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。
Asymmetric reduction using (R)-MeCBS and determination of absolute configuration of para-substituted 2-fluoroarylethanols
The asymmetric reduction of eight alpha-fluoroacetophenones has been investigated using (R)-MeCBS as a catalyst in various media. Based on a solvent screen, 1,2-dimethoxyethane, diethyl ether and dichloromethane were used in reductions of the alpha-fluoroacetophenones. The enantiomeric excess of the products depended oil the solvent and the electronic character of the aromatic substituents. Higher enantioselectivity and less solvent dependency were observed in the reduction of substrates bearing electron donating substituents, whereas the opposite was the case for reduction of the substrates with electron withdrawing substituents. The (R)-2-fluoro-1-arylethanols were obtained with enantiomeric excesses in the range of 91-99% using 1,2-dimethoxyethane as a solvent. Six of the alcohols produced are new chemical entities. The absolute configurations of the (R)-2-fluoro-1-arylethanols were determined by circular dichroism using the exciton chirality method of tile (S)-benzoate esters of the alcohols. The (S)-benzoate esters were obtained by lipase-catalysed resolution using Novozym 435. (C) 2008 Elsevier Ltd. All Fights reserved.