Tetrahydronaphthalene ( isotetralin ) intermediate: 11,11‐ Dichlorotricyclo [4.4.1.0 1,6 ] undeca ‐3,8‐ diene intermediate: Tricyclo [4.4.1.0 1,6 ] undeca ‐3,8‐ diene product: 1,6‐ Methano [10] annulene intermediate: 2,3‐dichloro‐5,6‐dicyanohydroquinone
of 2 and 4JZ1 and in terms of an increased conjugative interaction between the hydrocarbon framework and the CO groups (5 a15 b) in the case of 5.Among the chemical reactions of 5, that which deserves special attention, aside from the protonation and reductive acetylation already mentioned, is its reduction with sodium borohydride in methanol/dichloromethane. The reaction product formed thereby-formally with saturation of the central C=C bond-is the lOb,IOc-dihydro compound, the no longer planar syn-I ,6:8,13-ethanediylidene[l4]annulene-7,14-dione 4 [red rhombs (from acetone/hexane); slow decomposition above 165°C; yield 20%]; when dissolved in concentrated sulfuric acid, 4 is re-oxidized by atmospheric oxygen to 5. If one assumes a relatively high contribution of the tropylium resonance structures to 5, then the initial step of the observed hydrogenation might be interpreted as a nucleophilic addition of a hydride ion at C-lob (or C-~OC).['~] Proof of the structure of 4 is based not only on the spectra (Table 1) and their analogy to those of 2, but also on an independent synthesis of this new [14]annulenequinone, which, together with the structure and electrochemical investigations on 4, will be reported upon in a separate communication." 6l Received: September 27,1990 [Z 4208 IE] German version: Angew. Chem. 103 (1991) 699 CAS Registry numbers: 4, 133228-91-8; 5, 109324-40-5; 5 . HCIO,, 133228-90-7; 6, 3526-04-3; 16-mchlorobenzoyloxy-l5-hydroxy-1,6:8,13-ethanediylidene[l4]annulene, 133228-87-2; azuleno[2,1 ,8-ijn]azulene-3.5-dione, 133228-88-3; azuleno[2,1,8-ija]azulene-I,S-dione, 133228-89-4; 5,10-diacetoxyazuleno[2,1 ,8-@]azulene, 133228-92-9. [I] 0. Bayer, Methoden Org. Chem. Houben-Weyl(4rh Ed.) Vol. 7/3c, 1979; S. Patai (Ed.): The Chemistry of [he Quinonoid Compounds, Part 112, Wiley, London 1974; S. Patai (Ed.):
1,6‐Oxido[10]Annulene solvent: 50 ml. of petroleum ether intermediate: 11‐oxatricyclo[4.4.1.0 1,6 ]undeca‐3,8‐diene intermediate: 117 g. (0.250 mole) of finely powdered 3,4,8,9‐tetrabromo‐11‐oxatricyclo[4.4.1.0 1,6 ]undecane product: 1,6‐oxido[10]annulene
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