1. Dynamic structural change of the self-assembled lanthanum complex induced by lithium triflate for direct catalytic asymmetric aldol-Tishchenko reaction
- Author
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Masakatsu Shibasaki, Yoshihisa Sei, Vijay Gnanadesikan, Takashi Ohshima, Kosuke Katagiri, Kentaro Yamaguchi, Yoshihiro Horiuchi, and Hyuma Masu
- Subjects
Models, Molecular ,Spectrometry, Mass, Electrospray Ionization ,Magnetic Resonance Spectroscopy ,Molecular Structure ,Organic Chemistry ,Enantioselective synthesis ,chemistry.chemical_element ,General Chemistry ,Carbon-13 NMR ,Lithium ,Photochemistry ,Crystallography, X-Ray ,Catalysis ,chemistry.chemical_compound ,chemistry ,Propiophenone ,Aldol–Tishchenko reaction ,Lanthanum ,Polymer chemistry ,Reactivity (chemistry) ,Trifluoromethanesulfonate - Abstract
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 [LaLi 3 (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 1 3 C NMR 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 [La 2 Li 4 (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.
- Published
- 2005