- Formate-Mediated Cross-Electrophile Reductive Coupling of Aryl Iodides and Bromopyridines
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Two catalytic systems for the formate-mediated cross-electrophile reductive coupling of aryl iodides with 6-bromopyridines are described. Using homogenous rhodium or heterogeneous palladium catalysts, the products of reductive biaryl cross-coupling could
- Schwartz, Leyah A.,Spielmann, Kim,Swyka, Robert A.,Xiang, Ming,Krische, Michael J.
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- Catalyst Selection Facilitates the Use of Heterocyclic Sulfinates as General Nucleophilic Coupling Partners in Palladium-Catalyzed Coupling Reactions
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A range of 5- and 6-membered heterocycle-derived sulfinates are shown to be effective nucleophilic coupling partners with aryl chlorides and bromides using Pd(0) catalysis. The use of optimal reaction conditions, specifically incorporating a P(t-Bu)2Me-derived Pd catalyst, allowed reactions to be performed at moderate temperatures and enabled the inclusion of a variety of sensitive functional groups. Challenging heterocyclic sulfinates, including pyrazine, pyridazine, pyrimidine, pyrazole, and imidazole, were all shown to perform well.
- Markovic, Tim,Rocke, Benjamin N.,Blakemore, David C.,Mascitti, Vincent,Willis, Michael C.
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- Nickel/Photoredox-Catalyzed Methylation of (Hetero)aryl Chlorides Using Trimethyl Orthoformate as a Methyl Radical Source
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Methylation of organohalides represents a valuable transformation, but typically requires harsh reaction conditions or reagents. We report a radical approach for the methylation of (hetero)aryl chlorides using nickel/photoredox catalysis wherein trimethyl orthoformate, a common laboratory solvent, serves as a methyl source. This method permits methylation of (hetero)aryl chlorides and acyl chlorides at an early and late stage with broad functional group compatibility. Mechanistic investigations indicate that trimethyl orthoformate serves as a source of methyl radical via β-scission from a tertiary radical generated upon chlorine-mediated hydrogen atom transfer.
- Kariofillis, Stavros K.,Shields, Benjamin J.,Tekle-Smith, Makeda A.,Zacuto, Michael J.,Doyle, Abigail G.
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- Transition-Metal-Free Regioselective Alkylation of Pyridine N-Oxides Using 1,1-Diborylalkanes as Alkylating Reagents
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Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C?H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thus it can serve as a powerful method for late-stage functionalization.
- Jo, Woohyun,Kim, Junghoon,Choi, Seoyoung,Cho, Seung Hwan
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- Novel synthesis of 6-substituted 2-picolines from aryl/heteroaryl β-enaminones and meldrum's acid using cecl3.7H2o/nai
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One-pot condensation of aryl/heteroaryl β-enaminones, Meldrum's acid, and ammonium acetate in the presence of CeCl3.7H2O/NaI via tandem Michael addition-cyclodehydration-elimination sequence led to the formation of novel regioselecti
- Addla, Dinesh,Kantevari, Srinivas
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- Palladium-Catalyzed Cascade Reactions of I-Ketonitriles with Arylboronic Acids: Synthesis of Pyridines
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This study presents the first example of the Pd-catalyzed cascade reactions of 5-oxohexanenitrile with arylboronic acids, affording important synthon 2-methylpyridines that can be further translated through C(sp3)-H functionalization to construct pyridine derivatives. Furthermore, this chemistry allows 5-oxo-5-Arylpentanenitrile to react with arylboronic acids to provide unsymmetrical 2,6-diarylpyridines. This protocol paves the way for the practical and atom economical syntheses of valuable pyridines with broad functional groups in moderate to excellent yields under mild conditions.
- Chen, Jiuxi,Hu, Maolin,Li, Renhao,Liu, Jichao,Qi, Linjun,Shao, Yinlin,Yao, Xinrong,Zhao, Zhiwei,Zhen, Qianqian
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supporting information
p. 114 - 119
(2020/03/25)
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- Palladium-Catalyzed Direct Arylation of Alkylpyridine via Activated N-Methylpyridinium Salts
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An efficient Pd-catalyzed arylation of alkylpyridine based on the pyridinium activation strategy has been developed for synthesis of mixed aryl alkylpyridines. It was found that (1) the N-methyl group in the pyridinium salts acted as a transient activator and could be automatically departed after the reaction, (2) CuBr was an indispensable additive for achieving the C6-selective arylation, (3) the α-branched alkyl chain on the alkylpyridine greatly increased the yield of the product. Deuterium labelling experiment revealed that in the case of the α-branched alkylpyridine, the presence of CuBr completely inhibited the H/D exchange at the benzylic position and thus enabled the selective arylation at the C6 position. This protocol demonstrates a broad substrate scope, and with respect to both the aryl iodides and the α-branched alkylpyridine, the desired mixed aryl alkylpyridines were obtained in generally good to excellent yields.
- Chen, Xue,Li, Wen-Jing,Li, Shun,Tang, Juan,Du, Xi,Zheng, Xue-Li,Yuan, Mao-Lin,Fu, Hai-Yan,Li, Rui-Xiang,Chen, Hua
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p. 622 - 632
(2019/12/30)
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- Heterocyclic Allylsulfones as Latent Heteroaryl Nucleophiles in Palladium-Catalyzed Cross-Coupling Reactions
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Heterocyclic sulfinates are effective reagents in palladium-catalyzed coupling reactions with aryl and heteroaryl halides, often providing high yields of the targeted biaryl. However, the preparation and purification of complex heterocylic sulfinates can be problematic. In addition, sulfinate functionality is not tolerant of the majority of synthetic transformations, making these reagents unsuitable for multistep elaboration. Herein, we show that heterocyclic allylsulfones can function as latent sulfinate reagents and, when treated with a Pd(0) catalyst and an aryl halide, undergo deallylation, followed by efficient desulfinylative cross-coupling. A broad range of allyl heteroarylsulfones are conveniently prepared, using several complementary routes, and are shown to be effective coupling partners with a variety of aryl and heteroaryl halides. We demonstrate that the allylsulfone functional group can tolerate a range of standard synthetic transformations, including orthogonal C- and N-coupling reactions, allowing multistep elaboration. The allylsulfones are successfully coupled with a variety of medicinally relevant substrates, demonstrating their applicability in demanding cross-coupling transformations. In addition, pharmaceutical agents crizotinib and etoricoxib were prepared using allyl heteroaryl sulfone coupling partners, further demonstrating the utility of these new reagents.
- Markovic, Tim,Murray, Philip R.D.,Rocke, Benjamin N.,Shavnya, Andre,Blakemore, David C.,Willis, Michael C.
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p. 15916 - 15923
(2018/11/23)
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- Pyridine sulfinates as general nucleophilic coupling partners in palladium-catalyzed cross-coupling reactions with aryl halides
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Pyridine rings are ubiquitous in drug molecules; however, the pre-eminent reaction used to form carbon-carbon bonds in the pharmaceutical industry, the Suzuki-Miyaura cross-coupling reaction, often fails when applied to these structures. This phenomenon is most pronounced in 2-substituted pyridines, and results from the difficulty in preparing, the poor stability of, and low efficiency in reactions of pyridine-2-boronates. We demonstrate that by replacing these boronates with pyridine-2-sulfinates, a cross-coupling process of unrivalled scope and utility is realized. The corresponding 3-And 4-substituted pyridine variants are also efficient coupling partners. In addition, we apply these sulfinates in a library format to the preparation of medicinally relevant derivatives of the drugs varenicline (Chantix) and mepyramine (Anthisan).
- Markovic, Tim,Rocke, Benjamin N.,Blakemore, David C.,Mascitti, Vincent,Willis, Michael C.
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p. 4437 - 4442
(2017/07/11)
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- A General Suzuki-Miyaura Coupling of Aryl Chlorides with Potassium Aryltrifluoroborates in Water Catalyzed by an Efficient CPCy Phendole-phos-Palladium Complex
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General examples of the palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl or heteroaryl chlorides with potassium aryl- or heteroaryltrifluoroborates in water are presented. The palladium complex comprising of palladium(II) acetate and 'CPCy Phendole-phos' is found to be a highly effective catalyst system for this coupling reaction with low catalyst loading (down to 0.005 mol% Pd).
- Yuen, On Ying,Wong, Shun Man,Chan, Kin Fai,So, Chau Ming,Kwong, Fuk Yee
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supporting information
p. 2826 - 2832
(2015/10/21)
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- A general and highly efficient method for the construction of aryl-substituted N-heteroarenes
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A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides, which is strongly dependent on the molecular structure of solvent. A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides including 2-pyridyl bromides, 3-pyridyl bromides, 3-quinolyl bromides, 5-pyrimidyl bromides and 2-pyrazyl chloride, which is strongly dependent on the molecular structure of solvent.
- Liu, Chun,Han, Na,Song, Xiaoxiao,Qiu, Jieshan
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supporting information; experimental part
p. 5548 - 5551
(2011/02/19)
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- A fast and oxygen-promoted protocol for the ligand-free Suzuki reaction of 2-halogenated pyridines in aqueous media
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A fast protocol has been developed for the construction of 2-aryl-substituted pyridine derivatives by the oxygen-promoted, ligand-free, Pd(OAc)2-catalyzed Suzuki reaction of 2-halogenated pyridines in aqueous isopropanol.
- Liu, Chun,Yang, Weibo
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supporting information; experimental part
p. 6267 - 6269
(2010/02/16)
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- Suzuki coupling of heteroaromatic chlorides using highly electron-donating clickphos ligands
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Using highly electron-rich monophosphine ligands, Suzuki cross-coupling of heteroaromatic chlorides with various boronic acids was carried out in high yields. High yields were also often observed when steric heteroaromatic chlorides were employed in Suzuki cross-coupling reactions.
- Spinella, Stephen M.,Guan, Zheng-Hui,Chen, Jian,Zhang, Xumu
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experimental part
p. 3094 - 3098
(2009/12/28)
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- Heterocyclic derivatives in the treatment of Ischaemia and related diseases
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Compounds of the formula: STR1 wherein A, R1, R2, R3 and m are defined as in the specification or a pharmaceutically acceptable acid addition salt or N-oxide thereof, are calcium and sodium channel antagonists useful for treating mammals having a variety of disease states, such as stroke, epilepsy, hypertension, angina, migraine, arrhythmia, thrombosis, embolism, and also for treatment of spinal injuries.
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