THE MECHANISMS OF THE OXIDATION OF NADH ANALOGS .1. PHOTOCHEMICAL OXIDATION OF N-UNSUBSTITUTED 1,4-DIHYDROPYRIDINES BY VARIOUS ACCEPTORS

The reactivity of different active centers has been studied during the photo-oxidation of N-unsubstituted 1,4-dihydropyridines (1,4-DHPs) by various electron acceptors. The participation of that or another reactive center (N-H, (C-4)-H, (C-3)-CO group) in the reaction has been observed, depending on the type of process, 1,4-DHP structure, medium polarity and related properties. In the case of photo-initiated interaction with electron acceptors, the elementary mechanism of the process includes the sequential stages of electron, proton and hydrogen atom transfer (e-, H+, H.) if the electron acceptors are quinones which are able to form charge transfer complexes with the initial 1,4-DHP. When acceptors of another type are used, the primary act of the photo-oxidation process is the abstraction of hydrogen atoms from the C-4 position of the 1,4-DHP, and the oxidation takes place as the two-stage (H., H-) process.