Regioselective intramolecular oxidation of phenols and anisoles by dioxiranes generated in situ

A novel method for regioselective oxidation of phenols and anisoles has bee n developed in which dioxiranes, generated in situ from ketones and Oxone, oxidize phenol derivatives in an intramolecular fashion. A series of ketone s with electron-withdrawing groups, such as CF3, COOMe, and CH2Cl, were att ached to phenols, anisoles, or aryl rings via a C-2 or C-3 methylene linker . In a homogeneous solvent system of CH3CN and H2O, oxidation of phenol der ivatives 1-10 afforded spiro 2-hydroxydienones in 24-55% yields regardless of the presence of other substituents (ortho Me, meta Me or Br) on the aryl ring and the length of the linker. Experimental evidences were provided to support the mechanism that involves a regioselective pi bond epoxidation o f aryl rings followed by epoxide rearrangement and hemiketal formation.