Tetracyclo octene

Erwahnt sei femer die photochemische Isomerisierung des exo-Tricyclo-[3,2,l,08 4]octen-Derivates 48 zum Tetracyclo[3,3,0,02 8,04>8]octan-Deri-vat 49 (216), obwohl diese Reaktionen im strengen Sinne keine Cyclo-merisation darstellt. Auf analoge Weise ist auch das unsubstituierte Tetracyclo-octan sowohl aus exo- als auch aus endo-Tricyclo [3,2,1,02.4]-octen-(6) zuganglich (125). 

Sasse, W. H. F., P. J. Collin, and G. Sugowdz The photo-addition of tolan to some naphthalenes. The formation of derivatives of 2.3-benzo-tetracyclo[3.2.1.05-7.08-8]octene-(2). Tetrahedron Letters 1965, 3373. 

Sehr gute Uberlappungsvoraussetzungen bietet exo-Tricyclo[3.2.1.0s 4]octen-(6) (I It =H). In Ather wird bei Bestrahlung (450 W Hanovia Quecksilber-Mitteldruek-Lampe) Tetracyclo [3.3.0.02-s.0i>e]octan (II R ==H) mit 29%iger Ausbeute gebildet7 ... 

Einen hochst eigenartigen Verlauf nimmt die Photocycloadditionsreaktion zwisohen Diphenyl-acetylen und Naphthalin bzw. substituierten Naphthalinen2 3. Im Ealle des Naphthalins entsteht das Addukt 4,5-Diphenyl-(benzo-tetracyclo[3.3.0.02[Pg.501]

Aus der Mutterlauge laBt sioh naeh Entfernung dos Losungsmittels durch Chromatographic an Kieselge] mit Benzin/Benzol (9 1) neben weiteren 4,0 g Produkt das isomere 7-Methoxy-4/)-diphenyl-(ben,zo-tetracyclo[3.3.0.0i l.0l >]octen- 7)) [0,37 g F 136-137° (Methanol)] gewinnen. 

Cyclooctatetraene (COT), a An non-aromatic hydrocarbon, is only one of the many (CH)s compounds, but it is a central character. The other isomers, many of which interconvert with COT by thermal and photochemical pathways, include bicyclo[4.2.0]octa-2,3,7-triene (BOT), semibullvalene (SB), barrelene (B), tricyclo[3.3.0.0 ]octa-3,7-diene (TOD), the cyclobutadiene dimers (CBD), tetracyclo[4.2.0.0. " 0 ]oct-7-ene (TOE), cubane (C), tetracyclo[4.2.0.0. 0 ] octene - the intramolecular Diels-Alder isomer of BOT (IDA), tetracy-... 

The most reasonable mechanism consistent with the facts is electrocyclization to BOX followed by an intramolecular, reversible 4 + 2 cycloaddition to give tetracyclo[4.2.0.0 0 ]octene. The carbon sequence resulting from this pathway satisfies the observations if the 1,2-isomer preferentially forms the tetracycle with methyls on the two saturated carbons. Much clearer is the result with the 1,5-isomer which can only lead to reformation of the 1,5-isomer or formation of the 1,4-isomer by the pathway described above (Scheme 9.14). 

The chemistry of cyclo-octatetraene has been reviewed. Calculations using the MIN DO method suggest that the isomerization of cyclo-octatetraenes may proceed via tetracyclo[4,2,0,0 ,0 ]octene (510) at high temperatures. The interconversion of (510) and bicyclo[4,2,0]octatriene is symmetry allowed and (510) is claimed... 

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