PHOTOINDUCED ELECTRON-TRANSFER (PET) CYCLIZATION AND PHOTOOXYGENATIONOF 2,6-DIARYL-1,6-HEPTADIENES AND 2,7-DIARYL-1,7-OCTADIENES

The 2,6-diaryl-substituted 1,6-heptadienes 3a-c and the 2,7-diaryl-sub stituted 1,7-octadienes 4a-b were cleanly converted into the correspon ding anellated cyclobutanes 5 and 6, resp., when irradiated under phot oelectron-transfer conditions (9,10-dicyanoanthracene in acetonitrile) . Only for 4c did the rearranged compound 7c become the dominant photo product. Oxygen trapping experiments with formation of endoperoxides 8 , 9 were successful in the case of the electron-rich substrates 3b, c and 4c.