- Elemental Sulfur-Promoted Synthesis of 4-Hydroxybenzophenones from p-Quinone Methides under Metal-Free Condition
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Conventional methods for the general and efficient synthesis of 4-hydroxybenzo- phenones are extremely underdeveloped and limited. We herein report a challenging metal-free protocol to rapidly construct 4-hydroxybenzophenones from para-quinone methides (p-QMs) in DMSO in the presence of KOH using the inexpensive and readily available elemental sulfur as redox reagent. As an unprecedented method, this simple but efficient approach has excellent site specificity, green sustainability, excellent atomic economy, and broad functional group compatibilities. Mechanistic studies show that the novel reaction proceeds through a radical pathway.
- Li, Jingping,Wang, Kunpeng,Wu, Jiayi,Zhang, Haoxiang,Chen, Yan,Liu, Qinglei,Xu, Junju,Yi, Weiyin
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- Synthesis and Electrochemical Characteristics of 1-(3,5-Di-tert-butyl-4-hydroxyphenyl)alkyl(aryl)ketones and Radicals Obtained Therefrom
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1-(3,5-Di-tert-butyl-4-hydroxyphenyl)alkyl(aryl) ketones were prepared by treating 2,6-di-tert-butylphenol with aliphatic acids anhydrides and aroyl chlorides. The products were characterized with IR and 1H NMR spectra. Electrochemical reductio
- Monastyrskaya,Lyutkin,Gorbunov,Klimov
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p. 1409 - 1416
(2007/10/03)
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- Oxygenation of tert-Butylphenols with an Unsaturated Side Chain
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Base- and Co(Salpr)-promoted oxygenations of title compounds have been investigated with a view to obtaining further details concerning controlling factors in regioselective O2 incorporation into phenols.In the oxygenation of 4-alkenyl-2,6-di-tert-butyl- and 2-alkenyl-4,6-di-tert-butylphenols (1 and 12), the reactivity of the substrates and regioselectivity in the O2 incorporation may be interpreted in terms of electronic and steric effects of the alkenyl group as well as association effect of the countercation K+ on the transition-state 26 involving a charge transfer from the substrate anion to O2.With 4-alkynyl-2,6-di-tert-butylphenols (21), dioxygen was incorporated exclusively into the ortho position only when the phenolate anion was associated with K+.On the contrary, in the oxygenation of 1 and 12 with Co(Salpr), O2 was incorporated exclusively into the alkynyl side chain, regardless of the nature of the substituent, whereas with 21, O2 incorporation was distributed to both the ortho and the alkenyl side chain.The substituent-dependent regioselectivity in the oxygenation of phenols with Co(Salpr) is because the reactive phenolate-COIII species undergo homolysis to form phenoxy radical-CoII species reversibly, whose oxygenations compete with each other.When the oxygenation of the anionic species predominates, O2 is incorporated into the ortho position, whereas with the radical species the para and side chain oxydations predominate.
- Nishinaga, Akira,Iwasaki, Hitoshi,Shimizu, Tadashi,Toyoda, Yasushi,Matsuura, Teru
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p. 2257 - 2266
(2007/10/02)
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- Oxygenation of 2,6-Di-tert-butylphenols Bearing an Electron-Withdrawing Group in the 4-Position
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Co(Salpr), a five-coordinate cobalt (II) Schiff base complex, has been found to promote oxygenation of 2,6-di-tert-butylphenols bearing an electron-withdrawing group in the 4-position, leading to dioxygen incorporation exclusively into the ortho position of the phenols. 4-Acyl-2,6-di-tert-butylphenols (1) and their oxime O-methyl ethers (2) gave the corresponding 6-hydroperoxy-2,4-cyclohexadienone derivatives 3 and 4 quantitatively.Schiff bases 10 derived from 3,5-di-tert-butyl-4-hydroxybenzaldehyde, on the other hand, gave unexpected products, 1,2-dihydropyridine derivatives 11, cyclopentadienone 12, and epoxy-o-quinol 13.The structure of dihydropyridine 11a was determined by X-ray analysis. 2,6-Di-tert-butyl-4-cyanophenol gave 2,5-di-tert-butyl-3-cyano-2,4-cyclopentadienone in good yield.The formation of these products can be understood to result from intramolecular decomposition of the corresponding o-peroxidic intermediate.Phenols 2 were readily oxygenated in t-BuOH containing t-BuOK to give epoxy-o-quinols 7 in excellent yield, although the other phenols examined were unsusceptible to oxygenation under various basic conditions.
- Nishinaga, Akira,Shimizu, Tadashi,Toyoda, Yasushi,Matsuura, Teruo,Hirotsu, Ken
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p. 2278 - 2285
(2007/10/02)
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- INVESTIGATION OF COMPOUNDS WITH JUVENILE ACTIVITY. XV. SYNTHESIS OF 2,6-DI-TERT-BUTYL-4-ACYLPHENOLS
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A series of 2,6-di-tert-butyl-4-acylphenols, which inhibit the development of the mosquito larva, were synthesized.These compounds were obtained either by acylation of 2,6-di-tert-butylphenol with the chlorides of benzoic or phenylacetic acids or by the reaction of 3,5-di-tert-butyl-4-hydroxyphenyl bromomethyl ketone with thiols or amines.Apart from the new compounds, the highly active larvicide benzyl 3,5-di tert-butyl-4-hydroxythiobenzoate, used as a standard for biological tests, was synthesized.
- Sergovskaya, N. L.,Kornienko, N. I.,Shekhter, O. V.,Tsizin, Yu. S.
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p. 1910 - 1913
(2007/10/02)
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- OXYGENATION OF 2,6-DI-t-BUTYLPHENOLS BEARING ELECTRON-WITHDRAWING GROUP AT 4-POSITION MEDIATED BY CO(II)-SCHIFF BASE COMPLEX
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4-Acyl-2,6-di-t-butylphenols except 3,5-di-t-butyl-4-hydroxybenzaldehyde were oxygenated in the presence of Co(Salpr) exclusively at the ortho position to give the corresponding 3,5-di-t-butyl-6-hydroperoxy-2,4-cyclohexadienone derivatives in quantitative
- Nishinaga, A.,Shimizu, T.,Matsuura, T.
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p. 5293 - 5296
(2007/10/02)
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- Quinone Dehydrogenation. Oxidation of Benzylic Alcohols with 2,3-Dichloro-5,6-dicyanobenzoquinone
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2,3-Dichloro-5,6-dicyanobenzoquinone (DDQ) reacts with primary and secondary aryl-substituted alcohols under mild conditions in dioxane solution to give the corresponding carbonyl compounds in high yields.In contrast to other oxidants, DDQ can be applied advantageously for the oxidation of hydroxyaryl-substituted alcohols.A mechanism involving participation of the phenolic hydroxyl group in the dehydrogenation reaction is discussed.Oxidations of hydroxyaryl-substituted alcohols by DDQ in methanolsolution resulting in the formation of benzoquinones by loss of the hydroxyaryl side chain are interpreted in terms of phenol oxidation.An example of a pyridine-catalyzed Smiles rearrangement of an o-hydroxy-substituted diphenyl ether is reported.
- Becker, Hans-Dieter,Bjoerk, Anders,Adler, Erich
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p. 1596 - 1600
(2007/10/02)
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- Anti-inflammatory method
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Compounds in which 2,6-di(t-butyl)phenol is substituted in the 4 position by an optionally substituted benzoyl group have valuable pharmacological activity as anti-inflammatory agents.
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