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

N-(1-Adamantyl) phenylphosphonamidic acid (3), an easily prepared soli d, on heating in toluene or 1,2-dichloroethane gave the crystalline ad amantylamine salt of the anhydride PhP(O)(NHAd)-O-PPh(O)(OH). The mech anism is proposed to involve first the fragmentation of 3 to form phen yl dioxophosphorane, PhPO(2), which then acts as a phosphorylating age nt 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 P hPO(2) was trapped as the monoalkyl phenylphosphonate. The OH groups o n the surface of silica gel were also phosphonylated by PhPO(2). The a cidic OH group of a phosphoric acid monoester (thymyl phosphate) was p hosphonylated to give Thy-O-P(O)(OH)-O-PPh(O)(OH). It is concluded fro m this study that N-(1-adamantyl) phenylphosphonamidic acid is a usefu l precursor of phenyl dioxophosphorane, which can perform valuable pho sphonylation operations.