- Enantioselective [3+2] annulation of isatin-derived MBH-carbonates and 3-nitroindoles enabled by a bifunctional DMAP-thiourea
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A highly enantioselective [3+2] annulation of isatin-derived Morita-Baylis-Hillman (MBH) carbonates and 3-nitroindoles was enabled by a chiral DMAP-thiourea bifunctional catalyst, affording the corresponding polycyclic spirooxindoles bearing three consecutive stereocenters with good to excellent yields and enantioselectivities. Transformations of the annulation product were subsequently elaborated and the preliminary biological assays demonstrated that these artificial spirooxindoles potentially inhibited pancreatic lipase in a dose-dependent manner.
- Gao, Dingding,Ge, Guangbo,Hu, Qing,Li, Qing-Hua,Lin, Guo-Qiang,Mei, Ming-Shun,Shi, Da-Yu,Tian, Ping,Wang, Yu-Hui
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- Stereodivergent Synthesis of Tetrahydrofuroindoles through Pd-Catalyzed Asymmetric Dearomative Formal [3+2] Cycloaddition
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A stereodivergent synthesis of tetrahydrofuroindoles through palladium-catalyzed asymmetric dearomative formal [3+2] cycloaddition of nitroindoles with epoxybutenes was developed. The polarity of the solvent was found to play a key role in the diastereoselectivity. In toluene, good to excellent yields (70–99 %), diastereoselectivity (87/13->95/5 d.r.), and enantioselectivity (85/15–94/6 e.r.) were obtained, regardless of the properties of the substituents on nitroindoles. In acetonitrile, tetrahydrofuroindoles of a different diastereoisomer were produced with good to excellent yields (75–98 %) and stereoselectivity (78/22–93/7 d.r., 93/7–99/1 e.r.). Mechanistic studies were conducted to illustrate the origin of the diastereodivergency. The kinetic experiments indicate that the rate-determining step of this reaction is different in different solvents. ESI-MS experiments also support the existence of key palladium complex intermediates and the catalytic cycle of the reaction.
- Cheng, Qiang,Zhang, Fang,Cai, Yue,Guo, Yin-Long,You, Shu-Li
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p. 2134 - 2138
(2018/02/06)
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