Azulenium fluoroborates

Hafner et al. have described the preparation and use in synthesis of azulenium fluoroborates. Thus when 4,6,8-trimethylazulene (1) in ether solution is treated with an ethereal solution of fluoroboric acid, the violet color fades and colorless 4,6,8-trimethylazulenium fluoroborate (2) separates. On addition of benzaldehyde, the... 

Azulenium salts. Ethereal fluoroboric acid added dropwise with stirring and ice-cooling under anhydrous conditions to a soln. of 4,6,8-trimethylazulene in abs. ether, benzaldehyde added to the resulting 4,6,8-trimethylazulenium fluoro-borate, and the product isolated after ca. 4 hrs. l-benzylidene-4,6,8-trimethyl-azulenium fluoroborate. Y 94%.— Azulenes can be converted into azulenium salts, which are derivatives of the tropenium cation, as well as into azuleniate salts, which are derivatives of ihe cyclopentadienyl anion. F. e. and reactions s. K. Hafner, H. Pelster, and J. Schneider, A. 650, 62 (1961) syntheses via azuleniate salts s. A. 650, 80. 

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See also in sourсe #XX -- [ ]

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