Synthesis of 3-substituted imidazo[1,5-a]pyridines having 1-(N-picolinamidin-2-yl) group

The 3-substituted imidazo[1,5-a]pyridine compounds having 1-(N-picolinamidin-2-yl) group (1a–h) were synthesized by heating 1 equiv of an aldehyde (eight examples), 2 equiv of 2-cyanopyridine and ammonium acetate in PEG-400. By heating 2 equiv of the aldehyde and 1 equiv of 2-cyanopyridine under the same experimental conditions, 2,4,5-trisubstituted imidazoles (2a–c) were isolated. All the reported compounds were thoroughly characterized and the molecular structures of 1a and 2b were established by single crystal X-ray diffraction studies.