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.
An efficient diastereo- and enantioselective [3 + 2] cycloaddition of heterosubstituted alkenes with oxiranes via selective C–C bond cleavage of epoxides has been developed. The reaction was catalyzed by a chiral N,N′-dioxide/Ni(II) catalyst, and a variety of chiral highly substituted tetrahydrofurans were obtained in up to 99% yield, 92/8 dr, and 99% ee.
Catalytic Asymmetric Michael Addition/Cyclization of Isothiocyanato Oxindoles: Highly Efficient and Versatile Approach for the Synthesis of 3,2′-Pyrrolidinyl Mono- and Bi-spirooxindole Frameworks
作者:Yi-Ming Cao、Fang-Fang Shen、Fu-Ting Zhang、Rui Wang
DOI:10.1002/chem.201204114
日期:2013.1.21
A‐spiro‐ing to greatness: The catalytic asymmetric Michael addition/cyclization of isothiocyanato oxindoles has been realized. This versatile approach provides an easy and highly efficient way to access not only the enantioselective synthesis of 3,2′‐pyrrolidinyl spirooxindole frameworks, but also the construction of enatiomerically enriched bi‐spirooxindoles containingthreecontiguous stereocenters
Regioselective
<scp>aza‐Michael</scp>
additions of
<scp>2‐arylidene</scp>
‐1,3‐diphenylpropan‐1,3‐diones with isatins: Synthesis of
<scp>N‐diketone</scp>
‐functionalized isatins
作者:Ya Cheng、Zheng Li
DOI:10.1002/jhet.4075
日期:2020.10
The efficient aza‐Michaeladditions of isatins to 2‐arylidene‐1,3‐diphenylpropan‐1,3‐diones at room temperature in the presence of cesium carbonate are described. The salient features of this protocol are no transition‐metal catalysts, mild conditions, high regioselectivity, high atom economy, satisfactory yield and simple work‐up procedures.