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Secododecahedradienes – Syntheses, Reactivity, in‐Plane Homoconjugated 3C/2e Cations, 4C/3e Radical Cations, and σ ‐Bishomoaromatic 4C/2e Dications?
Author(s) -
Reinbold Jens,
Bertau Martin,
Voss Torsten,
Hunkler Dieter,
Knothe Lothar,
Prinzbach Horst,
Neschchadin Dmytro,
Gescheidt Georg,
Mayer Bernhard,
Martin HansDieter,
Heinze Jürgen,
Prakash G. K. Surya,
Olah George A.
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010613)84:6<1518::aid-hlca1518>3.0.co;2-r
Subject(s) - chemistry , dication , allylic rearrangement , electrophile , reactivity (psychology) , cationic polymerization , photochemistry , radical , radical ion , medicinal chemistry , crystallography , computational chemistry , molecule , organic chemistry , ion , medicine , alternative medicine , pathology , catalysis
Secodecahedradiene 2a , featuring very proximate, perfectly syn ‐periplanar and significantly pyramidalized C=C bonds, was synthesized as testing object for in‐plane( σ )‐homoconjugational electron delocalization, starting from the available pagodane 15b . The response of 2a (and in part its diester 2b ) – in π , π ‐distance (average 3.08 Å), olefinic pyramidalization (average 26.9°), and π , π ‐split (PE, 1.15 eV) intermediate between disecododecahedradiene 1a and 1,16‐dodecahedradiene 3a – to selected 4 π ‐reagents, electrophiles, and radicals was explored experimentally and by calculations. Intriguing multistep reaction sequences attest to the ease of competing stabilization pathways for the 3C/2e in‐plane homoconjugated cationic intermediates. PE, CV, and ESR measurements and calculations (DFT) characterize the radical cation generated from 2a as in‐plane homoconjugated 4C/3e‐species 2a .+ , persistent in a Freon matrix, but only very shortly existent in solution (CIDNP). Consequently, NMR control of the two‐electron oxidation in SbF 5 /SO 2 ClF did not disclose the σ ‐bis‐homoaromatic dication 4C/2e (see 2a 2 + ), but a bis‐allylic dication 75 as persistent species. In support of 2a 2 + as intermediate, evidence is presented for very limited kinetic protection offered by the secododecahedral framework to through H‐cage σ ‐homoconjugated cations.