Highly effective and recoverable Pd(II) catalyst immobilized on thermally stable Schiff base polymer containing phenol group: Production, characterization and application in Suzuki coupling reactions

Abstract

In this study, a novel highly efficient, recoverable, sustainable, and thermally stable Schiff base polymer-Pd(II) catalyst was designed for Suzuki coupling reactions in synthesis of biaryl compounds for the first time. Firstly, a novel Schiff base polymer containing phenol, Poly(4-((pyridine-2ylimino)methyl)benzene-1,3-diol) (P (4-PMB)), which was used as a support material in catalyst design, was synthesized in aqueous alkaline medium via oxidative polycondensation of 4-((pyridine-2-ylimino)methyl)benzene-1,3-diol (4-PMB) with NaOCl oxidant. The effects of oxidant concentration, polymerization temperature, and time on yield and molecular weight of the polymer were investigated. The structures of the synthesized compounds were illuminated by UV–Vis, FTIR, 1HNMR, XRD, TG/DTG, and SEM/EDAX methods. Then, Pd(II) complex of P (4-PMB) was produced, and its catalytic performance was tested in the synthesis of various biaryl compounds by Suzuki reactions using microwave irradiation technique which is a highly effective, fast, solvent-free and green method. The designed Pd(II) catalyst exhibited superior catalytic effect against syntheses of various biaryl compounds with high conversion yields (99%) and very low catalyst loading (0.01 mol%) for 5 min. Recyclability and reproducibility tests showed that the catalyst could be reused for seven successive runs without any great loss of its catalytic performance (84%).