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61.
Highly Enantioselective Intermolecular Cross Rauhut–Currier Reaction Catalyzed by a Multifunctional Lewis Base Catalyst 下载免费PDF全文
Xuelin Dong Ling Liang Erqing Li Prof. Dr. You Huang 《Angewandte Chemie (International ed. in English)》2015,54(5):1621-1624
The highly enantioselective intermolecular cross Rauhut–Currier reaction of different active olefins catalyzed by a multifunctional chiral Lewis base was reported. The RC products were obtained in excellent yields (up to 98 %), high chemo‐ and enantioselectivity (up to 96 % ee). The reaction could be performed on a gram scale using 1 mol % of the multifunctional phosphine catalyst. 相似文献
62.
Guang‐Hui Ouyang Yan‐Mei He Yong Li Jun‐Feng Xiang Prof. Dr. Qing‐Hua Fan 《Angewandte Chemie (International ed. in English)》2015,54(14):4334-4337
An aza‐crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host–guest interactions. In the OFF state, the catalyst is almost inactive (less than 1 % conversion) because of the formation of an intermolecular sandwich complex by two aza‐crown ether moities and the cationic rhodium metal center. In using alkali‐metal‐cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98 % ee). 相似文献
63.
Enantioselective Construction of Spiroindolines with Three Contiguous Stereogenic Centers and Chiral Tryptamine Derivatives via Reactive Spiroindolenine Intermediates 下载免费PDF全文
Dr. Chun‐Xiang Zhuo Yong Zhou Qiang Cheng Lin Huang Prof. Dr. Shu‐Li You 《Angewandte Chemie (International ed. in English)》2015,54(47):14146-14149
The highly efficient synthesis of the enantioenriched spiroindolines by iridium‐catalyzed asymmetric allylic dearomatization and reduction is presented. Spiroindolines containing three contiguous stereogenic centers were obtained with excellent diastereo‐ and enantioselectivity. In addition, a chiral tryptamine derivative could be easily accessed in good yield with excellent ee value through an unprecedented dearomatization/retro‐Mannich/hydrolysis cascade reaction of an indole derivative. 相似文献
64.
Dr. Shiwen Wang Dr. Lijiang Wang Dr. Zhiqiang Zhu Zhe Hu Dr. Qing Zhao Prof. Dr. Jun Chen 《Angewandte Chemie (International ed. in English)》2014,53(23):5892-5896
Developing organic compounds with multifunctional groups to be used as electrode materials for rechargeable sodium‐ion batteries is very important. The organic tetrasodium salt of 2,5‐dihydroxyterephthalic acid (Na4DHTPA; Na4C8H2O6), which was prepared through a green one‐pot method, was investigated at potential windows of 1.6–2.8 V as the positive electrode or 0.1–1.8 V as the negative electrode (vs. Na+/Na), each delivering compatible and stable capacities of ca. 180 mAh g?1 with excellent cycling. A combination of electrochemical, spectroscopic and computational studies revealed that reversible uptake/removal of two Na+ ions is associated with the enolate groups at 1.6–2.8 V (Na2C8H2O6/Na4C8H2O6) and the carboxylate groups at 0.1–1.8 V (Na4C8H2O6/Na6C8H2O6). The use of Na4C8H2O6 as the initial active materials for both electrodes provided the first example of all‐organic rocking‐chair SIBs with an average operation voltage of 1.8 V and a practical energy density of about 65 Wh kg?1. 相似文献
65.
MoS2 Nanoflowers with Expanded Interlayers as High‐Performance Anodes for Sodium‐Ion Batteries 下载免费PDF全文
Zhe Hu Lixiu Wang Dr. Kai Zhang Dr. Jianbin Wang Prof. Fangyi Cheng Prof. Zhanliang Tao Prof. Jun Chen 《Angewandte Chemie (International ed. in English)》2014,53(47):12794-12798
MoS2 nanoflowers with expanded interlayer spacing of the (002) plane were synthesized and used as high‐performance anode in Na‐ion batteries. By controlling the cut‐off voltage to the range of 0.4–3 V, an intercalation mechanism rather than a conversion reaction is taking place. The MoS2 nanoflower electrode shows high discharge capacities of 350 mAh g?1 at 0.05 A g?1, 300 mAh g?1 at 1 A g?1, and 195 mAh g?1 at 10 A g?1. An initial capacity increase with cycling is caused by peeling off MoS2 layers, which produces more active sites for Na+ storage. The stripping of MoS2 layers occurring in charge/discharge cycling contributes to the enhanced kinetics and low energy barrier for the intercalation of Na+ ions. The electrochemical reaction is mainly controlled by the capacitive process, which facilitates the high‐rate capability. Therefore, MoS2 nanoflowers with expanded interlayers hold promise for rechargeable Na‐ion batteries. 相似文献
66.
[HCo(CO)4]‐Catalyzed Three‐component Cycloaddition of Epoxides,Imines, and Carbon Monoxide: Facile Construction of 1,3‐Oxazinan‐4‐ones 下载免费PDF全文
The three‐component [3+2+1] cycloaddition of epoxides, imines, and carbon monoxide to produce 1,3‐oxazinan‐4‐ones has been developed by using [HCo(CO)4] as the catalyst. The reaction occurs for a wide variety of imines and epoxides, under 60 bar of CO pressure at 50 °C, to produce 1,3‐oxazinan‐4‐ones with different substitution patterns in high yields, and provides an efficient and atom‐economic route to heterocycles from simple and readily available starting materials. A plausible mechanism involves [HCo(CO)4]‐induced ring‐opening of the epoxide, followed by sequential addition of carbon monoxide and the imine, and then ring closure to form the product accompanied by regeneration of [HCo(CO)4]. 相似文献
67.
Origins of the Enantio‐ and N/O Selectivity in the Primary‐Amine‐Catalyzed Hydroxyamination of 1,3‐Dicarbonyl Compounds with In‐Situ‐Formed Nitrosocarbonyl Compounds: A Theoretical Study 下载免费PDF全文
Dr. Long Zhang Changming Xu Prof. Dr. Xueling Mi Prof. Dr. Sanzhong Luo 《化学:亚洲杂志》2014,9(12):3565-3571
Chemoselective control over N/O selectivity is an intriguing issue in nitroso chemistry. Recently, we reported an unprecedented asymmetric α‐amination reaction of β‐ketocarbonyl compounds that proceeded through the catalytic coupling of enamine carbonyl groups with in‐situ‐generated carbonyl nitroso moieties. This process was facilitated by a simple chiral primary and tertiary diamine that was derived from tert‐leucine. This reaction featured high chemoselectivity and excellent enantioselectivity for a broad range of substrates. Herein, a computational study was performed to elucidate the origins of the enantioselectivity and N/O regioselectivity. We found that a bidentate hydrogen‐bonding interaction between the tertiary N+? H and nitrosocarbonyl groups accounted for the high N selectivity, whilst the enantioselectivity was determined by Si‐facial attack on the (E)‐ and (Z)‐enamines in a Curtin–Hammett‐type manner. The bidentate hydrogen‐bonding interaction with the nitrosocarbonyl moieties reinforced the facial selectivity in this process. 相似文献
68.
Zhi‐Qiang Li Dr. Ying‐Ming Zhang Prof. Dr. Yong Chen Prof. Dr. Yu Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8566-8570
The extremely strong noncovalent complexation between the rigid host of phthalocyanine‐bridged β‐cyclodextrins and the amphiphilic guest carboxylated porphyrin is employed to construct a hollow tubular structure as a supramolecular nanoreactor. A representative coupling reaction occurs in the hydrophobic interlayers of the tubular walls in pure water at room temperature, leading to an enhancement of ten times higher reaction rate without any adverse effect on catalytic activity and conversion. 相似文献
69.
Podand‐Based Dimeric Chromium(III)–Salen Complex for Asymmetric Henry Reaction: Cooperative Catalysis Promoted by Complexation of Alkali Metal Ions 下载免费PDF全文
Guang‐Hui Ouyang Yan‐Mei He Prof. Dr. Qing‐Hua Fan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16454-16457
A new kind of podand‐based dimeric salen ligand was synthesized, and its association with potassium cations was investigated by 1H NMR spectroscopy. The corresponding CrIII–salen dimer was assembled by a supramolecular host–guest self‐assembly process and was then used as a catalyst in highly efficient and enantioselective asymmetric Henry reactions. Regulation by KBArF (BArF=[3,5‐(CF3)2C6H3]4B) led to remarkable improvements in yield (by up to 58 %) and enantioselectivity (for example, from 80 % ee to 96 % ee). 相似文献
70.
Taming Living Carbocations in Catalytic Direct Conjugate Addition of Simple Alkenes to α,β‐Enones 下载免费PDF全文
Dr. Jian Lv Xingren Zhong Prof. Dr. Sanzhong Luo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8293-8296
A Lewis acid in the presence of an anionic phosphate ligand enables the addition of alkenes to α,β‐enones. The ligand facilitates selective β‐proton elimination by suppressing competing pathways, thus leading to vinylation adducts in high yields (up to 99 %) for a broad range of substrates. 相似文献