Waste to wealth: water extract of papaya peel ash as a biodegradable alternative of conventional catalyst for the sustainable C–C bond formation via Knoevenagel condensation reaction

The investigation of organic synthesis with bio-waste materials has emerged as a high researched field owing to its environmentally benign methodology. The current work presents the Water Extract of Papaya Peel Ash (WEPPA) as a reusable and green catalyst for the efficient synthesis of the acrylidene malononitrile derivatives, thus forming C–C bonds via Knoevenagel condensation reaction. The catalyst underwent further characterization using several techniques such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), and high-resolution transmission electron microscopy (HR-TEM) methods. The presence of basic sites in WEPPA promotes its use as a catalyst in the synthesis of acrylidene malononitrile derivatives. The isolated product did not necessitate any column chromatographic purification and was recrystallized using hot ethanol. A total of nine derivatives were synthesized rapidly at room temperature within 2–15 min, yielding an excellent range of 89–94% and subsequently verified using nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopic techniques. In addition, the catalyst can be reused for up to four cycles with its efficiency being 91%, 89%, 87%, and 85% in 1st, 2nd, 3rd, and 4th cycle.