Synthesis of 2,3-Dihydrothiazolo[3,2-a]pyrimidin-5-ones by a Michael-type Tandem Reaction |
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Authors: | Yvonne Syha Charlene Valmalle Jan W. Bats Michael Kock Mona Abdel-Tawab Manfred Schubert-Zsilavecz |
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Affiliation: | Institut für Pharmazeutische Chemie/ZAFES, Universit?t Frankfurt am Main, Frankfurt am Main, Germany Ecole Normale Supérieure de Lyon (ENS Lyon), Lyon Cedex 07, France Institut für Organische Chemie, Universit?t Frankfurt am Main, Frankfurt am Main, Germany Phenion GmbH & Co. KG, Frankfurt am Main, Germany Zentrallaboratorium Deutscher Apotheker, Eschborn, Germany
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Abstract: | Summary. Although various thiazoles are known in literature for their biological and pharmacological properties only a few multi-step synthesis pathways for the preparation of thiazolo[3,2-a]pyrimidinones have been reported, which are tedious and time-consuming. An alternative synthesis pathway is described, which allows the preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones in a one-step process based on a Michael-type tandem reaction. By heating of 2-thiobarbituric acid with ethyl 4-bromocrotonate in ethanol at 60°C for 2 h, a 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was obtained in 73% yield, whereas carrying out the reaction at room temperature results in the formation of an unstable unsaturated ester. The structures of both, the α,β-unsaturated ester as well as the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one were confirmed by NMR spectroscopy. Additionally, the structure of the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was investigated by single-crystal X-ray analysis. The described approach offers a significant improvement over previously reported synthesis pathways because it allows the simple preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones with good yields in a one-step reaction. |
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Keywords: | . Cyclization 2,3-Dihydrothiazolo[3,2-a]pyrimidin-5-ones Michael-type tandem reaction. |
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