3164-09-8Relevant academic research and scientific papers
TEMPO-mediated aerobic oxidative synthesis of 2-aryl benzoxazoles via ring-opening of benzoxazoles with benzylamines
Rao, Mugada Sugunakara,Hussain, Sahid
, p. 2684 - 2694 (2021/07/26)
A simple and efficient TEMPO-mediated system for aerobic oxidative synthesis of 2-aryl benzoxazoles from readily available benzoxazoles and primary benzylic and hetero benzylic amines is presented in one pot. The reaction proceeds through the ring-opening of benzoxazoles and is followed by oxidative condensation with benzylamines. These metal-free, straightforward reactions worked well with a wide range of substrates, yielding moderate to good yields under mild conditions using air as an external green oxidant.
Syntheses, characterization, and catalytic potential of novel vanadium and molybdenum Schiff base complexes for the preparation of benzimidazoles, benzoxazoles, and benzothiazoles under thermal and ultrasonic conditions
Kargar, Hadi,Kargar, Khadijeh,Fallah-Mehrjardi, Mehdi,Munawar, Khurram Shahzad
, p. 593 - 605 (2021/06/21)
A new ONO-tridentate Schiff base ligand (H2L) derived from 3-methoxysalicylaldehyde and nicotinic hydrazide was synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, UV–Vis, and powder XRD studies. Then, oxovanadium(V) and dioxomolybdenum(VI) Schiff base complexes, VOL and MoO2L, were also prepared and characterized by different techniques. Moreover, the catalytic activities of both complexes were investigated for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles under reflux conditions as well as through ultrasonic irradiation. The results revealed several advantages of this procedure, including high product yields, short reaction times, facile work-up procedure, simplicity in operation, eco-friendly reaction conditions, and green aspects by avoiding toxic catalysts and solvents. Graphic abstract: [Figure not available: see fulltext.]
Dowex 50W: A green mild reusable catalyst for the synthesis of 2-aryl benzoxazole derivatives in aqueous medium
Datta, Arup
, p. 341 - 347 (2021/05/19)
In this work simple efficient, one pot and environmentally friendly method was developed for the synthesis of 2-Aryl-1H-benzoxazole derivatives at 80oC using ortho-aminophenol and various aldehydes. It has been found that Dowex 50W is an effective catalyst to prepare moderate to high yield of a variety of benzoxazole derivatives through a clean and simple process. Aqueous medium, green methodology, rapid reaction, reusability of heterogeneous catalyst are the great advantages of this protocol.
Heterogeneous palladium (II)-complexed dendronized polymer: A rare palladium catalyst for the one-pot synthesis of 2-arylbenzoxazoles
George, Smitha,Sreekumar, Krishnapillai
, (2020/12/14)
The palladium complex of dendronized amine polymer (EG–Gn–Pd, n = 0, 1 and 2) having ethylene glycol-initiated polyepichlorohydrin as core was synthesized on a Merrifield resin support and was well characterized. Generally, palladium catalysts are known for carbon–carbon coupling reactions. Here, a developed catalyst was found to be good for benzoxazole synthesis. Higher generation dendronized polymer (EG–G2–Pd) was found to be better catalyst over lower generation dendronized polymers. Moreover, dendronized polymers were found to be a better catalyst over dendrigraft polymers. The catalyst reusability was checked and good yield was obtained for five cycles.
Phosphine-phosphonium ylides as ligands in palladium-catalysed C2-H arylation of benzoxazoles
Yao, Zhenyu,Lin, Xing,Chauvin, Remi,Wang, Lianhui,Gras, Emmanuel,Cui, Xiuling
, p. 3250 - 3254 (2020/05/25)
As balanced electron-rich P,C-chelating ligands, phosphine-phosphonium-ylides are considered for their ability to in situ promote palladium-catalysed direct C(sp2)–H arylation. Using methyl phosphonium salts of 2,2'-bis(diphenylphosphino)-1,1'-binaphtyl (“methyl-BINAPIUM”) as ylide precursors under optimized reaction conditions, arylation of benzoxazole was found to proceed in moderate to high yield to give functional 2-aryl benzoxazoles. A strong anion effect of the non-salt free ylide was evidenced (TfO? > I? > PF6? ≈ salt-free). This first example of phosphonium ylides as ligands in catalytic C–H activation extends the prospect of their general implementation in homogeneous transition metal catalysis.
Efficient Cu-catalyzed intramolecular: O -arylation for synthesis of benzoxazoles in water
Gao, Hui,Li, Minxin,Mao, Zewei,Rao, Gaoxiong,Tang, Yanling
, p. 14317 - 14321 (2020/04/23)
An efficient method was developed for synthesis of benzoxazoles by Cu-catalyzed intramolecular O-arylation of o-halobenzanilides in water. This strategy provides several advantages, such as high yields, water as a green solvent and functional groups tolerance.
Acid-promoted cleavage of the C–C double bond of N-(2-Hydroxylphenyl)enaminones for the synthesis of benzoxazoles
Ge, Bailu,Peng, Yanling,Liu, Jing,Wen, Si,Peng, Cheng,Cheng, Guolin
, (2019/12/09)
An acid-mediated selective cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminones with formation a new C–O bond for the synthesis of 2-substituted benzoxazoles has been developed. This protocol proceeds under transition metal- and oxidant-free conditions with broad functional group tolerance. The oxidative cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminone is also realized using NCS or NFSI as oxidants with release of 2,2-dihalogen-acetophenone fragments.
Nickel catalysed construction of benzazoles: Via hydrogen atom transfer reactions
Adhikari, Debashis,Bains, Amreen K.,Dey, Dhananjay,Kundu, Abhishek,Yadav, Sudha
, p. 6495 - 6500 (2020/11/13)
Herein we report a homogeneous, phosphine free, inexpensive nickel catalyst that forms a wide variety of benzazoles from alcohol and diamines by a reaction sequence of alcohol oxidation, imine formation, ring cyclization and dehydrogenative aromatization. A reversible azo/hydrazo couple, that is part of the ligand architecture steers both the alcohol oxidation and dehydrogenation of the annulated amine under fairly mild reaction conditions. Interestingly, both the alcohol oxidation and amine dehydrogenation steps are directly mediated by hydrogen atom transfer (HAT), which is greatly facilitated by the reduced ligand backbone. The kH/kD for the amine dehydrogenation step, measured at 60 °C is 5.9, fully consistent with HAT as the rate determining factor during this step. This is a unique scenario where two consecutive oxidation steps towards benzazole formation undergo HAT, which has been substantiated via kinetic studies, KIE determination and intermediate isolation. This journal is
Synthesis and X-ray crystal structures of three new nickel(II) complexes of benzoylhydrazones: Catalytic applications in the synthesis of 2-arylbenzoxazoles
Layek, Samaresh,Agrahari, Bhumika,Kumar, Akash,Dege, Necmi,Pathak, Devendra D.
, (2019/11/11)
Three new complexes of nickel(II), having general formula [Ni(L1)(PPh3)] (1), [Ni(L1)(4-picoline)] (2), and [Ni(L2)(4-picoline)] (3) were synthesized by the reaction of Ni(OAc)2·4H2O with corresponding benzolyhydrazine-derived Schiff base ligands i.e. [4-(diethylamino)-2-hydroxybenzylidene]-benzohydrazonic acid (H2L1) or [2-(hydroxynaphthalen-1-yl)methylene]-benzohydrazonic acid (H2L2) and PPh3/4-picoline as co-ligand in 1:1:1 ratio in methanol. All the three complexes were air-stable, isolated as reddish brown solids and characterized by Elemental analysis, FT-IR, 1H, 13C{1H}, 31P{1H} NMR spectroscopy and mass spectrometry. The structures of all three complexes were determined by single crystal X-ray diffraction studies which revealed the distorted square planar geometry of the complexes. In these complexes, three coordination sites were occupied by ONO pincer type Schiff base ligand and the fourth site was blocked by phosphorus (P) or nitrogen (N) atom of the co-ligand. The catalytic potential of all three complexes was explored in the synthesis of a series of 2-arylbenzoxazoles from aldehydes and 2-aminophenol, using low catalyst loading (0.5 mol%). Complex 1 was found to be the best catalyst among three complexes, for the synthesis of a series of 2-aryl benzoxazoles. The ease of synthesis, air-stability and robustness of the catalyst, and good TONs are some of the key characteristics of the described catalytic system.
In-vitro Anti-cancer assay and apoptotic cell pathway of newly synthesized benzoxazole-N-heterocyclic hybrids as potent tyrosine kinase inhibitors
Desai, Sulaksha,Desai, Vidya,Shingade, Sunil
supporting information, (2019/11/13)
A series of benzoxazole-N-heterocyclic hybrids have been synthesized by a one-pot strategy. Molecular docking study revealed that such compounds have the ability to inhibit enzyme protein tyrosine kinase. The findings of this work have been the successful synthesis of benzoxazole scaffolds, featuring hybrids of benzoxazole with quinoline and quinoxaline respectively. The molecular docking studies have showed these compounds to be inhibitors of tyrosine kinase enzyme which triggers growth of cancer cells. The cytotoxicity study of compounds 4a-f showed better potency against breast cancer cell lines MCF-7 and MDA-MB-231 in contrast to oral and lung cancer cell lines KB and A549. The tyrosine kinase activity was measured using Universal Tyrosine Kinase Assay kit using horseradish peroxide (HRP)-conjugated anti-phosphotyrosine kinase solution as a substrate. The compounds 4c exhibited maximum inhibition in the activity of enzyme tyrosine kinase with IC50 value 0.10 ± 0.16 μM, than other compounds which were studied and thus proved to be inhibitors of enzyme tyrosine kinase. The selective index of all four compounds was found out to be greater than two, indicating the non-toxic behaviour, i.e. good anti-cancer activity. Further, fluorescence microscopic study helped to characterize the mode of cell death, which was found to be late apoptosis as indicated by the orange fluorescence. The SAR analysis has also been carried out.
