Metal-Free, Iodine-Mediated Multicomponent Synthesis of Bis-Pyrazolo-Pyridine Derivatives

Abstract

A one-pot, iodine-mediated, metal-free protocol has been developed for the synthesis of pyrazolo-fused pyridines from pyrazole amines, phenylglyoxal monohydrate, and phenylhydrazine hydrochloride. This method uses readily available substrates, offers a broad scope, and mechanistic studies reveal the role of iodine and the formation of 3 C-N and 2 C-C bonds.Polyheterocyclic systems are significant as the heteroatoms in their structure can modify the electronic structure of the compound, its polarity, and hydrogen-bond interactions. Hence, they are instrumental as a fluorescent material and in the semiconductor industry. 1 Fused pyrazole-based heterocyclic systems are essential scaffolds in the pursuit of biological activity and are present in various drug molecules and material synthesis (Figure 1). 2 Among these, pyrazole and pyridine are helpful for their fluorescence behaviour and biological activity. 3 However, synthesis of bispyrazolo pyridine is not known in the literature.