1,8-Bis(dimethylamino)4,5-dihydroxynaphthalene, a Natural, Intramolecularly Protonated “Proton Sponge” with Zwitterionic Structure


  • New “Proton Sponges”, Part 12. Part 11: H. A. Staab, M. Diehm, C. Krieger, Tetrahedron Lett.1996, 36, 2967-2970.


original image

Not the expected structure 1, but the zweitterionic isomer 2 is found in crystals and solutions of the title compound. Molecules of 2 in the crystal form a type of belt, in which the positive part of the wzeitterion faces the negative part of its neighbor. This belt is coordinated to a corresponding second belt, in which the zwitterions are oriented in the opposite direction. This very interesting crystal packing prompts further studies of anisotropic crystal properties.