Highly Enantioselective Conjugate Addition of Malononitrile to 2-Enoylpyridines with Bifunctional Organocatalyst
作者:Nagaraju Molleti、Nirmal K. Rana、Vinod K. Singh
DOI:10.1021/ol3015607
日期:2012.9.7
An efficient enantioselective conjugate addition of malononitrile to a range of β-substituted 2-enoylpyridines catalyzed by cinchonaalkaloid-based bifunctional urea catalysts has been developed. Both enantiomers of the products could be achieved with the same level of enantioselectivity by using pseudoenantiomeric catalysts in up to 97% ee and in excellent yields. One of the enantioenriched products
Enantioselective La<sup>III</sup>-pyBOX-Catalyzed Nitro-Michael Addition to (<i>E</i>)-2-Azachalcones
作者:Gonzalo Blay、Celia Incerti、M. Carmen Muñoz、José R. Pedro
DOI:10.1002/ejoc.201201579
日期:2013.3
[La(OTf)3] complex with a new pyBOX ligand bearing a bulky 1-naphthylmethyl substituent at the 4′-position of the oxazoline ring catalyzes the conjugate addition of nitroalkanes to a broad range of (E)-2-azachalcones, providing the expected nitro-Michael products with good yields and enantiomeric excesses up to 87 %. The optical purity of the products can be increased by a single crystallization. A plausible
Reinvestigation of synthesis of halo-substituted 3-phenyl-1-(2-pyridyl)-2-propen-1-ones (azachalcones). A tandem reaction for formation of penta-substituted cyclohexanols
作者:Chia-Wai Li、Tzu-Hsuan Shen、Tzenge-Lien Shih
DOI:10.1016/j.tet.2017.06.033
日期:2017.8
During the reaction course, we obtained not only the target azachalcones, but also penta-substituted cyclohexanols, which are seldom reported in the literatures. The formation of penta-substituted cyclohexanols was dependent on equivalents of base used and reaction time. Their formation followed a tandem reaction: Claisen-Schmidt condensation, three Michael reactions, retro-aldol reaction, and intramolecular
Cinchona alkaloid derived squaramide catalyzed diastereo- and enantioselective Michael addition of isocyanoacetates to 2-enoylpyridines
作者:Mei-Xin Zhao、Guang-Yu Zhu、Xiao-Li Zhao、Min Shi
DOI:10.1016/j.tet.2019.01.024
日期:2019.3
An efficient organocatalytic diastereo- and enantioselective Michael addition of α-substituted isocyanoacetates to 2-enoylpyridines catalyzed by cinchona alkaloid-derived squaramide has been achieved, affording the corresponding adducts with two adjacent tertiary-quaternary stereocenters in excellent yields (up to 99%) and good to excellent stereoselectivities (up to >20:1 dr, up to 98% ee) under mild