thiourea-modified l-Leu-based peptide (3,5-diCF3Ph)NHC(=S)-(l-Leu-l-Leu-Ac5c)2-OMe} with five-membered ring α,α-disubstituted α-amino acids (Ac5c) catalyzed a highly enantioselective 1,4-addition reaction between β-nitrostyrene and dimethyl malonate. The enantioselective reaction required only 0.5 mol % chiral peptide-catalyst in the presence of iPr2EtN (2.5 equiv.), and gave a 1,4-adduct with 93 % ee of
N-末端硫脲修饰的基于l -Leu 的肽 (3,5-diCF 3 Ph)NHC(=S)-( l -Leu- l -Leu-Ac 5 c) 2 -OMe} 具有五元环α,α-二取代的α-氨基酸(Ac 5 c)催化了β-硝基苯乙烯和丙二酸二甲酯之间的高度对映选择性1,4-加成反应。在i Pr 2 EtN(2.5 当量)存在下,对映选择性反应仅需要 0.5 mol% 的手性肽催化剂,并得到 1,4-加合物,93% ee,产率为 85%。作为迈克尔受体,各种β-硝基苯乙烯衍生物,如甲基、对氟、对溴和对可以应用苯基上的-甲氧基取代基、2-呋喃基、2-噻吩基和萘基β-硝基乙烯。此外,各种丙二酸烷基酯和环状β-酮酯可用作迈克尔供体。很明显,肽链的长度、右手螺旋结构、酰胺 N-Hs 和 N 端硫脲部分在不对称诱导中起着至关重要的作用。
Chiral Calcium Catalysts with Neutral Coordinative Ligands: Enantioselective 1,4-Addition Reactions of 1,3-Dicarbonyl Compounds to Nitroalkenes
Salt of the earth: The first chiral, coordinative alkaline earth metal catalysts have been developed. These catalysts effectively promote catalytic asymmetric additions of β‐dicarbonyl compounds to nitroalkenes in high yields with high enantioselectivities (up to 96 %).
Toward Efficient Asymmetric Carbon-Carbon Bond Formation: Continuous Flow with Chiral Heterogeneous Catalysts
作者:Tetsu Tsubogo、Yasuhiro Yamashita、Shū Kobayashi
DOI:10.1002/chem.201202896
日期:2012.10.22
A chiral Ca catalyst based on CaCl2 with a chiral ligand was developed and applied to the asymmetric 1,4‐addition of 1,3‐dicarbonyl compounds to nitroalkenes as a model system. To address product inhibition issues, the Ca catalyst was applied to continuous flow with a chiral heterogeneous catalyst. The continuous flow system using a newly synthesized, polymer‐supported Pybox was successfully employed
Enantioselective organocatalytic Michael addition of malonate esters to nitro olefins using bifunctional cinchonine derivatives
作者:Jinxing Ye、Darren J. Dixon、Peter S. Hynes
DOI:10.1039/b508833j
日期:——
and evaluated for asymmetric organocatalytic activity in the dimethyl malonate Michaeladdition to beta-nitrostyrene; thiourea derivative was identified as the most effective bifunctional organic catalyst and found to induce high enantioselectivity in the malonate ester Michaeladdition reaction to a range of nitroolefins.
progress has been made toward the development of metal-free catalysts of enantioselective transformations, yet the discovery of organic catalysts effective at low catalyst loadings remains a major challenge. Here we report a novel synergistic catalyst combination system consisting of a peptide-inspired chiral helical (thio)urea oligomer and a simple tertiary amine that is able to promote the Michael reaction