Stereoselective Nucleophilic Fluoromethylation of Aryl Ketones: Dynamic Kinetic Resolution of Chiral α-Fluoro Carbanions
作者:Xiao Shen、Wenjun Miao、Chuanfa Ni、Jinbo Hu
DOI:10.1002/anie.201308484
日期:2014.1.13
selectivity than the corresponding difluoromethylation and proceeded via a different type of transition state. Excellent stereoselective control at the fluorinated carbon chiral center was found, an effect believed to be facilitated by the dynamic kinetic resolution of the chiral α‐fluoro carbanions.
The combination of the catalytic power of photocatalysis and biocatalysis has greatly boosted the development of novel synthetic strategies due to its functional diversity and stereoselective specificity. Herein, we describe a one-potcascadeprocess that combined photo-oxidative fluoridation and bio-reduction to access enantiocomplementary vicinal fluoro alcohols with up to 87% isolated yield and 99%
由于其功能多样性和立体选择性,光催化和生物催化的催化能力的结合极大地促进了新型合成策略的发展。在这里,我们描述了一种单锅级联工艺,该工艺将光氧化氟化和生物还原相结合,以获得高达 87% 的分离产率和 99% ee 的对映互补邻氟醇。
Synthesis of Enantiopure Fluorohydrins Using Alcohol Dehydrogenases at High Substrate Concentrations
作者:Wioleta Borzęcka、Iván Lavandera、Vicente Gotor
DOI:10.1021/jo400962c
日期:2013.7.19
The use of purified and overexpressed alcohol dehydrogenases to synthesize enantiopure fluorinated alcohols is shown. When the bioreductions were performed with ADH-A from Rhodococcus ruber overexpressed in E. coli, no external cofactor was necessary to obtain the enantiopure (R)-derivatives. Employing Lactobacillus brevis ADH, it was possible to achieve the synthesis of enantiopure (S)-fluorohydrins at a 0.5 M substrate concentration. Furthermore, due to the activated character of these substrates, a huge excess of the hydrogen donor was not necessary.
Ruthenium-catalysed asymmetric transfer hydrogenation of para-substituted α-fluoroacetophenones
作者:Erik Fuglseth、Eirik Sundby、Bård H. Hoff
DOI:10.1016/j.jfluchem.2009.03.011
日期:2009.6
The first examples of asymmetric transfer hydrogenation of alpha-fluoroacetophenones are reported. Eight para-substituted a-fluoroacetophenones have been reduced using four catalytic systems constructed of [RuCl2(p-cymene)(2)](2) or [RuCl2(mesitylene)(2)](2) in combinations with each of the ligands (1R,2R)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine ((R,R)-TsDPEN) and (1R,2R)-N-(p-toluenesulfonyl)-1,2cyclohexanediamine ((R,R)-TsCYDN). All reactions were performed in both water and formic acid/triethylamine. The highest enantioselectivity was obtained using the (R,R)-TsDPEN ligand in a formic acid/triethylamine mixture, giving the (S)-1-aryl-2-fluoroethanols in high to moderate enantiomeric excess (97.5-84.5%). For this solvent system the presence of electron withdrawing groups in the para position reduced the enantioselectivity. Reactions performed in water generally gave lower enantioselectivity and reaction rate, although RuCl(mesitylene)-(R,R)-TsDPEN yielded the product alcohols with enantiomeric excess in the range of 95.5-76.5%. (c) 2009 Elsevier B.V. All rights reserved.