Uses and Synthesis of Diphenylphosphine oxide

Uses

Diphenylphosphine oxide is a commonly used chemical reagent in the laboratory. It is often used in the preparation of triphenylphosphine oxide, alkenyldiphenylphosphine oxide, addition to alkynes and Wittig-Horner reaction reagents.

Synthesis

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

(C2H5O)2P(O)H + 3 C6H5MgBr → (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.

Reactions

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

(C6H5)2P(O)H⇆ (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.