Multifunctional Catalyst for One-Pot Synthesis of E-Chalcones

E-chalcones, a subclass of α,β-unsaturated ketones, are widely recognized for their bioactive properties and serve as key intermediates in producing pharmaceuticals, pesticides, and specialty chemicals. Traditional synthesis methods involve multi-step processes such as Claisen–Schmidt condensation or separate carbonylation and hydrogenation reactions. These often require harsh conditions, multiple catalysts, and extensive purification steps. Additionally, functional group compatibility and overall yields remain limited in conventional procedures. To address these challenges, there is a growing interest in developing integrated catalytic systems that simplify synthetic protocols, minimize waste, and improve product selectivity.

The core of this invention is a bifunctional heterogeneous catalyst: Ru@SiO₂–[Pd–NHC]. It is synthesized via a two-step immobilization method: (1) Ru nanoparticles are deposited onto partially dehydroxylated silica using [Ru(2-methylallyl)₂(cod)] under hydrogen at high pressure and temperature, and (2) a Pd–NHC complex with triethoxysilane functional groups is covalently grafted onto the silica surface via silanization. The resulting material contains well-dispersed Pd(II) and Ru(0) species anchored to the support.

The catalyst performs a one-pot, two-step transformation. First, carbonylative Sonogashira coupling of aryl iodides and alkynes under CO yields ynones, mediated by the immobilized Pd–NHC. Second, Ru nanoparticles, under mild hydrogen pressure, selectively reduce the triple bond in the ynone to produce E-chalcones with high stereoselectivity. The process avoids palladium leaching, demonstrates structural integrity post-reaction, and allows for multiple recycling cycles with consistent performance.

Advanced spectroscopic and microscopic characterizations (NMR, XPS, STEM-EDX) confirm the dual-site integration, coordination states, and particle stability. Reactions are conducted in green solvents such as propylene carbonate, further emphasizing sustainability.

• Single-vessel synthesis integrating carbonylation and hydrogenation reduces time, waste, and purification steps.
• Multifunctional catalyst co-localizes Ru and Pd centers on a stable silica support, enhancing synergistic reactivity.
• High selectivity for E-chalcones is achieved through controlled hydrogenation of ynones.
• Reusable system with minimal loss in catalytic activity over multiple reaction cycles.
• Environmentally friendly: compatible with green solvents and avoids use of toxic ligands or additives.

• Pharmaceutical synthesis of anti-inflammatory, anticancer, or antimicrobial chalcone-based compounds.
• Agrochemical production of active chalcone derivatives for pesticide or herbicide formulations.
• Fine chemical manufacturing of dyes, fragrances, and intermediates for functional materials.
• Green chemistry education and research involving sustainable catalysis techniques.
• Catalyst development as a model for dual-site catalysis in other complex reaction cascades.

Durai, M., Wu, Y., Johny, J., Hetaba, W., Wiegand, T., Leitner, W., & Bordet, A. (2025). One-pot synthesis of E-chalcones using a multifunctional catalyst comprised of ruthenium nanoparticles and palladium N-heterocyclic carbene complexes immobilized on silica. Chemical Science, 16(14), 5776-5785.