期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 11, 期 18, 页码 5195-5204出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200500442
关键词
aldol-Tishchenko reaction; asymmetric catalysis; lanthanum; self-assembly
The development of a direct catalytic asymmetric aldol-Tishchenko reaction and the nature of its catalyst are described. An aldol-Tishchenko reaction of various propiophenone derivatives with aromatic aldehydes was promoted by [LaLi3(binol)(3)] (LLB), and reactivity and enantioselectivity were dramatically enhanced by the addition of lithium trifluoromethanesulfonate (LiOTf). First, we observed a dynamic structural change of LLB by the addition of LiOTf using (CN)-C-13 MR spectroscopy, electronspray ionization mass spectrometry (ESI-MS), and cold-spray ionization mass spectrometry (CSI-MS). X-ray crystallography revealed that the structure of the newly generated self-assembled complex was a binuclear [La2Li4,(binaphthoxide)(5)] complex 6. A reverse structural change of complex 6 to LLB by the addition of one equivalent of Li-2(binol) was also confirmed by ESI-MS and experimental results. The drastic concentration effects on the direct catalytic asymmetric aldol-Tishchenko reaction suggested that the addition of LiOTf to LLB generated an active oligomeric catalyst species.
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