Ligand effects in palladium‐catalyzed Suzuki and Heck coupling reactions

Abstract

A range of sterically hindered diimine ligands and their palladium (II) complexes were synthesized. These compounds were fully characterized by elemental analysis, 1 H and 13 C-NMR spectroscopy. The use of the palladium complexes as catalysts for Suzuki and Heck coupling has been studied in an attempt to demonstrate the effect of side groups on catalytic activity. It was clearly seen that the location of side -CH 3 groups which bound to benzene ring had little effect on catalytic activity. Interestingly when we changed these -CH 3 groups with -Cl groups the activity of the complexes increased. On the other hand, side groups which bound to imine nitrogen also had a large effect on catalytic activity.

Room‐temperature Suzuki–Miyauracross‐coupling reaction with α‐diimine Pd(II) catalysts

“…This is explained in that the activity increases because of the increased reactivity and stability of the metal catalysts by use of increasing efficacious supporting ligands. [10] Having the most active precatalyst rac-C1 in hand, the solvent was then optimized, employing the cross-coupling between phenylboronic acid and 4-bromo-2,6-dimethylaniline as the benchmark reaction ( Table 1, entries [6][7][8][9]. Due to the steric hindrance and solubility of substrates, reactions in neat water appear to be more sensitive to steric bulk on the aryl bromide than in the PEG-400-H 2 O system.…”

“…The Pd‐catalyzed Suzuki–Miyaura cross‐coupling reaction, the cross‐coupling of aryl halides with arylboronic acids, is one of the most prevalent CC bond forming processes for the synthesis of biaryls . Heterogeneous catalysts are preferred from the practical point of view . However, homogeneous catalysts for Suzuki–Miyaura cross‐coupling reactions have also been developed by the use of novel ligands .…”

“…[1][2][3][4] Heterogeneous catalysts are preferred from the practical point of view. [5][6][7][8][9] However, homogeneous catalysts for Suzuki-Miyaura cross-coupling reactions have also been developed by the use of novel ligands. [10][11][12][13][14][15][16][17][18][19][20] Buchwald's group synthesized a very effective sulfonated phosphine ligand for these cross-coupling reactions in aqueous media.…”

Synthesis of Calixarene‐Based Bis(iminophosphoranes) and Their Use in Suzuki–Miyaura Cross‐Coupling

“…[1][2][3][4][5][6][7][8] In comparison, the related iminophosphoranes R 3 P=NR, also termed phosphazenes, have only rarely been employed for the preparation of transitionmetal-based catalysts. [1][2][3][4][5][6][7][8] In comparison, the related iminophosphoranes R 3 P=NR, also termed phosphazenes, have only rarely been employed for the preparation of transitionmetal-based catalysts.…”

Microwave-assisted aqueous Suzuki coupling reactions catalyzed by ionic palladium(II) complexes

“…Ligands 7 and 8 were prepared by an ion exchange reaction between the ligand 6 and excess 1-butyl-3-methylimidazolium chloride (BmimCl) or tetrabutylammonium chloride (TBAC) in isopropanol according to the literature [17]. 13 Syntheses of Pd(II) complexes; general procedure All the Pd(II) complexes were prepared according to the literature method [26]. The required ligand (1-8) (1 mmol) and Pd(MeCN) 2 …”