- Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes
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We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.
- Hirao, Yuki,Kanai, Motomu,Katayama, Yuri,Mitsunuma, Harunobu
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supporting information
(2020/11/18)
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- Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls
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A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the RhI-catalysed hydrogen generation and Rh0-catalysed hydrogenation is proposed for the reaction.
- Lin, Xiao,Wang, Yuhan,Hu, Yan,Zhu, Wanjiang,Dou, Xiaowei
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supporting information
p. 1046 - 1049
(2020/02/25)
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- Regioselective Vinylation of Remote Unactivated C(sp3)?H Bonds: Access to Complex Fluoroalkylated Alkenes
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Regioselective incorporation of a particular functional group into aliphatic sites by direct activation of unreactive C?H bonds is of great synthetic value. Despite advances in radical-mediated functionalization of C(sp3)?H bonds by a hydrogen-atom transfer process, the site-selective vinylation of remote C(sp3)?H bonds still remains underexplored. Reported herein is a new protocol for the regioselective vinylation of unactivated C(sp3)?H bonds. The remote C(sp3)?H activation is promoted by a C-centered radical instead of the commonly used N and O radicals. The reaction possesses high product diversity and synthetic efficiency, furnishing a plethora of synthetically valuable E alkenes bearing tri-/di-/mono-fluoromethyl and perfluoroalkyl groups.
- Wu, Shuo,Wu, Xinxin,Wang, Dongping,Zhu, Chen
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supporting information
p. 1499 - 1503
(2019/01/04)
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- Regioselective Sulfonylvinylation of the Unactivated C(sp3)-H Bond via a C-Centered Radical-Mediated Hydrogen Atom Transfer (HAT) Process
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Given the similarity of multiple sp3 C-H bonds in electronic properties and bond dissociation energy (BDE), regioselective sp3 C-H bond functionalization remains a paramount challenge. Here, we report a C-centered radical-mediated approach for site-specific sulfonylvinylation of the C(sp3)-H bond via the hydrogen atom transfer (HAT) process. The reaction features mild conditions, broad substrate scope, and high regioselectivity and stereoselectivity, manifesting the nontrivial synthetic potential.
- Yang, Shan,Wu, Xinxin,Wu, Shuo,Zhu, Chen
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supporting information
p. 4837 - 4841
(2019/06/24)
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- Method for synthesizing alkyne through catalytic asymmetric cross coupling (by machine translation)
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The invention belongs to the field of, asymmetric synthesis, and discloses a method for catalyzing asymmetric cross- coupling to synthesize: an alkyne, and the L method comprises, the following steps, of A: preparing B a cuprous, salt and C a: ligand; preparing a catalyst; adding a base; reacting the compound with the compound with the compound; and reacting the compound with the compound. Of these, one of them, X is selected from the group consisting of, R halogens. 1 Optionally substituted heteroarylsulfonylcyanamide groups selected from the, group consisting, of optionally substituted, phenyl groups In-flight vehicle, R6 Trialkyl silyl groups or alkyl radicals, R2 Cycloalkyl radicals optionally substituted with an, optionally substituted alkyl, (CH radical2 )n R4 Multi,layer chain, n=0-10,R saw blade4 A group selected, from, the group consisting of phenyl, alkenyl, aralkynyls, noonyloxy,and, noonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylphenyl disiloxy-radicals. R3 A ligand, selected from hydrogen or any of the functional groups, is selected from the group consisting of, hydrogen and any L other functional group. The method, R disclosed by the, A invention has the, advantages of good catalytic, R ’ effect, wide application range. and high catalytic efficiency, and the, method disclosed by the, invention has the. advantages of good catalytic effect, wide application range and high catalytic efficiency. (by machine translation)
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Paragraph 0205; 0331-0332
(2020/01/12)
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- Design of Manganese Phenol Pi-complexes as Shvo-type Catalysts for Transfer Hydrogenation of Ketones
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Catalytic hydrogenation is one of the most important reactions both in academic research and industry. We explored ability of the manganese pi-complexes to act as Shvo-type catalysts for transfer hydrogenation of ketones. DFT calculations suggested that the transfer of hydrogen atoms from the hypothetical intermediate [(C6Me3H2OH)Mn(CO)2H] to acetone has low activation barrier of 10.9 kcal mol?1. Experimentally a number of ketones with various functional groups (OMe, NH2, Cl, CF3, pyridyl) were successfully reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex.
- Shvydkiy, Nikita V.,Vyhivskyi, Oleksandr,Nelyubina, Yulia V.,Perekalin, Dmitry S.
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p. 1602 - 1605
(2019/03/07)
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- Photoenzymatic Catalysis Enables Radical-Mediated Ketone Reduction in Ene-Reductases
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Flavin-dependent ene-reductases (EREDs) are known to stereoselectively reduce activated alkenes, but are inactive toward carbonyls. Demonstrated here is that in the presence of photoredox catalysts, these enzymes will reduce aromatic ketones. Mechanistic experiments suggest this reaction proceeds through ketyl radical formation, a reaction pathway that is distinct from the native hydride-transfer mechanism. Furthermore, this reactivity is accessible without modification of either the enzyme or cofactors, allowing both native and non-natural mechanisms to occur simultaneously. Based on control experiments, we hypothesize that binding to the enzyme active site attenuates the reduction potential of the substrate, enabling single-electron reduction. This reactivity highlights opportunities to access new catalytic manifolds by merging photoredox catalysis with biocatalysis.
- Sandoval, Braddock A.,Kurtoic, Sarah I.,Chung, Megan M.,Biegasiewicz, Kyle F.,Hyster, Todd K.
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supporting information
p. 8714 - 8718
(2019/05/28)
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- Diastereoselective C?H Bond Amination for Disubstituted Pyrrolidines
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We report herein the improved diastereoselective synthesis of 2,5-disubstituted pyrrolidines from aliphatic azides. Experimental and theoretical studies of the C?H amination reaction mediated by the iron dipyrrinato complex (AdL)FeCl(OEt2) provided a model for diastereoinduction and allowed for systematic variation of the catalyst to enhance selectivity. Among the iron alkoxide and aryloxide catalysts evaluated, the iron phenoxide complex exhibited superior performance towards the generation of syn 2,5-disubstituted pyrrolidines with high diastereoselectivity.
- Iovan, Diana A.,Wilding, Matthew J. T.,Baek, Yunjung,Hennessy, Elisabeth T.,Betley, Theodore A.
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supporting information
p. 15599 - 15602
(2017/11/16)
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- Ruthenium(III)-Catalyzed β-Alkylation of Secondary Alcohols with Primary Alcohols
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A Ru(III)-NNN complex bearing a pyridyl-supported pyrazolyl-imidazolyl ligand was synthesized and utilized as the catalyst for the direct β-alkylation of secondary alcohols with primary alcohols. β-Alkylated secondary alcohols were obtained in moderate to high yields with water formed as the byproduct through a hydrogen borrowing pathway. The present protocol provides a concise atom-economical and environmentally benign method for C-C bond formation.
- Wang, Qingfu,Wu, Kaikai,Yu, Zhengkun
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p. 1251 - 1256
(2016/06/01)
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- Oxidation and β-Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N-Heterocyclic Carbene Ligands
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The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for C-C bond forming processes offering significant environmental benefits over traditional approaches. Iridium(I)-cyclooctadiene complexes having a NHC ligand with a O- or N-functionalised wingtip efficiently catalysed the oxidation and β-alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex [Ir(NCCH3)(cod)(MeIm(2- methoxybenzyl))][BF4] (cod=1,5-cyclooctadiene, MeIm=1-methylimidazolyl) having a rigid O-functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF0) of 1283 h-1, and also in the β-alkylation of 2-propanol with butan-1-ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan-2-ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross-aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new C-C bond that involves the reaction of an O-bound enolate generated in the basic medium with the electrophilic aldehyde.
- Jiménez, M. Victoria,Fernández-Tornos, Javier,Modrego, F. Javier,Pérez-Torrente, Jesús J.,Oro, Luis A.
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supporting information
p. 17877 - 17889
(2015/12/08)
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- An umpolung sulfoxide reagent for use as a functionalized benzyl carbanion equivalent
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N-Methyl ortho-carbamoylaryl benzyl sulfoxides can be used as synthetic equivalents for α-hydroxy, α-chloro, and α-acetammido benzyl carbanions by means of a two-step sequence involving highly diastereoselective α-C-alkylation with alkyl halides followed by displacement of the sulfinyl residue (which can be recovered and recycled) by a hydroxyl, a chlorine or an acetamido, respectively, under non-oxidative Pummerer conditions. The scope and limits of the method, including a stereoselective version of the reaction, as well as the mechanism of the process are discussed in detail.
- Pinna, Giovanni,Bellucci, Maria Cristina,Malpezzi, Luciana,Pisani, Laura,Superchi, Stefano,Volonterio, Alessandro,Zanda, Matteo
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p. 5268 - 5281
(2011/08/06)
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- Iridium phosphine abnormal N-heterocyclic carbene complexes in catalytic hydrogen transfer reactions
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Several iridium complexes bearing chelating abnormal N-heterocyclic carbenes (NHCs) are shown to be active catalysts for transfer hydrogenation of ketones or enones, dehydrative C-C coupling between primary and secondary alcohols, and dehydrogenation of benzyl alcohol to benzyl benzoate. In the transfer hydrogenation of acetophenone, abnormal NHC complexes give higher activity than a normal analogue. Dehydrative C-C coupling reactions between primary and secondary alcohols result in β-alkylation of the secondary alcohols, using primary alcohols as the apparent alkylating reagents, and such reactions proceed with high yield and selectivity. These catalytic processes are known to involve metal-mediated temporary borrowing of hydrogen from alcohols and subsequent delivery of the hydrogen to CC and /or CO bonds.
- Gong, Xue,Zhang, Hong,Li, Xingwei
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p. 5596 - 5600
(2011/11/06)
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- Alcohol cross-coupling reactions catalyzed by Ru and Ir terpyridine complexes
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Primary alcohols can be coupled with secondary benzylic alcohols by an air-stable catalytic system involving terpyridine ruthenium or iridium complexes.
- Gnanamgari, Dinakar,Leung, Chin Hin,Schley, Nathan D.,Hilton, Sheena T.,Crabtree, Robert H.
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experimental part
p. 4442 - 4445
(2009/02/07)
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- Direct β-alkylation of secondary alcohols with primary alcohols catalyzed by a Cp*Ir complex
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(Chemical Equation Presented) A new catalytic system for β-alkylation of secondary alcohols has been developed. In the presence of [Cp*IrCl 2]2 (Cp* = pentamethylcyclopentadienyl) catalyst and base, the reactions of various secondary alcohols with primary alcohols give β-alkylated higher alcohols in good to excellent yields without any hydrogen acceptor or hydrogen donor. This reaction proceeds via successive hydrogen-transfer reactions and aldol condensation.
- Fujita, Ken-Ichi,Asai, Chiho,Yamaguchi, Tetsuhiro,Hanasaka, Fumihiro,Yamaguchi, Ryohei
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p. 4017 - 4019
(2007/10/03)
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- An umpolung sulfoxide reagent as α-hydroxy and α-chloro benzyl carbanion equivalents
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ortho-[(N-Methyl)carbamoyl]phenyl benzyl sulfoxide is used as a synthetic equivalent of α-hydroxy and α-chloro benzyl carbanions by means of a two-step sequence involving (1) highly stereoselective α-C-alkylation with alkyl bromides, and (2) displacement of the sulfinyl group by an OH or a Cl under Pummerer or chloro-Pummerer conditions, respectively. The sulfinyl auxiliary can be effectively regenerated and recycled.
- Volonterio, Alessandro,Bravo, Pierfrancesco,Zanda, Matteo
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p. 6537 - 6540
(2007/10/03)
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- Addition of organocerium reagents to homoallyl alcohols
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Alkylcerium reagents and hydride ions add to multiple bonds of homoallyl alcohols under mild conditions, leading to saturated alcohols in good yields.
- Bartoli, Giuseppe,Dalpozzo, Renato,De Nino, Antonio,Procopio, Antonio,Sambri, Letizia,Tagarelli, Antonio
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p. 8833 - 8835
(2007/10/03)
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- Behaviors of α-Fluorocarbenoids Derived from the Nucleophilic Desulfinylation of α-Chloro-α-fluoroalkyl Sulfoxides
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2-Aryl-1-chloro-1-fluoroethyl sulfoxides underwent nucleophilic desulfinylation with PhMgBr to give (Z)-fluorostyrene derivatives in a very stereoselective manner (>33:1) via an α-fluorocarbene species.When treated with 3 equiv of PhLi in the presence of N,N,N',N'-tetramethylethylenediamine, they similarly formed fluorostyrenes as a stereoisomeric mixture (E:Z = 2:1), but with 1 equiv of PhLi 1-aryl-1-chloro-1-fluoroethanes were the major product.On the other hand, no formation of a fluoroalkene was observed in the desulfinylation of 1-chloro-1-fluoro-4-phenylbutyl sul foxide with the nucleophiles.In the latter reaction, oxidation and/or phenylation of the intermediate carbene were the main pathways.
- Uno, Hidemitsu,Sakamoto, Katsuji,Semba, Fumihiko,Suzuki, Hitomi
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p. 210 - 217
(2007/10/02)
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- STRUCTURE OF THE INTERMEDIATE FORMED IN THE REACTION OF THE STYRENE RADICAL CATION AND NEUTRAL STYRENE.
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The structure of the ion-molecule adduct produced in the gas-phase reaction of the styrene radical cation with neutral styrene has been probed by collisionally stabilizing the adduct and then acquiring its collision-activated decomposition (CAD) spectrum with a tandem mass spectrometer. The CAD spectrum of the adduct is nearly identical with the CAD spectra of the cis- and trans-diphenylcyclobutane radical cations and with the product ion resulting from a 1,4-regiospecific water elimination from the 1,4-diphenylbutan-1-ol radical cation; therefore the radical cations from all four precursors possess the same structure. The DELTA H//f of this radical cation is shown to be less than equivalent to 239 kal/mol; therefore it cannot have the trans-1,2-diphenylcyclobutane structure ( DELTA H//f equals 247 kcal/mol). The results support a two-step mechanism for the left bracket 1 plus 2 right bracket cycloaddition reaction.
- Groenewold,Chess,Gross
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p. 539 - 543
(2007/10/02)
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