An efficient and flexible synthesis of a new class of chiral bifunctional NHC catalyst has been reported. These new imidazolylidene NHCs, bearing a (thio)urea function as a hydrogenbonddonor promoted efficiently highly diastereoselective trans‐cyclopentannulation of enals and enones in moderate to good yields (up to 69 % yield) along with excellent enantioselectivity (up to 96 % ee). This methodology
NHC-catalyzed reactions of enals with water as a solvent
作者:Wendy Wen Yi Leong、Xingkuan Chen、Yonggui Robin Chi
DOI:10.1039/c3gc40397a
日期:——
Water is demonstrated as a suitable solvent for NHC-catalyzed reactions of enals. The use of D2O as a solvent allows for the effective incorporation of deuterium isotopes into organic molecules.
Cooperative <i>N</i>-Heterocyclic Carbene/Lewis Acid Catalysis for Highly Stereoselective Annulation Reactions with Homoenolates
作者:Benoit Cardinal-David、Dustin E. A. Raup、Karl A. Scheidt
DOI:10.1021/ja910666n
日期:2010.4.21
A new approach that takes advantage of N-heterocyclic carbene/Lewis acidcooperativecatalysis provides access to cis-1,3,4-trisubstituted cyclopentenes from enals and chalcone derivatives with high levels of diastereoselectivity and enantioselectivity. The presence of Ti(OiPr)(4) as the Lewis acid allows for efficient substrate preorganization, which translates into high levels of diastereoselectivity
A Method for the Analysis of Free Carbenes Present after NHC-Organocatalyzed Transformations
作者:Tamal Kanti Das、Akkattu T. Biju
DOI:10.1002/ejoc.201700903
日期:2017.8.17
A systematic analysis of free N-heterocyclic carbenes (NHCs) present in the reaction flask after NHC-organocatalyzed reactions has been performed by treating the reaction mixture with elemental sulfur and isolating and analyzing the formed thiourea/thione derivatives.
Design, Synthesis, and Organocatalytic Activity of N-Heterocyclic Carbenes Functionalized with Hydrogen-Bond Donors in Enantioselective Reactions of Homoenolates
imidazolinium salts functionalized with urea-type hydrogen-bonddonor moieties has been prepared from the chiral pool. The corresponding N-heterocycliccarbenes were evaluated as organocatalysts in three enantioselectivereactions involving homoenolate intermediates generated from enals. The catalysts proved competent in enantioselective cyclopentannulation and γ-lactonization reactions, a premiere for