Ethylene glycol mediated, catalyst-free synthesis of Bis-pyrazolopyridine and their photophysical studies

Abstract: We describe a new hetero-annulation procedure for the selective synthesis of Bis-pyrazolo fused pyridines using pyrazole-5-amines and aryl glyoxal monohydrate. This distinct hetero-annulation, carried out under catalyst-free conditions with ethylene glycol as the medium, illustrates a domino reaction that involves the formation of two C-C bonds and one C-N bond. The photophysical properties of the synthesized derivatives were briefly analyzed. The emission spectra of the derivatives exhibited distinct charge transfer peaks which depend on the structure of the derivative. We evaluated the green metric calculation for our protocol to quantify the waste, reaction efficiency, and sustainability.