New mesoionic systems of azolopyridine series 2. Synthesis,structures, and biological activity of 2-aminothiazolo[3,2-a]pyridinium salts and thiazolo[3,2-a]pyridinium 2-imidates

A new procedure was developed for the synthesis of 2-aminothiazolo[3,2-a]pyridinium salts 8 by the reaction of 2-halo-N-phenacylpyridinium salts with KSCN. The anion compositions of salts 8 were studied by ion chromatography. Acylation of salts 8 afforded representatives of the previously unknown bicyclic mesoionic thiazolo[3,2-a]pyridinium 2-imidate system 9. The three-dimensional structures of 2-amino-3-(p-bromobenzoyl)thiazolo[3,2-a]pyridinium thiocyanate and N-trifluoroacetyl-3-(p-nitrobenzoyl)thiazolo[3,2-a]pyridinium 2-imidate were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 226–232, January, 2005.