Organocatalysis in Conjugate Amine Additions. Synthesis of β-Amino Acid Derivatives
作者:Mukund P. Sibi、Kennosuke Itoh
DOI:10.1021/ja071739c
日期:2007.7.1
Conjugateaddition of O-protected hydroxylamines to pyrazole-derived enoates proceeds with high efficiency and enantioselectivity when chiral thioureas are used as activators. A wide variety of substrates undergo conjugate amine addition providing access to enantioenriched β-aminoacidderivatives. Structural requirements for the optimal thiourea catalyst have been established, and the results suggest
After prosperous dominoreactions towards benzopyrans, the products were used as the starting material in Lewis acid catalyzed and organocatalytic Diels-Alder reactions to build up a tricyclic system. Herein, an asymmetric induction up to 96% enantiomeric excess was obtained by the use of imidazolidinone catalysts. This approach can be utilized to construct the tricyclic system in numerous natural
Bianthryl-based organocatalysts for the asymmetric Henry reaction of fluoroketones
作者:Jan Otevrel、David Svestka、Pavel Bobal
DOI:10.1039/c9ob00884e
日期:——
catalytic system based on bianthrylbis(thiourea) for the asymmetric Henry reaction of fluoroketones and nitroalkanes that resulted from the screening of a library containing 31 chiral non-racemic organocatalysts. The corresponding adducts were isolated in up to 6 times shorter reaction time in comparison with the previously published organocatalysts. High levels of stereocontrol have been generally observed
Recognition of chiral carboxylates by 1,3-disubstituted thioureas with 1-arylethyl scaffolds
作者:Karla Elisa Trejo-Huizar、Ricardo Ortiz-Rico、María de los Angeles Peña-González、Marcos Hernández-Rodríguez
DOI:10.1039/c3nj00644a
日期:——
Chiral thioureas with 1-arylethyl and 1-arylethyl-2-2-2-trifluoroethyl (Ar = Ph, 1-Napht, 9-Anthr) scaffolds were used as hosts to recognize acetate and chiral mandelates. The higher binding obtained with the trifluoromethyl analogue is also reflected in the higher selectivity factor for one enantiomer. The C2 symmetry was also indispensable to obtain selectivity.
Asymmetric acyl-Strecker reaction using novel thiourea organocatalyst is described. Screening experiments of the catalysts revealed that a bifunctional organocatalyst afforded an enantio-enriched product via an unique mechanism. That is, dihydroisoquinoline derivatives were converted to a corresponding 1-cyano-1,2,3,4-tetrahydroisoquinolines using the bifunctional thiourea catalyst derived from Betti base in moderate yield and enantioselectivity.