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1.
Salicylato Titanocene Complexes as Cooperative Organometallic Lewis Acid and Brønsted Acid Catalysts for Three‐Component Mannich Reactions 下载免费PDF全文
Dr. Ya Wu Chun Chen Gai Jia Xuyang Zhu Dr. Huaming Sun Prof. Guofang Zhang Prof. Weiqiang Zhang Prof. Ziwei Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8530-8535
A binary acid system has been developed that features an air‐stable organometallic precursor, titanocene dichloride, and simple organic cooperative Brønsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including 1H NMR titration, X‐ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system. 相似文献
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Copper‐Catalyzed Aerobic Oxidative Inert CC and CN Bond Cleavage: A New Strategy for the Synthesis of Tertiary Amides 下载免费PDF全文
Xiuling Chen Dr. Tieqiao Chen Qiang Li Dr. Yongbo Zhou Prof. Li‐Biao Han Prof. Shuang‐Feng Yin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12234-12238
A copper‐catalyzed aerobic oxidative amidation reaction of inert C?C bonds with tertiary amines has been developed for the synthesis of tertiary amides, which are significant units in many natural products, pharmaceuticals, and fine chemicals. This method combines C?C bond activation, C?N bond cleavage, and C?H bond oxygenation in a one‐pot protocol, using molecular oxygen as the sole oxidant without any additional ligands. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(39):11993-11997
The first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor‐acceptor cyclopropanes is presented. It is demonstrated that by applying an optically active bifunctional Brønsted base catalyst, racemic di‐cyano cyclopropylketones can be activated to undergo a stereoselective 1,3‐dipolar reaction with mono‐ and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with three consecutive stereocenters in high yield and stereoselectivity. Based on the stereochemical outcome, a mechanism in which the organocatalyst activates both the donor‐acceptor cyclopropane and nitroolefin is proposed. Finally, chemoselective transformations of the cycloaddition products are demonstrated. 相似文献
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Cationic Cobalt(III)‐Catalyzed Aryl and Alkenyl CH Amidation: A Mild Protocol for the Modification of Purine Derivatives 下载免费PDF全文
Yujie Liang Yu‐Feng Liang Conghui Tang Yizhi Yuan Prof. Dr. Ning Jiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16395-16399
A cationic cobalt(III)‐catalyzed direct C?H amidation of unactivated (hetero)arenes and alkenes by using 1,4,2‐dioxazol‐5‐ones as the amidating reagent has been developed. This transformation proceeds efficiently under external oxidant‐free conditions with a broad substrate scope. Moreover, 6‐arylpurine compounds, which often exhibit high potency in antimycobacterial, cytostatic, and anti‐HCV activities, can be smoothly amidated, thus offering a mild protocol for their late stage functionalization. 相似文献
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Synthesis of 1,1‐Diborylalkenes through a Brønsted Base Catalyzed Reaction between Terminal Alkynes and Bis(pinacolato)diboron 下载免费PDF全文
Akira Morinaga Kazunori Nagao Prof. Dr. Hirohisa Ohmiya Prof. Dr. Masaya Sawamura 《Angewandte Chemie (International ed. in English)》2015,54(52):15859-15862
A method for the synthesis of 1,1‐diborylalkenes through a Brønsted base catalyzed reaction between terminal alkynes and bis(pinacolato)diboron has been developed. The procedure allows direct synthesis of functionalized 1,1‐diborylalkenes from various terminal alkynes including propiolates, propiolamides, and 2‐ethynylazoles. 相似文献
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Rong Luo Ying Chen Ayusman Sen 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5499-5505
The first copolymerization of acrylate and methacrylate with nonpolar 1‐alkenes in the presence of Brønsted acids as complexation agents has been reported. The addition of both homogeneous and heterogeneous Brønsted acids resulted in increased monomer conversion and 1‐alkene incorporation. Further, the heterogeneous Brønsted acids can be recycled without loss of activity. A direct correlation exists between the ability of the Lewis or Brønsted acid to bind to the ester group of the acrylate/methacrylate monomer and its ability to promote the copolymerization reaction. For Lewis acids, there is also a direct correlation between the charge/size ratio at the metal center and their ability to promote copolymerizations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5499–5505, 2008 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(8):2091-2095
The catalytic asymmetric synthesis of both α‐substituted and α,α‐disubstituted (quaternary) β‐tetralones through direct α‐functionalization of the corresponding β‐tetralone precursor remains elusive. A designed Brønsted base‐squaramide bifunctional catalyst promotes the conjugate addition of either unsubstituted or α‐monosubstituted β‐tetralones to nitroalkenes. Under these reaction conditions, not only enolization, and thus functionalization, occurs at the α‐carbon atom of the β‐tetralone exclusively, but adducts including all‐carbon quaternary centers are also formed in highly diastereo‐ and enantioselective manner. 相似文献
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Olatz Olaizola Igor Iriarte Giovanna Zanella Enrique Gmez‐Bengoa Iaki Ganboa Mikel Oiarbide Claudio Palomo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14388-14392
A catalyst‐driven one‐pot reaction sequence is developed for the enantio‐ and diastereoselective synthesis of tetrasubstituted cyclohexenes from simple unsaturated ketones or thioesters. The method involves a tertiary amine/squaramide‐catalyzed α‐selective addition of transiently generated trienolates to nitroolefins, subsequent base‐catalyzed double bond isomerization, and an intramolecular (vinylogous) 1,6‐addition reaction, a rare key carbocyclization step that proceeded with essentially perfect stereocontrol. 相似文献
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《应用有机金属化学》2017,31(2)
A metal–organic framework Al‐MIL‐53‐NH2‐derived Brønsted acid catalyst (Al‐MIL‐53‐RSO3H) has been synthesized employing a post‐synthetic modification strategy under mild conditions. The Al‐MIL‐53‐RSO3H catalyst was successfully utilized in the nitro‐Mannich reaction taking advantage of its strong Brønsted acidity. Good to excellent yields of Mannich adducts were achieved for a variety of acylimine substrates in the presence of 0.1 mol% Al‐MIL‐53‐RSO3H. Furthermore, the Al‐MIL‐53‐RSO3H catalyst can be recycled five times without decreasing the yield and selectivity of Mannich adducts. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(5):1411-1415
Tetratrifylpropene (TTP) has been developed as a highly acidic, allylic C–H acid for Brønsted and Lewis acid catalysis. It can readily be obtained in two steps and consistently shows exceptional catalytic activities for Mukaiyama aldol, Hosomi–Sakurai, and Friedel–Crafts acylation reactions. X‐ray analyses of TTP and its salts confirm its designed, allylic structure, in which the negative charge is delocalized over four triflyl groups. NMR experiments, acidity measurements, and theoretical investigations provide further insights to rationalize the remarkable reactivity of TTP. 相似文献
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Ruthenium(II)/Chiral Brønsted Acid Co‐Catalyzed Enantioselective Four‐Component Reaction/Cascade Aza‐Michael Addition for Efficient Construction of 1,3,4‐Tetrasubstituted Tetrahydroisoquinolines 下载免费PDF全文
Dr. Jun Jiang Xiaochu Ma Dr. Changge Ji Dr. Zhenqiu Guo Taoda Shi Dr. Shunying Liu Prof. Wenhao Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1505-1509
An elegant synergistic catalytic system comprising a ruthenium complex with a chiral Brønsted acid was developed for a four‐component Mannich/cascade aza‐Michael reaction. The ruthenium‐associated ammonium ylides successfully trapped with in situ generated imines indicates a stepwise process of proton transfer in the ruthenium‐catalyzed carbenoid N?H insertion reaction. The different decomposition abilities of various ruthenium complexes towards diazo compounds were well explained by the calculated thermodynamic data. The transformation features a mild, rapid, and efficient method for the synthesis of enantiomerically pure 1,3,4‐tetrasubstituted tetrahydroquinolines bearing a quaternary stereogenic carbon center from simple starting precursors in moderate yields with high diastereo‐ and enantioselectivity. 相似文献
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Dr. Luis F. R. Gomes Prof. Dr. Luís F. Veiros Prof. Dr. Nuno Maulide Prof. Dr. Carlos A. M. Afonso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1449-1453
Carbene intermediates are very useful species for a range of reactions including C?H insertions and cycloadditions. They are most commonly generated by metal‐catalyzed release of nitrogen gas from diazo precursors. Herein, we present a novel C?H insertion of simple β‐ketoamide substrates, through reaction with (diacetoxyiodo)benzene (DIB) in the presence of a base. This unprecedented transformation bypasses the use of either diazo precursors or metal catalysts and directly delivers β‐lactam products by an iodonium ylide, in a single step under mild conditions. Mechanistic studies support the intermediacy of a free singlet carbene of unique reactivity and selectivity. 相似文献
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A Regioselective Synthesis of Benzopinacolones through Aerobic Dehydrogenative α‐Arylation of the Tertiary sp3 CH Bond of 1,1‐Diphenylketones with Aromatic and Heteroaromatic Compounds 下载免费PDF全文
Nagnath Yadav More Dr. Masilamani Jeganmohan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1337-1342
A regioselective synthesis of symmetrical and unsymmetrical benzopinacolones through aerobic dehydrogenative α‐arylation at the tertiary sp3 C?H bond of substituted 1,1‐diphenylketones with aromatic and heteroaromatic compounds, in the presence of K2S2O8 in CF3COOH at room temperature, is described. The reaction is proposed to go via a carbocation intermediate, which could be generated directly from cleavage of the sp3 C?H bond of 1,1‐diphenylketone. Subsequent α‐arylation was achieved at the methene sp3 carbon atom of the substituted ketone. A variety of substituted aromatic and heteroaromatic compounds were compatible with this reaction. In addition, benzopinacolones were converted into sterically hindered, tetrasubstituted alkenes and polycyclic aromatic compounds. 相似文献
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The Brønsted acidity of the various Si(nAl) sites present in zeolites is evaluated from proton binding energy and LUMO energy calculated by the semiempirical MNDO quantum chemical method. The two calculated energy values both exhibit a linear correlation with the existing 29Si NMR chemical shift and the IR hydroxyl stretching frequency data. The inter-convertibility between different Si(nAl) sites during an alumination or dealumination process is also evaluated based on the calculated substitution energy. The results indicate that alumination processes are less favorable to occur in zeolites than dealumination processes and the latter is more likely to occur for Si(nAl) clusters that contain the maximum number of aluminum nearest neighbors. 相似文献
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Intramolecular CH Activation and Metallacycle Aromaticity in the Photochemistry of [FeFe]‐Hydrogenase Model Compounds in Low‐Temperature Frozen Matrices 下载免费PDF全文
Wyatt A. Thornley Prof. Thomas E. Bitterwolf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18218-18229
The [FeFe]‐hydrogenase model complexes [(μ‐pdt){Fe(CO)3}2], [(μ‐edt){Fe(CO)3}2], and [(μ‐mdt){Fe(CO)3}2], where pdt=1,3‐propanedithiolate, edt=1,2‐ethanedithiolate, and mdt=methanedithiolate, undergo wavelength dependent photodecarbonylation in hydrocarbon matrices at 85 K resulting in multiple decarbonylation isomers. As previously reported in time‐resolved solution photolysis experiments, the major photoproduct is attributed to a basal carbonyl‐loss species. Apical carbonyl‐loss isomers are also generated and may undergo secondary photolysis, resulting in β‐hydride activation of the alkyldithiolate bridge, as well as formation of bridging carbonyl isomers. For [(μ‐bdt){Fe(CO)3}2], (bdt=1,2‐benzenedithiolate), apical photodecarbonylation results in generation of a 10 π‐electron aromatic FeS2C6H4 metallacycle that coordinates the remaining iron through an η5 mode. 相似文献
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MIL‐101‐SO3H: A Highly Efficient Brønsted Acid Catalyst for Heterogeneous Alcoholysis of Epoxides under Ambient Conditions 下载免费PDF全文
Yu‐Xiao Zhou Yu‐Zhen Chen Yingli Hu Gang Huang Prof. Dr. Shu‐Hong Yu Prof. Dr. Hai‐Long Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):14976-14980
For the first time, a ~100 % sulfonic acid functionalized metal–organic framework (MOF), MIL‐101‐SO3H, with giant pores has been prepared by a hydrothermal process followed by a facile postsynthetic HCl treatment strategy. The replete readily accessible Lewis acidic and especially Brønsted acidic sites distributed throughout the framework as well as high stability endow the resultant MOF exceptionally high efficiency and recyclability, which surpass all other MOF‐based catalysts, for the ring opening of epoxides with alcohols (especially, methanol) as nucleophiles under ambient conditions. 相似文献