Liu Han, Lu Shao-Feng, Xu Jiaxi, Du Da-Ming
Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Chem Asian J. 2008 Jul 7;3(7):1111-21. doi: 10.1002/asia.200800071.
The asymmetric Friedel-Crafts alkylation of electron-rich N-containing heterocycles with nitroalkenes under catalysis of diphenylamine-tethered bis(oxazoline) and bis(thiazoline)-Zn(II) complexes was investigated. In the reaction of indole derivatives, the complex of ligand 4 f with trans-diphenyl substitutions afforded better results than previously published ligand 4 e with cis-diphenyl substitutions. Excellent yields (up to greater than 99 %) and enantioselectivities (up to 97 %) were achieved in most cases. The complex of ligand 4 d bearing tert-butyl groups gave the best results in the reactions of pyrrole. Moderate to good yields (up to 91 %) and enantioselectivities (up to 91 %) were achieved in most cases. The origin of the enantioselectivity was attributed to the NH-pi interaction between the catalyst and the incoming aromatic system in the transition state. Such an interaction was confirmed through comparison of the enantioselectivity and the absolute configuration of the products in the reactions catalyzed by designed ligands.
研究了在二苯胺连接的双（恶唑啉）和双（噻唑啉）-锌（II）配合物催化下，富电子含氮杂环与硝基烯烃的不对称傅克烷基化反应。在吲哚衍生物的反应中，具有反式二苯基取代的配体4f的配合物比先前报道的具有顺式二苯基取代的配体4e给出了更好的结果。在大多数情况下，获得了优异的产率（高达99%以上）和对映选择性（高达97%）。带有叔丁基的配体4d的配合物在吡咯的反应中给出了最好的结果。在大多数情况下，获得了中等至良好的产率（高达91%）和对映选择性（高达91%）。对映选择性的起源归因于过渡态中催化剂与进入的芳族体系之间的NH-π相互作用。通过比较设计配体催化反应中产物的对映选择性和绝对构型，证实了这种相互作用。
