Intramolecular Arene Epoxidation by Phosphadioxiranes

Singlet oxygen reacts with binaphthyl phosphine derivatives such as 1,1‘-binaphthyl di-tert-butyl phosphine to form the corresponding binaphthyl-2-oxide phosphine oxides. This new intramolecular arene epoxidation reaction proceeds with complete retention of stereochemistry. The
binaphthyl-2-oxide di-tert-butyl phosphine oxide undergoes a slow “NIH-rearrangement” to form the corresponding hydroxylated product. A
transient phosphadioxirane intermediate has been directly observed by low-temperature NMR. Kinetic analyses show that all of the
phosphadioxirane intermediate is converted to product.