Synthesis of spiroindoline derivatives and biphenyl compounds in green solvent via a “capture–release” mechanism using modified polyacrylonitrile fiber as a catalyst

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Green synthesis of critical bioactive molecules and fine chemicals is attracting increasing interest. This study investigates the use of two distinct functionalized polyacrylonitrile (PAN) fibers (PANEDBPF and PANEDBP-Pd0F) as effective catalysts in a green solvent comprising ethanol and water. Firstly, a PAN fiber was modified using 2-(diphenylphosphino) ethylamine, a strongly nucleophilic phosphine compound, to obtain PANEDBPF. Spiroindoline derivatives were obtained in 98 % yields when the reaction was conducted using 5 mol% of PANEDBPF as the catalyst at 70 °C for 30 min. Next, we loaded PdNPs onto PANEDBPF to obtain PANEDBP-Pd0F. When the Suzuki coupling reaction was conducted at room temperature (25 °C) using 0.5 mol% of PANEDBP-Pd0F, the products were obtained in an extremely high yield of 99 %. Additionally, the unique enrichment of the substrate by the functionalized fibers during the reaction and the subsequent release of the product from the microenvironment conform to the “capture–release” reaction mode of catalysis. Both PANEDBPF and PANEDBP-Pd0F demonstrated good gram-scale amplification, repeatability, catalytic activity, and stability. Hence, they are highly promising candidates for green chemistry applications.