Highly enantioselective direct vinylogous Michael addition of γ-substituted deconjugated butenolides to maleimides catalyzed by chiral squaramides
作者:Yun-Long Guo、Li-Na Jia、Lin Peng、Liang-Wen Qi、Jing Zhou、Fang Tian、Xiao-Ying Xu、Li-Xin Wang
DOI:10.1039/c3ra43344g
日期:——
Highly enantioselectivedirectvinylogousMichael reactions of γ-aryl-substituted deconjugated butenolides with maleimides, catalyzed by only 1 mol% bifunctional squaramides derived from cinchona alkaloids, were achieved with excellent yields (up to 96%) and enantioselectivities (up to 97% ee). This protocol features a very low catalyst loading, mild reaction conditions and provides a potential and
99:1) and high diastereoselectivities (dr up to >20:1). DirectasymmetricvinylogousMichael reactions of γ-aryl-substituted deconjugatedbutenolides with nitroolefins and N-phenylmaleimide are described using bifunctional thiourea derivatives as the catalyst. The resulting butenolide derivatives containing adjacent quaternary and tertiary stereocenters are obtained in good yields (54–90%) and with excellent