Magnetically separable nano CeO2: a highly efficient catalyst for ligand free direct C–H arylation of heterocycles

Shelkar, Radheshyam S.; Balsane, Kishor Eknath; Nagarkar, Jayashree M.

doi:10.1016/j.tetlet.2014.12.069

Cited by 30 publications

(13 citation statements)

References 46 publications

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“…Next, the scope of various benzoxazoles was also evaluated. As our expectation both 5-methylbenzoxazole and 5-chlorobenzoxazole generally underwent the arylation to give the corresponding products in very good yields ranging from 82 to 95% except the case of 4-uorobenzaldehyde and 4-hydroxybenzaldehyde whose resulting arylated products were only obtained in signicantly diminished yields of 70-75% (Table 3, entries [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. For the benzoxazole bearing a nitro substituent, the lower yields of arylation products with various aldehydes were recorded even though harsher conditions (higher temperature for prolonged reaction time) were employed ( Table 3, entries [31][32][33][34][35][36][37].…”

Section: Optimization Of Reaction Conditionsmentioning

confidence: 91%

Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes

Tran

Hang

2018

RSC Adv.

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A novel and efficient methodology for the arylation of benzoxazoles with aromatic aldehydes catalyzed by deep eutectic solvent has been developed. The reaction smoothly proceeded with a wide range of substrates to give the desired products in high yields within short reaction time. Deep eutectic solvents are easily recovered and reused without significant loss of catalytic activity. Results and discussion Preparation and characterization of [ZnCl 2 ][ethylene glycol] 4DESs were synthesized by mixing zinc chloride and ethylene glycol (HBDs) at a dened molar ratio (1 : 4) and heating at 120 C for 1 h at atmospheric pressure under constant magnetic stirring until a homogeneous liquid was formed. The charge delocalization which occurs through hydrogen bonding between the halide anion and ethylene glycol is responsible for the decrease in the T m of the mixture. 52,53

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Section: Optimization Of Reaction Conditionsmentioning

confidence: 91%

Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes

Tran

Hang

2018

RSC Adv.

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“…A variety of electrophilic reagents including aryl halides, [21][22][23][24] aryl organometallic reagents, [25] unactivated simple arenes, [26] and phenol derivatives such as triflates, [19,27,28] mesylates, [29] sulfamates [30] and acids [31] have been employed for the transformation. Similarly, arene sulfonyl chlorides [32] and arene diazonium salts [33] are inexpensive and readily available arylating reagents. Among these arylating reagents, aryl halides have especially been employed as the most widely used arylating reagents owing to their commercial availability and substituted diversity.…”

Section: Scheme 1 Synthesis Of 2-arylsubstituted Benzoxazoles and Benmentioning

confidence: 99%

“…Kaloğlu, Kaloğlur & Özdemir variety of electrophilic reagents has been previously described by many groups. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] In previous works, similar substrates have been employed with higher catalyst loading (5%-20 mol%) and higher reaction time (5-48 h) has been chosen for the direct arylation of benzoazoles in presence of palladium catalysts. [21,22,[24][25][26][29][30][31][32] However, in the present work the catalyst loading was reduced to 1 mol%, and the reaction time was shortened to 4 h. Moreover, in the present study benzoxazole and benzothiazole can be efficiently and selectively arylated at the 2-position by palladium complexes bearing NHC ligands, and satisfactory results were obtained as compared to previously reported similar studies using aryl halides.…”

Section: Concise Reportmentioning

confidence: 99%

Direct C—H Bond Activation of Benzoxazole and Benzothiazole with Aryl Bromides Catalyzed by Palladium(II)‐N‐heterocyclic Carbene Complexes

2018

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Herein, we report that a series of novel palladium(II)‐NHC complexes (NHC=N‐heterocyclic carbene) were synthesized. The structures of all novel complexes were characterized by 1H NMR, 13C NMR, FT‐IR spectroscopy and elemental analysis techniques. These palladium(II)‐NHC complexes were tested as efficient catalysts in the direct C—H bond activation of benzoxazole and benzothiazole with aryl bromides in the presence of 1 mol% catalyst loading at 150 °C for 4 h. Under the given conditions, various aryl bromides were successfully applied as the arylating reagents to achieve the 2‐arylbenzoxazoles and 2‐arylbenzothiazoles in acceptable to high yields.

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“…However, the reusability of the catalyst was not as good as desirable. Even though ICP‐MS analysis indicated no apparent leaching, a decay in the yield of the product was found after each cycle …”

Section: Impregnated Magnetite In Organic Synthesismentioning

confidence: 94%

Magnetite and Metal‐Impregnated Magnetite Catalysts in Organic Synthesis: A Very Old Concept with New Promising Perspectives

2015

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Magnetite is a well-known material, with the impregnation of transition metals onto its surface being a very old protocol for preparing catalysts. However, only recently, the combination of both, magnetite and impregnation protocols, have been recognized as a powerful methodology to prepare catalysts. The impregnation protocol, of nearly all transition metals in the magnetite surface, has rendered the first generation of catalysts. These simple catalysts have been used in a very broad range of organic transformations. Thus, simple imine derivative formation or unknown reactions such as the direct cross β-alkylation of primary alcohols, through dehydrogenation, oxidation, addition, hydrogen autotransfer and multicomponent reactions has been accomplished using these catalysts. In most cases, these catalysts could be just isolated by magnetic decantation and reused several times without a detrimental effect on the initial results. In some cases, the study of the surface of the catalyst by means of several surface characterization techniques has permitted to determine the real species involved in the process and their structural changes within the reaction cycles. Furthermore, the post-modification of the catalysts by reduction or oxidation of the immobilized metal, or by the addition of ligands, has enlarged the applicability of this type of catalysts.

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Magnetically separable nano CeO2: a highly efficient catalyst for ligand free direct C–H arylation of heterocycles

Cited by 30 publications

References 46 publications

Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes

Deep eutectic solvent-catalyzed arylation of benzoxazoles with aromatic aldehydes

Direct C—H Bond Activation of Benzoxazole and Benzothiazole with Aryl Bromides Catalyzed by Palladium(II)‐N‐heterocyclic Carbene Complexes

Magnetite and Metal‐Impregnated Magnetite Catalysts in Organic Synthesis: A Very Old Concept with New Promising Perspectives

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