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71.
Guangfan Zheng Zhi Zhou Guoxun Zhu Shuailei Zhai Huiying Xu Xujing Duan Wei Yi Xingwei Li 《Angewandte Chemie (International ed. in English)》2020,59(7):2890-2896
Cyclopropane rings are a prominent structural motif in biologically active molecules. Enantio‐ and diastereoselective construction of cyclopropanes through C?H activation of arenes and coupling with readily available cyclopropenes is highly appealing but remains a challenge. A dual directing‐group‐assisted C?H activation strategy was used to realize mild and redox‐neutral RhIII‐catalyzed C?H activation and cyclopropylation of N‐phenoxylsulfonamides in a highly enantioselective, diastereoselective, and regioselective fashion with cyclopropenyl secondary alcohols as a cyclopropylating reagent. Synthetic applications are demonstrated to highlight the potential of the developed method. Integrated experimental and computational mechanistic studies revealed that the reaction proceeds via a RhV nitrenoid intermediate, and Noyori‐type outer sphere concerted proton‐hydride transfer from the secondary alcohol to the Rh=N bond produces the observed trans selectivity. 相似文献
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M. N. Elinson . K. Feducovich T. A. Zaimovskaya A. N. Vereshchagin G. I. Nikishin 《Russian Chemical Bulletin》2005,54(3):673-677
Electrolysis of aromatic aldehydes and malononitrile in alcohols in an undivided cell in the presence of a NaBr-NaOAc mediatory system stereoselectively gave bicyclic compounds containing the cyclopropane and pyrroline fragments in 60 to 70% yields. In the bicyclic products, the benzene and pyrroline rings are on different sides of the cyclopropane ring.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 663–667, March, 2005. 相似文献
74.
Stabilization of a Chiral Dirhodium Carbene by Encapsulation and a Discussion of the Stereochemical Implications
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Dr. Christophe Werlé Dr. Richard Goddard Petra Philipps Dr. Christophe Farès Prof. Alois Fürstner 《Angewandte Chemie (International ed. in English)》2016,55(36):10760-10765
For the first time, the stereochemical course of an asymmetric cyclopropanation can be discussed on the basis of experimental structural information on a pertinent chiral dirhodium carbene intermediate. Key to success was the formation of racemic single crystals of a heterochiral [Rh2{(S*)‐PTTL}4{=C(Ar)COOMe}][Rh2{(R*)‐PTTL}4] (Ar=MeOC6H4; PTTL=N‐phthaloyl‐tert‐leucinate) capsule, which has been characterized by X‐ray diffraction. NMR spectroscopic data confirm that the obtained structural portrait is also relevant in solution and provide additional information about the dynamics of this species. The chiral binding pocket is primarily defined by the conformational preferences of the N‐phthaloyl‐protected amino acid ligands and reinforced by a network of weak interligand interactions that get stronger when chlorinated phthalimide residues are used. 相似文献
75.
A stereoselective route to enantiomerically enriched bicyclic cyclopropane derivatives 13 is described which is based on a conceptually novel 1,2-chirality transfer approach. The hyperconjugative interaction of an electronically excited carbonyl group with the sigma* orbital of an adjacent C--X bond in the transition state of a hydrogen abstraction causes the preference of a certain conformation and consequently the differentiation between two diastereotopic methylene groups. The 1,2-chirality transfer is completed by a subsequent HX elimination which destroys the only stereogenic center in the reactants 12. Furthermore, it was found that contrary enthalpic and entropic influences result in the existence of an inversion temperature T 0. Upon crossing T 0 the stereoselectivity is reversed. Considering this temperature dependency, chirality transfer efficiencies of up to 83 % could be achieved. The absolute configuration of most products could be unambiguously determined by VCD spectroscopy combined with DFT calculations. 相似文献
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77.
Mechanism‐Driven Elaboration of an Enantioselective Bromocyclopropanation Reaction of Allylic Alcohols
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Sylvain Taillemaud Nicolas Diercxsens Prof. Alexandre Gagnon Prof. André B. Charette 《Angewandte Chemie (International ed. in English)》2015,54(47):14108-14112
A stereoselective bromocyclopropanation of allylic alcohols using dibromomethylzinc bromide is described. Spectroscopic studies to monitor the formation of transient intermediates not only led to the development of a more‐atom‐economical halocyclopropanation reaction, but also highlighted the unique role of ether additives in the process. The desired bromo‐substituted cyclopropanes were isolated in high yields and excellent diastereo‐ as well as enantioselectivities using readily available reagents. 相似文献
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Olalla Barreiro-Costa Gabriela Morales-Noboa Patricio Rojas-Silva Eliana Lara-Barba Javier Santamaría-Aguirre Natalia Bailn-Moscoso Juan Carlos Romero-Benavides Ana Herrera Cristina Cueva Lenin Ron-Garrido Ana Poveda Jorge Heredia-Moya 《Molecules (Basel, Switzerland)》2021,26(16)
This work focuses on the search and development of drugs that may become new alternatives to the commercial drugs currently available for treatment of leishmaniasis. We have designed and synthesized 12 derivatives of bis(spiropyrazolone)cyclopropanes. We then characterized their potential application in therapeutic use. For this, the in vitro biological activities against three eukaryotic models—S. cerevisiae, five cancer cell lines, and the parasite L. mexicana—were evaluated. In addition, cytotoxicity against non-cancerous mammalian cells has been evaluated and other properties of interest have been characterized, such as genotoxicity, antioxidant properties and, in silico predictive adsorption, distribution, metabolism, and excretion (ADME). The results that we present here represent a first screening, indicating two derivatives of bis(spiropyrazolone)cyclopropanes as good candidates for the treatment of leishmaniasis. They have good specificity against parasites with respect to mammalian cells. 相似文献