Visible light-mediated synthesis of N‑aryl phenothiazines catalyzed by a conjugated microporous polymer-copper complex

Abstract

N‑Aryl phenothiazines are privileged heterocyclic scaffolds with broad utility in optoelectronic materials, photoredox catalysis, and medicinal chemistry. However, their conventional synthesis often requires strong bases and elevated temperatures, limiting sustainability and scalability. Herein, we report a mild, base‑free, and visible‑light‑driven protocol for the efficient synthesis of N‑aryl phenothiazines via Chan–Lam coupling, enabled by a conjugated microporous polymer-copper complex PPAA‑Cu. The reaction proceeds under ambient conditions using ethanol as solvent and blue LED irradiation, tolerating a wide range of functional groups on both aryl boronic acids and phenothiazine derivatives to deliver the desired products in up to 87% yield. Notably, PPAA‑Cu can be readily recovered and reused for at least five cycles without significant loss in activity or copper leaching. This work establishes a sustainable and heterogeneous photocatalytic platform for the synthesis of N‑aryl phenothiazines and highlights the potential of conjugated microporous polymers in visible‑light‑driven organic transformations.