- Kharasch reaction: Cu-catalyzed and non-Kharasch metal-free peroxidation of barbituric acids
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It was discovered that the Kharasch peroxidation of barbituric acids proceeds both with a Cu-catalyst and without a metal catalyst. Despite the presence of possible thermal-initiated side oxidation pathways, α-tert-butylperoxybarbiturates were selectively prepared from substituted barbituric acids and tert-butyl hydroperoxide.
- Bityukov, Oleg V.,Vil, Vera A.,Sazonov, George K.,Kirillov, Andrey S.,Lukashin, Nikita V.,Nikishin, Gennady I.,Terent'ev, Alexander O.
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- Trapping Free Radicals Formed in the Reaction of Ozone with Simple Olefins Using 2,6-Di-tert-butyl-4-cresol (BHT)
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Free radicals are detected from the ozonation of a series of olefins using a BHT trapping technique.We have determined the structure of the adduct when 3,3-dimethylbutene (tert-butylethylene) is ozonated at -78 deg C and then warmed in the presence of BHT.The adduct can be rationalized as arising from trapping tert-butylperoxyl radicals by BHT to give 2,6-di-tert-butyl-4-(tert-butylperoxy)-4-methyl-2,5-cyclohexadienone (1).
- Pryor, William A.,Gu, Jen-tau,Church, Daniel F.
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- Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes
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A general catalytic methodology for the synthesis of pyrazolines from α-diazo compounds and conjugated alkenes is reported. The direct hydrogen atom transfer (HAT) process of α-diazo compounds promoted by the tert-butylperoxy radical generates electrophilic diazomethyl radicals, thereby reversing the reactivity of the carbon atom attached with the diazo group. The regiocontrolled addition of diazomethyl radicals to carbon-carbon double bonds followed by intramolecular ring closure on the terminal diazo nitrogen and tautomerization affords a diverse set of pyrazolines in good yields with excellent regioselectivity. This strategy overcomes the limitations of electron-deficient alkenes in traditional dipolar [3+2]-cycloaddition of α-diazo compounds with alkenes. Furthermore, the straightforward formation of the diazomethyl radicals provides umpolung reactivity, thus opening new opportunities for the versatile transformations of diazo compounds.
- Dong, Kuiyong,Doyle, Michael P.,Su, Yong-Liang,Zheng, Haifeng
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- Iodine-Initiated Dioxygenation of Aryl Alkenes Using tert-Butylhydroperoxides and Water: A Route to Vicinal Diols and Bisperoxides
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An environment-friendly and efficient dioxygenation of aryl alkenes for the construction of vicinal diols has been developed in water with iodine as the catalyst and tert-butylhydroperoxides (TBHPs) as the oxidant. The protocol was efficient, sustainable, and operationally simple. Detailed mechanistic studies indicated that one of the hydroxyl groups is derived from water and the other one is derived from TBHP. Additionally, the bisperoxides could be obtained in good yields with iodine as the catalyst, Na2CO3 as the additive, and propylene carbonate as the solvent, instead.
- Gao, Xiaofang,Lin, Jiani,Zhang, Li,Lou, Xinyao,Guo, Guanghui,Peng, Na,Xu, Huan,Liu, Yi
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p. 15469 - 15480
(2021/11/16)
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- Peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones
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The sp3-C-H peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones was achieved under mild and simple catalyst-free reaction conditions. A range of biologically important alkylated benzoxazinone peroxides are synthesized in high yield with a good functional group tolerance. The C(sp3)-OO bond was constructed efficiently and could be further converted into C(sp3)-C(sp3), C(sp3)-C(sp2), C(sp3)-C(sp), C-P and CO bonds by late-stage functional group transformations.
- Bao, Xiazhen,Huo, Congde,Wang, Jiayuan,Wang, Jie
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p. 3895 - 3898
(2020/04/15)
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- Table salt as a catalyst for the oxidation of aromatic alcohols and amines to acids and imines in aqueous medium: Effectively carrying out oxidation reactions in sea water
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A simple, efficient, sustainable and economical method for the oxidation of alcohols and amines has been developed based on chloride, a sea abundant anionic catalyst for the practical synthesis of a wide range of carboxylic acids, ketones and imines. Oxidation of aromatic alcohols was carried out using NaCl (20 mol%) as the catalyst, NaOH (50 mol%) and aq. TBHP (4 equiv.) as the oxidant in 55-92% isolated yields. Oxidation of aromatic amines to imines was achieved by using only 20 mol% of NaCl and aq. TBHP (4 equiv.) in 32-93% isolated yields. The chlorine species formed during the reaction as the active oxidation catalyst has been identified as ClO2- for alcohols and ClO-/ClO2- for amines by control experiments. This method is mostly free from chromatographic purification, which makes it suitable for large-scale synthesis. We have scaled up to 30 gram scale the synthesis of carboxylic acids and imines in good yields and have also carried out efficiently this new method using filtered sea water as the solvent and catalyst.
- Hazra, Susanta,Kushawaha, Ajay Kishor,Yadav, Deepak,Dolui, Pritam,Deb, Mayukh,Elias, Anil J.
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p. 1929 - 1934
(2019/04/29)
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- Ammonium hypoiodite-catalyzed peroxidative dearomatization of phenols
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Here, we report the first transition metal-free peroxidative dearomatization of phenols using hypoiodite catalysis with TBHP. Hypoiodite salts are generated in situ from the corresponding quaternary ammonium iodides in the presence of TBHP, and the oxidat
- Uyanik, Muhammet,Nishioka, Kohei,Ishihara, Kazuaki
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p. 1132 - 1147
(2019/12/11)
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- Dirhodium-catalyzed phenol and aniline oxidations with T-HYDRO. Substrate scope and mechanism of oxidation
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Dirhodium caprolactamate, Rh2(cap)4, is a very efficient catalyst for the generation of the tert-butylperoxy radical from tert-butyl hydroperoxide, and the tert-butylperoxy radical is a highly effective oxidant for phenols and anilines. These reactions are performed with 70% aqueous tert-butyl hydroperoxide using dirhodium caprolactamate in amounts as low as 0.01 mol % to oxidize para-substituted phenols to 4-(tert-butyldioxy) cyclohexadienones. Although these transformations have normally been performed in halocarbon solvents, there is a significant rate enhancement when Rh 2(cap)4-catalyzed phenol oxidations are performed in toluene or chlorobenzene. Electron-rich and electron-poor phenolic substrates undergo selective oxidation in good to excellent yields, but steric influences from bulky para substituents force oxidation onto the ortho position resulting in ortho-quinones. Comparative results with RuCl2(PPh 3)3 and CuI are provided, and mechanistic comparisons are made between these catalysts that are based on diastereoselectivity (reactions with estrone), regioselectivity (reactions with p-tert-butylphenol), and chemoselectivity in the formation of 4-(tert-butyldioxy)cyclohexadienones. The data obtained are consistent with hydrogen atom abstraction by the tert-butylperoxy radical followed by radical combination between the phenoxy radical and the tert-butylperoxy radical. Under similar reaction conditions, para-substituted anilines are oxidized to nitroarenes in good yield, presumably through the corresponding nitrosoarene, and primary amines are oxidized to carbonyl compounds by TBHP in the presence of catalytic amounts of Rh 2(cap)4.
- Ratnikov, Maxim O.,Farkas, Linda E.,McLaughlin, Emily C.,Chiou, Grace,Choi, Hojae,El-Khalafy, Sahar H.,Doyle, Michael P.
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experimental part
p. 2585 - 2593
(2011/06/19)
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- Titanium tetra-tert-butoxide-tert-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects
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The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C6H6, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)3TiOOBu-t and peroxytrioxide (t-BuO)3TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.
- Stepovik,Gulenova,Martynova,Mar'Yasin,Cherkasov
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p. 266 - 276
(2008/09/20)
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- Free-radical oxidation of para-substituted phenols by hypervalent tert-butylperoxiodane and tert-butyl hydroperoxide: Synthesis of 4-(tert-butylperoxy)-2,5-cyclohexadien-1-ones
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Oxidation of 4-alkylphenols 1 by 1-(tert-butylperoxy)-1,2-benziodoxol-3(1H)-one (2) in the presence of tert-butyl hydroperoxide affords selectively 4-(tert-butylperoxy)-2,5-cyclohexadien-1-ones 3 in good yields. Evidence for the involvement of free-radicals is reported.
- Ochiai, Masahito,Nakanishi, Akinobu,Yamada, Akiko
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p. 3927 - 3930
(2007/10/03)
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- The Oxidation of p-Substituted Phenols Using a t-Butyl Hydroperoxide-Heteropolyacid System
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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.
- Shimizu, Masao,Orita, Hideo,Hayakawa, Takashi,Watanabe, Yoshihito,Takehira, Katsuomi
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p. 2583 - 2584
(2007/10/02)
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