19225-97-9Relevant articles and documents
Method for catalyzing direct arylation of imidazole compound by using palladium complex
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Paragraph 0047-0059, (2021/07/31)
The invention relates to a method for catalyzing direct arylation of an imidazole compound by using a palladium complex, which comprises the following steps: in the presence of alkali, taking the imidazole compound and aryl halide as raw materials, taking
Palladium Complexes of Thio/Seleno-Ether Containing N-Heterocyclic Carbenes: Efficient and Reusable Catalyst for Regioselective C-H Bond Arylation
Bhatt, Ramprasad,Bhuvanesh, Nattamai,Sharma, Kamal Nayan,Joshi, Hemant
, p. 532 - 540 (2020/02/11)
The synthesis of the novel S,CNHC type half-pincer ligand precursors (L1 and L2) is described herein by using the atom economy reactions of 1-(2-(phenylthio)ethyl)-1H-imidazole with benzyl bromide and bromodiphenylmethane, respectively. The analogous reaction of 1-(2-(phenylselanyl)ethyl)-1H-imidazole with 2-bromoethyl phenyl sulfide has also resulted in a imidazolium bromide (L3) which is a precursor of novel S,CNHC,Se type pincer ligand. The route of silver-NHC transmetalation was employed to get the palladium complexes [Pd(L1/L2–HBr)Cl2] (C1 and C2) and [Pd(L3–HBr)Cl]BF4 (C3). The imidazolium bromide (L1–L3) and palladium complexes (C1–C3) were characterized by using multinuclear NMR and HR-MS. The structure and bonding in the complexes C1 and C2 were validated by X-ray crystallography. Thermally robust and moisture/air insensitive palladium complexes C1–C3 have been explored in the catalysis of C–H bond arylation of imidazoles. The protocol operates under mild reaction conditions in air with an excellent regioselective C–H bond arylation at C-5 position in imidazoles. All the complexes were found to be efficient (yield up to 97 % in 12 h) in the catalysis; however, the activating pincer ligand framework containing Pd catalyst C3, was found to be utmost effective among the three catalysts. Only 0.5 mol-% catalyst loading is required to achieve admirable yield of the desired cross-coupled products. A wide range of substrates was examined, and the developed protocol was applicable to all derivatives with high functional group tolerance and greater efficiency. More importantly, the catalyst C3 has also been found recyclable up to five cycles with minor decrease in efficiency which is highly desirable feature for the development of economical and sustainable industrial reaction processes. The PPh3 and Hg poisoning tests have established the complete homogeneous nature of the catalysis.
Dimetallic Palladium-NHC Complexes: Synthesis, Characterization, and Catalytic Application for Direct C?H Arylation Reaction of Heteroaromatics with Aryl Chlorides
Lee, Jhen-Yi,Ghosh, Debalina,Kuo, Ya-Ting,Lee, Hon Man
, p. 648 - 658 (2020/01/02)
A series of dimetallic palladium(II)-NHC complexes comprised of 1,4-naphthalenyl or 9,10-anthracenyl spacer sandwiched between two imidazole rings was successfully synthesized. These complexes were characterized by 1H and 13C{1H} NMR spectroscopy and elemental analysis. The structures of two dimetallic palladium complexes and a related mononuclear palladium complex to be used for comparative studies were further characterized by X-ray diffraction. The dimetallic palladium complex with the 9,10-anthracenyl linker was very efficient in catalyzing direct C?H arylation reactions of heteroaromatic compounds (imidazoles, imidazo[1,2-a]pyridine, and thioazole) with a broad range of aryl chlorides, employing a mild monopalladium loading of 1.5 mol%.It allows for the effective use of aryl chlorides to prepare arylated heterocycles, previously only accessible with the more reactive bromide counterparts. Importantly, the catalytic activity of the dimetallic precatalyst was found to be higher than that of an analogous mononuclear complex. (Figure presented.).
