共查询到20条相似文献,搜索用时 140 毫秒
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Direct N‐Glycofunctionalization of Amides with Glycosyl Trichloroacetimidate by Thiourea/Halogen Bond Donor Co‐Catalysis 下载免费PDF全文
Dr. Yusuke Kobayashi Yuya Nakatsuji Shanji Li Dr. Seiji Tsuzuki Prof. Dr. Yoshiji Takemoto 《Angewandte Chemie (International ed. in English)》2018,57(14):3646-3650
Using a halogen bond (XB) donor and Schreiner's thiourea as cooperative catalysts, various amides, including the asparagine residues of several peptides, were directly coupled with glycosyl trichloroacetimidates to give unique N‐acylorthoamides in good yields. Synthetic applications of N‐acylorthoamides, including rearrangement to the corresponding β‐N‐glycoside, were also demonstrated. 相似文献
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Lisa Kötzner Dr. Matthew J. Webber Dr. Alberto Martínez Dr. Claudia De Fusco Prof. Dr. Benjamin List 《Angewandte Chemie (International ed. in English)》2014,53(20):5202-5205
The first asymmetric organocatalytic synthesis of helicenes is reported. A novel SPINOL‐derived phosphoric acid, bearing extended π‐substituents, catalyzes the asymmetric synthesis of helicenes through an enantioselective Fischer indole reaction. A variety of azahelicenes and diazahelicenes could be obtained with good to excellent yields and enantioselectivities. 相似文献
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《Angewandte Chemie (International ed. in English)》2018,57(29):9176-9179
An efficient method for the benzenium‐ion‐mediated cleavage of inert Si−C(sp3) bonds is reported. Various tetraalkylsilanes can thus be converted into the corresponding counteranion‐stabilized silylium ions. The reaction is chemoselective in the case of hexamethyldisilane. Computations reveal a mechanism with backside attack of the proton at one of the alkyl groups. Several activated Si−C(spn) bonds (n=3–1) react equally well, and the procedure can be extended to the generation of stannylium ions. 相似文献
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Inside Cover: Asymmetric Catalysis on the Nanoscale: The Organocatalytic Approach to Helicenes (Angew. Chem. Int. Ed. 20/2014) 下载免费PDF全文
Lisa Kötzner Dr. Matthew J. Webber Dr. Alberto Martínez Dr. Claudia De Fusco Prof. Dr. Benjamin List 《Angewandte Chemie (International ed. in English)》2014,53(20):4980-4980
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Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation 下载免费PDF全文
Dr. Chao Xu Calum W. Muir Dr. Andrew G. Leach Dr. Alan R. Kennedy Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2018,57(35):11374-11377
The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N‐heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular asymmetric proton transfer from the ion‐paired prochiral intermediate. 相似文献
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Enantioselective Formal [3+2] Cycloaddition of Epoxides with Imines under Brønsted Base Catalysis: Synthesis of 1,3‐Oxazolidines with Quaternary Stereogenic Center 下载免费PDF全文
Dr. Azusa Kondoh Shiori Akahira Masafumi Oishi Prof. Dr. Masahiro Terada 《Angewandte Chemie (International ed. in English)》2018,57(21):6299-6303
The formal [3+2] cycloaddition of epoxides and unsaturated compounds is a powerful methodology for the synthesis of densely functionalized five‐membered heterocyclic compounds containing oxygen. Described is a novel enantioselective formal [3+2] cycloaddition of epoxides under Brønsted base catalysis. The bis(guanidino)iminophosphorane as a chiral organosuperbase catalyst enabled the enantioselective reaction of β,γ‐epoxysulfones with imines, owing to its strong basicity and high stereocontrolling ability, to provide enantioenriched 1,3‐oxazolidines having two stereogenic centers, including a quaternary one, in a highly diastereo‐ and enantioselective manner. 相似文献
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Masahiro Terada Prof. Dr. Kyoko Machioka Keiichi Sorimachi 《Angewandte Chemie (International ed. in English)》2009,48(14):2553-2556
An enriching experience : Chiral phosphoric acids have been used to catalyze the title transformation for aromatic and aliphatic hemiaminal ethers. The process affords the corresponding products in good to high enantioselectivity (see scheme; Boc=tert‐butoxycarbonyl, G=aromatic group). The method enables facile access to highly enantioenriched 1,3‐diamine derivatives.
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Chang Min Chih‐Tsung Lin Prof. Dr. Daniel Seidel 《Angewandte Chemie (International ed. in English)》2015,54(22):6608-6612
A readily available chiral Brønsted acid was identified as an efficient catalyst for intramolecular Povarov reactions. Polycyclic amines containing three contiguous stereogenic centers were obtained with excellent stereocontrol in a single step from secondary anilines and aldehydes possessing a pendent dienophile. These transformations constitute the first examples of catalytic enantioselective intramolecular aza‐Diels–Alder reactions. 相似文献
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Dr. Gavin Chit Tsui Luping Liu Prof. Dr. Benjamin List 《Angewandte Chemie (International ed. in English)》2015,54(26):7703-7706
We describe here the design and development of an organocatalytic Prins cyclization. In the presence of a confined chiral imidodiphosphoric acid catalyst, salicylaldehydes react with 3‐methyl‐3‐buten‐1‐ol to afford highly functionalized 4‐methylenetetrahydropyrans in excellent regio‐ and enantioselectivity. The extreme steric demand of the acid catalyst is key for the success of this transformation. 相似文献
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Brønsted Acid‐Catalyzed,Highly Enantioselective Addition of Enamides to In Situ‐Generated ortho‐Quinone Methides: A Domino Approach to Complex Acetamidotetrahydroxanthenes 下载免费PDF全文
Dr. Satyajit Saha Prof. Dr. Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2348-2352
The highly enantioselective conjugate addition of enamides and enecarbamates to in situ‐generated ortho‐quinone methides, upon subsequent N,O‐acetalization, gives rise to acetamido‐substituted tetrahydroxanthenes with generally excellent enantio‐ and diastereoselectivities. A chiral BINOL‐based phosphoric acid catalyst controls the enantioselectivity of the carbon–carbon bond‐forming event. The products are readily converted into other xanthene‐based heterocycles. 相似文献
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A Brønsted acid catalyzed direct alkylation reaction of aldehydes was described. The 3,5‐dinitrobenzoic acid promoted the reaction between aldehydes and diarylmethanols to afford the corresponding alkylation products with middle to high yields (up to 91% yield). 相似文献
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The Prins cyclization of enol ethers has been realized by employing BiX3 (or FeX3) as catalyst and TMSX (X=Br, Cl) as the halogen source. The presence of a tiny amount of water in the solvent dichloromethane played a key role for the reaction to proceed. The reaction is believed to be catalyzed by Lewis acid‐assisted Brønsted acids, which were generated in situ from MX3 and water in the solvent. 相似文献
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Aminomethylation of Enals through Carbene and Acid Cooperative Catalysis: Concise Access to β2‐Amino Acids 下载免费PDF全文
Dr. Jianfeng Xu Xingkuan Chen Dr. Ming Wang Pengcheng Zheng Bao‐An Song Prof. Dr. Yonggui Robin Chi 《Angewandte Chemie (International ed. in English)》2015,54(17):5161-5165
A convergent, organocatalytic asymmetric aminomethylation of α,β‐unsaturated aldehydes by N‐heterocyclic carbene (NHC) and (in situ generated) Brønsted acid cooperative catalysis is disclosed. The catalytically generated conjugated acid from the base plays dual roles in promoting the formation of azolium enolate intermediate, formaldehyde‐derived iminium ion (as an electrophilic reactant), and methanol (as a nucleophilic reactant). This redox‐neutral strategy is suitable for the scalable synthesis of enantiomerically enriched β2‐amino acids bearing various substituents. 相似文献