Mild and efficient flavin-catalyzed H2O2 oxidations

Based on a previously discovered method for amine oxidations using flavins as catalysts and hydrogen peroxide as oxidant, a comparative kinetic study using NMR spectroscopy was undertaken with a series of flavins for amine an d thioether oxidations. Included in this series is the newly prepared 7,8-d ifluoro-1,3dimethyl-5-ethyl-5,10-dihydroalIoxazine. This study shows that f lavins, which bear electron-donating groups on the aromatic ring and/or the N-10 position, are less active and are deactivated during the course of th e reaction, Moreover, flavins that are alkylated at the N-1 position instea d of the N-10 position and having either no substituents or electron-withdr awing groups on the aromatic ring, remain the most active and stable.