Proline-Glycine Dipeptidic Derivatives of Chiral Phosphoramides as Organocatalysts for the Enantiodivergent Aldol Reaction of Aryl Aldehydes and Isatins with Cyclohexanone in the Presence of Water
(S)-proline-glycine dipeptides and incorporating a chiral phosphoramide fragment was accomplished. These chiral compounds catalyze the enantioselective aldol addition reaction of cyclohexanone to prochiral aryl aldehydes and isatins in the presence of water. These chiral organocatalysts represent some of the few proline-derived compounds capable to catalyze aldol-type addition of cyclohexanone to isatins, a C–C
(2S,4R)-Hyp-(S)-Phe-OMe dipeptide supported on imidazolium tagged molecules as recoverable organocatalysts for asymmetric aldol reactions using water as reaction medium
作者:Arturo Obregón-Zúñiga、Eusebio Juaristi
DOI:10.1016/j.tet.2017.07.037
日期:2017.9
evaluated as organocatalysts in the asymmetric aldol reaction using water as solvent. It was found that catalysts incorporating the hexanoyl linker are active down to 5 mol% and afford aldol products with up to 94% yield, up to 98:2 dr and up to 97:3 er. This chiral imidazolium catalyst was reused up to 6 times without any loss in the stereoselectivity of asymmetric aldol reactions. By contrast, organocatalysts
Improving the Catalytic Performance of (<i>S</i>)-Proline as Organocatalyst in Asymmetric Aldol Reactions in the Presence of Solvate Ionic Liquids: Involvement of a Supramolecular Aggregate
For the first time, a highly efficient and stereoselective asymmetricaldolreaction employing (S)-proline in the presence of solvate ionicliquids is reported. The reaction seems to proceed via a supramolecular aggregate of (S)-proline, the solvate ionicliquid, and water, affording high yields and excellent stereoselectivities with low catalyst loadings.
Multifunctional phosphoramide-(<i>S</i>)-prolinamide derivatives as efficient organocatalysts in asymmetric aldol and Michael reactions
作者:Carlos Cruz-Hernández、José M. Landeros、Eusebio Juaristi
DOI:10.1039/c9nj00300b
日期:——
The synthesis and evaluation of three novel chiral organocatalysts derived from (S)-proline and containing a bis-amidophosphoryl amine fragment are reported. The structure and conformation of the new compounds were determined by NMR spectroscopy and X-ray crystallographic analysis. The present study represents an effort directed to enhance the performance of (S)-proline-derived organocatalysts in asymmetric