Substituenteneffekte in den13C-NMR-Spektren von diastereomeren Chalkondihalogeniden, 10. Mitt.: Erste Synthese und Konfigurationsbestimmung vonthreo-Chalkonbromhydrinen
摘要:
The first synthesis of threo chalcone bromohydrins was realized by reaction of trans chalcone epoxides with SnBr4 in molar ratios from 1:1 to 2:1. The compounds were obtained in high yields and isomeric purity. Their configuration was determined as threo by different methods based on C-13-NMR shifts of C-alpha and C-beta atoms.
Asymmetric synthesis of new γ-butenolides via organocatalyzed epoxidation of chalcones
作者:Lucas C. C. Vieira、Bianca T. Matsuo、Lorena S. R. Martelli、Mayara Gall、Marcio W. Paixão、Arlene G. Corrêa
DOI:10.1039/c7ob00165g
日期:——
medicinally important agents. In this work we describe a new metal-free sequential strategy for the asymmetric synthesis of substituted γ-butenolides having epoxychalcones as the advanced intermediate. Using the optimized reaction conditions, we were able to carry out the three-step sequence, epoxidation, olefination and hydrolysis, with only one single chromatographic purification of the final product
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.
Asymmetric C–C bond formation via Darzens condensation and Michael addition using monosaccharide-based chiral crown ethers
作者:Péter Bakó、Zsolt Rapi、György Keglevich、Tamás Szabó、Péter L. Sóti、Tamás Vígh、Alajos Grűn、Tamás Holczbauer
DOI:10.1016/j.tetlet.2011.01.094
日期:2011.3
phase asymmetric Darzens condensations were promoted by d-glucose- and d-mannose-based crown ethers. The corresponding aromatic and heteroaromatic α,β-epoxyketones were obtained with moderate to high enantioselectivities (up to 96%) as well as diastereoselectivities (up to 98:2) under mild reaction conditions. The absolute configurations of several of the epoxyketones were determined by single crystal
Lanthanide complexes combined with chiral salen ligands: application in the enantioselective epoxidation reaction of α,β-unsaturated ketones
作者:Xuexiu Xia、Chengrong Lu、Bei Zhao、Yingming Yao
DOI:10.1039/c9ra01529a
日期:——
1,2-diphenyl-1,2-ethanediamine) were employed in the enantioselective epoxidation of α,β-unsaturatedketones. It was found that the salen–La complex shows the highest efficiency and enantioselectivity. A relatively broad scope of α,β-unsaturatedketones was investigated, and excellent yields (up to 99%) and moderate to good enantioselectivities (37–87%) of the target molecules were achieved.
容易获得的镧系酰胺 Ln[N(SiMe 3 ) 2 ] 3 (Ln = Nd ( 1 ), Sm ( 2 ), Eu ( 3 ), Yb ( 4 ), La ( 5 )) 与手性 salen 配体 H 2结合La (( S , S )-N , N'-二- ( 3,5-二取代的亚水杨基)-1,2-环己二胺)和H 2 Lb ( ( S , S ) -N , N'-二-(3,5-二取代-水杨基)-1,2-二苯基-1,2-乙二胺)用于α,β-不饱和酮的对映选择性环氧化。结果发现,salen-La 配合物表现出最高的效率和对映选择性。研究了相对广泛的 α,β-不饱和酮,并实现了目标分子的优异产率(高达 99%)和中等至良好的对映选择性(37-87%)。
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