Phosphoric acid activation, reduction and transformation processes: efficient preparation of triarylphosphines†

In this study, we developed a pre-activation reduction strategy to enable the efficient activation, reduction, and conversion of inert phosphate. Our method allows for the direct activation of [TBA][H₂PO₄] using oxalyl chloride at room temperature, followed by reduction with HSiCl₃, enabling rapid synthesis of the low-valent bis(trichlorosilyl)phosphorylated anion [P(SiCl₃)₂]⁻ in 24 h. Follow-up experiments demonstrated that the resulting anion could be successfully coupled with aryl halides by Pd-catalyst leading to the synthesis of a series of triarylphosphine compounds with good tolerance to a wide range of functionalized aryl halides. This represents a novel strategy for synthesizing organophosphorus compounds (OPCs) from phosphoric acid.