The non-benzenoid aromatic system azulene is sufficiently nucleophilic at C1 that it can react with a protonated aldehyde to form an α-azulenyl alcohol. This in turn may be protonated and undergo loss of water to give an azulene α-carbocation. We report the isolation of such azulenyl cations as salts with non-coordinating anions. The salts have been characterised by NMR, UV/Vis absorption and (in certain cases) X-ray crystallography. Reduction of representative salts to afford azulenyl(aryl) methylenes has been demonstrated.

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http://dx.doi.org/10.1039/d2ob01695hDOI Listing

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