The pyridinium–dihydropyridine system. Part 2. Substituent effects on the oxidation of 1,4-dihydropyridines by flavins

Abstract

The oxidation of a series of 1,3-disubstituted 1,4-dihydropyridines by riboflavin of flavin mononucleotide has been studied in aqueous buffer at 25 °C. Substituents at the 3-position have a greater effect on the reaction rate than the same groups attached to 1-methyl. With carbamoyl at the 3-position, varying the 1-methyl substituent produces a linear relation with σ*, except for the 1-methoxymethyl compound, which reacts more slowly than expected. The reaction of uncomplexed reactants has ρ*–1.91, consistent with a hydride transfer path.