exchange of the metal ion from Zr(IV) to Fe(III) leads to a switch in the enantioselectivity of binary acid-catalyzed conjugate hydride reductions. In the presence of Hantzsch ester, γ-indolyl β,γ-unsaturated α-keto esters could be reduced to the desired (S)- or (R)-products, respectively, with good to excellent enantioselectivity (up to 98% ee).
金属离子从 Zr(IV) 到 Fe(III) 的交换导致二元酸催化的共轭氢化物还原的对映选择性发生变化。在 Hantzsch 酯存在下,γ-吲哚基 β,γ-不饱和 α-酮酯可以分别还原为所需的 ( S )- 或 ( R )- 产物,具有良好至优异的对映选择性(高达 98% ee) .
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.