Naphthopyrones, Part I Proton magnetic resonance spectral studies of some methylnaphthopyran-2-one and methylnaphthopyran-4-one derivatives

摘要

The 220 MHz1H-NMR spectra of four methylnaphthopyrone derivatives are presented and discussed. The chemical shift changes which occur upon protonation in trifluoroacetic acid solution are much more significant for the benzochromones than for the benzocoumarins. The particularly large effects at the methyl (0.6 ppm) and at the residual pyrone ring proton (1.2 ppm) provide a useful technique for differentiation between the two series of compounds.