Products derived from oxidations of 3,4‐dimethyl‐1‐phenylphosphole‐1‐oxide: A 3‐phenyl‐5,6‐dimethyl‐2,3‐oxaphosphabicyclo[2.2.2]octene‐3‐oxide derivative as a precursor of phenyl metaphosphonic anhydride

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Abstract
Oxidation of 3,4‐dimethyl‐1‐phenylphosphole with peracids or peroxides gives a relatively stable P‐oxide, which can be used in Diels‐Alder reactions to give derivatives with the 7‐phosphanorbornene framework. Oxygen insertion into a C–P bond of this framework occurs smoothly with m‐ chloroperbenzoic acid (MCPBA) providing derivatives of the 2,3‐oxaphosphabicyclo [2.2.2] octene ring system. The phosphole can be converted to this system in a one‐pot synthesis by reaction with excess MCPBA in the presence of N‐phenylmaleimide as dienophile. The phosphole oxide undergoes mono‐epoxidation with MCPBA. Thermal or photochemical fragmentation of the 2,3‐oxaphosphabicyclo [2.2.2] ocetene is a useful source of the 3‐coordinate species Ph–PO2, a meta‐anhydride of phenylphosphonic acid. This species was trapped successfully with a variety of alcohols.