Asymmetric cyclopropanation of chalcones using chiral phase-transfer catalysts

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• 作者：Richard Herchl ; Mario Waser ; ^{Mario.waser@jku.at}
• 关键词：Cyclopropanes ; Organocatalysis ; Phase-transfer catalysis ; Bifunctional ; Cinchona alkaloids
• 刊名：Tetrahedron Letters
• 出版年：2013
• 出版时间：15 May, 2013
• 年：2013
• 卷：54
• 期：20
• 页码：2472-2475
• 全文大小：273 K

文摘

The first phase-transfer catalyzed cyclopropanation reaction of chalcones using bromomalonates as the nucleophiles in a Michael Initiated Ring Closing reaction (MIRC) was developed. Key to success was the use of a free OH-containing cinchona alkaloid ammonium salt catalyst and carefully optimized liquid/liquid reaction conditions. The reaction performed well for electron neutral and electron deficient chalcones giving the products in yields up to 98 % and with enantiomeric ratios up to 91:9.