Copper(II) Surface-Functionalized Porous Organic Polymers for One-Pot Synthesis of Sulfoxide via Chan-Lam Cross-Coupling and Photooxidation Reactions

Abstract

Nanometer-sized porous organic polymers (POPs) composed of 4,4difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and tetraphenylmethane units were synthesized via Sonogashira coupling reactions under mini-emulsion conditions. Furthermore, a post-synthetic strategy was employed to covalently attach copper(II)−phenanthroline complexes to the surface of the POP nanoparticles through a thiol-yne click reaction. Detailed characterization of the photocatalyst, TEPM−BDP−Phen@Cu, using techniques such as solid-state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and inductively coupled plasma atomic emission spectrometry demonstrated that the copper(II)− phenanthroline complexes were successfully anchored on the surface of the POPs. TEPM−BDP−Phen@Cu exhibited dual catalytic activities, enabling it to catalyze the Chan-Lam cross-coupling reaction by external copper complexes and photocatalytically oxidize thioanisole into the corresponding sulfoxide by internal BODIPY-based polymeric networks via singlet oxygen. Taking the synthesis of methyl phenyl sulfoxide as the model reaction, TEPM−BDP−Phen@Cu was proven to be a good heterogeneous catalyst for the one-pot synthesis of methyl phenyl sulfoxide from S-methyl 4-toluenethiosulfonate and phenylboronic acid with a yield of 78%. Importantly, this reaction could be performed under mild conditions (room temperature, atmospheric pressure, and oxygen molecules in air as the oxidant) and avoid unpleasant odors of thioethers.