- Synthesis of asymmetric iron-pybox complexes and their application to aziridine forming reactions
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The synthesis of a series of iron-pybox complexes and their employment in the catalytic asymmetric aziridine forming reaction is presented. When AgSbF6 is used as an initiator, the i-pr- and t-bu-pybox complexes produce 47% of the cis-aziridine
- Redlich, Mark,Hossain, M. Mahmun
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p. 8987 - 8990
(2007/10/03)
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- An explanation for the apparent cis-aziridine selectivity in the iron Lewis acid-catalyzed reaction of N-benzylidene aniline and ethyl diazoacetate
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The reason for the apparent cis-aziridine selectivity in the reaction of ethyl diazoacetate with N-benzylidene aniline, catalyzed by [(η5-C5H5)(CO)2Fe(THF)] +[BF4]-, is reported. The catalytic reaction produces both cis and trans-aziridines. Once the imine has been consumed, the trans-isomer is shown to undergo a catalytic decomposition, leaving cis-aziridine and by-products. The reaction is graphically profiled to illustrate the relative quantity of reactants and products as a function of time. A new mechanistic model is proposed in order to explain the observed selectivity.
- Mayer, Michael F.,Wang, Qinwei,Hossain, M. Mahmun
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- InCl3 catalyzed reactions of ethyl diazoacetate with aldimines: A highly diastereoselective synthesis of cis-aziridine carboxylates
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InCl3 catalyzed reactions of ethyl diazoacetate with aldimines give aziridine carboxylates under mild conditions, low catalyst loading and with high cis-selectivity. (C) 2000 Elsevier Science Ltd.
- Sengupta,Mondal
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p. 6245 - 6248
(2007/10/03)
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- Aziridine synthesis in protic media by using lanthanide triflates as catalysts
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Ln(OTf)3-catalyzed aziridine synthesis from imines and diazo compounds was studied in a variety of protic media. The reactions proceeded readily under mild conditions and were highly selective, affording predominantly cis aziridines. The imines used were typically those derived from aromatic aldehydes and aromatic amines, with either electron-donating or electron- withdrawing substituents. N-benzyl aryl aldimines and imines derived from aromatic amines and hindered aliphatic aldehydes were also found to work well. Among the three diazo compounds examined, ethyl diazoacetate (EDA) and 3-nitrophenyl diazomethane were effective reagents for the aziridination. However, the reactions of ethyl diazoacetoacetate failed to give any desired product. Six lanthanides triflates as well as Sc(OTf)3 and Y(OTf)3 were tested as catalyst in the aziridination reaction. The formation of the by- products was also discussed.
- Xie, Wenhua,Fang, Jianwen,Li, Jun,Wang, Peng George
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p. 12929 - 12938
(2007/10/03)
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- Catalytic formation of aziridines from imines. Characterisation of an intermediate in SnCl4-catalysed aziridination and mechanistic considerations
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The tin(IV) catalysed aziridination of imines using ethyl diazoacetate as the carbene fragment donor has been investigated from a synthetic and mechanistic point of view. For imines substituted with aromatic substituents, an intermediate in the aziridination reaction has been isolated and characterised by X-ray diffraction. This intermediate is an octahedral complex with a trans coordination of two imines and in which the imines have isomerised from trans to cis by the reaction with/coordination to tin(iv). Tin(IV) is a very effective catalyst for the aziridination of various imines giving cis-aziridines as the major product. The aziridination can proceed with a very low catalyst load as 0.05 mol% of SnCl4 is sufficient to achieve a high conversion. For the formation of aziridines a linear plot of the experimental data is obtained by means of the Hammett equation for a series of competition experiments. Based on the results the mechanism for the aziridination is discussed in terms of a Lewis acid activation of the imine for a nucleophilic attack of ethyl diazoacetate.
- Rasmussen, Kaare G.,Juhl, Karsten,Hazell, Rita G.,Jorgensen, Karl Anker
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p. 1347 - 1350
(2007/10/03)
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- Facile synthesis of aziridines from imines and diazoesters or aldehydes, amines, and diazoesters using a catalytic amount of lanthanide triflate
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In the presence of a catalytic amount of lanthanide triflate (Ln(OTf)3), imines reacted with ethyl diazoester in hexane at room temperature to afford the corresponding aziridines in high yields with high diastereoselectivities. Based on these r
- Nagayama, Satoshi,Kobayashi, Shu
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p. 685 - 686
(2007/10/03)
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- Metal-catalysed reactions of imines with ethyl diazoacetate leading to aziridines
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The metal-catalysed aziridination of imines with ethyl diazoacetate as the carbene fragment donor using various Lewis acids as the catalyst has been investigated. The catalytic properties of different Lewis acid complexes have been tested and it has been found that both main-group complexes, such as BF3·OEt2, early- and late-transition metal complexes, such as TiCl2(O-Pr1)2, Cu(OTf)2 and Zn(OTf)2 and rare-earth metal complexes, such as Yb(OTf)3, can catalyse the formation of aziridines. The aziridination gives mainly the cis-aziridines as the major diastereoisomer, but the selectivity is dependent on the substrate, catalyst and solvent. Zn(OTf)2 and Yb(OTf)3 have been shown to be general catalysts for the formation of various aziridines using different imines and a variety of reaction conditions. Both Zn(OTf)2 and Yb(OTf)3, as well as some of the other Lewis acids, in combination with various chiral ligands, have been tested as catalysts for the formation of optically active aziridines, but only low ees are obtained. The Zn(OTf)2- and Yb(OTf)3-catalysed reactions have been investigated for imines having both electron-donating and -withdrawing substituents, and in reactions containing diethyl fumarate as a trapping reagent, in attempts to obtain insight into the mechanism of the aziridination.
- Rasmussen, Kaare G.,Jorgensen, Karl Anker
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p. 1287 - 1291
(2007/10/03)
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- Organic reactions catalyzed by methylrhenium trioxide: Reactions of ethyl diazoacetate and organic azides
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Methylrhenium trioxide (CH3ReO3 or MTO) catalyzes several classes of reactions of ethyl diazoacetate, EDA. It is the first high valent oxo complex for carbene transfer. Under mild conditions and in the absence of other substrates, EDA was converted to a 9:1 mixture of diethyl maleate and diethyl fumarate. In the presence of alcohols, α-alkoxy ethyl acetates were obtained in good yield. The yields dropped for the larger and more branched alcohols, the balance of material being diethyl maleate and fumarate. An electron-donating group in the para position of phenols favors the formation of α-phenoxy ethyl acetates. The use of EDA to form α-thio ethyl acetates and N-substituted glycine ethyl esters, on the other hand, is hardly affected by the size or structure of the parent thiol or amine, with all of these reactions proceeding in high yield. MTO-catalyzed cycloaddition reactions occur between EDA and aromatic imines, olefins, and carbonyl compounds. Three-membered ring products are formed: aziridines, cyclopropanes, and epoxides, respectively. The reactions favor the formation of trans products, and provide a convenient route for the preparation of aziridines. Intermediate carbenoid and nitrenoid species have been proposed. In the presence of an oxygen source such as an epoxide, ethyl diazoacetate and azibenzil are converted to an oxalic acid monoethyl ester and tobenzil; at the same time the epoxide was converted to an olefin. These results provide further support for the proposed intermediate, a cyclic species containing Re, O, and CHCO2Et (or, occasionally, CPhC(O)Ph)in a three-membered ring.
- Zhu, Zuolin,Espenson, James H.
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p. 9901 - 9907
(2007/10/03)
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- Carbenoiduebertragung auf Imine: eine neue asymmetrische katalytische Synthese von Aziridinen
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Stichworte: Asymmetrische Synthesen * Aziridine * Chirale Liganden * Kupferverbindungen
- Hansen, Karl B.,Finney, Nathaniel S.,Jacobsen, Eric N.
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p. 750 - 752
(2007/10/02)
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- Catalytic Formation of Aziridines from Imines and Diazoacetates
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A catalytic method for the preparation of aziridines from imines and diazoacetate is developed using copper complexes as catalyst; the synthetic, diastereo- and enantio-selective scope of the reaction are presented.
- Rasmussen, Kaare G.,Joergensen, Karl Anker
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p. 1401 - 1402
(2007/10/02)
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