Preparation and Properties of Strained Medium-ring Systems

4 Preparation and Properties of Strained Medium-ring Systems 

Direct photoisomerization of cyclo-octene gives a trans. cis ratio of 49 51, respectively, in the photostationary state, whereas photostationary trans cis ratios of 5 95 and 13 87, were observed on toluene photosensitization in the liquid and vapour phases, respectively. On irradiation, mixtures of isoprene and either cis-cyclohept- or cis-cyclo-oct-2-enone give the Diels-Alder adduct of the trans-cyclo-alkene similar Diels-Alder adducts were obtained using cyclopentadiene.  

Fischli, Q. Branca, and J. Daly, Helv. Chim. Acta, 1976, 59, 2443. 

Shinozaki, S. Arai, and M. Tada, Bull. Chem. Soc. Japan, 1976, 49, 821. 

Thermolysis of 2,3 5,6-dibenzobicyclo[5,2,0]non-8-ene at 290 °C in a flow apparatus gave a mixture of cis,cis- and cis,frans-1,2 7,8-dibenzocyclononatetraene (84) (84) is the first cis,trans-cyclononatetraene derivative to be isolated.  

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