Diademan und Strukturverwandte, I. Darstellung und charakteristische Reaktionen einiger Tris‐σ‐homobenzol‐Kohlenwasserstoffe

Abstract

Diademan (5) und 1,6-Homodiademan (6), die ersten Kohlenwasserstoffe mit cis-Tris-o-homobenzol-Geriist, wurden durch Photoisomerisierung der monoolefinischen Vorstufen 8 (,,Snouten") bzw. 15 (,,4, gewonnen. Analog entstand aus 17 (,,endo,exo-Bishomobarrelen") das iiberbriickte trans-Tris-o-homobenzol7, das sich bequemer auch durch Rhodium(1)-katalysierte Isomerisierung von 17 oder thermische Umlagerung von exo,exo-Bishomobarrelen 18 erhalten lien. Das nicht iiberbriickte 4 wurde nach einer neuen Synthesesequenz aus 1,3-Cyclohexadien dargestellt. Thermisch lagern sich 5 und 6 sehr leicht in Triquinacen (9) bzw. Diademane and Structurally Related Compounds, I Preparation and Characteristic Reactions of Some Tris-whomobenzene HydrocarbonsDiademane (5) and 1,6-Homodiademane (6) are the first hydrocarbons with cis-tris-o-homobenzene skeletons. They were prepared by photoisomerization of the olefinic precursors 8 (,,snoutene") and 15 (,,4,5-homosnoutene"), respectively. In an analogous reaction the bridged trans-tris-o-homobenzene 7 was formed from 17 (,,endo,exo-bishomobarrelene"). 7 is more easily obtained from 17 by rhodium(1)-catalyzed isomerization or from exo,exo-bishomobarrelene 18 by thermal rearrangement. The unbridged 4 was prepared using a newly developed synthetic sequence starting from 1.3-cyclohexadiene. The thermal rearrangement of 5 and 6 to triquinacene (9) and 1,lO-homotriquinacene (16) is very facile; the gas phase kinetic parameters (Ink (5) = 33.7 -31600lRTand Ink (6) = 32.2 -28300/RT, both first order) strongly corroborate, that these rearrangements are concerted [,2, + .2, + ,2,] cycloreversions. [3,6-12C2]-labelled 4 upon thermolysis yields a truns-bicyclo[4.3.O]nona-3,7-diene (31 P 22) with a 12C-labelling pattern, which proves its formation via a 3-step mechanism. The first step in this sequence most probably

Unsaturated Oligoquinanes and Related Systems

“…5) [47]. In this context it is interesting to note that the most highly symmetrical valence tautomer of triquinacene 10, the (CH) 10 hydrocarbon 51 has also been prepared, and shown to readily rearrange to triquinacene 10 [48,49]. The suggestion that the double bonds in triquinacene 10 are similarly homoconjugated through space like those in 50, and that 10 with its 6p-system therefore should be homoaromatic, has provoked a vigorous discussion going on for over ten years [45,50,51].…”

Palladium‐Catalyzed Cyclopropanation of Unsaturated Endoperoxides. A New Peroxide‐Preserving Reaction

“…This result is also in line with a report by de Meijere et al that the cyclopropanation of bicyclo[3.2.2]nona-2,6,8-triene, the carbocyclic analog of 16, by the Furukawa method (Et 2 Zn/CH 2 I 2 ) likewise gave exclusively the exo -product stemming from carbene addition from the face distal to the propeno bridge. [23] …”

Electronic Interactions of Cyclopropyl Groups: Synthesis and Photoelectron Spectra of Model Compounds Derived from Triasterane, Nortricyclane and Norbornane

“…The fraction boiling at 63°C120 torr was pure according to its analytical gas chromatogram (GC 402, 50-m glass capillary WG II, 90°C, retention time 3.6 min), yield 41. (17) To a magnetically stirred solution of 6.9 g (0.04 mol) mchloroperbenzoic acid in 80 ml dichloromethane, containing 3 g finely powdered potassium hydrogen carbonate, 5.0 g (0.033 mol) 16 was added dropwise within 30 min at 0 "C, The mixture was stirred for 2 h at 0 •C, then warmed to room Israel Journal ofChemistry 29 1989 temperature, and again stirred for 2 h. After filtration the solution was washed with two 70-ml portions of sodium hydrogen sulfite solution, then with three portions each of saturated sodium hydrogen carbonate solution, and finally with 70 ml saturated sodium chloride solution. The organic solution was dried over magnesium sulfate, the solvent was distilled slowly through a 30-cm packed column, and the product was short-path distilled at 0.01 torr.…”

“…The organic solution was dried over magnesium sulfate, the solvent was distilled slowly through a 30-cm packed column, and the product was short-path distilled at 0.01 torr. and 50 "C. The product was pure according to its analytical gas chromatogram (GC 402, 1.5 m 10% FFAP, 120 .C), yield 4.9 g (91%) 17…”