CYCLIC-ACYCLIC EQUILIBRIUM AND SELECTIVE P-O BOND-CLEAVAGE IN 2-HYDROXYPHENYLDIPHENYL-PHOSPHINATE, PH2P(O)OC6H4OH

The equilibrium in the Ph2P(O)OC6H4OH-base system may be shifted by va rying the base concentration, where base = imidazole, triethylamine, d imethyl sulfoxide, pyridine, and 1,4-dioxane. This equilibrium was stu died by P-31 and H-1 NMR, and information about the symmetry of phosph orus-containing intermediates is provided by the H-1 NMR spectrum of t he catecholyl ring, with its ABCD spin system. The equilibrium is also affected by trifluoroacetic acid. A mechanism is proposed that involv es protonation-deprotonation, cyclic-acyclic equilibria, and selective P-O bond cleavage, with all steps occurring rapidly on the NMR time s cale.