共查询到20条相似文献,搜索用时 593 毫秒
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Dr. Ceri Hammond Dr. Robert L. Jenkins Dr. Nikolaos Dimitratos Dr. Jose Antonio Lopez‐Sanchez Dr. Mohd Hasbi ab Rahim Dr. Michael M. Forde Adam Thetford Dr. Damien M. Murphy Dr. Henk Hagen Dr. Eric E. Stangland Prof. Jacob M. Moulijn Dr. Stuart H. Taylor Dr. David J. Willock Prof. Graham J. Hutchings 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15557-15557
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《International journal of quantum chemistry》2018,118(16)
Theoretical calculations were performed to elucidate the ability of the recently reported bis‐tert‐alcohol‐functionalized crown‐6‐calix[4]arene (BACCA) molecule to promote nucleophilic fluorination of alkyl mesylates with cesium fluoride reagent. It was found that a similar structure, named BACCAt, can separate the cesium fluoride ion pair in tert‐butanol solution. This separation has a free energy cost, even considering the double hydrogen bonds with the fluoride ion. The solvent has an important effect on the stabilization of this complex, due to interaction with the high dipole moment of the separated ion pair. The observed rate acceleration effect involves a structure with double hydrogen bonds between the BACCAt and the centers of negative charges of the SN2 transition state. The predicted free energy barrier of 27.3 kcal mol−1 is in excellent agreement with the estimated experimental value of 26.2 kcal mol−1. 相似文献
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Asymmetric Radical–Radical Cross‐Coupling through Visible‐Light‐Activated Iridium Catalysis 下载免费PDF全文
Chuanyong Wang Jie Qin Xiaodong Shen Radostan Riedel Dr. Klaus Harms Prof. Dr. Eric Meggers 《Angewandte Chemie (International ed. in English)》2016,55(2):685-688
Combining single electron transfer between a donor substrate and a catalyst‐activated acceptor substrate with a stereocontrolled radical–radical recombination enables the visible‐light‐driven catalytic enantio‐ and diastereoselective synthesis of 1,2‐amino alcohols from trifluoromethyl ketones and tertiary amines. With a chiral iridium complex acting as both a Lewis acid and a photoredox catalyst, enantioselectivities of up to 99 % ee were achieved. A quantum yield of <1 supports the proposed catalytic cycle in which at least one photon is needed for each asymmetric C? C bond formation mediated by single electron transfer. 相似文献
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Juliane Schmid Thorsten Junge Johannes Lang Wolfgang Frey Ren Peters 《Angewandte Chemie (International ed. in English)》2019,58(16):5447-5451
Achieving enzyme‐like catalytic activity and stereoselectivity without the typically high substrate specificity of enzymes is a challenge in the development of artificial catalysts for asymmetric synthesis. Polyfunctional catalysts are considered to be a promising tool for achieving excellent catalytic efficiency. A polyfunctional catalyst system was developed, which incorporates two Lewis acidic/Brønsted basic cobalt centers in combination with triazolium moieties that are crucial for high reactivity and excellent stereoselectivity in the direct 1,4‐addition of oxindoles to maleimides. The catalyst is assembled through click chemistry and is readily recyclable through precipitation by making use of its charges. Kinetic studies support a cooperative mode of action. Diastereodivergency is achievable with either Boc‐protected or unprotected maleimide. 相似文献
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Decarboxylative Aminomethylation of Aryl‐ and Vinylsulfonates through Combined Nickel‐ and Photoredox‐Catalyzed Cross‐Coupling 下载免费PDF全文
Dr. Lulu Fan Jiaqi Jia Dr. Hong Hou Dr. Quentin Lefebvre Prof. Dr. Magnus Rueping 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16437-16440
A mild approach for the decarboxylative aminomethylation of aryl sulfonates by the combination of photoredox and nickel catalysis through C?O bond cleavage is described for the first time. A wide range of aryl triflates as well as aryl mesylates, tosylates and alkenyl triflates afford the corresponding products in good to excellent yields. 相似文献
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Inside Back Cover: A Combined Transition‐Metal‐Catalyzed and Photopromoted Process: Synthesis of 2,3‐Fused 4‐Phenylnaphthalen‐1‐yl Carboxylates from 1,7‐Diaryl‐1,6‐diynes (Chem. Eur. J. 25/2015) 下载免费PDF全文
Prof. Dr. Yoshihiko Yamamoto Shota Mori Dr. Masatoshi Shibuya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(25):9263-9263
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Versatile In Situ Generated N‐Boc‐Imines: Application to Phase‐Transfer‐Catalyzed Asymmetric Mannich‐Type Reactions 下载免费PDF全文
Dr. Taichi Kano Ryohei Kobayashi Prof. Keiji Maruoka 《Angewandte Chemie (International ed. in English)》2015,54(29):8471-8474
The efficient construction of nitrogen‐containing organic compounds is a major challenge in chemical synthesis. Imines are one of the most important classes of electrophiles for this transformation. However, both the available imines and applicable nucleophiles for them are quite limited given the existing preparative methods. Described herein are imine precursors which generate reactive imines with a wide variety of substituents under mild basic conditions. This approach enables the construction of various nitrogen‐containing molecules which cannot be accessed by the traditional approach. The utility of the novel imine precursor was demonstrated in the asymmetric Mannich‐type reaction under phase‐transfer conditions. 相似文献