Synthesis of tertiary phosphine oxides by alkaline hydrolysis of quaternary phosphonium zwitterions using excess t-BuOK and stoichiometric water

Abstract

Hydrolysis of quaternary arylphosphonium zwitterions bearing COO⁻ and those in situ generated from the corresponding salts bearing Ac or OH at the aryl ring by using excess t-BuOK and stoichiometric water affords tertiary arylphosphine oxides in moderate to excellent yield, in contrast to hydrolysis of these zwittertion or salts in aqueous NaOH that mainly provides phosphine oxides with the loss of the aryl group. Under the t-BuOK/water conditions, hydrolysis of carbonyl stabilized ylides Ph₃P = CHCOR (R = Ph, Me, and OEt), which partially exist as phosphonium enolates, prefers to produce Ph₂P(O)CH₂COR. Further reduction of Ph₂P(O)CH₂COMe by PhSiH₃ allows the preparation of Ph₂PCH₂COMe in 43% yield.

Graphical Abstract

Keywords:

• Alkaline hydrolysis
• phosphorus ylide
• quaternary phosphonium salt
• quaternary phosphonium zwitterion
• tertiary phosphine oxide

Additional information

Funding

We thank the National Natural Science Foundation of China for their financial support of our program [Grant No. 21272170].