| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1345904 | Tetrahedron: Asymmetry | 2013 | 6 Pages |
Currently, asymmetric synthesis represents one of the main streams of organic synthesis. Although an extensive research has been carried out in this area, the synthesis of chiral compounds with the required enantiomeric purity is still a challenging issue. Herein, we focus on the preparation of new enantioselective catalysts based on pyridine-imidazolidinones. The substituted 5-benzyl-2-(pyridine-2-yl)imidazolidine-4-ones 5–8 were prepared by condensation of chiral amino acid amides (α-methylDOPA and α-methylphenylalanine) with 2-acetylpyridine and pyridine-2-carbaldehyde. The individual isomers of the described ligands 5–8 were separated chromatographically. The copper(II) complexes of these chiral ligands were studied as enantioselective catalysts for the asymmetric Henry reaction of substituted aldehydes with nitromethane or nitroethane. The ligands containing a methyl group at the 2-position of the imidazolidinone ring 6a and 8a exhibit a high degree of enantioselectivity (up to 91% ee). The nitroaldols derived from nitroethane (2-nitropropan-1-ols) were obtained with a comparable enantiomeric purity to derivatives of 2-nitroethanol. This group of ligands represents a new and promising class of enantioselective catalysts, which deserve further attention.
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(2S)-2-[(tert-Butoxycarbonyl)amino]-2-methyl-3-phenylpropanoic acidC15H21NO4[α]D20=-28.0 (c 1, CH3OH)Source of chirality: Asymmetric synthesis—resolution via diastereomersAbsolute configuration: (S)
(2S)-2-[(tert-Butoxycarbonyl)amino]-2-methyl-3-(3,4-dimethoxyphenyl)propanoic acidC17H25NO6[α]D20=-14.7 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPAAbsolute configuration: (S)
(2S)-2-[(tert-Butoxycarbonyl)amino]-2-methyl-3-phenylpropanamideC15H22N2O3[α]D20=-50.3 (c 1, CH3OH)Source of chirality: Asymmetric synthesis—resolution via diastereomersAbsolute configuration: (S)
(2S)-2-[(tert-Butoxycarbonyl)amino]-2-methyl-3-(3,4-dimethoxyphenyl)propanamideC17H26N2O5[α]D20=-44.1 (c 0.9, CH3OH)Source of chirality: (S)-α-methylDOPAAbsolute configuration: (S)
(2S)-2-Amino-2-methyl-3-phenylpropanamideC10H14N2O[α]D20=-33.0 (c 1.1, CH3OH)Source of chirality: Asymmetric synthesis—resolution via diastereomersAbsolute configuration: (S)
(2S)-2-Amino-2-methyl-3-(3,4-dimethoxyphenyl)propanamideC12H18N2O3[α]D20=-22.7 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPAAbsolute configuration: (S)
(2R,5S)-5-Benzyl-5-methyl-2-(pyridine-2-yl)imidazolidine-4-oneC16H17N3O[α]D20=-38.5 (c 1, CH3OH)Source of chirality: Asymmetric synthesis, chromatographic separationAbsolute configuration: (2R,5S)
(2S,5S)-5-Benzyl-5-methyl-2-(pyridine-2-yl)imidazolidine-4-oneC16H17N3O[α]D20=+30.5 (c 1, CH3OH)Source of chirality: Asymmetric synthesis, chromatographic separationAbsolute configuration: (2S,5S)
(2R,5S)-5-(3,4-Dimethoxybenzyl)-5-methyl-2-(pyridine-2-yl)imidazolidine-4-oneC18H21N3O3[α]D20=+79.9 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPA, chromatographic separationAbsolute configuration: (2R,5S)
(2S,5S)-5-(3,4-Dimethoxybenzyl)-5-methyl-2-(pyridine-2-yl)imidazolidine-4-oneC18H21N3O3[α]D20=-111.4 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPA, chromatographic separationAbsolute configuration: (2S,5S)
(2R,5S)-5-Benzyl-2,5-dimethyl-2-(pyridine-2-yl)imidazolidine-4-oneC17H19N3O[α]D20=-21.7 (c 1, CH3OH)Source of chirality: Asymmetric synthesis, chromatographic separationAbsolute configuration: (2R,5S)
(2S,5S)-5-Benzyl-2,5-dimethyl-2-(pyridine-2-yl)imidazolidine-4-oneC17H19N3O[α]D20=-147.0 (c 1, CH3OH)Source of chirality: Asymmetric synthesis, chromatographic separationAbsolute configuration: (2S,5S)
(2R,5S)-5-(3,4-Dimethoxybenzyl)-2,5-dimethyl-2-(pyridine-2-yl)imidazolidine-4-oneC19H23N3O3[α]D20=-3.3 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPA, chromatographic separationAbsolute configuration: (2R,5S)
(2S,5S)-5-(3,4-Dimethoxybenzyl)-2,5-dimethyl-2-(pyridine-2-yl)imidazolidine-4-oneC19H23N3O3[α]D20=-42.9 (c 1, CH3OH)Source of chirality: (S)-α-methylDOPA, chromatographic separationAbsolute configuration: (2S,5S)
