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Recently, PEPPSI‐type palladium‐complexes bearing N‐heterocyclic carbene (NHC) ligand have commonly been used as the effective catalysts in the direct arylation of heteroaromatic compounds. In most of previous studies catalyzed by such complexes, unsaturated ring carbene ligands such as benzo[d]imidazol‐2‐ylidene and imidazol‐2‐ylidene were used. However, the use of saturated ring carbene ligands such as 4,5‐dihydro‐imidazol‐2‐ylidene has been highly limited. Therefore, in this study, four novel 4,5‐dihydro‐1H‐imidazolium salts were synthesized as saturated ring carbene precursors. Then, well‐defined air‐ and moisture‐stable four novel PEPPSI‐type palladium‐complexes with 4,5‐dihydro‐imidazol‐2‐ylidene ligands were prepared. All synthesized carbene precursors and palladium‐complexes were structurally characterized by different spectroscopic and analytical techniques. Further structural characterization of two of the palladium‐complexes was performed by single‐crystal X‐ray diffraction. Next, the palladium‐complexes were tested in the direct arylation of azoles such as 4,5‐dimethylthiazole and 1‐methyl‐1H‐imidazole with (hetero)aryl halides in presence of 1 mol% catalyst loading at 120°C. The results showed that these novel palladium complexes are effective catalysts. [ABSTRACT FROM AUTHOR]

• New imidazolinium salts and their PEPPSI-type palladium-complexes were synthesized. • Structures of new compounds were characterized by different spectroscopic techniques. • The catalytic activities of palladium-complexes were tested in the direct arylation of five-membered aromatic N-heterocycles with (hetero)aryl bromides by via C-H functionalization. In this study, a series of air- and moisture-stable imidazolidin-2-ylidene-based new palladium complexes with the general formula [PdX 2 (NHC)(Py)] were synthesized (NHC = N-heterocyclic carbene, Py = pyridine, X = Cl or I). The structures of the palladium complexes were characterized by different techniques such as 1H NMR, 13C NMR, FT-IR spectroscopy and elemental analysis. The more detailed structural characterization of one of the palladium complex was determined by single-crystal X-ray diffraction study. The catalytic activities of all palladium complexes were tested in the direct arylation of five-membered aromatic N-heterocycles such as 3,5-dimethylisoxazole and 1-methyl-1H-pyrrole-2-carboxaldehyde with (hetero)aryl bromides in presence of 1 mol% catalyst loading at 120 °C. Desired products were obtained in moderate to good yields. [Display omitted] [ABSTRACT FROM AUTHOR]

We reported the synthesis and characterization of butylene linked bis-benzimidazole based N -heterocyclic carbene (NHC) precursors and their PEPPSI-type bimetallic Pd-complexes, and we implemented its activities in the direct C5-arylation of 2-acetylfuran and 1-methylpyrrole-2-carboxaldehyde with various aryl bromides. The catalytic activities of the synthesized palladium-complexes were found to be very high. These complexes were fully characterized by different techniques such as 1H NMR, 13C NMR, FT-IR spectroscopy and elemental analysis. Image 1 • New butylene linked benzimidazolium salts and their PEPPSI-type bimetallic Pd-complexes were synthesized. • Structures of all new compounds were characterized by different techniques. • All Pd-complexes were used as catalysts in the direct C5-arylation of 2-acetylfuran and 1-methylpyrrole-2-carboxaldehyde. [ABSTRACT FROM AUTHOR]

• New imidazolinium salts and their PEPPSI-type palladium complexes were synthesized. • Structures of new compounds were characterized by different techniques. • All palladium complexes were used as catalysts in the direct C4-arylation of 3,5-dimethylisoxazole. In this study, the synthesis and characterization of four new imidazolinium salts as carbene precursors and their corresponding four new PEPPSI-type (PEPPSI = Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation) palladium complexes were reported. The structures of these new compounds were characterized by spectroscopic and analytical techniques. The catalytic activities of all palladium complexes were evaluated in the direct C4-arylation of 3,5-dimethylisoxazole with para -substituted aryl bromides, ortho -substituted aryl bromides and heteroaryl bromides. A range of functional groups such as methoxy, acetyl, formyl, fluoro, trifluoromethyl, nitrile or tert -butyl on the aryl bromide were succesfully tolerated, and good yields were generally obtained in presence of 1 mol% catalyst loading at 120 °C. [ABSTRACT FROM AUTHOR]

Due to the industrial importance of bi(hetero)arenes, the synthesis of these compounds by homogeneous Pd-catalyzed direct arylation is an important research topic in modern organic chemistry. In this study, PEPPSI-type, (PEPPSI = Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation), new Pd-catalysts with N -heterocyclic carbene ligand were synthesized, and they were used as catalysts in the synthesis of bi(hetero)arenes by direct arylation process. The structures of Pd-carbene complexes were elucidated by different spectroscopic and analytical techniques such as NMR, FT-IR and elemental analysis. The more detailed structural characterization of one of the complexes was determined by single-crystal X-ray diffraction study. Pd-carbene complexes were used as effective catalysts in the direct arylation of five-membered heteroaromatics such as thiophene, furan and thiazole derivatives with (hetero)aryl bromides for 1 h, in the presence of 1 mol% of catalyst loading, and successful results were obtained. • Benzimidazole-based PEPPSI-type palladium-complexes were synthesized. • The structures of palladium-complexes were characterized by different techniques. • The complexes were tested as catalysts in the direct arylation of five-membered heteroaromatics. [ABSTRACT FROM AUTHOR]

In this study, a series of benzimidazolium salts were synthesized as unsymmetrical N‐heterocyclic carbene (NHC) precursors. Benzimidazolium salts were used for synthesis of the PEPPSI (pyridine enhanced precatalyst preparation stabilization and initiation)‐themed, six new Pd‐complexes with the general formula [PdX2(NHC)(pyridine)]. The structures of all compounds were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR and FT‐IR. The more detailed structural characterization of four of the complexes was determined by single‐crystal X‐ray diffraction study. The catalytic activities of all Pd‐complexes were evaluated in the direct arylation of the 2‐acetylfuran and 2‐acetylthiophene with aryl bromides in the presence of 1 mol% catalyst loading. [ABSTRACT FROM AUTHOR]