Mechanistic Studies on a Cu-Catalyzed Asymmetric Allylic Alkylation with Cyclic Racemic Starting Materials
作者:Emeline Rideau、Hengzhi You、Mireia Sidera、Timothy D. W. Claridge、Stephen P. Fletcher
DOI:10.1021/jacs.7b02440
日期:2017.4.19
Mechanisticstudies on Cu-catalyzed asymmetric additions of alkylzirconocene nucleophiles to racemic allylic halide electrophiles were conducted using a combination of isotopic labeling, NMR spectroscopy, kinetic modeling, structure-activity relationships, and new reaction development. Kinetic and dynamic NMR spectroscopic studies provided insight into the oligomeric Cu-ligand complexes, which evolve
结合同位素标记、核磁共振光谱、动力学建模、构效关系和新反应发展,对铜催化的烷基锆茂亲核试剂向外消旋烯丙基卤化物亲电试剂的不对称加成进行了机理研究。动力学和动态 NMR 光谱研究提供了对低聚 Cu-配体配合物的洞察,这些配合物在反应过程中变得更快和更高的对映选择性。Cu 抗衡离子在选择不同途径和通过形成烯丙基碘中间体使起始材料外消旋方面发挥作用。我们量化了 Cu 催化的烯丙基碘异构化的速率,并确定了一系列发生烯丙基碘的形成和外消旋化的条件。我们开发了反应条件,其中外消旋烯丙基磷酸酯是使用新亚磷酰胺配体 D 的合适底物。D 还首次允许对外消旋七元环烯丙基氯进行高度对映选择性加成。使用烯丙基磷酸酯的反应的 1H 和 2H NMR 光谱实验表明烯丙基氯中间体的重要性,这些中间体通过 TMSCl 的作用形成或来自外来的氯源。总的来说,这些研究支持一种机制,即复杂的低聚催化剂既可以使起始材料外消旋,又
Features and Applications of [Rh(CO)<sub>2</sub>Cl]<sub>2</sub>-Catalyzed Alkylations of Unsymmetrical Allylic Substrates
作者:Brandon L. Ashfeld、Kenneth A. Miller、Anna J. Smith、Kristy Tran、Stephen F. Martin
DOI:10.1021/jo701290b
日期:2007.11.1
A novel regio- and stereoselective [Rh(CO)2Cl]2-catalyzed allylic alkylation of unsymmetrical allylic carbonates was discovered. The regioselectivity of the reaction favors product ratios in which substitution occurs at the carbon bearing the leaving group. When an enantiomerically enriched carbonate (≥99% ee) was examined, the Rh(I)-catalyzed allylic alkylation proceeded stereoselectively to provide
Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation
作者:Hengzhi You、Emeline Rideau、Mireia Sidera、Stephen P. Fletcher
DOI:10.1038/nature14089
日期:2015.1.15
remains a key challenge. Here we report a copper-catalysed dynamickineticasymmetrictransformation using racemic substrates and alkyl nucleophiles. These nucleophiles have a pKa of ≥50, more than 25 orders of magnitude more basic than the nucleophiles that are typically used in such transformations. Organometallic reagents are generated in situ from alkenes by hydrometallation and give highly enantioenriched