Abstract
Using platform of a new type of chiral Ni(II) complex of glycine Schiff base we designed addition-cyclization reaction cascade to explore aspects of kinetic/thermodynamic formation of the corresponding (S)(2S,3S)/(S)(2S,3R) diastereomers. It was found that the final lactone products reflect the thermodynamic stereocontrol due to much greater rates of the reversible aldol addition vs. subsequent cyclization step. The observed 4/1 (S)(2S,3S)/(S)(2S,3R) diastereoselectivity in the reactions of new type of (S)-Ni(II) complexes constitute an improvement over the previously reported 1.7/1 ratio.
Highlights
Tailor-made amino acids (AAs) [1] are in high demand in modern pharmaceutical industry
Complex (S)-11 has never been used in the aldol additions but showed superior stereocontrolling properties in the alkyl halide alkylation [21] and deracemization of unprotected α- [22] and β-AAs [10]
All the experiments were monitored by thin layer chromatography (TLC) with UV light
Summary
Tailor-made amino acids (AAs) [1] are in high demand in modern pharmaceutical industry. Abstract: Using platform of a new type of chiral Ni(II) complex of glycine Schiff base we designed addition-cyclization reaction cascade to explore aspects of kinetic/thermodynamic formation of the corresponding (S)(2S,3S)/(S)(2S,3R) diastereomers. In a more general version, chiral ligands 1 are transformed to Ni(II) complexes of glycine Schiff bases 2 by the reaction with glycine and source of Ni(II) ions.
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