Mechanistic Investigations of Cooperative Catalysis in the Enantioselective Fluorination of Epoxides
作者:Julia A. Kalow、Abigail G. Doyle
DOI:10.1021/ja207256s
日期:2011.10.12
studies of the (salen)Co- and amine-cocatalyzed enantioselective ring opening of epoxides by fluoride. The kinetics of the reaction, as determined by in situ (19)F NMR analysis, are characterized by apparent first-order dependence on (salen)Co. Substituent effects, nonlinear effects, and reactivity with a linked (salen)Co catalyst provide evidence for a rate-limiting, bimetallic ring-opening step. To account
本报告描述了(salen)Co 和胺共催化的环氧化物对映选择性开环的机理研究。通过原位 (19)F NMR 分析确定的反应动力学特征在于对 (salen)Co 的明显一级依赖性。取代基效应、非线性效应和与连接的 (salen) Co 催化剂的反应性为限速双金属开环步骤提供了证据。为了解释这些不同的数据,我们提出了一种机制,其中活性亲核氟物质是形成静止状态二聚体的氟化钴。胺助催化剂与 (salen) Co 的轴向连接促进二聚体解离,并且是观察到的协同性的起源。在这些研究的基础上,我们表明在比率、周转次数、氟化物开环反应的底物范围可以通过使用连接的salen框架来实现。报道了将该催化剂系统应用于快速(5 分钟)氟化以生成已知 PET 示踪剂 F-MISO 的未标记类似物。
Polymer-Supported Chiral Co(Salen) Complexes: Synthetic Applications and Mechanistic Investigations in the Hydrolytic Kinetic Resolution of Terminal Epoxides
作者:D. Allen Annis、Eric N. Jacobsen
DOI:10.1021/ja984410n
日期:1999.5.1
corresponding immobilized cobalt derivatives are shown to be efficient and highly enantioselective catalysts for the hydrolytickineticresolution (HKR) of terminal epoxides. These systems provide practical solutions to certain technical difficulties associated with the isolation of reaction products from the HKR. Removal of the supported catalyst by filtration and repeated recycling is demonstrated with no loss
Redox-Activep-Quinone-Based Bis(pyrazol-1-yl)methane Ligands: Synthesis and Coordination Behaviour
作者:Sebastian Scheuermann、Tonia Kretz、Hannes Vitze、Jan W. Bats、Michael Bolte、Hans-Wolfram Lerner、Matthias Wagner
DOI:10.1002/chem.200701615
日期:2008.3.7
ox). An octahedral Ni IIcomplex [trans-Ni(2c)2] and square-planar Pd IIcomplexes [Pd2bCl2] and [Pd2b ox Cl2] have been prepared. In the two Pd II species, the ligands are coordinated only through their pyrazolyl rings. The fact that [Pd2bC12] and [Pd2b oxC12] are isolable compounds proves that redox transitions involving the p-quinone substituent are fully reversible. In [Pd2b oxCl2], the methine