Oxidative Desulfurization of Electron-Donating 5,5,7,7-Tetraaryl-5,7-dihydrodibenzo[c,e]thiepins and the Related Heterocycles: Generation of Dicationic Dyes upon Two-Electron Oxidation
Upon oxidation of the title heterocycle (1A) with dimethylamino groups, elemental sulfur is extruded to form dicationic dye (1B2+), from which the starting dibenzothiepin derivative was generated by the reaction with Na2S. The bay-region substituents enhance configurational stability, so that, the optically pure heterocycles [(M)-2A, (M)-3A)] can be obtained in terms of helicity of one-handedness by starting with the corresponding optically pure dicationic dyes [(R)-2B2+, (R)-3B2+)]. Similar oxidative desulfurization occurs in dibenzo-1,5-oxathiocin 4A, a structurally related 8-membered heterocycle.