Synthesis and Post-Resolution Modification of New Axially Chiral Ligands for Asymmetric Catalysis
作者:William J. Fleming、Helge Müller-Bunz、Patrick J. Guiry
DOI:10.1002/ejoc.201000794
日期:2010.11
The synthesis of four new members of the Quinazolinap series of ligands is described. Three of these ligands were prepared by post-resolution modification of the known ligand (R)-7-chloro-2-isopropyl-Quinazolinap, a new approach which offers an expedient route to a range of enantiopure ligands as it precludes the need for resolution of each ligand prepared. The remaining ligand, 7-chloro-2-methyl-Quinazolinap
描述了 Quinazolinap 系列配体的四个新成员的合成。其中三个配体是通过对已知配体 (R)-7-chloro-2-isopropyl-Quinazolinap 进行后解析修饰制备的,这是一种新方法,为一系列对映体纯配体提供了便利的途径,因为它排除了解析的需要制备的每种配体。剩下的配体,7-氯-2-甲基-喹唑啉,是在七步合成序列中制备的,其中钯和镍催化的转化是关键步骤。该配体的非对映异构纯钯环通过 X 射线晶体学表征。(R)-7-Chloro-2-isopropyl-Quinazolinap 用于乙烯基芳烃的铑催化硼氢化反应,区域选择性高达 > 99:1,ee 值高达 68%。将制备的每种喹唑啉配体应用于钯催化的乙酸 1,3-二苯基丙-2-烯酯烯丙基烷基化反应,转化率高达 100%,ee 值高达 85%。对其中一种配体的钯配合物的溶液相 NMR 研究为不对称感应提供了基本原理。