Dynamic Structural Change of the Self-Assembled Lanthanum Complex Induced by Lithium Triflate for Direct Catalytic Asymmetric Aldol–Tishchenko Reaction
✍ Scribed by Yoshihiro Horiuchi; Vijay Gnanadesikan; Takashi Ohshima; Hyuma Masu; Kosuke Katagiri; Yoshihisa Sei; Kentaro Yamaguchi; Masakatsu Shibasaki
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 457 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
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 ^13^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.