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Dynamic Structural Change of the Self‐Assembled Lanthanum Complex Induced by Lithium Triflate for Direct Catalytic Asymmetric Aldol–Tishchenko Reaction
Author(s) -
Horiuchi Yoshihiro,
Gnanadesikan Vijay,
Ohshima Takashi,
Masu Hyuma,
Katagiri Kosuke,
Sei Yoshihisa,
Yamaguchi Kentaro,
Shibasaki Masakatsu
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500442
Subject(s) - aldol reaction , trifluoromethanesulfonate , chemistry , catalysis , lithium (medication) , mass spectrometry , organic chemistry , medicine , chromatography , endocrinology
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.