Recent Developments in Pd-Catalyzed Direct Arylations of Heteroarenes with Aryl Halides

Bellina, Fabio

doi:10.1007/3418_2015_121

Cited by 14 publications

(8 citation statements)

References 53 publications

(44 reference statements)

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“…3a,b Apart from aryl halides, benign coupling partners such as boronic acids, sodium sulfinates, acids, silanes, phenylhydrazine hydrate, and [Ph-I-Ph]BF 4 have been used for the synthesis of α-/β-aryl-indoles under palladium-or copper-catalyzed methodologies (eq 1). 3,4 Transition-metal-catalyzed approaches to the direct C-(β)arylation of protected indoles using arenes have also been reported under harsh reaction conditions (eq 2). 5 Nonetheless, these reactions provide a mixture of α-, β-, and α,β-diaryl-indoles and are only suitable for the nonsubstituted and symmetrically substituted arenes, as regioselective coupling of arenes has not been achieved.…”

mentioning

confidence: 99%

KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

et al. 2014

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A KO(t)Bu-mediated intermolecular oxidative C-C coupling of nitroarenes with indoles is presented in DMSO at room temperature in an open flask. By using this mild and economical methodology, syntheses of β-(2/4-nitroaryl)-indoles with sensitive functionalities such as bromo, iodo, cyano, and nitro were achieved chemo- and regioselectively. Synthesized β-(2/4-nitroaryl) indoles were transformed into densely functionalized biindoles, indoloindoles, and (4-aminoaryl)-indoles which demonstrate post-transformation utility of the developed methodology.

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mentioning

confidence: 99%

KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

et al. 2014

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“…ESI-MS m/z 204 [M+H]+. EI-MS, m/z (%): 203 (100), 173 (20), 204 (12), 103 (11), 89 (10). 1 H NMR (400 MHz, CDCl3) δ 8.37 -8.29 (m, 2H), 7.64 -7.59 (m, 2H), 7.57 (d, J = 2.0 Hz, 1H), 6.43 (d, J = 2.0 Hz, 1H), 3.95 (s, 3H).…”

Section: -Methyl-5-(4-nitrophenyl)-1h-pyrazole (3dc)mentioning

confidence: 99%

“…ESI-MS m/z 207 [M+H] + . EI-MS, m/z (%): 206 (100), 176 (26), 148 (20), 133 (27), 89 (53). 1 H NMR (400 MHz, CDCl3) δ 8.88 (s, 1H), 8.33 -8.22 (m, 2H), 8.23 (s, 1H), 7.77 -7.72 (m, 2H).…”

Section: -(4-nitrophenyl)thiazole (3ec)mentioning

confidence: 99%

Ligandless Palladium-catalyzed Direct C-5 arylation of azoles Promoted by Benzoic Acid in Anisole

Rosadoni¹,

Banchini²,

Bellini³

et al. 2022

Preprint

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Due to the widespread application of (hetero)arylazoles, the development of straightforward functional group-tolerant synthetic methods that enable selective heteroaromatic elaboration under mild conditions aroused considerable attention. Over the last years we were interested in studies aimed to broaden the substrate scope of the direct functionalization of azoles and, in particular, to develop efficient synthetic protocols for the carbon-carbon bond forming reaction by selective palladium-catalyzed Csp2-H bond activation of imidazole derivatives. During these studies, we discovered that the outcome of the Pd-catalyzed arylation of imidazoles with aryl bromides is deeply influenced by the nature of the reaction solvent. Specifically, it is well known that the Pd-catalyzed direct arylation of imidazoles with aromatic halides selectively leads to C-5 monoarylation products when polar aprotic solvents such as DMF (or DMA) are used as a reaction medium, but these solvents are coded as dangerous according to EHS (Environmental, Health, Safety) parameters. Instead, the use of aromatic solvents as the reaction medium for direct arylations, although some of them show good EHS values, is poorly reported, probably due to their low solvent power against reagents and their potential involvement in undesired side reactions. So, with the intention of filling this gap, in this paper, we have developed a selective C-5 arylation procedure in anisole as the solvent, discovering also the unprecedented role of benzoic acid as a promoter of the coupling.

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“…Direct arylation reaction between heteroarenes and aryl halides is a highly desirable strategy for the construction of heterobiaryls because a preliminary organometallic reagent is not necessary, and hence there are fewer reaction steps with a reduction in waste. − Typically, a high palladium loading of 2.5–5.0 mol % was required for this catalytic reaction. Previously, we reported PEPPSI-themed PdCl 2 complexes with a NHC ligands ( A2 ), which were effective in direct arylation for the formation of heterobiaryls .…”

Section: Introductionmentioning

confidence: 99%

Isomeric Palladium Complexes Bearing Imidazopyridine-Based Abnormal Carbene Ligands: Synthesis, Characterization, and Catalytic Activity in Direct C–H Arylation Reaction

et al. 2019

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A series of “abnormal” NHC ligand precursors based on imidazopyridines and their corresponding NHC-palladium diiodide complexes were prepared. Our study included the first report on a palladium complex with an abnormal NHC ligand derived from imidazo[1,5-a]pyridine. DFT calculation on the free ligands confirmed the higher electron-donating properties of the abnormal NHC ligands than their normal NHC isomers. The structural properties of all the complexes were studied in detail by single-crystal X-ray diffraction studies, revealing that, in general, Pd–carbene bond distances in palladium complexes with abnormal NHCs were longer than those in their isomers with normal NHCs. A significant trans influence is observed in the palladium complexes with abnormal NHC ligands. But in the complexes with normal NHC ligands, both Pd–carbene and Pd–N bond distances are short. Catalytic studies revealed that the palladium complexes were very efficient in catalyzing direct C–H arylation between 1,2-dimethylimidazole and aryl halides using a low Pd loading of 0.5 mol %. The difference in catalytic activity between the normal and abnormal isomers is, however, small.

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Recent Developments in Pd-Catalyzed Direct Arylations of Heteroarenes with Aryl Halides

Cited by 14 publications

References 53 publications

KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

Ligandless Palladium-catalyzed Direct C-5 arylation of azoles Promoted by Benzoic Acid in Anisole

Isomeric Palladium Complexes Bearing Imidazopyridine-Based Abnormal Carbene Ligands: Synthesis, Characterization, and Catalytic Activity in Direct C–H Arylation Reaction

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Recent Developments in Pd-Catalyzed Direct Arylations of Heteroarenes with Aryl Halides

Cited by 14 publications

References 53 publications

KOtBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

KOtBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

Ligandless Palladium-catalyzed Direct C-5 arylation of azoles Promoted by Benzoic Acid in Anisole

Isomeric Palladium Complexes Bearing Imidazopyridine-Based Abnormal Carbene Ligands: Synthesis, Characterization, and Catalytic Activity in Direct C–H Arylation Reaction

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KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles

KO^tBu-Mediated Aerobic Transition-Metal-Free Regioselective β-Arylation of Indoles: Synthesis of β-(2-/4-Nitroaryl)-indoles