| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1345231 | Tetrahedron: Asymmetry | 2015 | 6 Pages |
By employing a natural cinchona alkaloid as a catalyst, the enantioselective tandem Michael addition/oxidation of 4-substituted pyrazol-5-ones with p-benzoquinones was realized. The reaction afforded a wide range of 4,4-disubstituted pyrazol-5-ones with moderate to good yields (up to 72%) and moderate to good enantioselectivities (up to 99%).
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2-(4-Ethyl-5-oxo-1,3-diphenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC23H18N2O380% ee[α]D20 = +70.45 (c 0.19, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Allyl-5-oxo-1,3-diphenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC24H18N2O399% ee[α]D20 = +90.5 (c 0.26, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(5-Oxo-1,3-diphenyl-4-(prop-2-yn-1-yl)-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC24H16N2O399% ee[α]D20 = +92.7 (c 0.26, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-5-oxo-1,3-diphenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC28H20N2O392% ee[α]D20 = +92.6 (c 0.26, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-(4-Fluorobenzyl)-5-oxo-1,3-diphenyl-4,5-dihydro-1H pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC28H19FN2O397% ee[α]D20 = +110.9 (c 0.27, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-(4-Methylbenzyl)-5-oxo-1,3-diphenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC29H22N2O366% ee[α]D20 = +70.45 (c 0.19, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-(4-Methoxybenzyl)-5-oxo-1,3-diphenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC29H22N2O469% ee[α]D20 = +34.6 (c 0.28, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(5-Oxo-1,3-diphenyl-4-(thiophen-2-ylmethyl)-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC26H18N2O3S92% ee[α]D20 = +99.1 (c 0.30, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-3-(4-bromophenyl)-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC28H19BrN2O350% ee[α]D20 = +74.8 (c 0.36, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-3-(4-methoxyphenyl)-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC29H22N2O484% ee[α]D20 = +92.95 (c 0.31, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-5-oxo-1-phenyl-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC29H22N2O397% ee[α]D20 = +127.9 (c 0.24, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-3-(naphthalen-1-yl)-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC32H22N2O392% ee[α]D20 = +115.3 (c 0.30, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
2-(4-Benzyl-5-oxo-1-phenyl-3-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-4-yl)cyclohexa-2,5-diene-1,4-dioneC26H18N2O3S84% ee[α]D20 = +86.5 (c 0.12, CH2Cl2)Source of chirality: Asymmetric tandem Michael addition/oxidation processAbsolute configuration: not determined
