Baeyer–Villiger rearrangement of a substituted pyrrole by Oxone
作者:Joseph P.Y. Kao、Sukumaran Muralidharan、Peter Y. Zavalij、Steven Fletcher、Fengtian Xue、Gerald M. Rosen
DOI:10.1016/j.tetlet.2014.04.004
日期:2014.5
Pyrroloxyls have been reported to exhibit very narrow EPR spectral lines, essential for in vivo imaging. En route to pyrroloxyls, we observed an unexpected Baeyer–Villiger rearrangement, leading to loss of aromaticity and formation of a 4,5-dihydro-1H-ketopyrrole.
Interaction of Radical Pairs Through-Bond and Through-Space: Scope and Limitations of the Point−Dipole Approximation in Electron Paramagnetic Resonance Spectroscopy
作者:Christoph Riplinger、Joseph P. Y. Kao、Gerald M. Rosen、Velavan Kathirvelu、Gareth R. Eaton、Sandra S. Eaton、Andrei Kutateladze、Frank Neese
DOI:10.1021/ja901150j
日期:2009.7.29
validity of the popular point-dipole approximation for interpretation of the zero-field splitting (ZFS) parameter (D-value) in EPR spectroscopy is studied. This approximation is of central importance for the determination of distances by analysis of EPR data. In this work, a detailed experimental (EPR spectroscopy and X-ray crystallography) and theoretical study for a model system (2,2',5,5'-tetra(tert-butyl)-4
研究了用于解释 EPR 光谱中零场分裂 (ZFS) 参数(D 值)的流行点偶极子近似的有效性。这种近似对于通过分析 EPR 数据确定距离至关重要。在这项工作中,对模型系统 (2,2',5,5'-四(叔丁基)-4,4'-双(乙氧基-羰基)-3,3'-bipyrrolyl-1,1'-dioxyl) 以了解 EPR 光谱中点偶极子模型的范围和局限性。对于这种双自由基,通过点偶极子近似得出的自由基-自由基距离与 X 射线分析得出的结果有很大的偏差(大约 40%)。基于 B3LYP 密度泛函计算的 D 值的显式量子化学计算导致与测量的 D 值具有极好的定量一致性。所采用方法的定量准确性得到了先前已通过实验表征的两个附加系统的确认。因此,我们详细分析了对目标系统 D 值的贡献。这种分析导致深入了解点偶极子近似失败的原因。然后将分析扩展到对五类模型系统的计算机研究。在携带自由基的基团之间引入了不同长度和键饱和度的接头。这允许分析