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By controlling the amount of catalyst 1-methyl-3-(2-(sulfooxy)ethyl)-1H-imidazol-3-ium chloride, two new intermediates of Tröger's bases (11, 1,6-dimethyl-3-(4-methylphenyl)-1,4-dihydroquinazolin-3-ium tetrafluoroborate and 12, 8-methyl-2,5-bis-(4-methylphenyl)-3,5,6,7-tetrahydropyrimido[5,6,1-ij]quinazoline-2-ium tetrafluoroborate) were simply obtained from the one-pot reaction of aromatic amine and formaldehyde in ionic liquid at ambient temperature. These results support the mechanism for Tröger's base formation supposed by Fernando Coelho and co-workers. However, the crystal structure of 12 and correlative quantum chemistry calculation results are not reconciled with their report. 相似文献
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某些含氮有机物光催化氧化产生的自由基中间体 总被引:3,自引:0,他引:3
本文用自旋捕捉技术与ESR相结合的方法研究了某些含氮有机物TiO2光催化降解的过程中形成的活泼中间体.选择的化合物中有丁胺、戊胺、庚胺、六氢吡啶、吡啶、2-甲基吡啶、2,6-二甲基吡啶,这些分子中的氮原子分别作为初级脂肪胺、饱和环中的二级胺以及芳环中的三级胺出现,实验中观察到N-中心自由基及C-中心自由基与自旋捕捉剂加合物的ESR信号,表明这些自由基参与这些化合物光降解的初始过程,对深入了解其光降机理是有意义的. 相似文献
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Rolf Huisgen 《Angewandte Chemie (International ed. in English)》1970,9(10):751-762
Spectroscopic methods have recently been developed that allow the direct detection of reactive intermediates under favorable circumstances. The most general and reliable method, however, is still the indirect one, which makes use of the priciple of kinetic competition; this method is based on the freedom of the intermediate to choose between several reaction possibilities. The following discussion is addressed less to the specialist in reaction mechanisms than to the outsider who wishes to obtain some idea of the value and limitations of the kinetic method. 相似文献
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Dr. Qigang Zhong Dr. Artur Mardyukov Dr. Ephrath Solel Dr. Daniel Ebeling Prof. André Schirmeisen Prof. Peter R. Schreiner 《Angewandte Chemie (International ed. in English)》2023,62(46):e202310121
On-surface synthesis is at the verge of emerging as the method of choice for the generation and visualization of unstable or unconventional molecules, which could not be obtained via traditional synthetic methods. A case in point is the on-surface synthesis of the structurally elusive cyclotriphosphazene (P3N3), an inorganic aromatic analogue of benzene. Here, we report the preparation of this fleetingly existing species on Cu(111) and Au(111) surfaces at 5.2 K through molecular manipulation with unprecedented precision, i.e., voltage pulse-induced sextuple dechlorination of an ultra-small (about 6 Å) hexachlorophosphazene P3N3Cl6 precursor by the tip of a scanning probe microscope. Real-space atomic-level imaging of cyclotriphosphazene reveals its planar D3h-symmetric ring structure. Furthermore, this demasking strategy has been expanded to generate cyclotriphosphazene from a hexaazide precursor P3N21 via a different stimulation method (photolysis) for complementary measurements by matrix isolation infrared and ultraviolet spectroscopy. 相似文献
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K. C. Nicolaou Phil S. Baran Rolf Jautelat Yun He Kin Chiu Fong Ha‐Soon Choi Won Hyung Yoon Yong‐Li Zhong 《Angewandte Chemie (International ed. in English)》1999,38(4):549-552
A seven‐step cascade reaction —in which selective mesylation, epoxide formation, epoxide lysis, cyclization, reiterative oxidation, and nitrogen–oxygen exchange occur sequentially—facilitates the construction of the maleic anhydride moiety of CP molecules 1 and 2 (>93% yield per step). Unstable intermediates of this reaction sequence were detected, providing evidence for the proposed mechanism and resulting in the discovery of a new chemical entity. 相似文献
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Nicola Maggiarosa Wieland Tyrra Dieter Naumann Natalya V. Kirij Yurij L. Yagupolskii 《Angewandte Chemie (International ed. in English)》1999,38(15):2252-2253
The long-postulated reactive intermediates of polar fluoride-inititated trifluoromethylations with Me3SiCF3 (see scheme) were identified by NMR spectroscopy as [Me3Si(CF3)F]− and [Me3Si(CF3)2]−. 相似文献
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Farough Nasiri Morteza Bidar Bahareh Atashkar 《Monatshefte für Chemie / Chemical Monthly》2009,140(4):463-466
Abstract The reaction between dibenzoylacetylene and enol systems, such as acetylaceton or cyclohexane-1,3-dione in the presence of
triphenylphosphine in THF/H2O, leads to 4-acetyl-3-benzoyl-1-phenyl-1,5-hexanedione and 2-hydroxy-3-(2-oxo-2-phenylethyl)-2-phenyl-3,5,6,7-tetrahydro-1-benzofuran-4(2H)-one. Subsequently, these compounds undergo cyclization and elemination reactions in acidic dichloromethane at room temperature
to produce known highly functionalized furan derivatives.
Graphical abstract
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The concept of 1,3-dipolar cycloaddition was developed, starting in the late 1950s, largely by Rolf Huisgen and his students in Munich, and it has led to one of the most versatile methods for the construction of five-membered ring heterocycles. Although first known only as transient intermediates, nitrile imines have been at the heart of mechanistic studies of this type of cycloaddition reactions. Hundreds of mechanistic papers appeared in 1960s and 1970s; reliable spectroscopic observations were achieved in the early 1980s both at low temperatures and in the gas phase; finally, the first crystalline nitrile imine was reported in 1988. The unusual structures found by X-ray analyses as well as the facile rearrangements observed experimentally have fostered a new interplay between experiment and theory. The story of nitrile imines, from matrix characterization to stable compounds, nicely illustrates the role that main group elements can play in organic chemistry. 相似文献