Synlett 2007(5): 0765-0768  
DOI: 10.1055/s-2007-970758
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Novel Catalytic Hypervalent Iodine Oxidation of p-Alkoxyphenols to p-Quinones Using 4-Iodophenoxyacetic Acid and Oxone®

Takayuki Yakura*, Tatsuya Konishi
Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani, Toyama 930-0194, Japan
e-Mail: yakura@pha.u-toyama.ac.jp;
Further Information

Publication History

Received 26 December 2006
Publication Date:
08 March 2007 (online)

Abstract

A novel catalytic hypervalent iodine oxidation of phenol derivatives using 4-iodophenoxyacetic acid and Oxone® was developed. Reaction of p-alkoxyphenols with a catalytic amount of 4-iodophenoxyacetic acid in the presence of Oxone® as a co-oxidant in acetonitrile-water (2:1) gave the corresponding p-quinones in ­excellent yields without purification.

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It is possible that iodine(III) species may be oxidized by Oxone® to regenerate iodine(V) species before the reaction of iodine(III) with phenol.

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Typical Reaction Procedure: To a solution of 2 (1 mmol) in MeCN-H2O (2:1, 6 mL) was added 1a (0.2 mmol) followed by Oxone® (1 mmol) at r.t. and the resulting mixture was stirred at the same temperature. After 2 was completely consumed indicated by TLC, the mixture was diluted with EtOAc and washed with H2O. The organic layer was then washed with aq sat. NaHCO3 solution and dried, concentrated to give pure 3. If necessary, the product was purified by column chromatography on silica gel to give pure quinone.
The alkaline solution was acidified by 10% HCl solution and extracted with EtOAc. The organic layer was washed with aq Na2S2O3 solution and dried, then concentrated to give recovered 1a which was purified by recrystallization from Et2O-hexane.
All new compounds gave satisfactory spectroscopic data.