Article

The equilibrium in the Ph 2 P(O)OC 6 H 4 OH-base system may be shifted by varying the base concentration, where base = imidazole, triethylamine, dimethyl sulfoxide, pyridine, and 1,4-dioxane. This equilibrium was studied by 31 P and 1 H NMR, and information about the symmetry of phosphorus-containing intermediates is provided by the 1 H NMR spectrum of the catecholyl ring, with its ABCD spin system. The equilibrium is also affected by trifluoroacetic acid. A mechanism is proposed that involves protonation-deprotonation, cyclic-acyclic equilibria, and selective P-O bond cleavage, with all steps occurring rapidly on the NMR time scale.Key words: Ph 2 P(O)OC 6 H 4 OH-base system, cyclic-acyclic equilibrium, and selective P-O bond cleavage.