Synthesis, Thermal Stability, and Chemiluminescence Properties of the Dioxetanes Derived from 1,4-Dioxines

Article abstract of DOI:10.1021/jo00195a008

Photosensitized oxygenation of benzo- and naphtho-1,4-dioxins 3 afforded the corresponding 1,2-dioxetanes 4 in moderate to good yields.Ene products 7 were obtained in those cases in which the 1,4-dioxins 3 bear alkyl substituents.Thermal decomposition of the 1,2-dioxetanes 4 afford the corresponding diesters 5 essentially quantitatively.The X-ray crystal structures of the dioxetanes 4g, 4h, and 4j indicate that the four-membered rings are all essentially planar.These dioxetanes exhibit surprisingly similar thermal stabilities; the free energies of activation (ΔG(excit.)) at 298 K fall within 26 +/- 1 kcal/mol, the enthalpies of activation (ΔH(excit.)) within 24 +/- 1.5 kcal/mol, and the entropies of activation (ΔS(excit.)) within -6 +/- 2 eu.In their chemiluminescence properties they are inefficient sources of chemienergized, electronically excited diester products.The singlet excitation yields (Φ^S) range between 0.0001percent and 0.003percent and the triplet excitation yields (Φ^T) between 0.01percent and 3.5percent.They represent typical dioxetanes in that preferentially triplet excited carbonyl products are chemienergized.