Computational analysis of the stereochemical outcome in the imidazolidinone-catalyzed enantioselective (4 + 3)-cycloaddition reaction.
Computational analysis of the stereochemical outcome in the imidazolidinone-catalyzed enantioselective (4 + 3)-cycloaddition reaction.
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DOI：
10.1021/jo501906m
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发表时间：
2015-01
期刊：
影响因子：
--
通讯作者：
E. Krenske;K. Houk;M. Harmata
中科院分区：
文献类型：
--
作者：
E. Krenske;K. Houk;M. Harmata
计算表明，为什么催化，不对称（4 + 3）-环加成反应中开发的Harmata实验室的收益与面部选择性相反，提出了相关的催化Diels-Alder反应的模型。用M06-2X/6-311+G（d，p）//B3 LYP/6- 31 G（d）计算表明，MacMillan手性2-叔丁基-5-苄基咪唑烷酮衍生的亚胺离子与呋喃的（4 + 3）-环加成反应优先发生在较拥挤的面上.苄基的构象重组，以避免与甲硅烷基的分子内相互作用，是负责区分顶面和底面攻击的活化屏障。
Computations show why the catalytic, asymmetric (4 + 3)-cycloaddition reaction developed in the Harmata laboratories proceeds with facial selectivity opposite to that for models proposed for related catalyzed Diels-Alder reactions. Computations with M06-2X/6-311+G(d,p)//B3LYP/6-31G(d) show that iminium ions derived from MacMillan's chiral 2-tert-butyl-5-benzylimidazolidinone and siloxypentadienals undergo (4 + 3)-cycloadditions with furans preferentially on the more crowded face. Conformational reorganization of the benzyl group, to avoid intramolecular interaction with the silyl group, is responsible for differentiating the activation barriers of top- and bottom-face attack.