Enantioselective Stetter Reactions of Enals and Modified Chalcones Catalyzed by N-Heterocyclic Carbenes
作者:Xinqiang Fang、Xingkuan Chen、Hui Lv、Yonggui Robin Chi
DOI:10.1002/anie.201105812
日期:2011.12.2
New trick for an old cat.: Triazolium‐based N‐heterocycliccarbenes (NHCs) catalyze the selective generation of acyl anion equivalents for the title reaction. The stereoelectronic properties of the enal‐derived Breslow intermediates and the unique reactivity of the modified chalcones are crucial for the Stetter reactions to occur. EWG=electron‐ withdrawing group.
β-Functionalization of Carboxylic Anhydrides with β-Alkyl Substituents through Carbene Organocatalysis
作者:Zhichao Jin、Shaojin Chen、Yuhuang Wang、Pengcheng Zheng、Song Yang、Yonggui Robin Chi
DOI:10.1002/anie.201408604
日期:2014.12.1
The first NHC‐catalyzed functionalization of carboxylicanhydrides is described. In this reaction, the β carbon behaves as a nucleophilic carbon and undergoes asymmetric reactions with electrophiles. Anhydrides with challenging β‐alkyl substituents work effectively.
Enantioselective Diels–Alder Reactions of Enals and Alkylidene Diketones Catalyzed by N-Heterocyclic Carbenes
作者:Xinqiang Fang、Xingkuan Chen、Yonggui Robin Chi
DOI:10.1021/ol201917u
日期:2011.9.2
introduced to the α-position of chalcones, and the resulting alkylidene diketones showed new reactivities with enals under the catalysis of N-heterocycliccarbenes (NHCs). Selective activation of enals affords enolate equivalents that undergo highly enantioselective intermolecular Diels–Alder reactions with the alkylidene diketones. No products that might have resulted from typical homoenolate pathways were
Sodium hydride was employed as a Michael donor under the catalysis of PdCl2 for 1,4‐conjugate reductions of α, β‐unsaturatedcarbonylcompounds, which features operational simplicity, mild conditions and high atom‐economy. The merits of NaH as a reductant were demonstrated by the one‐pot or cascade reactions for the syntheses of complex molecules.
Asymmetric epoxidation of 2-arylidene-1,3-diketones: facile access to synthetically useful epoxides
作者:Alessio Russo、Alessandra Lattanzi
DOI:10.1039/c002587a
日期:——
enantioselective epoxidation reaction of acyclic and cyclic 2-arylidene-1,3-diketones is reported. Easily accessible or commercially available α,α-diaryl prolinols as the organocatalysts in the presence of tert-butyl hydroperoxide (TBHP) provide the corresponding epoxides in high to excellent yield (up to 99%) and up to 85% ee (ee >90% after crystallisation). These epoxides are pharmaceutically important