Indole dioxetanes and epoxides by oxidation of N-acylated indoles with singlet oxygen and dimethyldioxirane: kinetics and chemiluminescence yields of the thermal dioxetane decomposition and fluoride ion-induced CIEEL emission

Abstract

Photooxygenation of the N-acylated indoles 2 afforded the corresponding labile indole dioxetanes 3, the allylic hydroperoxides 4 and the carbamates 5. The dioxetanes were sufficiently stable for isolation and spectral characterization. Additionally, they were characterized by their chemiluminescence properties and chemical transformations, i.e. thermolysis to the fragmentation products 5 and dimethyl sulfide deoxygenation to the epoxides 7. The latter were independently prepared by dimethyldioxirane oxidation. The activation parameters (E_a, log A, ΔH‡, ΔS‡) and the excitation yields (Φ^S, Φ^T) of the direct chemiluminescence for the indole dioxetanes 3 were determined by standard isothermal kinetic methods. The fluoride ion-induced decomposition of the silyl-substituted dioxetane 3b released intramolecular CIEEL emission.