Reactions of alkoxy radicals. IV. Intramolecular hydrogen-atom transfer in the presence of cupric ion: A novel directive effect

Abstract

2-Methyl-2-hexyloxy radical (V), generated by ferrous-ion reduction of 2-methyl-2-hexyl hydroperoxide, undergoes intramolecular hydrogen-atom transfer to the extent of 44%, yielding 2-hydroxy-2-methyl-5-hexyl radical (XIII). Oxidation of the latter with cupric ion in acetic acid affords a mixture of 2-methyl-4-hexen-2-ol (XXI) and 2-methyl-5-hexen-2-ol (XX). Similar results were obtained using radicals derived from 2,5-dimethyl-2-hexyl hydroperoxide and 2-methyl-2-heptyl hydroperoxide. In each case the preponderant formation of the unsaturated alcohol having an olefinic link in the δ-position with respect to the hydroxy group demonstrates the operation of a novel directive effect, for which a possible mechanism is discussed. Some other examples of metal-ion oxidation of alkyl radicals are described. No product arising from intramolecular hydrogen-atom transfer was isolated from ferrous-ion reduction of 2,4,4-trimethyl-2-pentyl hydroperoxide.