Gluconic acid promoted cascade reactions of 2-phenylimidazo[1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione to create novel fused bisheterocycles

Abstract

Here in, we described the synthesis of novel bisheterocycles imidazopyridine bearing xanthenedione by reacting various substituted 2-phenylimidazo [1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione in gluconic acid aqueous solution (GAAS) via a tandem Knoevenagel followed by Michael, cyclization & tautomerization sequence. The use of GAAS in organic synthesis offers significant benefits like cost-effective, simple operation, reusable catalyst and green method. The reaction completed in 2–12 h to afford white stable solid compounds with very good yield. The structures of the compounds are confirmed by analyzing MS, IR, ¹H NMR and ¹³C NMR spectra. Further, the structure of compound 3 h was confirmed by XRD analysis.

GRAPHICAL ABSTRACT

KEYWORDS:

• Bisheterocyclic
• gluconic acid
• imidazopyridine
• reusable
• xanthenedione

Acknowledgments

The authors are thankful to Dr. S. J. S. Flora, Director for his support in carrying out this research work. The authors would like to acknowledge Department of Pharmaceuticals, Ministry of Chemicals and Fertilizers, Govt. of India for financial support, SAIF, CSIR-CDRI, Lucknow for the spectral analysis and Indian Institute of Technology, Kanpur for single crystal X-ray analysis.

Supporting information

Full experimental detail, ESI-MS; HRMS, ¹H and ¹³C NMR spectra of all compounds and XRD data of 3 h can be found via the “Supplementary Content” section of this article’s webpage.