| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1348572 | Tetrahedron: Asymmetry | 2007 | 6 Pages |
Recoverable (Sa)-BINAM-l-prolinamide in combination with benzoic acid catalyzed the direct aldol reaction between α-chloroacetone and several aldehydes in different solvents, including water. It is possible to obtain mainly one of the isomers with good regio-, diastero-, and enantioselectivity by choosing the appropriate solvent and reaction conditions. Thus, α-chloroacetone mainly gives the anti-aldol isomer in DMF/H2O with up to 97% ee. The crude α-chloro-β-hydroxy ketones obtained are transformed stereospecifically into the corresponding enantioenriched trans-α,β-epoxy ketones derivatives with up to 97% ee through an SN2 displacement reaction by treatment with Et3N.
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trans-(3R,4S)-3,4-Epoxy-4-(4-nitrophenyl)butan-2-oneC10H9NO4Ee = 83% [HPLC: Chiralpak AD column, hexane/iPrOH: 98/21.25 mL/min; ret. times, 43.9 (major), 53.4 (minor) min][α]D20 = −15 (c 1.14, CHCl3)Source of chirality: asymmetric organocatalysisAbsolute configuration: (3R,4S)
trans-(3R,4S)-3,4-Epoxy-4-(2-nitrophenyl)butan-2-oneC10H9NO4Ee = 96% [HPLC: Chiralpak AD column, hexane/iPrOH: 98/21.25 mL/min; ret. times, 19.7 (major), 36.0 (minor) min][α]D20 = −40 (c 1.2, CHCl3)Source of chirality: asymmetric organocatalysisAbsolute configuration: (3R,4S)
trans-(3R,4S)-3,4-Epoxy-4-(3-nitrophenyl)butan-2-oneC10H9NO4Ee = 97% [HPLC: Chiralpak AD column, hexane/iPrOH: 98/21.25 mL/min; ret. times, 25.4 (major), 32.6 (minor) min][α]D20 = −17 (c 1.4, CHCl3)Source of chirality: asymmetric organocatalysisAbsolute configuration: (3R,4S)
trans-(3R,4S)-3,4-Epoxy-4-(4-cyanophenyl)butan-2-oneC11H9NO2Ee = 93% [HPLC: Chiralpak AD column, hexane/iPrOH: 98/21.25 mL/min; ret. times, 32.3 (major), 43.2 (minor) min][α]D20=-50(c0.84,CHCl3)Source of chirality: asymmetric organocatalysis.Absolute configuration: (3R,4S)
trans-(3R,4S)-Epoxy-4-{4-(methoxycarbonyl)phenyl}butan-2-oneC12H12O4Ee = 87% [HPLC: Chiralpak AD column, hexane/iPrOH: 98/21.25 mL/min; ret. times, 9.0 (major), 12.0 (minor) min][α]D20 = −63 (c 0.5, CHCl3)Source of chirality: asymmetric organocatalysisAbsolute configuration: (3R,4S)
