The oxidation of p-substituted phenols with t-BuOOH in the presence of heteropolyacids was carried out. 4-t-Butylperoxy-2,5-cyclohexadien-1-ones were obtained in good yields by the oxidation of 2,4,6-trialkylsubstituted phenols in this oxidation system.
Cobalt Schiff base complexes [Co(SB)] catalyze the oxidation of anilines (1) with tert-butyl hydroperoxide to give nitrobenzenes 2 and 4-(tert-butylperoxy)-2,5-cyclohexadien-1-imine derivatives 3 in yield distributions depending on the substitution mode of the substrate. 4-Alkyl- and 4-aryl-2,6-di-tert-butylanilines gave mixtures of 2 and 3, where the higher the bulkiness of the 4-substituent, the higher the yield of 2. With 2,4,6-trimethylaniline, the ratio of oxidations of the nitrogen and C-4 atoms was almost the same; but a hydrolyzed product 5 of the imine was obtained. 2,4,6-Triphenylaniline gave only 2. Nitrobenzene derivatives were also obtained from 2,6-dialkylanilines and 4-substituted anilines. The catalytic activity of Co(SB) depended on the nature of the SB ligand: the formal potential E degrees and steric factors seem to affect the reaction rate. Kinetic studies showed that the key step may involve hydrogen abstraction from the aniline, presumably by t-BuO(.) generated from homolytic decomposition of initially formed Co-III(SB)(OO-t-Bu). A precursor of 2 was found to be the nitrosobenzene derivative.
Co(salen) catalyzed oxidation of 2,4,6-trisubstituted anilines with tert-butylhydroperoxide
Co(salen) catalyzed oxidation of 2,4,6-trisubstituted (preferentially 2,6-di-tert-butylated) anilines with tert-butylhydroperoxide gives 4-tert-butylperoxy-2,5-cyclohexadien-1-imine and nitrobenzene derivatives. The relative ratio of the products depends on the nature of the substituents in the substrate.
“A Jack of Trio”-robust one-pot metal free oxidative amination, azidation and peroxidation of phenols
containing quaternary carbon centres via aminative and azidative oxidative dearomatization of phenols. The same protocol has also been successfully employed to achieve oxidativeperoxidation of phenols. The simplest metal free reaction conditions delineate an easy breakthrough to the “Trio”- oxidative amination, azidation and peroxidation. An array of diverse polyfunctionalised heterocycles has been synthesized