FRAGMENTATION OF A PHENYLPHOSPHONAMIDIC ACID AS A NEW TECHNIQUE FOR THE GENERATION OF PHENYL DIOXOPHOSPHORANE

Abstract

N-(1-Adamantyl) phenylphosphonamidic acid (3), an easily prepared solid, on heating in toluene or 1,2-dichloroethane gave the crystalline adamantylamine salt of the anhydride PhP(O)(NHAd)[sbnd]O[sbnd]PPh(O)(OH). The mechanism is proposed to involve first the fragmentation of 3 to form phenyl dioxophosphorane, PhPO₂, which then acts as a phosphorylating agent to unreacted 3. This mechanism was supported by the observation of first-order kinetics for the consumption of 3. When the phosphonamidic acid was fragmented in the presence of an alcohol, the intermediate PhPO₂ was trapped as the monoalkyl phenylphosphonate. The OH groups on the surface of silica gel were also phosphonylated by PhPO². The acidic OH group of a phosphoric acid monoester (thymyl phosphate) was phosphonylated to give Thy[sbnd]O[sbnd]P(OXOH)[sbnd]O[sbnd]PPh(O)(OH). It is concluded from this study that N-(1-adamantyl) phenylphosphonamidic acid is a useful precursor of phenyl dioxophosphorane, which can perform valuable phosphonylation operations.

Key Words:

• N-(1-adamantyl) phenylphosphonamidic acid
• phenyl dioxophosphorane
• phosphonylation