Belokon YN

Bulychev AG

Godovikov IA

Kataev DA

Lyssenko KA

Mal'fanov IlyaL

Maleev VI

Moskalenko MA

North M

Saveleva TF

Skrupskaya TV

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%). \ua9 2008 Elsevier Ltd. All rights reserved

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

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

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