- Cp*Rh(iii)/boron hybrid catalysis for directed C-H addition to β-substituted α,β-unsaturated carboxylic acids
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The C-H bond addition reaction of 2-phenylpyridine derivatives with α,β-unsaturated carboxylic acids catalyzed by Cp*Rh(iii)/BH3·SMe2is reported. Activation of C-H bonds with the rhodium catalyst and activation of α,β-unsaturated carboxylic acids with the boron catalyst cooperatively work, and a BINOL-urea hybrid ligand significantly improved the reactivity. With the optimized hybrid catalytic system, various β-disubstituted carboxylic acids were obtained under mild reaction conditions.
- Hirata, Yuki,Kojima, Masahiro,Matsunaga, Shigeki,Tanaka, Ryo,Yoshino, Tatsuhiko
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supporting information
p. 76 - 79
(2021/12/29)
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- Access to Branched Allylarenes via Rhodium(III)-Catalyzed C-H Allylation of (Hetero)arenes with 2-Methylidenetrimethylene Carbonate
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A rhodium(III)-catalyzed C-H allylation of (hetero)arenes by using 2-methylidenetrimethylene carbonate as an efficient allylic source has been developed for the first time. Five different directing groups including oxime, N-nitroso, purine, pyridine, and pyrimidine were compatible, delivering various branched allylarenes bearing an allylic hydroxyl group in moderate to excellent yields.
- Zhang, Shang-Shi,Zheng, Yi-Chuan,Zhang, Zi-Wu,Chen, Shao-Yong,Xie, Hui,Shu, Bing,Song, Jia-Lin,Liu, Yan-Zhi,Zeng, Yao-Fu,Zhang, Luyong
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supporting information
p. 5719 - 5723
(2021/08/16)
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- Three-Component Couplings among Heteroarenes, Difluorocyclopropenes, and Water via C-H Activation
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Three-component couplings have been realized for efficiently constructing various nitrogen-containing skeletons via C-H activation, where difluorocyclopropenes have been first identified as coupling partners. Many substrates including sp2 and sp3 C-H substrates were well tolerated, furnishing the corresponding products in good yields. Furthermore, a catalyst-dependent reaction was also developed, enabling divergent construction of two different frameworks. The application value of these reactions was demonstrated in gram-scale experiments with as little as 1 mol % catalyst.
- Liu, Xuexin,Chen, Jian,Yang, Chunyan,Wu, Zhouping,Li, Zhiyang,Shi, Yuesen,Huang, Tianle,Yang, Zhongzhen,Wu, Yong
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supporting information
p. 6831 - 6835
(2021/09/08)
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- Rhodium-Catalyzed Additive-Free C?H Ethoxycarbonylation of (Hetero)Arenes with Diethyl Dicarbonate as a CO Surrogate
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A rhodium-catalyzed C(sp2)-H ethoxycarbonylation of indoles and arylpyridines using diethyl dicarbonate was developed. The catalytic process features an additive-free ethoxycarbonylation reaction, in which only ethanol and CO2 are produced as byproducts, providing a CO-free and operationally simple protocol. The introduced ethoxycarbonyl group is easily transformed into other ester and amide functionalities in a single step. Moreover, the reaction can be successfully applied on gram scale, and allows for the efficient synthesis of indole-2-carboxylic acid esters and isophthalates.
- Kawai, Yuya,Liao, Yumeng,Matsuda, Takanori,Suzuki, Hirotsugu
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supporting information
p. 4938 - 4942
(2021/09/30)
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- Nickel-Catalyzed Reductive 2-Pyridination of Aryl Iodides with Difluoromethyl 2-Pyridyl Sulfone
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A novel nickel-catalyzed reductive cross-coupling between aryl iodides and difluoromethyl 2-pyridyl sulfone (2-PySO2CF2H) enables C(sp2)-C(sp2) bond formation through selective C(sp2)-S bond cleavage, which demonstrates the new reactivity of 2-PySO2CF2H reagent. This method employs readily available nickel catalyst and sulfones as cross-electrophile coupling partners, providing facile access to biaryls under mild reaction conditions without pregeneration of arylmetal reagents.
- Miao, Wenjun,Ni, Chuanfa,Xiao, Pan,Jia, Rulong,Zhang, Wei,Hu, Jinbo
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supporting information
p. 711 - 715
(2021/01/26)
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- Pd-Catalysed Suzuki-Miyaura cross-coupling of aryl chlorides at low catalyst loadings in water for the synthesis of industrially important fungicides
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The Suzuki-Miyaura coupling reaction of electron-poor aryl chlorides in the synthesis of crop protection-relevant active ingredients in water is disclosed. Optimisation of the reaction conditions allowed running the reaction with 50 ppm of Pd-catalyst loading without an additional organic solvent in the cross-coupling reaction step in short reaction times. The system was optimised for the initial cross-coupling step of the large scale produced fungicides Boscalid, Fluxapyroxad and Bixafen up to 97% yield. It is also shown that the Suzuki-Miyaura reaction can be easily scaled up to 50 g using a simple product separation and purification using environmentally benign solvents in the work-up. To show the usability of this method, it was additionally applied in the three-step synthesis of the desired active ingredients.
- Goetz, Roland,Hashmi, A. Stephen K.,Orecchia, Patrizio,Petkova, Desislava Slavcheva,Rominger, Frank,Schaub, Thomas
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supporting information
p. 8169 - 8180
(2021/11/01)
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- Meta-dehydrogenative alkylation of arenes with ethers, ketones, and esters catalyzed by ruthenium
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A meta-dehydrogenative alkylation of arenes with cyclic ethers, ketones, and esters catalyzed by ruthenium is achieved in the presence of a di-tert-butyl peroxide (DTBP) oxidant. Interestingly, when quinoline and isoquinoline are employed as the directing group, or a chain ether as alkylation reagent, the system produces Minisci reaction products. Mechanistic study indicates that meta-dehydrogenative alkylation is a radical process initiated by DTBP with the assistance of a CAr-Ru bond ortho/para-directing effect.
- Li, Gang,Gao, Yuan,Jia, Chunqi,Wang, Shichong,Yan, Bingxu,Fang, Yu,Yang, Suling
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supporting information
p. 8758 - 8763
(2020/12/02)
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- A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles
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A waste biomass, sodium lignosulfonate, was treated with sodium 2-formylbenzenesulfonate, and the phenylaldehyde condensation product was then used as a robust supporting material to immobilize a copper species. The so-obtained catalyst was characterized by many physicochemical methods including FTIR, EA, FSEM, FTEM, XPS, and TG. This catalyst exhibited excellent catalytic activity in the synthesis of nitrogen-containing heterocycles such as tricyclic indoles bearing 3,4-fused seven-membered rings, 2-arylpyridines, aminonaphthalenes and 3-phenylisoquinolines. In addition, this catalyst showed to be recyclable and could be reused several times without significant loss in activity during the course of the reaction process.
- Bai, Rongxian,Gu, Yanlong,Lai, Bingbing,Li, Minghao,Liu, Ping,Ye, Meng
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supporting information
p. 2888 - 2902
(2020/12/22)
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- Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach
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A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96percent. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.
- Bartolomeu, Aloisio De A.,Brocksom, Timothy J.,De Oliveira, Kleber T.,No?l, Timothy,Silva, Rodrigo C.
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- N-heterocyclic carbene enabled rhodium-catalyzed ortho C(sp2)-H borylation at room temperature
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We report a rhodium-catalyzed ortho C(sp2)-H borylation of 2-phenylpyridines using commercially available N-heterocyclic carbenes (NHCs) as ligand and pinacolatodiboron (B2pin2) as borylating reagent. The reaction could take place at room temperature, tolerating a wide range of functionalities and affording ortho borylated products in moderate to excellent yields. The current method is also applicable to gram-scale reaction with reduced catalyst loading.
- Zhong, Lei,Zong, Zhi-Hong,Wang, Xi-Cun
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supporting information
p. 2547 - 2552
(2019/03/27)
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- A Pyridine–Pyridine Cross-Coupling Reaction via Dearomatized Radical Intermediates
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A pyridine–pyridine coupling reaction has been developed between pyridyl phosphonium salts and cyanopyridines using B2pin2 as an electron-transfer reagent. Complete regio- and cross-selectivity are observed when forming a range of valuable 2,4′-bipyridines. Phosphonium salts were found to be the only viable radical precursors in this process, and mechanistic studies indicate that the process does not proceed through a Minisci-type coupling involving a pyridyl radical. Instead, a radical–radical coupling process between a boryl phosphonium pyridyl radical and a boryl-stabilized cyanopyridine radical explains the C?C bond-forming step.
- Koniarczyk, J. Luke,Greenwood, Jacob W.,Alegre-Requena, Juan V.,Paton, Robert S.,McNally, Andrew
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supporting information
p. 14882 - 14886
(2019/11/05)
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- Enabling Catalytic Arene C-H Amidomethylation via Bis(tosylamido)methane as a Sustainable Formaldimine Releaser
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Addition of catalytic arene C-H to formaldimines has been enabled by Ru(II)-catalyzed amidomethylation with bis(tosylamido)methane as a catalytic formaldimine releaser. The new process provides an atom-efficient and sustainable solution to address the challenges of formaldimines in this type of transformation. Furthermore, new synthetic routes based on this catalytic system have been developed for step-efficient access to N-heterotricyclic core structures that are pharmaceutically relevant.
- Li, Zhong-Yuan,Chaminda Lakmal, Hetti Handi,Cui, Xin
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supporting information
p. 3735 - 3740
(2019/05/24)
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- Ruthenium-Catalyzed ortho- And meta-H/D Exchange of Arenes
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Ruthenium-catalyzed aromatic H/D exchange in [D4]acetic acid has been developed. By using N-heteroarenes as directing groups, both ortho and meta positions are selectively deuterated with high levels of D incorporation. Moreover, this strategy provides an alternative way to achieve meta-C-H activation.
- Zhao, Liang-Liang,Liu, Wei,Zhang, Zengyu,Zhao, Hongyan,Wang, Qi,Yan, Xiaoyu
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supporting information
p. 10023 - 10027
(2019/12/24)
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- Ruthenium-Catalyzed Reductive Cleavage of Unstrained Aryl-Aryl Bonds: Reaction Development and Mechanistic Study
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Cleavage of carbon-carbon bonds has been found in some important industrial processes, for example, petroleum cracking, and has inspired development of numerous synthetic methods. However, nonpolar unstrained C(aryl)-C(aryl) bonds remain one of the toughest bonds to be activated. As a detailed study of a fundamental reaction mode, here a full story is described about our development of a Ru-catalyzed reductive cleavage of unstrained C(aryl)-C(aryl) bonds. A wide range of biaryl compounds that contain directing groups (DGs) at 2,2′ positions can serve as effective substrates. Various heterocycles, such as pyridine, quinoline, pyrimidine, and pyrazole, can be employed as DGs. Besides hydrogen gas, other reagents, such as Hantzsch ester, silanes, and alcohols, can be employed as terminal reductants. The reaction is pH neutral and free of oxidants; thus a number of functional groups are tolerated. Notably, a one-pot C-C activation/C-C coupling has been realized. Computational and experimental mechanistic studies indicate that the reaction involves a ruthenium(II) monohydride-mediated C(aryl)-C(aryl) activation and the resting state of the catalyst is a η4-coordinated ruthenium(II) dichloride complex, which could inspire development of other transformations based on this reaction mode.
- Zhu, Jun,Chen, Peng-hao,Lu, Gang,Liu, Peng,Dong, Guangbin
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supporting information
p. 18630 - 18640
(2019/11/21)
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- Reversible Concerted Metalation-Deprotonation C-H Bond Activation by [Cp*RhCl2]2
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The reversibility of the concerted metalation-deprotonation exchange of eight para-substituted phenylpyridines is examined with the parent Cp*RhCl(κ-C,N-NC5H4-C6H4). Equilibrium constants are determined, and the free energies are used to extract the most important parameters that control the thermodynamics. Keq values are found to correlate best with heterolytic C-H bond strengths but in a way that is not obvious considering the electrophilic nature of these activations.
- Vanderweide, Andrew I.,Brennessel, William W.,Jones, William D.
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supporting information
p. 12960 - 12965
(2019/10/11)
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- Perylenequinonoid-catalyzed photoredox activation for the direct arylation of (het)arenes with sunlight
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Naturally occurring perylenequinonoid pigments (PQPs) have attracted considerable attention owing to their excellent properties of photosensitization. They have been widely investigated as an aspect of photophysics and photobiology. However, their applications in photocatalysis are yet to be explored. We report here that sunlight along with 1 mol% cercosporin, which is one of the perylenequinonoid pigments, catalyzes the direct C-H bond arylation of (het)arenes by a photoredox process with good regioselectivity and broad functional group compatibility. Furthermore, a gram-scale reaction with great conversions of substrates was achieved even by a cercosporin-containing supernatant without organic solvent extraction and purification after liquid fermentation. Thus we set up a bridge between microbial fermentation and organic photocatalysis for chemical reactions in a sustainable, environmentally friendly manner.
- Zhang, Shiwei,Tang, Zhaocheng,Bao, Wenhao,Li, Jia,Guo, Baodang,Huang, Shuping,Zhang, Yan,Rao, Yijian
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supporting information
p. 4364 - 4369
(2019/05/10)
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- Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes
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A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square-planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single-crystal X-ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross-coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.
- Thimma Sambamoorthy, Manikandan,Rengan, Ramesh,Jan Grzegorz, Malecki
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- Transition-Metal-Free Decarboxylative Arylation of 2-Picolinic Acids with Arenes under Air Conditions
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A facile, transition-metal-free, and direct decarboxylative arylation of 2-picolinic acids with simple arenes is described. The oxidative decarboxylative arylation of 2-picolinic acids with arenes proceeds readily via N-chloro carbene intermediates to afford 2-arylpyridines in satisfactory to good yields under transition-metal-free conditions. This new type of decarboxylative arylation is operationally simple and scalable and exhibits high functional-group tolerance. Various synthetically useful functional groups, such as halogen atoms, methoxycarbonyl, and nitro, remain intact during the decarboxylative arylation of 2-picolinic acids.
- Zhang, Xitao,Feng, Xiujuan,Zhou, Chuancheng,Yu, Xiaoqiang,Yamamoto, Yoshinori,Bao, Ming
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supporting information
p. 7095 - 7099
(2018/11/23)
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- Facile C–H arylation using catalytically active terminal sulfurs of 2 dimensional molybdenum disulfide
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The first methodology of C–H arylation of heteroarene via 2D transition metal dichalcogenides that have catalytically active edge functional groups was described. The terminal sulfur groups could effectively catalyze a formation of an azo-linked intermediate with aryl diazonium salts, leading to produce heteroarenes with good yields. This novel methodology using bulk 2D transition metal dichalcogenides that have catalytically active edge functional groups can apply for various reactions to achieve C–C bond formation in the fields of heterogeneous catalysis that is easily separable, highly reusable, and inexpensive method.
- Hwang, Eunhee,Mi Lee, Sae,Bak, Sora,Min Hwang, Hee,Kim, Hyunjung,Lee, Hyoyoung
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supporting information
p. 3969 - 3973
(2018/10/02)
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- C6-Selective Direct Arylation of 2-Phenylpyridine via an Activated N-methylpyridinium Salt: A Combined Experimental and Theoretical Study
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An elegant pre-activation strategy, based on the formation of N-methylpyridinium iodide salts for C6-selective direct arylation of 2-phenylpyridines using Pd/Cu cooperative catalysis, has been developed. By this methodology, a wide range of unsymmetrical 2, 6-diarylpyridines were synthesized with high reactivity and regioselectivity as well as good functional group tolerance. In particular, challenging substrates bearing electron donating groups (EDGs), such as OMe, NMe2, were also successfully employed in this reaction. Deuterium incorporation studies revealed that the C?H bond acidity is improved significantly in N-methylpyridinium salts compared with their N-Oxide and N-iminopyridinium ylide counterparts, thus solving the long-standing problem associated with previous strategies for the synthesis of diaryl pyridines. Finally, the control experiments and DFT calculations supported a Pd-catalyzed and Cu-mediated mechanism in which a carbenoid copper species that is formed in-situ from N-methylpyridinium salts, participates in a Pd-catalyzed arylation followed by an iodide-promoted N-demethylation process. (Figure presented.).
- Yin, Changzhen,Zhong, Kangbao,Li, Wenjing,Yang, Xiao,Sun, Rui,Zhang, Chunchun,Zheng, Xueli,Yuan, Maolin,Li, Ruixiang,Lan, Yu,Fu, Haiyan,Chen, Hua
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supporting information
p. 3990 - 3998
(2018/09/12)
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- Dibenzofuran and dibenzothiophene based palladium(ii)/NHC catalysts-synthesis and applications in C-C bond formation
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In the quest for a new ligand system for Pd(ii)/NHCs, we developed new dibenzofuran and dibenzothiophene based palladium N-heterocyclic carbene catalysts D1-D6 in good yields. All the catalysts were characterized by multinuclear NMR spectroscopy and HRMS. The X-ray crystal structure of the representative dibenzothiophene based Pd(ii)/NHC D4 was determined. Among the precatalysts, D1 was shown to be highly effective in the Suzuki-Miyaura cross-coupling reaction of heterocyclic bromides with boronic acids. Besides, D1 affords diverse arylated benzoxazoles via direct C-H bond functionalization with substituted bromo derivatives.
- Karthik, Shanmugam,Gandhi, Thirumanavelan
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supporting information
p. 15811 - 15819
(2018/10/04)
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- Metallaphotoredox-Mediated Csp2-H Hydroxylation of Arenes under Aerobic Conditions
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The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc)2 as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-state intramolecular proton transfer properties for generating tunable luminescence responses.
- Shah, Sk. Sheriff,Paul, Amrita,Bera, Manoranjan,Venkatesh, Yarra,Singh, N. D. Pradeep
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supporting information
p. 5533 - 5536
(2018/09/21)
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- An Iron-Based Long-Lived Catalyst for Direct C?H Arylation of Arenes and Heteroarenes
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Direct C?H arylation of arenes and heteroarenes to biaryls at ambient temperature has been accomplished using a phenalenyl-supported iron(III) catalyst. The present catalyst requires a chemical reductant such as potassium and functions without any light stimulation. C?H arylation of various heteroarenes including pyridine as well as unactivated arene such as benzene delivered good to excellent yield (28 examples, up to 92 %) at room temperature. A combined effort based on experiments and theoretical calculations established that a phenalenyl-based radical species (generated by chemical reduction of the iron(III) coordinated phenalenyl complex) plays key role during the catalysis. Furthermore, this catalyst displayed remarkable stability during the catalysis, as evident from the fact that it was still usable over ten consecutive catalytic runs without losing its catalytic efficiency.
- Chakraborty, Soumi,Ahmed, Jasimuddin,Shaw, Bikash Kumar,Jose, Anex,Mandal, Swadhin K.
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p. 17651 - 17655
(2018/11/10)
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- A phosphine-free, atom-efficient cross-coupling of aryl iodides with triarylindiums or trialkynylindiums catalyzed by immobilization of palladium(0) in MCM-41
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The first phosphine-free heterogeneous atom-efficient cross-coupling reaction of aryl iodides with triarylindiums or trialkynylindiums was achieved in THF at 68 °C by using 1 mol% of MCM-41-immobilized palladium(0)-Schiff base complex [MCM-41-N,N-Pd(0)] as catalyst, yielding a variety of unsymmetrical biaryls and arylalkynes in good to excellent yields. The heterogeneous palladium(0) catalyst could easily be prepared via a simple procedure from commercially readily available reagents, and recovered by filtration of the reaction solution and recycled at least 10 times without significant loss of activity.
- Lei, Zhiwei,Liu, Haiyi,Cai, Mingzhong
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- Blue light mediated C-H arylation of heteroarenes using TiO2 as an immobilized photocatalyst in a continuous-flow microreactor
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Titanium dioxide was applied as an immobilized photocatalyst in a microstructured falling film reactor for the continuous-flow C-H arylation of heteroarenes with aryldiazonium salts as the starting material. Detailed investigations of the catalyst and a successful long-term run proved its excellent usability for this process. Very good yields up to 99% were achieved with broad substrate scope and were compared with batch synthesis. The transfer to the continuous-flow mode revealed an impressive boost in reactor performance solely resulting from the improved irradiation and contact of the catalyst, substrate and light.
- Fabry, David C.,Ho, Yee Ann,Zapf, Ralf,Tremel, Wolfgang,Panth?fer, Martin,Rueping, Magnus,Rehm, Thomas H.
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supporting information
p. 1911 - 1918
(2017/06/09)
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- α-Halo carbonyls enable: Meta selective primary, secondary and tertiary C-H alkylations by ruthenium catalysis
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A catalytic meta selective C-H alkylation of arenes is described using a wide range of α-halo carbonyls as coupling partners. Previously unreported primary alkylations with high meta selectivity have been enabled by this methodology whereas using straight chain alkyl halides affords ortho substituted products. Mechanistic analysis reveals an activation pathway whereby cyclometalation with a ruthenium(ii) complex activates the substrate molecule and is responsible for the meta selectivity observed. A distinct second activation of the coupling partner allows site selective reaction between both components.
- Paterson, Andrew J.,Heron, Callum J.,McMullin, Claire L.,Mahon, Mary F.,Press, Neil J.,Frost, Christopher G.
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supporting information
p. 5993 - 6000
(2017/07/25)
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- Palladium-catalyzed C-H alkylation of 2-phenylpyridines with alkyl iodides
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Palladium-catalyzed C-H alkylation reaction of 2-phenylpyridines with alkyl iodides has been successfully developed. The palladacycles obtained from 2-phenylpyridines should act as the key intermediates in the alkylation reaction.
- Wang, Xiaoling,Ji, Xiaoming,Shao, Changdong,Zhang, Yu,Zhang, Yanghui
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supporting information
p. 5616 - 5624
(2017/07/12)
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- Ruthenium-Catalyzed meta-Selective C?H Mono- and Difluoromethylation of Arenes through ortho-Metalation Strategy
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The first example for the ruthenium-catalyzed ligand-directed meta-selective C?H mono- and difluoromethylation is developed, affording a variety of new meta-mono- and difluoromethylated 2-phenylpyridines, 2-phenylpyrimidines, and 1-phenylpyrazoles in moderate-to-good yields. This new transformation exhibits broad substrate scope, good functional group tolerance, and high efficiency, and offers a practical approach to synthesize mono- and difluoromethylated arenes. Mechanistic studies indicate that a reaction pathway involving palladium-initiated radical species is involved in the catalytic cycle. The new dual catalytic system consisting of compatible ruthenium(II) and palladium(0) complexes enables the key processes of C?H activation and mono-/difluoromethyl-radical formation to occur and achieves the meta-selective functionalization efficiently. In addition, the present protocol can also be extended to non-fluoromethylation.
- Li, Zhong-Yuan,Li, Liang,Li, Qi-Li,Jing, Kun,Xu, Hui,Wang, Guan-Wu
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supporting information
p. 3285 - 3290
(2017/03/16)
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- Palladium-catalyzed decarboxylative, decarbonylative and dehydrogenative C(sp2)-H acylation at room temperature
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Over the past few decades, an impressive array of C-H activation methodology has been developed for organic synthesis. However, due to the inherent inertness of the C-H bonds (e.g. ～110 kcal mol-1 for the cleavage of C(aryl)-H bonds) harsh reaction conditions have been realized to overcome high energetic transition states resulting in a limited substrate scope and functional group tolerance. Therefore, the development of mild C-H functionalization protocols is in high demand to exploit the full potential of the C-H activation strategy in the synthesis of a complex molecular framework. Although, electron-rich substrates undergo electrophilic metalation under relatively mild conditions, electron-deficient substrates proceed through a rate-limiting C-H insertion under forcing conditions at high temperature. In addition, a stoichiometric amount of toxic silver salt is frequently used in palladium catalysis to facilitate the C-H activation process which is not acceptable from the environmental and industrial standpoint. We report herein, a Pd(ii)-catalyzed decarboxylative C-H acylation of 2-arylpyridines with α-ketocarboxylic acids under mild conditions. The present protocol does not require stoichiometric silver(i) salts as additives and proceeds smoothly at ambient temperature. A novel decarbonylative C-H acylation reaction has also been accomplished using aryl glyoxals as acyl surrogates. Finally, a practical C-H acylation via a dehydrogenative pathway has been demonstrated using commercially available benzaldehydes and aqueous hydroperoxides. We also disclose that acetonitrile solvent is optimal for the acylation reaction at room temperature and has a prominent role in the reaction outcome. Control experiments suggest that the acylation reaction via decarboxylative, decarbonylative and dehydrogenative proceeds through a radical pathway. Thus we disclose a practical protocol for the sp2 C-H acylation reaction.
- Hossian, Asik,Manna, Manash Kumar,Manna, Kartic,Jana, Ranjan
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supporting information
p. 6592 - 6603
(2017/08/16)
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- Radical Arylation of Anilines and Pyrroles via Aryldiazotates
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The radical arylation of anilines and pyrroles can be achieved under transition-metal- and catalyst-free conditions by using aryldiazotates in strongly alkaline aqueous solutions. The aryldiazotates act as protected diazonium ions, which do not undergo azo coupling with electron-rich aromatic substrates, but can still serve as an aryl radical source at slightly elevated temperatures. Based on an improved preparation of aryldiazotates in aqueous solution, homolytic aromatic substitutions of anilines and pyrroles were conducted with good overall yields and high regioselectivity. Moreover, DFT calculations provided further mechanistic insights.
- Hofmann, Josefa,Gans, Eva,Clark, Timothy,Heinrich, Markus R.
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p. 9647 - 9656
(2017/07/22)
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- A new face of phenalenyl-based radicals in the transition metal-free C-H arylation of heteroarenes at room temperature: Trapping the radical initiator: Via C-C σ-bond formation
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The radical-mediated transition metal-free approach for the direct C-H bond functionalization of arenes is considered as a cost effective alternative to transition metal-based catalysis. An organic ligand-based radical plays a key role by generating an aryl radical which undergoes a subsequent functionalization process. The design principle of the present study takes advantage of a relatively stable odd alternant hydrocarbon-based phenalenyl (PLY) radical. In this study, the first transition metal-free catalyzed direct C-H arylation of a variety of heteroarenes such as azoles, furan, thiophene and pyridine at room temperature has been reported using a phenalenyl-based radical without employing any photoactivation step. This protocol has been successfully applied to the gram scale synthesis of core moieties of bioactive molecules. The phenalenyl-based radical initiator has been characterized crystallographically by trapping it via the formation of a C-C σ-bond between the phenalenyl radical and solvent-based radical species.
- Ahmed, Jasimuddin,Sreejyothi,Vijaykumar, Gonela,Jose, Anex,Raj, Manthan,Mandal, Swadhin K.
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p. 7798 - 7806
(2017/10/30)
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- Synthesis of 2-phenyl pyridine derivatives from aryl ketones and 1,3-diaminopropane using palladium acetate as a catalyst
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A simple and efficient method for the synthesis of 2-phenyl pyridine via cyclization of aryl ketone with 1,3-diaminopropane using palladium acetate is established. This method is mild, operationally simple, involves short reaction time and involves easy workup procedure to afford the corresponding 2-phenyl pyridines in moderate to good yield.
- Ghodse, Shrikant M.,Telvekar, Vikas N.
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supporting information
p. 524 - 526
(2017/01/17)
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- Interface coassembly of mesoporous MoS2 based-frameworks for enhanced near-infrared light driven photocatalysis
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The three-dimensional porous Fe3O4@Cu2-xS-MoS2 framework is reported for the first time. The as-prepared 3D framework exhibits good structural stability, high surface area, enhanced adsorption capacity to substrates, and strong absorption in the NIR range. As a result, such hybrid frameworks exhibit excellent NIR-light photocatalytic activity and stable cycling for the direct arylation of heteroaromatics at room temperature.
- Zhi, Lihua,Zhang, Haoli,Yang, Zhengyin,Liu, Weisheng,Wang, Baodui
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supporting information
p. 6431 - 6434
(2016/05/24)
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- A atom-efficient cross-coupling reaction of aryl iodides with triarylbismuths catalyzed by immobilization of palladium(II)-Schiff base complex in MCM-41
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The first phosphine-free heterogeneous atom-efficient cross-coupling of aryl iodides with triarylbismuths was achieved in NMP using K2CO3 as base at 110 °C in the presence of 2 mol % of an MCM-41-immobilized palladium(II)-Schiff base complex [MCM-41-N,N-Pd(OAc)2], yielding a variety of unsymmetrical biaryls in good to excellent yields. This new heterogeneous palladium catalyst exhibits high catalytic activity and can be recovered by a simple filtration of the reaction solution and recycled for at least 10 consecutive trials without any decreases in activity. Our system not only avoids the use of phosphine ligands, but also solves the basic problem of palladium catalyst recovery and reuse.
- Xu, Caifeng,Yin, Lin,Huang, Bin,Liu, Haiyi,Cai, Mingzhong
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p. 2065 - 2071
(2016/04/09)
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- Photoactivated Functionizable Tetracarbonyl(phenylpyridine)manganese(I) Complexes as CO-Releasing Molecules: A Direct Suzuki–Miyaura Cross-Coupling on a Thermally Stable CO-RM
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A new class of carbon monoxide-releasing molecules (CO-RMs) are reported based on a previously known tetracarbonyl phenylpyridine manganese(I) motif. A pre-functionalized CO-RM undergoes a direct Pd-catalysed Suzuki–Miyaura cross-coupling with phenylboronic acid to give a π-extended three-ring CO-RM. Cross-coupling conditions were modified to allow coupling of a morpholine-containing boronic acid on to a CO-RM, introducing drug-like functionality. An LED system was used to facilitate controlled CO-release. Irradiation using an LED (400 nm or 365 nm) gives rise to faster CO-release, with lower overall input power than traditional use of a TLC lamp (365 nm), as measured by an assay based on the conversion of deoxymyoglobin to carbonmonoxymyoglobin.
- Ward, Jonathan S.,Bray, Joshua T. W.,Aucott, Benjamin J.,Wagner, Conrad,Pridmore, Natalie E.,Whitwood, Adrian C.,Moir, James W. B.,Lynam, Jason M.,Fairlamb, Ian J. S.
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p. 5044 - 5051
(2016/11/09)
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- Highly efficient palladium(II) hydrazone based catalysts for the Suzuki coupling reaction in aqueous medium
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Synthesis of a new family of air stable palladium(ii)benzhydrazone complexes of the general formula [PdCl(PPh3)(L)] (where HL = thiophene aldehyde benzhydrazones) incorporating PPh3 and chloride as co-ligands has been described through a single and convenient step with good yields. All the new complexes have been fully characterized by means of elemental analysis, IR, UV-vis, and NMR spectral methods. The molecular structures of three of the complexes were determined by single crystal X-ray crystallography, which confirm the coordination mode of benzhydrazone and reveal the presence of a distorted square planar geometry around the Pd ion. The complexes 1-5 (0.05 mol%) have been found to be a highly active catalytic system in the mono and double Suzuki-Miyaura cross coupling reaction of deactivated aryl and heteroaryl bromides with different types of aryl boronic acids in neat water and the maximum yield was up to >99%. Notably, these catalysts work well with ultra-low loading of the catalysts and show high turnover numbers in a short time towards different substrates. Moreover, the catalysts could be simply recovered and reused five times without significant loss of efficiency.
- Muthumari, Subramanian,Ramesh, Rengan
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p. 52101 - 52112
(2016/06/13)
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- Palladium catalyzed ortho-C-H-acylation of 2-arylpyridines using phenylacetylenes and styrene epoxide
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A palladium-catalyzed ortho-C-H-acylation of 2-arylpyridine using phenylacetylenes and styrene epoxide as the acylated reagents was developed. With the employment of tert-butyl hydroperoxide (TBHP) as the oxidant and a phosphorous ligand, the protocol generates corresponding aryl ketones in moderated to good yields with high regioselectivity and good functional group compatibility.
- Zhang, Qian,Wang, Yang,Yang, Tingting,Li, Li,Li, Dong
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supporting information
p. 90 - 94
(2015/12/23)
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- Pd-Catalyzed Homo Cross-Dehydrogenative Coupling of 2-Arylpyridines by Using I2 as the Sole Oxidant
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A palladium-catalyzed homo cross-dehydrogenative coupling (CDC) of 2-arylpyridines via C-H activation is described. This reaction employs I2 as the sole oxidant without any other additives, which complements the hypervalent iodine chemistry, such as of phenyliodonium diacetate (PIDA) or IOAc, in C-H activation research field. A tentative mechanism involving a Pd(II)-Pd(IV) catalytic cycle is proposed to rationalize this homo CDC reaction.
- Liu, Wenbo,Zhu, Youquan,Li, Chao-Jun
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supporting information
p. 1616 - 1621
(2016/05/24)
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- Chelation-Assisted Copper-Mediated Direct Acetylamination of 2-Arylpyridine C-H Bonds with Cyanate Salts
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In this study, the coupling of 2-phenylpyridine derivatives and potassium cyanate through C-H bond functionalization in the presence of a copper salt is developed for the first time. By this protocol, various heteroarylated acetanilide derivatives are synthesized in good yields. 2-Phenylpyridines containing electron-donating and -withdrawing groups appear to be well-tolerated by this transformation.
- Kianmehr, Ebrahim,Amiri Lomedasht, Yousef,Faghih, Nasser,Khan, Khalid Mohammed
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p. 6087 - 6092
(2016/07/23)
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- Palladium-Catalyzed Decarbonylative Cross-Coupling of Azinecarboxylates with Arylboronic Acids
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The first palladium-catalyzed decarbonylative coupling of phenyl 2-azinecarboxylates and arylboronic acids is presented. The key for the development of this decarbonylative coupling is the use of Pd/dcype as a catalyst. A wide range of 2-azinecarboxylates can undergo the present coupling reaction to afford 2-arylazines. By combination with previously reported nickel-catalyzed decarbonylative coupling, we achieved a chemoselective sequential decarbonylative coupling of pyridine dicarboxylate to synthesize 2,4-diarylpyridine.
- Muto, Kei,Hatakeyama, Taito,Itami, Kenichiro,Yamaguchi, Junichiro
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supporting information
p. 5106 - 5109
(2016/10/14)
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- Metal-free oxidative cyclization of acetophenones with diamines: A facile access to phenylpyridines
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An efficient metal-free access to 2- and 3-phenylpyridines via oxidative coupling of acetophenones or phenylacetones with 1,3-diaminopropane has been described. The reaction involves shorter reaction time, excellent yields and a broad substrate scope. The reaction proceeds via the formation of imine, which further undergoes oxidative C-N bond cleavage, C-C bond formation and oxidation to give a pyridine skeleton. The quantum chemical calculations identified the transition state for the reaction and helped in tracing the reaction mechanism.
- Sharma, Rohit,Patel, Neha,Vishwakarma, Ram A.,Bharatam, Prasad V.,Bharate, Sandip B.
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supporting information
p. 1009 - 1012
(2016/01/16)
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- Visible light-induced aerobic C-N bond activation: A photocatalytic strategy for the preparation of 2-arylpyridines and 2-arylquinolines
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An efficient method for accessing arylpyridines and arylquinolines via visible light-induced aerobic C-N bond activation is described. The applicability of different kinds of simple ketones, easily available amines, and the use of air as the sole oxidant make this transformation very attractive.
- Hu, Bei,Li, Yuyuan,Dong, Wuheng,Xie, Xiaomin,Wan, Jun,Zhang, Zhaoguo
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p. 48315 - 48318
(2016/06/09)
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- Cross-coupling study of iodo/chloropyridines and 2-chloroquinoline with atom-economic triarylbismuth reagents under Pd-catalysis
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This study describes the palladium-catalyzed couplings of iodopyridines, chloropyridines, and chloroquinoline with atom-economic BiAr3 reagents in sub-stoichiometric loadings. Mono-arylations of iodo and chloropyridines produced arylpyridines i
- Rao, Maddali L.N.,Dhanorkar, Ritesh J.
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p. 338 - 349
(2015/03/04)
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- Comparative Catalytic Activity of Group 9 [CpMIII] Complexes: Cobalt-Catalyzed C-H Amidation of Arenes with Dioxazolones as Amidating Reagents
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A procedure for the [CpCoIII]-catalyzed direct C-H amidation of arenes with dioxazolone has been developed. This reaction proceeds under straightforward and mild conditions with a broad range of substrates, including anilides. A comparative study on the catalytic activity of Group 9 [{CpMCl2}2] complexes revealed the unique efficiency of the cobalt catalyst. Pick of the bunch: A variety of arenes, including anilides, underwent direct C-H amidation with dioxazolones in the presence of a cobalt catalyst with a Cp? ligand under mild and straightforward reaction conditions (see scheme; Piv=pivaloyl). A comparative study of Group 9 [CpMIII] complexes revealed the unique ability of the cobalt catalyst to promote this transformation efficiently.
- Park, Juhyeon,Chang, Sukbok
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supporting information
p. 14103 - 14107
(2016/01/25)
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- Catalytic Electrophilic C-H Silylation of Pyridines Enabled by Temporary Dearomatization
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A C-H silylation of pyridines that seemingly proceeds through electrophilic aromatic substitution (SEAr) is reported. Reactions of 2- and 3-substituted pyridines with hydrosilanes in the presence of a catalyst that splits the Si-H bond into a hydride and a silicon electrophile yield the corresponding 5-silylated pyridines. This formal silylation of an aromatic C-H bond is the result of a three-step sequence, consisting of a pyridine hydrosilylation, a dehydrogenative C-H silylation of the intermediate enamine, and a 1,4-dihydropyridine retro-hydrosilylation. The key intermediates were detected by 1H NMR spectroscopy and prepared through the individual steps. This complex interplay of electrophilic silylation, hydride transfer, and proton abstraction is promoted by a single catalyst.
- Wübbolt, Simon,Oestreich, Martin
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supporting information
p. 15876 - 15879
(2016/01/28)
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- Catalytic meta-selective C-H functionalization to construct quaternary carbon centres
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A catalytic meta-selective C-H functionalization of 2-phenylpyridines using a range of tertiary halides is described. The protocol is simple to perform and uses commercially available reagents to construct challenging quaternary carbon centres in a regioselective manner. Preliminary studies suggest the C-H functionalization proceeds through a radical process directed via a remote σ-activation.
- Paterson, Andrew J.,St John-Campbell, Sahra,Mahon, Mary F.,Press, Neil J.,Frost, Christopher G.
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supporting information
p. 12807 - 12810
(2015/08/06)
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- Cobalt-catalyzed C-H cyanation of (Hetero)arenes and 6-Arylpurines with N -cyanosuccinimide as a new cyanating agent
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A cobalt-catalyzed C-H cyanation reaction of arenes has been developed using N-cyanosuccinimide as a new electrophilic cyanating agent. The reaction proceeds with high selectivity to afford monocyanated products with excellent functional group tolerance. Substrate scope was found to be broad enough to include a wide range of heterocycles including 6-arylpurines.
- Pawar, Amit B.,Chang, Sukbok
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supporting information
p. 660 - 663
(2015/03/04)
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- Cobalt(III)-Catalyzed Directed C-H Coupling with Diazo Compounds: Straightforward Access towards Extended π-Systems
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The first highly efficient and scalable cobalt-catalyzed directed C-H functionalization with carbene precursors is presented. This methodology provides a modular route towards a new class of conjugated polycyclic hydrocarbons with tunable emission wavelengths both in solution and in the solid state.
- Zhao, Dongbing,Kim, Ju Hyun,Stegemann, Linda,Strassert, Cristian A.,Glorius, Frank
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supporting information
p. 4508 - 4511
(2015/04/14)
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- RhIII-Catalyzed C-H Activation with Pyridotriazoles: Direct Access to Fluorophores for Metal-Ion Detection
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The first C-H bond activation with pyridotriazoles as coupling partners is presented using a RhIII catalyst. The pyridotriazoles can be used as new carbene precursors in C-H activation for direct access to novel fluorescent scaffolds. These tunable fluorophores can be applied for the detection of metal ions.
- Kim, Ju Hyun,Gensch, Tobias,Zhao, Dongbing,Stegemann, Linda,Strassert, Cristian A.,Glorius, Frank
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supporting information
p. 10975 - 10979
(2015/09/15)
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- A Pd(ii)/Mg-La mixed oxide catalyst for cyanation of aryl C-H bonds and tandem Suzuki-cyanation reactions
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A palladium(ii)/magnesium-lanthanum mixed oxide (Pd(ii)/Mg-La) catalyst is a reusable catalyst for cyanation of aromatic C-H bonds by using the combination of NH4HCO3 and DMSO as the ''CN'' source. Moderate to good yields of aromatic nitriles were obtained. An excellent regioselectivity was achieved using the present protocol. A tandem process involving Suzuki coupling followed by a cyanation reaction was also developed using the heterogeneous (Pd(ii)/Mg-La) catalyst. This cascade process resulted in the formation of aromatic nitrile from simple 2-halopyridine. The catalyst was recovered by centrifugation and reused for three consecutive cycles with nearly consistent activity and selectivity. This journal is
- Kishore, Ramineni,Yadav, Jagjit,Venu, Boosa,Venugopal, Akula,Lakshmi Kantam
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supporting information
p. 5259 - 5264
(2015/07/07)
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