Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

Abstract

A series of bulky geometry-constrained iminopyridylpalladium chlorides were developed. The steric environment adjacent to the nitrogen atom in the pyridine rings and diimine parts enhanced the thermal stability of the palladium species. Bulkier groups at the imino group stabilized the palladium species and the corresponding palladium chlorides showed high activities in the coupling reaction of aryl chlorides.

Synthesis, characterization and evaluation of bulky bis(pyrazolyl)palladium complexes in Suzuki–Miyaura cross-coupling reactions

“…(Yield ¼ 501. 22 Synthesis of 1-benzyl-3,5-diphenyl-1H-pyrazole (3). Into a round bottom ask containing 20 mL acetonitrile, 51.170 mg (0.9120 mmol) of KOH was added and the mixture was stirred for 10 min.…”

“…Synthesis of biaryl compounds, which are the building blocks for the preparation of the Merck and Novartis hypertensive drugs losartan and valsartan, involves the use of transition metal catalysts such as palladium and copper. [1][2][3][4][5] Most notably, palladium complexes have gained widespread use as catalysts in both industry and academia for performing cross-coupling reactions mainly due to their thermal, oxidative and moisture stability, facile synthesis and the ability to modulate the steric and electronic properties of these palladium complexes. 6 Bisligated palladium complexes, especially those with bulky monodentate ligands are well known for their anticancer properties 7,8 and as effective cross-coupling catalysts.…”

Encaging palladium(0) in layered double hydroxide: A sustainable catalyst for solvent-free and ligand-free Heck reaction in a ball mill

“…The homogeneous palladium salts along with phosphine- or nitrogen-based ligands were employed as the traditional catalyst systems not only in solution-based C–C cross coupling [ 13 – 16 ] reactions but also in mechanically activated Heck [ 4 , 17 – 22 ], Suzuki [ 23 – 26 ], and Sonogashira [ 5 , 27 – 28 ] coupling reactions. The limitations of which are obviously unstable ligands and expensive Pd catalysts.…”

A catalytic system with high efficiency and recyclability based on Suzuki and Heck reaction in aqueous admicellar medium

“…Recently, we have developed a salen‐type palladium (II) catalyst (Z 4 ) that exhibits excellent catalytic activity for Suzuki and Heck cross‐coupling reactions under mild conditions (Figure ). The steric environment adjacent to the nitrogen atom in the ligand parts enhanced the thermal stability of the palladium species . On the other hand, increasing the donor capacity and steric bulk of the ligand should favor the oxidation addition and reduction elimination steps in the catalytic cycle, respectively .…”