Synthesis of Diaryl- and Dialkynylphosphinates From Ubiquitous P^V Sources via a Redox-Neutral Approach

Organophosphinic acids, R₂P(O)(OH), and their derivatives are versatile compounds with applications in catalysis, material chemistry, biomolecular bridging, metal extraction, and flame retardancy. Current synthetic methods primarily rely on white phosphorus (P₄) as a precursor, which is converted into nucleophilic or electrophilic P-synthons through acid-/base-induced disproportionation (e.g., PH₃, [H₂PO₂]^-) or chlorination (PCl₃). However, P₄ poses significant drawbacks due to its highly pyrophoric nature, environmental hazards, and the energy-intensive production process from phosphate ores. Previously, we introduced a method to bypass P₄ in the synthesis of P^V compounds through the redox-neutral activation of phosphates using trifluoromethanesulfonic anhydride (Tf₂O) and pyridine, yielding the electrophilic PO₂ ⁺ phosphorylation reagent [(pyridine)₂PO₂][OTf] (1a[OTf]). While this reagent exhibits high selectivity for alcohols, amides, and (pseudo)halides, it failed to react efficiently with organometallic compounds to form organophosphinates. Here, we present mechanistic studies that rationalize this limitation and report an optimized strategy, which successfully facilitates reactions with Grignard reagents. By replacing the pyridine leaving group in 1a[OTf] with 4-dimethylaminopyridine (DMAP), the reagent [(DMAP)₂PO₂][OTf] (1b[OTf]) is obtained, which enables the selective synthesis of a broad range of diaryl- and dialkynylphosphinates, thereby expanding the scope of redox-neutral phosphate activation.