1999
DOI: 10.1039/a901202h
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Long-lived [1.1.1.1]- and [2.2.1.1]-‘Isopagodane’ dications: novel 4C/2e σ-bishomoaromatic dications†

Abstract: The [1.1.1.1]pagodane (A, m = n = 1) and functionalized derivatives have received considerable attention as intermediates in the various synthetic routes to pentagonal dodecahedranes. 1 An important theoretical aspect is linked to the central, planar, peralkylated cyclobutane ring: Two-electron oxidations had allowed the experimental verification of shomoaromaticity in form of the respective 4C/2e dications. 2,3 In order to gain more insight into the limiting structural and energetic prerequisites of this intr… Show more

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Cited by 15 publications
(9 citation statements)
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“…[67][68][69][70] The dications 44 and 47 are fully characterized by experiment, 13 C NMR spectroscopy, and by theory as 4-center 2-electron (4c/2e) bishomoaromatic dications. 67,70 Prinzbach et al proposed that the persistent species formed upon two-electron oxidation (cyclic voltametry) of 48 or 49 is the homoaromatic 4c/2e dication 50. 69 The central 4c/2e moiety has a rectangular geometry with calculated (B3LYP/6-31G*) bond/interatomic distances ranging from a ) 2.357 to 2.419 Å and b ) 1.424 to 1.432 Å for 44 and 47.…”
Section: Pagodane Dicationsmentioning
confidence: 99%
“…[67][68][69][70] The dications 44 and 47 are fully characterized by experiment, 13 C NMR spectroscopy, and by theory as 4-center 2-electron (4c/2e) bishomoaromatic dications. 67,70 Prinzbach et al proposed that the persistent species formed upon two-electron oxidation (cyclic voltametry) of 48 or 49 is the homoaromatic 4c/2e dication 50. 69 The central 4c/2e moiety has a rectangular geometry with calculated (B3LYP/6-31G*) bond/interatomic distances ranging from a ) 2.357 to 2.419 Å and b ) 1.424 to 1.432 Å for 44 and 47.…”
Section: Pagodane Dicationsmentioning
confidence: 99%
“…Experimentally, efficient cyclic in-plane delocalization has been verified in 4C/3e radical cations and σ-bishomoaromatic 4C/2e dications A (Figure ) through one- and two-electron oxidation (superacid, PE, CV, EPR 6 ) of the polycyclic pagodanes ( C ‘) and the respective “pagodadienes” ( D ‘), with a peralkylated cyclobutane ring ( C ) and two proximate, syn -periplanar CC double bonds ( D ), respectively, as rigidly preoriented four-carbon cores. In subsequent efforts to distinguish “tight” and “extended” (4C/ 3e) precursor radical cations A and to define “scope and limitations” of this sort of in-plane electron delocalization, in 1,16-dodecahedradiene at a π,π distance of ∼3.5 Å (ω = 180°), still the 4C/3e radical cation, but not, however, the corresponding 4C/2e dication, could be detected. , The importance of “kinetic protection” is underlined by the failure to observe the dications derived from the less rigid “bird-cages” and their dienes ( C ‘ ‘, D ‘ ‘) . Of particular relevance in the context of this paper is the fact that all these substrates ( C , D ) proved not amenable to reduction to give the respective (σ-bishomoaromatic) 4C/5(6)e (di)anions ( E , F ), not even after the installation of charge-stabilizing electronegative functionalities.…”
Section: Introductionmentioning
confidence: 99%
“…102, Although the dications 85 and 86 are of σ-bishomoaromatic nature (4C/2e) and of similar geometry as 75 and 80, they are chemically different in their properties. 102 The cyclobutane dication structures in pagodane and isopagodane skeletons are fully supported by theory and are considered 4C/2e σ-bishomoaromatic dications. 103, Attempted generation of dications in secododecahedradiene skeletons were unsuccessful demonstrating the limitations of the σ-bishomoaromaticity in strained systems.…”
Section: Static Cyclopropylcarbinyl Cationsmentioning
confidence: 62%
“…Similar cyclobutane dications, 85 and 86 , have been obtained by the oxidative ionization of [1.1.1.1] and [2.2.1.1]isopagodanes, respectively. , Although the dications 85 and 86 are of σ-bishomoaromatic nature (4C/2e) and of similar geometry as 75 and 80 , they are chemically different in their properties …”
mentioning
confidence: 71%