| Abstract: | In this work, four kinds of natural seashells (clam shell, oyster shell, scallop shell, and conch shell) are investigated as catalysts for the Knoevenagel reaction to produce arylmethylenemalonitriles, among which conch shells show the highest catalytic activity due to their mixed phases of calcite and aragonite, resulting in the relatively weak base strength and fewer number of basic sites. Solvent effect and catalyst usage are systematically investigated, and conch shells show high universality for nine aromatic aldehydes to produce the desired products with high yield in short time under optimized conditions. In addition, this catalyst possesses good recyclability and could be used four times without obvious deactivation. In all, conch shell is an efficient, low‐cost, green, and recyclable catalyst for the Knoevenagel reaction. |
