Recyclable CMK-5 supported sulfonic acid as an environmentally benign catalyst for solvent-free one-pot construction of coumarin through Pechmann condensation

• Efficient synthesis of coumarins with green and simple experimental procedure.
• Solvent-free reaction conditions.
• Exceedingly simple workup and uncomplicated recovery (six reaction cycles).
• Outstanding thermal stability of CMK-5-SO3H.

Sulfonic acid modified nanostructured CMK-5 is used as an alternative to conventional acid catalysts in the von Pechmann condensation of a neat mixture of substituted phenols with ethyl acetoacetate leading to the formation of coumarin derivatives at 130 °C. In comparison, CMK-5-SO3H showed a greater activity than some other homogeneous and heterogeneous catalysts. Additionally, the catalyst is reused repeatedly for 6 reaction cycles without any evidence of loss of activity, confirming the stability of the covalent bonding of acidic centers. The methodology presented offers reusable strategy for the efficient synthesis of coumarin, simplicity in operation, and green aspects by avoiding toxic conventional catalysts and solvents.

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