- Ir(NHC)-Catalyzed Synthesis of β-Alkylated Alcohols via Borrowing Hydrogen Strategy: Influence of Bimetallic Structure
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Multi N-heterocyclic carbene(NHC)-modified iridium catalysts were employed in the β-alkylation of alcohols; dimerization of primary alcohols (Guerbet reaction), cross-coupling of secondary and primary alcohols, and intramolecular cyclization of alcohols. Mechanistic studies of Guerbet reaction, including kinetic experiments, mass analysis, and density functional theory (DFT) calculation, were employed to explain the fast reaction promoted by bimetallic catalysts, and the dramatic reactivity increase of monometallic catalysts at the late stage of the reaction. (Figure presented.).
- Sung, Kihyuk,Lee, Mi-hyun,Cheong, Yeon-Joo,Kim, Yu Kwon,Yu, Sungju,Jang, Hye-Young
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supporting information
p. 3090 - 3097
(2021/05/10)
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- Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
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The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
- Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
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supporting information
p. 10005 - 10013
(2021/07/19)
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- Alkyne Trifunctionalization via Divergent Gold Catalysis: Combining π-Acid Activation, Vinyl-Gold Addition, and Redox Catalysis
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Here we report the first example of alkyne trifunctionalization through simultaneous construction of C-C, C-O, and C-N bonds via gold catalysis. With the assistance of a γ-keto directing group, sequential gold-catalyzed alkyne hydration, vinyl-gold nucleophilic addition, and gold(III) reductive elimination were achieved in one pot. Diazonium salts were identified as both electrophiles (N source) and oxidants (C source). Vinyl-gold(III) intermediates were revealed as effective nucleophiles toward diazonium, facilitating nucleophilic addition and reductive elimination with high efficiency. The rather comprehensive reaction sequence was achieved with excellent yields (up to 95%) and broad scope (>50 examples) under mild conditions (room temperature or 40 °C).
- Yuan, Teng,Tang, Qi,Shan, Chuan,Ye, Xiaohan,Wang, Jin,Zhao, Pengyi,Wojtas, Lukasz,Hadler, Nicholas,Chen, Hao,Shi, Xiaodong
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supporting information
p. 4074 - 4082
(2021/04/06)
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- Regioselective Crossed Aldol Reactions under Mild Conditions via Synergistic Gold-Iron Catalysis
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A synergistic gold-iron (Au-Fe) catalytic system was developed for sequential alkyne hydration and vinyl Au addition to aldehydes or ketones. Fe(acac)3 was identified as an essential co-catalyst in preventing vinyl Au protodeauration and facilitating nucleophilic additions. Effective C–C bond formation was achieved under mild conditions (room temperature) with excellent regioselectivity and high efficiency (1% [Au], up to 95% yields). The intramolecular reaction was also achieved, giving successful macrocyclization (16–31 ring sizes) with excellent yields (up to 90%, gram scale) without extended dilution (0.2 M), which highlights the great potential of this new crossed aldol strategy in challenging target molecule synthesis. Effective construction of the C–C bond is one of the most important tasks in organic synthesis. Whereas aldol condensation is a classic C–C bond-forming transformation, it requires other chemical promoters, such as strong base and reactive acidic catalysts. As a result, the overall transformation is limited in terms of ideal atom economy and environmentally friendly operation. With the discovery of a gold-iron (Au-Fe) synergistic catalysis system, here we describe a new approach to facilitating alkyne hydration and sequential vinyl Au addition to carbonyls. This approach gives the C–C bond-forming products in excellent yields, wide substrate scope, and great functional-group compatibility under mild conditions. This protocol can also be applied to macrocyclization without extended dilution. This C–C bond-forming strategy could facilitate challenging molecule synthesis in chemical, biological, and medicinal research. We report a synergistic gold-iron (Au-Fe) catalytic system to access vinyl Au reactivity by avoiding frequently occurring protodeauration. Fe(acac)3 was identified as an essential co-catalyst, facilitating vinyl Au addition to aldehydes. A broad substrate scope was obtained under mild conditions (room temperature) with excellent regioselectivity and high efficiency (1% [Au], up to 95% yields). This protocol offers a practical solution for achieving macrocyclization (16–31 ring sizes, up to 90%, gram scale) without extended dilution, highlighting the synthetic utility in complex molecular synthesis.
- Chen, Hao,Jean, Jonathan,Shan, Chuan,Shi, Xiaodong,Teng, Shun,Wang, Jin,Wojtas, Lukasz,Ye, Xiaohan,Yi, Yaping,Yuan, Teng,Zhao, Pengyi
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supporting information
p. 1420 - 1431
(2020/06/19)
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- Photo-mediated [1, 3]-Carbonyl shift of β-Ketocarbonyls
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An organic amine mediated photolytic [1,3]-benzoyl migration of β-benzoyl carbonyl compounds was reported. This migration was achieved by Norrish-Yang cyclization and retro-aldol reaction under black light (365 nm) or visible light irradiation. This photolytic protocol provides an alternative approach to the synthesis of 1,5-dicarbonyl compounds. By chiral primary amine catalysis, a kinetic resolution was also developed to afford enantioenriched 1,5-dicarbonyls.
- Zhang, Wenzhao,Li, Yao,Luo, Sanzhong
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- Nonclassical Mechanism in the Cyclodehydration of Diols Catalyzed by a Bifunctional Iridium Complex
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1,4- and 1,5-diols undergo cyclodehydration upon treatment with cationic N-heterocyclic carbene (NHC)–IrIII complexes to give tetrahydrofurans and tetrahydropyrans, respectively. The mechanism was investigated, and a metal-hydride-driven pathway was proposed for all substrates, except for very electron-rich ones. This contrasts with the well-established classical pathways that involve nucleophilic substitution.
- González Miera, Greco,Bermejo López, Aitor,Martínez-Castro, Elisa,Norrby, Per-Ola,Martín-Matute, Belén
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supporting information
p. 2631 - 2636
(2019/02/01)
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- Cyclopentane Formation from Flexible Precursors Using Samarium(II) Reagents
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Three efficient methods for five-membered ring carbocycle synthesis have been developed from simple starting materials using samarium(II) reagents. A Reformatsky aldol reaction proceeded efficiently with samarium(II) iodide using lithium bromide as an additive. A new intramolecular alkylation of a samarium enolate was realized with a pendant sulfonate ester leaving group. Pinacol cyclization of a simple diketone was also demonstrated giving a diol product in high stereoselectivity. A promising lead result has been established demonstrating enantioselectivity in a chiral ligand controlled Reformatsky aldol reaction.
- Aretz, Christopher D.,Escobedo, Humberto,Cowen, Bryan J.
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supporting information
p. 1880 - 1884
(2018/05/09)
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- Synthesis of Benzofurans from Ketones and 1,4-Benzoquinones
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Benzofuran derivatives can be synthesized through the sequential Michael addition and cyclization of 1,3-dicarbonyl compounds with 1,4-benzoquinones. However, ketones are rarely used in this reaction because of their low nucleophilicities. In this study, this problem was solved by utilizing triethyl orthoformate, which enabled the formation of a vinyl ethyl ether as an additive. As a result, the nucleophilicity of ketones increased. Many important 5-hydroxybenzofuran derivatives, which were not readily available by synthesis in the past, were also prepared via these newly established reactions. (Figure presented.) .
- Wu, Fengtian,Bai, Rongxian,Gu, Yanlong
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p. 2307 - 2316
(2016/07/29)
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- Bimetallic nanosized solids with acid and redox properties for catalytic activation of C-C and C-H bonds
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A new approach is presented to form self-supported bimetallic nanosized solids with acid and redox catalytic properties. They are water-, air- and H2-stable, and are able to activate demanding C-C and C-H reactions. A detailed mechanistic study on the formation of the Ag-Fe bimetallic system shows that a rapid redox-coupled sequence between Ag+, O2 (air) and Fe2+ occurs, giving monodisperse Ag nanoparticles supported by O-bridged diatomic Fe3+ triflimides. The system can be expanded to Ag nanoparticles embedded within a matrix of Cu2+, Bi3+ and Yb3+ triflimide.
- Cabrero-Antonino, Jose R.,Tejeda-Serrano, María,Quesada, Manuel,Vidal-Moya, Jose A.,Leyva-Pérez, Antonio,Corma, Avelino
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p. 689 - 696
(2016/12/28)
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- Palladium-Catalyzed Long-Range Deconjugative Isomerization of Highly Substituted α,β-Unsaturated Carbonyl Compounds
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The long-range deconjugative isomerization of a broad range of α,β-unsaturated amides, esters, and ketones by an in situ generated palladium hydride catalyst is described. This redox-economical process is triggered by a hydrometalation event and is thermodynamically driven by the refunctionalization of a primary or a secondary alcohol into an aldehyde or a ketone. Di-, tri-, and tetrasubstituted carbon-carbon double bonds react with similar efficiency; the system is tolerant toward a variety of functional groups, and olefin migration can be sustained over 30 carbon atoms. The refunctionalized products are usually isolated in good to excellent yield. Mechanistic investigations are in support of a chain-walking process consisting of repeated migratory insertions and β-H eliminations. The bidirectionality of the isomerization reaction was established by isotopic labeling experiments using a substrate with a double bond isolated from both terminal functions. The palladium hydride was also found to be directly involved in the product-forming tautomerization step. The ambiphilic character of the in situ generated [Pd-H] was demonstrated using isomeric trisubstituted α,β-unsaturated esters. Finally, the high levels of enantioselectivity obtained in the isomerization of a small set of α-substituted α,β-unsaturated ketones augur well for the successful development of an enantioselective version of this unconventional isomerization.
- Lin, Luqing,Romano, Ciro,Mazet, Clément
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supporting information
p. 10344 - 10350
(2016/08/31)
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- Selective Alkenylation and Hydroalkenylation of Enol Phosphates through Direct C-H Functionalization
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An efficient and selective Rh-catalyzed direct C-H functionalization reaction of enol phosphates was developed. The method is applicable to a variety of coupling partners, including activated alkenes, alkynes, and allenes, and leads to the formation of various valuable alkenylated and hydroalkenylated enol phosphates through the action of the phosphate directing group. The versatility and utility of the coupling products were demonstrated through further transformations into synthetically useful building blocks. P points the way: A direct C-H functionalization of enol phosphates was developed. The method is applicable to a variety of coupling partners, including activated alkenes, alkynes, and allenes, and it leads to the formation of alkenylated and hydroalkenylated enol phosphates through the action of the phosphate directing group. The utility of the coupling products are demonstrated by further transformations into synthetically useful building blocks.
- Hu, Xu-Hong,Yang, Xiao-Fei,Loh, Teck-Peng
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p. 15535 - 15539
(2016/01/26)
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- Synthesis and structures of air-stable binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate and their catalytic application in C-C bond-forming reactions
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The two air-stable m2-hydroxy-bridged binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate complexes were successfully synthesized. The high catalytic activity and recyclability of these complexes were exemplified for various carbon-carbon bond formation reactions. Compared with our previously reported hafnocene perfluorooctanesulfonate, these complexes show stronger Lewis acidity and better catalytic activity, and should find broad applications in organic synthesis.
- Li, Ningbo,Zhang, Xiaohong,Xu, Xinhua,Chen, Yun,Qiu, Renhua,Chen, Jinyang,Wang, Xie,Yin, Shuang-Feng
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supporting information
p. 2430 - 2440
(2013/10/01)
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- Regio- and stereoselective monoamination of diketones without protecting groups
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Hitting the right target: Differentiation between two keto moieties was accomplished by a regio- and enantioselective bioamination employing ω-transaminases. Using 1,5-diketones as substrates gave access to the optically pure 2,6-disubstituted piperidine scaffold. The approach allowed the shortest synthesis of the alkaloid dihydropinidine, as well as its enantiomer, by choosing an appropriate ω-transaminase. Copyright
- Simon, Robert C.,Grischek, Barbara,Zepeck, Ferdinand,Steinreiber, Andreas,Belaj, Ferdinand,Kroutil, Wolfgang
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supporting information; experimental part
p. 6713 - 6716
(2012/09/22)
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- Manganese-catalyzed direct oxidation of methyl ethers to ketones
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Direct C-H oxidation of alkyl ethers into ketones was achieved using 0.1 mol % of MnCl2 and 4, 4′, 4″-tri(tert-butyl)-2, 2′:6′, 2″-terpyridine (tBu-terpy) in the presence of mCPBA. Conversion of methyl ethers into ketones was particularly efficient and chemoselective. Electron-deficient oxygen functionalities survived under the reaction conditions. The present method broadens the utility of methyl ethers as stable protective groups for hydroxy functionalities and as precursors to carbonyl compounds. (Chemical equation presented).
- Kamijo, Shin,Amaoka, Yuuki,Inoue, Masayuki
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supporting information; experimental part
p. 486 - 489
(2010/09/04)
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- Unified oxidation protocol for the synthesis of carbonyl compounds using a manganese catalyst
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We have developed a unified protocol for the oxidation of ethers, benzylic compounds, and alcohols to carbonyl compounds. The protocol uses catalytic amounts of manganese(II) chloride tetrahydrate and tri(t-butyl)-2,2':6',2Prime;- terpyridine in combination with a stoichiometric amount of either m-chloroperbenzoic acid (MCPBA) or potassium hydrogen peroxysulfate (KHSO 5). A reagent system consisting of the Mn catalyst and MCPBA permitted the chemoselective sp3 C-H oxidation of alkyl ethers and benzylic compounds to generate the corresponding ketones. Alternatively, the water-soluble inorganic salt KHSO5 in combination with the Mn catalyst was used to oxidize alcohols to ketones or carboxylic acids. Importantly, the Mn catalyst/KHSO5 system eliminates technical difficulties associated with the isolation of carboxylic acid products. All the oxidations presented in this feature article proceed at sup-ambient temperature in an aerobic atmosphere, and can therefore be used in practical syntheses of complex organic molecules. Georg Thieme Verlag Stuttgart · New York.
- Kamijo, Shin,Amaoka, Yuuki,Inoue, Masayuki
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experimental part
p. 2475 - 2489
(2010/09/06)
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- Unexpected TiIII/Mn-promoted pinacol coupling of ketones
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Titanocene(III) chemistry has emerged in the last decades as an indispensable tool in C-C bond-forming reactions. In this context, pinacol and related reactions allow the stereoselective synthesis of vicinal diols. In this work, we present new applications of these reactions using as starting materials aromatic ketones. Simple and smooth reaction conditions have been developed and have been applied for inter- and intramolecular processes. We also describe that although Cp2TiCl is usually used as a monoelectronic reducing agent, it can be also used as an efficient Lewis acid.
- Paradas, Miguel,Campana, Araceli G.,Estevez, Rosa E.,De Cienfuegos, Luis Alvarez,Jimenez, Tania,Robles, Rafael,Cuerva, Juan M.,Oltra, J. Enrique
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supporting information; experimental part
p. 3616 - 3619
(2009/09/06)
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- Pd(0) or Pd(II)-catalyzed ring-opening reactions of benzylidene- and alkylidenecyclopropyl ketones and aldehydes
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Pd(0) catalyzed reactions of methylenecyclopropyl carbonyl compounds afforded a convenient method for the synthesis of conjugate (E,E)-1,3-diene derivatives 2 in good to excellent yields. Moreover, we also found that Pd(II)-catalyzed reactions of methylen
- Tang, Xiang-Ying,Shi, Min
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supporting information; experimental part
p. 8863 - 8868
(2009/12/26)
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- Electroreductive crossed pinacol coupling of aromatic ketones with aliphatic ketones and aldehydes
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The intermolecular crossed pinacol coupling of aromatic ketones with aliphatic aldehydes and ketones was effected by electroreduction in the presence of chlorotrimethylsilane. The best result was obtained using a Pb cathode in Bu4NPF6/sub
- Kise, Naoki,Shiozawa, Yousuke,Ueda, Nasuo
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p. 5415 - 5426
(2008/01/07)
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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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- Generation of β-keto radicals from cyclopropanols catalyzed by AgNO3
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Various β-keto radicals are generated from cyclopropanols by treatment with a catalytic amount of AgNO3 and (NH4) 2S2O8 as a reoxidant in the presence of pyridine. Thus, generated β-keto radicals react with alkenes to yield addition products. Copyright
- Chiba, Shunsuke,Cao, Zhengyan,El Bialy, Serry Atta Atta,Narasaka, Koichi
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- Copper-Mediated, Palladium-Catalyzed Coupling of Thiol Esters with Aliphatic Organoboron Reagents
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Thiol esters and B-alkyl-9-BBN derivatives couple in the presence of a copper(I) carboxylate mediator and a palladium catalyst. In contrast to copper-mediated, palladium-catalyzed cross-couplings of thioorganics with boronic acids, the current coupling reaction of 9-BBN derivatives is facilitated by the addition of a base such as Cs2CO3. Under optimized conditions, a variety of thiol esters react with different B-alkyl-9-BBN derivatives giving ketones in moderate to excellent yields.
- Yu, Ying,Liebeskind, Lanny S.
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p. 3554 - 3557
(2007/10/03)
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- Synthesis and relative stability of 3,5-diacyl-4,5-dihydro-1H-pyrazoles prepared by dipolar cycloaddition of enones and α-diazoketones
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An unusual reaction process that produced unexpected heterocyclic systems by a fragmentation-recombination mechanism is described. Thus treatment of the triketone, 3-acetyl-2,6-heptanedione, 1, with methanesulfonyl azide gave, in addition to the expected α-diazo ketone 3a, the dihydro-pyrazole 3c and its oxidation product, the pyrazole 3d. We propose that the initially formed α-diazo ketone 3a fragments into the simple a-diazomethyl ketone and methyl vinyl ketone which then undergo an intermolecular [2,3]-dipolar cycloaddition. Analogous treatment of the trifluoromethyl trione 2 again afforded a pyrazole 4c. Further experiments were carried out to lend evidence to our mechanistic hypothesis. Thus a-diazoacetophenone 5 and MVK underwent a [2,3]-dipolar cycloaddition under mild conditions to give the two regioisomeric dihydropyrazoles 6a and 6b. Interestingly these were formed in a 2:1 ratio, which suggested that 6a was more stable than 6b. The structures of 6a and 6b were optimized by using the B3LYP density functional method and the 6-31G*basis set and isomer 6a was predicted to be 1.5 kcal/mol more stable than isomer 6b. This energy difference could be rationalized by the greater capacity of the acetyl group than the benzoyl group to conjugate with the hydrazone. This difference in conjugation is reflected by key bond length differences. Thus we have discovered a novel fragmentation-cycloaddition process. We have also presented evidence for the mechanism of the formation of the dihydropyrazoles and carried out calculations to support these findings.
- Jung, Michael E.,Min, Sun-Joon,Houk,Ess, Daniel
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p. 9085 - 9089
(2007/10/03)
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- Mercuric triflate-catalyzed synthesis of 2-methylfurans from 1-alkyn-5-ones
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(Chemical Equation Presented) 2-Methylfurans were prepared by an effective cyclization of 1-alkyn-5-ones in the presence of mercuric triflate as the catalyst under very mild reaction conditions with high catalytic turnover up to 100 times. Benzene, toluen
- Imagawa, Hiroshi,Kurisaki, Takahiro,Nishizawa, Mugio
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p. 3679 - 3681
(2007/10/03)
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- Indium-trichloride catalyzed Michael reaction of silyl enol ethers with α,β-unsaturated carbonyl compounds under neat condition
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In the presence of a catalytic amount of indium (III) trichloride (InCl3) (20 mol%), ketene silyl enol ethers react quickly with α, β- unsaturated ketones and esters to afford the corresponding Michael adducts in moderate to good yields. Indium(III) trichloride can be recovered and reused without decrease in yields.
- Loh, Teck-Peng,Wei, Lin-Li
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p. 7615 - 7624
(2007/10/03)
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- Oxidative Cleavage of vic-Diols Using Copper(II) Bromide-Lithium t-Butoxide: A New Route to Unsymmetrical 1,5- and 1,6-Diketones
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Unsymmetrical 1,6-diketones were obtained by the copper(II) bromide-lithium t-butoxide oxidation of 1,2-disubstituted 1,2-cyclohexanediols. The diols were easily prepared by the addition of Grignard reagents to 2-trimethylsiloxy-2-cyelohexenone followed by the hydrolysis and treatment of the resulting 2-hydroxycyclohexanones with the second Grignard reagents. Similarly, 1,5-Diketones were obtained using 2-trimethylsiloxy-2-cyclopentenone as a starting material.
- Fujiwara, Tooru,Tsuruta, Yumiko,Arizono, Ko-Ichi,Takeda, Takeshi
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p. 962 - 964
(2007/10/03)
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- Intramolecular aldol condensations: Rate and equilibrium constants
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Rate and equilibrium constants have been determined for both the aldol addition and the elimination steps in the intramolecular condensation reactions of 2,5-hexanedione, 2,6-heptanedione, 1-phenyl-1,5-hexanedione, and 5-oxohexanal. The overall thermodynamics are similar for cyclization of 2,5-hexanedione and 2,6-heptanedione; conversion of 2,5-hexanedione to the corresponding enone is actually more favorable, but the cyclization of 2,5-hexanedione is 2400 times slower than that of 2,6-heptanedione. As expected on the basis of intermolecular analogs, the addition step is less favorable and slower for 1-phenyl-1,5-hexanedione, and the addition step for 5-oxohexanal is more favorable though similar in rate to that for heptanedione. Detailed analysis of the kinetics and equilibrium for all of these compounds, as well as 2-(2-oxopropyl)benzaldehyde, in terms of Marcus theory, leads to the same intrinsic barriers for the intramolecular reactions as were seen previously for the intermolecular reactions. This means that rate constants for intramolecular aldol reactions should be predictable from the energetics of the reactions and that the effective molarity can be calculated. Methods for estimating thermodynamic quantities for reactants and products of these reactions have been examined.
- Guthrie,Guo
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p. 11472 - 11487
(2007/10/03)
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- Photoaddition of styrene on certain β-polyketones
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The irradiation of 1,5-diphenylpentane-1,3,5-trione 1 and 1-phenylhexane-1,3,5-trione 2 at λ > 290 nm with styrene gives products of double photo-addition: 1,2,6,9-tetraphenylnonane-1,5,9-trione 5 and 1,2,6-triphenyldecane-1,5,9-trione 6, respectively.Under the same conditions with λ > 220 nm, 2-(3-oxo-3-phenylpropionyl)indane-1,3-dione 3 and 2-(3-oxobutyryl)indane-1,3-dione 4 give only products of simple photoaddition: 4-(3-oxo-3-phenylpropionyl)-2-phenylbenzocycloheptane-1,5-dione 7 and 4-(3-oxobutyryl)-2-phenylbenzocycloheptane-1,5-dione 8, respectively.The regiospecificity previously observed with the β-diketones is not a general rule for these β-triketones.The phenyl group in position 6 (products 5 and 6) is not in the α-position of the benzoyl group.The δ-triketones obtained are characterized using β-diketonic models, which are prepared by a simple sequence.Observations of products 7 and 8 show that styrene reacts with the cyclic enol only.This work may be considered as a model study for the prediction of the behavior of triketones 1, 2, 3 and 4 in the side chain of polymeric compounds.Keywords: photoaddition / styrene / β-polyketones / stereoselectivity
- Mansri, Ali,Casals, Pierre-Francois,Fan, Bo Tao,Lapluye, Gerard
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p. 247 - 252
(2007/10/02)
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- LITHIUM HYDROXIDE-CATALYZED CONJUGATE ADDITION OF β-DICARBONYL COMPOUNDS
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Lithium hydroxide proves to be a very efficient catalyst for Michael addition of β-dicarbonyl compounds 1.The application of the methodology to α,γ-diketo esters and α-keto γ-diesters 4 allows an easy approach to δ-diketones and δ-keto esters 5, respectiv
- Bonadies, Francesco,Forcellese, Maria Luigia,Locati, Ludovica,Scettri, Arrigo,Scolamiero, Cristina
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p. 467 - 468
(2007/10/02)
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- Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The synthesis of oxabicyclo[3.n.1]alkan-3-ones
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Lewis acids are employed as catalysts in the annulation of 1,4- and 1,5-dicarbonyl dielectrophiles with bis(trimethylsilyl) end ethers of β-diketones and β-keto esters. A variety of 2-(alkoxycarbonyl)-m-oxabicyclo[3.n.1]alkan-3-ones can be constructed by this process in which two new carbon-carbon bonds are generated. Unusually high regiocontrol is observed, and good to excellent stereochemical control can be achieved at virtually every position on the new carbocycles. Intramolecular neighboring group participation is proposed to explain the unusually high selectivities attained in the annulation reaction.
- Molander, Gary A.,Camera, Kimberly O.
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p. 830 - 846
(2007/10/02)
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- Generation of β-Carbonyl Radicals from Cyclopropanol Derivatives by the Oxidation with Manganese(III) 2-Pyridinecarboxylate and Their Reactions with Electron-Rich and -Deficient Olefins
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Various β-carbonyl radicals are generated oxidatively from cyclopropanol derivatives by the use of manganese(III) 2-pyridinecarboxylate (Mn(pic)3).These β-carbonyl radicals react with electron-rich olefins such as conjugated silyl enol ethers, a ketene th
- Iwasawa, Nobuharu,Hayakawa, Satoshi,Funahashi, Masahiro,Isobe, Koichi,Narasaka, Koichi
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p. 819 - 827
(2007/10/02)
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- Lanthanide trifluoromethanesulfonates as reusable catalysts. Michael and Diels-Alder reactions
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The Michael reaction of silyl enolates with α,β-unsaturated ketones and the Diels-Alder reaction of carbonyl containing dienophiles are catalyzed by a catalytic amount of lanthanide trifluoromethanesulfonate to give the corresponding adducts in high yields. In both reactions, the catalyst can be recovered and reused.
- Kobayashi,Hachiya,Takahori,Araki,Ishitani
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p. 6815 - 6818
(2007/10/02)
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- Pyridyl styrene dialkanoic acids as anti-leukotriene agents
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Compounds having the formula: STR1 are leukotriene antagonists and inhibitors of leukotriene biosynthesis. These compounds are useful as anti-asthmatic, anti-allergic, anti-inflammatory, and cytoprotective agents.
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- Organotin Triflate as Practical Catalyst for Michael Addition of Enol Silyl Ethers
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Dibutyltin bis(triflate) is a mild Lewis acid which catalyzes clean Michael addition of enol silyl ethers.The new catalyst allows to employ various labile acceptors such as methyl vinyl ketone and 2-cyclopentenone which do not undergo smooth reaction with
- Sato, Tsuneo,Wakahara, Yoshiyuki,Otera, Junzo,Nozaki, Hitosi
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p. 9773 - 9782
(2007/10/02)
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- Generation of β-Keto Radicals from Cyclopropanol Derivatives by the Use of Manganese(III) 2-Pyridinecarboxylate as an Oxidant and Their Reactions with Olefins
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Various β-keto radicals are generated from cyclopropanol derivates such as 1- or 2-substituted cyclopropanols and a cyclopropanone hemiacetal by the use of manganese(III) 2-pyridinecarboxylate, and their reactions with electron-rich olefins give cross-addition products in good yields.
- Iwasawa, Nobuharu,Hayakawa, Satoshi,Isobe, Koichi,Narasaka, Koichi
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p. 1193 - 1196
(2007/10/02)
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- A NOVEL PROCEDURE FOR DENITROHYDROGENATION BY Na2S2O4-Et3SiH
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The nitro group of α-nitro ketones is replaced by hydrogen or deuterium on treatment with Na2S2O4-Et3SiH system in HMPA-H2O or HMPA-D2O.
- Kamimura, Akio,Kurata, Kiyoko,Ono, Noboru
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p. 4819 - 4820
(2007/10/02)
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- Pyridyl dialkanoic acids and their use as medicaments
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Compounds having the formula. are leukotriene antagonists and inhibitors of leukotriene biosynthesis. These compounds are useful as anti-asthmatic, anti-allergic, anti-inflammatory, and cytoprotective agents.
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- 1,5-Dicarbonyl Compounds via Michael-Addition of Deprotonated Enamines and Allylamines to 2-(N-Methylanilino) acrylonitrile
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A new method for the synthesis of the title compounds by a onepot, three component, coupling reaction is described.Is consists of the reaction of a homoenolate anion and an enol cation equivalent with subsequent alkylation of an acyl-anion equivalent.Hence the methodology of Umpolung is used in a threefold manner within the reaction sequence.
- Ahlbrecht, Hubertus,Dietz, Manfred,Weber, Lothar
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p. 251 - 254
(2007/10/02)
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- THE ZIRCONOCENE INDUCED COUPLING OF BENZYNE WITH NITRILES: SYNTHESIS, STRUCTURE AND REACTIONS OF NOVEL AZAMETALLACYCLOPENTENES
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A series of novel azazirconacyclopentenes have been prepared by the thermolysis of diphenylzirconocene in the presence of one equivalent of a wide variety of nitriles.An X-ray crystal structure shows these metallacycles to be dimeric in the solid state.
- Buchwald, Stephen L.,Sayers, Ann,Watson, Brett T.,Dewan, John C.
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p. 3245 - 3248
(2007/10/02)
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- REGIOSELECTIVE HYDRATION OF ALKYNONES BY PALLADIUM CATALYSIS
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Diketones are regioselectively prepared from alkynyl ketones under mild conditions by palladium catalysis; 5-heptyn-2-one and 2-(2-nonynyl)cyclohexanone give 1,4-diketones whereas 2-(2-heptynyl)cyclopentanone and 5,6-didehydroprostaglandin E2 methyl ester afford 1,5-diketones.
- Imi, Katsuharu,Imai, Kumiko,Utimoto, Kiitiro
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p. 3127 - 3130
(2007/10/02)
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- A CONVENIENT PROCEDURE FOR CARBOXYLATION-ROBINSON ANNULATIONS OF KETONES USING TRIETHYLAMINE BASE IN THE PRESENCE OF MAGNESIUM CHLORIDE
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Carboxylation of ketones with carbon dioxide in the presence of magnesium chloride and triethylamine followed by reaction with methyl vinyl ketone gives satisfactory yields of Michael and Robinson annulation products.
- Olsen, Richard S.,Fataftah, Zakaria A.,Rathke, Michael W.
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p. 1133 - 1140
(2007/10/02)
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- 1,5-DICARBONYL COMPOUNDS A GENERAL PREPARATION METHOD
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In this report, a general method for the preparation of 1,5-dicarbonyl compounds and six membered ring annelation is described.This method involves the reaction of hemiacetal vinylogs 1 with enol ethers 2 or 3 in the presence of a Lewis acid.This reaction was successfully applied to the enol ethers of α and α,α'-hindered ketones such as 2,2,6-trimethyl cyclohexanone. α-Cyperone and 6-epi-α-cyperone were obtained using this process.
- Duhamel, P.,Hennequin, L.,Poirier, J. M.,Tavel, G.,Vottero, C.
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p. 4777 - 4786
(2007/10/02)
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- Pyran Annelation: An Effective Route to a Tricyclic Dienone
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A new pyran annelation reaction was investigated. 2,6-Dimethyl-4H-pyran-4-one (2) was converted to 2((p-tolylsulfonyl)methyl)-6-methyl-4H-pyran-4-one (7) which was alkylated at the C-2 methylene position regioselectively, and the p-tolylsulfonyl group can be easily eliminated with an aluminium amalgam reduction.On the other hand the pyran-4-one ring was easily transformed into an 1,5-diketone derivative.By joining and applying these selective alkylations and transformations, tricyclic dienone 22 was effectively synthesized from 2.
- Yamamoto, Makoto,Iwasa, Seiji,Takatsuka, Kenichi,Yamada, Kazutoshi
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p. 346 - 349
(2007/10/02)
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- ON THE SYNTHESIS OF 1,n-DIKETONES USING MONO-SUBSTITUTED DERIVATIVES OF TOSYLMETHYL ISOCYANIDE
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A new method is described for the synthesis of symmetrical and unsymmetrical diketones.Particularly good results are obtained in the synthesis of 1,6- and 1,5-diketones.Procedures are reported for 1,2-diketones.The moderate results obtained for 1,4-diketones and the lack of success for 1,3-diketones are discussed.
- Leusen, Albert M. van,Oosterwijk, Roelof,Echten, Erik van,Leusen, Daan van
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- A New Synthesis of 1,5-Dicarbonyl Compounds under Neutral Conditions
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Michael addition of α-nitroketones to methyl vinyl ketone or acrylaldehyde followed by denitration with Bu3SnH affords 1,5-dicarbonyl compounds in good yields.
- Ono, Noboru,Miyake, Hideyoshi,Kaji, Aritsune
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p. 875 - 876
(2007/10/02)
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