20247-89-6Relevant academic research and scientific papers
Highly enantioselective and anti -diastereoselective catalytic intermolecular glyoxylate-ene reactions: Effect of the geometrical isomers of alkenes
Zhang, Xiang,Wang, Min,Ding, Ran,Xu, Yun-He,Loh, Teck-Peng
supporting information, p. 2736 - 2739 (2015/06/16)
An efficient method for the synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities via an In(III)-catalyzed intermolecular glyoxylate-ene reaction has been developed. The geometrical isomers of alkenes were shown to have different reactivities. Only the isomers of the alkenes having a proton β-cis to the substituent reacted in this catalytic system.
Bidentate hydroxyalkyl NHC ligands for the copper-catalyzed asymmetric allylic substitution of allyl phosphates with grignard reagents
Magrez, Magaly,Le Guen, Yann,Basle, Olivier,Crevisy, Christophe,Mauduit, Marc
supporting information, p. 1199 - 1203 (2013/02/25)
Demonstrating their potential: Bidentate alkoxy NHC ligands have been used in the copper-catalyzed asymmetric allylic alkylation of allyl phosphates with Grignard reagents (see scheme). The method provides access to tertiary and quaternary chiral centers with high regio- and enantioselectivity. The system is also applied to the synthesis of chiral E,E-dienes, a key structural motif prevalent in natural products. Copyright
β- and γ-disubstituted olefins: Substrates for copper-catalyzed asymmetric allylic substitution
Falciola, Caroline A.,Tissot-Croset, Karine,Reyneri, Hugo,Alexakis, Alexandre
supporting information; scheme or table, p. 1090 - 1100 (2009/05/30)
The copper-catalyzed asymmetric allylic alkylation has shown through many examples that it is a powerful means to generate stereogenic centers with mono β- and γ-substituted olefinic substrates. However, little has been reported about more substituted olefinic patterns, such as β-disubstituted allylic electrophiles. In this paper, we show that a simple procedure using easily accessible Grignard reagents and as low as 3 mol% of copper/ligand can promote high to nearly perfect enantioselectivities (up to >99% ee) with very good γ-selectivities on a wide panel of aliphatic or aromatic β-disubstituted substrates.
Enantioselective protonation of samarium enolates derived from α- heterosubstituted ketones and lactone by SmI2-mediated reduction
Nakamura, Yutaka,Takeuchi, Seiji,Ohgo, Yoshiaki,Yamaoka, Makoto,Yoshida, Akihiro,Mikami, Koichi
, p. 4595 - 4620 (2007/10/03)
SmI2-mediated reductive cleavage of α-heterosubstituents of α-alkyl or α-aryl ketones and lactone gave the corresponding 'thermodynamic samarium enolates'. Enantioselective protonation of the samarium enolates with C2- symmetric chiral diols afforded the corresponding ketones and lactone in moderate to high enantioselectivities.
Anwendungen der Phasentransfer-Katalyse 17. Wittig-Reaktionen in verschiedenen Zweiphasen-Systemen
Dehmlow, Eckehard V.,Barahona-Naranjo, Simon
, p. 1748 - 1762 (2007/10/02)
EINE vergleichende Untersuchung von Wittig-Reaktionen unter Phasentransfer-Katalyse (PTC) bei verschiedenen Bedingungen wurde durchgefuehrt.Es erwies sich als unnoetig, ausser den Phosphoniumsalzen einen PTC-Katalysator zu verwenden.Mechanistische Konsequenzen dieses Befundes werden diskutiert.Als ein besonders geeignetes Basensystem stellte sich Kalium-tert-butoxid in Benzol heraus.Erstmals gelang die Umzetzung von Ketonen und aliphatischen Aldehyden.Einige sehr hohe Literaturausbeuten von PTC-Wittig-Reaktionen konnten unter praeparativen Bedingungen nicht reproduziert werden.
