Ultrasound Promoted, Solvent‐Free Synthesis of Arylidine and Hetero‐Arylidinemalononitriles Using Waste <i>Mangifera Indica</i> Peel Ash as Natural, Biodegradable Heterogeneous Catalyst

Abstract Knoevenagel condensation is one of the very popular and established C─C bond forming reactions which is helpful in synthesizing compounds of diverse applications. Arylidine and heteroarylidinemalononitriles are examples of such beneficial compounds, which are precursors to several biologically active heterocycles. The work presented here demonstrated the application of waste Mangifera indica peel ash as a natural, cheap, biodegradable, and heterogeneous catalyst in achieving the synthesis of electronically diverse arylidine malononitriles. The reaction performed under solvent‐free and ultrasound‐assisted conditions led to the product formation within a short reaction time of 10–25 min in good to excellent yield (80%–98%). The present method, comprising waste mango peel ash as a catalyst, solvent‐free, ultrasound‐assisted reaction conditions, and a short reaction time is based on the principles of green chemistry.