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

Abstract

A novel method for regioselective oxidation of phenols and anisoles has been developed in which dioxiranes, generated in situ from ketones and Oxone, oxidize phenol derivatives in an intramolecular fashion. A series of ketones with electron-withdrawing groups, such as CF 3COOMe, and CH 2Cl, were attached to phenols, anisoles, or aryl rings via a C 2 or C 3 methylene linker. In a homogeneous solvent system of CH 3CN and H 2O, oxidation of phenol derivatives 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 π bond epoxidation of aryl rings followed by epoxide rearrangement and hemiketal formation.