- Aromatization as an Impetus to Harness Ketones for Metallaphotoredox-Catalyzed Benzoylation/Benzylation of (Hetero)arenes
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Herein we report ketones as feedstock materials in radical cross-coupling reactions under Ni/photoredox dual catalysis. In this approach, simple condensation first converts ketones into prearomatic intermediates that then act as activated radical sources for cross-coupling with aryl halides. Our strategy enables the direct benzylation/benzoylation of (hetero)arenes under mild reaction conditions with high functional group tolerance.
- Lee, Shao-Chi,Li, Li-Yun,Tsai, Zong-Nan,Lee, Yi-Hsin,Tsao, Yong-Ting,Huang, Pin-Gong,Cheng, Cheng-Ku,Lin, Heng-Bo,Chen, Ting-Wei,Yang, Chung-Hsin,Chiu, Cheng-Chau,Liao, Hsuan-Hung
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- Desulfurative Ni-Catalyzed Reductive Cross-Coupling of Benzyl Mercaptans/Mercaptoacetates with Aryl Halides
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The C-S activation and sulfur removal from native thiols is challenging, which limits their application as feedstock materials in organic synthesis despite their natural abundance. Herein, we introduce a per-/polyfluoroaryl moiety, which serves as a redox-active scaffold, into sp3-hybridized thiols to activate the C-S bond. Using a Ni catalyst with MgBr2 as an additive, the S group can be removed to yield an aliphatic radical that can react with an aryl halide in a reductive cross-coupling.
- Chan, Cheng-Lin,Hsu, Che-Ming,Lee, Shao-Chi,Li, Li-Yun,Liao, Hsuan-Hung,Mi?oza, Shinje,Tsai, Hao-En,Tsai, Zong-Nan,Tsao, Yong-Ting
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- Selective electrochemical oxidation of aromatic hydrocarbons and preparation of mono/multi-carbonyl compounds
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A selective electrochemical oxidation was developed under mild condition. Various mono-carbonyl and multi-carbonyl compounds can be prepared from different aromatic hydrocarbons with moderate to excellent yield and selectivity by virtue of this electrochemical oxidation. The produced carbonyl compounds can be further transformed into α-ketoamides, homoallylic alcohols and oximes in a one-pot reaction. In particular, a series of α-ketoamides were prepared in a one-pot continuous electrolysis. Mechanistic studies showed that 2,2,2-trifluoroethan-1-ol (TFE) can interact with catalyst species and generate the corresponding hydrogen-bonding complex to enhance the electrochemical oxidation performance. [Figure not available: see fulltext.]
- Li, Zhibin,Zhang, Yan,Li, Kuiliang,Zhou, Zhenghong,Zha, Zhenggen,Wang, Zhiyong
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p. 2134 - 2141
(2021/09/29)
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- A general copper-catalyzed radical C(sp3)?C(sp2) cross-coupling to access 1,1-diarylalkanes under ambient conditions
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A general copper-catalyzed C(sp3)?C(sp2) cross-coupling of (hetero)benzyl bromides with the air- and moisture-stable aryl nucleophiles has been developed, providing a facile access to pharmaceutically useful 1,1-di(hetero)arylalkane and 1-aryl-1-heteroarylalkane scaffolds. Critical to the success is the utilization of a proline-based N,N,P-ligand to enhance the reducing capability of copper, thus easily converting benzyl bromides to the corresponding radical species via a single-electron transfer process under ambient conditions. The reaction features a broad substrate scope, covering (hetero)arylboronate esters, oxadiazoles, and benzo[d]oxazoles, as well as primary and secondary (hetero)benzyl bromides with excellent functional group tolerance.
- Su, Xiao-Long,Jiang, Sheng-Peng,Ye, Liu,Xu, Guo-Xing,Chen, Ji-Jun,Gu, Qiang-Shuai,Li, Zhong-Liang,Liu, Xin-Yuan
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supporting information
(2021/05/06)
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- Nickel-Catalyzed Electrochemical C(sp3)?C(sp2) Cross-Coupling Reactions of Benzyl Trifluoroborate and Organic Halides**
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Reported here is the redox neutral electrochemical C(sp2)?C(sp3) cross-coupling reaction of bench-stable aryl halides or β-bromostyrene (electrophiles) and benzylic trifluoroborates (nucleophiles) using nonprecious, bench-stable NiCl2?glyme/polypyridine catalysts in an undivided cell configuration under ambient conditions. The broad reaction scope and good yields of the Ni-catalyzed electrochemical coupling reactions were confirmed by 50 examples of aryl/β-styrenyl chloride/bromide and benzylic trifluoroborates. Potential applications were demonstrated by electrosynthesis and late-stage functionalization of pharmaceuticals and natural amino acid modification, and three reactions were run on gram-scale in a flow-cell electrolyzer. The electrochemical C?C cross-coupling reactions proceed through an unconventional radical transmetalation mechanism. This method is highly productive and expected to find wide-spread applications in organic synthesis.
- Luo, Jian,Hu, Bo,Wu, Wenda,Hu, Maowei,Liu, T. Leo
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p. 6107 - 6116
(2021/02/01)
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- Remote Nickel-Catalyzed Cross-Coupling Arylation via Proton-Coupled Electron Transfer-Enabled C-C Bond Cleavage
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Cross-coupling reactions for carbon-carbon and carbon-heteroatom bond formation are of great importance in modern chemical synthesis. In addition to classical cross-couplings involving preformed or preactivated coupling partners, more recently breakthroughs have been made in the selective, direct coupling of abundant aliphatic carbon-hydrogen bonds using hydrogen atom transfer reactions in which the bond-dissociation energy is the thermodynamic driving force. The more challenging carbon-carbon bond activation is still rather underdeveloped due to the bond inertness. Herein, we report a mild and general strategy for the activation of a diverse set of readily available cyclic alcohols for the remote and site-specific arylation of ketones via the combination of photoredox-mediated multisite concerted proton-electron transfer (MS-PCET) and nickel catalysis. The current cross-coupling proceeds with the generation of an alkoxy radical utilizing bond-dissociation free energy (BDFE) as the thermodynamic driving force. Subsequently, the resulting remote carbon-centered radicals formed by C-C cleavage merge with the nickel catalytic cycle to create the challenging C(sp3)-C(sp2) bonds.
- Huang, Long,Ji, Tengfei,Rueping, Magnus
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supporting information
p. 3532 - 3539
(2020/02/25)
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- Generation of Alkyl Radical through Direct Excitation of Boracene-Based Alkylborate
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The generation of tertiary, secondary, and primary alkyl radicals has been achieved by the direct visible-light excitation of a boracene-based alkylborate. This system is based on the photophysical properties of the organoboron molecule. The protocol is applicable to decyanoalkylation, Giese addition, and nickel-catalyzed carbon-carbon bond formations such as alkyl-aryl cross-coupling or vicinal alkylarylation of alkenes, enabling the introduction of various C(sp3) fragments to organic molecules.
- Hashizume, Daisuke,Hosoya, Takamitsu,Nakamura, Kei,Ohmiya, Hirohisa,Sato, Yukiya,Sumida, Yuto
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supporting information
p. 9938 - 9943
(2020/06/27)
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- Photo-Ni-Dual-Catalytic C(sp2)-C(sp3) Cross-Coupling Reactions with Mesoporous Graphitic Carbon Nitride as a Heterogeneous Organic Semiconductor Photocatalyst
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The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp2)-C(sp3) cross-co
- Antonietti, Markus,Ghosh, Indrajit,K?nig, Burkhard,Khamrai, Jagadish,Savateev, Aleksandr
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p. 3526 - 3532
(2020/04/09)
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- Nickel catalysis enables convergent paired electrolysis for direct arylation of benzylic C-H bonds
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Convergent paired electrosynthesis is an energy-efficient approach in organic synthesis; however, it is limited by the difficulty to match the innate redox properties of reaction partners. Here we use nickel catalysis to cross-couple the two intermediates
- Hu, Xile,Zhang, Lei
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p. 10786 - 10791
(2020/10/26)
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- Visible Light-Catalyzed Benzylic C-H Bond Chlorination by a Combination of Organic Dye (Acr+-Mes) and N-Chlorosuccinimide
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By combining "N-chlorosuccinimide (NCS)"as the safe chlorine source with "Acr+-Mes"as the photocatalyst, we successfully achieved benzylic C-H bond chlorination under visible light irradiation. Furthermore, benzylic chlorides could be converted to benzylic ethers smoothly in a one-pot manner by adding sodium methoxide. This mild and scalable chlorination method worked effectively for diverse toluene derivatives, especially for electron-deficient substrates. Careful mechanistic studies supported that NCS provided a hydrogen abstractor "N-centered succinimidyl radical,"which was responsible for the cleavage of the benzylic C-H bond, relying on the reducing ability of Acr?-Mes.
- Xiang, Ming,Zhou, Chao,Yang, Xiu-Long,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
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p. 9080 - 9087
(2020/08/14)
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- Metal-organic layers as multifunctional two-dimensional nanomaterials for enhanced photoredox catalysis
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Metal-organic layers (MOLs) have recently emerged as a novel class of molecular two-dimensional (2D) materials with significant potential for catalytic applications. Herein we report the design of a new multifunctional MOL, Hf12-Ir-Ni, by laterally linking Hf12 secondary building units (SBUs) with photosensitizing Ir(DBB)[dF(CF3)ppy]2+ [DBB-Ir-F, DBB = 4,4′-di(4-benzoato)-2,2′-bipyridine; dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine] bridging ligands and vertically terminating the SBUs with catalytic Ni(MBA)Cl2 [MBA = 2-(4′-methyl-[2,2′-bipyridin]-4-yl)acetate] capping agents. Hf12-Ir-Ni was synthesized in a bottom-up approach and characterized by TEM, AFM, PXRD, TGA, NMR, ICP-MS, UV-vis, and luminescence spectroscopy. The proximity between photosensitizing Ir centers and catalytic Ni centers (～0.85 nm) in Hf12-Ir-Ni facilitates single electron transfer, leading to a 15-fold increase in photoredox reactivity. Hf12-Ir-Ni was highly effective in catalytic C-S, C-O, and C-C cross-coupling reactions with broad substrate scopes and turnover numbers of ～4500, ～1900, and ～450, respectively.
- Lan, Guangxu,Quan, Yangjian,Wang, Maolin,Nash, Geoffrey T.,You, Eric,Song, Yang,Veroneau, Samuel S.,Jiang, Xiaomin,Lin, Wenbin
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supporting information
p. 15767 - 15772
(2019/10/11)
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- The Dual Role of Benzophenone in Visible-Light/Nickel Photoredox-Catalyzed C?H Arylations: Hydrogen-Atom Transfer and Energy Transfer
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A dual catalytic protocol for the direct arylation of non-activated C(sp3)?H bonds has been developed. Upon photochemical excitation, the excited triplet state of a diaryl ketone photosensitizer abstracts a hydrogen atom from an aliphatic C?H bond. This inherent reactivity was exploited for the generation of benzylic radicals which subsequently enter a nickel catalytic cycle, accomplishing the benzylic arylation.
- Dewanji, Abhishek,Krach, Patricia E.,Rueping, Magnus
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supporting information
p. 3566 - 3570
(2019/02/26)
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- Construction of Di(hetero)arylmethanes Through Pd-Catalyzed Direct Dehydroxylative Cross-Coupling of Benzylic Alcohols and Aryl Boronic Acids Mediated by Sulfuryl Fluoride (SO2F2)
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A practical Pd-catalyzed direct dehydroxylative coupling of (hetero)benzylic alcohols with (hetero)arylboronic acids for the constructions of di(hetero)arylmethane derivatives under SO2F2 was described. This new method provided a strategically distinct approach to di(hetero)arylmethane derivatives from readily available and abundant benzylic alcohols under mild condition.
- Zhao, Chuang,Zha, Gao-Feng,Fang, Wan-Yin,Rakesh,Qin, Hua-Li
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supporting information
p. 1801 - 1807
(2019/02/07)
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- An Efficient Ga(OTf)3/Isopropanol Catalytic System for Direct Reduction of Benzylic Alcohols
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This study aims to report the first gallium-catalyzed direct reduction of benzylic alcohols using isopropanol as a reductant. The reaction proceeds via gallium catalyst-assisted hydride transfer of the in situ-generated benzylic isopropyl ether. The method generates only water and acetone as byproducts and thus provides an atom-economic and environmentally friendly approach to the synthesis of di- and triarylmethanes, which are important substructures in various bioactive compounds and functional materials. (Figure presented.).
- Sai, Masahiro
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p. 4330 - 4335
(2018/10/15)
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- Modular Functionalization of Arenes in a Triply Selective Sequence: Rapid C(sp2) and C(sp3) Coupling of C?Br, C?OTf, and C?Cl Bonds Enabled by a Single Palladium(I) Dimer
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Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0-catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C?Br-selective functionalization in the presence of C?OTf and C?Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C?OTf bonds (in I dimer. This allowed the realization of the first general and triply selective sequential C?C coupling (in 2D and 3D space) of C?Br followed by C?OTf and then C?Cl bonds.
- Keaveney, Sinead T.,Kundu, Gourab,Schoenebeck, Franziska
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supporting information
p. 12573 - 12577
(2018/09/18)
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- Cobalt-Catalyzed Formation of Functionalized Diarylmethanes from Benzylmesylates and Aryl Halides
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A simple cobalt-catalyzed reductive coupling protocol allowing the synthesis of functionalized diarylmethanes from benzyl mesylate is described. The possibility to directly use the benzyl alcohol as a result of a two-step reaction is also presented. This method tolerates a variety of functional groups. A benzyl radical is likely involved. (Figure presented.).
- Reddy, Bhoomireddy Rajendra Prasad,Chowdhury, Sushobhan,Auffrant, Audrey,Gosmini, Corinne
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p. 3026 - 3029
(2018/08/24)
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- Synthesis of bench-stable solid triorganoindium reagents and reactivity in palladium-catalyzed cross-coupling reactions
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Bench-stable solid triorganoindium compounds have been prepared by coordination with 4-(dimethylamino)pyridine (DMAP). The solid R3In(DMAP) complexes are obtained from the corresponding solution of R3In in quantitative yield and can
- Gil-Negrete, José M.,Pérez Sestelo, José,Sarandeses, Luis A.
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supporting information
p. 1453 - 1456
(2018/02/19)
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- Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes
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A Cu-catalyzed method has been identified for selective oxidative arylation of benzylic C-H bonds with arylboronic esters. The resulting 1,1-diarylalkanes are accessed directly from inexpensive alkylarenes containing primary and secondary benzylic C-H bonds, such as toluene or ethylbenzene. All catalyst components are commercially available at low cost, and the arylboronic esters are either commercially available or easily accessible from the commercially available boronic acids. The potential utility of these methods in medicinal chemistry applications is highlighted.
- Vasilopoulos, Aristidis,Zultanski, Susan L.,Stahl, Shannon S.
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p. 7705 - 7708
(2017/06/20)
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- Synthesis of Di- and Triarylmethanes through Palladium-Catalyzed Reductive Coupling of N -Tosylhydrazones and Aryl Bromides
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A palladium-catalyzed reductive coupling between N-tosylhydrazones and aryl bromides has been developed. The reaction provides an efficient method for the synthesis of diarylmethanes and triarylmethanes via the formation of C(sp2)-C(sp3) single bonds. This new methodology for the synthesis of diarylmethanes and triarylmethanes is featured by the ready availability of the starting materials, mild reaction conditions, and the tolerance of wide range of functional groups. The reaction follows a pathway including palladium carbene formation, migratory insertion, and reduction of the alkylpalladium(II) intermediate.
- Xia, Yamu,Hu, Fangdong,Xia, Ying,Liu, Zhenxing,Ye, Fei,Zhang, Yan,Wang, Jianbo
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p. 1073 - 1086
(2017/02/24)
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- Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes
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Herein, chiral Mn–aminopyridine complexes have been shown to catalyze the oxidation of alkylarenes to enantiomerically enriched 1-arylalkanols with hydrogen peroxide. The observed enantiomeric excess values result from the direct enantioselective benzylic C?H hydroxylation, accompanied by stereoconvergent oxidative kinetic resolution of the resulting alcohol. Testing several (S,S)-bipyrrolidine derived Mn complexes has revealed a novel catalyst (6) that exhibits the best kinetic resolution in the series (krel up to 8.8), along with sufficient reactivity and efficiency (>1000 catalytic turnovers). The mechanistic study of the Mn-mediated alcohol oxidation witnesses electrophilic active species (ρ=?1.2), with rate-limiting H abstraction (kH/kD=2.2), followed by oxygen rebound and dehydration of the resulting gem-diol to form the ketone. Intriguingly, while for the resolution of the relatively bulky 1,2-diphenylethanol, krel is virtually constant throughout the reaction, for less bulky alcohols, krel increases with increasing conversion, in line with the rising optical purity of the 1-arylalkanol. The latter participates in the oxidation as an auxiliary ligand, assisting the chiral recognition. This effect is related to the previously described asymmetric autocatalysis and asymmetric autoinduction, but is not identical with either of those, with the differences being discussed. To unambiguously identify this effect, the term asymmetric autoamplification (chiral autoamplification) is proposed.
- Talsi, Evgenii P.,Samsonenko, Denis G.,Bryliakov, Konstantin P.
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p. 2599 - 2607
(2017/07/12)
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- One-pot borylation/Suzuki-Miyaura sp2-sp3 cross-coupling
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We describe the first one-pot borylation/Suzuki-Miyaura sp2-sp3 cross-coupling between readily available aryl (pseudo)halides and activated alkyl chlorides. This method streamlines the synthesis of diaryl methanes, α-aryl carbonyls and allyl aryl compounds, substructures that are commonly found in life changing drug molecules.
- Whitaker, Luke,Harb, Hassan Y.,Pulis, Alexander P.
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p. 9364 - 9367
(2017/08/23)
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- Synthesis of zwitterionic palladium complexes and their application as catalysts in cross-coupling reactions of aryl, heteroaryl and benzyl bromides with organoboron reagents in neat water
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N-(3-Chloro-2-quinoxalinyl)-N′-arylimidazolium salts (aryl = 2,6-diisopropylphenyl [HL1Cl]Cl, aryl = mesityl [HL2Cl]Cl) have been synthesized by treating 2,3-dichloroquinoxaline with the corresponding N′-arylimidazole in neat water. Facile reactions of these imidazolium salts with Pd(PPh3)4 and Pd2(dba)3/PPh3 (dba = dibenzyledene acetone) at 50 °C have afforded zwitterionic palladium(ii) complexes [Pd(HL1)(PPh3)Cl2] (I) and [Pd(HL2)(PPh3)Cl2] (II) in excellent yields. I and II have been tested for their ability to catalyze Suzuki-Miyaura cross coupling (SMC) reactions in neat water/K2CO3 and are found to be highly active for carrying out these reactions between aryl bromides and organoboron reagents. Furthermore, the scope of the catalyst I was also examined by employing (hetero)aryl bromides, hydrophilic aryl bromides, benzyl bromides and various organoboron reagents. More than 80 aryl/benzyl bromide-arylboronic acid combinations were screened in neat water/K2CO3 and it was found that I was a versatile catalyst, which produced biaryls/diarylmethanes in excellent yields. A TON of 82 000 was achieved by using I. Studies on the mechanism have also been carried out to investigate the involvement of carbene complexes in the catalytic path. Poison tests and a two-phase test were also conducted and the results are reported.
- Ramakrishna,Dastagiri Reddy
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p. 8598 - 8610
(2017/07/12)
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- Phenol Derivatives as Coupling Partners with Alkylsilicates in Photoredox/Nickel Dual Catalysis
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Photoredox/nickel dual catalysis via single electron transmetalation allows coupling of Csp3-Csp2 hybridized centers under mild conditions. A procedure for the coupling of electron-deficient aryl triflates, -tosylates, and -mesylates with alkylbis(catecholato)silicates is presented. This method represents the first example of the use of phenol derivatives as electrophilic coupling partners in photoredox/nickel dual catalysis.
- Patel, Niki R.,Molander, Gary A.
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supporting information
p. 7271 - 7275
(2016/08/30)
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- Direct C(sp3)-H Cross Coupling Enabled by Catalytic Generation of Chlorine Radicals
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Here we report the development of a C(sp3)-H cross-coupling platform enabled by the catalytic generation of chlorine radicals by nickel and photoredox catalysis. Aryl chlorides serve as both cross-coupling partners and the chlorine radical source for the α-oxy C(sp3)-H arylation of cyclic and acyclic ethers. Mechanistic studies suggest that photolysis of a Ni(III) aryl chloride intermediate, generated by photoredox-mediated single-electron oxidation, leads to elimination of a chlorine radical in what amounts to the sequential capture of two photons. Arylations of a benzylic C(sp3)-H bond of toluene and a completely unactivated C(sp3)-H bond of cyclohexane demonstrate the broad implications of this manifold for accomplishing numerous C(sp3)-H bond functionalizations under exceptionally mild conditions.
- Shields, Benjamin J.,Doyle, Abigail G.
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supporting information
p. 12719 - 12722
(2016/10/13)
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- Nickel-Catalyzed Cross-Electrophile Coupling with Organic Reductants in Non-Amide Solvents
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Cross-electrophile coupling of aryl halides with alkyl halides has thus far been primarily conducted with stoichiometric metallic reductants in amide solvents. This report demonstrates that the use of tetrakis(dimethylamino)ethylene (TDAE) as an organic reductant enables the use of non-amide solvents, such as acetonitrile or propylene oxide, for the coupling of benzyl chlorides and alkyl iodides with aryl halides. Furthermore, these conditions work for several electron-poor heterocycles that are easily reduced by manganese. Finally, we demonstrate that TDAE addition can be used as a control element to ‘hold’ a reaction without diminishing yield or catalyst activity.
- Anka-Lufford, Lukiana L.,Huihui, Kierra M. M.,Gower, Nicholas J.,Ackerman, Laura K. G.,Weix, Daniel J.
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supporting information
p. 11564 - 11567
(2016/08/05)
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- Cobalt-Catalyzed Reductive Cross-Coupling Between Benzyl Chlorides and Aryl Halides
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A new protocol for the direct reductive cobalt-catalyzed arylation of benzyl chlorides has been developed in order to form functionalized diarylmethanes. A variety of reactive groups either on the aryl or the benzyl halide was employed. This represents the first cobalt-catalyzed reductive cross-coupling which does not require any ligand and pyridine. A reaction pathway is proposed involving a radical benzyl species. (Figure presented.).
- Pal, Suman,Chowdhury, Sushobhan,Rozwadowski, Elodie,Auffrant, Audrey,Gosmini, Corinne
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supporting information
p. 2431 - 2435
(2016/08/16)
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- Cobalt co-catalysis for cross-electrophile coupling: Diarylmethanes from benzyl mesylates and aryl halides
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The nickel-catalyzed cross-coupling of aryl halides with alkyl radicals derived from alkyl halides has recently been extended to couplings with carbon radicals generated by a co-catalyst. In this study, a new co-catalyst, cobalt phthalocyanine (Co(Pc)), is introduced and demonstrated to be effective for coupling substrates not prone to homolysis. This is because Co(Pc) reacts with electrophiles by an SN2 mechanism instead of by the electron-transfer or halogen abstraction mechanisms previously explored. Studies demonstrating the orthogonal reactivity of (bpy)Ni and Co(Pc), applying this selectivity to the coupling of benzyl mesylates with aryl halides, and the adaptation of these conditions to the less reactive benzyl phosphate ester and an enantioconvergent reaction are presented.
- Ackerman, Laura K. G.,Anka-Lufford, Lukiana L.,Naodovic, Marina,Weix, Daniel J.
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p. 1115 - 1119
(2015/02/05)
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- N-Heterocyclic carbene-palladium(II)-1-methylimidazole complex-catalyzed Suzuki-Miyaura coupling of benzyl carbamates with arylboronic acids
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The Suzuki-Miyaura coupling of benzyl carbamates with arylboronic acids was achieved in an environmentally benign medium. Using water as the sole solvent, such transformation took place very well to give the desired diarylmethane derivatives in good to almost quantitative yields in the presence of a well-defined NHC-Pd(ii)-Im complex under mild conditions. It is worth noting here that this is the first example of benzyl carbamates used in coupling reaction, thus affording a new method for the formation of diarylmethanes by palladium-catalyzed C-O bond activation.
- Wang, Xiao-Xia,Luo, Mao-Jun,Lu, Jian-Mei
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p. 11438 - 11444
(2015/12/04)
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- Visible light mediated efficient oxidative benzylic sp3 C-H to ketone derivatives obtained under mild conditions using O2
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A photooxygenation of benzylic sp3 C-H reaction has been demonstrated using O2 mediated by visible light. This protocol provides a simple and mild route to obtain ketones from benzylic sp3 C-H bonds. Various benzylic sp3 C-H bonds can be transformed into the desired ketone derivatives in moderate to good yields. The 18O2 labelling experiments demonstrated that the oxygen introduced into ketone originated from dioxygen. A plausible mechanism has been proposed accordingly.
- Yi, Hong,Bian, Changliang,Hu, Xia,Niu, Linbin,Lei, Aiwen
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supporting information
p. 14046 - 14049
(2015/09/15)
-
- Green photocatalytic organic transformations by polyoxometalates vs. mesoporous TiO2 nanoparticles: Selective aerobic oxidation of alcohols
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In this study, the catalytic activity of decatungstate (W10O324-) supported on mesoporous TiO2 nanoparticle assemblies (DT-MTA) was compared with that of homogeneous [Bu4N]4W10O32 catalysts under mild conditions. Our experiments showed that both catalytic systems achieve exceptionally high activity and selectivity under UV-visible light oxidation of various para-substituted aryl alcohols, using molecular oxygen as a "green" oxidant. The chemoselective transformation of aryl alcohols into the corresponding ketones was investigated with gas chromatography (GC) and NMR spectroscopy. Product analysis and kinetic results also indicated that these photooxidation reactions proceed via both electron transfer (ET) and hydrogen atom transfer (HAT) mechanisms over the DT-MTA catalyst, with the former one as the predominant, whereas a HAT route was adopted to account for the decatungstate homogeneous catalyzed reactions. This journal is
- Symeonidis, Theodoros S.,Tamiolakis, Ioannis,Armatas, Gerasimos S.,Lykakis, Ioannis N.
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p. 563 - 568
(2015/03/14)
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- METHOD OF SYNTHESIS MOLECULES USING CATALYST AND COMPOSITES THEREOF
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A method to synthesis molecules is provided. The method employs a catalyst for a cross- coupling react ion to obtain the molecule. The method comprises coupling boronic acid and halide in presence of the catalyst having graphite oxide supported palladium nanoparticles, a solvent and a base by heating. The heating is performed at a temperature lower than the temperature at which the graphite oxide deforms. The molecule is a biaryl. The method further provides obtaining complexs such as boscalid, telmisartan, valsartan, and SPPARMγ.
- -
-
Sheet 9/14; 10/14
(2014/11/13)
-
- Threefold and chemoselective couplings of triarylbismuths with benzylic chlorides and iodides using palladium catalysis
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This paper describes the palladium-catalyzed studies on threefold coupling of triarylbismuth reagents with benzylic chlorides and iodides. The optimized protocol conditions are operationally simple, delivering threefold coupling of a variety of triarylbismuths in combination with benzylic chlorides and iodides. The two optimized protocols allowed the synthesis of a diverse range of unsymmetrical diarylmethanes in an efficient manner. As part of this study, chemoselective transformation of benzylic chlorides and iodides was also achieved. This journal is the Partner Organisations 2014.
- Rao, Maddali L. N.,Dhanorkar, Ritesh J.
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p. 13134 - 13144
(2014/04/03)
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- Pd-catalyzed chemoselective threefold cross-coupling of triarylbismuths with benzylic bromides
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An efficient palladium-catalyzed protocol was demonstrated for the chemoselective cross-coupling of functionalized benzylic bromides with triarylbismuth reagents. Under the established conditions, catalyzed by palladium in the presence of K3PO
- Rao, Maddali L. N.,Dhanorkar, Ritesh J.
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p. 6794 - 6798
(2013/05/23)
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- Palladium nanoparticle catalysis: Borylation of aryl and benzyl halides and one-pot biaryl synthesis via sequential borylation-Suzuki-Miyaura coupling
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Palladium nanoparticles generated in PEG catalyze the reaction of bis(pinacolato)diboron with various aryl/benzyl halides to afford aryl/benzyl boronates in high yield. Arylboronates thus prepared, have been directly used in the Suzuki-Miyaura coupling reaction with different aryl halides and benzyl halides in a convenient one-pot, two-step solvent free green synthesis of unsymmetrical biaryls and diarylmethanes. The Royal Society of Chemistry 2012.
- Bej, Ansuman,Srimani, Dipankar,Sarkar, Amitabha
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experimental part
p. 661 - 667
(2012/05/04)
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- Suzuki-Miyaura cross-couplings of secondary allylic boronic esters
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Palladium-catalyzed cross-coupling reactions of secondary allylic boronic esters with iodoarenes were demonstrated under the conditions previously described for the coupling of benzylic substrates. The regioselectivity of the process was largely dictated by the pattern of olefin substitution. The Royal Society of Chemistry 2012.
- Glasspoole, Ben W.,Ghozati, Kazem,Moir, Jonathon W.,Crudden, Cathleen M.
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supporting information; experimental part
p. 1230 - 1232
(2012/02/15)
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- Palladium-catalyzed carbonylative coupling of benzyl chlorides with aryl boronic acids in aqueous media
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A novel chemoselective protocol for the carbonylative Suzuki coupling of benzyl chlorides with aryl boronic acids at low pressure of carbon monoxide has been developed. Applying a commercially available palladium acetate/PCy 3 catalyst system in the presence of potassium phosphate as the base and water as the solvent the coupling reactions proceeded smoothly. To demonstrate the general applicability 12 different α-arylated acetophenones have been synthesized in moderate to good yields (41-78%) under mild conditions.
- Wu, Xiao-Feng,Neumann, Helfried,Beller, Matthias
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experimental part
p. 6146 - 6149
(2010/12/24)
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- Direct method for carbon-carbon bond formation: The functional group tolerant cobalt-catalyzed alkylation of aryl halides
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(Figure Presented). A new protocol for the direct cobaltcatalyzed alkylation of aryl halides has been developed that proceeds smoothly in the presence of phosphanes or bipyridines as ligands with a variety of alkyl halides, including challenging alkyl electrophiles bearing β hydrogen atoms (see scheme). Sensitive functional groups are tolerated on both coupling partners, thus, significantly extending the general scope of transition-metal-catalyzed alkylation of aryl halides.
- Amatore, Muriel,Gosmini, Corinne
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supporting information; experimental part
p. 5848 - 5852
(2010/09/03)
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- High catalytic efficiency of nanostructured molybdenum trioxide in the benzylation of arenes and an investigation of the reaction mechanism
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The synthesis and characterization of nanostructured MoO3 with a thickness of about 30 nm and a width of about 450 nm are reported. The composition formula of the MP (precipitation method) precursor was estimated to be [(NH4)2O]0.169·MoO 3· (H2O)0.239. The calcination of the precursor in air afforded nanostructured pellets of the α-MoO3 phase. The nano-structured MoO3 catalyst exhibited high efficiency in catalyzing the benzylation of various arenes with substituted benzyl alcohols, which were strikingly different to common bulk MoO3. Most reactions offered >99% conversion and >99% selectivity to monoalkylated compounds. MoO3 is a typical acid catalyst. However, the benzylation reaction over nanostructured MoO3 does not belong to the acid-catalyzed type or defect site-catalyzed type, since the catalyst has no acidity and defect site on surface. Characterization with thermal, spectroscopic, and electronic techniques reveal that the catalyst contains fully oxygen-coordinated MoO 6 octahedrons on the surface but partially reduced species (Mo 5+) within the bulk phase. The terminal oxygen atoms of Mo=O bonds on the (010) basal plane resemble oxygen anion radicals and act as active sites for the adsorption and activation of benzyl alcohols by electrophilic attack. Such sites are indispensable for catalytic reactions since the blocking of these sites by electron acceptors, such as tetracyanoethylene (TCNE), can greatly decrease catalytic activity. This work represents a successful example of combining a heterogeneous catalysis study with nanomaterial synthesis.
- Wang, Feng,Ueda, Wataru
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experimental part
p. 742 - 753
(2009/10/01)
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- Nanostructured molybdenum oxides and their catalytic performance in the alkylation of arenes
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We report for the first time that nanostructured MoO3 is an excellent catalyst for the alkylation of a wide range of arenes with substituted benzyl alcohols as alkylating agents. The Royal Society of Chemistry.
- Wang, Feng,Ueda, Wataru
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supporting information; scheme or table
p. 3196 - 3198
(2009/02/04)
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- Synthesis of functionalised diarylmethanes via a cobalt-catalysed cross-coupling of arylzinc species with benzyl chlorides
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A new cobalt-catalysed reductive coupling of aryl halides with benzyl chlorides is reported; a variety of diarylmethanes can be prepared in good to excellent yields under mild reaction conditions using CoBr2 as catalyst and Zn dust; this new cobalt-catalysed coupling represents a practical and interesting alternative to previously known methods for the synthesis diarylmethanes. The Royal Society of Chemistry.
- Amatore, Muriel,Gosmini, Corinne
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supporting information; experimental part
p. 5019 - 5021
(2009/06/05)
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- Decatungstate catalyst supported on silica and γ-alumina: Efficient photocatalytic oxidation of benzyl alcohols
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Four supported catalysts with the same tungsten loading were prepared by depositing decatungstate species W10O4-32, through wet impregnation, on the surface of γ-alumina and silica at different pH values. The prepared samples were characterized using BET measurements as well as XRD, UV-vis DR, and XP spectroscopies. Higher dispersion of W(VI) oxo-species was obtained in the silica-supported catalysts compared with the corresponding alumina-supported ones. Within the same support, the dispersion was higher when the impregnation pH is lower than the point of zero charge (pzc) of the support. The decatungstate anions were present mainly on the silica surface without any modification, whereas these underwent a partial depolymerization on their deposition on the γ-alumina surface. The extent of depolymerization was less in the sample prepared at pH above pzc. These findings were explained in terms of the mode of deposition of the W(VI) species from the solution onto the support surface. The photocatalytic activity of the aforementioned catalysts, concerning the photooxidation of 1-phenylethanol, depends on the fraction of the W10O4-32 supported species rather than on the W(VI) dispersion. Thus, extremely high conversions have been obtained over the silica-based catalysts and also over the γ-alumina-based catalyst prepared at relatively high pH. These catalysts also are very effective in the photooxidation of a series of secondary and primary benzyl alcohols, in which benzyl ketones and benzoic acids were formed as the only or major products, respectively. The easy separation of the solid catalyst from the reaction mixture, the high activity, selectivity, and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis. Based on product analysis and kinetic data on the heterogeneous oxidation of benzyl alcohols, we suggest that a hydrogen abstraction transfer (HAT) mechanism predominates with respect to an electron transfer (ET) one in these reactions.
- Tzirakis, Manolis D.,Lykakis, Ioannis N.,Panagiotou, George D.,Bourikas, Kyriakos,Lycourghiotis, Alexis,Kordulis, Christos,Orfanopoulos, Michael
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p. 178 - 189
(2008/09/18)
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- Suzuki-miyaura cross-coupling reactions of benzyl halides with potassium aryltrifluoroborates
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(Chemical Equation Presented) The palladium-catalyzed cross-coupling of potassium aryltrifluoroborates with benzylic halides occurs in good yield with high functional group tolerance. The increased stability of potassium aryltrifluoroborates compared to other boron coupling partners makes this an effective route to functionalized methylene-linked biaryl systems.
- Molander, Gary A.,Elia, Maxwell D.
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p. 9198 - 9202
(2007/10/03)
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- LUMINOUS COMPOUNDS AND LABELING REAGENTS USING THE SAME
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This invention provides: a compound represented by formula (I):R-Y-(-X-Phe-COCH2COCnF2n+1)m wherein R denotes hydrogen, alkyl, phenyl, or a group capable of binding to a protein, peptide, amino acid, nucleic aci
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- A general and straightforward route toward diarylmethanes. Integrated cross-coupling reactions using (2-pyridyl)silylmethylstannane as an air-stable, storable, and versatile coupling platform
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(graph presented) Pharmacologically important diarylmethane structures have been prepared in a straightforward manner through sequentially integrated Pd-catalyzed cross-coupling reactions. (2-Pyridyl)silylmethylstannane was found to be an air-stable, storable, and versatile coupling platform in this synthetic strategy.
- Itami, Kenichiro,Mineno, Masahiro,Kamei, Toshiyuki,Yoshida, Jun-Ichi
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p. 3635 - 3638
(2007/10/03)
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- Cross-coupling reactions of potassium alkyltrifluoroborates with aryl and 1-alkenyl trifluoromethanesulfonates.
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[figure: see text] The palladium-catalyzed coupling reaction of potassium alkyltrifluoroborates with aryl- or alkenyltriflates proceeds to afford the corresponding arenes or alkenes in high yield. The borates are all solids, stable in air, and thus can be stored on the shelf indefinitely. The cross coupling can be effected using PdCl2(dppf).CH2Cl2 as the catalyst in THF-H2O in the presence of Cs2CO3. A variety of functional groups can be tolerated within the borate and/or the triflate coupling partner.
- Molander,Ito
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p. 393 - 396
(2007/10/03)
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- SET and exciplex pathways in the photochemical reactions between aromatic ketones and benzylsilane and stannane derivatives
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The photochemical reaction of α,α,α-trifluoroacetophenone (TFA), benzophenone, and p-cyanoacetophenone with benzyltrimethylsilane in MeCN involves hydrogen transfer from the benzylic position. Desilylation occurs as a minor process only in the case of TFA (but it increases greatly in the presence of MeOH or LiClCO4). The final products result from the statistical recombination of the benzyl and ketyl radicals. Further cases of intramolecular selectivity studied are p-methylbenzyl- and p-methoxybenzyltrimethylsilane (the latter substrate undergoes mainly C-Si bond cleavage in the reaction with TFA) as well as benzyltributylstannane (only destannylation observed with all ketones). Product studies are complemented by the determination of relevant kinetic parameters through steadystate and flash-photolysis experiments. The results are explained in terms of hydrogen transfer proceeding from an exciplex and desilylation from the solvent separated radial ion pair. The latter species predominates when ΔGet -1.
- Cermenati, Laura,Freccero, Mauro,Venturello, Paolo,Albini, Angelo
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p. 7869 - 7876
(2007/10/02)
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- Novel 1,2,3,6-tetrahydropyridine derivatives with potent antihypoxic activity
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A number of 1,2,3,6-tetrahydropyridine derivatives 1a-u were synthesised.They were examined for their antihypoxic actions in mice and rats using various hypoxic tests (eg. hypobaric hypoxia, cytotoxic hypoxia, and asphyxic anoxia).Some of the compounds described displayed significant antihypoxic activity.The antihypoxic activity of the most effective compopund (1q) is probably unrelated to the hypothermising action.The participation of adrenergic and serotoninergic receptors in this effect can also be excluded.However, the activity of this compound may be related to the inhibition of cellular Ca2+ movement. 1,2,3,6-tetrahydropyridine / antihypoxic activity / calcium movement / hypothermia
- Gizur, T.,Kiss, B.,Harsanyi, K.,Karpati, E.,Palosi, E.,et al.
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p. 349 - 356
(2007/10/02)
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- ELECTROPHILIC AROMATIC SUBSTITUTION IN ARENE-TRICARBONYL-CHROMIUM COMPLEXES
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The Friedel-Crafts acetylation and acid-promoted H-D exchange in tricarbonyl-chromium complexes of some diaryls, naphthalene and toluene were studied. For biphenyl and diphenylmethane complexes an assistance in electrophilic substitution by neigdbouring Cr(CO)3 was revealed. A reaction mechanism is proposed, comprising a preliminary formation of a relatively stable intermediate by the attack of electrophilie on the chromium atom, followed by transfer into the key intermediate, in a rate determining step. The key intermediate is formed through an early transition state (resembling a ?-complex) thus differing from free arenes where a late transition state (resembling a ?-complex) is operating. These features explain striking differences observed in orientation effects of complexes compared to "free" arenes.
- Rosca, Sinziana,Chiraleu, Filip,Rosca, Sorin I.
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p. 693 - 705
(2007/10/03)
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- Electrophilic Substitution in (Arene)tricarbonylchromium Complexes. Part 1.
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The Friedel-Crafts acetylation of several (arene)tricarbonylchromium complexes have been investigated.From the results it is concluded that the tricarbonylchromium group deactivates to a small extent towards electrophilic substitution the ring to which it is attached.In the case of tricarbonyl(diphenylmethane)chromium (1; n=1), however, attack occurred on both rings to about an equal extent, possible explanations for this unexpected behaviour are advanced.
- von Rosenberg, Joseph L.,Pinder, A. Reginald
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p. 747 - 752
(2007/10/02)
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- ELECTRON TRANSFER FREE RADICAL MECHANISM IN THE REACTIONS OF ARENEDIAZONIUM CATIONS WITH GRIGNARD REAGENTS
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The major pathway in the reactions of arenediazonium cations with certain Grignard reagents is found to involve an electron transfer from the latter to the ?-system of the former reactant and radicals are the immediate precursors of the final products.
- Singh, P. R.,Khanna, R. K.,Jayaraman, B.
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p. 5475 - 5478
(2007/10/02)
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