TRIPLET PHOTOCHEMISTRY OF MEDIUM RING TRIENES

Article abstract of DOI:10.1016/S0040-4020(01)92373-7

The photochemistry of the triplets of 10- and 11-membered ring 1,3,5-trienes has been studied.At -70 deg C, cis,trans,cis-cyclodeca-1,3,5-triene goes only to the cis,cis,cis-isomer.At 25 deg C, this latter compound is converted into cis-bicyclo<4.4.0>deca-2,4-diene via the thermally labile trans,cis,trans-cyclodeca-1,3,5-triene.At -70 deg C, cis,trans,cis-cycloundeca-1,3,5-triene is converted to the cis,cis,cis-isomer.At 25 deg C, this primary photochemical product undergoes a thermal 1,7-sigmatropic hydrogen migration to yield the trans,cis,cis-isomer.This latter triene upon sensitized irradiation yields cis-bicyclo<5.4.0>undeca-8,10-diene and trans-bicyclo<7.2.0>undeca-2,10-diene.The ratio of these latter two products changes with the temperature of the sensitized reaction.The possible mechanisms of these transformations are discussed.