Asymmetric Latent Carbocation Catalysis with Chiral Trityl Phosphate
作者:Jian Lv、Qichao Zhang、Xingren Zhong、Sanzhong Luo
DOI:10.1021/jacs.5b11085
日期:2015.12.16
Stable carbocations such as tritylium ions have been widely explored as organic Lewisacid catalysts and reagents in organic synthesis. However, achieving asymmetric carbocation catalysis remains elusive ever since they were first identified over one century ago. The challenges mainly come from their limited compatibility, scarcity of chiral carbocations, as well as the extremely low barrier to racemization
AgAsF<sub>6</sub>/Sm(OTf)<sub>3</sub> Promoted Reversal of Enantioselectivity for the Asymmetric Friedel−Crafts Alkylations of Indoles with β,γ-Unsaturated α-Ketoesters
The first example of central metal controlled reversal of enantioselectivity in asymmetric Friedel-Crafts alkylation of Indoles and beta,gamma-unsaturated alpha-ketoesters has been developed. Using the same chiral starting material derived N,N'-dioxides 1 a and 1 b as ligands, various indole esters 4 were obtained In good to excellent yields and enantioselectivities. The reaction also featured mild reaction conditions and remarkably low catalyst loading (down to 0.01 mol %).
Enantioselective Friedel–Crafts alkylation of indoles with β,γ-unsaturated α-ketoesters catalyzed by new squaramide-linked bisoxazoline–Zn(OTf)2 complexes
作者:Sheng-Jian Jia、Da-Ming Du
DOI:10.1016/j.tetasy.2014.05.011
日期:2014.7
Enantioselective Friedel-Crafts alkylation reactions of indoles with beta,gamma-unsaturated alpha-ketoesters catalyzed by novel chiral C-2-symmetric squaramide-linked bisoxazoline-Zn(OTf)(2) complexes were investigated. The corresponding indole ketoesters were obtained in good to excellent yields (up to 98%) and with high enantioselectivities (up to 94% ee). This is the first report on the use of chiral squaramide-linked bisoxazoline SQBOX in a catalytic enanitioselective Friedel-Crafts alkylation reaction. (C) 2014 Elsevier Ltd. All rights reserved.