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首页> 外文期刊>Chemistry: A European journal >An Improved Catalyst System for the Iron-Catalyzed Intermolecular Ring-Expansion Reactions of Epoxides
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An Improved Catalyst System for the Iron-Catalyzed Intermolecular Ring-Expansion Reactions of Epoxides

机译：铁催化的环氧化物分子间扩环反应的改进催化剂体系

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A considerable improvement is reported in the iron-catalyzed ring-expansion reactions of epoxides gener ating tetrahydrofuran derivatives by formal insertion of an alkene.Optimi zation of the catalyst system revealed that a preformed[Fe(salen)]complex minimizes the formation of polymeri zation side-products so that increased yields of intermolecular reactions were obtained.However,more importantly,the scope of the reaction could also be enlarged considerably.The iron-cata lyzed ring-expansion reaction can now be applied to some styrene oxide deriv atives,acting as radical donors,as well as to a wide variety of acceptor-substi tuted acyclic alkenes and cyclic dienes that act as radical acceptors.The use of unsymmetrical radical acceptors led to interesting questions concerning the re-giochemistry of the reactions.The con servation of the stereochemistry of the starting materials in the products was investigated through a study of the re actions of E-and Z-configured accept or-substituted double bonds.The reac tions of fumaric and maleic esters were performed and the ratios of diastereo-meric and regioisomeric products were determined.
机译：据报道，通过烯烃的正式插入，在铁催化的生成四氢呋喃衍生物的环氧化物的环催化扩环反应中有显着改进。催化剂体系的优化表明，预先形成的[Fe（salen）]络合物可最大程度地减少聚合反应的形成。副产物，从而提高了分子间反应的产率。但是，更重要的是，反应的范围也可以大大扩大。铁催化的扩环反应现在可以用于某些苯乙烯氧化物衍生物，作为自由基供体，以及各种各样的取代基的无环烯烃和环状二烯充当自由基受体。不对称自由基受体的使用引起了有关反应的重新血管化学的有趣问题。通过研究E和Z构型的接受或替代物的反应，研究了产品中起始原料的立体化学进行富马酸酯和马来酸酯的反应，并确定非对映异构和区域异构产物的比例。

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