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dc.contributor.authorTapuhi, Yitzhaken_US
dc.contributor.authorSuissa, Michal Rachelen_US
dc.contributor.authorCohen, Shmuelen_US
dc.contributor.authorBiedermann, Paul Ulrichen_US
dc.contributor.authorLevy, Amaliaen_US
dc.contributor.authorAgranat, Israelen_US
dc.date.accessioned2016-02-24T09:05:19Z
dc.date.available2016-02-24T09:05:19Z
dc.date.issued2000-01-14en_US
dc.identifier.citationTapuhi, Y., Suissa, M. R., Cohen, S., Biedermann, P. U., Levy, A., & Agranat, I. (2000). The stereochemistry of overcrowded homomerous bistricyclic aromatic enes with alkylidene bridges. Journal of the Chemical Society, Perkin Transactions 2, (1), 93-100.en_US
dc.identifier.issn1472-779Xen_US
dc.identifier.otherFRIDAID 1304527en_US
dc.identifier.urihttp://hdl.handle.net/10642/3046
dc.description.abstractThe objective of the research was to study the e ff ects of alkylidene bridges on the conformations and the conformational behaviour of overcrowded homomerous bistricyclic aromatic ethenes ( 1 ). The isopropylidene- bridged bistricyclic ethene 2 and 3 were synthesized by a reductive “dimerization” of 7 , using TiCl 4 –Zn–pyridine–THF. The methylene-bridged bistricyclic ethenes 4 – 6 were synthesized by LiAlH 4 –AlCl 3 –Et 2 O reductions of the corresponding bianthrones. The structures of 2 – 6 were established by 1 H- and 13 C-NMR spectroscopy and in the cases of 2 and 3 , also by X-ray analysis. Compounds 2 and 3 adopted C i - anti -folded conformations with 53.0 and 28.8 folding dihedrals between pairs of benzene rings of tricyclic moieties. The central C 9 C 9 bond in 2 was essentially planar. A short C 9 C 10 distance of 2.81 Å in 2 indicated an intramolecular overcrowding e ff ect in the highly folded bistricyclic ethene. Semiempirical PM3 and AM1 calculations of the anti -folded, syn -folded, twisted and orthogonally twisted conformations of 2 and 4 indicated that anti -folded 2 and 4 were the most stable conformations with folding dihedrals of 48.7 and 45.0 , respectively at AM1. A DNMR spectroscopic study of E , Z -isomerizations and conformational inversions gave ∆ G c ‡ ( E Z ) = 99.6 kJ mol 1 (CDBr 3 ) and ∆ G c # (inversion) = 97.9 kJ mol 1 (hexachlorobutadiene) in 5 and ∆ G c ‡ (inversion) > 108 kJ mol 1 (benzophenone) in 3 . These high energy barriers were interpreted in terms of less overcrowded fjord regions in the anti -folded ground-state conformations.en_US
dc.language.isoengen_US
dc.publisherRoyal society of chemistryen_US
dc.subjecteffects of alkylidene bridgesen_US
dc.subjectconformational behaviouren_US
dc.subjectovercrowded homomerous bistricyclic aromatic ethenesen_US
dc.titleThe Stereochemistry of Overcrowded Homemerous Bistrucyclic Aromatic Enes With Alkylidene Bridgesen_US
dc.typeJournal articleen_US
dc.typePeer revieweden_US
dc.identifier.doihttp://dx.doi.org/10.1039/A906696I


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