Preparation and ESR Studies of New Stable Tocopheroxyl Model Radicals

New tocopherol (vitamin E) model compounds (tocopherol 1; 7-t-butyl-2,2-dimethyl-6-chromanol, tocopherol 2; 7-t-butyl-2,2,5-trimethyl-6-chromanol, and tocopherol 3; 5,7-diisopropyl-2,2-dimethyl-6-chromanol) have been synthesized by condensation of 2-methyl-3-buten-2-ol to the corresponding alkylhydroquinone. Electron spin resonance measurements were performed for the tocopheroxyl radicals obtained from the above tocopherol model compounds by oxidizing the phenol precursors with PbO2 in toluene. The proton hyperfine coupling constants and giso-values were determined. The tocopheroxyl radicals 2 and 3 having large alkyl substituents at both ortho positions (C-5 and C-7) are fairly stable, and the radical stability, as measured by the intensities of the ESR signals, increases in the order tocopheroxyl 1<α-tocopheroxyl model