共查询到20条相似文献,搜索用时 15 毫秒
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Zi‐Qiang Rong Min Wang Chi Hao Eugene Chow Prof. Yu Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9483-9487
Highly efficient and diastereodivergent aza‐Diels–Alder reactions have been developed to access either diastereomeric series of benzofuran‐fused δ‐lactams and dihydropyridines in nearly perfect stereoselectivity (d.r. >20:1, >99 % ee for all examples). The complementarity of N‐heterocyclic carbene and chiral amine as the catalyst was demonstrated for the first time, together with an excellent level of catalytic efficiency (1 mol % loading). 相似文献
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Cascade Olefin Isomerization/Intramolecular Diels–Alder Reaction Catalyzed by N‐Heterocyclic Carbenes 下载免费PDF全文
Marcin Kowalczyk Dr. David W. Lupton 《Angewandte Chemie (International ed. in English)》2014,53(21):5314-5317
The addition of an N‐heterocyclic carbene to the carbonyl group of an α,β,γ,δ‐unsaturated enol ester affords a hemiacetal azolium intermediate that enables a cascade olefin isomerization/Diels–Alder reaction, for which mechanistic studies implicate Lewis base catalysis. Preliminary studies into the utility of the products have been undertaken with reductive and oxidative cleavage, giving materials for potential use in complex‐target synthesis. 相似文献
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Chiral Dawson‐Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels–Alder Reactions 下载免费PDF全文
Wen‐Jing Xuan Dr. Candice Botuha Prof. Bernold Hasenknopf Prof. Serge Thorimbert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16512-16516
Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C?C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate‐based catalyst for asymmetric Diels–Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels–Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners. 相似文献
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Dr. Jacques‐Alexis Funel Dr. Stefan Abele 《Angewandte Chemie (International ed. in English)》2013,52(14):3822-3863
The Diels–Alder reaction is one of the most popular transformations for organic chemists to generate molecular complexity efficiently. Surprisingly, little is known about its industrial application for the synthesis of pharmacologically active ingredients, agrochemicals, and flavors and fragrances. This Review highlights selected examples, with a focus on large‐scale applications (>1 kg) from a process research and development perspective. 相似文献
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Dr. Pablo A. Denis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15719-15725
Herein, by using dispersion‐corrected density functional theory, we investigated the Diels–Alder chemistry of pristine and defective graphene. Three dienes were considered, namely 2,3‐dimethoxy‐1,3‐butadiene (DMBD), 9‐methylanthracene (9MA), and 9,10‐dimethylanthracene (910DMA). The dienophiles that were assayed were tetracyanoethylene (TCNE) and maleic anhydride (MA). When pristine graphene acted as the dienophile, we found that the cycloaddition products were 47–63 kcal mol?1 less stable than the reactants, thus making the reaction very difficult. The presence of Stone–Wales translocations, 585 double vacancies, or 555‐777 reconstructed double vacancies did not significantly improve the reactivity because the cycloaddition products were still located at higher energy than the reactants. However, for the addition of 910DMA to single vacancies, the product showed comparable stability to the separated reactants, whereas for unsaturated armchair edges the reaction was extremely favorable. With regards the reactions with dienophiles, for TCNE, the cycloaddition product was metastable. In the case of MA, we observed a reaction product that was less stable than the reactants by 50 kcal mol?1. For the reactions between graphene as a diene and the dienophiles, we found that the most‐promising defects were single vacancies and unsaturated armchair edges, because the other three defects were much‐less reactive. Thus, we conclude that the reactions with these above‐mentioned dienes may proceed on pristine or defective sheets with heating, despite being endergonic. The same statement also applies to the dienophile maleic anhydride. However, for TCNE, the reaction is only likely to occur onto single vacancies or unsaturated armchair edges. We conclude that the dienophile character of graphene is slightly stronger than its behavior as a diene. 相似文献
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Inside Cover: Bioinspired Intramolecular Diels–Alder Reaction: A Rapid Access to the Highly‐Strained Cyclopropane‐Fused Polycyclic Skeleton (Chem. Eur. J. 9/2014) 下载免费PDF全文
Prof. Dr. Shifa Zhu Zhengjiang Guo Zhipeng Huang Prof. Dr. Huanfeng Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2390-2390
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Thomas Varlet Coralie Gelis Pascal Retailleau Guillaume Bernadat Luc Neuville Graldine Masson 《Angewandte Chemie (International ed. in English)》2020,59(22):8491-8496
An efficient enantioselective construction of tetrahydronaphthalene‐1,4‐diones as well as dihydronaphthalene‐1,4‐diols by a chiral phosphoric acid catalyzed quinone Diels–Alder reaction with dienecarbamates is reported. The nature of the protecting group on the diene is key to the success of achieving high enantioselectivity. The divergent “redox” selectivity is controlled by using an adequate amount of quinones. Reversible redox switching without erosion of enantioselectivity was possible from individual redox isomers. 相似文献
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K. C. Nicolaou Scott A. Snyder Tamsyn Montagnon Georgios Vassilikogiannakis 《Angewandte Chemie (International ed. in English)》2002,41(10):1668-1698
The Diels–Alder reaction has both enabled and shaped the art and science of total synthesis over the last few decades to an extent which, arguably, has yet to be eclipsed by any other transformation in the current synthetic repertoire. With myriad applications of this magnificent pericyclic reaction, often as a crucial element in elegant and programmed cascade sequences facilitating complex molecule construction, the Diels–Alder cycloaddition has afforded numerous and unparalleled solutions to a diverse range of synthetic puzzles provided by nature in the form of natural products. In celebration of the 100th anniversary of Alder's birth, selected examples of the awesome power of the reaction he helped to discover are discussed in this review in the context of total synthesis to illustrate its overall versatility and underscore its vast potential which has yet to be fully realized. 相似文献
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Andreas Mavroskoufis Keerthana Rajes Paul Golz Arush Agrawal Vincent Ruß Jan P. Gtze Matthew N. Hopkinson 《Angewandte Chemie (International ed. in English)》2020,59(8):3190-3194
The combination of light activation and N‐heterocyclic carbene (NHC) organocatalysis has enabled the use of acid fluorides as substrates in a UVA‐light‐mediated photochemical transformation previously observed only with aromatic aldehydes and ketones. Stoichiometric studies and TD‐DFT calculations support a mechanism involving the photoactivation of an ortho‐toluoyl azolium intermediate, which exhibits “ketone‐like” photochemical reactivity under UVA irradiation. Using this photo‐NHC catalysis approach, a novel photoenolization/Diels–Alder (PEDA) process was developed that leads to diverse isochroman‐1‐one derivatives. 相似文献
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An organocatalyst formed from a binaphthyl‐substituted diamine and trifluoromethanesulfonic acid exhibited unprecedented levels of exo selectivity in the Diels–Alder reaction of α,β‐unsaturated aldehydes with cyclopentadiene. A novel axially chiral diamine was also designed as an organocatalyst for an asymmetric variant of this reaction, in which the desired cycloadducts were formed with high diastereo‐ and enantioselectivities. The highest diastereoselectivity observed was greater than 20:1 in favor of the exo cycloadduct in the asymmetric Diels–Alder reaction of crotonaldehyde with cyclopentadiene. 相似文献
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Dr. Misal Giuseppe Memeo Prof. Paolo Quadrelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12554-12582
This review highlights the state of the art of the use of iminium ions as dienophiles in Aza‐Diels–Alder (ADA) cycloadditions. An historical survey spanning the very first discovery of the reaction to modern developments, mechanistic studies and synthetic applications of the iminium variant of the ADA (iADA) reaction are presented. The discussion is focused on the intermolecular and intramolecular versions of the iADA reactions that are conducted in aqueous solutions to generate, in situ, the reactive dienophile from an amine hydrochloride and either aliphatic or aromatic aldehydes in the presence of a variety of dienes. The retro‐ADA reaction is also presented as an interesting method for the protection of amines. The use of Lewis acid catalysis in these reactions was thoroughly studied by the reactions of different amines and aldehydes conducted in the presence of lanthanide(III) complexes. 相似文献
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Marc Garcia‐Borràs Dr. Josep M. Luis Prof. Dr. Marcel Swart Prof. Dr. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(14):4468-4479
One of the most important reactions in fullerene chemistry is the Diels–Alder (DA) reaction. In two previous experimental studies, the DA cycloaddition reactions of cyclopentadiene (Cp) and 1,2,3,4,5‐pentamethylcyclopentadiene (Cp*) with La@C2v‐C82 were investigated. The attack of Cp was proposed to occur on bond 19 , whereas that of Cp* was confirmed by X‐ray analysis to be over bond o . Moreover, the stabilities of the Cp and Cp* adducts were found to be significantly different, that is, the decomposition of La@C2v‐C82Cp was one order of magnitude faster than that of La@C2v‐C82Cp*. Herein, we computationally analyze these DA cycloadditions with two main goals: First, to compute the thermodynamics and kinetics of the cycloadditions of Cp and Cp* to different bonds of La@C2v‐C82 to assess and compare the regioselectivity of these two reactions. Second, to understand the origin of the different thermal stabilities of the La@C82Cp and La@C82Cp* adducts. Our results show that the regioselectivity of the two DA cycloadditions is the same, with preferred attack on bond o . This result corrects the previous assumption of the regioselectivity of the Cp attack that was made based only on the shape of the La@C82 singly occupied molecular orbital. In addition, we show that the higher stability of the La@C82Cp* adduct is not due to the electronic effects of the methyl groups on the Cp ring, as previously suggested, but to higher long‐range dispersion interactions in the Cp* case, which enhance the stabilization of the reactant complex, transition state, and products with respect to the separated reactants. This stabilization for the La@C82Cp* case decreases the Gibbs reaction energy, thus allowing competition between the direct and retro reactions and making dissociation more difficult. 相似文献
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Florian L. Geyer Alexander Rode Prof. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16448-16453
A series of ethynylated silanes, including tetraethynylsilane, was treated with tetraphenylcyclopentadienone at 300 °C under microwave irradiation to give the aromatized Diels–Alder adducts as sterically encumbered mini‐dendrimers with up to 20 benzene rings. The sterically most congested adducts display red‐shifted emission through intramolecular π–π interactions in the excited state. 相似文献
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