Polystyrene-Anchored Palladium(II) Schiff Base Complex: A Reusable Catalyst for Phosphine-Free and Copper-Free Sonogashira Cross-Coupling Reaction in Aqueous Medium

Abstract

A novel polystyrene-supported palladium(II) complex, an excellent and recyclable catalyst, was synthesized for Sonogashira reactions. The present complex shows high catalytic activity for Sonogashira cross-coupling reaction of aryl halides with phenylacetylene under phosphine-free and copper-free reaction conditions in aqueous (DMF–H₂O) medium. The catalyst could be reused for at least six reaction cycles with almost unchanged catalytic properties.

Keywords:

• Aqueous medium
• aryl halides
• palladium(II) complex
• Sonogashira cross-coupling

ACKNOWLEDGMENTS

We gratefully acknowledge the Department of Science and Technology (DST), the Council of Scientific and Industrial Research (CSIR), and the University Grant Commission (UGC), New Delhi, India, for funding. One of the authors, K. T., is thankful to the UGC (eastern region), India, for financial support. We also thank the DST and UGC, New Delhi, India, for providing instrumental support under the Funding for Infrastructure in Science and Technoloy (FIST) and SAP program.

Notes

^a Reaction conditions: bromobenzene (1.0 mmol), phenylacetylene (2.0 mmol), catalyst (1.0 mol% Pd), and solvent (6 mL). Yields determined by GC analysis.

^a Reaction conditions: aryl halide (1.0 mmol), phenylacetylene (2.0 mmol), catalyst (1.0 mol% Pd), Et₃N (2.0 mmol), TBAB (1.0 mmol), and DMF–H₂O (1:1, 6 mL) at 70 °C.

^b Products were identified by comparison of their GC-MS and ¹H NMR spectral data with those reported in the literature.

^c Conversion of reactant was determined by GC and GCMS analysis using dodecane as internal standard.