Design and synthesis of hemilabile heterocyclic phosphine Ligands and their applications in palladium-catalyzed carbon-carbon and carbon-nitrogen bond-construction processes

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Design and synthesis of hemilabile heterocyclic phosphine Ligands and their applications in palladium-catalyzed carbon-carbon and carbon-nitrogen bond-construction processes

 

Author: Wong, Shun Man
Title: Design and synthesis of hemilabile heterocyclic phosphine Ligands and their applications in palladium-catalyzed carbon-carbon and carbon-nitrogen bond-construction processes
Degree: Ph.D.
Year: 2015
Subject: Phosphorus compounds.
Ligands (Biochemistry)
Catalysis.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Applied Biology and Chemical Technology
Pages: 1 volume (various pagings) : illustrations ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2798184
URI: http://theses.lib.polyu.edu.hk/handle/200/7898
Abstract: A new family of hemilabile benzimidazolyl phosphine ligands was designed and synthesized. The benzimidazole scaffold of this family of ligands could be easily prepared and diversified from inexpensive substituted o-phenylenediamines and substituted carboxylic acids by conventional Phillips benzimidazole synthesis. Two classes of ligands, P,N-type 2-arylated benzimidazolyl phosphine ligands and alterable P,O-or P,N-type 2-phosphino-substituted benzimidazolyl ligands, were successfully synthesized by a “Cross-matching approach. The 2-arylated benzimidazolyl phosphine ligands showed excellent catalytic activities for the Suzuki-Miyaura coupling of aryl chlorides with arylboronic acids, especially under very-low-catalyst-loading down to 1 ppm. In addition, these ligands were efficient towards Suzuki-Miyaura coupling of aryl chlorides with potassium aryltrifluoroborates. Notably, the X-ray crystallographic data confirmed that the ligand was coordinated in a κ2-P,N fashion to the palladium center. On the other hand, the palladium complexes of 2-phosphino-substituted benzimidazolyl ligands showed coordination in a κ2-P,N fashion and potential P,O-hemilabile ability, which could be altered by tuning the steric bulkiness of phosphino group. Interestingly, the complexes with P,O-coordination and P,N-coordination showed high efficacy towards Suzuki-Miyaura coupling and Buchwald-Hartwig amination of aryl chlorides, respectively. Particularly noteworthy, to probe with these fascinating hemilabile properties, chemoselective cross-coupling of aryl chlorides was also examined. The palladium-ligand complexes showed essentially complete orthogonal property (>99%) to afford Suzuki coupling products when carrying out competitive cross-coupling of aryl chlorides with arylboronic acids and amines.

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