Cobalt(II) chloride-catalyzed oxidation of cyclic ethers with oxygen in 1,2-dimethoxyethane gives the corresponding lactones in reasonable to excellent yields. Oxidation of acyclic alkyl benzyl ethers affords the corresponding esters in yields which are dependent on the stability of alkyl radicals. The more stable the alkyl radical, the lower the yield of the formed ester. Oxidation of acyclic alkyl and heterocyclic ethers is also described. A free-radical mechanism is proposed involving participation of superoxocobalt.
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