Cu(II)-crosslinked carboxymethylcellulose entrapped in-situ generated Cu2O nanoparticles composite beads: a highly efficient catalyst for ipso-iodination of arylboronic acids

In this study, we successfully synthesized Cu₂O@Cu(II)-CMC composite beads via a one-step process, where Cu(II) ions are crosslinked with sodium carboxymethylcellulose (CMC-Na) through an ion exchange reaction to form composite beads with a three-dimensional (3D) network. Simultaneously, the Cu(II) ions undergo in-situ partial reduction by the hydroxy groups of CMC-Na, generating Cu₂O nanoparticles (NPs) that are entrapped and uniformly confined within these as-formed beads. The composite beads were systematically characterized using X-ray diffraction (XRD), Fourier transform infraredspectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermogravimetric analysis (DTG), and inductively coupled plasma atomic emission spectrometry (ICP-AES). For the first time, their catalytic performance was evaluated in the ipso-iodination of arylboronic acids. The results revealed excellent activity under mild conditions, achieving high yields in short reaction times at room temperature while tolerating a broad range of functional groups. The superior catalytic performance can be attributed to: (1) the regulatory effect of carboxylate and hydroxy groups on the metal centers; (2) the 3D porous structure facilitating mass transfer; and (3) the activation of phenylboronic acid via esterification with hydroxy groups of CMC. Additionally, copper-carboxylate chelation minimized leaching of active species, enabling the catalyst to maintain high efficiency up to six consecutive reaction cycles with easy recovery by simple filtration.

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