Carbon-SO₃H catalyzed expedient synthesis of new spiro-[indeno[1,2-b]quinoxaline-[11,2′]-thiazolidine]-4′-ones as biologically important scaffold

Abstract

In this report, we have described a convenient and eco-compatible approach for synthesis of new hybrid spiro[indeno[1,2-b]quinoxaline-[11,2′]-thiazolidine]-4′-ones (4a-k) via multi-component reaction of indeno[1,2-b]quinoxalinone, α-mercaptocarboxylic acids and various types of amines using urea-choline chloride as green deep eutectic solvent and carbon-SO₃H as a solid acid catalyst. This new protocol produces a thiazolidine ring attached to indeno[1,2-b]quinoxaline through spiro carbon in good to excellent yields. The advantages of this protocol are avoidance of toxic and harmful catalyst and solvents further both catalyst and DES were recovered from the reaction mixture quantitatively and reused several times. Synthesized compounds were characterized on the basis of spectral and single crystal X-ray analysis. The prepared catalyst was characterized by FT-IR, SEM, and X-ray diffraction method.

Graphical Abstract

Keywords:

• Indeno[1,2-b]quinoxaline
• α-mercaptocarboxylic acid;multi-component reaction
• solid acid catalysis

Acknowledgments

We are thankful to the Central Drug research institute (CDRI), Lucknow and MNIT, Jaipur for the spectral analyses and elemental analyses. We are thankful to IIT, Indore for single crystal X-ray analysis.

Additional information

Funding

R. S. thanks DST, New Delhi for start-up grant (YSS/2015/000972).