Counter-rotatable dual cinchona quinuclidinium salts and their phase transfer catalysis in enantioselective alkylation of glycine imines
作者:Jiin Oh、Jihyeon Park、Keepyung Nahm
DOI:10.1039/d1cc02785a
日期:——
Dual cinchona quinuclidinium salts with a diphenyl ether linker were synthesized and used as powerful asymmetric phasetransfer catalysts in the α-alkylation of imines of glycine and alanine ester with 0.01–0.1 mol% loading (17 examples, 92–99% ee). Skewed conformers of dual quinuclidiniums at TS were proposed to rationalize their high efficiency via DFT calculations.
The synthesis of the first calixarene-based chiralphase-transfercatalysts derived from cinchona alkaloids has been achieved in two steps from p-tert-butylcalix[4]arene. The catalytic efficiency of the chiral calix[4]arenes 3a–c was evaluated by carrying out the phase-transfer alkylation of N-(diphenylmethylene)glycine ethyl ester with benzyl bromide. Various factors that affect the chemical yield
Abstract Optically active α-amino acid was asymmetrically synthesized under soluble polymer-supported quinine by homogeneous phase catalytic reaction. The precursor of l -phenylalanine, Ph 2 NCH(CH 2 Ph)CO 2 C 2 H 5 (C 24 H 23 NO 2 , M r =364.38) has been determined by X-ray diffraction analysis. The crystal belongs to monoclinic system with space group P 2 1 / c , a =10.4539(10), b =9.8315(10), c
摘要 在可溶性聚合物负载的奎宁下,通过均相催化反应不对称合成了具有旋光活性的α-氨基酸。L-苯丙氨酸的前体Ph 2 NCH(CH 2 Ph)CO 2 C 2 H 5 (C 24 H 23 NO 2 ,M r =364.38)已通过X射线衍射分析确定。该晶体属于单斜晶系,空间群为 P 2 1 / c , a =10.4539(10), b =9.8315(10), c =19.8896(19) A, α =90.00, β =93.661(2), γ = 90.00°,V =2040.0(3) A 3 ,Z =4,D c =1.164 mg mm -3 ,μ =0.074 mm -1 ,F (000) = 760。最终的 R 和 wR 因子分别为 0.0463 和 0.1239,具有 3610 个(R int = 0.0291)独立反射。
Asymmetric PTC Alkylation of Glycine Imines: Variation of the Imine Ester Moiety
作者:Barry Lygo、Bryan Allbutt
DOI:10.1055/s-2003-43368
日期:——
Studies into the enantioselective phase-transferalkylation of a series of glycine imine esters are presented. Using a quaternary ammonium salt catalyst derived from α-methylnaphthylamine, high enantioselectivities were obtained in reactions involving imines containing tert-butyl, benzhydryl, and benzyl esters. In contrast, a quaternary ammonium salt catalyst derived from dihydrocinchonidine gave highest