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Organocatalytic asymmetric conjugate addition to allenic esters and ketones.
J Am Chem Soc. 2008 Apr 09; 130(14):4897-905.JA

Abstract

The first example of an organocatalytic enantioselective conjugate addition of cyclic beta-ketoesters and glycine imine derivatives to electron-deficient allenes is described. We disclose that the corresponding chiral beta,gamma-unsaturated carbonyl compounds are formed exclusively under phase-transfer conditions using either cinchona-alkaloid-derived or biphenyl-based chiral quaternary ammonium salts as catalysts. The scope of the reaction for beta-ketoesters is outlined for allenes having a ketone or ester motif as electron-withdrawing group as well as different substituents in the 3-position, giving the optically active products in high yields and excellent diastereo- and enantioselectivities (90-96% ee). The conjugate addition also proceeds for a number of cyclic beta-ketoesters having different ring sizes, ring systems, and substituents in high yields and enantioselectivities. Glycine imine derivatives also undergo the asymmetric conjugate addition to electron-deficient allenes in high yields and with enantioselectivities in the range of 60-88% ee, thus providing a rapid entry to optically active alpha-vinyl-substituted alpha-amino acid derivatives. It is shown that the enantioselectivity is strongly dependent on the size of the ester moiety of the nucleophile in combination with the catalytic system used. The high synthetic value of the chiral products arising from these new catalytic processes is demonstrated by two straightforward transformations leading in one case to optically active hexahydrobenzopyranones and in the other to substituted pyroglutamates (gamma-lactames).

Authors+Show Affiliations

Danish National Research Foundation, Center for Catalysis, Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

18341345

Citation

Elsner, Petteri, et al. "Organocatalytic Asymmetric Conjugate Addition to Allenic Esters and Ketones." Journal of the American Chemical Society, vol. 130, no. 14, 2008, pp. 4897-905.
Elsner P, Bernardi L, Dela Salla G, et al. Organocatalytic asymmetric conjugate addition to allenic esters and ketones. J Am Chem Soc. 2008;130(14):4897-905.
Elsner, P., Bernardi, L., Dela Salla, G., Overgaard, J., & Jørgensen, K. A. (2008). Organocatalytic asymmetric conjugate addition to allenic esters and ketones. Journal of the American Chemical Society, 130(14), 4897-905. https://doi.org/10.1021/ja710689c
Elsner P, et al. Organocatalytic Asymmetric Conjugate Addition to Allenic Esters and Ketones. J Am Chem Soc. 2008 Apr 9;130(14):4897-905. PubMed PMID: 18341345.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Organocatalytic asymmetric conjugate addition to allenic esters and ketones. AU - Elsner,Petteri, AU - Bernardi,Luca, AU - Dela Salla,Giorgio, AU - Overgaard,Jacob, AU - Jørgensen,Karl Anker, Y1 - 2008/03/15/ PY - 2008/3/18/pubmed PY - 2008/3/18/medline PY - 2008/3/18/entrez SP - 4897 EP - 905 JF - Journal of the American Chemical Society JO - J Am Chem Soc VL - 130 IS - 14 N2 - The first example of an organocatalytic enantioselective conjugate addition of cyclic beta-ketoesters and glycine imine derivatives to electron-deficient allenes is described. We disclose that the corresponding chiral beta,gamma-unsaturated carbonyl compounds are formed exclusively under phase-transfer conditions using either cinchona-alkaloid-derived or biphenyl-based chiral quaternary ammonium salts as catalysts. The scope of the reaction for beta-ketoesters is outlined for allenes having a ketone or ester motif as electron-withdrawing group as well as different substituents in the 3-position, giving the optically active products in high yields and excellent diastereo- and enantioselectivities (90-96% ee). The conjugate addition also proceeds for a number of cyclic beta-ketoesters having different ring sizes, ring systems, and substituents in high yields and enantioselectivities. Glycine imine derivatives also undergo the asymmetric conjugate addition to electron-deficient allenes in high yields and with enantioselectivities in the range of 60-88% ee, thus providing a rapid entry to optically active alpha-vinyl-substituted alpha-amino acid derivatives. It is shown that the enantioselectivity is strongly dependent on the size of the ester moiety of the nucleophile in combination with the catalytic system used. The high synthetic value of the chiral products arising from these new catalytic processes is demonstrated by two straightforward transformations leading in one case to optically active hexahydrobenzopyranones and in the other to substituted pyroglutamates (gamma-lactames). SN - 1520-5126 UR - https://www.unboundmedicine.com/medline/citation/18341345/Organocatalytic_asymmetric_conjugate_addition_to_allenic_esters_and_ketones_ DB - PRIME DP - Unbound Medicine ER -