from l‐ and d‐xylose, and l‐ and d‐arabinose, respectively. These monosaccharide‐based chiral macrocycles were tested as phase transfer catalysts in a few asymmetric reactions. The xylal‐based crown compounds proved to be efficient catalysts in a few liquid‐liquid phase reactions. The epoxidation of trans‐chalcone and the Darzens condensation of α‐chloroacetophenone with benzaldehyde took place with
The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside-1 or mannopyranoside 2 have been applied as phase-transfercatalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetricinduction. It was found that the position of the substituents in the aromatic ring of the chalcone
A highly efficient catalytic kinetic resolution of 2,3-epoxy 3-aryl ketones via asymmetric ring-opening with pyrazole derivatives has been achieved by using a chiral N,N′-dioxide–Sc(iii) complex as the catalyst.
Enantioselective epoxidation of α,β-enones promoted by (1R,3S,4S)-2-azanorbornyl-3-methanol as an organocatalyst
作者:Jun Lu、Yun-He Xu、Feng Liu、Teck-Peng Loh
DOI:10.1016/j.tetlet.2008.07.175
日期:2008.10
(1R,3S,4S)-2-Azanorbornyl-3-methanol was synthesized form (R)-1-phenylethylamine and used as a catalyst for the enantioselectiveepoxidation of α,β-enones to afford the corresponding epoxides in good yields and high enantioselectivities at room temperature.
Asymmetric epoxidation of α,β-unsaturated ketones catalyzed by rare-earth metal amides RE[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub>with chiral TADDOL ligands
作者:Haiwen Shan、Chengrong Lu、Bei Zhao、Yingming Yao
DOI:10.1039/d0nj05228k
日期:——
The catalyticasymmetric epoxidation of α,β-unsaturatedketones by tert-butylhydroperoxide (TBHP) has been well established using rare-earth metal amides RE[N(SiMe3)2]3 (RE = La(1), Nd(2), Sm(3), Y(4), Yb(5)) with chiral TADDOL ligands. It was found that the combination of Yb[N(SiMe3)2]3 and chiral TADDOL ligand H2L2 ((4S,5S)-2,2-dimethyl-α,α,α′,α′-tetra-3,5-bis(trifluormethylphenyl)-1,3-dioxolane-4