The Reaction of Biadamantylidene with Singlet Oxygen in the Presence of Dyes [1]

Abstract

SummarySinglet oxygen, generated chemically or photogenetically, reacts with biadamantylidene to give the corresponding dioxetane and epoxide only. When methylene blue (MB) or meso-tetraphenylporphin (m-TPP) is used as sensitizer the normal reaction course occurs giving dioxetane as the preponderant product in 2-propanol, ethyl acetate, acetone, pinacolone, methylene chloride, chloroform, carbon tetrachloride and benzene, although in the last two solvents some 10-25% of epoxide is formed. When erythrosin and rose bengal (RB) are used, epoxide becomes the main product (70-95%). Epoxide does not derive from chemical reaction with the solvent. Pinacolone, for example, is not oxidized to t-butyl acetate.The rose bengal reaction involves both singlet oxygen and radicals, since diazabicyclooctane (DABCO) and di-t-butyl-p-cresol interfere with the oxidation. A mechanistic scheme is proposed in which sensitizer and oxygen combine to produce sensitizer radical cation and superoxide radical anion. Subsequently, hydroperoxy radical, deriving from superoxide, reacts with substrate to give epoxide and hydroxy radical. The latter adds to substrate to give a new radical which captures triplet oxygen. Epoxide is formed by loss of hydroperoxy .radical and the chain starts anew. The dioxetane is formed separately either by [2 + 21-cycloaddition or stepwise addition.

Determination of the Quantum Yield of Intersystem Crossing of Rose Bengal

“…Since deconvolution of the observed bleaching signal yields curves corresponding to those obtained for transient absorption, we used Eqn. 23 in order to fit the formation of the radical cation and calculate its maximum concentration.…”

Precocene II Metabolism in Insects: Synthesis of Potential Metabolites and Identification of Initial in Vitro Biotransformation Products

“…Because of the problems encountered in repeating the previously reported synthesis and the potential significance of the epoxide 15 as a key intermediate in both bioacti- vation and detoxification, the successful preparation and characterization of this compound became an important synthetic goal. Since MCPBA oxidation proved unsuccessful, several other routes to the epoxide were examined, including oxidation of 1 with H202, using either acetonitrile (Payne et al, 1961) or p-chlorophenyl isocyanate (Matsumura et al, 1970) as the coreactant, photooxidation sensitized with -diketones (Shimizu and Bartlett, 1976) or with rose bengal (Jefford and Boschung, 1977), and formation of the bromohydrin, followed by dehydrobromination with base. None of these techniques gave the epoxide, but evidence for the existence and thermal stability of this compound was obtained in the GC-MS analysis of chromatographically pure cis-diol (12), which showed a second component having chromatographic and mass spectral properties consistent with the epoxide structure.…”

Glutathione depletion associated with rose bengal‐photosensitized mortality in the housefly, Musca domestica

“…Molecular mechanisms of photosensitization have been extensively reviewed [2,3]. Xanthene dyes are believed to generate singlet oxygen [4] and also to be capable of free radical-type reactions [5]. Although the literature abounds with toxicological [6] and photochemical [7-91 investigations, relatively few studies have been performed on intact organisms to determine the mechanism of photodynamic action.…”