Solution structure of a key intermediate used in asymmetric alkylation reactions. 1H, 1H-NOESY and 6Li, 1H-HOESY studies of mixtures of a chiral lithium amide and n-butyllithium

• Published in: Journal of organometallic chemistry Vol. 489; no. 1; pp. 175 - 179
• Main Authors: Hilmersson, Göran, Davidsson, Öjvind
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.1995
• Subjects: Asymmetric induction; Lithium; Nuclear magnetic resonance; Asymmetric induction; Lithium; Nuclear magnetic resonance
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/0022-328X(94)05157-7

NMR spectroscopy involving 6Li, 1H-HOESY and 6Li, 6Li-COSY studies in combination with 1H, 1H-NOESY has been used to determine the detailed structures of two complexes, are the novel mixed 1 : 1 complex between lithium-(2-methoxy-(R)-1-phenyl-ethyl)-((S)-1-phenyl-ethyl)-amide ( 1) and n-butyllithium, and the other the dimeric complex of 1. Both the mixed dimer between 1 and n-butyllithium and the dimeric complex of 1 were formed when 1 was mixed with n-butyllithium in molar ratio of 1.5:1 in diethyl ether (DEE-d 10) at −80°C. The 6Li NMR spectrum of the solution, containing the complex between 1 and n-butyllithium and the dimer of 1 showed the presence of four 6Li resonances at −80°C, indicative of two non-equivalent lithiums within each complex. The complex between 1 and n-butyllithium is responsible for the asymmetric induction in the alkylation reaction.