- Radical Benzylation of Quinones via C-H Abstraction
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Herein we report the development of radical benzylation reactions of quinones using Selectfluor and catalytic Ag(I) initiators. The reaction is believed to proceed via a C-H abstraction mechanism after Ag(I)-mediated reduction of Selectfluor. This reaction occurs under mild conditions and is effective for a variety of quinones and radical precursors bearing primary benzylic carbons. The use of preformed Ag(4-OMePy)2NO3 as a catalyst proved effective in improving the reaction efficiency by reducing unwanted degradation pathways available to Selectfluor.
- Galloway, Jordan D.,Mai, Duy N.,Baxter, Ryan D.
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p. 12131 - 12137
(2019/10/02)
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- Copper-Catalyzed Oxidative C(sp3)?H/N?H Cross-Coupling of Hydrocarbons with P(O)?NH Compounds: the Accelerating Effect Induced by Carboxylic Acid Coproduct
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An chelation-assisted oxidative C(sp3)?H/N?H cross coupling of hydrocarbons with P(O)?NH compounds using copper acetate as catalyst is described. The results of kinetic experiments, mechanistic studies and DFT calculations demonstrate the importance of acetic acid coproduct as an additive for promoting the formation of intermediate bis((diphenylphosphoryl)(quinolin-8-yl)amino)copper (6), and consequently accelerating the construction of C(sp3)?N bond. The reaction proceeded efficiently with a wide array of hydrocarbons and P(O)?NH compounds, and the rate acceleration induced by the acetic acid coproduct have been repeatedly proven. Furthermore, the efficiency of small-scale reaction could be retained upon gram-scale synthesis in a continuous manner. (Figure presented.).
- Lei, Jian,Yang, Yincai,Peng, Lingteng,Wu, Lesong,Peng, Ping,Qiu, Renhua,Chen, Yi,Au, Chak-Tong,Yin, Shuang-Feng
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supporting information
p. 1689 - 1696
(2019/03/07)
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- Cetyltrimethyl ammonium bromide catalysed oxidative cross dehydrogenative coupling of benzylic C(sp3)-H bonds in methylarenes with P(O)-OH compounds
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An efficient metal-free method for the synthesis of organophosphorus compounds via oxidative cross dehydrogenative coupling of benzylic C(sp3)-H bonds in methylarenes with P(O)-OH compounds catalysed by cetyltrimethyl ammonium bromide (CTAB) is
- Li, Hang,Lei, Jian,Liu, Yongping,Chen, Yi,Au, Chak-Tong,Yin, Shuang-Feng
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supporting information
p. 302 - 308
(2019/01/10)
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- Synthesis and cytotoxicity studies of newly designed benzyl-hydroquinone derivatives
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Abstract: A series of new benzyl-substituted hydroquinones has been prepared by short and flexible routes. Such molecules are simplified analogs of bioactive natural terpenes. Preliminary studies have established, for some of these derivatives, promising cytotoxicity data against human carcinoma cancer cell lines.
- Tasseau, Olivier,Mosset, Paul,Barillé-Nion, Sophie,Gautier, Fabien,Juin, Philippe,Levoin, Nicolas,Amireddy, Niharika,Kalivendi, Shasi,Grée, René
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p. 1050 - 1065
(2018/02/14)
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- Quinone C-H Alkylations via Oxidative Radical Processes
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A brief survey of radical additions to quinones is reported. Carboxylic acids, aldehydes, and unprotected amino acids are compared as alkyl radical precursors for the mono- or bis- C-H alkylation of several quinones. Two methods for radical initiation are discussed comparing inorganic persulfates and Selectfluor as stoichiometric oxidants. Kinetic analysis reveals dramatic differences in the rate of radical initiation depending on the identity of the radical precursor and oxidant. Synthetic strategies for efficiently producing alkyl-quinones are discussed in the context of selecting optimum radical precursors and initiators depending on quinone identity and functional groups present.
- Hamsath, Akil,Galloway, Jordan D.,Baxter, Ryan D.
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p. 2915 - 2923
(2018/06/12)
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- Ruthenium-catalyzed oxidative dearomatization of phenols to 4-(tert-butylperoxy)cyclohexadienones: Synthesis of 2-substituted quinones from p-substituted phenols
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The ruthenium-catalyzed oxidation of phenols with tert-butylhydroperoxide efficiently gives the corresponding 4-(tert-butylperoxy)cyclohexadienones. The oxidation proceeds selectively because of ruthenium's ability for rapid single-electron transfer. This biomimetic oxidation reaction is highly useful to obtain the metabolic compounds desired for confirming the safety of medicines and related compounds. Typically, the first metabolic compound of the female hormone estrone is readily obtained by this biomimetic oxidation reaction. The resulting 4-(tert-butylperoxy)cyclohexadienones are versatile synthetic intermediates, which can be transformed into 2-substituted 1,4-benzoquinones by treatment with acid catalysts. Acid-promoted rearrangement followed by a Diels-Alder reaction provides a new strategy for the synthesis of fused cyclic compounds, such as naphthoquinone and anthraquinone derivatives, from readily available phenols. The nonnatural 1,4-diacetoxy steroidal skeleton is obtained by the oxidation of estrone followed by zinc-mediated migration. Vitamin K 3 is synthesized selectively from p-cresol in an overall 79 % yield in 4 steps, and the synthesis includes the ruthenium-catalyzed oxidation.
- Murahashi, Shun-Ichi,Miyaguchi, Noriko,Noda, Shinji,Naota, Takeshi,Fujii, Akiko,Inubushi, Yasutaka,Komiya, Naruyoshi
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p. 5355 - 5365
(2011/11/14)
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- Synthesis of 2-substituted quinones, vitamin K3, and vitamin K1 from p-cresol. BF3·OEt2-catalyzed methyl migration of 4-tert-butyldioxycyclohexadienones
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BF3·OEt2-catalyzed methyl group migration of 4-methyl-4-tert-butyldioxycyclohexadienone, which is obtained by ruthenium-catalyzed oxidation of p-cresol with tert-butyl hydroperoxide, in hexafluoro-2-propanol/toluene gave toluquinone efficiently. The reaction can be applied to the regio-selective short-step syntheses of vitamin K3 and vitamin K1 from p-cresol.
- Murahashi, Shun-Ichi,Fujii, Akiko,Inubushi, Yasutaka,Komiya, Naruyoshi
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scheme or table
p. 2339 - 2341
(2010/05/19)
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- Acid-induced rearrangement reactions of reduced benzoquinone cyclopentadiene cycloadducts
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Several Diels-Alder adducts between benzoquinones and cyclopentadiene were reduced to the corresponding diols 7a-c and 11. Treatment of these diols with strong acid triggered a skeletal rearrangement reaction resulting in compounds 8a-c and 12 that contain a 4,8-methanoazulene substructure. In addition, a dyotropic-like rearrangement of the tetracyclic lactone 13 to the spirolactone 18 was observed. Five of the structures were supported by X-ray analysis.
- Eipert, Martin,Maichle-Moessmer, Caecilia,Maier, Martin E.
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p. 8692 - 8695
(2007/10/03)
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- A new synthetic route to substituted quinones by radical-mediated coupling of organotellurium compounds with quinones
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Carbon-centered radicals generated from the corresponding organotellurium compounds react with a variety of quinones under photo-thermal conditions to give the monoaddition product in moderate to excellent yield. The reaction can be used for the synthesis of polyprenyl quinoid natural products and C-glycosides.
- Yamago, Shigeru,Hashidume, Masahiro,Yoshida, Jun-Ichi
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p. 6805 - 6813
(2007/10/03)
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- A Simple and Efficient Procedure for the Preparation of p-Quinols by Hypervalent Iodine Oxidation of Phenols and Phenol Tripropylsilyl Ethers
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Oxidation of para-substituted phenols with benzene (BTIB) in aqueous acetonitrile at 0 deg C gives p-quinols in moderate to good yields; higher yields are obtained when tripropylsilyl ethers of phenols are used.
- McKillop, Alexander,McLaren, Lee,Taylor, Richard J. K.
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p. 2047 - 2048
(2007/10/02)
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- Benzoquinones and Related Compounds. Part 5. Nuclear Magnetic Resonance Study of the Conformation in Solution of Some Diels-Alder Adducts between 1,4-Benzoquinones and Cyclopentadiene
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The Diels-Alder reaction of cyclopentadiene with the 5,6-double bond of benzyl-, α-hydroxybenzyl-, and α-acetoxybenzyl-1,4-benzoquinone, and of 1-hydroxy-1-phenyl-, 1-phenyl-, and 1-hydroxy-indan-4,7-quinone gives in each case a pair of diastereoisomeric endo adducts.For those which carry a phenyl group, the chemical shift of one of the norbornene olefinic protons in one member of each pair is significantly different from that of the corresponding proton in the other member.The conformational significance of this effect is discussed.Proton longitudinal relaxation and nuclear Overhauser relaxation techniques are used to show that the cyclopentadiene endo monoadducts of 1,4-benzoquinone and α-hydroxybenzyl-1,4-benzoquinone prefer to adopt an 'open' rather than a 'closed' conformation.
- Al-Hamdany, Raad,Bruce, J. Malcolm,Heatley, Frank,Khalafy, Jabbar
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p. 1395 - 1400
(2007/10/02)
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- ELECTRON-TRANSFER PROCESSES BY PEROXYDISULPHATE: HOMOLYTIC BENZYLATION OF QUINONES BY ALKYLARENES AND REACTIONS OF AROMATIC RADICAL CATIONS WITH AROMATICS
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Quinones are monobenzylated in good to satisfactory yields by alkylarenes and the Ag(+)/S2O8(2-) couple under two-phase conditions.Under homogeneous conditions polybenzylation can be obtained.The polar effect of the aromatic substrate substituents in the ring and in the side chain is discussed on the basis of the intermediate aromatic radical cation reactivity in side-chain proton loss and electrophilic aromatic addition.The high efficiency of the quinone system in trapping benzylic radicals, coming from the aromatic radical cations, is ascribed to a charge-transfer transition state.
- Citterio, Attilio
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p. 253 - 258
(2007/10/02)
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- Organocopper Chemistry of Quinone Bisketals. Application to the Synthaais of Isoprenoid Quinone Systems
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The reactions of organocuprates of 1,4-benzoquinone and 1,4-naphthoquinone bisketals are reported.These reagents, formed from the corresponding lithium reagent, cuprous iodide, and dimethyl sulfide react efficiently with allylic bromides (allyl, prenyl, geranyl, and phytyl), often with utilization of greater than one R group of the R2CuLi.Their reactions with acid chlorides and benzyl bromide proceed with acceptable efficiency, but they are unreactive toward a number of other substrates.The utility of this chemistry in the synthesis of menaquinone-2, phylloquinone,cymopol, and cymopol methyl ether is described.
- Chenard, Bertrand L.,Manning, Michael J.,Raynolds, Peter W.,Swenton, John S.
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p. 378 - 384
(2007/10/02)
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