- Ruthenium catalyzed β-selective alkylation of vinylpyridines with aldehydes/ketonesviaN2H4mediated deoxygenative couplings
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Umpolung (polarity reversal) tactics of aldehydes/ketones have greatly broadened carbonyl chemistry by enabling transformations with electrophilic reagents and deoxygenative functionalizations. Herein, we report the first ruthenium-catalyzed β-selective alkylation of vinylpyridines with both naturally abundant aromatic and aliphatic aldehyde/ketonesviaN2H4mediated deoxygenative couplings. Compared with one-electron umpolung of carbonyls to alcohols, this two-electron umpolung strategy realized reductive deoxygenation targets, which were not only applicable to the regioselective alkylation of a broad range of 2/4-alkene substituted pyridines, but also amenable to challenging 3-vinyl and steric-embedded internal pyridines as well as their analogous heterocyclic structures.
- Lv, Leiyang,Li, Chao-Jun
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p. 2870 - 2875
(2021/03/14)
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- ZnMe2-Mediated, Direct Alkylation of Electron-Deficient N-Heteroarenes with 1,1-Diborylalkanes: Scope and Mechanism
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The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe2-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity. The reaction scope is remarkably broad, and a range of C2- or C4-alkylated electron-deficient N-heteroarenes are obtained in good yields. Experimental and computational mechanistic studies imply that ZnMe2 serves not only as an activator of 1,1-diborylalkanes to generate (α-borylalkyl)methylalkoxy zincate, which acts as a Lewis acid to bind to the nitrogen atom of the heterocycles and controls the regioselectivity, but also as an oxidant for rearomatizing the dihydro-N-heteroarene intermediates to release the product.
- Jo, Woohyun,Baek, Seung-Yeol,Hwang, Chiwon,Heo, Joon,Baik, Mu-Hyun,Cho, Seung Hwan
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supporting information
p. 13235 - 13245
(2020/09/01)
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- Potassium Amide-Catalyzed Benzylic C?H Bond Addition of Alkylpyridines to Styrenes
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The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide-catalyzed selective benzylic C?H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Br?nsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity.
- Zhai, Dan-Dan,Zhang, Xiang-Yu,Liu, Yu-Feng,Zheng, Lei,Guan, Bing-Tao
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supporting information
p. 1650 - 1653
(2018/01/27)
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- Switchable Selectivity in the Pd-Catalyzed Alkylative Cross-Coupling of Esters
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The Pd-catalyzed cross-coupling of phenyl esters and alkyl boranes is disclosed. Two reaction modes are rendered accessible in a selective fashion by interchange of the catalyst. With a Pd-NHC system, alkyl ketones can be prepared in good yields via a Suzuki-Miyaura reaction proceeding by activation of the C(acyl)-O bond. Use of a Pd-dcype catalyst enables alkylated arenes to be synthesized by a modified pathway with extrusion of CO. Applications of this divergent coupling strategy and the origin of the switchable selectivity are discussed.
- Masson-Makdissi, Jeanne,Vandavasi, Jaya Kishore,Newman, Stephen G.
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p. 4094 - 4098
(2018/07/15)
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- Coupling of Challenging Heteroaryl Halides with Alkyl Halides via Nickel-Catalyzed Cross-Electrophile Coupling
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Despite their importance, the synthesis of alkylated heterocycles from the cross-coupling of Lewis basic nitrogen heteroaryl halides with alkyl halides remains a challenge. We report here a general solution to this challenge enabled by a new collection of ligands based around 2-pyridyl-N-cyanocarboxamidine and 2-pyridylcarboxamidine cores. Both primary and secondary alkyl halides can be coupled with 2-, 3-, and 4-pyridyl halides as well as other more complex heterocycles in generally good yields (41 examples, 69% ave yield).
- Hansen, Eric C.,Li, Changfeng,Yang, Sihang,Pedro, Dylan,Weix, Daniel J.
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p. 7085 - 7092
(2017/07/26)
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- Synthesis and utility of dihydropyridine boronic esters
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When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine, and piperidine products.
- Panda, Santanu,Coffin, Aaron,Nguyen, Q. Nhu,Tantillo, Dean J.,Ready, Joseph M.
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supporting information
p. 2205 - 2209
(2016/02/18)
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- Nickel-catalysed para-CH activation of pyridine with switchable regioselective hydroheteroarylation of allylarenes
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para-CH activation of pyridine with allylbenzene is described by Ni/Al cooperative catalysis in combination with a bulkier NHC ligand and a Lewis acid, leading to linear hydroheteroarylation products. Interestingly, the branch selectivity can be achieved by using the combination of a less sterically hindered amino-NHC ligand and AlMe3 through tandem reaction of facile alkene isomerization followed by a slow CH bond activation process.
- Lee, Wei-Chih,Chen, Chien-Hung,Liu, Cheng-Yuan,Yu, Ming-Shiuan,Lin, Yung-Huei,Ong, Tiow-Gan
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supporting information
p. 17104 - 17107
(2015/12/01)
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- Selective C-4 alkylation of pyridine by nickel/Lewis acid catalysis
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Direct C-4-selective addition of pyridine across alkenes and alkynes is achieved for the first time by nickel/Lewis acid cooperative catalysis with an N-heterocyclic carbene ligand. A variety of substituents on both alkenes and pyridine are tolerated to give linear 4-alkylpyridines in modest to good yields. The addition across styrene, on the other hand, gives branched 4-alkylpyridines. A single example of C-4-selective alkenylation is also described.
- Nakao, Yoshiaki,Yamada, Yuuya,Kashihara, Natsuko,Hiyama, Tamejiro
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supporting information; experimental part
p. 13666 - 13668
(2010/11/24)
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- Nickel-catalyzed cross-coupling of potassium aryl- and heteroaryltrifluoroborates with unactivated alkyl halides
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A method for the cross-coupling of alkyl electrophiles with various potassium aryl- and heteroaryltrifluoroborates has been developed. Nearly stoichiometric amounts of organoboron species could be employed to cross-couple a large variety of challenging heteroaryl nucleophiles. Several functional groups were tolerated on both the electrophilic and the nucleophilic partners. Chemoselective reactivity of C(sp3) - Br bonds in the presence of C(sp2) - Br bonds was achieved.
- Molander, Gary A.,Argintaru, O. Andreea,Aron, Ioana,Dreher, Spencer D.
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supporting information; experimental part
p. 5783 - 5785
(2011/03/18)
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- Zn-promoted regio- and sequence-selective one-pot joining reactions of three components: vinylpyridines, alkyl iodides, and carbonyl compounds (or nitriles)
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Addition of alkyl iodides (3) into the solution containing 2-(or 4-)vinylpyridine (1 or 2) and carbonyl compounds (6) in the presence of Zn-powder (99.9%) in acetonitrile under refluxing brought about regio- and sequence-selective joining reaction of thre
- Mineyama, Kenji,Maekawa, Hirofumi,Kohsaka, Akihiro,Yamamoto, Yoshimasa,Nishiguchi, Ikuzo
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experimental part
p. 7706 - 7711
(2009/12/04)
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- Intramolecular cation-π interactions control the conformation of nonrestricted (phenylalkyl)pyridines
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NOEsy and fluorescence spectroscopy reveal that conversion of conformationally flexible (phenylalkyl)pyridines into their corresponding N-methyl-pyridinium iodides results in intramolecular π-stacking. The Royal Society of Chemistry.
- Richter, Isabella,Minari, Jusaku,Axe, Philip,Lowe, John P.,James, Tony D.,Sakurai, Kazuo,Bull, Steven D.,Fossey, John S.
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p. 1082 - 1084
(2008/12/20)
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- 3-thienyl and 3-furanyl pyrrolidine modulators of chemokine receptor activity
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The present invention is directed to pyrrolidine compounds of the formula I: (wherein R1, R2, R3, R4c, R4d, and R4fare defined herein) which are useful as modulators of chemokine receptor activity. In particular, these compounds are useful as modulators of the chemokine receptors CCR-3 and/or CCR-5.
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- Efficient catalytic conversion of pyridine N-oxides to pyridine with an oxorhenium(V) catalyst
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(Equation Presented) The compound CH3Re(O)(SR)2PPh3, where (SR)2 represents the dianion of 2-(mercaptomethyl)thiophenol, catalyzes the rapid and efficient transfer of an oxygen atom from a wide range of ring-substituted pyridine N-oxides to triphenylphosphine, yielding the pyridines in high yield.
- Wang, Ying,Espenson, James H.
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p. 3525 - 3526
(2007/10/03)
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- Synthesis of (+/-)--9-halogeno-2-methyl-1,2,3,4,4a,5,6,10b,11,12,12a-dodecahydronaphthoisoquinolines
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Treatment of 5-(2-arylethyl)-1,2,3,4,5,6,7,8-octahydroisoquinolines with 48percent HBr resulted in isomerisation of the double bond and subsequent cyclisation at position 6 of the octahydroisoquinoline ring system to give (+/-)--9-halogeno-2-methyl-1,2,3,4,4a,4b,5,6,10b,11,12,12a-dodecahydronaphtho2,1-f>isoquinolines.The products obtained represent novel analogues of aza-D-homoestranes.No reaction was observed with the corresponding 5,5-disubstituted octahydroisoquinolines.An X-ray crystallographic study of compound 10 (X = Br) is described.
- Patrick, Graham L.
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p. 1273 - 1280
(2007/10/02)
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- Intramolecular Alkylations of Aromatic Compounds, XVIII: Synthesis of 3,4-Dihydro-1'-methylspiro
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Refluxing the tetrahydroyridines 10 in hydrobromic acid gives the title compounds 12 stereoselectively.Their structures and configurations were confirmed by NMR spectroscopy and X-ray analysis.The tetrahydropyridines 10 were prepared from the pyridinecarbonitriles 5 and Grignard reagents 6 by standard methods.
- Reimann, Eberhard,Speckbacher, Johann,Lotter, Hermann
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p. 385 - 393
(2007/10/02)
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