Waste mussel shell as a highly efficient heterogeneous catalyst for the synthesis of polyfunctionalized 4H-pyrans in aqueous media

An economical and environmentally friendly heterogeneous base catalyst has been developed from a waste freshwater mussel shell and employed successfully for the synthesis of 4H-pyrans in an aqueous medium at ambient temperature. 2-arylidenemalononitrile, an intermediate of 4H-pyran reaction, was also prepared using the same catalyst. The catalyst was characterized by FT-IR, XRD, XRF, EDS, and SEM. Analytical tools such as XRF and EDS explored the presence of calcium oxide as a main component in the mussel shell, while the XRD pattern showed crystalline nature and SEM image displayed porous surface with irregular cavities. The catalyst exhibited unprecedented performance in the one-pot three-component condensation reaction of C–H activated acidic compounds with aromatic aldehydes and malononitrile in the green reaction medium and offered pure products without chromatographic separation.