Development of a novel chiral palladacycle and its application in asymmetric hydrophosphination reaction

Abstract

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.

Stereocontrol in Preparation of Cyclopalladated Alkylaromatic Oximes and Evaluation of Their Stereoselective Esterase-Type Catalytic Activity

“…This complex has cisoid arrangement of cyclopalladated ligands, − while for other cyclopalladated complexes, i.e., amines, the trans orientation is common. − Also, the ligand molecule is highly bent with dihedral angle between Pd–C–N mean planes equal to 121°. The observed bending of Pd 2 Cl 2 cycle in 2rac is probably due to intramolecular O–H···Cl bonds (H···Cl 2.37–2.49 Å, O–H···Cl 138–148°).…”

Imine Palladacycles: Synthesis, Structural Analysis and Application in Suzuki–Miyaura Cross Coupling in Semi-Aqueous Media

“…The palladium atoms are coordinated to an ortho carbon atom from the phenyl ring, a nitrogen atom from the C=N group and two oxygen atoms from the acetate ligands in distorted square-planar geometry. The imine units are in a trans arrangement, recently coined as the “butterfly” geometry, [ 38 ] with the metallated imines held together by the bridging acetate ligands. The bond distances and angles are within the reported values, with allowance for the palladium–oxygen distance trans to carbon [ cf .…”

Highly selective anti-cancer properties of ester functionalized enantiopure dinuclear gold(I)-diphosphine

“…Optical rotations were measured on the specified solution in a 0.1 dm cell with a Atago AP-300 polarimeter. The diphosphine ligands were prepared according to the literature methods [24,25].…”