- Oxovanadium(v)-catalyzed oxidative cross-coupling of enolates using O2as a terminal oxidant
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The oxovanadium(v)-catalyzed oxidative cross-coupling of enolates using O2 as a terminal oxidant is reported, where a boron enolate and a silyl enol ether were employed as enolates. The redox behavior of V(v/iv) in this reaction under O2 was investigated by ESR and 51V NMR experiments.
- Osafune, Yuma,Jin, Yuqing,Hirao, Toshikazu,Tobisu, Mamoru,Amaya, Toru
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supporting information
p. 11697 - 11700
(2020/10/19)
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- Synthesis of 1,4-Dicarbonyl Compounds by Visible-Light-Mediated Cross-Coupling Reactions of α-Chlorocarbonyls and Enol Acetates
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Herein, we report a protocol for visible-light-mediated radical coupling reactions of α-chloroketones and enol acetates to afford 1,4-dicarbonyl compounds, which are important precursors and intermediates in organic synthesis. The reaction involves photoredox-catalyzed activation of the α-chloroketone upon photoelectron transfer, carbon–chlorine bond cleavage, and coupling of the resulting radical with the carbon–carbon double bond of the enol acetate. This mild protocol has a wide substrate scope and moderate to good yields. (Figure presented.).
- Liu, Qiang,Wang, Rui-Guo,Song, Hong-Jian,Liu, Yu-Xiu,Wang, Qing-Min
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supporting information
p. 4391 - 4396
(2020/09/21)
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- Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones
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Due to their closely matched reactivity, the coupling of two dissimilar ketone enolates to form a 1,4-diketone remains a challenge in organic synthesis. We herein report that umpolung of a ketone trimethylsilyl enol ether (1 equiv) to form a discrete enol
- Parida, Keshaba N.,Pathe, Gulab K.,Maksymenko, Shimon,Szpilman, Alex M.
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p. 992 - 997
(2019/12/23)
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- Eosin Y as a Direct Hydrogen-Atom Transfer Photocatalyst for the Functionalization of C?H Bonds
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Eosin Y, a well-known economical alternative to metal catalysts in visible-light-driven single-electron transfer-based organic transformations, can behave as an effective direct hydrogen-atom transfer catalyst for C?H activation. Using the alkylation of C?H bonds with electron-deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y-based photocatalytic hydrogen-atom transfer strategy is promising for diverse functionalization of a wide range of native C?H bonds in a green and sustainable manner.
- Fan, Xuan-Zi,Rong, Jia-Wei,Wu, Hao-Lin,Zhou, Quan,Deng, Hong-Ping,Da Tan, Jin,Xue, Cheng-Wen,Wu, Li-Zhu,Tao, Hai-Rong,Wu, Jie
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supporting information
p. 8514 - 8518
(2018/07/14)
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- Selective intermolecular oxidative cross-coupling of enolates
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Selective intermolecular oxidative cross-coupling of enolates, which is a bond-forming reaction between carbanion equivalents, remains as an unsolved issue despite its potential utility for the direct synthesis of unsymmetrical 1,4-diones. The main difficulty derives from the unavoidable homo-coupling. Our strategy depends on the selective one-electron oxidation of one enolate to afford an electrophilic carbonyl α-radical species, followed by trapping with another enolate. The present study demonstrates the selective oxovanadium(V)-induced cross-coupling between boron and silyl enolates.
- Amaya, Toru,Maegawa, Yusuke,Masuda, Takaya,Osafune, Yuma,Hirao, Toshikazu
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p. 10072 - 10075
(2015/09/01)
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- Radical alkylations of alkyl halides and unactivated C-H bonds using vinyl triflates
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Radical alkylations of activated alkyl iodides and bromides were achieved using vinyl triflates in the presence of hexadimethyltin, whereas those of unactivated C-H bonds using vinyl triflates proceeded cleanly under tin-free conditions. Georg Thieme Verl
- Lee, Jin Young,Lim, Kyoung-Chan,Meng, Xiangjian,Kim, Sunggak
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experimental part
p. 1647 - 1650
(2010/09/04)
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- Ring-opening of tertiary cyclopropanols derived from β-diketones
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The ring-opening reaction of 1,2-disubstituted cyclopropanols, prepared from β-diketones, mediated by Cu(NO3)2, p-TsOH, and NaOH is reported. The Cu(II)-mediated ring-opening of cyclopropanols gave α-methylene-γ-diketones in good yie
- Li, Le-Zhen,Xiao, Bin,Guo, Qing-Xiang,Xue, Song
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p. 7762 - 7771
(2007/10/03)
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- Free radical ring expansion and chain extension of 1,3-diketones
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Free radical-promoted one carbon ring expansion and chain extension of 1,3-diketones including 1,3-diarylpropane-1,3-diones and 2-aroyl-3,4-dihydro-2H- naphalen-1-one to generate corresponding 1,4-diketones are described.
- Mu, Xue-Jun,Zou, Jian-Ping,Wang, Zhi-Tao,Zhang, Wei
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p. 4727 - 4729
(2007/10/03)
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- Cross-coupling reaction of α-chloroketones and organotin enolates catalyzed by zinc halides for synthesis of γ-diketones
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The reaction of tin enolates 1 with α-chloro- or bromoketones 2 gave γ-diketones (1,4-diketones) 3 catalyzed by zinc halides. In contrast to the exclusive formation of 1,4-diketones 3 under catalytic conditions, uncatalyzed reaction of 1 with 2 gave aldol-type products 4 through carbonyl attack. NMR study indicates that the catalyzed reaction includes precondensation between tin enolates and α-haloketones providing an aldol-type species and their rearrangement of the oxoalkyl group with leaving halogen to produce 1,4-diketones. The catalyst, zinc halides, plays an important role in each step. The carbonyl attack for precondensation is accelerated by the catalyst as Lewis acid and the intermediate zincate promotes the rearrangement by releasing oxygen and bonding with halogen. Various types of tin enolates and α-chloro and bromoketones were applied to the zinc-catalyzed cross-coupling. On the other hand, the allylic halides, which have no carbonyl moiety, were inert to the zinc-catalyzed coupling with tin enolates. The copper halides showed high catalytic activity for the coupling between tin enolates 1 and organic halides 7 to give γ,δ-unsaturated ketones 8 and/or 9. The reaction with even chlorides proceeded effectively by the catalytic system.
- Yasuda, Makoto,Tsuji, Shoki,Shigeyoshi, Yusuke,Baba, Akio
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p. 7440 - 7447
(2007/10/03)
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- Preparations of Furans from α-Bromo Ketones and Enol Ethers Catalyzed by a Rhenium(I) Nitrogen Complex
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By the catalytic use of a rhenium(I) nitrogen complex, [ReCl(N2)(PMe2Ph)4], α-keto radicals are generated from α-bromo ketones and react with vinyl ethers and silyl enol ethers intermolecularly. Various substituted furans, including tetrasubstituted furans such as furoguaiacin, are prepared by this method.
- Koga, Yuji,Kusama, Hiroyuki,Narasaka, Koichi
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p. 475 - 482
(2007/10/03)
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- A new simple synthesis of aryl-substituted 1,4-diketones
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1,4-Diketones have been prepared by aldol condensation of methyl ketones with α-bromo ketones in the presence of tert-butoxymagnesium or diethylamido magnesium bromide and subsequent rearrangement of the formed 4-bromo-3-hydroxy ketones under the action o
- Kel'in, Alexander V.,Kulinkovich, Oleg G.
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p. 330 - 332
(2007/10/03)
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- Oxidative Generation of α-Radicals of Carbonyl Compounds from the α-Stannyl Derivatives and Their Reactions with Electron-Rich Olefins
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The oxidation of α-tributylstannyl alkanoates with tetrabutylammonium hexanitratocerate(IV) generates α-radicals of the alkanoates by eliminating the stannylium ion.The thus-formed radicals react with various electron-rich olefinic compounds, such as silyl enol ethers, giving addition products in good yield.This method formally achieves selective cross coupling between alkanoates and ketones.
- Kohno, Yasushi,Narasaka, Koichi
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p. 322 - 329
(2007/10/02)
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- Radical and Ionic Reactions of (Benzoylmethyl)mercurials
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Photolysis of PhCOCH2HgCl or (PhCOCH2)2Hg yields benzoylmethyl radicals which can be trapped by anions such as Me2C=NO2-, RC(CO2Et)2-, RC(O-)=CH2 or by other electron-rich systems such as (RO)3P, N-methylpyrrole, enamines, or norbornene.Electron transfer from the adduct radicals to the mercurials yields PhCOCH2A from the anions A-, PhCOCH2P(O)(OR)2 from P(OR)3, and the phenacyl derivative from N-methylpyrrole or enamines.Easily oxidized anions such as PhCOCPh2- or PhC(CH3)=NO2- react with PhCOCH2* by electron transfer to yield the dimer derived from the anion.Addition of PhCOCH2* to norbornene yields a substituted 3-benzoylpropyl radical which cyclizes at the ortho position of the benzoyl group to give the α-tetralone derivative.
- Russell, Glen A.,Kulkarni, Shekhar V.,Khanna, Rajive K.
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p. 1080 - 1086
(2007/10/02)
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- The Addition Reaction of β-Keto Carboxylic Acids to Olefinic Compounds by the Use of Mn(III) Tris(2-pyridinecarboxylate) as an Oxidant
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Intermolecular addition reactions of radical species generated from β-keto carboxylic acids to olefinic compounds such as a silyl enol ether, a ketene dithioacetal and an enamine proceed selectively by the use of manganese(III) tris(2-pyridinecarboxylate) as an oxidant.
- Narasaka, Koichi,Miyoshi, Norikazu,Iwakura, Kazunori,Okauchi, Tatsuo
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p. 2169 - 2172
(2007/10/02)
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