Asymmetric Synthesis of Spiropyrazolones through Phosphine-Catalyzed [4+1] Annulation
An enantioselective synthesis of spiropyrazolones from allenoate‐derived MBH acetates and pyrazolones through a phosphine‐mediated [4+1] annulation process has been developed. Spiropyrazolones were readily prepared in good chemical yields and good to high enantioselectivities. This is the first asym...
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Veröffentlicht in: | Angewandte Chemie International Edition 2014-05, Vol.53 (22), p.5643-5647 |
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Sprache: | eng |
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Zusammenfassung: | An enantioselective synthesis of spiropyrazolones from allenoate‐derived MBH acetates and pyrazolones through a phosphine‐mediated [4+1] annulation process has been developed. Spiropyrazolones were readily prepared in good chemical yields and good to high enantioselectivities. This is the first asymmetric example in which α‐substituted allenoates were utilized as a C4 synthon for phosphine‐catalyzed [4+1] annulation.
Optically enriched 4‐spiro‐5‐pyrazolones were prepared through phosphine‐catalyzed enantioselective [4+1] annulation. In this study, substituted pyrazolones were used as a C1 synthon in cycloaddition for the first time. Moreover, this is the first report in which α‐substituted allenoates were utilized in an asymmetric [4+1] annulation. |
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ISSN: | 1433-7851 1521-3773 |
DOI: | 10.1002/anie.201311214 |