69217-39-6Relevant articles and documents
Solvolysis of 4-halogeno-4-alkyl-2,6-di-tert-butylcyclohexa-2,5-dienones induced by positive halogen donors as electrophiles
Omura, Kanji
, p. 1386 - 1392 (2013/12/04)
Positive halogen donors such as N-iodosuccinimide (NIS) induce solvolysis of dienones 1, as model 4-halogenocyclohexa-2,5-dienones, in different hydroxylic solvents (ROH), yielding the 4-RO-cyclohexa-2,5-dienones (2). The rate of the solvolysis with NIS is highly dependent on the structure of ROH. The problem of such dependency is overcome by running the reaction in ROH diluted with MeCN, a polar aprotic solvent, in place of pure ROH; the rate of the reaction in the ROH-MeCN solvent mixture is almost independent of the structure (or the polarity) of ROH, and the reaction is completed faster or markedly faster than in neat ROH. The results suggest that the solvolysis rate is controlled by the polarity of the solvent system, although the hydrogen-bond acceptability of MeCN for dilution also accelerates the reaction. A mechanism for the solvolysis is proposed, involving electrophilic attack of a positive halogen donor at the halogen atom of 1, generating the 4-oxocyclohexa-2,5-dienyl cation intermediates (8) via the rate-limiting polar transition states. CSIRO 2013.
Oxidation of Phenols by Molecular Oxygen Catalysed by Transition Metal Complexes. Comparison between the Activity of Various Cobalt and Manganese Complexes and the Role of Peroxy Intermediates
Frostin-Rio, Maryvonne,Pujol, Daniele,Bied-Charreton, Claude,Perree-Fauvet, Martine,Gaudemer, Alain
, p. 1971 - 1980 (2007/10/02)
The oxidation reactions of hindered phenols by molecular oxygen catalysed by monomeric and polymeric cobalt-Schiff base complexes, cobalt and manganese porphyrins, and (pyridine)cobaloxime are described; the rate and selectivity of these reactions are very dependent on the catalyst and on the solvent.A new product has been isolated, 1,3,5-tri-t-butyl-4-oxocyclohexa-2,5-dienylperoxy(pyridine)cobaloxime, and was fully characterised by its elemental analysis and spectroscopic methods.The reactivity of peroxy compounds derived from 2,4,6-tri-t-butylphenol which are postulated as intermediates in the oxidation of this phenol has been studied.Thermal decomposition of 1,3,5-tri-t-butyl-4-oxocyclohexa-2,5-dienyl(pyridine)cobaloxime indicates that the formation of this complex from the phenol, O2, and (pyridine)cobaloxime(II) is reversible and that it is converted into 2,6-di-t-butyl-1,4-benzoquinone only in the presence of a proton source.The corresponding hydroperoxide is probably an intermediate in this transformation as its decomposition in the presence of the cobalt(II) or manganese(III) complexes yields the same final products as the overall oxidations.
Regioselective Formation of Peroxyquinolatocobalt(III) Complexes in the Oxygenation of 2,6-DI-t-butylphenols Schiff-base Complexes
Nishinaga, Akira,Tomita, Haruo,Nishizawa, Kanji,Matsuura, Teruo,Ooi, Shunichiro,Hirotsu, Ken
, p. 1504 - 1514 (2007/10/02)
The oxygenation of 2,6-di-t-butylphenols with five-co-ordinated cobalt(II) Schiff-base complexes in aprotic solvents, such as CH2Cl2, thf, and dmf (thf = tetrahydrofuran, dmf = dimethylformamide), has been found to result in regioselective formation of peroxyquinolatocobalt(III) complexes.The regioselectivity depends on the nature of the substituent at the 4-position of the phenol used: 4-alkyl-2,6-di-t-butylphenols(1) afford peroxy-p-quinolatocobalt(III) complexes, whereas peroxy-o-quinolato-complexes are formed from 4-aryl-2,6-di-t-butyl-phenols (4).The initiation of the oxygenation is hydrogen abstraction by superoxocobalt(III) species from the phenols to give the corresponding phenoxy-radicals (10).Rapid reduction of (10) with cobalt(II) species follows giving rise to a phenolatocobalt(III) complex intermediate, within which dioxygen is incorporated.The regioselectivity of the oxygenation is attributable to the formation of the phenolatocobalt(III) complex intermediate.Crystals of the peroxy-p-quinolatocobalt(III) complex (2a) are orthorombic, space group P212121, with a = 33.749(11), b = 11.844(5), c = 9.329(4) Angstroem, and Z = 4.The crystal structure has been refined from 3 018 diffractometer data to R = 0.067.
