The reaction of tetraphenyldiphosphine with aromatic carboxylic acids

Abstract

Tetraphenyldiphosphine and benzoic acid at 180° give α-(diphenylphosphinyloxy)benzyldiphenylphosphine oxide. Aromatic acids containing electron-attractive para substituents give analogous oxides; when the para substituent is capable of supplying electrons these oxides are further reduced to substituted benzyldiphenylphosphine oxides. From a study of the properties of benzoyloxydiphenylphosphine, benzoyldiphenylphosphine, and benzoyldiphenylphosphine oxide these reactions are shown to involve formation of the aroyldiphenylphosphine and/or its oxide, followed by addition to the carbonyl of diphenylphosphine oxide and rearrangement to the product. The rearrangement of α-hydroxyalkylphosphine oxides, R¹R²C(OH)P(:O)R₂ to give the phosphinates R¹R²CHOP(:O)R₂ occurs when R¹ is able to stabilise an adjacent carbanion.