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

Lookup NU author(s): Professor Michael North


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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%). © 2008 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Belokon YN, Maleev VI, Kataev DA, Mal'fanov IlyaL, Bulychev AG, Moskalenko MA, Saveleva TF, Skrupskaya TV, Lyssenko KA, Godovikov IA, North M

Publication type: Article

Publication status: Published

Journal: Tetrahedron: Asymmetry

Year: 2008

Volume: 19

Issue: 7

Pages: 822-831

ISSN (print): 0957-4166

ISSN (electronic): 1362-511X

Publisher: Pergamon


DOI: 10.1016/j.tetasy.2008.03.010


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