Direct ortho-arylation of 2-arylbenzoxazoles via C–H activation

Yang, Fan; Wu, Yangjie; Zhu, Zhiwu; Zhang, Junli; Li, Yanan

doi:10.1016/j.tet.2008.04.099

Cited by 51 publications

(37 citation statements)

References 34 publications

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“…Anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives can be arylated by aryl iodides under very similar reaction conditions thus attesting to the generality of the method. Others have shown that arylation of imines and heterocyclic substrates are possible under nearly identical conditions 37. Furthermore, extension of the method to the arylation of unactivated sp 3 C-H bonds has been achieved by incorporating a removable, pyridine-based auxiliary.…”

Section: Discussionmentioning

confidence: 99%

Palladium- and Copper-Catalyzed Arylation of Carbon−Hydrogen Bonds

2009

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The transition-metal-catalyzed functionalization of C-H bonds is a powerful method for generating carbon-carbon bonds. Although significant advances to this field have been reported during the last decade, many challenges remain. First, most of the methods are substrate-specific and thus cannot be generalized. Second, conversions of unactivated (i.e. not benzylic or alpha to heteroatom) sp 3 C-H bonds to C-C bonds are rare, with most examples limited to t-butyl groups-a conversion that is inherently simple because there are no β-hydrogens that can be eliminated. Finally, the palladium, rhodium, and ruthenium catalysts routinely used for the conversion of C-H bonds to C-C bonds are expensive. Catalytically active metals that are cheaper and less exotic (e.g. copper, iron, and manganese) are rarely used.This Account describes our attempts to provide solutions to these three problems. We have developed a general method for directing-group-containing arene arylation by aryl iodides. Using palladium acetate as the catalyst, we arylated anilides, benzamides, benzoic acids, benzylamines, and 2-substituted pyridine derivatives under nearly identical conditions. We have also developed a method for the palladium-catalyzed auxiliary-assisted arylation of unactivated sp 3 C-H bonds. This procedure allows for the β-arylation of carboxylic acid derivatives and the γ-arylation of amine derivatives. Furthermore, copper catalysis can be used to mediate the arylation of acidic arene C-H bonds (i.e. those with pKa values <35 in DMSO). Using a copper iodide catalyst in combination with a base and a phenanthroline ligand, we successfully arylated electron-rich and electron-deficient heterocycles and electron-poor arenes possessing at least two electron-withdrawing groups. The reaction exhibits unusual regioselectivity: arylation occurs at the most hindered position. This coppercatalyzed method supplements the well-known C-H activation/borylation methodology, in which functionalization usually occurs at the least hindered position. We also describe preliminary investigations to determine the mechanisms of these transformations. We anticipate that other transition metals, including iron, nickel, cobalt, and silver, will also be able to facilitate deprotonation/arylation reaction sequences.

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Section: Discussionmentioning

confidence: 99%

Palladium- and Copper-Catalyzed Arylation of Carbon−Hydrogen Bonds

2009

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“…This method has been applied to the arylation of substituted anilides,72 2-arylpyridines,75,76,77 benzoxazoles,75,78 and benzoic acid derivatives (Scheme 27 and eq. 30).…”

Section: Carbon-carbon Bond Formationmentioning

confidence: 99%

Palladium-Catalyzed Ligand-Directed C−H Functionalization Reactions

2010

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“…28,29 On other hand, benzoxazole unit has been employed as directing group for the regioselective C2 arylation of phenyl using a palladium catalyst in the presence of silver carbonate in trifluoroacetic acid ( Figure 2b). 30,31 A similar procedure was reported by Ding, Peng and coworkers for the direct C2 arylation of 2-arylbenzothiazole ( Figure 2c). 32 To the best of our knowledge, the reactivity of dihalogenophenyls bearing a benzoxazole or a benzothiazole as potential directing groups in palladium-catalyzed direct arylation has never been reported.…”

Section: Introductionmentioning

confidence: 72%

Palladium-catalyzed non-directed C–H bond arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole

Abdellaoui

Ammar

Soulé

et al. 2015

Catalysis Communications

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International audienceWe report, herein, on palladium-catalyzed direct arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole moieties, which don't act as directing groups. With moderate electron-withdrawing substituents on the aryl bromides as coupling partners, the reaction proceeds nicely using phosphine-free PdCl2 catalyst, and potassium pivalate/dimethylacetamide (PivOK/DMA) as catalytic system. The reaction was regioselective and occurred at the less hindered ortho-positions of fluorine or chlorine atom

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Direct ortho-arylation of 2-arylbenzoxazoles via C–H activation

Cited by 51 publications

References 34 publications

Palladium- and Copper-Catalyzed Arylation of Carbon−Hydrogen Bonds

Palladium- and Copper-Catalyzed Arylation of Carbon−Hydrogen Bonds

Palladium-Catalyzed Ligand-Directed C−H Functionalization Reactions

Palladium-catalyzed non-directed C–H bond arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole

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