Publication
JACS
Paper

Organic Photochemistry with 6.7-eV Photons: Photoisomerization of Tricyclo[3.2.1.02,4]oct-6-ene (Endo and Exo) and Tricyclo[3.2.2.02,4]non-6-ene (Endo and Exo)

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Abstract

Photolysis of the title compounds at 185 nm in solution leads to internal addition of the olefinic group to the cyclopropane ring and cleavage of the cyclopropane to a bicyclic 1,4-diene. A theoretical analysis of the interactions between the -orbitals of the double bond and the orbitals of the cyclopropane in each of these compounds has been carried out. The effect of through-bond interactions superimposed upon the through-space effects when extended to the valence excited states gives rise to three low-lying excited states which are (in order of decreasing energy) σA → σA* + π* (forbidden), Ns + π → π* + σA* (allowed), and π - σs → π* + σs (allowed). The internal addition reaction is identified with the π - σs → π* + σA* state and the cleavage of the cyclopropane to yield a 1,4-diene with the σs + π → π* + σA* state. The low reactivity of the endo-tricyclo[3.2.2.02,4]non-6-ene is believed to relate to a departure from the ordering of the excited states as described above. © 1980, American Chemical Society. All rights reserved.

Date

01 May 2002

Publication

JACS