2-ARYLAZOIMIDAZOLES REVAMPED BY QUARTERNIZATION OR DIMERIZATION; ANOTHER GAIN IN FUNCTIONALITY OF AN INDUSTRIAL DYESTUFF FAMILY BY TASK-SPECIFIC SIDE-CHAIN SUBSTITUENTS

Based on [(E)-2-(4-fluorophenyl)diazenyl]-1H-imidazole,[210180-24-0], a versatile late stage intermediate for the divergent synthesis of direct dyes, a novel series of N,N`-disubstituted azoimidazolium salts was prepared. In particular, benzylation, 4-vinylbenzylation, phenacylation, sulfopropylation, ethylation, as well as propargylation allowed for the access of derivatives (1-6), which are useful for follow-up conversions, e.g. click reactions, or free radical polymerization. The compounds were routinely characterized spectroscopically. The diethylated tetrafluoroborate salt 5 was additionally analyzed by F-19-NMR. Hot stage microscopy of contact melts of 5 with the less commonly used anionic nucleophiles azide and rhodanide illustrate the rapid formation of deeply colored products confirming the nucleophilic aromatic replacement of fluoride in the 4-fluorophenyl substituent. Remarkably, in addition to the conceived functional quarternizations, a neutral dimer chromophore (7) resulted from using epichlorohydrin as a linking agent. Single crystal X-ray structure determinations are reported for all newly described compounds.