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991.
Single‐Layered Ultrasmall Nanoplates of MoS2 Embedded in Carbon Nanofibers with Excellent Electrochemical Performance for Lithium and Sodium Storage 下载免费PDF全文
Dr. Changbao Zhu Dr. Xiaoke Mu Prof. Peter A. van Aken Prof. Yan Yu Prof. Joachim Maier 《Angewandte Chemie (International ed. in English)》2014,53(8):2152-2156
The preparation and electrochemical storage behavior of MoS2 nanodots—more precisely single‐layered ultrasmall nanoplates—embedded in carbon nanowires has been studied. The preparation is achieved by an electrospinning process that can be easily scaled up. The rate performance and cycling stability of both lithium and sodium storage were found to be outstanding. The storage behavior is, moreover, highly exciting from a fundamental point of view, as the differences between the usual storage modes—insertion, conversion, interfacial storage—are beneficially blurred. The restriction to ultrasmall reaction domains allows for an almost diffusion‐less and nucleation‐free “conversion”, thereby resulting in a high capacity and a remarkable cycling performance. 相似文献
992.
Quinones as Dienophiles in the Diels–Alder Reaction: History and Applications in Total Synthesis 下载免费PDF全文
Dr. Christopher C. Nawrat Prof. Dr. Christopher J. Moody 《Angewandte Chemie (International ed. in English)》2014,53(8):2056-2077
In the canon of reactions available to the organic chemist engaged in total synthesis, the Diels–Alder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carbon? carbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the Diels–Alder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60 years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines. 相似文献
993.
Atom‐Economic,Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes 下载免费PDF全文
Kun Xu Niels Thieme Prof. Dr. Bernhard Breit 《Angewandte Chemie (International ed. in English)》2014,53(8):2162-2165
New Rh‐ and Pd‐catalyzed regiodivergent and stereoselective intermolecular coupling reactions of imidazole derivatives with mono‐substituted allenes are herein reported. Using a RhI/Josiphos system, perfect regioselectivities and high enantiomeric excess were obtained, while a PdII/dppf system gave linear products with high regioselectivities and high E/Z selectivities. This method permits the atom economic synthesis of valuable branched and linear allylic imidazole derivatives. 相似文献
994.
Dr. Hongli Bao Liela Bayeh Prof. Uttam K. Tambar 《Angewandte Chemie (International ed. in English)》2014,53(6):1664-1668
New advances in the functionalization of unactivated olefins with carbon nucleophiles have provided more efficient and practical approaches to convert inexpensive starting materials into valuable products. Recent examples have been reported with stabilized carbon nucleophiles, tethered carbon nucleophiles, diazoesters, and trifluoromethane donors. A general method for functionalizing olefins with aromatic, aliphatic, and vinyl Grignard reagents was developed. In a one‐pot process, olefins are oxidized by a commercially available reagent to allylic electrophiles, which undergo selective copper‐catalyzed allylic alkylation with Grignard reagents. Products are formed in high yield and with high regioselectivity. This was utilized to synthesize a series of skipped dienes, a class of compounds that are prevalent in natural products and are difficult to synthesize by known allylic alkylation methods. 相似文献
995.
Palladium‐Catalyzed Oxidative Carbonylation of N‐Allylamines for the Synthesis of β‐Lactams 下载免费PDF全文
Wu Li Dr. Chao Liu Prof. Heng Zhang Keyin Ye Guanghui Zhang Wangzheng Zhang Zhengli Duan Prof. Shuli You Prof. Aiwen Lei 《Angewandte Chemie (International ed. in English)》2014,53(9):2443-2446
β‐Lactam scaffolds are considered to be ideal building blocks for the synthesis of nitrogen‐containing compounds. A new palladium‐catalyzed oxidative carbonylation of N‐allylamines for the synthesis of α‐methylene‐β‐lactams is reported. DFT calculations suggest that the formation of β‐lactams via a four‐membered‐ring transition state is favorable. 相似文献
996.
Dr. R. Fernando Martínez Zilei Liu Dr. Andreas F. G. Glawar Dr. Akihide Yoshihara Prof. Ken Izumori Prof. George W. J. Fleet Dr. Sarah F. Jenkinson 《Angewandte Chemie (International ed. in English)》2014,53(4):1160-1162
The scarcity and expense of access to L ‐sugars and other rare sugars have prevented the exploitation of their biological potential; for example D ‐psicose, only recently available, has been recognized as an important new food. Here we give the definitive and cheap synthesis of 99.4% pure L ‐glucose from D ‐glucose which requires purification of neither intermediates nor final product other than extraction into and removal of solvents; a simple crystallization will raise the purity to >99.8%. 相似文献
997.
Pd/C as a Catalyst for Completely Regioselective CH Functionalization of Thiophenes under Mild Conditions 下载免费PDF全文
Dan‐Tam D. Tang Dr. Karl D. Collins Johannes B. Ernst Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2014,53(7):1809-1813
The completely C3‐selective arylation of thiophenes and benzo[b]thiophenes was achieved by using Pd/C as a heterogeneous catalyst without ligands or additives under mild reaction conditions. The practicability of this transformation is demonstrated by notable functional group tolerance and the insensitivity of the reaction to H2O and air. This method is also applicable to nitrogen‐ and oxygen‐containing heterocycles, yielding the corresponding C2‐arylated products. Three‐phase tests along with Hg‐poisoning and hot‐filtration tests suggest that the catalytically active species is heterogeneous in nature. 相似文献
998.
Rhodium(III)‐Catalyzed ortho Alkenylation of N‐Phenoxyacetamides with N‐Tosylhydrazones or Diazoesters through CH Activation 下载免费PDF全文
Fangdong Hu Ying Xia Fei Ye Zhenxing Liu Prof. Dr. Chen Ma Prof. Dr. Yan Zhang Prof. Dr. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2014,53(5):1364-1367
A coupling reaction of N‐phenoxyacetamides with N‐tosylhydrazones or diazoesters through RhIII‐catalyzed C? H activation is reported. In this reaction, ortho‐alkenyl phenols were obtained in good yields and with excellent regio‐ and stereoselectivity. Rh–carbene migratory insertion is proposed as the key step in the reaction mechanism. 相似文献
999.
Enantioselective Synthesis of Boron‐Substituted Quaternary Carbon Stereogenic Centers through NHC‐Catalyzed Conjugate Additions of (Pinacolato)boron Units to Enones 下载免费PDF全文
Suttipol Radomkit Prof. Amir H. Hoveyda 《Angewandte Chemie (International ed. in English)》2014,53(13):3387-3391
The first examples of Lewis base catalyzed enantioselective boryl conjugate additions (BCAs) that generate products containing boron‐substituted quaternary carbon stereogenic centers are disclosed. Reactions are performed in the presence of 1.0–5.0 mol % of a readily accessible chiral accessible N‐heterocyclic carbene (NHC) and commercially available bis(pinacolato)diboron; cyclic or linear α,β‐unsaturated ketones can be used and rigorous exclusion of air or moisture is not necessary. The desired products are obtained in 63–95 % yield and 91:9 to >99:1 enantiomeric ratio (e.r.). The special utility of the NHC‐catalyzed approach is demonstrated in the context of an enantioselective synthesis of natural product antifungal (?)‐crassinervic acid. 相似文献
1000.
Azobenzene‐Functionalized Metal–Organic Polyhedra for the Optically Responsive Capture and Release of Guest Molecules 下载免费PDF全文
Dr. Jinhee Park Dr. Lin‐Bing Sun Ying‐Pin Chen Zachary Perry Prof. Dr. Hong‐Cai Zhou 《Angewandte Chemie (International ed. in English)》2014,53(23):5842-5846
Stimuli‐responsive metal–organic polyhedra (srMOPs) functionalized with azobenzene showed UV‐irradiation‐induced isomerization from the insoluble trans‐srMOP to the soluble cis‐srMOP, whereas irradiation with blue light reversed this process. Guest molecules were trapped and released upon cis‐to‐trans and trans‐to‐cis isomerization of the srMOPs, respectively. This study provides a new direction in the ever‐diversifying field of MOPs, while laying the groundwork for a new class of optically responsive materials. 相似文献