Chiroptical Properties of 10,11-Dihydro-5,10-methano-5H-dibenzocycloheptene Derivatives

Article abstract of DOI:10.1246/bcsj.54.2790

The title compounds have been prepared from (+)-(9R,10R)-dimethyl 11-oxo-9,10-dihydro-9,10-ethanoanthracene-1,5-dicarboxylate.Their absolute configurations were determined by chemical reaction, and by IR and CD spectra.Although the CD spectra of 2 and 3 (R=NH2) were expected to show an antipodal pattern from analysis of the simple coupling mechanism, they showed approximately the same magnitude of the positive Cotton effect in both regions of the ¹L_b and ¹L_a benzenoid transitions.Their CD spectra were calculated by the point-dipole exciton treatment and by the ?-SCF approximation using the dipole velocity procedure with and without the charge transfer transition between the aromatic chromophores.Thus, the electric transition dipole moment should not be treated as a point dipole at any place and the rotational strength should be calculated by the dipole velocity procedure since a local magnetic transition dipole moment was produced perpendicular to the benzene ring in the region of the ¹L_b transition.The charge transfer transition can not be neglected in the calculation of the MO, though it does not cause the alteration of the sequence of the coupling mode.