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Synthesis of phosphonium salts

C-P activation of phosphonium salts enables a "group-substitution" synthesis of trivalent phosphines. An alkylation of phosphines to provide phosphonium salts is followed by a Pd-catalyzed "de-arylation" via C-P activation and transfer hydrogenation. With this method, a series of trivalent phosphines were prepared from commercially available triarylphosphines.
M. Lei, X. Chen, Y. Wang, L. Zhang, H. Zhu, Z. Wang, Org. Lett., 2022, 24, 2868-2872.

Two approaches for the synthesis of substituted phosphonium salts from benzyl alcohols have been developed: direct mixing of alcohol, TMSBr, and PPh₃ in 1,4-dioxane followed by heating at 80 °C enables the conversion of acid-sensitive substrates, while sequential addition of TMSBr, and PPh₃ gave higher yields for benzyl alcohols bearing electroneutral or electron-withdrawing substituents.
P. N. Chalkiki, T. T. Magkoev, A. V. Gutnov, O. P. Demidov, M. G. Uchuskin, I. V. Trushkov, V. T. Abaev, J. Org. Chem., 2021, 86, 9838-9846.