Photochemische Umwandlungen, 42 [1] Photoisomerisierungen im 5-Isopropyliden-tetracyclo-[4.3.0.02,4.03,7]non-8-en-System. Vorläufige mitteilung

Direct photochemical excitation of the tetracyclo4.3.0.0.^2,4.0^3,7]non-8-enes 7a – d leads to a mixture of the isomers 8a – d and 10a – d , with the former being the main products. On sensitization by acetone the formation of 10a – d is clearly favored. The cis-bishomobenzenes 9a – d are the postulated intermediates. Spectral data and some thermal reactions are described.