Phosphine ligands enable challenging Suzuki-Miyaura coupling and Miyaura borylation

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Phosphine ligands enable challenging Suzuki-Miyaura coupling and Miyaura borylation

 

Author: Chow, Wing Kin
Title: Phosphine ligands enable challenging Suzuki-Miyaura coupling and Miyaura borylation
Degree: Ph.D.
Year: 2014
Subject: Ligands (Biochemistry)
Phosphorus compounds.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Applied Biology and Chemical Technology
Pages: xv, 519 p. : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2695998
URI: http://theses.lib.polyu.edu.hk/handle/200/7404
Abstract: A proper ligand design was found to be very important for substantial improvement in metal-catalyzed coupling reactions. After recognizing the preliminary relationship between the ligand structure and the effect of the coupling reaction, a series of new ligands have been designed and prepared for the bond-forming methodologies. Although remarkable progress has been made, the design for specific ligand to decipher some problematic and challenging bond-construction catalysis is still of great demand. Based on previous reports, the improvements of ligands provide a favorable platform to explore other problematic and difficult substrates in these cross-coupling reactions. Herein, we reported the application of modified indolyl phosphine ligands in the challenging palladium-catalyzed Suzuki-Miyaura Coupling and Miyaura Borylation. New indolyl phosphine ligands with the phosphine group (-PPh₂ or -PCy₂) was attached at the C-3 position were highly active towards the Suzuki-Miyaura coupling and Miyaura borylation of aryl chlorides. The Pd/PPh2-Andole-phos and Pd/PPh2-Nadole-phos systems catalyzed the challenging tetra-ortho-substituted biaryl coupling reactions, while PPh2-Andole-phos further provides highly effective catalytic system for the borylation of aryl chlorides. Furthermore, the catalytic system is able to catalyze both borylation reaction and Suzuki-Miyaura coupling reaction in a one-pot sequential manner for the direct synthesis of biaryl compounds in excellent yields. The first palladium-catalyzed borylation of sterically demanding aryl halides with bis(neopentylglycolato)diboron is described. Notably, a range of functional groups was compatible of borylation in excellent yields. Besides, the ligand bearing with PCy2 exhibited exceedingly high activity in the Suzuki-Miyaura coupling of aryl chlorides. It could achieve very low catalyst loading in the reaction. The indolyl phosphine complexes in which the phosphine group was attached at the ortho position of the bottom ring were highly active towards coupling reactions of aryl tosylates and mesylates. The first general examples of palladium-catalyzed Suzuki-type cross-coupling of aryl and heteroaryl mesylates with potassium aryl and heteroaryltrifluoroborates are presented. In addition to the Pd/CM-phos system, the first successful examples of using alkenyl mesylates in alkenylation are also described. Noteworthy, the newly developed Pd/MeO-CM-phos catalyst system enables the borylation aryl tosylates and mesylates. This first successful Pd-catalyzed borylation features mild reaction conditions and has excellent functional group tolerance. The new one-pot three-step sulfonationborylation-cross-coupling cascade sequence provides more opportunities of a synthetic transformation, starting from phenols yet without isolation of intermediates for a facile assembly of biaryl motifs.

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