两种互补的手性催化剂,膦8d和 DMAP 衍生的ent - 23b,同时用于在均相条件下选择性活化作为酰基供体的两种不同非手性酸酐的混合物。所得活化中间体25和26与外消旋苯甲醇5反应,通过完全催化平行动力学拆分(PKR)形成对映体富集的酯( R ) -24和( S ) -17。对于 PKR 过程,芳酰基酯 ( R )- 24以近乎理想的对映选择性获得,但 ( S)- 17被大约污染。8% 的次要对映异构体 ( R ) -17来自第二个途径,通过形成混合酸酐27并在8d激活。
Preparative-Scale Synthesis of Vedejs Chiral DMAP Catalysts
作者:Artis Kinens、Simonas Balkaitis、Edgars Suna
DOI:10.1021/acs.joc.8b01687
日期:2018.10.19
A scalable synthesis of chiral Vedejs-type DMAP catalysts is reported. The key step of the synthesis is amination of the enantiomerically pure 4-chloropyridine derivative using well-defined ZnCl2(amine)2 complexes. A series of Zn(II)–amine complexes have been synthesized to explore the scope of the ZnCl2-mediated amination of 4-halopyridines. Mechanistic studies support a Zn(II)-facilitated nucleophilic
AcOLeDMAP and BnOLeDMAP: Conformationally Restricted Nucleophilic Catalysts for Enantioselective Rearrangement of Indolyl Acetates and Carbonates
作者:Trisha A. Duffey、Scott A. Shaw、Edwin Vedejs
DOI:10.1021/ja805541u
日期:2009.1.14
The rate of indotyl O- to C-acetyl or carboxyl rearrangement is accelerated by the electron-withdrawing N-diphenylacetyl group (DPA) using the conformationally restricted chiral catalysts AcOLeDMAP (12b) and BnOLeDMAP (13b). Highly enantioselective conversion to quaternary C-acetylated and C-carboxylated oxindoles is observed, even for substrates containing branched substituents. The rearrangement of the carboxylate substrates 19 occurs with complementary enantiofacial selectivity using catalyst 13b compared to the acetyl migrations of 16 catalyzed by 12b. Access to N-unsubstituted oxindoles is demonstrated by DPA cleavage with Et2NH.