Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

Abstract

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV-visible and NMR) methods. A distorted square-planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single-crystal X-ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki-Miyaura cross-coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous-organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.

Molecular Organosulphur, Organoselenium and Organotellurium Complexes as Homogeneous Transition Metal Catalytic Systems for Suzuki Coupling

“…Thiourea ( L40 ) is considered as a versatile ligand framework (Figure 5) since it has shown its potential in analytical chemistry, catalysis and pharmaceutical drugs [47] . Ligands L40 ‐ L42 come under this category [47–49] L40 is commercially available [48] .…”

“…Thiourea ( L40 ) is considered as a versatile ligand framework (Figure 5) since it has shown its potential in analytical chemistry, catalysis and pharmaceutical drugs [47] . Ligands L40 ‐ L42 come under this category [47–49] L40 is commercially available [48] . The reaction of phenyl isothiocyanate with 2‐aminothiazole in dimethylformamide (DMF) medium afforded the ligand L41 (Figure 5) in high yields [47] …”

“…Li 2 PdCl 4 is reacted with L28 / L81 in presence of NaOAc (sodium acetate) for 48 hours at room temperature to obtain (Table 3) complex 51 / 52 in which the ligand coordinates in a bidentate (N, E) mode [35] . [Pd(PPh 3 ) 2 Cl 2 ] is used for synthesizing complex 53 by stirring with L41 in methanol at room temperature for 24 hours [47] . This reagent is also used to react with L33 to obtain complex 54 [42] .…”

“…However, in order to widen the substrate scope, some of the catalysts are used to mediate the reactions between various heteroaryl halides and arylboronic acids. The heteroarene ring systems that have been selected for investigation include pyridines, [26,32,33,35,36,37,47] pyrimidines, [55,73] thiophenes, [35,55] imidazoles, quinoline [37,73] etc. In some cases, electron donating, neutral and withdrawing as well as sterically hindered groups on the (hetero)aryl halides [26,32,33] and (hetero)arylboronic acid [50,47] are also tolerated in the reactions and formation of the coupled products occur in excellent yields.…”

Recent Advance of Ketones Synthesis from Carboxylic Esters

“…2019 年, Rengan 课题组 [28] 利用苯基噻唑基硫脲和 PdCl 2 (PPh 3 ) 2 反应, 制备了一种硫脲钯配合物, 以其作 为催化剂, 在 1 mol%催化剂用量下, 实现了苯酯和芳基 硼酸的 Suzuki-Miyaura 偶联(Scheme 8).…”