skip to main content
Original Article

Natural base catalysis in the sustainable synthesis of functionalized 2-amino-4H-chromenes




Functionalized 2-amino-4H-chromenes have been successfully synthesized via cyclization of C-H activated acids, aromatic aldehydes, and active methylene compounds using a natural base catalyst derived from waste snail shells (Bellamya bengalensis) in the water at ambient temperature. Freshwater snail shells are significant biological materials with diverse uses. As an economical and environmentally benign alternative to traditional stoichiometric reagents and expensive metal catalysts, the waste shells of snails worked well as a heterogeneous base catalyst in hetero-cyclization. The as-prepared catalyst was analyzed using FTIR, XRD, EDS, SEM, TEM, and TGA tools. The chemical analysis revealed the predominance of CaO, which in the water possibly provides an alkaline medium to the reaction through which the reaction accelerates efficiently and offers a quantitative yield of the desired product. Catalytic reusability showed slight leaching of the catalyst that could be recovered and reused.




·         Waste shells of snail-derived catalyst employed in synthesizing densely functionalized 2-amino-4H-chromenes.

·         Utilization of natural feedstock in catalysis leads to cost-efficient and sustainable methodology.

·         Characterization tools exhibited a higher concentration of Ca species in snail shells.

·         CaO-enriched catalyst possibly responsible for promoting heterocyclization more efficiently in an aqueous medium.

·         Green credentials of the protocol are enhanced using water as a solvent, ambient temperature conditions, and achieving high yields.


Graphical Abstract