Enantioselective amination of nitroolefins under base-free and water-rich conditions using chiral bifunctional phase-transfer catalysts
作者:Junchao Zhu、Dongxiao Cui、Yuedan Li、Jingxu He、Weiping Chen、Pingan Wang
DOI:10.1039/c8ob00583d
日期:——
The direct enantioselective amination of nitroolefins has been performed with L-tert-leucine-derived squaramide-scaffold bifunctional phase-transfer catalysts under base-free and water-rich conditions with low catalyst loading (0.5–1 mol%) to provide 2-aminonitroalkanes in good yields (up to 96%) and enantioselectivities (up to 93% ee).
Asymmetric Neutral Amination of Nitroolefins Catalyzed by Chiral Bifunctional Ammonium Salts in Water-Rich Biphasic Solvent
作者:Lijia Wang、Seiji Shirakawa、Keiji Maruoka
DOI:10.1002/anie.201101307
日期:2011.5.27
It′s just a phase: Environmentally benign title reaction was achieved under neutral phase‐transfer conditions in the presence of 0.05 mol % of a chiral bifunctional ammonium bromide. The importance of bifunctional design of the chiral phase‐transfer catalysts (PTC) was clearly shown in the transition‐state model of the reaction based on the single‐crystal X‐ray structure. Bn=benzyl, Boc=tert‐butoxycarbonyl
phase‐transfer reaction system can be applied to highly enantioselectiveconjugateaddition and aldol reactions under the influence of chiral bifunctional ammonium bromides as key catalysts. The structure of the chiral ammonium enolate intermediate is discussed based on the single‐crystal X‐ray structures of relevant ammonium salts and the importance of bifunctional design of catalyst is clearly explained in the