C(sp 3 )-H hydroxylation of fluorenes, oxindoles and benzofuranones with a Mg(NO 3 ) 2 -HP(O)Ph 2 oxidation system.

A novel oxidation system in which magnesium nitrate [Mg(NO3 )2 ] is used as an oxidant in the presence of diphe-nylphosphine oxide [HP(O)Ph2 ] permits the C(sp3 )-H hydroxylation of fluorenes, oxindoles, and benzofuranones. This method features high efficiency, good functional group tolerance, and operational simplicity. The synthetic utility is highlighted by further transformations to valuable organic materials.