Diphenylphosphine oxide explained

Diphenylphosphine oxide is an organophosphorus compound with the formula (C₆H₅)₂P(O)H. It is a white solid that soluble in polar organic solvents.^[1]

Synthesis

Diphenylphosphine oxide can be prepared by the reaction of phosphonic esters, such as diethylphosphite, with Grignard reagents followed by acid workup:^[2]

(C₂H₅O)₂P(O)H + 3C₆H₅MgBr → (C₆H₅)₂P(O)MgBr + C₂H₅OMgBr

(C₆H₅)₂P(O)MgBr + HCl → (C₆H₅)₂P(O)H + MgBrCl

Alternatively, it may be prepared by the partial hydrolysis of chlorodiphenylphosphine or diphenylphosphine.^[3]

Reactions

Diphenylphosphine oxide exists in equilibrium with its minor tautomer diphenylphosphinous acid, ((C₆H₅)₂POH:

Diphenylphosphine oxide is used in Buchwald-Hartwig coupling reactions to introduce diphenylphosphino substituents.

Thionyl chloride converts diphenylphosphine oxide to chlorodiphenylphosphine.

Organophosphinous acids are deoxygenated with DIBAH. The resulting secondary phosphines are precursors to phosphine ligands.^[4]

References

1. Book: 10.1002/047084289X.rd428.pub2. Diphenylphosphine Oxide. Encyclopedia of Reagents for Organic Synthesis. 2007. Saunders. Jeffrey O.. Wang. Zheng. Ding. Kuiling. 978-0-471-93623-7.
2. 10.1039/JR9570002413. 1957. Hunt. B. B.. Saunders. B. C.. J. Chem. Soc.. 2413–2414. Preparation and Reactions of Diphenylphosphine Oxide.
3. Rauhut . M. M. . Currier . Helen A. . Oxidation of Secondary Phosphines to Secondary Phosphine Oxides . The Journal of Organic Chemistry . November 1961 . 26 . 11 . 4626–4628 . 10.1021/jo01069a102.
4. Synthesis Of Electron-Deficient Secondary Phosphine Oxides And Secondary Phosphines: Bis[3,5-bis(Trifluoromethyl)phenyl]phosphine Oxide And Bis[3,5-bis(Trifluoromethyl)phenyl]phosphine. Carl A. Busacca . Jon C. Lorenz . Paul Sabila . Nizar Haddad . Chris H. Senanyake . Org. Synth.. 2007. 84. 242. 10.15227/orgsyn.084.0242.