Photocatalytic radical (O)P–P(O) bond formation: access to diphosphine dioxides for thermoset protection

Abstract

Although significant progress has been made in the construction of organic phosphorus compounds using P-centered radicals, challenges have arisen in constructing P–P bonds via P-centered radicals due to their high reactivity and thermodynamic instability. Here, this work developed a photocatalytic radical coupling strategy and realized a mild approach for constructing novel diphosphine dioxide compounds bearing an (O)P–P(O) bond from structurally diverse P(O)H compounds via self-coupling or cross-coupling. This method attains near-quantitative yields through only simple filtration, features recyclable catalyst/solvent systems, and functions efficiently on a kilogram scale. Crucially, the diphosphine dioxide compounds endow thermosets with multi-environmental stability, simultaneously achieving high flame retardancy, exceptional resistance to UV radiation, and chemical corrosion at minimal loadings.