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Comparative studies on the concerted and two-step mechanism of ketene-methylenimine cycloaddition

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Chinese Journal of Chemistry 1996年第2期14卷 97-104页

作者： Fang, DC Fu, XY BEIJING NORMAL UNIV DEPT CHEMBEIJING 100875PEOPLES R CHINA

The concerted reaction mechansim of the ketene-methylenimine cycloaddition reaction was reconfirmed by IRC calculation at HF/6-31G* level. Other possible reaction schemes were also studied. The cis and gauch intermediate cannot be found on the potential energy surface, and the trans intermediate can only lead to a 6-membered ring product. Therefore, a two step mechanism to form p-lactam is excluded for the title reaction.

关键词： ketene methylenimine cycloaddition mechanism

Theoretical Study on the Reaction Mechanism of ketene CH2CO with Isocyanate NCO Radical

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Chinese Journal of Chemistry 2007年第8期25卷 1105-1111页

作者：赵丽薇阚伟于海涛付宏刚孙家钟 School of Chemistry and Materials Science Heilongjiang University Harbin Heilongjiang 150080 China School of Chemistry and Chemical Engineering Qiqihar University Qiqihar Heilongjiang 161006 China State Key Laboratory of Theoretical and Computational Chemistry Institute of Theoretical Chemistry Jilin University Changchun Jinlin 130023 China

The bimolecular single collision reaction potential energy surface of an isocyanate NCO radical with a ketene CH2CO molecule was investigated by means of B3LYP and QCISD（T） methods. The computed results indicate that two possible reaction channels exist on the surface. One is an addition-elimination reaction process, in which the CH2CO molecule is attacked by the nitrogen atom at its methylene carbon atom to lead to the formation of the intermediate OCNCH2CO followed by a C-C rupture channel to the products CH2NCO＋CO. The other is a direct hydrogen abstraction channel from CHzCO by the NCO radical to afford the products HCCO＋HNCO. Because of a higher barrier in the hydrogen abstraction reaction than in the addition-elimination reaction, the direct hydrogen abstraction pathway can only be considered as a secondary reaction channel in the reaction kinetics of NCO＋ CH2CO. The predicted results are in good agreement with previous experimental and theoretical investigations.

关键词： ketene isocyanate NCO radical quantum chemistry method reaction mechanism

Redox-neutral C–H acylation of indole with ketene by manganese catalysis

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Green Synthesis and Catalysis 2022年第3期3卷 287-290页

作者： Chengming Wang Qijing Zhang College of Chemistry and Materials Science Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and ApplicationsJinan UniversityGuangzhou 510632China

A low-cost manganese-catalyzed oxidant-free selective C–H acylation of indole with ketene is *** protocol features mild reaction conditions and good functional group *** yield is from middle to *** acylation products can be further converted to diverse useful *** study reveals the acylation transformation possibly undergoes a cyclomanganated complex species as reactive intermediate.

关键词： Manganese Indole Acylation ketene Redox-neutral

STUDIES　ON　THE　REACTIVITY　OF　CYCLOAROMATIZATION　REACTION　VIA　a－OXO　ketene　DITHIOACETALS

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Chinese Chemical Letters 1994年第7期5卷 577-580页

作者： Qun LIU Zhi Ling WANG Shu Jia ZHANG Zhi Yun YANG(Department of Chemistry, Northeast Normal University, Changchun, 130024)

The dihydric dithioketenes 3a-c obtained by 1,2-addition of methallyl Grignard reagent to bis(alkylthio)methylidene derivative ofdimedone 2a-c wewr converted to the cycloaromatization product 4 assisted by boron trifluoride *** this reaction was performed in methanol,the substitution-cycloaroatization product 5 was obtained as by- product from *** this eycloaromatization reaction,,the reactivity order dimethylthio>1, 3 - propylenedithio>1, 2- ethylenedithio carbon cation was established by the yields from 3a-c *** intramolecular a1,a1reaction pattern was developed by experiment.

关键词： OXO ketene REACTION CYCLOAROMATIZATION DITHIOACETALS VIA

Theoretical studies on selectivities in the Staudinger reaction of vicinal diimines and ketenes

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Science China Chemistry 2013年第3期56卷 370-439页

作者： HOU ShiLi LI XinYao XU JiaXi State Key Laboratory of Chemical Resource Engineering Department of Organic ChemistryFaculty of ScienceBeijing University of Chemical Technology

The selectivities,including peri-,regio-,and diastereoselectivities,in the Staudinger reaction involving vicinal diimines and ketenes were investigated theoretically via the density functional theory(DFT) *** results indicate that vicinal diimines prefer stepwise [2+2] cycloaddition rather than [2+4] cycloaddition to generate cis-4-imino-β-*** diimines attack the less sterically hindered exo-side of ketenes to generate zwitterionic intermediates,which directly undergo a conrotatory ring closure to produce cis-4-imino-β-lactams whatever diimines with less or more bulky *** unsymmetric vicinal ketoaldehyde-derived diimines,their ketimines attack the exo-side of ketenes and undergo a conrotatory ring closure to produce cis-4-aldimino-β-lactams due to less steric *** current theoretical studies provide very important information for in-depth understanding of the selective formation of mono-cis-β-lactams from vicinal diimines and ketenes.

关键词： density functional theory(DFT) selectivity diimine ketene cycloaddition Staudinger reaction

Theoretical studies on selectivities in the Staudinger reaction of vicinal diimines and ketenes

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Science China(Physics,Mechanics & Astronomy) 2013年第3期56卷 370-379页

The selectivities, including peri-, regio-, and diastereoselectivities, in the Staudinger reaction involving vicinal diimines and ketenes were investigated theoretically via the density functional theory （DFT） calculation. The results indicate that vicinal diimines prefer stepwise [2＋2] cycloaddition rather than [2＋4] cycloaddition to generate cis-4-imino-β-lactams. The diimines attack the less sterically hindered exo-side of ketenes to generate zwitterionic intermediates, which directly undergo a conrota- tory ring closure to produce cis-4-imino-β-lactams whatever diimines with less or more bulky N-substituents. For unsymmetric vicinal ketoaldehyde-derived diimines, their ketimines attack the exo-side of ketenes and undergo a conrotatory ring closure to produce cis-4-aldimino-β-lactams due to less steric effect. The current theoretical studies provide very important information for in-depth understanding of the selective formation of mono-cis-β-lactams from vicinal diimines and ketenes.

关键词： density functional theory (DFT) selectivity diimine ketene cycloaddition Staudinger reaction

Asymmetric Trapping of Pd-Containing Dipoles by Photogenerated ketenes

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Asymmetric Trapping of Pd-Containing Dipoles by Photogenerat...

Enantioselective Trapping of Pd-Containing 1,5-Dipoles by Photogenerated ketenes: Access to 7-Membered Lactones Bearing Chiral Quaternary Stereocenters

中国化学会·第十六届全国有机合成化学学术研讨会

作者：陆良秋 Yi Wei Miao-Miao Li Jie Liu Wen-Jing Xiao 华中师范大学 College of Chemistry Central China Normal University

Transition metal-catalyzed cycloaddition reactions have been determined to be a powerful tool for constructing valuable heterocyclic *** particular,a variety of dipolar cycloidditions of in situ generated,transition metal-containing dipolar species have been established by reacting with a series prepared *** the past years,we are focused on the development of Pd-,Ir-,Fe-and Cu-catalyzed novel dipolar cycloadditions by exploiting new reactivity,new reagent and new ligand. Recently,we successfully expanded the concept of TM-containing dipoles to the asymmetric photochemical cycloaddition reactions. As depicted in Scheme 1,the key to success is the enantioselective trapping of Pd-containing intermediates by ketenes,a class of reactive C2-synthons,which were generated in an in-situ and traceless manner under visible light *** this trapping,a variety of chiral heterocycles bearing challenging chiral quaternary stereocenters can be accessed in a facile manner with good efficiency and high enantio selectivity.

关键词： asymmetric catalysis palladium catalysis dipolar cycloaddition ketene chiral heterocycle

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Enantioselective Trapping of Pd-Containing 1,5-Dipoles by Ph...

Insertion Reactions of PhEtCCO and PhNCO into Ln-S (Ln=Er, Y, Yb) Bond of [Cp_2Ln(μ-SEt)]_2

中国化学会第十六届全国光化学学术讨论会（2019）

作者： Liang-Qiu Lu Yi Wei Song Liu Miao-Miao Li Yi Li Yu Lan Wen-Jing Xiao College of Chemistry Central China Normal University School of Chemistry and Chemical Engineering Chongqing University

Catalytic asymmetric construction of medium-sized rings remains an important and challenging task in organic synthesis. Within this realm, transition metal-catalyzed [5+2] cycloadditions are an elegant strategy for accessing 7-membered rings;however, successful examples have largely been limited to intramolecular Ru-or Rh-catalyzed processes using chiral feedstock. Thus, the development of a general strategy for asymmetric intermolecular [5+2] cycloadditions using a catalytic amount of chiral pool is of great interest. Otherwise, ketenes are reactive and versatile C2 synthons that are widely used in organocatalytic or Lewis acid-catalyzed asymmetric [n+2] cycloadditions(n = 2-4). However, ketenes have never been applied in the preparation of chiral medium-sized rings. In this work, we described the first example of an enantioselective [5+2] cycloaddition of vinylethylene carbonates and α-diazoketones by combining photoactivation and asymmetric Pd catalysis. The key to the success of this method is the enantioselective trapping of the Pd-containing 1,5-dipolar intermediates by reactive ketenes that were generated in an in situ and traceless manner under visible light irradiation. By doing so, a variety of 7-membered lactones bearing challenging chiral quaternary stereocenters were furnished in a facile manner with good efficiency and high enantioselectivity(up to 99% yield and 96:4 er).

关键词： asymmetric Pd catalysis Wolff rearrangement cycloaddition medium-sized ring ketene

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Journal of Rare Earths 2006年第1期24卷 9-14页

作者：张春梅林阳辉陈珍霞周锡庚 Department of Chemistry Fudan University Shanghai 200433 China Department of Chemistry East China University of Science and Technology Shanghai 200237 China) Department of Chemistry Fudan University Shanghai 200433 China

The reactivity of lanthanocene thiolates [Cp2Ln（μ-SEt）]2（Ln = Er, Y, Yb） with PhEtCCO and with PhNCO was examined. Treatment of [ Cp2Ln（μ-SEt）]2 with PhEtCCO gives the α-thiolate-substituted enolate complexes [ Cp2Ln （μ-η^1 ：η^3-OC（SEt）CPhEt）]2（Ln = Yb, Y）, while [Cp2Ln（μ-SEt）]2 react with PhNCO to give the lanthanocene amido derivatives [Cp2Ln（OC（SEt）NPh ）]2（Ln = Er, Yb）. In both cases, the insertion reaction is independent of the stoichiometric ratio and the nature of lanthanides, demonstrating that lanthanocene thiolates are high reactive toward PhEtCCO and PhNCO under the conditions involved. All complexes are characterized by elemental analysis and spectroscopic properties, of which the structures of ytterbium enolate and erbium amido are also determined by X-ray single crystal diffraction analysis, indicating that both of them are centrosymmetric binuclear structures.

关键词： organolanthanide ketene isocyanate insertion crystal structure