Silica Bonded Bis(Hydrogensulphato)Benzene as a New, Sustainable Catalytic Material for an Efficient and Aqueous Based Synthesis of 5-Oxo-4H-Pyrano[3,2-c]Quinolone Scaffolds

Abstract

Catalytic use of benzene-1,3-disulfonic acid at an ordinary condition gets restricted due to its high hygroscopic and moisture sensitive nature. In the present study, a new catalytic material silica bonded bis(hydrogensulphato)benzene (SiO₂-BHSB) was synthesized through a sequence of reactions, where the active catalytic part benzene-1,3-disulfonic acid was grafted on the surface of micro-sized silica by the chemical bonding. Structural features, purity, thermal stability, and acid strength of the synthesized SiO₂-BHSB material were confirmed by the adequate analytical techniques such as FT-IR, solid-state CP-MAS ¹³C-NMR, CP-MAS ²⁹Si-NMR, EDX, DTG, TGA, and volumetric studies. The synthesized material SiO₂-BHSB was observed as an efficient and sustainable reaction promoter for a tandem reaction between 4-hydroxy-1-methyl-2(1H)-quinolone, malononitrile, and structurally diverse aldehydes to offer pyrano[3,2-c]quinolone scaffolds. An environmentally benign catalytic protocol in aqueous based solvent and at ordinary energy conditions was developed, wherein a tiny amount (3 mol%) of SiO₂-BHSB was observed sufficient to catalyze the synthesis pyrano[3,2-c]quinolone scaffolds. Structures of the synthesized pyrano[3,2-c]quinolone derivatives were established from their physical and spectrometric data. Catalyst recovery and reuse study revealed that SiO₂-BHSB sustains its catalytic activity even after five runs of its reuse. Use of aqueous-based solvent, environmentally compatible reaction conditions, ease of catalyst recovery and reuse are the additional salient features of the present protocol.

Graphical Abstract

Keywords:

• 4-Hydroxy-1-methyl-2(1H)-quinolone
• 5-oxo-4H-pyrano[3;2-c]quinolone
• silica bonded bis(hydrogensulphato)benzene
• water-based solvent

Acknowledgments

One of the authors KRK is thankful to the Principal, ASC College Kolhar, and the Principal, PVP College, Pravaranagar for providing infrastructure and time to carry out this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).