Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent

Article abstract of DOI:10.1246/bcsj.70.2561

NaBrO₃ combined with NaHSO₃ was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO₃/NaHSO₃ reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO₃/NaHSO₃, in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60°C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-l-heptene with NaBrO₃/NaHSO₃ afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major products.