Oxidation reactions using tetra-n-butylammonium peroxydisulfate

Abstract

Tetrabutylammonium peroxydisulfate has been prepared from tetrabutyl-ammonium hydrogen sulfate and potassium persulfate and shows strong oxidizing abilities. This peroxide shows high solubility in organic solvents, such as methylene chloride, chloroform, acetonitrile, and acetone, in contrast to the poor solubility of the known metal peroxydisulfates. Tetrabutylammonium peroxydisulfate has turned out to be a useful source of tetrabutylammonium sulfate radical, which is relatively stable in organic solvents and can be used at higher temperature than 20℃. Facile iodination and bromination of aromatic compounds have been achieved by use of tetrabutylammonium peroxydisulfate and iodine in good yields. Regioselective iodination occurred at para position to methoxy group. While α,β-unsaturated ketones afforded α-iodinated or α-brominated products. When 1,3-dicarbonyl compounds were reacted under the same conditions, 2-position was iodinated. Deprotection of ρ-methoxybenzyl ethers to alcohol has been successfully achieved by use of tetrabutylammonium peroxydisulfate in the presence of iodine in good yields. Tetrabutylammnoium peroxydisulfate has been also found to be a good deprotecting reagent of removal of the trityl group : Treatment of 5``-O-dimethoxytrityl uridine or thymidine with the peroxydisulfate gave the correspond ing dedimethoxytritylated nucleosides in excellent yields under neutral and mild conditions and without causing any side reactions such as cleavage of the glycosidic bond. Furthermore α,β-unsaturated ketones or aldehydes reacted with tetrabutylammonium peroxydisulfate in the presence of hydrogen peroxide and sodium hydroxide to give the corresponding epoxides in excellent yields. A new facile and efficient allyl ether cleavage reaction to the alcohol has been found. Because of simplicity and chemoselectivity of this reaction, this procedure will be undoubtedly extended for the use of allyl groups for the protection of a variety of hydroxy groups.