An asymmetric 1,4-addition reaction of 5H-oxazol-4-ones to alkynones using chiral guanidine catalysts bearing a hydroxy group at the appropriate position was developed, and applied to several substrates. The method provides a synthetically useful enone-substituted α-hydroxy acid derivatives with a chiral quaternary α-carbon atom.
asymmetric Michael reaction between 5H‐oxazol‐4‐ones and α,β‐unsaturated acylimidazoles is reported. A novel 2‐benzo[b]thiophenyl‐modified chiral ProPhenol species is synthesized and used as a ligand, leading to good enantioselectivities in this asymmetric conjugate addition reaction. Furthermore, the introduction of phenol additives as achiral co‐ligands is found to improve the reaction’s chemical yields
据报道,5 H-恶唑-4-酮与α,β-不饱和酰基咪唑之间存在不对称迈克尔反应。合成了一种新型的2-苯并[ b ]硫代苯基修饰的手性脯酚,并用作配体,从而在该不对称共轭加成反应中产生了良好的对映选择性。此外,发现引入苯酚添加剂作为非手性配体可提高反应的化学收率,非对映选择性和对映选择性。
Stereoconvergent 1,4-Addition Reaction of 5<i>H</i>
-Oxazol-4-ones with <i>E</i>
,<i>Z</i>
Isomeric Mixture of Alkylidene β-Ketoesters Catalyzed by Chiral Guanidines
A 1,4‐addition reaction of 5H‐oxazol‐4‐ones to alkylidene β‐ketoesters, which was catalyzed by using chiral guanidines via a dynamickineticresolution process that involved geometric isomerization of the alkylidene β‐ketoesters, was developed. This method allowed using E,Z isomeric mixture of various acyclic alkylidene β‐ketoesters to obtain the products stereoselectively. The relation between the