New Chiral Lewis Bases Derived from L-Pipecolinic Acid Showing Stereocontrol Highly Dependent on the Catalyst Design in the Hydrosilylation of<i>N</i>-Phenyl Ketimines
作者:Juan F. Collados、María L. Quiroga-Feijóo、Carlos Alvarez-Ibarra
DOI:10.1002/ejoc.200900284
日期:2009.7
obtained by using the urea-pipecolinamide 5c, which proved to be an efficient activator of trichlorosilane. The observed reactivities and stereoselectivities have been rationalized not only on the basis of the conformational dependence of the ligands, but also by noncovalent interactions, which has allowed the structures of the transition states to be deduced. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451
基于手性 L-哌啶酸的催化剂,N-官能化的哌啶酰胺 4a-h 和 5a-e,是从 Boc-L-哌啶酸开始,通过简单的两步合成获得的。催化剂与三氯硅烷形成络合物,证明对标准 N-苯基亚胺底物的对映选择性加成有效 6。我们测试了配体的对映选择性,以确定 N-和 O-官能化对手性 α-的影响氨基酸。尽管 N-甲酰基哌啶酰胺会产生 R 构型的胺,但使用脲-哌啶酰胺 5c 获得了相反的结果,它被证明是三氯硅烷的有效活化剂。观察到的反应性和立体选择性不仅基于配体的构象依赖性,还可以通过非共价相互作用来推断过渡态的结构。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)