- 2-Position-Selective Trifluoromethylthiolation of Six-Membered Heteroaromatic Compounds
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The regioselective C-H trifluoromethylthiolation of six-membered heteroaromatic compounds via nucleophilic attack of a CF3S source on the electrophilically activated six-membered heteroaromatic ring was developed. The reaction proceeds in good yield with good functional group tolerance, even on a gram-scale. The key to the successful regioselective transformation is the presence of an additive (2,4-dinitrobenzenesulfonyl chloride). The regioselective trifluoromethylthiolation of quinidine derivative is also demonstrated. Trifluoromethylthiolation, followed by S-oxidation, affords the corresponding sulfones.
- Muta, Ryuhei,Torigoe, Takeru,Kuninobu, Yoichiro
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Read Online
- Dehydrogenative etherification homocoupling of heterocyclic N-oxides
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A novel approach was developed for the dehydrogenative etherification homocoupling of heterocyclic N-oxides in the presence of silver oxide and PyBroP. Various substrates were well tolerated and the desired products were obtained in moderate to good yields. Generally, this reaction features excellent functional group compatibility, broad substrate scope and good regioselectivity.
- Zhang, Dong,Qiao, Kai,Yuan, Xin,Zheng, Mingwei,Fang, Zheng,Wan, Li,Guo, Kai
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Read Online
- Arylation of pyridine N-oxides via a ligand-free Suzuki reaction in water
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We report a practical and highly efficient protocol for the arylation of pyridine N-oxides with arylboronic acid through palladium-catalyzed Suzuki reaction in water. This ligand-free Suzuki reaction is performed in the presence of diisopropylamine and gi
- Liu, Chun,Zhang, Shao-Ke,Zhang, Yi-Xia,Jin, Zi-Lin
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Read Online
- Copper-Catalyzed Regioselective Cascade Alkylation and Cyclocondensation of Quinoline N-Oxides with Diazo Esters: Direct Access to Conjugated π-Systems
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An inexpensive copper-catalyzed cascade regioselective alkylation, followed by cyclocondensation of quinoline N-oxides with α-diazo esters has been achieved successfully to provide heteroarene-containing conjugated π-systems. The developed method is simple, straightforward, and economical with a broad range of substrate scope. The dual role of copper catalyst in the C?H bond functionalization and in Lewis acid-promoted cyclization was explored.
- Biswas, Aniruddha,Karmakar, Ujjwal,Pal, Arun,Samanta, Rajarshi
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- 2-Position-selective C[sbnd]H fluoromethylation of six-membered heteroaryl N-oxides with (fluoromethyl)triphenylphosphonium iodide
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A mild and efficient method for the regioselective C[sbnd]H fluoromethylation of heteroaryl N-oxides with (fluoromethyl)triphenylphosphonium iodide is presented. With LiOt-Bu as the base and DMSO as the solvent, this reaction delivers a series of C2-fluor
- Hu, Chen-Chen,Hu, Wei-Qiang,Qing, Feng-Ling,Xu, Xiu-Hua
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Read Online
- A Photosensitizer-Free Radical Cascade for Synthesizing CF3-Containing Polycyclic Quinazolinones with Visible Light
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Herein, we report an efficient photoinduced radical tandem trifluoromethylation/cyclization reaction of N-cyanamide alkenes for the synthesis of functionalized quinazolinones. Importantly, the reaction is carried out under mild conditions without any addi
- Hu, Qiang,Yu, Wan-Lei,Luo, Yong-Chun,Hu, Xiu-Qin,Xu, Peng-Fei
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supporting information
p. 1493 - 1501
(2022/02/07)
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- Copper/manganese oxide catalyzed regioselective amination of quinoline N-oxides: An example of synergistic cooperative catalysis
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An atom economical and efficient protocol for C-2 amination of quinoline N-oxides using our synthesized recyclable heterogeneous Cu–MnO catalyst has been reported here. Direct C[sbnd]H aminations of heterocyclic N-oxides with secondary amine were carried out under base, and ligand-free conditions in good to excellent yields. The major advantage is that air is used as a sole oxidant and our catalyst is recycled several times.
- Sahoo, Tapan,Thakur, Dinesh,Panda, Asit Baran,Ghosh, Subhash Chandra
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supporting information
(2021/09/29)
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- Visible-light-promoted c2 selective arylation of quinoline and pyridine n-oxides with diaryliodonium tetrafluoroborate
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A protocol of visible-light-promoted C2 selective arylation of quinoline and pyridine N-oxides, with diaryliodonium tetrafluoroborate as an arylation reagent, using eosin Y as a photocatalyst for the construction of N-heterobiaryls was presented. This met
- Li, Dazhi,Liang, Ce,Jiang, Zaixing,Zhang, Junzheng,Zhuo, Wang-Tao,Zou, Fan-Yue,Wang, Wan-Peng,Gao, Guo-Lin,Song, Jinzhu
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p. 2733 - 2742
(2020/03/11)
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- Preparation method of 2-phenyl substituted pyridine nitrogen oxide compound
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The invention discloses a preparation method of a 2-phenyl substituted pyridine nitrogen oxide compound, relates to a preparation method of a pyridine nitrogen oxide derivative, and aims to solve thetechnical problems of flammability, explosiveness, harsh reaction conditions and poorer regioselectivity of a catalyst in the conventional direct selective functionalization method. The method comprises the following steps: adding the pyridine nitrogen oxide derivative, diphenyl iodide tetrafluoroborate, an eosin Y catalyst, an alkali and an additive into a transparent reactor at room temperature,and sealing; replacing air in the reactor with nitrogen to form a nitrogen atmosphere, injecting a solvent, and uniformly mixing; irradiating the reactor with blue LEDs lamp light for reaction; afterthe reaction is finished, removing the solvent through rotary evaporation, and then performing separation and purification of prefabricated silica gel column chromatography to obtain the 2-phenyl substituted pyridine nitrogen oxide compound, and the structural formula of the 2-phenyl substituted pyridine nitrogen oxide compound is as shown in the specification, R1 is hydrogen, alkyl, nitrile group, halogen, phenyl or nitro; the 2-phenyl substituted pyridine nitrogen oxide compound can be used in the fields of screening of drug lead compounds or biological activity test and research.
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Paragraph 0029-0038
(2020/03/09)
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- Visible-Light-Induced ortho-Selective Migration on Pyridyl Ring: Trifluoromethylative Pyridylation of Unactivated Alkenes
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The photocatalyzed ortho-selective migration on a pyridyl ring has been achieved for the site-selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF3 radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho-position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well-suited for addition to the C2-position of pyridinium salts to ultimately provide synthetically valuable C2-fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P-centered radicals. The utility of this transformation was further demonstrated by the late-stage functionalization of complex bioactive molecules.
- Jeon, Jinwon,He, Yu-Tao,Shin, Sanghoon,Hong, Sungwoo
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supporting information
p. 281 - 285
(2019/11/26)
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- Decarboxylative Arylation of Pyridine 1-Oxides and Anilides with Benzoic Acid via Palladium-Catalyzed C–H Functionalization
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A novel method for the palladium-catalyzed decarboxylative ortho C–H bond arylation of pyridine 1-oxides and anilides with benzoic acids as aryl sources is described. The established methodology provides a direct approach for the synthesis of 2-arylpyridine 1-oxides and 2-aryl anilides in good isolated yields.
- Dabiri, Minoo,Alavioon, Seyed Iman,Movahed, Siyavash Kazemi
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supporting information
p. 1479 - 1487
(2019/02/19)
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- Strategic Approach on N-Oxides in Gold Catalysis – A Case Study
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An extensive kinetic study of selected key reactions of (oxidative) gold catalysis concentrates on the decrease of the catalytic activity due to inhibition of the gold(I) catalyst caused by pyridine derivatives that are obtained as by-products if N-oxides are applied as oxygen donors. The choice of the examined pyridine derivatives and their corresponding N-oxides has been made regardless of their commercial availability; particular attention has been paid to the practical benefit which up to now has been neglected in most of the reaction screenings. The test reactions were monitored by GC and 1H NMR spectroscopy. The received reaction constants provide information concerning a correlation between the electronic structure of the heterocycle and the catalytic activity. Based on the collected kinetic data, it was possible to develop a basic set of three N-oxides which have to be taken into account in further oxidative gold(I)-catalyzed reactions. (Figure presented.).
- Schie?l, Jasmin,Stein, Philipp M.,Stirn, Judith,Emler, Kirsten,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 725 - 738
(2018/10/20)
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- Regioselective Cyanation of Six-Membered N-Heteroaromatic Compounds Under Metal-, Activator-, Base- and Solvent-Free Conditions
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A regioselective cyanation of heteroaromatic N-oxides with trimethylsilyl cyanide has been developed to obtain 2-substituted N-heteroaromatic nitrile without the requirement of any external activator-, metal-, base-, and solvent. The present protocol is a straightforward, one-pot heteroaromatic C?H cyanation process, and proceeds smoothly in conventional heating but also under microwave irradiation with shorter reaction times. This approach now allows access to a broad class of quinoline N-oxides and other heteroarene N-oxides with high to good yields and can also be scaled up to obtain gram quantities. Further application of this process was observed and utilized in late-stage cyanation of the anti-malarial drug quinine as well as transformation of the 2-cyanoazines to a series of biologically important molecules. Based on the experimental observations, a plausible mechanism has also been proposed highlighting the dual role of trimethylsilyl cyanide as a nitrile source and as an activating agent. (Figure presented.).
- Sarmah, Bikash Kumar,Konwar, Monuranjan,Bhattacharyya, Dipanjan,Adhikari, Priyanka,Das, Animesh
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supporting information
p. 5616 - 5625
(2019/11/22)
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- Electrochemical Deoxygenation of N-Heteroaromatic N -Oxides
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An electrochemical method for the deoxygenation of N-heteroaromatic N -oxide to give the corresponding N-heteroaromatics has been developed. Several classes of N-heterocycles such as pyridine, quinoline, isoquinoline, and phenanthridine are tolerated. The electrochemical reactions proceed efficiently in aqueous solution without the need for transition-metal catalysts and waste-generating reducing reagents.
- Xu, H.-C.,Xu, P.
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supporting information
p. 1219 - 1221
(2019/06/08)
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- Pd-Catalyzed Direct C-H Alkenylation and Allylation of Azine N -Oxides
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A Pd-catalyzed direct C2-alkenylation of azine N-oxides with allyl acetate is disclosed. The products are formed through an allylation/isomerization cascade process. The use of a tri-tert-butylphosphonium salt as the ligand precursor and KF is mandatory for optimal yields. When cinnamyl acetate is used, the same catalytic system promotes C2-cinnamylation of the azine N-oxide without subsequent isomerization. A mechanism is proposed on the basis of experimental studies and DFT calculations.
- Roudesly, Fares,Veiros, Luis F.,Oble, Julie,Poli, Giovanni
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supporting information
p. 2346 - 2350
(2018/04/30)
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- Transition-Metal-Free Regioselective Alkylation of Quinoline N-Oxides via Oxidative Alkyl Migration and C?C Bond Cleavage of tert-/sec-Alcohols
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An unprecedented C2-alkylation of quinoline N-oxide derivatives via C?C bond activation of tert- and sec-alkyl alcohol is described using hypervalent iodine (III) reagent PhI(OAc)2 (PIDA). This regioselective alkylation using mild hypervalent iodine reagents is more practical, operationally simple and transition metal free. The reaction proceeds efficiently with a broad range of substrates including quinoline, isoquinoline, and pyridine N-oxides using a variety of tert-/sec- alcohols. From experimental outcome, we also propose a rationalized mechanism, mediated by PIDA. (Figure presented.).
- Sen, Chiranjit,Ghosh, Subhash C.
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supporting information
p. 905 - 910
(2018/01/11)
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- Nickel-catalyzed C–H trifluoromethylation of pyridine N-oxides with Togni's reagent
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The first nickel-catalyzed C–H trifluoromethylation of pyridine N-oxides with Togni's reagent has been achieved. Trifluoromethylation proceeds smoothly under mild conditions with moderate functional group compatibility. Notable advantages of this method include the using of low cost of nickel catalyst, and its simple convenient operation.
- Gao, Xianying,Geng, Yang,Han, Shuaijun,Liang, Apeng,Li, Jingya,Zou, Dapeng,Wu, Yangjie,Wu, Yusheng
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supporting information
p. 1551 - 1554
(2018/03/23)
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- Visible-Light-Induced C2 Alkylation of Pyridine N-Oxides
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A photoredox catalytic method has been developed for the direct C2 alkylation of pyridine N-oxides. This reaction is compatible with a range of synthetically relevant functional groups for providing efficient synthesis of a variety of C2-alkylated pyridine N-oxides under mild conditions. Mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.
- Zhang, Wen-Man,Dai, Jian-Jun,Xu, Jun,Xu, Hua-Jian
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p. 2059 - 2066
(2017/02/26)
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- Pd(II)-catalyzed monoarylation of 2-phenylpyridine N-oxide with iodobenzene in water
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A Pd(II)-catalyzed activation and arylation of C(sp2)–H bond directed by pyridine N-oxide in water is achieved with high regioselectivity to form monoarylated products in yields up to 91%. The wide substrate scope highlights the flexibility of the catalyst. The reaction mechanism was proposed and the application of this method was taken as an example by the synthesis of COX-2 inhibitor analog.
- Zhang, Wei,Li, Zhengkai,Zhang, Yihan,Yang, Li,Zhou, Xiangge
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supporting information
p. 793 - 802
(2017/04/06)
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- Copper-Catalyzed Direct, Regioselective Arylamination of N-Oxides: Studies to Access Conjugated π-Systems
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An efficient copper(I)-catalyzed direct regioselective arylamination of various heterocyclic N-oxides was achieved successfully under redox-neutral conditions using anthranils as arylaminating reagents. The developed protocol is simple, straightforward, and economic with a broad range substrate scope. The dual functional groups in the final molecules were utilized to construct structurally and functionally diverse nitrogen-containing organic π-conjugated systems.
- Biswas, Aniruddha,Karmakar, Ujjwal,Nandi, Shiny,Samanta, Rajarshi
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p. 8933 - 8942
(2017/09/11)
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- 2,2′-Homocoupled Azine N,N′-Dioxides or Azine N-Oxides: CDC- or SNAr-Controlled Chemoselectivity
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An unprecedented Cu(OAc)2- and LiOtBu-mediated homocoupling of azine N-oxides to yield 2,2′-azine N,N′-dioxides is reported. This is the first instance in which copper has been used to catalyze the homodimerization reaction, especially of 2-phenylpyridine N-oxides. In the absence of catalytic copper, the reaction follows an alternative pathway, and instead of dioxides it yields 2,2′-azine N-monoxides. This latter protocol works efficiently with a range of N-heterocyclic oxides of pyridine, 2-phenylpyridine, quinoline and N-aryl-1,2,3-triazole. It is scalable, offers high regioselectivity and gives the products in moderate to high yields. The observed chemoselectivity between the copper-assisted and copper-free protocols is routed through oxidative cross-dehydrogenative coupling (CDC) and nucleophilic aromatic substitution of hydrogen (SNAr) pathways, respectively.
- Jha, Abadh Kishor,Jain, Nidhi
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p. 4765 - 4772
(2017/09/07)
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- Palladium-catalyzed direct C-H arylation of pyridine N-oxides with potassium aryl- and heteroaryltrifluoroborates
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An efficient ligand-free Pd(OAc)2-catalyzed selective arylation of pyridine N-oxides using potassium (hetero)aryltrifluoroborates as coupling partners via C-H bond activation was achieved in the presence of TBAI. This approach has a broad subst
- Li, Mengli,Li, Xing,Chang, Honghong,Gao, Wenchao,Wei, Wenlong
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supporting information
p. 2421 - 2426
(2016/03/01)
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- Metal-Free, Phosphonium Salt-Mediated Sulfoximination of Azine N-Oxides: Approach for the Synthesis of N-Azine Sulfoximines
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Herein, we report a simple and metal-free method for the synthesis of N-azine sulfoximines by the nucleophilic substitution of azine N-oxides with NH-sulfoximines. The present method works at room temperature with wide functional group compatibility and gives several unprecedented N-azine sulfoximines. The reaction conditions were also found suitable with enantiopure substrates and furnished products without any racemization. It also finds an application in the sulfoximination of azine-based functional molecules such as 2,2′-bipyridine, 1,10-phenanthroline, and quinine.
- Aithagani, Sravan Kumar,Kumar, Mukesh,Yadav, Mahipal,Vishwakarma, Ram A.,Singh, Parvinder Pal
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p. 5886 - 5894
(2016/07/23)
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- Recent developments in the chemistry of heteroaromatic N -oxides
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Selected developments in the chemistry of heteroaromatic N-oxides since 2001 are presented in this review. The use of these N-oxides, both in late-transition-metal-catalyzed oxidations of carbon-carbon triple bonds and in regioselective C-H functionalizations of the heteroarene, are contemporary topics of interest and the focus of the discussion. 1 Introduction 2 Synthesis of Heteroaromatic N-Oxides 2.1 Direct Oxidation of Hindered Heteroarenes 2.2 Through Construction of Heteroaromatic Rings 3 Heteroaromatic N-Oxides as Oxidants 3.1 Alkyne Oxidation 3.2 Allene Oxidation 3.3 Carbene Oxidation 4 Heteroaromatic N-Oxides as Substrates 4.1 Deoxygenative ortho-C-H Functionalization with Prior Activation 4.2 Deoxygenative ortho-C-H Functionalization with Nonstabilized Carbanions 4.3 Nondeoxygenative C-H Functionalization 4.3.1 ortho-C-H Functionalization 4.3.2 N-Oxide Directed ortho-Alkyl C-H Functionalization 4.3.3 N-Oxide Directed Remote C-H Functionalization 4.4 1,3-Dipolar Cycloaddition 5 Conclusion and Outlook.
- Wang, Youliang,Zhang, Liming
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- Pd-catalyzed decarboxylative cross-coupling of 2-carboxyazine N-oxides with various (hetero)aryl halides
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Decarboxylative cross-coupling reactions of substituted 2-carboxyazine N-oxides, with a variety of (hetero)aryl halides, by bimetallic Pd 0/CuI and Pd0/AgI catalysis are reported. Two possible pathways, a conven
- Rouchet, Jean-Baptiste,Schneider, Cedric,Spitz, Cedric,Lefevre, Johan,Dupas, George,Fruit, Corinne,Hoarau, Christophe
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supporting information
p. 3610 - 3615
(2014/04/03)
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- Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles
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A Mo/P catalytic system for an efficient gram-scale oxidation of a variety of nitrogen heterocycles to N-oxides with hydrogen peroxide as terminal oxidant has been investigated. Combined spectroscopic and crystallographic studies point to the tetranuclear Mo4P peroxo complex as one of the active catalytic species present in the solution. Based on this finding an optimized catalytic system has been developed. The utility and chemoselectivity of the catalytic system has been demonstrated by the synthesis of over 20 heterocyclic N-oxides.
- Larionov, Oleg V.,Stephens, David,Mfuh, Adelphe M.,Arman, Hadi D.,Naumova, Anastasia S.,Chavez, Gabriel,Skenderi, Behije
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p. 3026 - 3036
(2014/05/06)
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- Substitution of the nitro group with Grignard reagents: Facile arylation and alkenylation of pyridine N-oxides
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The unprecedented substitution of a nitro group with aryl or alkenyl groups of Grignard reagents affords 2-aryl or alkenylpyridine N-oxides in modest to high yields with high chemoselectivity. This protocol allows a simple and clean synthesis of various 2
- Zhang, Fang,Zhang, Song,Duan, Xin-Fang
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p. 5618 - 5620
(2013/01/15)
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- Silver-catalyzed 2-pyridyl arylation of pyridine N-oxides with arylboronic acids at room temperature
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A novel direct arylation of pyridine N-oxides with arylboronic acids through C-H functionalization has been developed. This new reaction is performed at room temperature using catalytic silver(I) nitrate in the presence of potassium persulfate and give 2-
- Mai, Wenpeng,Yuan, Jinwei,Li, Zhicheng,Sun, Gangchun,Qu, Lingbo
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supporting information; experimental part
p. 145 - 149
(2012/02/04)
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- Reduction of amine N-oxides by diboron reagents
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Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis- (pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N-dioxide of (S)-(-)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR. (Figure presented) ; 2011 American Chemical Society.
- Kokatla, Hari Prasad,Thomson, Paul F.,Bae, Suyeal,Doddi, Venkata Ramana,Lakshman, Mahesh K.
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experimental part
p. 7842 - 7848
(2011/12/01)
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- COPPER-CATALYZED C-H BOND ARYLATION
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The present invention is a one-step method for efficiently converting carbon-hydrogen bonds into carbon-carbon bonds using a combination of aryl halides, a substrate, and a copper salt as catalyst. This method allows faster introduction of complex molecular entities, a process that would otherwise require many more steps. This invention is particularly relevant for the organic synthesis of complex molecules such as, but not limited to, pharmacophores and explosives.
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Page/Page column 23
(2009/04/24)
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- A simple base-mediated halogenation of acidic sp2 C-H bonds under noncryogenic conditions
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(Chemical Equation Presented) A new method has been developed for in situ halogenation of acidic sp2 carbon-hydrogen bonds in heterocycles and electron-deficient arenes. Either selective monohalogenation or one-step exhaustive polyhalogenation is possible for substrates possessing several C-H bonds that are flanked by electron-withdrawing groups. For the most acidic arenes, such as pentafluorobenzene, K3PO4 base can be employed instead of BuLi for metalation/halogenation sequences.
- Do, Hien-Quang,Daugulis, Olafs
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supporting information; experimental part
p. 421 - 423
(2009/07/04)
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- A general method for copper-catalyzed arylation of arene C-H bonds
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A general method for copper-catalyzed arylation of sp2 C-H bonds with pKa's below 35 has been developed. The method employs aryl halide as the coupling partner, lithium alkoxide or K3PO4 base, and DMF, DMPU, or mixed DMF/xylenes solvent. A variety of electron-rich and electron-poor heterocycles such as azoles, caffeine, thiophenes, benzofuran, pyridine oxides, pyridazine, and pyrimidine can be arylated. Furthermore, electron-poor arenes possessing at least two electron-withdrawing groups on a benzene ring can also be arylated. Two arylcopper-phenanthroline complex intermediates were independently synthesized.
- Do, Hien-Quang,Khan, Rana M. Kashif,Daugulis, Olafs
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supporting information; experimental part
p. 15185 - 15192
(2009/03/12)
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- Palladium-catalyzed C-H functionalization of pyridine N-oxides: Highly selective alkenylation and direct arylation with unactivated arenes
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Two catalytic protocols of the oxidative C-C bond formation have been developed on the basis of the C-H bond activation of pyridine N-oxides. Pd-catalyzed alkenylation of the N-oxides proceeds with excellent regio-, stereo-, and chemoselectivity, and the
- Seung, Hwan Cho,Seung, Jun Hwang,Chang, Sukbok
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supporting information; scheme or table
p. 9254 - 9256
(2009/02/03)
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- 2-AMINOCARBONYL-PYRIDINE DERIVATIVES
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The present invention relates to 2-aminocarbonyl-pyridine derivatives and their use as P2Yi2 receptor antagonists in the treatment and/or prevention of peripheral vascular, of visceral-, hepatic- and renal-vascular, of cardiovascular and of cerebrovascular diseases or conditions associated with platelet aggregation, including thrombosis in humans and other mammals.
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Page/Page column 109
(2008/06/13)
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- N-oxidation of 2-substituted pyridines and quinolines by dimethyldioxirane: Kinetics and steric effects
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The oxidation of 2-substituted pyridines and selected N-containing aromatic heterocycles by dimethyldioxirane (1) produced the corresponding N-oxides as the sole products, quantitatively in most cases. The second order rate constants for N-oxidation by 1 in dried acetone at 23°C were determined for a series of 2-substituted pyridines 2-10, quinolines 11-14 and isoquinolines 15,16. An excellent correlation of log k2 with Taft (σ*) constants was obtained for 2-substituted pyridines (R = Me, Et, Prn, Pr i, 3-pentyl) with the exception of the data for 2-f-butylpyridine. The results for the substituted quinolines and isoquinolines followed the same trends observed with the pyridines. Steric effects due to 2-substitution and periinteractions can substantially reduce reactivity. The results provide insights into the geometrical requirements for N-oxidation by dimethyldioxirane.
- Winkeljohn, W. Rucks,Leggett-Robinson, Pamela,Peets, Monique R.,Strekowski, Lucjan,Vasquez, Pedro C.,Baumstark
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- Thiazoles and thiopyridines: Novel series of high affinity h5HT 7 ligands
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A series of thiazole based 5HT7 ligands has been identified from screening. Optimisation of the pendent aryl group and modification of the core gave a related series of high affinity, selective thiopyridine based 5HT7 ligands, the most active of which behaves as a partial agonist.
- Thomson, Christopher G.,Beer, Margaret S.,Curtis, Neil R.,Diggle, Helen J.,Handford, Emma,Kulagowski, Janusz J.
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p. 677 - 680
(2007/10/03)
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- A long-range chiral relay via tertiary amide group in asymmetric catalysis: new amino acid-derived N,P-ligands for copper-catalysed conjugate addition.
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New N,P-ligands 4-6, derived from valinol and prolinol, respectively, have been developed for the asymmetric, copper(I)-catalysed conjugate addition of diethylzinc to unsaturated ketones; the tertiary amide group has been shown to effectively relay the chiral information from the ligand backbone to the active centre.
- Malkov, Andrei V,Hand, John B,Kocovsky, Pavel
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p. 1948 - 1949
(2007/10/03)
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- The palladium catalysed Suzuki coupling of 2- and 4-chloropyridines
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The Suzuki coupling of 2- and 4-chloropyridines with arylboronic acids is successfully performed under Pd(PPh3)4 catalysis. Moderate to good yields are obtained with 4-chloropyridines while 2-chloropyridines give excellent yields. The corresponding pyridine N-oxides react in the same manner. An easy and cheap access to arylpyridines, a class of compound with medicinal interest, is thus achieved.
- Lohse, Olivier,Thevenin, Philippe,Waldvogel, Erwin
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- FURTHER FUNCTIONAL GROUP OXIDATIONS USING SODIUM PERBORATE
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Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N-oxides, and various types of sulfur heterocycles to S,S-dioxides.Nitriles are unaffected by the reagent in acetic acid, but undergo smooth hydration to amides when aqueous methanol is employed as solvent.
- McKillop, Alexander,Kemp, Duncan
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p. 3299 - 3306
(2007/10/02)
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- Studies on Tertiary Amine Oxides. LXXVII. The Pseudo-Gomberg Reaction of 4- and 2-Aminopyridine 1-Oxides
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The 1-oxido-4-pyridyl radical generated by the reaction of 4-aminopyridine 1-oxide with amyl nitrite reacted smoothly with aromatic hydrocarbons, including five-membered heterocycles, i.e. thiophene, fyran and pyrrole, to give the arylated products when acetic acid was used as the solvent.The relative rates of reaction with the 1-oxido-4-pyridyl radical indicated that this radical is electrophilic, and this finding was supported by a comparison of molecular orbital energy levels. 2-Aminopyridine 1-oxide also undergoes a similar reaction.Keywords - pyridine N-oxide; Gomberg reaction; phenylpyridine; thienylpyridine; furylpyridine; 1-methanesulfonyl-pyrrolylpyridine; 1-oxido-4-pyridyl radical; molecular orbital; highperformance liquid chromatography
- Saeki, Seitaro,Kondo, Sachiko,Hayashi, Takaaki,Hamana, Masatomo
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p. 1780 - 1789
(2007/10/02)
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- KINETICS OF THE N OXIDATION OF SOME COMPOUNDS OF THE PYRIDINE SERIES WITH PERBENZOIC ACID IN CHLOROFORM AND AQUEOUS DIOXANE
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A comparative study of the kinetics of the N oxidation of 19 derivatives of the pyridine series with perbenzoic acid in choroform and aqueous dioxane at 20, 25, 30, and 35 deg C was made.The rate constants, the parameters of the Arrhenius equation, and the activation energies of the N oxidation of the indicated monoazines were determined.The scale of the reactivities of the derivatives of the pyridine series was calculated within the framework of the Pearson hard-soft acid-base concept.
- Lohkov, R.E.
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p. 264 - 271
(2007/10/02)
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