Synthesis of Bicyclic Dioxetanes Bearing a Hydroxyphenanthrene or Hydroxy[4]helicene Moiety and Their Base-Induced Chemiluminescent Decomposition

Six bicyclic dioxetanes bearing a 1-hydroxyphenanthren-3-yl 2-iv, 3-hydroxyphenanthren-1-yl 2-ov, 4-hydroxyphenanthren-2-yl 2-oh, 2-hydroxyphenanthren-4-yl 2-ih, 4-hydroxy[4]helicen-2-yl 3-iv and 2-hydroxy[4]helicen-4-yl group 3-ov were synthesized and their base-induced chemiluminescent decomposition was investigated in a TBAF (tetrabutylammonium fluoride) / MeCN system. For dioxetanes in the iv-series 2-iv and 3-iv including alpha-naphthol-analog 17a and those in the ov-series 2-ov and 3-ov including beta-naphthol-analog 17b, we investigated how the chemiluminescence properties changed with an increase in the number of fused benzene rings of a hydroxyarene moiety attached to a dioxetane ring. The results showed that a) maximum wavelength of chemiluminescence lambda(CL)(max) tended to shift to a longer wavelength region as the number of fused benzene rings increased, b) the k(CTID) values for the iv-series were >1000 times larger than those for the ov-series regardless of the number of fused benzene rings, and c) a dioxetane in the iv-series tended to have a higher singlet-chemiexcitation efficiency Phi(S) than the corresponding dioxetane in the ov-series. This tendency could be explained by the "syn/anti" rotational isomerism of an aromatic electron donor, where an anti-rotamer gives Phi(S) far more effectively than a syn-rotamer.