Catalytic hypervalent iodine oxidation using 4-iodophenoxyacetic acid and oxone: oxidation of p-alkoxyphenols to p-benzoquinones.

A catalytic hypervalent iodine oxidation of p-alkoxyphenols using 4-iodophenoxyacetic acid (1a) and Oxone((R)) was developed. Reaction of p-alkoxyphenol (2) with a catalytic amount of 1a in the presence of Oxone((R)) as a co-oxidant in 2,2,2-trifluoroethanol-water (1 : 2) gave the corresponding p-quinone (3) in excellent yield without special operation. The substituent effect on iodobenzene ring in the oxidation was observed; p-alkoxy is the most effective, with the series following the approximate order p-RO>p-Me, o-MeO, m-MeO>H>o-CO(2)H. And remarkable solvent effects were observed.