Division of Chemistry and Biological Chemistry, Nanyang Technological University, Singapore, Singapore.
Dalton Trans. 2014 Apr 21;43(15):5777-84. doi: 10.1039/c4dt00062e. Epub 2014 Feb 26.
A novel amine ligand, 1-(2,5-dichlorophenyl)-N,N-dimethylethanamine, was synthesized from 1-(2,5-dichlorophenyl)ethanone via a three step synthetic route. Direct ortho-palladation of the amine ligand with Pd(OAc)(2) gave the racemic dimeric complex in high yield. This racemic palladacycle was efficiently resolved through the formation of its (S)-prolinato derivatives. The resulting diastereomeric complexes were separated efficiently by column chromatography. In the solid state, the structure and absolute configuration of the two optically resolved palladium complexes were determined by single crystal X-ray crystallography. In solution, their absolute conformations were also investigated by the 2D (1)H-(1)H rotating frame nuclear Overhauser enhancement (ROESY) NMR spectroscopy. Both (R,R) and (S,S)-di-μ-chloro dimeric palladium complexes could be obtained chemoselectively by treating the corresponding prolinato derivatives with dilute hydrochloric acid. The amine auxiliary could be subsequently removed from the palladium center by treatment with concentrated hydrochloric acid. The enantiomerically pure palladacycle was used to promote the asymmetric hydrophosphination reaction between diphenylphosphine and dimethyl acetylenedicarboxylate. The (31)P{(1)H} NMR spectroscopy indicated that only one stereo-isomeric product was formed.
一种新型的胺配体，1-(2,5-二氯苯基)-N,N-二甲基乙胺，是通过三步合成路线从 1-(2,5-二氯苯基)乙酮合成的。胺配体与 Pd(OAc)(2)的直接邻位钯化以高产率得到外消旋二聚体络合物。这种外消旋钯配合物通过形成其(S)-脯氨酸衍生物得到有效拆分。通过柱层析可有效地分离得到的非对映异构体络合物。在固态下，通过单晶 X 射线晶体学确定了两个光学拆分的钯配合物的结构和绝对构型。在溶液中，通过二维（1）H-(1)H 旋转框架核奥弗豪瑟增强（ROESY）NMR 光谱研究了它们的绝对构象。通过用稀盐酸处理相应的脯氨酸衍生物，可以选择性地获得(R,R)和(S,S)-二-μ-氯二聚钯络合物。随后可以用浓盐酸从钯中心除去胺辅助配体。手性纯的钯配合物用于促进二苯基膦和二甲酸乙酰基二乙酯之间的不对称氢膦化反应。(31)P{(1)H}NMR 光谱表明仅形成一种立体异构产物。
