Preparation of TiO2 Nanoparticles using Raphanus sativus Leaf Extract to Promote the Claisen-Schmidt Condensation

Introduction: The development of eco-friendly and sustainable approaches for the synthesis of nanomaterials and their catalytic properties has gained considerable attention in recent years. In this study, Raphanus sativus leaf extract was employed for the green synthesis of TiO2 NPs. The synthesized TiO2 NPs were subsequently investigated for their catalytic potential in organic transformations, particularly in the Claisen-Schmidt condensation reaction. Methods: TiO2 NPs were synthesized via an ultrasound-assisted green route using Raphanus sativus leaf extract as a natural reducing, capping, and stabilizing agent. Their catalytic activity was evaluated in the solvent-free, microwave-assisted Claisen–Schmidt condensation of 3,3-dimethyl-1,5-dioxa-spiro[5.5]undecan-9-one with substituted aromatic aldehydes to afford bis-benzylidene derivatives. The catalyst showed effective reuse in subsequent cycles. Results: The characterization studies confirmed the successful formation of nanosized TiO2 particles predominantly possessing the anatase crystalline phase. The biogenic nano-TiO2 showed excellent catalytic activity in the Claisen-Schmidt condensation, affording bis-benzylidene derivatives in good yields under solvent-free microwave conditions with reduced reaction times, and it retained high catalytic efficiency upon reuse. Discussion: The FT-IR, XRD, SEM, TEM, EDX, UV–Vis, and XPS analyses provided evidence for the structural, morphological, elemental, and electronic characteristics of the synthesized nanoparticles, and their reuse performance was also evaluated. The structures of the synthesized compounds were confirmed using appropriate spectroscopic techniques and by single-crystal X-ray diffraction analysis. Conclusion: We have developed a green and biogenic method for the synthesis of TiO2 NPs under sonication. The synthesized nano-TiO2 exhibited excellent catalytic efficiency in the Claisen–Schmidt condensation under solvent-free microwave-assisted conditions, affording the desired bis-benzylidene derivatives in good yields within shorter reaction times. In addition, the biogenic TiO2 NPs showed good reuse performance, highlighting their potential as an efficient, sustainable, and environmentally friendly heterogeneous catalyst for organic transformations.