Journal
ADVANCED SYNTHESIS & CATALYSIS
Volume 356, Issue 10, Pages 2330-2336Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adsc.201300964
Keywords
asymmetric catalysis; Cinchona alkaloids; nitroolefins; organocatalysis; pyrazolinones; vinylogous Michael addition
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Funding
- Universita degli Studi di Parma
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While several protocols exist for the asymmetric functionalization of pyrazolinones at the a-position relying on nucleophilic addition or annulation procedures, use of alpha-alkylidene electronrich analogues in asymmetric vinylogous coupling to carbon electrophiles is substantially an uncharted domain. We now report, for the first time, that alkylidenepyrazolinones carrying an enolizable carbon at the gamma-position efficiently participate in direct and asymmetric, catalytic vinylogous Michael- type additions to nitroolefins providing the expected adducts in high yields, with complete gamma-site selectivity and with extraordinary levels of enantio-, diastereo-, and geometrical selectivities. Both enantiomeric adducts were equally accessed by employing a quasi-enantiomeric quinine- or quinidine-based thiourea catalyst pair.
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