Antioxidants and Light Stabilizers. Part 1. Reactions of an Indolinone Nitroxide and Phenoxy radicals. X-ray Cristallographic Analysis of 1-[O-(3,5-di-tert-butyl-4-hydroxy)-benzyl]-1,2-dihydro-2-methyl-2-phenyl-3-oxo-3H-indole and 3,5,3’,5’-Tetra-tert-butylstilbene-4,4’-quinone

Abstract: 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butylphenol undergo hydrogen abstraction from 1,2-Dihydro-2-methyl-2-phenyl-3-oxo-3H-indole-1-oxyl (nitroxide). In the former case the benzyl radical of the methylphenol gave the corresponding dimer and the alkylated hydroxylamine by coupling with the starting nitroxide. In the latter case only the 2,6-di-tert-butylbenzoquinone, the amine and the hydroxylamine corresponding to the starting nitroxide were obtained. In all other cases, in which the nitroxide was unable to give hydrogen abstraction from phenols, the phenoxy radicals were formed by lead dioxide oxidation of the corresponding phenols in the presence of the nitroxide. Except for 2,4,6-trimethylphenol, whose phenoxy radical formed with the nitroxide the alkylated hydroxylamine, all other phenoxy radicals reacted with the starting nitroxide giving ortho or para benzoquinones and the amine corresponding to the deoxygenated nitroxide. The structures of 1-[O-(3,5-di-tert-butyl-4-hydroxy)-benzyl]-1,2-dihydro-2-methyl-2-phenyl-3-ox o-3H-indole and of the 3,5,3',5'-tetra-tert-butylstilbene-4.4'-quinone, isolated by lead dioxide oxidation on 2,6-di-tert-butyl-4-methylphenol, were determined by X-ray analysis; their geometries are discussed in comparison with analogous compounds.