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1.
Rhodium(II)‐Catalyzed Intramolecular Cycloisomerizations of Methylenecyclopropanes with N‐Sulfonyl 1,2,3‐Triazoles 下载免费PDF全文
Kai Chen Zi‐Zhong Zhu Yong‐Sheng Zhang Dr. Xiang‐Ying Tang Prof. Min Shi 《Angewandte Chemie (International ed. in English)》2014,53(26):6645-6649
A novel rhodium(II)‐catalyzed tandem cycloisomerization of methylenecyclopropanes (MCPs) with N‐sulfonyl 1,2,3‐triazoles is disclosed. The reaction produces a series of highly functionalized polycyclic N heterocycles via a rhodium imino carbene intermediate. A distinct feature of this divergent synthesis is that different types of substrates control the reaction pathways. Moreover, several interesting transformations of these products to construct diazabicyclo[3.2.1]octane derivatives are also reported. 相似文献
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Hans Joachim Breunig Roland Rsler Enno Lork 《Angewandte Chemie (International ed. in English)》1998,37(22):3175-3177
Surprisingly facile at low temperatures is the synthesis of the first cyclobismuthanes 1 and 2 [Eq. (1)]. In solution 1 and 2 are in equilibrium. The four-membered ring 2 forms black crystals, which were structurally analyzed. At room temperature the rings decompose to elemental bismuth and R3Bi. R=(Me3Si)2CH. 相似文献
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Highly Diastereoselective and Enantioselective Olefin Cyclopropanation Using Engineered Myoglobin‐Based Catalysts 下载免费PDF全文
Dr. Melanie Bordeaux Dr. Vikas Tyagi Prof. Dr. Rudi Fasan 《Angewandte Chemie (International ed. in English)》2015,54(6):1744-1748
Using rational design, an engineered myoglobin‐based catalyst capable of catalyzing the cyclopropanation of aryl‐substituted olefins with catalytic proficiency (up to 46 800 turnovers) and excellent diastereo‐ and enantioselectivity (98–99.9 %) was developed. This transformation could be carried out in the presence of up to 20 g L?1 olefin substrate with no loss in diastereo‐ and/or enantioselectivity. Mutagenesis and mechanistic studies support a cyclopropanation mechanism mediated by an electrophilic, heme‐bound carbene species and a model is provided to rationalize the stereopreference of the protein catalyst. This work shows that myoglobin constitutes a promising and robust scaffold for the development of biocatalysts with carbene‐transfer reactivity. 相似文献
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Inside Back Cover: Highly Diastereoselective and Enantioselective Olefin Cyclopropanation Using Engineered Myoglobin‐Based Catalysts (Angew. Chem. Int. Ed. 6/2015) 下载免费PDF全文
Dr. Melanie Bordeaux Dr. Vikas Tyagi Prof. Dr. Rudi Fasan 《Angewandte Chemie (International ed. in English)》2015,54(6):1975-1975
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Zeynep Güven Lars Denker Hadi Dolati Daniela Wullschläger Dr. Bartosz Trzaskowski Dr. René Frank 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(32):e202200673
Donor-acceptor cyclopropanes or cyclobutanes are dipolar reagents, which are widely used in the synthesis of complex organic (hetero)cycles in ring expansion reactions. Applying this concept to boron containing heterocycles, the four-membered borete cyclo-iPr2N-BC10H6 reacted with the carbon donor ligands 2,6-xylylisonitrile and the carbene IMes :C(NMesCH)2 with ring expansion and ring fusion, respectively. In particular, the tetracyclic structure formed with IMes displays zwitterionic character and absorption in the visible region. In contrast to the carbene IMes, the heavier carbenoids :Si(NDippCH)2 and :Ga(AmIm) with a two-coordinate donor atom afford spiro-type bicyclic compounds, which display four-coordinate geometry at silicon or gallium. (TD-)DFT calculations provide deeper insight into the mechanism of formation and the absorption properties of these new compounds. 相似文献
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Sheng Feng Prof. Fanyang Mo Dr. Ying Xia Zhenxing Liu Zhen Liu Prof. Yan Zhang Prof. Jianbo Wang 《Angewandte Chemie (International ed. in English)》2016,55(49):15401-15405
The rhodium(I)‐catalyzed C?C bond activation reaction of siloxyvinylcyclopropanes with diazoesters demonstrates a novel mode of C?C bond cleavage of siloxyvinvylcyclopanes. The alkene products were obtained as single E‐configured isomers in good yields. A σ,η3‐allyl rhodium complex, which has been previously proposed as the key intermediate in rhodium(I)‐catalyzed cycloaddition of vinylcyclopropanes, has been isolated and characterized by X‐ray crystallography. 相似文献
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Helge Willner Friedhelm Aubke 《Angewandte Chemie (International ed. in English)》1997,36(22):2402-2425
Homoleptic carbonyl cations of the electron-rich metals in Groups 8 through 12 are the newest members of the large family of transition metal carbonyls. They can be distinguished from typical metal carbonyl complexes in several respects. Their synthesis entails carbonylation of metal salts in such superacids as fluorosulfuric acid and “magic acid” HSO3F? SbF5. Thermally stable salts with [Sb2F11]? as counterion are obtained with antimony pentafluoride as reaction medium. Both the [Sb2F11]? anion and superacid reaction media have previously found little application in the organometallic chemistry of d-block elements. Also unprecedented in metal carbonyl chemistry are the coordination geometries with coordination numbers 4 (square-planar coordination) and 2 (linear coordination) for the cation. Formal oxidation states of the metals, and the charges of the complex cations, extend from + 1 to +3: thus CO is largely σ-bonded to the metal, and the CO bond is strongly polarized. Minimal metal → CO π-backbonding and a positive partial charge on carbon are manifested in long M? C bonds, short C? O bonds, high frequencies for C? O stretching vibrations (up to 2300 cm?1), and small 13C NMR chemical shifts (up to δc, = 121). Prominent examples of these unusual homoleptic carbonyl cations, which were recently the subject of a Highlight in this journal, include the first carbonyl cation of a p-block metal [Hg(CO)2]2+, the first trivalent carbonyl cation [Ir(CO)6]3+, and the first multiply charged carbonyl cation of a 3d metal [Fe(CO)6]2+. In this overview we propose to (a) outline the historical origins of cationic metal carbonyls and their methods of synthesis; (b) present a summary of the general field of carbonyl cations, which has developed over a yery short period of time; (c) discuss the structural and spectroscopic characteritics of metal–CO bonding; (d) discuss the special significance associated with reaction media and the [Sb2F11]? anion; and (e) point to the most recent results and anticipated future developments. 相似文献
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Jan Keuter Alexander Hepp Christian Mück‐Lichtenfeld Felicitas Lips 《Angewandte Chemie (International ed. in English)》2019,58(13):4395-4399
Reaction of the bicyclo[1.1.0]tetrasilatetraamide Si4{N(SiMe3)Dipp}4 1 (Dipp=2,6‐diisopropylphenyl) with 5 equiv of the N‐heterocyclic carbene NHCMe4 (1,3,4,5‐tetramethylimidazol‐2‐ylidene) affords a bifunctional carbene‐coordinated four‐membered‐ring compound with a Si=N group and a two‐coordinate silicon atom Si4{N(SiMe3)Dipp}2(NHCMe4)2(NDipp) 2 . When 2 reacts with 0.25 equiv sulfur (S8), two sulfur atoms add to the divalent silicon atom in plane and perpendicular to the plane of the Si4 ring, which confirms the silylone character of the two‐coordinate silicon atom in 2 . 相似文献
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Malcolm H. Chisholm David L. Clark Mark J. Hampden-Smith David H. Hoffman 《Angewandte Chemie (International ed. in English)》1989,28(4):432-444
Alkoxide and carbonyl ligands complement each other because they both behave as “π buffers” to transition metals. Alkoxides, which are π donors, stabilize early transition metals in high oxidation states by donating electrons into vacant dπ orbitals, whereas carbonyls, which are π acceptors, stabilize later transition elements in their lower oxidation states by accepting electrons from filled dπ orbitals. Both ligands readily form bridges that span M? M bonds. In solution fluxional processes that involve bridge–terminal ligand exchange are common to both alkoxide and carbonyl ligands. The fragments [W(OR)3], [CpW(CO)2], [Co(CO)3], and CH are related by the isolobal analogy. Thus the compounds [(RO)3W ? W(OR)3], [Cp(CO)2W?W(CO)2Cp], hypothetical [(CO)3Co?Co(CO)3], and HC?CH are isolobal. Alkoxide and carbonyl cluster compounds often exhibit striking similarities with respect to substrate binding—e.g., [W3(μ3-CR)(OR′)9] versus [Co3(μ3-CR)(CO)9] and [W4(C)(NMe)(OiPr)12] versus [Fe4(C)(CO)13]—but differ with respect to M? M bonding. The carbonyl clusters use eg-type orbitals for M? M bonding whereas the alkoxide clusters employ t2g-type orbitals. Another point of difference involves electronic saturation. In general, each metal atom in a metal carbonyl cluster has an 18-electron count; thus, activation of the cluster often requires thermal or photochemical CO expulsion or M? M bond homolysis. Alkoxide clusters, on the other hand, behave as electronically unsaturated species because the π electrons are ligand-centered and the LUMO metal-centered. Also, access to the metal centers may be sterically controlled in metal alkoxide clusters by choice of alkoxide groups whereas ancillary ligands such as tertiary phosphanes or cyclopentadienes must be introduced if steric factors are to be modified in carbonyl clusters. A comparison of the reactivity of alkynes and ethylene with dinuclear alkoxide and carbonyl compounds is presented. For the carbonyl compounds CO ligand loss is a prerequisite for substrate uptake and subsequent activation. For [M2(OR)6] compounds (M = Mo and W) the nature of substrate uptake and activation is dependent upon the choice of M and R, leading to a more diverse chemistry. 相似文献
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Liu R Zhang M Wyche TP Winston-McPherson GN Bugni TS Tang W 《Angewandte Chemie (International ed. in English)》2012,51(30):7503-7506
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Borst ML van der Riet N Lemmens RH de Kanter FJ Schakel M Ehlers AW Mills AM Lutz M Spek AL Lammertsma K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3631-3642
The synthesis of highly strained bicyclic phosphirane and phosphirene iron-tetracarbonyl complexes, that is, complexes with 2-aza-1-phosphabicyclo[n.1.0]alkanes and -alkenes (n = 3-5), is explored by using intramolecular cycloaddition of an in situ generated electrophilic phosphinidene complex, [R(iPr)NP=Fe(CO)(4)], to its C=C- and C[triple chemical bond]C-containing R substituent. Saturated bicyclic complexes 7 a-c with n = 4-2 are remarkably stable, as illustrated by the X-ray crystal structure for 7 b (n=3), yet all readily undergo retroaddition to react with phenylacetylene. Shuttling of the phosphinidene iron complex between two equivalent C=C groups is demonstrated for a 1-butene-substituted 2-aza-1-phosphabicyclo[3.1.0]hexane by selective (1)H NMR magnetization transfer from the phosphirane protons to the olefinic protons. Even the more strained unsaturated bicycles 17 a,b (n = 4,3) are surprisingly stable as illustrated by the X-ray crystal structure for 17 a (n = 4), but the smaller phosphabicyclo[3.1.0]hex-5-ene (17 c, n = 2) dimerizes to tricyclic 19 with a unique ten-membered heterocyclic ring; an X-ray crystal structure is reported. Like their saturated analogues also the bicyclic phosphirenes readily undergo retroaddition as shown by the reaction of their phosphinidene iron moiety with phenylacetylene. 相似文献
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Masaaki Ichinohe Tadahiro Matsuno Akira Sekiguchi 《Angewandte Chemie (International ed. in English)》1999,38(15):2194-2196
Red-orange crystals of cyclotrisilene 3 were obtained by the reaction of the dibromotrisilane 1 and the tribromodisilane 2 with sodium in toluene [Eq. (1)]. The X-ray crystal structure of 3 shows that the three-membered ring is almost an isosceles triangle and has a twisted Si−Si double bond with a length of 2.138(2) Å. 相似文献
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Many papers have been published on the analysis of metal cations by capillary electrophoresis (CE), for example, lanthanide, transition metal, alkali, and alkaline earth metal ions. Separations of metal ions are based on the differences in their electrophoretic mobilities. Since most 相似文献
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Two new thioantimonates [M(dap)3]Sb4S7 (M = Ni2+ ( 1 ) and Co2+ ( 2 )) were synthesized under solvothermal conditions by the reaction of NiS (or Co metal), Sb and S in an aqueous solution of 1,2‐diaminopropane (dap). Compounds 1 and 2 are isostructural. The polymeric [Sb4S72?]n anion is composed of two SbS3 trigonal pyramids and two SbS4 units. The SbS3 and SbS4 units are interconnected by corners and edges to build a 2‐D puckered layer with Sb4S4 and Sb16S16 heterorings. The apertures of the large Sb16S16 hetero‐rings are filled by two [M(dap)3]2+ complex cations which serve as template ions. The band gaps of 2.44 eV for 1 and 2.43 eV for 2 have been estimated from optical absorption spectra. 相似文献
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