Potassium and silver chiral cobaltate(III) complexes as precatalysts for asymmetric C–C bond formation

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• 作者：Yuri N. Belokon ; Viktor I. Maleev ; Dimitri A. Kataev ; Ilya. L. Mal&#x2019 ; fanov ; Alex ; er G. Bulychev ; Margarita A. Moskalenko ; Tat&#x2019 ; yana F. Saveleva ; Tat&#x2019 ; yana V. Skrupskaya ; Konstantin A.
• 关键词：Time&#x2013 ; frequency analysis ; Spectrogram ; Wigner distribution ; Choi&#x2013 ; Williams distribution ; Signal processing
• 刊名：Tetrahedron ; Asymmetry
• 出版年：2008
• 期刊代码：108_09574166
• 类别：ch
• 出版时间：17 April 2008
• 卷：19
• 期：7
• 页码：822-831
• 文件大小：576 K

摘要

Chiral, coordinatively-saturated cobaltate(III) complexes of Schiff bases obtained from salicylaldehyde and the optically active amino acids, (S)-Val, (S)-Thr, and (S)-Trp, are formed as C₂-symmetrical, octahedral, anionic Λ(S,S)-, and Δ(S,S)-diastereoisomeric complexes, which are easily separable by chromatography. The complexes are stereochemically inert and, thus, are not transformed into each other under normal conditions. The counter-cations of the complexes can be easily interchanged and the sodium, potassium, and silver salts of some of the complexes were prepared. The structures of diastereoisomeric Λ-[(Sal-(S)-Val)₂Co(III)]⁻Ag⁺ and Δ-[(Sal-(S)-Val)₂Co(III)]⁻Ag⁺ were established by single crystal X-ray analysis. All of the sodium and potassium complexes effectively catalyzed the reaction between benzaldehyde and Me₃SiCN, but only the Λ-[(Sal-(S)-Trp)₂Co(III)]⁻K⁺ complex gave rise to enantiomerically-enriched mandelonitrile with up to 77%ee. The silver salts catalyzed a Mukaiyama reaction with low enantioselectivity (ee in the range 6–27%).