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.
Abstract New recyclable monoaza-15-crown ethers have been synthesized starting from ( R , R )-(+)- and ( S , S )-(−)-hydrobenzoin. These macrocycles proved to be efficient and reusable phase transfer catalysts in a few asymmetric reactions under mild conditions. The asymmetric epoxidation of trans -chalcone took place with up to 81% ee, while using other chalcone derivatives, the products were formed
摘要 以 ( R , R )-(+)- 和 ( S , S )-(-)- 氢安息香为原料合成了新的可回收单氮杂-15-冠醚。在温和条件下的一些不对称反应中,这些大环被证明是有效且可重复使用的相转移催化剂。反式查耳酮的不对称环氧化反应的 ee 高达 81%,而使用其他查耳酮衍生物时,生成的产物 ee 高达 68-88%。还使用溴丙二酸二乙酯在一些缺电子烯烃的环丙烷化中测试了基于氢安息香的套索醚,以提供具有良好对映选择性(54-75% ee)的产物。催化剂通过成盐回收,然后萃取,并在不损失活性和对映选择性影响的情况下重复使用。
Asymmetric Epoxidation of Unsaturated Ketones Catalyzed by Heterobimetallic Rare Earth–Lithium Complexes Bearing Phenoxy-Functionalized Chiral Diphenylprolinolate Ligand
作者:Qinqin Qian、Yufang Tan、Bei Zhao、Tao Feng、Qi Shen、Yingming Yao
DOI:10.1021/ol5020398
日期:2014.9.5
Four novel heterobimetalliccomplexes [REL2][(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate (RE = Yb (1), Y (2), Sm (3), Nd (4), H2L = (S)-2,4-di-tert-butyl-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol have been synthesized and characterized. These readily available complexes are highly active in catalyzing the epoxidation of α,β-unsaturated ketones, while
四种新型双核配合物[REL 2 ] [(THF)3李] 2(μ-Cl)的}通过手性苯氧基官能化prolinolate稳定(RE =镱(1),Y(2),SM(3),钕(4),H 2 L =(小号)-2,4-二-叔已经合成并表征了丁基-6-[[[2-(羟基二苯基甲基)吡咯烷-1-基]甲基]苯酚。这些容易获得的络合物在催化α,β-不饱和酮的环氧化中具有高活性,而对映选择性根据稀土中心的离子半径而变化。在10 mol%的1存在下,使用TBHP作为氧化剂,在0°C于80→99%ee下,将一系列查尔酮衍生物转化为手性环氧化物。