NAPHTHOQUINONE COLORING MATTERS .3. SYNTHESIS AND ELECTRONIC ABSORPTION-SPECTRA OF 1,4-NAPHTHOQUINONES CONTAINING ELECTRON-DONOR GROUPS IN BOTH RINGS

The syntheses of several 1,4-naphthoquinones containing mesomeric electron donor groups (NH2, NHR, or OMe) in both rings are described. The most convenient routes involve nucleophilic replacement of labile 2- or 3-substituents (Cl, OMe, CN) in appropriately substituted 5-donor- or 5,8-bis(donor)-1,4-naphthoquinones. The directing effects of 5-amino- and 5-nitro-groups in these reactions have been examined. The electronic absorption spectra of the derivatives show a broad, complex band system in the 350-600 nm region, and PPP-MO calculations indicate that this results from two overlapping π→π• transitions, one involving electron density migration from the benzenoid donor-group(s) into the quinonoid system, and the other involving a similar transfer of negative charge from the quinonoid donor group(s).