method for the synthesis of 1- and 2-pyridylazulenes, and of 1,3-dipyridylazulenes, is described. Color and spectral changes of these pyridylazulenes upon the addition of either acid or metal ions were investigated in detail. The color changed from blue to red upon the addition of trifluoroacetic acid or soft metal ions, depending on the substitution patterns of the pyridyl group on the azulene skeleton
A Convenient Synthesis of Functionalized Azulenes via Negishi Cross-Coupling
作者:Aleksei Bredihhin、Julia Dubovik
DOI:10.1055/s-0034-1379486
日期:——
into positions 1 and 3 of azulene through cross-coupling reaction is described for the first time. A mild and effective method for the synthesis of functionalized azulenes is described. Negishi cross-coupling of bromoazulenes with functionalized aromatic, heterocyclic, benzylic, and alkylic organozinc reagents affords substituted azulenes in good yields. Functional groups, including ethoxycarbonyl,
showed a return peak associated with the oxidation, which was not observed for azulene. The stabilization of the single-electron oxidant may be due to the SOMO-HOMO energy inversionphenomenon. X-ray crystallography of the azulene dimers revealed that this species possessed a syn-type structure in which both aryl groups in the 2-positions formed π-stacks. The twisted structure was indicated to be in the