Synthetic and structural studies on pentafluorobenzylated imidazole systems

Quaternization of common N-functionalized imidazoles (vinyl-, allyl-, propargyl-) with pentafluorobenzyl bromide afforded the respective series of differently substituted imidazolium salts. Likewise, chemospecific S- and N-alkylation of the commercial medicinal drug methimazole (1-methyl-3H-imidazole-2-thione) and its vinylated relative 1-vinyl-3H-imidazole-2-thione yielded N,S-bis(pentafluorobenzyl)-2-mercaptoimidazole derivatives. In order to illustrate the proven feasibility of perfluorophenyl moieties to undergo further nucleophilic aromatic substitution, one member of this newly conceived family of fluorinated salts was converted to the 4-azido derivative, namely 3-(4-azido-2,3,5,6-tetrafluorobenzyl)-1-vinylimidazolium bromide. Staudinger and copper-catalyzed azide-alkyne cycloaddition reactions were performed as well in an initial investigation into azide follow-up chemistry. All target compounds, including new intermediates, were characterized by routine spectroscopy and mass spectrometry. Additionally, X-ray single crystal structure determinations were performed for 14 substances. Surfactant properties were investigated for selected representatives through surface tension measurements. Lastly, the thermal stability of the azido compound was evaluated by thermoanalysis (TGA /DSC).