Hydride abstraction in positive-ion electrospray interface: oxidation of 1,4-dihydropyridines in electrospray ionization mass spectrometry.

During the positive-ion mode electrospray ionization mass spectrometry analysis of 1,4-diphenyl-3-benzoyl-1,4-dihydropyridines with methanol as the solvent, the major ion generated is one mass unit lower than the analyte, which can be rationalized as the oxidative aromatization of 1,4-dihydropyridines to pyridine cations.