Highly enantioselective Friedel–Crafts alkylation of indole and pyrrole with β,γ-unsaturated α-ketoester catalyzed by chiral dicationic palladium complex
作者:Kohsuke Aikawa、Kazuya Honda、Shunsuke Mimura、Koichi Mikami
DOI:10.1016/j.tetlet.2011.09.006
日期:2011.12
The chiral dicationic Pd complexes, bearing sterically demanding diphosphine ligands as Lewis acid catalysts, are shown to catalyze the asymmetric Friedel–Crafts (F–C) alkylations of indoles and pyrroles with β,γ-unsaturated α-ketoesters, to provide the F–C alkylation products with benzylic stereocenters in high yields and enantioselectivities. The reactive chelated structure, formed by the chiral dicationic
带有空间要求的二膦配体作为路易斯酸催化剂的手性二价Pd配合物,可以催化带有β,γ-不饱和α-酮酸酯的吲哚和吡咯的不对称Friedel-Crafts(FC)烷基化反应,从而提供F-具有苄基立体中心的C烷基化产物,收率高,对映选择性高。手性Pd络合物和亲电子试剂形成的反应性螯合结构对于在FC烷基化反应中获得高水平的不对称诱导非常重要。F–C产物可通过催化不对称烯序列容易地官能化以生成α-羟基酯。