| Abstract: | The geometries of a fourfold bridged tricyclo4.2.0.02,5]octa-3,7-diene ( 1 ) and its photoproducts 2 and 3 were calculated by Hartree-Fock ab initio (3-21G and DZP basis) and semiempirical (MNDO, AM1, MINDO /3) methods. It was found that due to the smaller distance between the double bonds in 1 (2.65 Å) as compared to the parent tricyclo4.2.0.02,5]octa-3,7-diene ( 4 ) (2.91 Å), the sequence of the frontier orbitals is different. In the case of 1 , the photochemical 2 + 2]cycloaddition is allowed, whereas in 4 it is forbidden. © 1995 by John Wiley & Sons, Inc. |
