Free-Radical Reagents. 2. Oxidation and Addition Products from the Reaction of Di-tert-Butyliminoxyl with Phenols

摘要

The blue, persistent free-radical di-tert-butyliminoxyl, t-Bu2C=NO (1), oxidizes p-hydroquinones and catechol in organic solvents to the corresponding quinones in good yield. With simple phenols, the reaction takes three pathways. 2-Naphthol and 9-phenanthrol are oxidized to the corresponding o-quinones, while 1-naphthol, phenol, and 2,6-di-tert-butylphenol give 4,4-disubstituted oxime ethers. Para-substituted phenols afford cyclohexadienones with one di-tert-butyliminoxyl at the original para position. Some of these adducts can be prepared by cooxidation of 1-H and the phenol with ceric ion. Rate constants for some of the reactions of 1 with phenols have been measured by kinetic EPR spectroscopy.