Photoreactions of Hydroxychlordene in Solution, as Solids, and on the Surface of Leaves

The photoreactions of the heptachlor transformation product 1-exo-hydroxychlordene (exo-4,5,6,7,-8,8-hexachloro-3a,4,7,7a-tetrahydro-4,7-methanoinden-l-ol) (2) dissolved in organic solvents, as a solid on glass, and dispersed on plant leaf surfaces have been investigated. In addition to the (2 + 2) cycloaddition typical for this substance class, an entirely novel intramolecular photoisomerization reaction was found. This reaction leads to cyclic ketone, l,la,2,2,3,exo-6-hexachloro-la,2,3,3a,5a,5b-hexahydro-l,3-methano-lH-cyclobuta[cd]pentalen-4-one (8), whose structure was established by spectral data obtained by mass spectrometry, infrared spectrometry, and 1H and 13C nuclear magnetic resonance measurements.