732-28-5Relevant academic research and scientific papers
Electron transfer between protonated and unprotonated phenoxyl radicals
Omura, Kanji
, p. 858 - 867 (2008/09/19)
(Chemical Equation Presented) The reaction of phenoxyl radicals with acids is investigated. 2,4,6-Tri-tert-butylphenoxyl radical (13), a persistent radical, deteriorates in MeOH/PhH in the presence of an acid yielding 4-methoxycyclohexa-2,5-dienone 18a and the parent phenol (14). The reaction is facilitated by a strong acid. Treatment of 2,6-di-tert-butyl-4-methylphenoxyl radical (2), a short-lived radical, generated by dissociation of its dimer, with an acid in MeOH provides 4-methoxycyclohexa-2,5-dienone 4 and the products from disproportionation of 2 including the parent phenol (3). A strong acid in a high concentration favors the formation of 4 while the yield of 3 is always kept high. Oxidation of the parent phenol (33) with PbO2 to generate transient 2,6-di-tert-butylphenoxyl radical (35) in AcOH/H2O containing an added acid provides eventually p-benzoquinone 39 and 4,4′-diphenoquinone 42, the product from dimerization of 35. A strong acid in a high concentration favors the formation of 39. These results suggest that a phenoxyl radical is protonated by an acid and electron transfer takes place from another phenoxyl radical to the protonated phenoxyl radical, thus generating the phenoxyl cation, which can add an oxygen nucleophile, and the phenol (eq 5). The electron transfer is a fast reaction.
QSAR for the cytotoxicity of 2-alkyl or 2,6-dialkyl, 4-X-phenols: The nature of the radical reaction
Selassie, Cynthia D.,Verma, Rajeshwar P.,Kapur, Sanjay,Shusterman, Alan J.,Hansch, Corwin
, p. 1112 - 1117 (2007/10/03)
In a continuation of studies on the radical mediated toxicity of phenols to leukemia cells, a set of di- and tri-substituted phenols with mostly alkyl substituents in the ortho position were examined. These analogs are similar in structure to the commercial antioxidants BHA and BHT. A QSAR analysis of their growth inhibitory constants led to the formulation of this simple but unusual equation based on 18 congeners: log 1/C = -0.47Es-2 + 2.42RR + 2.43; r3 = 0.934 ES-2 is the Taft steric parameter for the larger of the two ortho substituents while ER is Otsu's radical parameter, which was originally defined to correlate radical reactions.
Rapid conversion of phenols to p-benzoquinones under acidic conditions with lead dioxide
Omura, Kanji
, p. 1145 - 1148 (2007/10/03)
Treatment of 4-unsubstituted and 4-halogenated phenols with PbO2 and 70% HClO4 in AcOH afforded the corresponding p-benzoquinones in fair to high yields. The oxidation of 4-substituted 2,6-di-tertbutylphenols 6 with PbO2 and 70% HClO4 in acetone gave 2,6-di-tert-butyl-p-benzoquinone (2).
120. Stereoselective Ring Opening of Electronically Excited Cyclohexa-2,4-dienones: Cause and Effect
Quikert, Gerhard,Scherer, Stefan,Reichert, Dietmar,Nestler, Hans-Peter,Wennemers, Helma,Ebel, Andreas,Urbahns, Klaus,Wagner, Klaus,Michaelis, Klaus-Peter,Wiech, Gerhard,Prescher, Günter,Bronstert, Bernd,Freitag, Bernd-Jürgen,Wicke, Ilka,Lisch, Dietmar,Belik, Pavel,Crecelius, Thorsten,H?rstermann, Dirk,Zimmermann, Gottfried,Bats, Jan W.,Dürner, Gerd,Rehm, Dieter
, p. 1683 - 1772 (2007/10/03)
The two conformers of a cyclohexa-2,4-dienone with different substituents at C(6) on irradiation are believed to undergo ring opening stereospecifically affording a mixture of two configurationally isomeric diene-ketenes (and descendents thereof). Exceptions are generally found for those dienones with one C and one O substituent or even with two C substituents, if one of them carries a polar group at a site able to interact through space with the ring C=O group. In these cases, only one of the two anticipated diene-ketenes (and descendents thereof) is produced. A thorough investigation of the photochemistry of a series of structurally different cyclohexa-2,4-dienones on analytical as well as on preparative scale extends our mechanistic knowledge of the various routes from diene-ketenes into a variety of compound classes. Novel compound classes accessible to diene-ketenes are seven-membered carbocycles (by intramolecular aldolization of the zwitterion of appropriately substituted, transiently formed diene-(N,O)-ketene acetals) and βlactams (by Staudinger reaction).
Dienone tautomers of 4-alkoxy-2,6-di-terf-butylphenols
Omura, Kanji
, p. 7156 - 7161 (2007/10/03)
Generation and isolation of 4-alkoxycyclohexa-2,5-dienones 9, the tautomeric forms of the title phenols (10), is described. They are generated efficiently by the Ag ion mediated reaction of 4-bromocyclohexa-2,5-dienone 3b with simple alcohols, although they can be irreversibly isomerized into 10 under the reaction conditions. Crude materials with high amounts of 9 can be obtained by conducting the reaction with AgClO4 in the presence of Na2CO3 or with AgOCOCF3 and by interrupting the reaction shortly after the formation of 9 is complete. The AgOCOCF3 reaction produces labile 4-(trifluoroacetoxy)cyclohexa-2,5-dienone 11 also, the formation of which becomes significant as the alcohol becomes bulky. All of 9 prove to be very much susceptible to the prototropic rearrangement into 10 by catalysis with base, acid, or SiO2. Crude dienones 9 can be conveniently prepared directly from phenol 6 by treatment for a short time with Br2 in alcohols containing AgClO4 and Na2CO3. A one-pot synthesis from 6 of 4-oxyfunctionalized 2,6-di-tert-butylphenols, including 10, is also described.
Choice of Manganese(III) Complexes for the Synthesis of 4,4'-Biphenyldiols and 4,4'-Diphenoquinones
Nishino, Hiroshi,Nobuyuki, Itoh,Nagashima, Makiko,Kurosawa, Kazu
, p. 620 - 622 (2007/10/02)
2,6-Disubstituted phenols are oxidized with tris(2,4-pentanedionato)manganese(III), , in glacial acetic acid to give the corresponding 4,4'-biphenyldiols in high yields, whereas similar reactions using manganase(III) acetate, , instead of quantitatively yield the corresponding 4,4'-diphenoquinones.Cross-coupling reactions of 2,6-di-t-butylphenol and other substituted phenols afford the corresponding cross-coupled 4,4'-biphenyldiols and 4,4'-diphenoquinones together with oxidation products derived from them starting phenols themselves.The advantageous use of and Mn(OAc)3> in the ubiqitous phenol coupling reaction is discussed.
SYNTHESIS OF 4-ALKOXY- AND 4-ACYLOXY-2,6-DI-tert-BUTYLPHENOLS AND QUINOL ETHERS BASED ON THEM
Dobronravova, Z. A.,Meshcheryakov, V. I.,Prishchenko, Yu. E.,Gavrilov, L. D.,Vereshchagin, L. I.
, p. 910 - 914 (2007/10/02)
4-Alkoxy- and 4-acyloxy-2,6-di-tert-butylphenols were obtained by the alkylation and acylation of 2,6-di-tert-butyl-p-dihydroxybenzene.With quinone dioximes under oxidizing conditions the products form quinol ethers.
