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The bioluminescence reaction of many biological subspecies, most notably fireflies, forms dioxetanone derivatives as high-energy intermediates. The thermal instability of dioxetanones complicates understanding of the transition from the ground state to the first excited state that leads to light emission. Herein, we report the reaction mechanism of 2-coumaranones, synthetically accessible strongly chemiluminescent materials that mimic the bioluminescence reaction. The pathways of chemiexcitation and photorelaxation are clarified on the basis of synthetic evidence and spectrochemical as well as computational mechanistic analysis. [ABSTRACT FROM AUTHOR]

The mechanism of the chemiluminescent reaction of ethyl (5-fluoro-2-oxo-2,3-dihydrobenzofuran-3-yl) carbamate (a 2-coumaranone derivative) with a base and molecular oxygen was investigated. New evidence from the reaction kinetics and absorption/emission profiles was obtained, supporting the existence of a 1,2-dioxetanone as an intermediate: (i) its characteristic activation parameters (ΔH≠ = 7.2 ± 0.1 kcal mol−1; ΔS≠ = −45 ± 5 cal K−1 mol−1) indicating a high degree of thermal instability and (ii) its bimolecular decomposition rate constant for the reaction with perylene. The newly developed methodology has been shown to be suitable for determining the reactivity of such thermally unstable peroxides, which are very difficult to prepare and isolate, using this alternative approach of in situ generation of a 1,2-dioxetanone. [ABSTRACT FROM AUTHOR]

The conversion of red excitation light into blue emission light (uphill energy conversion) using unstable 1,2-dioxetanes is described. The method is based on 1,2-dioxetane formation by red-light sensitized photooxygenation of adequate alkenes and subsequent blue-light emission due to thermal 1,2-dioxetane cleavage. The energy gain resulting from the chemical energy obtained in the transformation of an alkene into two carbonyl compounds transforms a red-light excitation laser beam into a blue-light chemiluminescence emission, producing thereby a formal anti-Stokes shift of 200–250 nm, opening up a whole spectrum of possible applications. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and study of the chemiluminescence parameters and thermal stability of 1,2-dioxetanes containing a spirofenchyl substituent are reported. Three fenchyl-substituted 1,2-dioxetanes were synthesized by photooxygenation of the corresponding alkenes, obtained by Barton–Kellogg olefination of the readily available (−)-fenchone. The fenchyl-substituted 1,2-dioxetanes showed thermal stabilities similar to those of the corresponding spiroadamantyl-substituted derivatives, although being slightly more labile with respect to unimolecular decomposition than the latter derivatives, which are widely utilized as labels in a great variety of chemiluminescent immunoassays. Fluoride induced decomposition of one triggerable fenchyl 1,2-dioxetane derivative showed kinetic parameters similar to those of the corresponding adamantyl-substituted derivative. The chemiluminescence quantum yields in the one percent range are also similar to that of other widely utilized chemiluminescence systems as the luminol reaction. These results indicate that fenchyl-substituted 1,2-dioxetanes can potentially be utilized as a cheaper alternative to substitute the corresponding spiroadamantyl derivatives in bioanalytical applications. [Copyright &y& Elsevier]

The optimized one-pot synthesis of 16 new 2-coumaranones containing a carbamate side-chain is described. Furthermore, the quantum yields for the base-activated chemiluminescence in the presence of oxygen was determined for all compounds, with a maximum of 5.9 ± 0.1 x 10-2 E mol-1, and the application of these compounds as substitutes for usual bioluminescent and chemiluminescent reagents in bioassays is anticipated. A preliminary mechanistic pathway is also suggested, making use of recent developments regarding aspects of organic chemiluminescence, in agreement with both experimental and theoretical data available on the induced 1,2-dioxetanone decomposition as well as with the high efficiency of this reaction. [ABSTRACT FROM AUTHOR]

Optimized syntheses of 2-coumaranone derivatives and, based thereon, several new representatives of this class of substances are described. They show a clearly visible chemiluminescence under the exposure of a strong base and in the presence of oxygen. The wavelength and intensity of the light emitted depends on both the substituents on the benzo annealed, as well as on the type of base used. A mechanism is presented in which a delocalized enolate is postulated as a key intermediate. [ABSTRACT FROM AUTHOR]