- LIGAND COUPLING REACTION ON THE PHOSPHORUS ATOM
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Phosphine oxides bearing two or three 2-pyridyl groups were found to react with organometallic compounds affording 2,2'-bipyridyl, 2-substituted pyridines and pyridine in substantial yields.Both ligand exchange and ligand coupling appear to take place within the penta-coordinated phosphorus intermediates formed incipiently.
- Uchida, Yuzuru,Onoue, Katsumi,Tada, Nobuaki,Nagao, Fumio
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- CONVERSION OF HETEROCYCLIC N-OXIDES INTO α-ALKYLATED HETEROCYCLES. TRIMETHYLSILANOL AS LEAVING GROUP -IV.
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Aromatic heterocyclic N-oxides are readily converted into α-alkylated heterocycles by allyl-or benzyltrimethylsilane and fluoride ion.
- Vorbrueggen, Helmut,Krolikiewicz, Konrad
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- Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding
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Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3)?H] to ketones [C(sp2)=O] or esters [C(sp3)?O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine–enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD–DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.
- Guha, Somraj,Sekar, Govindasamy
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- A novel iodide-catalyzed reduction of nitroarenes and aryl ketones with H3PO2 or H3PO3: Its application to the synthesis of a potential anticancer agent
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A novel iodide-catalyzed reduction method using hypophosphorous and/or phosphorus acids was developed to reduce both diaryl ketones and nitroarenes chemoselectively in the presence of chloro and bromo substituents in high yield. This efficient and practical method has been successfully applied to a large scale production of a potential anticancer agent
- Wu, George G.,Chen, Frank X.,LaFrance, Danny,Liu, Zhijian,Greene, Scott G.,Wong, Yee-Shing,Xie, Ji
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- A novel reduction of pyridinemethanols by samarium diiodide
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An efficient synthesis of alkylpyridine derivatives by SmI2 mediated deoxygenation of pyridinemethanol derivatives is described.
- Kato, Yoshiaki,Mase, Toshiaki
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- Palladium-catalyzed coupling reactions of (ArCH2)Ti(O-i-Pr) 3 with aromatic or heteroaromatic bromides
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Three benzyltitanium compounds of (ArCH2)Ti(O-i-Pr)3 (Ar = Ph (1a), 4-MeOC6H4 (1b), 4-FC6H 4 (1c)) were prepared and used as benzyl nucleophiles for coupling reactions with aromatic or heteroaromatic bromides. The simple catalytic system of 1 mol % Pd(OAc)2 and 2 mol % PCy3 worked efficiently for a wide variety of aromatic bromides, producing diarylmethanes in good to excellent yields of up to 96%. Coupling reactions of hindered aromatic bromides or aromatic bromides containing electron-withdrawing substituents were slower over longer reaction times of 3-6 h. Reactions of heteroaromatic bromides of bromopyridines, bromofurans, or bromothiophenes with benzyl reagents of 1a or 1b required either longer reaction times of 12-24 h or a higher reaction temperature of 80 °C, producing pyridyl-, furyl-, and thienyl-arylmethanes in moderate yields.
- Chang, Shu-Ting,Li, Qinghan,Chiang, Ruei-Tang,Gau, Han-Mou
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- Palladium-catalyzed regioselective benzylation-annulation of pyridine N -oxides with toluene derivatives via multiple c-h bond activations: Benzylation versus arylation
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A palladium-catalyzed cross-dehydrogenative coupling (CDC) reaction of pyridine N-oxides with toluenes has been developed that operates under mild conditions. 2-Benzylpyridines can be obtained directly by this method via a CDC reaction between unactivated toluenes and pyridine N-oxides. In addition, azafluorene N-oxides, of value for future medicinal chemistry applications, can be obtained successfully by this procedure via four tandem C-H bond activations.
- Kianmehr, Ebrahim,Faghih, Nasser,Khan, Khalid Mohammed
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- Acylation of 2-benzylpyridine N-oxides and subsequent in situ [3,3]-sigamatropic rearrangement reaction
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An effective method for the acylation of 2-benzylpyridine N-oxides and their fast in situ [3,3]-sigmatropic rearrangement was reported. This transformation has a wide substrate scope under mild conditions, giving moderate to excellent yields. The application for the synthesis of chiral phenyl-2-pyridylmethanol products was briefly explored. Furthermore, an interesting example of tandem substitution and in situ [3,3]-sigamatropic rearrangement of 2-benzylpyridine N-oxide with benzenecarboximidoyl chloride was reported.
- Antilla, Jon C.,Jing, Hua-qing,Li, Hong-liang
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- Ligand-Free Iridium-Catalyzed Dehydrogenative ortho C?H Borylation of Benzyl-2-Pyridines at Room Temperature
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A convenient and ligand-free iridium-catalyzed dehydrogenative ortho C?H borylation of benzyl-2-pyridines has been developed. The reaction proceeds smoothly at room temperature using pinacolborane as a borylating reagent in the presence of catalytic amount of [IrOMe(COD)]2. The reaction is compatible with many functional groups, providing a vast array of ortho borylated products in moderate to excellent yields with excellent selectivities. (Figure presented.).
- Yang, Yuhuan,Gao, Qian,Xu, Senmiao
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p. 858 - 862
(2019/01/04)
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- Catalytic Selective Metal-Free Cross-Coupling of Heteroaromatic N-Oxides with Organosilanes
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A metal-free, regioselective C-H functionalization of heteroaromatic N-oxides has been developed. The method enables the synthesis of various benzylated and alkynylated N-heterocycles in a transition-metal-free manner employing organosilanes as coupling partners. The unanticipated reactivity has been exploited for the synthesis of a number of symmetrical disubstituted acetylenes from ethynyltrimethylsilane via carbon-silicon bond metathesis.
- Puthanveedu, Mahesh,Polychronidou, Vasiliki,Antonchick, Andrey P.
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supporting information
p. 3407 - 3411
(2019/05/10)
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- Nickel-catalyzed cross-coupling of aldehydes with aryl halides: Via hydrazone intermediates
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Traditional cross-couplings require stoichiometric organometallic reagents. A novel nickel-catalyzed cross-coupling reaction between aldehydes and aryl halides via hydrazone intermediates has been developed, merging the Wolff-Kishner reduction and the classical cross-coupling reactions. Aromatic aldehydes, aryl iodides and aryl bromides are especially effective in this new cross-coupling chemistry.
- Tang, Jianting,Lv, Leiyang,Dai, Xi-Jie,Li, Chen-Chen,Li, Lu,Li, Chao-Jun
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supporting information
p. 1750 - 1753
(2018/02/21)
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- Substrate switchable Suzuki-Miyaura coupling for benzyl ester: Vs. benzyl halide
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Two reaction conditions were developed to accomplish the substrate switchable Suzuki-Miyaura coupling of benzyl derivatives and arylboronic acid derivatives. Under conditions for esters, benzyl esters such as carbonates and acetates reacted with arylboronic acids to afford the corresponding diarylmethanes. However, the benzyl halides did not react under the same conditions. On the other hand, benzyl halides such as bromides and chlorides furnished diarylmethanes under conditions for halides, under which benzyl ester substrates did not react, in which water was found to play an important role. This switching system was tested using the intermolecular/intramolecular competitive reactions, during which the desired products could be synthesized by selecting the appropriate reaction conditions.
- Ohsumi, Masato,Ito, Akitaka,Nishiwaki, Nagatoshi
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p. 35056 - 35061
(2018/10/24)
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- Cobalt-Catalyzed Formation of Functionalized Diarylmethanes from Benzylmesylates and Aryl Halides
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A simple cobalt-catalyzed reductive coupling protocol allowing the synthesis of functionalized diarylmethanes from benzyl mesylate is described. The possibility to directly use the benzyl alcohol as a result of a two-step reaction is also presented. This method tolerates a variety of functional groups. A benzyl radical is likely involved. (Figure presented.).
- Reddy, Bhoomireddy Rajendra Prasad,Chowdhury, Sushobhan,Auffrant, Audrey,Gosmini, Corinne
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p. 3026 - 3029
(2018/08/24)
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- Photocatalyzed ortho-Alkylation of Pyridine N-Oxides through Alkene Cleavage
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A photocatalyzed reaction of pyridine N-oxides with alkenes gives ortho-alkylated pyridines with cleavage of the carbon–carbon double bond. Benzyl and secondary alkyl groups are incorporated at the ortho position of pyridines in one pot.
- Zhou, Wang,Miura, Tomoya,Murakami, Masahiro
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supporting information
p. 5139 - 5142
(2018/05/30)
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- Synthesis of bench-stable solid triorganoindium reagents and reactivity in palladium-catalyzed cross-coupling reactions
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Bench-stable solid triorganoindium compounds have been prepared by coordination with 4-(dimethylamino)pyridine (DMAP). The solid R3In(DMAP) complexes are obtained from the corresponding solution of R3In in quantitative yield and can
- Gil-Negrete, José M.,Pérez Sestelo, José,Sarandeses, Luis A.
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supporting information
p. 1453 - 1456
(2018/02/19)
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- Direct Synthesis of N,N-Dimethylated and β-Methyl N,N-Dimethylated amines from nitriles using methanol: Experimental and computational studies
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Direct and selective synthesis of N,N-dimethylated amines from nitriles using methanol as C1 building blocks is reported using an air- and moisture-stable ruthenium complex. Following this process, various aromatic as well as aliphatic nitriles were converted to the corresponding N-methylated amines. Interestingly, tandem C-methylation as well as N-methylation was achieved by introducing multiple methyl groups. The practical aspect of this process was revealed by preparative-scale reactions with different nitriles and the synthesis of anti-allergic drug "avil". Several kinetic experiments and detailed DFT calculations were carried out to understand the mechanism of this process.
- Paul, Bhaskar,Shee, Sujan,Panja, Dibyajyoti,Chakrabarti, Kaushik,Kundu, Sabuj
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p. 2890 - 2896
(2018/04/14)
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- A synthetic method of pheniramine maleate
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A novel synthetic method of pheniramine maleate is provided. The method includes subjecting benzylboronic acid and 2-halogenpyridine to a condensation reaction to obtain 2-benzylpyridine, subjecting the 2-benzylpyridine and 2-dimethylaminoethyl halide hydrochloride to a substitution reaction to prepare pheniramine, and salifying the pheniramine with maleic acid to obtain the pheniramine maleate. The method is simple in process, high in yield, low in cost and easy in industrial production.
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Paragraph 0009; 0010; 0051; 0052; 0054
(2018/07/06)
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- Copper-Catalyzed Base-Controlled Diastereoselective Synthesis of Tetraarylethanes from 2-Benzylpyridines
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A highly efficient and base-controlled diastereoselective synthesis of tetraarylethanes through copper-catalyzed dehydrogenative homocoupling of readily available 2-benzylpyridines is reported. Various dl - and meso -tetraarylethanes were diastereoseletively synthesized by this new protocol, where base plays the role of the principle modulator: Grignard reagents selectively provide the C2 isomers, whereas KO t -Bu promotes the formation of the meso -tetraarylethanes. Interestingly, the presence of excess KO t -Bu generates the (E)-tetraarylethenes as the only product.
- Chandrasekar, Selvaraj,Karthikeyan, Iyyanar,Sekar, Govindasamy
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p. 1275 - 1283
(2017/12/26)
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- Palladium-Catalyzed Arylation of Benzylic C-H Bonds of Azaarylmethanes with Aryl Sulfides
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Benzylic C-H arylation of azaarylmethanes with aryl sulfides has been developed by using a Pd-NHC catalyst and an amide base. Various azaarylmethanes and aryl sulfides were involved in the reaction to afford the corresponding diarylmethanes in good to excellent yields. Moreover, triarylmethane synthesis was accomplished through iterative arylations of 2- or 4-methylpyridine with two different aryl sulfides.
- Gao, Ke,Yamamoto, Keita,Nogi, Keisuke,Yorimitsu, Hideki
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supporting information
p. 2956 - 2960
(2017/10/06)
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- Efficient Selenium-Catalyzed Selective C(sp3)?H Oxidation of Benzylpyridines with Molecular Oxygen
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An efficient selenium-catalyzed direct oxidation of benzylpyridines in aqueous DMSO has been successfully developed by using molecular oxygen as the oxidant. A variety of benzoylpyridines with broad functional group tolerance were obtained in modest to excellent yields and with exclusive chemoselectivity. (Figure presented.).
- Jin, Weiwei,Zheng, Poonnapa,Wong, Wing-Tak,Law, Ga-Lai
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p. 1588 - 1593
(2017/05/05)
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- A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters
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We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron-deficient olefins via radical addition to efficiently form C?C coupled products in a redox-neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.
- Lima, Fabio,Sharma, Upendra K.,Grunenberg, Lars,Saha, Debasmita,Johannsen, Sandra,Sedelmeier, Joerg,Van der Eycken, Erik V.,Ley, Steven V.
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supporting information
p. 15136 - 15140
(2017/11/20)
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- Visible-Light-Mediated Aromatic Substitution Reactions of Cyanoarenes with 4-Alkyl-1,4-dihydropyridines through Double Carbon-Carbon Bond Cleavage
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Novel aromatic substitution reactions of cyanoarenes with 4-alkyl-1,4-dihydropyridines as alkylating reagents in the presence of a catalytic amount of a photoredox catalyst proceed smoothly to give the corresponding alkyl-substituted arenes in good to high yields. The present reaction system realizes a novel C-C bond-forming reaction between two fragments generated from the C-C bond-cleavage reactions of two independent substrates.
- Nakajima, Kazunari,Nojima, Sunao,Sakata, Ken,Nishibayashi, Yoshiaki
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p. 1028 - 1032
(2016/04/05)
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- Versatile C(sp2)?C(sp3) Ligand Couplings of Sulfoxides for the Enantioselective Synthesis of Diarylalkanes
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The reaction of chiral (hetero)aryl benzyl sulfoxides with Grignard reagents affords enantiomerically pure diarylalkanes in up to 98 % yield and greater than 99.5 % enantiomeric excess. This ligand coupling reaction is tolerant to multiple substitution patterns and provides access to diverse areas of chemical space in three operationally simple steps from commercially available reagents. This strategy provides orthogonal access to electron-deficient heteroaromatic compounds, which are traditionally synthesized by transition metal catalyzed cross-couplings, and circumvents common issues associated with proto-demetalation and β-hydride elimination.
- Dean, William M.,?iau?iulis, Mindaugas,Storr, Thomas E.,Lewis, William,Stockman, Robert A.
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p. 10013 - 10016
(2016/08/16)
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- Ruthenium-Mediated Dual Catalytic Reactions of Isoquinoline via C?H Activation and Dearomatization for Isoquinolone
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We have unraveled the ruthenium-promoted prototype reaction based on C(sp2)?C(sp3) bond formation through the reigoselective C?H activation of isoquinoline and pyridine derivatives with various alkyl halides, leading to 1-substituted isoquinoline products in good yield. This C?H catalytic reaction did not rely on chelation assistance of the directing group of the substrates. The dimer [RuCl2(p-cymene)]2in combination with an N-heterocyclic carbene ligand, adamantanecarboxylic acid and K2CO3base in N-methyl-2-pyrrolidone solution at 150 °C are the best conditions. Simultaneously, we are also able to chemically tune the reaction mode to dearomatization by adding water, leading to isoquinolone products. This reaction methodology is not suitable for other nitrogen-containing heteroarenes such as pyridazines and pyrimidines. (Figure presented.).
- Wang, Ting-Hsuan,Lee, Wei-Chih,Ong, Tiow-Gan
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supporting information
p. 2751 - 2758
(2016/09/13)
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- Cobalt-Catalyzed Reductive Cross-Coupling Between Benzyl Chlorides and Aryl Halides
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A new protocol for the direct reductive cobalt-catalyzed arylation of benzyl chlorides has been developed in order to form functionalized diarylmethanes. A variety of reactive groups either on the aryl or the benzyl halide was employed. This represents the first cobalt-catalyzed reductive cross-coupling which does not require any ligand and pyridine. A reaction pathway is proposed involving a radical benzyl species. (Figure presented.).
- Pal, Suman,Chowdhury, Sushobhan,Rozwadowski, Elodie,Auffrant, Audrey,Gosmini, Corinne
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supporting information
p. 2431 - 2435
(2016/08/16)
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- PBr3-mediated unexpected reductive deoxygenation of α-aryl-pyridinemethanols: Synthesis of arylmethylpyridines
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PBr3-mediated reductive deoxygenation of α-aryl-pyridinemethanols to provide arylmethylpyridines is described, the alcohol substrate scope is explored, free radical trap TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) is introduced, and the hydrogen source of the methylene product is defined. The unexpected reaction enabled us to prepare previously inaccessible, novel EP1 antagonists.
- Nishigaya, Yosuke,Umei, Kentaro,Watanabe, Daisuke,Kohno, Yasushi,Seto, Shigeki
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p. 1566 - 1572
(2016/03/01)
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- Alternative approach toward the generation of benzylic zinc reagent: Direct oxidative addition of active zinc into the carbon-oxygen bond of benzyl mesylates
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The use of highly active zinc, prepared by the Rieke method, for the direct preparation of benzylic zinc mesylate was investigated. The oxidative addition of highly active zinc to benzyl mesylate was easily completed under mild conditions. The resulting benzylic zinc mesylates were employed in subsequent cross-coupling reactions with a broad range of electrophiles, and the formation of the corresponding products was successful.
- Jung, Hye-Soo,Kim, Seung-Hoi
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p. 666 - 670
(2015/03/14)
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- Triazolopyridines. Part 30.1 Hydrogen transfer reactions; Pyridylcarbene formation
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The transfer hydrogenation reaction of [1,2,3]triazolo[1,5-a]pyridines with Pd/C/Zn or Pd(OH)2/C/Zn in water, ethanol or water/ethanol mixture has been explored. 4,5,6,7-Tetrahydrotriazolopyridines were obtained in good to medium yields. In addition, under the same conditions 2-substituted pyridines were also formed as a result of intermediate pyridylcarbene formation, by triazole ring opening and loss of nitrogen.
- Abarca, Belen,Adam, Rosa,Alom, Shamim,Ballesteros, Rafael,Lopez-Molina, Sonia
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p. 175 - 186
(2014/03/21)
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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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- Nickel-catalyzed cross-coupling of aryl fluorides and organozinc reagents
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Ni(PCy3)2Cl2 was demonstrated to effectively catalyze cross-coupling of aryl fluorides and organozinc reagents. Both electron-poor and -rich aryl fluorides can react effectively with nucleophiles including aryl-, methyl-, and benzylzinc chlorides. A wide range of substituents and functional groups are tolerated. In the presence of a directing group, PhC(O), the reaction is selective for cleavage of the C-F bond ortho to the carbonyl substituent in a difluoroarene.
- Zhu, Feng,Wang, Zhong-Xia
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p. 4285 - 4292
(2014/06/09)
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- Synthesis of heteroaryl compounds through cross-coupling reaction of aryl bromides or benzyl halides with thienyl and pyridyl aluminum reagents
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An efficient method for synthesis of useful biaryl building blocks containing 2-thienyl, 3-thienyl, 2-pyridyl, and 3-pyridyl moieties was provided through cross-coupling reactions of aryl bromides or benzyl halides with heteroaryl aluminum reagents in the presence of Pd(OAc)2 and (o-tolyl)3P. The coupling reaction also worked efficiently with heteroaryl bromides affording series of heterobiaryl compounds. The reaction of phenylbromide with in situ prepared 3-pyridyl aluminum was demonstrated to afford the product 8a in high yield. Additionally, the catalytic system was also suited well for the coupling reaction of benzyl halides with pyridyl aluminum reagents to afford series of pyridyl-arylmethane.
- Chen, Xu,Zhou, Lingmin,Li, Yimei,Xie, Tao,Zhou, Shuangliu
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p. 230 - 239
(2014/01/17)
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- Direct vicinal disubstitution of diaryliodonium salts by pyridine N-oxides and N-amidates by a 1,3-radical rearrangement
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Paired off: The title reaction leads to a series of o-pyridinium phenols (1) and anilines (2). The experimental and computational studies indicate that the key step involves homolytic cleavage to give a radical pair, which undergoes solvent-cage recombination to give the product. Copyright
- Peng, Jing,Chen, Chao,Wang, Yong,Lou, Zhenbang,Li, Ming,Xi, Chanjuan,Chen, Hui
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supporting information
p. 7574 - 7578
(2013/07/26)
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- NOVEL MICROBICIDES
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Compounds of formula (I), wherein G represents together with the two carbon atoms of the pyrimidine ring to which it is attached, a 5- to 7-membered aliphatic carbocyclic or heterocyclic ring system which contain 0 to 2 heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur; and wherein said 5- to 7-membered aliphatic carbocyclic or heterocyclic ring system can be mono-, di- or trisubstituted by substituents selected from the group consisting of halogen, keto, C1-C6alkyl, C1-C6alkoxy, C1-C6alkyloximino and C1-C6alkylendioxy; and wherein the other substituents R1, R2, R3, R4, R5 and R6 are as defined in claim 1, and their use as microbicides.
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Page/Page column 49-50
(2012/05/19)
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- Palladium-catalyzed benzylic cross-couplings of pyridine N-oxides
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Palladium-catalyzed C-H couplings (CSP3-C SP2) of pyridine N-oxides with benzyl chloride derivatives is reported. It provides a novel and easy process for the synthesis of 2-benzylpyridine derivatives through benzylic cross-couplings of pyridine N-oxides. Georg Thieme Verlag Stuttgart · New York.
- Mai, Wenpeng,Yuan, Jinwei,Li, Zhicheng,Yang, Liangru,Xiao, Yongmei,Mao, Pu,Qu, Lingbo
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supporting information; experimental part
p. 938 - 942
(2012/06/01)
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- Palladium-catalyzed decarboxylative couplings of 2-(2-Azaaryl)acetates with aryl halides and triflates
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Pd-catalyzed decarboxylative cross-couplings of 2-(2-azaaryl)acetates with aryl halides and triflates have been discovered. This reaction is potentially useful for the synthesis of some functionalized pyridines, quinolines, pyrazines, benzoxazoles, and benzothiazoles. Theoretical analysis shows that the nitrogen atom at the 2-position of the heteroaromatics directly coordinates to Pd(II) in the decarboxylation transition state.
- Shang, Rui,Yang, Zhi-Wei,Wang, Yan,Zhang, Song-Lin,Liu, Lei
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supporting information; experimental part
p. 14391 - 14393
(2010/12/19)
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- Synthesis of pyridines and pyrazines using an intramolecular hydroamination-based reaction sequence
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A management issue! Various pyridines and pyrazines can be efficiently accessed from simple acyclic precursors using an intramolecular hydroamination/isomerization/aromatization sequence (see scheme). ρ-Toluenesulfonic acid (2 mol%) is used to catalyze this novel alkyne annulation, in which the oxime group allows for a subsequent redoxneutral aromatization step to occur.
- Rizk, Toni,Bilodeau, Eric J.-F.,Beauchemin, Andre M.
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supporting information; experimental part
p. 8325 - 8327
(2010/01/16)
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- Synthesis of phenanthro[9,10-b]indolizidin-9-ones, phenanthro[9,10-b] quinolizidin-9-one, and related benzolactams by Pd(OAc)2-catalyzed direct aromatic carbonylation
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Phenanthro[9,10-b]indolizidin-9-ones, phenanthro[9,10-b]-quinolizidin-9- one, and related benzolactams were synthesized by benzolactam ring formation using Pd(OAc)2-catalyzed direct aromatic carbonylation. This also constitutes a formal synthesis of the representative phenanthroindolizidine and -quinolizidine alkaloids (±)-tylophorine, (±)-antofine, and (±)-cryptopleurine. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Yamashita, Satoshi,Kurono, Nobuhito,Senboku, Hisanori,Tokuda, Masao,Orito, Kazuhiko
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supporting information; experimental part
p. 1173 - 1180
(2009/07/11)
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- Synthesis of 2-substituted pyridines via a regiospecific alkylation, alkynylation, and arylation of pyridine N-oxides
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Figure presented Sequential addition of Grignard reagents to pyridine N-oxides in THF at room temperature followed by treatment with acetic anhydride at 120°C afforded 2-substituted pyridines in good to high yields. Furthermore, by exchanging acetic anhydride for DMF in the second step, 2-substituted pyridine N-oxides were obtained, as intermediates suitable for addition of a second Grignard reagent for the synthesis of 2,6-disubstituted pyridines.
- Andersson, Hans,Almqvist, Fredrik,Olsson, Roger
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p. 1335 - 1337
(2008/01/03)
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- Palladium-catalyzed 2-pyridylmethyl transfer from 2-(2-pyridyl)-ethanol derivatives to organic halides by chelation-assisted cleavage of unstrained Csp3-Csp3 bonds
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(Chemical Equation Presented) Making a break for it: Treatment of 2-(2-pyridyl)ethanol derivatives with aryl chlorides in the presence of a palladium catalyst results in the transfer of the pyridylmethyl moiety of the alcohol to yield the corresponding (2-pyridyl-methyl)arene. The reaction proceeds by chelation-assisted cleavage of an Csp3-C5p3 bond (see scheme) followed by formation of a carbon-carbon bond.
- Niwa, Takashi,Yorimitsu, Hideki,Oshima, Koichiro
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p. 2643 - 2645
(2008/02/13)
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- Palladium-catalyzed cross-coupling of B-Benzyl-9-borabicyclo[3.3.1]nonane to furnish methylene-linked biaryls
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(Chemical Equation Presented) Benzylboranes are noticeably uncommon partners within Suzuki-Miyaura coupling reactions. B-Benzyl-9-BBN was successfully coupled to a range of aryl/heteroaryl bromides, chlorides, and triflates to give pharmacologically important methylene-linked biaryl structures. Activated, deactivated, and sterically hindered substrates were successfully coupled in high yield using Pd(PPh3)4 or Pd(OAc)2 with SPhos as the catalyst system.
- Flaherty, Alice,Trunkfield, Amy,Barton, William
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p. 4975 - 4978
(2007/10/03)
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- Cobalt-catalyzed cross-coupling reaction of chloropyridines with grignard reagents
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Treatment of 2-chloropyridine with benzylmagnesium chloride in the presence of a catalytic amount of cobalt(II) acetylacetonate in dioxane afforded the corresponding cross-coupling product in excellent yield. Trimethylsilylmethyl and phenyl Grignard reagents also participated in similar cross-coupling reactions.
- Ohmiya, Hirohisa,Yorimitsu, Hideki,Oshima, Koichiro
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p. 1240 - 1241
(2007/10/03)
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- Palladium-catalyzed cross-coupling of benzylzinc reagents with methylthio N-heterocycles: A new coupling reaction with unusual selectivity
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Benzylzinc reagents undergo palladium-catalyzed cross-coupling reactions with methylthio-substituted N-heterocycles in moderate to good yields. 2- (Methylthio)pyrimidines are particularly reactive substrates for this reaction. As a result, the regioselectivity of 2,4-bis(methylthio)pyrimidines is opposite to that of their 2,4-dichloropyrimidine analogues. This unusual cross-coupling reaction offers new flexibility in the regioselective synthesis of substituted pyrimidines and other heterocycles.
- Angiolelli, Mary E.,Casalnuovo, Albert L.,Selby, Thomas P.
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p. 905 - 907
(2007/10/03)
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- 1,4-Bis(arylsulfonyl)-1,2,3,4-tetrahydropyridines in synthesis. Highly regio- and stereoselective SN1′ and alkylation reactions
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Reaction of lithiated β-sulfonyl acetals with amino acid-derived N-tosylaziridines followed by acid-catalysed cyclisation gives enantiomerically pure 2-alkyl 1,4-bis(arylsulfonyl)-1,2,3,4-tetrahydropyridines 3 in good yields. These heterocyclic substrates react efficiently and highly stereoselectively with a range of carbon nucleophiles under Lewis acidic conditions to give the 1,2,5,6-tetrahydropyridine products of SN1′ reaction, and undergo lithiation followed by completely stereoselective reaction at the 4-position with haloalkanes.
- Craig, Donald,McCague, Raymond,Potter, Gerard A.,Williams, Meredith R. V.
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- Aggregative activation in heterocyclic chemistry. Part 5. Lithiation of pyridine and quinoline with the complex base BuLi·Me2N(CH2)2OLi (BuLi·LiDMAE)
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It is shown that the complex base BuLi·LiDMAE reacts with pyridine to give metallated species which, after trapping by electrophiles, lead to 2-substituted pyridines in good to excellent yields. The same reactions have been less successfully performed with quinoline.
- Gros, Philippe,Fort, Yves,Caubere, Paul
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p. 3597 - 3600
(2007/10/03)
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- Synthesis of 1,4-dihydropyridines by regioselective additions of benzylic zinc bromides to pyridinium salts and their aromatizations to 4-benzylpyridines
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Benzylic zinc reagents add with high regioselectivity to 1-(phenoxycarbonyl) salts of methyl nicotinate to yield methyl-1-(phenoxycarbonyl)-4-benzyl-1,4-dihydronicotinates. The dihydronicotinates on heating with sulfur in decalin afford methyl 4-benzylnicotinates.
- Krapcho, A. Paul,Waterhouse, David J.,Hammach, Abdelhakim,Di Domenico, Roberto,Menta, Ernesto,Oliva, Ambrogio,Spinelli, Silvano
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p. 781 - 794
(2007/10/03)
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- Ligand coupling reactions of 2-pyridyl, 4-pyridyl and 2-pyrimidyl sulfoxides with grignard reagents
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The ligand coupling reaction was extended to 3-and 4-pyridyl sulfoxides as well as the 2-pyrimidyl moiety with Grignard reagents. It was found that both 4-pyridyl and 2-pyrimidyl sulfoxides nicely underwent the ligand coupling reactions, but 3-pyridyl sulfoxide underwent ligand exchange.
- Oae, Shigeru,Takeda, Takeshi,Uenishi, Junichi,Wakabayashi, Shoji
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p. 179 - 182
(2007/10/03)
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- First Cobalt(I)-catalysed Heterocyclotrimerization of Ethyne with Nitriles to Pyridines in Water under Mild Conditions
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In water the synthesis of substituted pyridines with cobalt(I)-complexes is carried out at room temperature and normal pressure with very high product selectivity in the presence of light.
- Heller, Barbara,Oehme, Guenther
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p. 179 - 180
(2007/10/02)
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- SYNTHESIS OF 2- AND 4-BENZYLPYRIDINES - REAGENTS FOR DETECTION OF TOXIC CHEMICALS
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Synthesis and isolation of 2- and 4-benzylpyridines, which are used in thin-layer chromatography for detection of toxic chemicals in the environment, have been described.Synthesis of 2- and 4-benzylpyridines is based on homolytic benzylation of pyridine with toluene in the presence of trifluoroacetic acid.
- Ivanova, L. P.,Kasatkina, A. A.,Trifonova, V. N.
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p. 1981 - 1982
(2007/10/02)
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- Synthetic and mechanistic investigation of the rearrangement of η2-iminoacyl ligands of group 4 metals to vinylamido groups via a facile 1,2-hydrogen shift
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Reaction of the metallocene dichloride compounds Cp2MCl2 (M = Zr, Hf) with (2-(6-methylpyridyl)-methyl)lithium (LiCH2-py-6Me) leads to the bis(alkyl) compounds Cp2M(CH2-py-6Me)2 (M = Zr (1a), Hf (1b)). A single-crystal X-ray diffraction analysis of 1a shows the compound to contain one chelated and one terminal pyridylmethyl ligand in the solid state. Solution studies with 1H and 13C NMR spectroscopy indicate equivalent pyridylmethyl ligands for 1, presumably due to rapid dissociation and recoordination of the pyridine nitrogen atoms. Treatment of compounds 1 with 2,6-dimethylphenyl isocyanide (xyNC) leads initially to the formation of the corresponding η2-iminoacyl derivatives Cp2M(η2-xyNCCH2-py-6Me)(CH 2-py-6Me) (M = Zr (2a), Hf (2b)). The η2 binding of the iminoacyl group is strongly implied by the downfield shift of the iminoacyl carbon atom in the 13C NMR spectrum: δ 246.7 ppm for 2a and δ 254.4 ppm for 2b. The iminoacyl compounds 1 exhibit thermal instability in solution. Over a period of hours at 25-30°C they rearrange via a 1,2-hydrogen shift to the corresponding vinylamido compounds Cp2M[xyNCH=CH-py-6Me](CH2-py-6Me) (M = Zr (3a), Hf (3b)) in almost quantitative yield. Further reaction of 3 with xyNC finally leads to the bis (vinylamido) compounds Cp2M[xyNCH=CH-py-6Me]2 (5) via the corresponding intermediate η2-iminoacyl 4. On the basis of 1H NMR data and a single-crystal X-ray diffraction analysis of 5b, a trans arrangement can be assigned for the hydrogen atoms attached to the vinyl group. Treatment of Cp2HfCl2 with 1 equiy of LiCH2-py-6Me or Cp2Hf(CH2-py-6Me)2 1b leads to the formation of Cp2Hf(CH2-py-6Me)Cl (6). Again treatment of 6 with xyNC generates the intermediate η2-iminoacyl compound Cp2Hf(η2-XyNCCH2-py-6Me)Cl (7), which isomerizes to the corresponding vinylamido compound 8. A kinetic study of the conversion of 2a,b to 3a,b and 7 to 8 shows the reactions to be first order in η2-iminoacyl at 28°C and the 1,2-hydrogen shifts to proceed at essentially the same rate, demonstrating little dependence on metal and ancillary ligation. The use of the deuterated reagent LiCD2-py-6CD3 allows the formation of Cp2Hf(η2-xyNCCD2-py-6CD3)Cl 7. The isomerization of 7 to 8 proceeds at a much slower rate than for the protio compound, yielding kH/kD = 11 (2) at 28°C. The introduction of a phenyl substituent onto the α-carbon of the alkyl ligand totally inhibits the 1,2-hydrogen shift. Hence, the compound Cp2Hf[CH(Ph)-py]Cl (9) reacts with xyNC to yield the stable, structurally characterized η2-iminoacyl Cp2Hf[xyNCCH(Ph)-py]Cl (10). These results combined with the thermal stability of the corresponding benzyl-derived η2-iminoacyl compounds are discussed in terms of possible mechanisms for the overall 1,2-hydrogen shift. Crystal data at 22°C for Cp2Zr(CH2-py-6Me)2 (1a): a = 7.679 (3) A?, b = 11.239 (3) A?, c = 12.672 (2) A?, α = 95.67 (2)°, β = 100.57 (2)° γ = 68.37 (3)°, Z = 2, dcalcd = 1.432 g cm-3 in space group P1 Crystal data for Cp2Hf(xyNCH=CH-py-6Me)2 (5b) at -155°C: a = 14.490 (7) A?, b = 8.925 (4) A?, c = 15.943 (9) A?, β = 91.03 (3)°, Z = 2, dcalcd = 1.263 g cm-3 in space group I2. Crystal data for Cp2Hf[η2-xyNCCH(Ph)-py]Cl (10) at 22°C: a = 11.012 (1) A?, b = 14.821 (1) A?, c = 19.067 (2) A?, β = 103.263 (8)°, Z = 4, dcalcd = 1.613 g cm-3 in space group P21/n. In the solid-state structure of 10 the phenyl and pyridyl groups were disordered.
- Beshouri, Sharon M.,Chebi, Diego E.,Fanwick, Phillip E.,Rothwell, Ian P.,Huffman, John C.
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p. 2375 - 2385
(2008/10/08)
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- LIGAND COUPLING THROUGH ?-SULFURANE --- COMPLETE RETENTION OF GEOMETRIC CONFIGURATION OF ALLYLIC AND VINYLIC GROUPS IN THE REACTIONS OF ALLYLIC AND VINYLIC SULFOXIDES WITH GRIGNARD REAGENTS
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The reaction of p-benzenesulfonylphenyl crotyl sulfoxide with Grignard reagents is considered to proceed via formation of an incipient ?-sulfurane to afford the coupling product, p-benzenesulfonyl-crotylbenzene, in which the geometric configuration of crotyl group was completely preserved.No rearrangement was observed in the coupling reaction of p-benzenesulfonylphenyl α-methylallyl sulfoxide.Such a complete retention of geometric configuration was also found in the reactions of 2-pyridyl and p-benzenesulfonylphenyl styryl sulfoxides with Grignard reagents.
- Oae, Shigeru,Takeda, Takashi,Wakabayashi, Shoji
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p. 4445 - 4448
(2007/10/02)
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