Photochemistry of Some 1,1'-Dicycloalkenyls. The Mechanism of Sensitized Photocyclization

[摘要] The photocyclization of 1,1'-dicycloalkenyls (1,1'-dicyclohexenyl, 1,1'-dicyclopentenyl, 1,1'-dicycloheptenyl and 1,1'-dicyclooctenyl) is studied. Irradiation at liquid nitrogen temperature does not show trans double bond band in IR spectra. Even though naphthalene and pyrene fluorescence are quenched very efficiently by 1, 1'-dicycloalkenyls, no or trace amount of cyclobutenes are accompanied. When acetophenone or benzophenone is used, cyclobutene is obtained only from 1,1'-dicyclohexenyls, 1,1'-dicycloheptenyl giving some adducts. Naphthalene and pyrene sensitizes adduct formation but not cyclization. From above observations, it is concluded that photocyclization occurs from the planar s-cis triplet state rather than twisted triplet, singlet excited state or vibrationally excited ground state in sensitized photocyclization of 1,1'-dicycloalkenyls.

[学科分类] 化学（综合）