Department of Chemistry, Brock University , St. Catharines, Ontario, Canada L2S 3A1.
J Org Chem. 2013 Oct 18;78(20):10288-97. doi: 10.1021/jo401665n. Epub 2013 Oct 1.
The origin of the enantioselectivity in the Cu(R,R)-Ph-box2-catalyzed intramolecular aminooxygenation of N-sulfonyl-2-allylanilines and 4-pentenylsulfonamides to afford chiral indolines and pyrrolidines, respectively, was investigated using density functional theory (DFT) calculations. The pyrrolidine-forming transition-state model for the major enantiomer involves a chairlike seven-membered cyclization transition state with a distorted square-planar copper center, while the transition-state model for the minor enantiomer was found to have a boatlike cyclization geometry having a distorted tetrahedral geometry about the copper center. Similar copper-geometry trends were observed in the chiral indoline-forming reactions. These models were found to be qualitatively consistent with experimental results and allow for rationalization of how substitution on the substrate backbone and N-sulfonyl substituent affect the level of enantioselectivity in these and related copper(II)-catalyzed enantioselective reactions.
使用密度泛函理论（DFT）计算研究了 Cu(R,R)-Ph-box2 催化的 N-磺酰基-2-烯丙基苯胺和 4-戊烯基磺酰胺的分子内氨氧化反应中对映选择性的起源，分别得到手性吲哚啉和吡咯烷。对于主要对映异构体的吡咯烷形成过渡态模型，涉及一个扭曲的四面体形铜中心的椅式七元环化过渡态，而对于次要对映异构体的过渡态模型，则发现具有扭曲的四面体形铜中心的船式环化几何形状。在手性吲哚啉形成反应中观察到类似的铜几何趋势。这些模型与实验结果定性一致，并允许对底物骨架和 N-磺酰基取代基的取代如何影响这些和相关的铜（II）催化对映选择性反应中的对映选择性水平进行合理化。
