The photolysis of 1-benzyloxy-2-pyridone and its methyl derivatives. Correlation with 1H NMR-derived ground-state conformation

Abstract

In addition to methyl substituent effects on the reactivities of the vibrationally unrelaxed excited singlet statt of 1-benzyloxy-2-pyridone (1), deuterium isotope effects on the reaction efficiencies of (1) and its methyl derivatives are discussed on the basis of their major ground-state conformations, as analysed by ¹H NMR spectroscopy. It is suggested that intramolecular hydrogen abstraction of the benzylic hydrogen by the amido carbonyl oxygen in (1) competes with N–O bond cleavage in polar solvents. Effects exerted by both a methyl group and a non-polar solvent are manifested by the predominant N–O bond cleavage in the vibrationally ‘hot’ excited singlet state.