铁催化的高度区域和对映选择性有机转化具有普遍性和广泛的底物范围,在现代合成化学中具有深远的应用;本文基于具有金属和配体中心手性的顺式-Fe II配合物描述了一个例子。cis -β Fe II ( N 4 ) 配合物 [Fe II (L)(OTf) 2 ] (L = N , N '-bis(2,3-dihydro-1 H -cyclopenta-[ b ]quinoline-5- yl)- N , N'-二甲基环己烷-1,2-二胺)是一种有效的手性催化剂,可用于 N-杂芳烃与 α,β-不饱和 2-酰基咪唑的高度区域选择性和对映选择性烷基化,包括广泛的不对称 N1、C2、C3 烷基化吲哚(34 例)和吡咯和苯胺的烷基化(14 例),均具有高产物收率(高达 98%)、高对映选择性(高达 >99% ee)和高区域选择性。DFT 计算表明,铁络合物的“金属手性”顺式-β 构型和二级 π-π 相互作用是高对映选择性的原因。
Enantioselective Friedel−Crafts Alkylations of α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine−Scandium(III) Triflate Complexes
作者:David A. Evans、Keith R. Fandrick、Hyun-Ji Song
DOI:10.1021/ja052433d
日期:2005.6.1
An enantioselective Friedel−Craftsalkylation with α,β-unsaturated 2-acyl imidazoles and electron-rich aromatic nucleophiles catalyzed by bis(oxazolinyl)pyridine−scandium(III) triflate complexes has been accomplished. These α,β-unsaturated 2-acyl imidazoles are effective electrophiles for the Friedel−Crafts reaction. The resulting adduct 2-acyl imidazole is easily converted to amides, esters, carboxylic
Enantioselective Friedel−Crafts Alkylations Catalyzed by Bis(oxazolinyl)pyridine−Scandium(III) Triflate Complexes
作者:David A. Evans、Keith R. Fandrick、Hyun-Ji Song、Karl A. Scheidt、Risheng Xu
DOI:10.1021/ja072976i
日期:2007.8.1
The enantioselective Friedel-Crafts addition of a variety of indoles catalyzed by bis(oxazolinyl)pyridine-scandium(III) triflate complexes (Sc(III)-pybox) was accomplished utilizing a series of beta-substituted alpha,beta-unsaturated phosphonates and alpha,beta-unsaturated 2-acyl imidazoles. The acyl phosphonate products were efficiently transformed into esters and amides, whereas the acyl imidazole adducts were converted to a broader spectrum of functionalities such as esters, amides, carboxylic acids, ketones, and aldehydes. The sense of stereoinduction and level of enantioselectivity were found to be functions of the size of the substrate employed, the substitution on the ligand, and the catalyst loading. Molecular modeling of the catalyst with the bound substrates was performed based on the crystal structures of the catalyst complexes and the sense of stereoinduction observed in the addition reaction. Nonlinear effects over a range of catalyst concentrations implicate a mononuclear complex as the active catalyst.