635724-00-4Relevant articles and documents
Synthesis and Properties of α,α -Bis(heteroazulen-3-yl)-1,4-benzoquinonemethides
Naya, Shin-Ichi,Watano, Tetsuhiro,Nitta, Makoto
, p. 2035 - 2043 (2007/10/03)
The synthesis and properties of a novel type of α,α -bis(heteroazulen-3-yl)-1,4-benzoquinonemethides 11a-f are studied. The synthetic method was based on a TFA-catalyzed electrophilic aromatic substitution on the heteroazulenes with 4-hydroxybenzaldehyde to afford the corresponding methane derivatives, followed by oxidative hydrogen abstraction with DDQ, and subsequent exchange of the counter-anion by using aq. HBF 4 or aq. HBF6 and neutralization. The polarization of 11a-f was evaluated by their 13C NMR and UV-vis spectral data. The thermodynamic stability of the conjugated acid of 11a-f was evaluated to be in the order 11a a values (a values. In CV measurements, the reduction waves of quinonemethides 11a-f were reversible, suggesting a stabilizing effect of heteroazulenes toward the radical and anion species. Moreover, quinonemethides 11a-f showed two oxidation waves, and that the first oxidation potentials (EIox) of 11a-c, which have two t-Bu groups, are reversible.