Electron paramagnetic resonance spectroscopic studies of the electron transfer reaction of Hantzsch ester and a pyrylium salt.

The oxidation of Hantzsch ester by a pyrylium cation takes place via electron-proton-electron transfer. The reaction was investigated with EPR spectroscopy using TEMPO and DMPO for inhibition and spin trapping, respectively, of the radicals appearing during the reaction. The present in-depth EPR study of the radical reactions of a NADH analogue indicate a complex electron transfer mechanism in the title reaction.