Donor‐acceptor pyran‐2‐ones: Absorption and fluorescence spectra of 4‐substituted 2H‐1‐benzo/napthopyran‐2‐ones

The absorption spectra and emission spectra of 4‐substituted 2H‐1‐benzo/napthopyran‐2‐ones 3a‐1 have been determined in THF and DMSO. The substituent at the 4‐position of the 2H‐benzo/napthopyran‐2‐one, establishes a compact conjugation pathway in which the pyran‐2‐one nucleus can act as an acceptor ring.