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'Valence Tautomerism' in keywords
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1996 (1)
1990 (1)
1Author    M. Arianne Bäudler, JosefH. AhnRequires cookie*
 Title    Beiträge zur Chemie des Phosphors, 208 [1] Zur Valenztautomerie des Heptaphosphanortricyclen-Anions P73- On the Valence Tautomerism o f the Heptaphosphanortricyclene Anion P73  
 Abstract    The valence tautomerism o f the heptaphosphanortricyclene anion P73~ has been studied by means o f a two-dimensional 3IP N M R exchange spectrum. The rearrangement process o f the P atoms postulated earlier [2] has been confirmed in all details. 
  Reference    Z. Naturforsch. 45b, 1279—1281 (1990); eingegangen am 6. April 1990 
  Published    1990 
  Keywords    Heptaphosphanortricyclene A nion, Valence Tautomerism, Valence Isomerization, Two-dimensional 31P Exchange Spectrum 
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 TEI-XML for    default:Reihe_B/45/ZNB-1990-45b-1279.pdf 
 Identifier    ZNB-1990-45b-1279 
 Volume    45 
2Author    Jörg Laue, G. Unther Seitz, H. Ans, W. AßmuthRequires cookie*
 Title    Synthese und [4+2  
 Abstract    ]-Cycloadditionen von 4a, 8a-Methanophthalazin, das erste Propellan mit einem elektronenreichen und einem elektronenarmen 47r-Diensystem Synthesis and [4+2] C ycloaddition Reactions o f 4a, 8a-M ethanophthalazine, the First Propellane w ith an E lectronrich and an Electrondeficient 47r-Diene System Cyclopropabenzene 3 reacts with 3,6-bis(trifluoro)-l,2,4,5-tetrazine 4 to afford in high yield the 4a,8a-methanophthalazine 6, the first propellane, containing an electron rich cyclohexadiene system on the one hand and an electron deficient diazadiene system on the other hand. According to the principle of Diels-Alder reactions with inverse electron demand, electron rich dienophiles like ketene acetals, enamines or dimethyl hydrazones react predominantly with the diazadiene system to yield the azo-bridged cycoadducts of type 19 and/or the tricyclic tetrahydropyridazines like 20. In the same fashion several more or less angle strained cycloalkenes cycloadd to the diazadiene of the propellane 6 to give the novel polycyclic azo compounds 34, 36, 38,40, 42 and 44 with exo-configuration of the annulated cycloalkanes. Attack apparently occurs from less hindered face anti to the methano bridge of 6 with high stereo-and site-selectivity. As anticipated the electron deficient dienophiles 1,2,4-triazoline-3,5-dione 45 and the benzoquinone 46 add with different site selectiviy to 6 furnishing the polycyclic pyridazines 47 and 48 resp. again by exclusive anti attack. Treatment of 6 with both an electron rich and an electron deficient dienophile like 49 and 45 resp. affords the heptacyclic anti-anti-bis adduct 51 with analogously high site-and stereoselectivity. 
  Reference    Z. Naturforsch. 51b, 348—358 (1996); eingegangen am 31. August 1995 
  Published    1996 
  Keywords    Diels-Alder Reactions, Valence Tautomerism, Propellane, Bivalent, 7r-Facial Selectivity, Site Selectivity 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0348.pdf 
 Identifier    ZNB-1996-51b-0348 
 Volume    51