Asymmetric Catalytic Hydrogenations of Chiral α-Keto Amides

Abstract
Asymmetric catalytic hydrogenations of chiral pyruvamides were carried out using palladium on charcoal (Pd-C) as a catalyst to give lactamides with the diastereoisomeric purities (d.p.) of up to 62%. It was found that there was a linear correlation between the d.p. and the dielectric constant of the solvents used in the hydrogenations of chiral pyruvamides. The results were explained by employing the chelation model and the adsorption of the phenyl group in the substrate molecule on the catalyst. The temperature effect on the d.p. of the product was also examined. The catalytic hydrogenations of chiral benzoylformamides were also performed to give low d.p. presumably, the chelation complexes of the substrates could not take a predominant conformation with the catalyst.

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