corresponding succinimides in good yields and enantioselectivities. DFT calculations support the stereochemical results and the role played by the solvents. Chiralprimary amines containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a pyrimidin-2-yl unit are synthesized and used as general organocatalysts for the Michael reaction of α-branched aldehydes to maleimides. The reaction
N-Primary-amine tetrapeptide-catalyzed highly asymmetric Michael addition of aliphatic aldehydes to maleimides
作者:Zhi-Hong Du、Wen-Juan Qin、Bao-Xiu Tao、Meng Yuan、Chao-Shan Da
DOI:10.1039/d0ob01457e
日期:——
highly asymmetric Michaeladdition reaction between maleimides and aliphatic aldehydes catalyzed by low-loading β-turn tetrapeptides with excellent yields and enantioselectivities at room temperature was reported. α-Branched and α-unbranched aldehydes both are suitable nucleophiles. N-Aryl, alkyl and hydrogen maleimides all are well tolerated and led to high yields and enantioselectivities. The transformation
α,β-dipeptides as chiralorganocatalysts in the asymmetricMichaeladditionreaction between enolizable aldehydes and N-arylmaleimides or nitroolefins is described. With N-arylmaleimides as substrates, the best results were achieved with dipeptide 2 as a catalyst in the presence of aq. NaOH. Whereas dipeptides 4 and 6 in conjunction with 4-dimethylaminopyridine (DMAP) and thiourea as a hydrogen bond
The effect of chiral <i>N</i>-substituents with methyl or trifluoromethyl groups on the catalytic performance of mono- and bifunctional thioureas
作者:Josué Vazquez-Chavez、Socorro Luna-Morales、Diego A. Cruz-Aguilar、Howard Díaz-Salazar、Wilmer E. Vallejo Narváez、Rodrigo S. Silva-Gutiérrez、Simón Hernández-Ortega、Tomás Rocha-Rinza、Marcos Hernández-Rodríguez
DOI:10.1039/c9ob01893j
日期:——
thiourea organocatalysts that incorporate a chiral group which includes a trifluoromethyl moiety and contrasted their performance with non-fluorinated analogs. The comparison between such systems allows the direct study of the NH acidity of a thiourea bonded to an aliphatic substituent. In principle, –CF3 systems feature an enhanced hydrogen bond (HB) donor capacity that is undoubtedly beneficial for
A highly efficient asymmetric Michael addition of α,α-disubstituted aldehydes to maleimides catalyzed by primary amine thiourea salt
作者:Feng Yu、Zhichao Jin、Huicai Huang、Tingting Ye、Xinmiao Liang、Jinxing Ye
DOI:10.1039/c0ob00154f
日期:——
The first highlyefficientMichaeladdition of challenging α,α-disubstituted aldehydes to maleimides catalyzed by a simple bifunctional primary amine thiourea catalyst/benzoic acid system has been successfully developed to generate quaternary carbon centers in high yields (up to 99%) with excellent enantioselectivities (91–99%).