Porous Organic Polymer Constructed From Thiazolo‐Thiazole and Cyclophosphazene as a Heterogeneous Photocatalyst for Visible Light‐Mediated Synthesis of Isatins, Thiocyanoindoles, and Thiocyanoanilines

A porous organic polymer (POP) based on hexakis(4-formylphenoxy)cyclophosphazene (HFCP), that is, HFCPTzPOP, was synthesized by condensation reaction with dithiooxamide. The polymer is shown to exhibit excellent visible light absorption, enabling its application as a heterogeneous photocatalyst for the conversion of indoles to isatins and 3-thiocyanoindoles, and selective thiocyanation of anilines at the para position. The photocatalytic reactions occur under mild conditions in oxygen atmosphere without the addition of any toxic metal or oxidizing agent. HFCPTzPOP acts as a photoredox catalyst in oxidative transformations, converting molecular oxygen into singlet oxygen (¹O₂) and superoxide radical anion (O₂ ^•-) through energy transfer and electron transfer processes, respectively. It is shown that the photocatalyst can be easily recycled up to 10 cycles without any loss of catalytic activity.