Asymmetric Hydrogenation with Iridium C,N and N,P Ligand Complexes: Characterization of Dihydride Intermediates with a Coordinated Alkene
作者:Stefan Gruber、Andreas Pfaltz
DOI:10.1002/anie.201309515
日期:2014.2.10
Previously elusive iridium dihydride alkene complexes have been identified and characterized by NMR spectroscopy in solution. Reactivity studies demonstrated that these complexes are catalytically competent intermediates. Additional H2 is required to convert the catalyst‐bound alkene into the hydrogenation product, supporting an IrIII/IrV cycle via an [IrIII(H)2(alkene)(H2)(L)]+ intermediate, as originally
以前难以捉摸的二氢化铱铱烯烃配合物已通过溶液中的NMR光谱进行了鉴定和表征。反应性研究表明,这些络合物是催化活性的中间体。需要额外的H 2才能将与催化剂结合的烯烃转化为加氢产物,从而通过[Ir III(H)2(烯烃)(H 2)(L)] +来支持Ir III / Ir V循环中间,如最初基于DFT计算所建议的。NMR分析表明,反应路径是通过快速平衡同分异构的二氢化烯烃中间体而进行的,随后是缓慢的对映选择性确定步骤。如在用二膦酸铑催化剂进行不对称氢化的经典实例中一样,它是一种次要的,不稳定的中间体,可转化为主要产物对映异构体。
Synthesis of isotopically labeled tri-p-tolylamine
作者:Brian D. Kesling、Bj�rn C. S�derberg、Terry Gullion
Three isotopically labeled tri-p-tolylamines, 15N, 15N2D27, and mono-13CH3 have been prepared using zeolite mediated bromination or nitration of toluenes as one of the key steps. The obtained-4-nitrotoluenes were reduced to 4-aminotoluenes, and coupled, via a palladium catalyzed amination reaction, with 4-bromotoluenes to afford di- and tri-p-tolylamines. The di-p-tolylamines were readily transformed
Structure and dynamics of intramolecular hydrogen bonds in carboxylic acid dimers: A solid state NMR study
作者:B. H. Meier、F. Graf、R. R. Ernst
DOI:10.1063/1.443045
日期:1982.1.15
Direct evidence for dynamic intramolecular double proton exchange in carboxylic acid dimers in the solid is obtained from NMR measurements. For the p-toluic acid dimer, an asymmetric double minimum potential with an energy difference ΔG = 1.0 kJ/mol and an activation energy of Ea = 4.8 kJ/mol between the two tautomeric forms is found. The equilibrium position of the carboxylic proton pair at low temperature is derived from the corresponding dipolar coupling tensor. The importance of double proton tunneling at low temperature is discussed.
DEUTERIUM-ENRICHED VALSARTAN
申请人:Czarnik Anthony W.
公开号:US20080299218A1
公开(公告)日:2008-12-04
The present application describes deuterium-enriched valsartan, pharmaceutically acceptable salt forms thereof, and methods of treating using the same.
A Simple Route to Strong Carbon-13 NMR Signals Detectable for Several Minutes
作者:Soumya S. Roy、Philip Norcott、Peter J. Rayner、Gary G. R. Green、Simon B. Duckett
DOI:10.1002/chem.201702767
日期:2017.8.4
Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) suffer from low sensitivity and limited nuclear spin memory lifetimes. Although hyperpolarization techniques increase sensitivity, there is also a desire to increase relaxation times to expand the range of applications addressable by these methods. Here, we demonstrate a route to create hyperpolarized magnetization in 13 C nuclear
核磁共振 (NMR) 和磁共振成像 (MRI) 的灵敏度较低且核自旋记忆寿命有限。尽管超极化技术提高了灵敏度,但还希望增加弛豫时间以扩大这些方法可寻址的应用范围。在这里,我们展示了一种在 13 C 核自旋对中产生超极化磁化的途径,通过以单线态存储,该磁化的持续时间比正常寿命长得多。通过将分子设计和低场存储与仲氢衍生的超极化相结合,我们实现了相对于平衡塞曼极化的超过三个数量级的信号放大以及状态寿命的一个数量级的延长。这些研究使用了一系列专门合成的哒嗪衍生物,其中二甲基对甲苯基苯基哒嗪是最成功的,在低场中实现了约 190 秒的寿命,从而产生了 10 分钟可见的 13 C 信号。