Enantioselective direct fluorination and chlorination of cyclic β-ketoesters mediated by phase-transfer catalysts
作者:Jie Luo、Wenqin Wu、Li-Wen Xu、Yuezhong Meng、Yixin Lu
DOI:10.1016/j.tetlet.2013.03.028
日期:2013.5
A straightforward and practical method for the direct fluorination and chlorination of various beta-ketoesters employing a phase-transfer catalyst is developed. The desired products with fluorine/chlorine-substituted quaternary chiral centers are prepared with good to excellent enantioselectivities. (c) 2013 Elsevier Ltd. All rights reserved.
Asymmetric α-chlorination of β-ketoesters using bifunctional ammonium salt catalysis
Chiral urea-quaternary ammonium salt hybrid organocatalysts were tested for their capability to control asymmetric alpha-chlorination reactions of beta-ketoesters. After a careful screening we identified a structurally simple catalyst derivative that allowed us to obtain enantiomeric ratios up to 90:10 under operationally simple conditions using just 1 mol% of the catalyst.[GRAPHICS].