Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters
作者:Chang Won Suh、Tae Hyun Han、Dae Young Kim
DOI:10.5012/bkcs.2013.34.6.1623
日期:2013.6.20
room temperature. As shown in Table 1, Takemoto’s catalyst I and quinine-derived thiourea catalystII effectively promoted the reaction with moderate enantioselectivities (entry 1-2). While both of binaphthyl-modified (thio)urea catalysts III-IV and squaramide organocatalysts V-VI bearing both central and axial chiralities gave high enantioselectivities (entries 3-6). The best result has been obtained
Highly Enantioselective Michael Addition of Cyclic 1,3-Dicarbonyl Compounds to β,γ-Unsaturated α-Keto Esters
作者:Xing-Kuan Chen、Chang-Wu Zheng、Sheng-Li Zhao、Zhuo Chai、Ying-Quan Yang、Gang Zhao、Wei-Guo Cao
DOI:10.1002/adsc.201000045
日期:——
A highlyenantioselectiveMichaeladdition of cyclic 1,3‐dicarbonyl compounds to β,γ‐unsaturated α‐keto esters catalyzed by amino acid‐derived thiourea‐tertiary‐amine catalysts is presented. Using 5 mol% of a novel tyrosine‐derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short