Asymmetric Friedel–Crafts Alkylation of α-Substituted β-Nitroacrylates: Access to β<sup>2,2</sup>-Amino Acids Bearing Indolic All-Carbon Quaternary Stereocenters
作者:Jian-Quan Weng、Qiao-Man Deng、Liang Wu、Kai Xu、Hao Wu、Ren-Rong Liu、Jian-Rong Gao、Yi-Xia Jia
DOI:10.1021/ol403480v
日期:2014.2.7
A highly enantioselective Friedel–Crafts alkylation reaction of indoles with acyclic α-substituted β-nitroacrylates is developed under the catalysis of Ni(ClO4)2–bisoxazoline complex at 1 mol % catalyst loading, affording chiral indolic β-nitroesters bearing all-carbon quaternary stereocenters in excellent yields and ees of up to 97%. Transformation of one of the products to β2,2-amino ester and t
在Ni(ClO 4)2-双恶唑啉配合物的催化下,以1 mol%的负载量催化吲哚与非环状α-取代的β-硝基丙烯酸酯的高度对映选择性Friedel-Crafts烷基化反应,从而得到具有全碳的手性吲哚β-硝基酯四元立体中心,产率极高,ee高达97%。举例说明了其中一种产物通过硝基还原和连续的Pictet-Spengler环化反应转变为β2,2-氨基酯和四氢-β-咔啉。