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Article: On the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions

TitleOn the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions
Authors
Issue Date2007
PublisherWiley - V C H Verlag GmbH & Co KGaA. The Journal's web site is located at http://www.wiley-vch.de/home/chemistry
Citation
Chemistry - A European Journal, 2007, v. 13 n. 23, p. 6724-6731 How to Cite?
AbstractAn investigation into the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions by using density functional theory (DFT) methods is reported. Previous work suggested that this type of cyclopropanation reaction may proceed by competition between a methylene-transfer mechanism and a carbometalation mechanism. In this paper, it is demonstrated that the intramolecular cyclopropanation reactions promoted by chiral carbenoids 1 and 2 proceed by the methylene-transfer mechanism. The carbometalation mechanism was found to have a much higher reaction barrier and does not appear to compete with the methylenetransfer mechanism. The Lewis base group does not enhance the carbometalation pathway enough to compete with the methylene-transfer pathway. The present computational results are consistent with experimental observations for these cyclopropanation reactions. The factors governing the stereochemistry of the intramolecular cyclopropanation reaction by the methylene-transfer mechanism were examined to help elucidate the origin of the stereoselectivity observed in experiments. Both the directing group and the configuration at the C 1 centre were found to play a key role in the stereochemistry. Carbenoid 1 has a chiral C 1 centre of R configuration. The Lewis base group directs the cyclization of carbenoid 1 to form a single product. In contrast, the Lewis base group cannot direct the cyclization of carbenoid 2 to furnish a stereoselective product due to the S configuration of the chiral C 1 centre in carbenoid 2. This relationship of the stereochemistry to the chiral character of the carbenoid has implications for the design of new efficient carbenoid reagents for stereoselective cyclopropanation. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
Persistent Identifierhttp://hdl.handle.net/10722/168133
ISSN
2015 Impact Factor: 5.771
2015 SCImago Journal Rankings: 2.323
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorKe, Zen_US
dc.contributor.authorZhou, Yen_US
dc.contributor.authorGao, Hen_US
dc.contributor.authorZhao, Cen_US
dc.contributor.authorPhillips, DLen_US
dc.date.accessioned2012-10-08T03:15:29Z-
dc.date.available2012-10-08T03:15:29Z-
dc.date.issued2007en_US
dc.identifier.citationChemistry - A European Journal, 2007, v. 13 n. 23, p. 6724-6731en_US
dc.identifier.issn0947-6539en_US
dc.identifier.urihttp://hdl.handle.net/10722/168133-
dc.description.abstractAn investigation into the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions by using density functional theory (DFT) methods is reported. Previous work suggested that this type of cyclopropanation reaction may proceed by competition between a methylene-transfer mechanism and a carbometalation mechanism. In this paper, it is demonstrated that the intramolecular cyclopropanation reactions promoted by chiral carbenoids 1 and 2 proceed by the methylene-transfer mechanism. The carbometalation mechanism was found to have a much higher reaction barrier and does not appear to compete with the methylenetransfer mechanism. The Lewis base group does not enhance the carbometalation pathway enough to compete with the methylene-transfer pathway. The present computational results are consistent with experimental observations for these cyclopropanation reactions. The factors governing the stereochemistry of the intramolecular cyclopropanation reaction by the methylene-transfer mechanism were examined to help elucidate the origin of the stereoselectivity observed in experiments. Both the directing group and the configuration at the C 1 centre were found to play a key role in the stereochemistry. Carbenoid 1 has a chiral C 1 centre of R configuration. The Lewis base group directs the cyclization of carbenoid 1 to form a single product. In contrast, the Lewis base group cannot direct the cyclization of carbenoid 2 to furnish a stereoselective product due to the S configuration of the chiral C 1 centre in carbenoid 2. This relationship of the stereochemistry to the chiral character of the carbenoid has implications for the design of new efficient carbenoid reagents for stereoselective cyclopropanation. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.en_US
dc.languageengen_US
dc.publisherWiley - V C H Verlag GmbH & Co KGaA. The Journal's web site is located at http://www.wiley-vch.de/home/chemistryen_US
dc.relation.ispartofChemistry - A European Journalen_US
dc.subject.meshCyclopropanes - Chemistryen_US
dc.subject.meshHydrocarbons - Chemistryen_US
dc.subject.meshLithium - Chemistryen_US
dc.subject.meshMethane - Analogs & Derivatives - Chemistryen_US
dc.subject.meshMolecular Conformationen_US
dc.subject.meshThermodynamicsen_US
dc.titleOn the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactionsen_US
dc.typeArticleen_US
dc.identifier.emailPhillips, DL:phillips@hku.hken_US
dc.identifier.authorityPhillips, DL=rp00770en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1002/chem.200700145en_US
dc.identifier.pmid17508383-
dc.identifier.scopuseid_2-s2.0-34547773279en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-34547773279&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume13en_US
dc.identifier.issue23en_US
dc.identifier.spage6724en_US
dc.identifier.epage6731en_US
dc.identifier.isiWOS:000248710700022-
dc.publisher.placeGermanyen_US
dc.identifier.scopusauthoridKe, Z=14048262500en_US
dc.identifier.scopusauthoridZhou, Y=16835391600en_US
dc.identifier.scopusauthoridGao, H=36666205500en_US
dc.identifier.scopusauthoridZhao, C=7403563836en_US
dc.identifier.scopusauthoridPhillips, DL=7404519365en_US

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