- The effect of a para substituent on the conformational preference of 2,2-diphenyl-1,3-dioxanes: Evidence for the anomeric effect from X-ray crystal structure analysis
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The molecular structures of 2,2-di(para-substituted phenyl)-1,3-dioxanes were elucidated for the first time by X-ray crystallographic analysis, which revealed two important structural features: (1) These compounds have the chair conformation in which electron-withdrawing aryl groups [viz. p-nitro-or p-(trifluormethyl)phenyl] are always axial and electron-donating aryl groups (viz. p-methoxyphenyl) are always equatorial. (2) In these compounds as well as in symmetrically substituted 2,2-diphenyl-1,3-dioxane the axial C2-aryl bond is longer than the equatorial C2-aryl bond. The axial preference of the electron-withdrawing aryl group was also demonstrated in solution by 1H and 13C NMR spectroscopy. The anomeric carbon substituted with an electron-withdrawing aryl group resonates at an unusually high field, as does the aromatic carbon bearing the electron-withdrawing substituent. The observed 13C NMR data clearly indicate enhanced electron density at these carbons due to the anomeric effect. Semiempirical molecular orbital calculations by the MOPAK PM3 method reproduced the bond lengthening for axial C2-aryl, while the heat of formation derived from this calculation failed to support the axial preference of electron-withdrawing aryl groups. The X-ray crystallographic data on the conformational preference and bond lengths at the anomeric carbon, as well as the solution NMR spectroscopic data, clearly indicate the anomeric effect that is best rationalized in terms of stabilizing interaction between the lone-pair electrons on the ring oxygens and the antibonding orbital of the axial C2-aryl bond.
- Uehara, Fumiaki,Sato, Masayuki,Kaneko, Chikara,Kurihara, Hiroyuki
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- Dirhodium-Catalyzed Enantioselective B?H Bond Insertion of gem-Diaryl Carbenes: Efficient Access to gem-Diarylmethine Boranes
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The scarcity of reliable methods for synthesizing chiral gem-diarylmethine borons limits their applications. Herein, we report a method for highly enantioselective dirhodium-catalyzed B?H bond insertion reactions with diaryl diazomethanes as carbene precursors. These reactions afforded chiral gem-diarylmethine borane compounds in high yield (up to 99 % yield), high activity (turnover numbers up to 14 300), high enantioselectivity (up to 99 % ee) and showed unprecedented broad functional group tolerance. The borane compounds synthesized by this method could be efficiently transformed into diaryl methanol, diaryl methyl amine, and triaryl methane derivatives with good stereospecificity. Mechanistic studies suggested that the borane adduct coordinated to the rhodium catalyst and thus interfered with decomposition of the diazomethane, and that insertion of a rhodium carbene (generated from the diaryl diazomethane) into the B?H bond was most likely the rate-determining step.
- Huang, Ming-Yao,Li, Xiao-Yu,Su, Yu-Xuan,Yang, Liang-Liang,Zhao, Yu-Tao,Zhu, Shou-Fei
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supporting information
p. 24214 - 24219
(2021/10/07)
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- Systematic Evaluation of 1,2-Migratory Aptitude in Alkylidene Carbenes
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Alkylidene carbenes undergo rapid inter- and intramolecular reactions and rearrangements, including 1,2-migrations of β-substituents to generate alkynes. Their propensity for substituent migration exerts profound influence over the broader utility of alkylidene carbene intermediates, yet prior efforts to categorize 1,2-migratory aptitude in these elusive species have been hampered by disparate modes of carbene generation, ultrashort carbene lifetimes, mechanistic ambiguities, and the need to individually prepare a series of 13C-labeled precursors. Herein we report on the rearrangement of 13C-alkylidene carbenes generated in situ by the homologation of carbonyl compounds with [13C]-Li-TMS-diazomethane, an approach that obviates the need for isotopically labeled substrates and has expedited a systematic investigation (13C{1H} NMR, DLPNO-CCSD(T)) of migratory aptitudes in an unprecedented range of more than 30 alkylidene carbenes. Hammett analyses of the reactions of 26 differentially substituted benzophenones reveal several counterintuitive features of 1,2-migration in alkylidene carbenes that may prove of utility in the study and synthetic application of unsaturated carbenes more generally.
- Dale, Harvey J. A.,Nottingham, Chris,Poree, Carl,Lloyd-Jones, Guy C.
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p. 2097 - 2107
(2021/02/01)
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- A convenient pinacol coupling of diaryl ketones with B2pin2viapyridine catalysis
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A convenient, pyridine-boryl radical-mediated pinacol coupling of diaryl ketones is developed. In contrast to the conventional pinacol coupling that requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed by DFT calculations, which suggests the necessity of both aromatic rings for the maximum stabilization of the transition states.
- Jo, Junhyuk,Kim, Seonyul,Choi, Jun-Ho,Chung, Won-Jin
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supporting information
p. 1360 - 1363
(2021/02/22)
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- Photocontrolled Radical Polymerization from Hydridic C-H Bonds
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Given the ubiquity of carbon-hydrogen bonds in biomolecules and polymer backbones, the development of a photocontrolled polymerization selectively grafting from a C-H bond represents a powerful strategy for polymer conjugation. This approach would circumvent the need for complex synthetic pathways currently used to introduce functionality at a polymer chain end. On this basis, we developed a hydrogen-atom abstraction strategy that allows for a controlled polymerization selectively from a hydridic C-H bond using a benzophenone photocatalyst, a trithiocarbonate-derived disulfide, and visible light. We performed the polymerization from a variety of ethers, alkanes, unactivated C-H bonds, and alcohols. Our method lends itself to photocontrol which has important implications for building advanced macromolecular architectures. Finally, we demonstrate that we can graft polymer chains controllably from poly(ethylene glycol) showcasing the potential application of this method for controlled grafting from C-H bonds of commodity polymers.
- Stache, Erin E.,Kottisch, Veronika,Fors, Brett P.
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supporting information
p. 4581 - 4585
(2020/03/05)
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- Water Phase, Room Temperature, Ligand-Free Suzuki–Miyaura Cross-Coupling: A Green Gateway to Aryl Ketones by C–N Bond Cleavage
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We report herein a green strategy for synthesis of aryl ketones from twisted amides by using Pd(OAc)2 as catalysts. This method shows high functional group tolerance to offer a variety of ketones in good yields under mild conditions (up to 94 %). Notably, this methodology demonstrates the first water phase, room temperature, ligand-free Suzuki–Miyaura coupling through C–N bond cleavage, which is environmentally friendly and might facilitate the development of amide based green chemistry.
- Zhang, Yuqi,Wang, Zijia,Tang, Zhao,Luo, Zhongfeng,Wu, Hongxiang,Liu, Tingting,Zhu, Yulin,Zeng, Zhuo
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p. 1620 - 1628
(2020/03/04)
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- Direct C-H Arylation of Aldehydes by Merging Photocatalyzed Hydrogen Atom Transfer with Palladium Catalysis
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Herein, we report that merging palladium catalysis with hydrogen atom transfer (HAT) photocatalysis enabled direct arylations and alkenylations of aldehyde C-H bonds, facilitating visible light-catalyzed construction of a variety of ketones. Tetrabutylammonium decatungstate and anthraquinone were found to act as synergistic HAT photocatalysts. Density functional theory calculations suggested a Pd0-PdII-PdIII-PdI-Pd0 pathway and revealed that regeneration of the Pd0 catalyst and the photocatalyst occurs simultaneously in the presence of KHCO3. This regeneration features a low energy barrier, promoting efficient coupling of the palladium catalytic cycle with the photocatalytic cycle. The work reported herein suggests great promise for further applications of HAT photocatalysis in palladium-catalyzed cross-coupling and C-H functionalization reactions to be successful.
- Chen, Guangying,Cheng, Gui-Juan,Guo, Bin,Li, Xiaobao,Ran, Chongzhao,Wang, Lu,Wang, Ting,Wei, Jun-Jie,Zheng, Caijuan,Zheng, Chao
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p. 7543 - 7551
(2020/08/21)
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- Binuclear Palladium Complex Immobilized on Mesoporous SBA-16: Efficient Heterogeneous Catalyst for the Carbonylative Suzuki Coupling Reaction of Aryl Iodides and Arylboronic Acids Using Cr(CO)6 as Carbonyl Source
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Abstract: In this study, a binuclear palladium complex immobilized on the organo-functionalized SBA-16 was prepared and structurally characterized by routine techniques. Characterizations indicated that the mesostructure of SBA-16 was maintained after the immobilization of palladium complex. Then, the prepared nanomaterial was applied as a heterogeneous catalyst in the carbonylative Suzuki coupling reaction of aryl iodides with arylboronic acids using Cr(CO)6 as carbonyl source. The catalyst was efficiently promoted the coupling reactions of various aryl iodides and arylboronic acids to give the corresponding diaryl ketones in excellent yields. Moreover, the catalyst was readily recovered by filtration and could be reused for seven cycles without losing its structural integrity and catalytic activity. Graphic Abstract: [Figure not available: see fulltext.].
- Niakan, Mahsa,Asadi, Zahra,Emami, Mohammad
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p. 404 - 418
(2020/01/03)
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- Kinetically Controlled, Highly Chemoselective Acylation of Functionalized Grignard Reagents with Amides by N?C Cleavage
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The direct transition-metal-free acylation of amides with functionalized Grignard reagents by highly chemoselective N?C cleavage under kinetic control has been accomplished. The method offers rapid and convergent access to functionalized biaryl ketones through transient tetrahedral intermediates. The direct access to functionalized Grignard reagents by in situ halogen–magnesium exchange promoted by the versatile turbo-Grignard reagent (iPrMgCl?LiCl) permits excellent substrate scope with respect to both the amide and Grignard coupling partners. These reactions enable facile, operationally simple and chemoselective access to tetrahedral intermediates from amides under significantly milder conditions than chelation-controlled intermediates. This novel direct two-component coupling sets the stage for using amides as acylating reagents in an alternative paradigm to the metal-chelated approach, acyl metals and Weinreb amides.
- Li, Guangchen,Szostak, Michal
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p. 611 - 615
(2020/01/02)
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- 2-Methyltetrahydrofuran (2-MeTHF): A Green Solvent for Pd?NHC-Catalyzed Amide and Ester Suzuki-Miyaura Cross-Coupling by N?C/O?C Cleavage
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The palladium-NHC-catalyzed (NHC=N-heterocyclic carbene) Suzuki-Miyaura cross-coupling of amides and esters via highly chemoselective N?C(O) and O?C(O) cleavage with aryl boronic acids using green, sustainable and eco-friendly 2-methyltetrahydrofuran (2-MeTHF) is reported. A variety of amides and aryl esters were coupled with aryl boronic acids in high to excellent yields. This method employs commercially-available, air- and moisture-stable Pd(II) ?NHC precatalysts. Crucially, the use of 2-MeTHF leads to the highest TON reported to date in amide N?C(O) bond cross-coupling. This operationally-simple protocol was utilized in the synthesis a bioactive ketone intermediate, emphasizing the potential of 2-MeTHF as a green solvent in unconventional amide bond disconnection. Given the tremendous importance of amide bond cross-coupling strategies and the drive to maintain full sustainability in cross-coupling processes, we expect that the synthetic method will be of broad interest.
- Lei, Peng,Ling, Yun,An, Jie,Nolan, Steven P.,Szostak, Michal
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supporting information
p. 5654 - 5660
(2019/11/16)
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- I-Pr2NMgCl·LiCl Enables the Synthesis of Ketones by Direct Addition of Grignard Reagents to Carboxylate Anions
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The direct preparation of ketones from carboxylate anions is greatly limited by the required use of organolithium reagents or activated acyl sources that need to be independently prepared. Herein, a specific magnesium amide additive is used to activate and control the addition of more tolerant Grignard reagents to carboxylate anions. This strategy enables the modular synthesis of ketones from CO2 and the preparation of isotopically labeled pharmaceutical building blocks in a single operation.
- Colas, Kilian,Dos Santos, A. Catarina V. D.,Mendoza, Abraham
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supporting information
(2019/10/08)
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- Triflamides: Highly Reactive, Electronically Activated N-Sulfonyl Amides in Catalytic N-C(O) Amide Cross-Coupling
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The direct, highly chemoselective Suzuki-Miyaura cross-coupling of trifluoromethanesulfonamides (triflamides) by selective N-C(O) amide bond cleavage is reported. This operationally simple, mild, and user-friendly method accomplishes the direct synthesis of ketones from amides by a catalytic manifold as a powerful alternative to Weinreb amides. Mechanistic studies support rotational inversion and electronic activation, favoring selective insertion under mild conditions. Our data strongly suggest that triflamides should be routinely considered as precursors in amide bond cross-coupling.
- Shi, Shicheng,Lalancette, Roger,Szostak, Roman,Szostak, Michal
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supporting information
p. 1253 - 1257
(2019/02/26)
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- Sp3 C-H Arylation and Alkylation Enabled by the Synergy of Triplet Excited Ketones and Nickel Catalysts
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Triplet ketone sensitizers are of central importance within the realm of photochemical transformations. Although the radical-type character of triplet excited states of diaryl ketones suggests the viability for triggering hydrogen-atom transfer (HAT) and single-electron transfer (SET) processes, among others, their use as multifaceted catalysts in C-C bond-formation via sp3 C-H functionalization of alkane feedstocks still remains rather unexplored. Herein, we unlock a modular photochemical platform for forging C(sp3)-C(sp2) and C(sp3)-C(sp3) linkages from abundant alkane sp3 C-H bonds as functional handles using the synergy between nickel catalysts and simple, cheap and modular diaryl ketones. This method is distinguished by its wide scope that is obtained from cheap catalysts and starting precursors, thus complementing existing inner-sphere C-H functionalization protocols or recent photoredox scenarios based on iridium polypyridyl complexes. Additionally, such a platform provides a new strategy for streamlining the synthesis of complex molecules with high levels of predictable site-selectivity and preparative utility. Mechanistic experiments suggest that sp3 C-H abstraction occurs via HAT from the ketone triplet excited state. We believe this study will contribute to a more systematic utilization of triplet excited ketones as catalysts in metallaphotoredox scenarios.
- Shen, Yangyang,Gu, Yiting,Martin, Ruben
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p. 12200 - 12209
(2018/09/27)
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- Rapidly Activating Pd-Precatalyst for Suzuki-Miyaura and Buchwald-Hartwig Couplings of Aryl Esters
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Esters are valuable electrophiles for cross-coupling due to their ubiquity and ease of synthesis. However, harsh conditions are traditionally required for the effective cross-coupling of ester substrates. Utilizing a recently discovered precatalyst, Pd-catalyzed Suzuki-Miyaura and Buchwald-Hartwig reactions involving cleavage of the C(acyl)-O bond of aryl esters that proceed under mild conditions are reported. The Pd(II) precatalyst is highly active because it is reduced to the Pd(0) active species more rapidly than previous precatalysts.
- Dardir, Amira H.,Melvin, Patrick R.,Davis, Ryan. M.,Hazari, Nilay,Mohadjer Beromi, Megan
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supporting information
p. 469 - 477
(2018/02/19)
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- Synthesis of diaryl ketones through oxidative cleavage of the C-C double bonds in N -Sulfonyl enamides
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An oxidative cleavage of a C-C double bond is developed from the photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen, followed by a ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. Moreover, the oxidative cleavage of C-C triple bonds from 1-alkynes is demonstrated for the synthesis of symmetrical and unsymmetrical ketones from the Cu-catalyzed [3+2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because the synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the present method is notable.
- Kim, Hyunseok,Park, Sangjune,Baek, Yonghyeon,Um, Kyusik,Han, Gi Uk,Jeon, Da-Hye,Han, Sang Hoon,Lee, Phil Ho
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p. 3486 - 3496
(2018/04/14)
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- N-Acylsuccinimides: Efficient acylative coupling reagents in palladium-catalyzed Suzuki coupling via C–N cleavage
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An acylative Suzuki coupling of activated amides with aryl boronic acids has been reported via palladium-catalyzed C–N bond cleavage. This protocol demonstrate amides can be activated by an atom-economic and cheap succinimide, which can be efficiently utilized to synthesize broad array of diaryl ketones in moderate to good yields.
- Cui, Ming,Chen, Zeyu,Liu, Tingting,Wang, Hui,Zeng, Zhuo
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supporting information
p. 3819 - 3822
(2017/09/15)
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- Base free Suzuki acylation reactions of sodium (aryl trihydroxyborate) salts: A novel synthesis of substituted aryl ketones
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The first simple and efficient base free Pd(PPh3)4 catalysed synthesis of substituted aryl ketones from acyl chlorides and easily accessible sodium aryl trihydroxyborate salts in aqueous toluene is reported. The reaction conditions appeared versatile and tolerable to a variety of functional groups including, CF3, OMe, SMe, Br, NO2, F, OH and NH2 furnishing 25 examples of substituted aryl ketones in isolated yields of up to 96% in 24 h. Beside the high purity, the ease and convenience of the isolation compared to boronic acids, sodium aryl trihydroxyborate salts could be used subsequently without the addition of excess amount of an activator and are more user-friendly in terms of the use of accurate reaction stoichiometry.
- Sithebe, Siphamandla,Molefe, Patience
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p. 305 - 311
(2017/07/13)
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- Suzuki-Miyaura cross-coupling of amides and esters at room temperature: Correlation with barriers to rotation around C-N and C-O bonds
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The Suzuki-Miyaura cross-coupling has been widely recognized as one of the most important methods for the construction of C-C bonds. However, in contrast to traditional aryl halide or pseudohalide electrophiles, coupling reactions with unactivated C-N and C-O electrophiles have proven significantly more challenging. Here we report the first general palladium-catalyzed Suzuki-Miyaura cross-coupling of both common amides and aryl esters through the selective cleavage of the C-N and C-O bonds under exceedingly mild conditions. Notably, for the first time we demonstrate selective C(acyl)-N and C(acyl)-O cleavage/cross-coupling under the same reaction conditions. The reaction uses a commercially available, bench-stable and operationally-convenient (η3-1-t-Bu-indenyl)Pd(IPr)(Cl) precatalyst. Furthermore, we demonstrate that the reactivity of generic amides and aryl esters can be correlated with barriers to isomerization around the C(acyl)-X (X = N, O) bond, thus providing a blueprint for the development of a broad range of novel coupling reactions of ester and amide electrophiles by the selective activation of C-O and C-N bonds.
- Lei, Peng,Meng, Guangrong,Shi, Shicheng,Ling, Yun,An, Jie,Szostak, Roman,Szostak, Michal
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p. 6525 - 6530
(2017/08/29)
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- Palladium-catalyzed Suzuki-Miyaura coupling of aryl esters
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The Suzuki-Miyaura coupling is among the most important C-C bond-forming reactions available due to its reliability, chemoselectivity, and diversity. Aryl halides and pseudohalides such as iodides, bromides, and triflates are traditionally used as the electrophilic coupling partner. The expansion of the reaction scope to nontraditional electrophiles is an ongoing challenge to enable an even greater number of useful products to be made from simple starting materials. Herein, we present how an NHC-based Pd catalyst can enable Suzuki-Miyaura coupling where the C(acyl)-0 bond of aryl esters takes on the role of electrophile, allowing the synthesis of various ketone-containing products. This contrasts known reactions of similar esters that provide biaryls via nickel catalysis. The underlying cause of this mechanistic divergence is investigated by DFT calculations, and the robustness of esters compared to more electrophilic acylative coupling partners is analyzed.
- Halima, Taoufik Ben,Zhang, Wanying,Yalaoui, Imane,Hong, Xin,Yang, Yun-Fang,Houk, Kendall N.,Newman, Stephen G.
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supporting information
p. 1311 - 1318
(2017/05/16)
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- Nickel-Catalyzed Negishi Cross-Coupling of N -Acylsuccinimides: Stable, Amide-Based, Twist-Controlled Acyl-Transfer Reagents via N-C Activation
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This paper reports a room temperature, nickel-catalyzed Negishi cross-coupling of N -acylsuccinimides with arylzinc reagents via selective N-C bond cleavage enabled by amide bond twist. The reaction proceeds using a commercially available, air-stable Ni(II) precatalyst in the absence of additives under exceedingly mild conditions. Of broad interest, this report introduces N -acylsuccinimides as stable, crystalline, electrophilic, cost-effective, benign, amide-based acyl transfer reagents via acyl metal intermediates. The reaction selectivity is governed by half-twist of the amide bond in N -acylsuccinimides, thus opening the door for applications in metal-catalyzed manifolds via redox-neutral reaction pathways tuneable by amide bond distortion.
- Shi, Shicheng,Szostak, Michal
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supporting information
p. 3602 - 3608
(2017/08/15)
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- Palladium-Catalyzed Denitrogenative Synthesis of Aryl Ketones from Arylhydrazines and Nitriles Using O2 as Sole Oxidant
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An efficient and simple palladium-catalyzed approach for the synthesis of aryl ketones from low-cost nitriles and arylhydrazines using molecular oxygen (O2) as sole oxidant via C-N bond cleavage is reported. Various aryl ketones were synthesized in moderate to good yields under mild conditions. A possible mechanism involving the PdII/Pd0 catalytic cycle process is depicted, and a cationic palladium intermediate was detected by ESI-MS.
- Wang, Xu,Huang, Yubing,Xu, Yanli,Tang, Xiaodong,Wu, Wanqing,Jiang, Huanfeng
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p. 2211 - 2218
(2017/02/26)
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- Ni-Catalyzed cross-coupling reactions of N-acylpyrrole-type amides with organoboron reagents
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The catalytic conversion of amides to ketones is highly desirable yet challenging in organic synthesis. We herein report the first Ni/bis-NHC-catalyzed cross-coupling of N-acylpyrrole-type amides with arylboronic esters to obtain diarylketones. This method is facilitated by a new chelating bis-NHC ligand. The reaction tolerates diverse functional groups on both arylamide and arylboronic ester partners including sensitive ester and ketone groups.
- Huang, Pei-Qiang,Chen, Hang
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p. 12584 - 12587
(2017/11/30)
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- Iron-Catalyzed Acylation of Polyfunctionalized Aryl- and Benzylzinc Halides with Acid Chlorides
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FeCl2 (5 mol %) catalyzes a smooth and convenient acylation of functionalized arylzinc halides at 50 °C (2-4 h) and benzylic zinc chlorides at 25 °C (0.5-4 h) with a variety of acid chlorides leading to polyfunctionalized diaryl and aryl heteroaryl ketones.
- Benischke, Andreas D.,Leroux, Marcel,Knoll, Irina,Knochel, Paul
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supporting information
p. 3626 - 3629
(2016/08/16)
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- Efficient Synthesis of Diaryl Ketones by Nickel-Catalyzed Negishi Cross-Coupling of Amides by Carbon–Nitrogen Bond Cleavage at Room Temperature Accelerated by a Solvent Effect
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The first Negishi cross-coupling of amides for the synthesis of versatile diaryl ketones by selective C?N bond activation under exceedingly mild conditions is reported. The cross-coupling was accomplished with bench-stable, inexpensive precatalyst [Ni(PPh3)2Cl2] that shows high functional-group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N?C bond activation accomplished to date (room temperature, 10 min). Considering the versatile role of polyfunctional biaryl ketone linchpins in modern organic synthesis, availability, and excellent functional-group tolerance of organozinc reagents, this strategy provides a new platform for amide N?C bond/organozinc cross-coupling under mild conditions.
- Shi, Shicheng,Szostak, Michal
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p. 10420 - 10424
(2016/07/21)
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- Chemoselective Transformation of Diarylethanones to Arylmethanoic Acids and Diarylmethanones and Mechanistic Insights
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The chemoselective transformation of diarylethanones via either aerobic oxidative cleavage to give arylmethanoic acids or tandem aerobic oxidation/benzilic acid rearrangement/decarboxylation to give diarylmethanones has been developed. The transformation is controllable and applicable to a broad spectrum of substrates and affords the desired products in good to excellent yields. Mechanistic insights with control reactions, 1H NMR tracking, and single-crystal X-ray diffraction reveal a complex mechanistic network in which two common intermediates, α-ketohydroperoxide and diarylethanedione, and three plausible pathways are proposed and verified. These pathways are interlinked and can be switched reasonably by changing the reaction conditions. This method enables scalable synthesis and access to a number of valuable compounds, including vitamin B3, diphenic acid, and the nonsteroidal anti-inflammatory drug ketoprofen. The present protocol represents a step forward in exploiting complex mechanistic networks to control reaction pathways, achieving divergent syntheses from the same class of starting materials.
- Wang, Xing,Chen, Rui-Xi,Wei, Zeng-Feng,Zhang, Chen-Yang,Tu, Hai-Yang,Zhang, Ai-Dong
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p. 238 - 249
(2016/01/15)
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- Nickel-Catalyzed Decarbonylative Coupling of Aryl Esters and Arylboronic Acids
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A variety of functionalized biaryls can be accessed by coupling aryl and heteroaryl esters with boronic acids in Suzuki-Miyaura-type decarbonylative cross-coupling catalyzed by an affordable catalyst system composed of Ni(cod)2 and PCy3. The methodology is tolerant of a variety of functional groups and presents an attractive alternative to the use of palladium catalysis currently used in industry to acquire such bis(hetero)aryls, but also reveals challenges associated with nickel catalysis of esters in cross-coupling chemistry.
- Laberge, Nicole A.,Love, Jennifer A.
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supporting information
p. 5546 - 5553
(2015/09/01)
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- Dirhodium(II)-Catalyzed Cross-Coupling Reactions of Aryl Aldehydes with Arylboronic Acids in Water
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In this report, dirhodium(II) catalysts with axial phosphanes ligands were employed to catalyze cross-coupling reactions of aromatic aldehydes with arylboronic acids to generate ketones in neat water. The overall reaction is proposed to occur through a cascade process involving the dirhodium-catalyzed addition of boronic acids to aldehydes followed by the dehydrogenative oxidation of alcohols.
- Kuang, Yi,Wang, Yuanhua
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supporting information
p. 1163 - 1166
(2015/10/05)
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- Iridium-catalyzed direct C-H amidation with weakly coordinating carbonyl directing groups under mild conditions
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An iridium-catalyzed direct C-H amidation of weakly coordinating substrates, in particular of those bearing ester and ketone groups, under very mild conditions has been developed. The observed high reaction efficiency was achieved by the combined use of acetic acid and lithium carbonate as additives. Copyright
- Kim, Jinwoo,Chang, Sukbok
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supporting information
p. 2203 - 2207
(2014/03/21)
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- Practical one-pot preparation of ketones from aryl and alkyl bromides with aldehydes and DIH via Grignard reagents
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Various diaryl ketones, alkyl aryl ketones, and dialkyl ketones were efficiently prepared in good yields by the reactions of the Grignard reagents derived from aryl or alkyl bromides, followed by the reactions with aromatic or aliphatic aldehydes and the subsequent treatment with 1,3-diiodo-5,5- dimethylhydantoin and K2CO3, in a one-pot method. The same treatment of aromatic bromides bearing electron-withdrawing groups, such as ester, nitrile, ketone, and nitro groups with i-PrMgCl·LiCl or PhMgCl instead of Mg, also provided the corresponding diaryl and alkyl aryl ketones in good yields. The above methods are simple and practical transition-metal-free methods for the preparation of various diaryl ketones and alkyl aryl ketones bearing electron-rich aromatic groups and electron-deficient aromatic groups, as well as dialkyl ketones.
- Dohi, Souya,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 6557 - 6564
(2012/08/27)
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- Photochemically promoted transition metal-free cross-coupling of acylsilanes with organoboronic esters
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Intermolecular carbon-carbon bond formation between acylsilanes and organoboronic esters was achieved by photoirradiation under almost neutral, transition metal-free conditions. In this reaction, siloxycarbenes generated by photoisomerization of acylsilanes reacted with boronic esters to give the formal B-C bond insertion intermediates, which underwent unique rearrangement to afford the cyclic α-alkoxyboronic esters. Acidic treatment of the resulting crude products under air furnished the cross-coupled ketones in good yields.
- Ito, Kazuta,Tamashima, Hiroto,Iwasawa, Nobuharu,Kusama, Hiroyuki
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p. 3716 - 3719
(2011/05/14)
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- Synthesis of arylketones by ruthenium-catalyzed cross-coupling of aldehydes with arylboronic acids
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The first ruthenium-catalyzed cross-coupling of aldehydes with arylboronic acids is reported. Various aliphatic and aromatic aldehydes are transformed to the corresponding arylketones. A total of 31 examples with moderate to excellent yields are presented, together with the results of an initial mechanistic investigation.
- Li, Hong,Xu, Yuan,Shi, Erbo,Wei, Wei,Suo, Xiangqiang,Wan, Xiaobing
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supporting information; experimental part
p. 7880 - 7882
(2011/08/06)
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- Tandem catalysis: Access to ketones from aldehydes and arylboronic acids via rhodium-catalyzed addition/oxidation
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Direct cross-coupling reactions of aromatic aldehydes with arylboronic acids afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst, acetone and a base. This new reaction, involving a formal aldehyde C-H bond activation, is believed to proceed via a tandem process involving addition of the organometallic species to the aldehyde followed by oxidation by β-hydride transfer.
- Mora, Guilhem,Darses, Sylvain,Genet, Jean-Pierre
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p. 1180 - 1184
(2008/09/16)
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- Stereoelectronic and solvent effects on the allylic oxyfunctionalization of alkenes with singlet oxygen
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The factors that control the stereochemistry of sensitized photooxygenation of alkenes via singlet oxygen (ene reaction) are selectively reported. We also introduce our most recent stereoelectronic effects on the singlet oxygen-ene reaction. The origin of
- Alberti, Mariza N.,Orfanopoulos, Michael
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p. 10660 - 10675
(2007/10/03)
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- Application of the catalytic friedel-crafts acylation reaction and regioselectivity correlations
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A correlation was found between electronic properties and regioselectivity in the Friedel-Crafts reaction of substituted phenylacetic and benzoic acids with anisole, utilising substoichiometric (down to 1 mol%) amounts of catalyst. Relative reactivities of selected catalysts for this reaction were also studied. Georg Thieme Verlag Stuttgart.
- Wilkinson, Mark C.,Saez, Fabienne,Wei, Lee Hon
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p. 1063 - 1066
(2007/10/03)
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- Ruthenium-catalyzed coupling of aldimines with arylboronates: New synthetic method for aromatic ketones
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Using the chelation strategy, the reaction of aldimines bearing the 3-picolin-2-yl group with various arylboronates in the presence of a ruthenium catalyst furnished the corresponding ketimines in high yields for a short reaction time; the resulting ketimines were readily converted to ketones by hydrolysis. The Royal Society of Chemistry 2005.
- Park, Young Jun,Jo, Eun-Ae,Jun, Chul-Ho
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p. 1185 - 1187
(2007/10/03)
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- Spectral properties and reactivity of diarylmethanol radical cations in aqueous solution. Evidence for intramolecular charge resonance
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Spectral properties and reactivities of ring-methoxylated diarylmethane and diarylmethanol radical cations, generated in aqueous solution by pulse and γ-radiolysis and by the one-electron chemical oxidant potassium 12-tungstocobalt(III)ate, have been studied. The radical cations display three bands in the UV, visible, and vis-NIR regions of the spectrum. The vis-NIR band is assigned to an intramolecular charge resonance interaction (CR) between the neutral donor and charged acceptor rings, as indicated by the observation that the relative intensity of the vis-NIR band compared to that of the UV and visible bands does not increase with increasing substrate concentration and that the position and intensity of this band is influenced by the ring-substitution pattern. In acidic solution (pH = 4), monomethoxylated diarylmethanol radical cations 1a.+-1e.+ decay by Ca-H deprotonation [k = (1.7-1.9) x 104 S-1] through the intermediacy of a ketyl radical, which is further oxidized in the reaction medium to give the corresponding benzophenones, as evidenced by both time-resolved spectroscopic and product studies. With the dimethoxylated radical cation 2.+, Ca-H deprotonation is instead significantly slower (k = 6.7 × 102 s-1). In basic solution, 1.+-1e.+ undergo -OH-induced deprotonation from the α-OH group with kOH ≈ 1.4 × 1010 M-1 s-1, leading to a ketyl radical anion, which is oxidized in the reaction medium to the corresponding benzophenone.
- Bietti, Massimo,Lanzalunga, Osvaldo
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p. 2632 - 2638
(2007/10/03)
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- The nature of the transition state in diarylmethyl cation - Nucleophile combination reactions as probed by secondary α-deuterium isotope effects
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Transition-state structures for the carbocation-nucleophile combination reactions of (4-substituted-4′-methoxydiphenyl)methyl cations with water, chloride, and bromide ions in acetonitrile-water mixtures have been investigated by measuring the secondary α-deuterium kinetic and equilibrium isotope effects. Rate constants in the combination direction were measured with laser flash photolysis. Equilibrium constants were measured for the water reaction by a comparison method in moderately concentrated sulfuric acid solutions, for the bromide reaction via the observation of reversible combination, and for the chloride reaction from the ratio of the combination rate constant and the rate constant for the ionization of the diarylmethyl chloride product. The fraction of bond making in the transition state has been calculated as the ratio log (kinetic isotope effect):log (equilibrium isotope effect). For the water reaction, there is 50-65% bond making in the transition state; this is also true for cations that are many orders of magnitude less reactive. The same conclusions, 50-65% bond formation in the transition state independent of reactivity, have previously been made in corre-lations of log kw vs. log KR. Thus, two quite different measures of transition structure provide the same result. The kH:kD values for the halide combinations in 100% acetonitrile are within experimental error of unity. This is consistent with suggestions that these reactions are occurring with diffusional encounter as the rate-limiting step. Addition of water has a dramatic retarding effect on the halide reactions, with rate constants decreasing steadily with increased water content. Small inverse kinetic isotope effects are observed (in 20% acetonitrile:80% water) indicating that carbon-halogen bond formation is rate-limiting. Comparison of the kinetic and equilibrium isotope effects shows ~25 and ~40% bond formation in the transition states for the reactions with bromide and chloride, respectively.
- Van Pham, Thuy,McClelland, Robert A.
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p. 1887 - 1897
(2007/10/03)
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- Merostabilization in radical ions, triplets, and biradicals. 4. Substituent effects on the half-wave reduction potentials and n, ?* triplet energies of aromatic ketones
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The half-wave reduction potentials, measured by cyclic voltammetry, and n, ?* triplet energies, measured by phosphorescence spectroscopy, were determined for a series of eighteen symmetrically and unsymmetrically substituted benzophenones.Attempts are made to correlate the results with Hammett substituent constants.Better correlations are observed when the data are correlated with a two-parameter function consisting of Hammett substituent constants and a set of substituent parameters describing variations in free radical stability.Significant deviations from "normal" behaviour are observed for benzophenones substituted by both electron-donating and electron-withdrawing substituents.These deviations are attributed to merostabilization of the radical-like species, and an empirical approach designed to evaluate the importance of this effect is developed.Ab initio calculations of molecular orbital energies in meta- and para-substituted benzaldehydes are used to evaluate the substituent effects on E1/2red and ETn,?* in terms of the effect on the energies of the n- and ?*-orbitals.
- Leigh, William J.,Arnold, Donald R.,Humphreys, Robert W. R.,Wong, Po Cheong
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p. 2537 - 2549
(2007/10/02)
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