- Electronic absorption spectra of some alkoxyl radicals. An experimental and theoretical study
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The visible and UV absorptions of a variety of alkoxyl radicals have been examined by experiment and theory. In most solvents, the tert-butoxyl radical shows only a weak "tail-end" absorption in the UV region of the spectrum and no absorption in the visib
- Avila, David V.,Ingold,Di Nardo, Ariel A.,Zerbetto, Francesco,Zgierski, Marek Z.,Lusztyk, Janusz
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- Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
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Different benzylic compounds were efficiently oxidized to the corresponding ketones with aqueous 70% tert-butyl hydroperoxide (TBHP) and the catalytic system composed of CuCl2.2H2O and 2,2'-biquinoline-4,4'-dicarboxylic acid dipotassium salt (BQC). The catalytic system CuCl2/BQC/TBHP allows obtaining high yields at room temperature under organic solvent-free conditions. The interest of this system lies in its cost effectiveness and its benign nature towards the environment. Benzylic tertbutylperoxy ethers and benzylic alcohols were observed and suggested as the reaction intermediates. Analysis of organic products by atomic absorption did not show any contamination with copper metal. In terms of efficiency, CuCl2/BQC system is comparable or superior to the most of the catalytic systems described in the literature and which are based on toxic organic solvent.
- Ajjou, Abdelaziz Nait,Rahman, Ateeq
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p. 165 - 174
(2020/04/15)
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- TBHP-promoted direct oxidation reaction of benzylic Csp3-H bonds to ketones
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A metal-free oxidation system employing tert-butyl hydroperoxide (TBHP) has been developed for selective oxidation of structurally diverse benzylic sp3 C-H bonds. This low-cost methodology allows for rapid generation of synthetically and biologically valued arylketones in good to excellent yields from readily available alkylarenes and diarylmethanes.
- Tan, Jiajing,Zheng, Tianyu,Yu, Yuqi,Xu, Kun
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p. 15176 - 15180
(2017/03/17)
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- Merging Photoredox with Br?nsted Acid Catalysis: The Cross-Dehydrogenative C?O Coupling for sp3 C?H Bond Peroxidation
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A photoredox and Br?nsted acid synergistically catalyzed cross-dehydrogenative C?O coupling reaction is developed in which isochroman peroxyacetals are formed through sp3 C?H bond peroxidation. The reported method is characterized by its extremely mild reaction conditions, excellent yields, and broad substrate scope. An oxocarbenium ion p-chlorobenzenesulfonate was speculated to be the reactive intermediate. The role of hemiacetals and oxygenated dimers on the effective stabilization of the oxocarbenium ion was investigated; the presence of acid appeared to establish equilibrium between hemiacetals and oxygenated dimers with the oxocarbenium ion pairs. The broad applicability of the method highlights the potential of the protocol for molecule synthesis.
- Xia, Qing,Wang, Qiang,Yan, Changcun,Dong, Jianyang,Song, Hongjian,Li, Ling,Liu, Yuxiu,Wang, Qingmin,Liu, Xiangming,Song, Haibin
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supporting information
p. 10871 - 10877
(2017/08/18)
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- Synthesis of aromatic ketones from aromatic compounds using vanadium-containing mesoporous silicates
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Aromatic ketones were synthesized from aromatic compounds via liquid-phase oxidation at 60 °C and 1 atm over vanadium-containing MCM-41 catalysts using a batch reactor. The catalysts were prepared by direct hydrothermal (4V-MCM-41) and wet impregnation (9V/MCM-41) methods. Their physico-chemical properties were determined with various characterization techniques. For the oxidations of all substrates in this work, 4 V-MCM-41 exhibits superior catalytic performance than 9 V/MCM-41 due to its larger values of unit cell parameter, BET surface area, and vanadium dispersion as well as stronger oxidation ability of vanadium-oxygen species. Apparently, the single site, isolated vanadium centers in 4V-MCM-41 possess much higher activity (based on the turnover number) than those containing more vanadium atoms in 9V/MCM-41. In addition, the substrate activities decrease in the order of diphenylmethane > fluorene > 9,10-dihydroanthracene > ethylbenzene ≥ 4-nitroethylbenzene, which are attributed to their distinct molecular structures.
- Chen, Chih-Wei,Ko, An-Nan
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p. 1104 - 1110,7
(2020/08/24)
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- A metal-free catalytic system for the oxidation of benzylic methylenes and primary amines under solvent-free conditions
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Iodine-pyridine-tert-butylhydroperoxide is developed as a green and efficient catalytic system for the oxidation of benzylic methylenes to ketones and primary amines to nitriles. The reaction conditions are quite mild and environmentally benign, no transition metals, organic solvents or hazard reagents being needed. The oxidation of benzylic methylenes gave the corresponding ketones in excellent yields with complete chemoselectivity, while the oxidation of primary amines was complete in several minutes, affording various nitriles in moderate to good yields.
- Zhang, Jintang,Wang, Zhentao,Wang, Ye,Wan, Changfeng,Zheng, Xiaoqi,Wang, Zhiyong
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scheme or table
p. 1973 - 1978
(2010/06/15)
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- Copper-catalyzed homolytic and heterolytic benzylic and allylic oxidation using tert-butyl hydroperoxide
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Allylic and benzylic alcohols were oxidized in good yields to the respective ketones by tert-butyl hydroperoxide (TBHP) in the presence of copper salts under phase-transfer catalysis conditions. This dehydrogenation was found to proceed via a heterolytic mechanism. CuCl2, CuCl, and even copper powder were equally facile as catalysts, as they were all transformed in situ to Cu(OH)Cl which was extracted into the organic phase by the phase-transfer catalyst (PTC). Deuterium labeling experiments evidenced the scission of the benzylic C-H bond in the rate-determining step. Nonproductive TBHP decomposition was not observed in the presence of the alcohol substrates. Conversely, the oxygenation of π-activated methylene groups in the same medium was found to be a free radical process, and the major products were the appropriate tert-butyl peroxides. Catalyst deactivation, solvent effects, and extraction effects are discussed. By applying Minisci's postulations concerning the relative reactivity of TBHP molecules towards tert-butoxyl radicals in protic and nonprotic environments, the coexistence of the homolytic and the heterolytic pathways can be explained. A complete reaction mechanism is proposed, wherein the free-radical oxidation obeys Kochi's mechanism, and the heterolytic dehydrogenation is based on either a high-valent CuIV=O species or a [Cu(OH)Cl]2 species.
- Rothenberg, Gadi,Feldberg, Liron,Wiener, Harold,Sasson, Yoel
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p. 2429 - 2434
(2007/10/03)
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- THE SELECTIVE FUNCTIONALIZATION OF SATURATED HYDROCARBONS. PART 28. THE ACTIVATION OF BENZYLIC METHYLENE GROUPS UNDER GOAGGIV AND GOAGGV CONDITIONS
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Under GoAggIV and GoAggV conditions, cyclohexadienes were oxidized to give aromatic products instead of ketones and alcohols.At the same time, anthracene was oxidized to give anthraquinone.Under GoAggIV and GoAggV conditions, xanthene, fluorene and diphenylmethane were oxidized to give the corresponding xanthone, fluorenone and benzophenone following two possible pathways: a) alkane to alkyl t-butylperoxide to ketone, and b) alkane to ketone, in which alkyl hydroperoxide, derived from oxygen, may be the reaction intermediate.Xanthyl azide was formed when sodium azide was added to the reaction mixture of xanthene under GoAggIV and GoAggV conditions.The reaction of triphenylmethane under GoAggV conditions gave triphenylmethyl t-butyl peroxide as the major product and hydroperoxide as the minor product.When TEMPO was added, triphenylmethyl hydroperoxide was the only product.
- Barton, Derek H. R.,Wang, Tie-Lin
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p. 1011 - 1032
(2007/10/02)
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- BIMETALLIC OXIDATION CATALYSTS: OXIDATIONS WITH TERT.BUTYLHYDROPEROXIDE MEDIATED BY BIS-(TRIBUTYLTIN OXIDE) DIOXOCHROMIUM (VI)
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At 40-80 deg C, t.BuOOH in conjunction with catalytic amounts of (n.Bu3SnO)2CrO2 1 oxidizes benzylic alcohols, methylenes in α-position of aryl, ethylenic or acetylenic groups into ketones, anthracene into anthraquinone, adamantane into adamantan-1-ol and 2-one.Except for propargylic oxidations, yields are generally superior to those obtained when CrO3 is used as catalyst instead of 1.
- Muzart, Jacques
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p. 2061 - 2068
(2007/10/02)
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- CHROMIUMVI COMPLEX CATALYZED BENZYLIC OXIDATIONS IN THE PRESENCE OF TERT.BUTYL HYDROPEROXIDE
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In using t.BuOOH and a small quantity of 2,4-dimethylpentane-2,4-diol cyclic chromate, benzylic methylene groups are oxidised into carbonyl functions; t.butylperoxy compounds are postulated as intermediates.
- Muzart, Jacques
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p. 3139 - 3142
(2007/10/02)
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