Photochemistry of Trans-Fused Bicyclo 2,4-Dienes. Ground-State Conformational Control in Rigid Systems.

Article abstract of DOI:10.1021/jo01305a001

The photochemistry of a series of simple trans-fused bicyclo<4.n.0> 2,4-dienes (n=3, 4, 5) which possess semirigid structures in the ground state has been studied. trans-Bicyclo<4.3.0>nona-2,4-diene gave rise to cis,cis,cis-cyclonona-1,3,5-triene, the first example of a nonaccordant cyclohexadiene ring opening.The trans-bicyclo<4.4.0>deca-2,4-diene at -40 deg C, using 254-nm light, yielded trans,cis,trans-cyclodeca-1,3,5-triene.This triene upon further irradiation yielded endo,endo-tricyclo<5.3.0.0^2,10>dec-8-ene.The triene was extremely thermally labile and was readily converted to cis-bicyclo<4.4.0>deca-2,4-diene.At -78 deg C, the photostationary state of trans-bicyclo<4.4.0>deca-2,4-diene showed a wavelenght dependency.The photochemistry of trans-bicyclo<5.4.0>undeca-8,10-diene was analogous to that of the ten-carbon analogue.