- On the metallation of 2-isopropylpyridine
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2-Isopropylpyridine has been successfully metallated and functionalized by using potassium diisopropylamide (KDA). Subsequent functionalization has been achieved with a wide range of electrophiles and good to excellent yields have been obtained. The action of other potassium or sodium bases has also been investigated.
- Pasquinet, Eric,Rocca, Patrick,Marsais, Francis,Godard, Alain,Queguiner, Guy
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- Photoredox-catalysed regioselective synthesis of C-4-alkylated pyridines with N -(acyloxy)phthalimides
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A method of direct C-4 selective alkylation of pyridines under visible light irradiation at room temperature has been reported, using simple maleate-derived pyridinium salts as pyridine precursors and the readily available carboxylic acid-derived N-(acyloxy)phthalimides as alkyl radical precursors, affording good to excellent yields without using stoichiometric oxidants and acids. A broad range of primary, secondary, and tertiary carboxylates can be used as alkylation reagents. Oxidant and acid-sensitive functional groups can be tolerated well. This journal is
- He, Qian,Yang, Chunhao,Zhang, Xiaofei,Zhang, Zhucheng
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supporting information
p. 1969 - 1973
(2022/03/15)
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- A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
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The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- García-Domínguez, Andrés,Gonzalez, Jorge A.,Leach, Andrew G.,Lloyd-Jones, Guy C.,Nichol, Gary S.,Taylor, Nicholas P.
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supporting information
(2022/01/04)
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- Copper-catalyzed cross-coupling of aryl-, primary alkyl-, and secondary alkylboranes with heteroaryl bromides
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A method for the Cu-catalyzed cross-coupling of both aryl and alkylboranes with aryl bromides is described. The method employs an inexpensive Cu-catalyst and functions for a variety of heterocyclic as well as electron deficient aryl bromides. In addition, aryl iodides of varying substitution patterns and electronic properties work well.
- Bergmann, Allison M.,Oldham, Adam M.,You, Wei,Brown, M. Kevin
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supporting information
p. 5381 - 5384
(2018/06/01)
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- Manganese-Catalyzed Kumada Cross-Coupling Reactions of Aliphatic Grignard Reagents with N-Heterocyclic Chlorides
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Herein we report the use of manganese(II) chloride for the catalytic generation of C(sp 2)-C(sp 3) bonds via Kumada cross-coupling. Rapid and selective formation of 2-alkylated N-heterocyclic complexes were observed in high yields with use of 3 mol% MnCl 2 THF 1.6 and under ambient reaction conditions (21 °C, 15 min to 20 h). Manganese-catalyzed cross-coupling is tolerant toward both electron-donating and electron-withdrawing functional groups in the 5-position of the pyridine ring, with the latter resulting in an increased reaction rate and a decrease in the amount of nucleophile required. The use of this biologically and environmentally benign metal salt as a catalyst for C-C bond formation highlights its potential as a catalyst for the late-stage functionalization of pharmaceutically active N-heterocyclic molecules (e.g., pyridine, pyrazine).
- Petel, Brittney E.,Purak, Merjema,Matson, Ellen M.
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supporting information
p. 1700 - 1706
(2018/07/13)
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- Synthesis of a Series of Structurally Diverse MB327 Derivatives and Their Affinity Characterization at the Nicotinic Acetylcholine Receptor
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A novel series of 30 symmetric bispyridinium and related N-heteroaromatic bisquaternary salts with a propane-1,3-diyl linker was synthesized and characterized for their binding affinity at the MB327 binding site of nicotinic acetylcholine receptor (nAChR) from Torpedo californica. Compounds targeting this binding site are of particular interest for research into new antidotes against organophosphate poisoning, as therapeutically active 4-tert-butyl-substituted bispyridinium salt MB327 was previously identified as a nAChR re-sensitizer. Efficient access to the target compounds was provided by newly developed methods enabling N-alkylation of sterically hindered or electronically deactivated heterocycles exhibiting a wide variety of functional groups. Determination of binding affinities toward the MB327 binding site at the nAChR, using a recently developed mass spectrometry (MS)-based Binding Assay, revealed that several compounds reached affinities similar to that of MB327 (pKi=4.73±0.03). Notably, the newly prepared lipophilic 4-tert-butyl-3-phenyl-substituted bispyridinium salt PTM0022 (3 h) was found to have significantly higher binding affinity, with a pKi value of 5.16±0.07, thus representing considerable progress toward the development of more potent nAChR re-sensitizers.
- Rappenglück, Sebastian,Sichler, Sonja,H?fner, Georg,Wein, Thomas,Niessen, Karin V.,Seeger, Thomas,Paintner, Franz F.,Worek, Franz,Thiermann, Horst,Wanner, Klaus T.
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supporting information
p. 1806 - 1816
(2018/09/11)
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- Iron-Catalyzed Isopropylation of Electron-Deficient Aryl and Heteroaryl Chlorides
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Traditional methods for the preparation of secondary alkyl-substituted aryl and heteroaryl chlorides challenge both selectivity and functional group tolerance. This contribution describes the use of statistical design of experiments to develop an effective procedure for the preparation of isopropyl-substituted (hetero)arenes with minimal isopropyl to n-propyl isomerization. The reaction tolerates electronically diverse aryl chloride coupling partners, with excellent conversion observed for strongly electron-deficient aromatic rings, such as esters and amides. Electron-rich systems, including methyl- and methoxy-substituted aryl chlorides, were found to be less reactive. Furthermore, the reaction was found to be most successful when heteroaryl chlorides were submitted to the cross-coupling protocol. By mapping substituent effects on reaction selectivity, we were able to show that electron-deficient aryl chlorides are essential for efficient coupling, and use electronic structure calculations to predict the likelihood of successful coupling through the estimation of the electron affinity of each aryl chloride. Moderate isolated yields were achieved with selected aryl chlorides, and moderate to good isolated yields were obtained for all the heteroaryl chlorides coupled. Excellent selectivity was observed when a 2,6-dichloroquinoline was used, allowing mono-substitution on a challenging substrate. (Figure presented.).
- Sanderson, James N.,Dominey, Andrew P.,Percy, Jonathan M.
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p. 1007 - 1017
(2017/03/27)
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- Magnesiation of N-Heterocycles Using i-PrMgCl · LiCl and catalytic diisopropylamine
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The direct magnesiation of various N-heterocyclic compounds with i-PrMgCl · LiCl and catalytic diisopropylamine allows for preparation of 2-substituted pyrroles, imidazole, indoles, and benzimidazoles, in moderate to good yields. The magnesiated substrates canreadily undergo a Kumada-type coupling with iodo-aryls in the presence of catalytic Pd(PPh3)4.
- Nxumalo,Dinsmore
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supporting information
p. 2478 - 2484
(2015/11/10)
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- Asymmetric Hydrogenation of Pyridinium Salts with an Iridium Phosphole Catalyst
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Iridium-catalyzed asymmetric hydrogenation of N-alkyl-2-alkylpyridinium salts provided 2-aryl-substituted piperidines with high levels of enantioselectivity. Simple benzyl and other alkyl groups successfully activated the challenging pyridine substrates toward hydrogenation. The use of the unusual chiral-phosphole-based MP2-SEGPHOS was the key to the success of this approach which provides a versatile and practical procedure for the synthesis of chiral piperidines. Ring to ring: Simple N-benzyl and N-alkyl groups successfully activated pyridine substrates toward hydrogenation. The use of the unusual chiral phosphole-based ligand L was the key to the success of this approach, which provides a versatile and practical procedure for the synthesis of chiral piperidines. cod=1,5-cyclooctadiene.
- Chang, Mingxin,Huang, Yuhua,Liu, Shaodong,Chen, Yonggang,Krska, Shane W.,Davies, Ian W.,Zhang, Xumu
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supporting information
p. 12761 - 12764
(2016/02/18)
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- Bis(phosphine)cobalt dialkyl complexes for directed catalytic alkene hydrogenation
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Planar, low-spin cobalt(II) dialkyl complexes bearing bidentate phosphine ligands, (P - P)Co-(CH2SiMe3)2, are active for the hydrogenation of geminal and 1,2-disubstituted alkenes. Hydrogenation of more hindered internal and endocyclic trisubstituted alkenes was achieved through hydroxyl group activation, an approach that also enables directed hydrogenations to yield contrasteric isomers of cyclic alkanes.
- Friedfeld, Max R.,Margulieux, Grant W.,Schaefer, Brian A.,Chirik, Paul J.
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supporting information
p. 13178 - 13181
(2015/03/30)
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- Nickel-catalyzed reductive alkylation of halogenated pyridines with secondary alkyl bromides
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This article highlights Ni-catalyzed cross-electrophile coupling of halogenated pyridines with secondary alkyl bromides using zinc as the terminal reductant. With this protocol, we have successfully achieved different alkyl-substituted pyridines in modera
- Liu, Huiyan,Liang, Zhuye,Qian, Qun,Lin, Kunhua
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supporting information
p. 2999 - 3007
(2014/10/16)
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- The role of ion/neutral complexes in the fragmentation of N-benzyl-(alkylpyridinium) ions
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N-Benzylpyridinium ions bearing an alkyl group at the pyridine nucleus were studied as potential precursors of gaseous ion/neutral complexes. The occurrence of I/N complexes [C6H5CH2 + ? alkylpyridine] was probed by the reactivity of the potential benzylic hydride donor sites present in the ortho-, meta- and para-alkyl groups (R = methyl, ethyl, isopropyl and benzyl). Collision-induced dissociation of the ions, carried out in an electrical ion cage mass spectrometer, revealed that hydride transfer strongly depends both on the energy requirements of the hydride transfer but also on the position of the hydride donor. Hydride transfer, giving rise to the loss of toluene, was found to occur exclusively with those N-benzylpyridinium ions which bear an isopropyl or a benzyl substituent in the ortho position of the pyridine ring, thus reflecting the intermediacy of I/N complexes. All of the putative hydride donor alkyl groups were found to be non-reactive in the meta and para positions, as were methyl and ethyl groups even in the ortho positions. Density functional calculations (B3LYP/6-311+G/3d,2p)//(B3LYP/6-31+G(d)) on the hydride-transfer and simple-cleavage channels were carried out to help rationalizing these observations. The results suggest that the intra-complex hydride abstraction from the 3- and 4-isopropyl- and from the 3- and 4-benzylpyridine neutrals, although being thermodynamically favorable, is suppressed by substantial intra-complex rotational (or reorientation) barriers.
- Kuck, Dietmar,Grützmacher, Hans-Friedrich,Barth, Dieter,Heitkamp, Sandra,Letzel, Matthias C.
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body text
p. 159 - 166
(2012/07/13)
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- Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
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(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
- Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
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supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)
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- ETHANAMINE COMPOUNDS AND THEIR USE FOR TREATING DEPRESSION
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The present invention relates to ethanamine compounds, namely 1- (3-f luorophenyl) -2-methyl-2- (pyridine-2-yl) propan-1-amine and 2-methyl-l-phenyl-2- (pyridine-2yl) propan-1-amine, the enantiomers and salts thereof and their use for the treatment of depression.
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Page/Page column 25-27
(2010/07/09)
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- Chelate [2-(iminoethyl)pyridine N-oxide]metal complexes - Synthesis and structural comparison with their chemically related 2-(iminoethyl)pyridine- derived systems
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The N,O-chelate ligands 2-(iminoethyl)pyridine N-oxide (2a) and 2-(iminoethyl)-6-isopropylpyridine N-oxide (2b) were prepared by conventional synthetic routes, the latter involving a variant of the Reissert-Henze reaction. Treatment of 2a with FeCl2 resulted in a deoxygenation reaction of the ligand and formation of the salt (bis{2-(iminoethyl)-pyridine}FeCl] +[FeCl4]- (18a). In contrast, the reaction of 2a with PdCl2 or CoCl2 cleanly furnished the six-membered chelate [κN,O-2(iminoethyl)pyridine N-oxide]MCl2 complexes (19a, M = Pd) or (20a, M = Co), respectively, which were both characterised by X-ray diffraction. Treatment of 2b with [NiBr2 (dme)], followed by crystallisation from THF, gave the complex [κN,O-2b)NiBr2(THF)] (21b), which features a distorted trigonal-bipyramidal coordination geometry of the central metal atom. The reaction of 2a with [NiBr2(dme)] gave the structurally related complex [(κN,O-2a)NiBr2(κO-2a)] (21a). The N,O-chelate Pd complex 19a was shown to be an active catalyst for the Suzuki coupling reaction. The ligand systems 2a,b and their related 2-(iminoethyl)-pyridines 3a,b and a variety of metal complexes of ligands 3 were also prepared and characterised for comparison by X-ray diffraction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Nienkemper, Katrin,Kotov, Vasily V.,Kehr, Gerald,Erker, Gerhard,Froehlich, Roland
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p. 366 - 379
(2007/10/03)
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- Structure-activity relationships of dimethindene derivatives as new M2-selective muscarinic receptor antagonists
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A series of 2,3-disubstituted indenes, which are analogues of the widely used histamine H1 receptor antagonist dimethindene, have been synthesized and studied as muscarinic and histamine receptor antagonists. The affinities of these compounds for the five human muscarinic receptor subtypes (M1-M5) and for human histamine H1 receptors were determined in radioligand binding studies using membranes from transfected Chinese hamster ovary (CHO) cells and [3H]N-methylscopolamine ([3H]NMS). The results demonstrate that the diisopropyl analogue 19 has a similar high affinity as (S)-dimethindene at M2 receptors ((S)-dimethindene: pKi = 7.52; (-)-19: pKi = 7.37) with an improved selectivity pattern ((S)-dimethindene: M2/M1 = 6-fold, M2/M3 = 5-fold, M2/M4 = 10-fold, M2/M5 = 25-fold; (-)-19: M2/M1 = 36-fold, M2/M3 = 96-fold, M2/M4 = 42-fold, M2/M5 = 275-fold). In addition, compound (-)-19 showed 35-fold lower affinity at histamine H1 receptors (pKi = 5.61) than (S)-dimethindene (pKi = 7.16). Another interesting compound is the fluoroethyl derivative 20 (pKi/M2 = 7.49), which also exhibits a higher M2 selectivity (M2/M1 = 19-fold; M2/M3 = 22-fold; M2/M4 13-fold; M2/M5 = 62-fold) than (S)-dimethindene. Unfortunately, compound 20 also shows a high affinity for histamine H1 receptors (pKi = 8.14). The compound with the highest affinity for M2 receptors (pKi = 7.91), the dimethylaminomethylene analogue 31, displayed only a small preference for M2 receptors. In conclusion, compound (-)-19 might be useful to test the hypothesis that blockade of muscarinic M2 receptors in the brain is a viable mechanism by which to produce improved cognition. This second-generation dimethindene analogue might also be the starting point for the development of M2-selective muscarinic antagonists useful for quantifying M2 receptors in the central nervous system with positron emission tomography imaging.
- B?hme, Thomas M.,Keim, Christine,Kreutzmann, Kai,Linder, Matthias,Dingermann, Theo,Dannhardt, Gerd,Mutschler, Ernst,Lambrecht, Günter
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p. 856 - 867
(2007/10/03)
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- Process for the preparation of polychloropyrimidines
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Polychloropyrimidines, in particular 4,6-dichloropyrimidine and 2,4,6-trichloropyrimidine, are obtained in a particularly advantageous manner from polyhydroxypyrimidines or tautomeric keto compounds thereof and excess phosphorus oxychloride in the presence of a tertiary amine if, in this reaction, a) 0.75 to 1.5 mol of phosphorus trichloride and 0.7 to 1.4 mol of chlorine per equivalent of hydroxyl groups to be replaced by chlorine are added such that an excess of phosphorus trichloride over chlorine is always present and b) phosphorus oxychloride and the polychloropyrimidine prepared are distilled off successively over a column under reduced pressure, or steps a) and b) are carried out in the reverse sequence, phosphorus trichloride also being distilled off before the phosphorus oxychloride in the case of b) after a) and phosphorus oxychloride which has formed again after step a) has been carried out being distilled off in the case of a) after b), and c) a strong base is added to the distillation residue which is then present, and the tertiary amine employed is recovered from this mixture by d) separating off the upper phase and e) purifying it by distillation, or carrying out steps d) and e) in the reverse sequence.
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- A series of non-quinoline cysLT1 receptor antagonists: SAR study on pyridyl analogs of Singulair
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The structure-activity relationship of a series of styrylpyridine analogs of MK-0476 (montelukast, Singular) is described. This work has led to the identification of a number of potent and orally active cysLT1 receptor (LTD4 receptor) antagonists including 2ab (L-733,321) as an optimized candidate.
- Guay, Daniel,Gauthier,Dufresne,Jones,McAuliffe,McFarlane,Metters,Prasit,Rochette,Roy,Sawyer,Zamboni
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p. 453 - 458
(2007/10/03)
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- Entropy barriers to proton transfer
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Proton transfer between sterically hindered pyridines and amines proceeds through locked-rotor, low-entropy intermediates. The reactions exhibit slow kinetics (efficiencies of 0.1-0.0001) and large negative temperature coefficients (up to k = CT-8.7). The rates become slower and the temperature dependencies steeper with increasing steric hindrance. The observations are reproduced by a multiple complex-switching RRKM model that allows several alternative complexes to be rate controlling: a series of loose complexes, a locked-rotor tight complex that occurs before the formation of a hydrogen-bonded complex, and a complex located at the central barrier. The rate-limiting transition state shifts from the loose to the tight and central-barrier complexes with increasing temperature. The model suggests that at elevated temperatures, above 1000 K, ion-molecule reactions will become slow even for unhindered, small reactants. Ion kinetics may then become similar to neutral radical kinetics.
- Meot-Ner, Michael,Smith, Sean C.
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p. 862 - 869
(2007/10/02)
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- A Three-Step Pyridoannelation of Carbonyl Compounds
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The elaboration of a pyridine nucleus onto an α-methylene carbonyl compound can be accomplished through a three step reaction sequence based on the regiospecific alkylation of N,N-dimethylhydrazones with bromoethyl-1,3-dioxolane.Scope and limitations of the new method are considered.
- Marchetti, Mauro
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p. 1761 - 1765
(2007/10/02)
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- Alkylation of Pyridine in Free Radical Chain Reactions Utilizing Alkylmercurials
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Pyridines or N,N,N',N'-tetramethyl-p-phenylenediamine will undergo a photostimulated free radical chain reaction with alkylmercury halides or carboxylates, yielding ring alkylated substitution products.Alkene mercuration products (R1CH(Y)CH(R2)HgX with Y=HO, RO, CH3CONH; X=Cl, CH3CO2, CF3CO2) can be used without isolation for the alkylation reaction
- Russell, Glen A.,Guo, Deliang,Khanna, Rajive K.
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p. 3423 - 3425
(2007/10/02)
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- NMR Studies of Picolyl-type Carbanions. VIII. Anions Produced by Reactions of Alkyl-substituted Pyridines with Butyllithium
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The 1H and 13C NMR spectra have been observed for the anions, produced from methyl-, ethyl-, and isopropylpyridines, in tetrahydrofuran (THF).Two kinds of anions are formed concomitantly by lithium-proton exchange and addition of butyllithium from 2-ethyl, 2-isopropyl, 4-methyl, and 4-ethylpyridines.The former reaction tends to occur at the substituent bonded to the position adjacent to nitrogen, and the latter one occurs at the position adjacent to nitrogen without substituent.In the anions formed by the exchange from 2- and 4-ethylpyridines, a specific ring protonis coupled to the α-carbon, and, further, the ortho- or meta-protons (or -carbons) in the latter anion are nonequivalent respectively at room temperature.The α-carbons in these anions are virtually sp2-hybridized.
- Konishi, Kazuyori,Matsumoto, Hiroshi,Saito, Katsuhiro,Takahashi, Kensuke
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p. 2294 - 2297
(2007/10/02)
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- A Convenient Method for the Regioselective Synthesis of 4-Alkyl(aryl)pyridines Using Pyridinium Salts
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RCu.BF3 reacted with 1-ethocycarbonylpyridinium chloride at the 4-position with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridine derivatives in high yields (81-94percent).The dihydropyridines were oxidized by oxygen to give 4-alkyl(aryl)pyridines (38-68percent).Grignard reagents also reacted with 1-t-butyldimethylsilylpyridinium triflate with almost complete regioselectivity (>99percent) to afford the corresponding 1,4-dihydropyridines, which were easily oxidized to give 4-substituted pyridines in higher yields than above (58-70percent).
- Akiba, Kin-ya,Iseki, Yuji,Wada, Makoto
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p. 1994 - 1999
(2007/10/02)
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- Process for the catalytic production of 2-substituted pyridines
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A process for the catalytic production of a 2-substituted pyridine which comprises reacting a corresponding cyano compound and acetylene in the presence of cobaltocene. Favorable conversion speed, conversion of at least 90 percent, good yield and high selectivity are obtained.
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