Secododecahedradienes - Syntheses, Reactivity, in-Plane Homoconjugated 3C/2e Cations, 4C/3e Radical Cations, andσ-Bishomoaromatic 4C/2e Dications?

Abstract

Edgar Heilbronner in alter Verbundenheit (H. P.; H.-D. M.) zum 80. Geburtstag Secodecahedradiene 2a, featuring very proximate, perfectly syn-periplanar and significantly pyramidalized CC bonds, was synthesized as testing object for in-plane(s)-homoconjugational electron delocalization, starting from the available pagodane 15b. The response of 2a (and in part its diester 2b) ± in p,p-distance (average 3.08 ), olefinic pyramidalization (average 26.98), and p,p-split (PE, 1.15 eV) intermediate between disecododecahedradiene 1a and 1,16-dodecahedradiene 3a ± to selected 4p-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 s-bishomoaromatic 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 s-homoconjugated cations.

Carbocations in Superacid Systems

“…Dication 585 can be considered as a four-p-electron bicyclo(polycyclo)aromatic system. For 596, only the corresponding bisallylic dication could be observed, 1051,1052 whereas for 597 the dication could not be observed at all. The extent of bishomoaromatic delocalization, as expected, is critically dependent upon structural geometry.…”

CIDNP as a tool for rapid rearrangements: New insights into cyclobutanoid 4‐center/3‐electron radical cations

“…The discovery of the highly persistent (2 days at 20 °C) 4‐center‐3‐electron (4c/3e) radical cation observed upon (electro)chemical oxidation of [1.1.1.1]pagodane ( 1 ) has induced numerous studies of related cage skeletons . Significant changes with respect to stability, persistence and behavior of the corresponding radical cations could be established.…”