- Synthesis and free radical scavenging activity of coumarin derivatives containing a 2-methylbenzothiazoline motif
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Coumarin and benzothiazole scaffolds can be found in a number of natural or synthetic antioxidants. In an effort to develop a novel radical scavenger and potential antioxidant, a series of coumarin derivatives containing 2-methylbenzothiazoline motif and related compounds was synthesized and evaluated for their DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS ?+ (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals scavenging activities. Among them, 7-hydroxy-3-(2-methyl-2,3- dihydrobenzo[d]thiazol-2-yl)-2H-chromen-2-one (3e) has shown a significant free radical scavenging activity. From the structure-activity point of view, it was found that phenolic coumarin ring and benzothiazoline moiety in target compounds may contribute to the scavenging activity against free radicals. A series of coumarin derivatives containing a 2-methylbenzothiazoline motif and related compounds were synthesized and evaluated for their DPPH and ABTS ?+ radicals scavenging activities. 7-Hydroxy-coumarin derivative 3e showed a significant free radical scavenging activity. Copyright
- Khoobi, Mehdi,Emami, Saeed,Dehghan, Gholamreza,Foroumadi, Alireza,Ramazani, Ali,Shafiee, Abbas
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- Recyclization of 2-imino-2H-1-benzopyrans using nucleophilic reagents 3. Reaction of 2-iminocoumarin-3-carboxamides with o-phenylenediamines and o-amino(thio)phenols
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Using o-phenylenediamines, o-aminophenol or o-aminothiophenol, 2-iminocoumarin-3-carboxamide can be recyclized to the corresponding 3-(1H-benzimidazol-2-yl), 3-(benzoxazol-2-yl), or 3-(benzothiazol-2-yl) coumarins. An alternative synthesis has been carried out and an analytical comparison of the synthetic routes made.
- Kovalenko,Vasil'ev,Sorokina,Chernykh,Turov,Rudnev
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- Accessing the long-lived emissive 3IL triplet excited states of coumarin fluorophores by direct cyclometallation and its application for oxygen sensing and upconversion
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We studied four cyclometallated Pt(ii) complexes, in which the thiazo-coumarin ligands (Pt-2, Pt-3 and Pt-4) or the phenylthiazo ligand (Pt-1) were directly cycloplatinated. Pt-2 shows intense absorption in visible region but other complexes show blue-shifted absorption. Room temperature phosphorescence was observed for all the complexes, and the emission wavelength is dependent on the size of the π-conjugation, not the intramolecular charge transfer (ICT) feature of the CN ligands. Pt-2 shows longer phosphorescence lifetime (τ = 20.3 μs) than other complexes (below 2.0 μs). Furthermore, Pt-2 shows phosphorescence quantum yield Φ = 0.37, whereas Pt-3 and Pt-4 show much smaller Φ values (0.03 and 0.01, respectively). DFT/TDDFT calculations indicate 3IL triplet excited states for the complexes. The complexes were used as for luminescence O2 sensing and triplet-triplet-annihilation (TTA) based upconversion. Stern-Volmer quenching constant KSV = 0.026 Torr-1 was observed for Pt-2, ca. 89-fold of that of Pt-3. TTA upconversion is achieved with Pt-2 (λem = 400 nm with λex = 473 nm, anti-Stokes shift is 0.47 eV, excitation power density is at 70 mW cm-2). The upconversion quantum yield with Pt-2 as triplet sensitizer is up to 15.4%. The TTET efficiency (KSV = 1.33 × 105 M-1, kq = 6.57 × 109 M-1 s-1. DPA as quencher) of Pt-2 is 34-fold of the model complex [Ru(dmb) 3][PF6]2. Our results show that the 3IL state can be readily accessed by direct cyclometallation of organic fluorophores and this approach will be useful for preparation and applications of transition metal complexes that show intense absorption in visible region and the long-lived emissive 3IL excited states.
- Wu, Wenting,Wu, Wanhua,Ji, Shaomin,Guo, Huimin,Zhao, Jianzhang
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- Synthesis and biological evaluation of benzothiazole derivatives of pyrimidines, acrylonitriles, and coumarins
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A number of benzothiazole derivatives of 2-aminopyrimidines (3a-b, 5, 6a-b, and 7), benzothiazole-3-arylacrylonitriles (10a-c), and benzothiazol-2-yl-coumarins (18a c, and 20) were synthesized by reacting benzothiazole derivatives with dicarbonyl compound
- Youssef, Amal M.,Mohamed, Hany M.,Czezowski, Caitlin,Ata, Athar,Abd-El-Aziz, Alaa S.
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- A one-pot reaction to synthesize two types of fluorescent materials containing benzothiazolyl moiety
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Two different types of fluorescent materials containing benzothiazolyl moiety, 2-(benzothiazol-2-yl)phenol derivatives and 3-(benzothiazol-2-yl) coumarin derivatives, were synthesized synchronously using ethyl cyanoacetate, appropriate aromatic aldehyde and 2-aminothiophenol as the starting materials under the catalysis of benzoic acid by one-pot reaction. This method has the advantages of mild reaction conditions, easy processing and low waste. All synthesized compounds were characterized by elemental analysis, IR, 1H NMR spectra. The structures of 2-(benzothiazol-2-yl)phenol derivatives, 2-(benzothiazol-2-yl)phenol (BTP) and 2-(benzothiazol-2-yl)naphthol (BTN), were determined by X-ray single crystal analysis. The UV-vis absorption and photoluminescence spectra of all synthesized compounds were investigated. The 2-(benzothiazol-2-yl)phenol derivatives exhibit bright green emissions and 3-(benzothiazol-2-yl)coumarin derivatives emit bright blue light in solutions.
- Yu, Tianzhi,Zhang, Chengcheng,Zhao, Yuling,Chai, Haifang,Fan, Duowang,Ma, Ying,Yao, Shanglei,Li, Wentao
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- Synthesis, crystal structure and photoluminescence of a cyclometalated iridium(III) coumarin complex
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In this paper a new cyclometalated iridium(III) coumarin complex, Ir(III)bis(3-(2-benzothiazolyl)coumarinato N,C4)(acetylacetonate) (Ir(L)2(acac)), was synthesized and characterized. X-ray crystallography demonstrated that the iridium(III) ion is hexacoordinated by two C atoms and two N atoms from 3-(2-benzothiazolyl)coumarinato ligands and two O atoms from acac ligand, displaying distorted octahedral coordination geometry. The Ir(L)2(acac) complex has good thermal stability with less than 2 % weight-reduction occurring at 300 C, and exhibits strong reddish orange emission. The results shown that Ir(L)2(acac) is useful for fabrication organic light-emitting diodes.
- Yu, Tianzhi,Zhang, Chengcheng,Zhao, Yuling,Guo, Shaoqiang,Liu, Peng,Li, Wentao,Fan, Duowang
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- The one-pot synthesis and fluorimetric study of 3-(2′-benzothiazolyl)coumarins
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A novel, piperidene-catalysed, one-pot synthesis of 3-(2′-benzothiazolyl)coumarins was undertaken, starting from salicylaldehydes, ethyl cyanoacetate and o-aminobenzenethiols in ethanol. Salicylaldehydes with electron-donating group gave optimum yields. The novel method is characterized by mild reaction conditions, simple procedure and low waste. All compounds were fluorescent in solution emitting either green light (490?nm) or blue light (440-460?nm). Two typical fluorescence peaks were found in the three-dimensional fluorescence spectra.
- Zhou, Shihai,Jia, Jianhong,Gao, JianRong,Han, Liang,Li, Yujin,Sheng, Weijian
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- Novel boronate probe based on 3-benzothiazol-2-yl-7-hydroxy-chromen-2-one for the detection of peroxynitrite and hypochlorite
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Derivatives of coumarin, containing oxidant-sensitive boronate group, were recently developed for fluorescent detection of inflammatory oxidants. Here, we report the synthesis and the characterization of 3-(2-benzothiazolyl)-7-coumarin boronic acid pinacol ester (BC-BE) as a fluorescent probe for the detection of peroxynitrite (ONOO– ), with high stability and a fast response time. The BC-BE probe hydrolyzes in phosphate buffer to 3-(2-benzothiazolyl)-7-coumarin boronic acid (BC-BA) which is stable in the solution even after a prolonged incubation time (24 h). BC-BA is slowly oxidized by H2O2 to form the phenolic product, 3-benzothiazol-2-yl-7-hydroxy-chromen-2-one (BC-OH). On the other hand, the BC-BA probe reacts rapidly with ONOO?. The ability of the BC-BA probe to detect ONOO– was measured using both authentic ONOO– and the system co-generating steady-state fluxes of O2?– and?NO. BC-BA is oxidized by ONOO– to BC-OH. However, in this reaction 3-benzothiazol-2-yl-chromen-2-one (BC-H) is formed in the minor pathway, as a peroxynitrite-specific product. BC-OH is also formed in the reaction of BC-BA with HOCl, and subsequent reaction of BC-OH with HOCl leads to the formation of a chlorinated phenolic product, which could be used as a specific product for HOCl. We conclude that BC-BA shows potential as an improved fluorescent probe for the detection of peroxynitrite and hypochlorite in biological settings. Complementation of the fluorescence measurements by HPLC-based identification of oxidant-specific products will help to identify the oxidants detected.
- Modrzejewska, Julia,Szala, Marcin,Grzelakowska, Aleksandra,Zak?os-Szyda, Ma?gorzata,Zielonka, Jacek,Podsiad?y, Rados?aw
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- Tailoring C-6-Substituted Coumarin Scaffolds for Novel Photophysical Properties and Stimuli-Responsive Chromism
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A judicious strategy was utilized to envision the substantial regio-positional effects of substituents on the photophysical properties of the 2H-chromen-2-one-3-benzothiazole scaffold-based push-pull framework, named 6-X-CUMs. Among them, 6-NEt2-CUM reveals prominent excited-state intramolecular charge transfer with a large change of dipole moment (?μ ~18.23 D), hence displaying remarkable emission solvatochromism from the green (536 nm in cyclohexane) to far-red region (714 nm in dimethyl sulfoxide) and a high-temperature sensitivity (-0.23 nm °C-1). These, together with unique basicity and acido-/vaporchromism upon acidification elucidated by NMR and photospectroscopic studies, show stark contrast to the conventional 7-NEt2-CUM. The new series of these tailored 6-X-CUMs represents a new dimension in tailoring the photophysical properties for the development of a promising class of multistimuli-responsive materials.
- Chen, Chao-Tsen,Chen, Deng-Gao,Chou, Pi-Tai,Lan, Yi-Cheng,Liu, Yi-Hung,Singh, Ravinder,Wang, Chun-Hsiang
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p. 11557 - 11565
(2021/10/25)
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- Chlorophyll-catalyzed photochemical regioselective coumarin C-H arylation with diazonium salts
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This communication describes the development of a mild method for the cross-coupling of the C3-position of coumarin with an array of diazonium salts mediated by chlorophyll as a biocatalyst via visible light catalysis. A natural pigment such as chlorophyll is used as a green photosensitizer and environmentally benign catalyst. This general and easy procedure provides a transition-metal-free alternative for the formation of 3-aryl coumarin derivatives at room temperature with good to excellent yields. This journal is
- Moazzam, Ali,Jafarpour, Farnaz
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supporting information
p. 16692 - 16696
(2020/10/27)
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- Alumina as a support and catalyst for the synthesis of benzothiazoles in solvent-free condition
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Arylbenzothiazole (4) and benzothiazolylcoumarins (5) were prepared by the condensation of 2-aminothiophenol (1) and hydroxybenzaldehydes (2) and 3-ethoxycarbonylcoumarinnin (3), respectively, in solvent- free condition. Of the solid support used,γ-Al2O3 demonstrated the best activity. Alinear regression line obtained from correlation between relative formation rate and Hammett constants with slope of 0.653 suggested that this condensation process is less sensitive to the substituents on the phenyl ring due to low efficacy of polarization in the solid state. In general, good yields (>80% yield) were obtained for the formation of 4. Conversely, yields of 5 were poor, because of γ-Al2O3 catalytic decomposition of 3 to form 2 (without P2O5) and coumarin (with P2O5).
- Ding, Mei-Fang,Chen, Chia-Pei,Lin, Shaw-Tao
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p. 645 - 649
(2013/10/22)
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- Direct C-H cross-coupling approach to heteroaryl coumarins
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A Pd-catalyzed direct cross-coupling of 3-bromocoumarins with heteroarenes provided an efficient route to synthesizing 3-heteroarylcoumarins. The reaction scope for the transformation was fairly broad, affording modest to good yields of various 3-heteroarylcoumarin scaffolds, which are privileged structures and prevalent motifs in many biologically active compounds and fluorophores. The Royal Society of Chemistry 2012.
- Min, Minsik,Kim, Bomi,Hong, Sungwoo
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experimental part
p. 2692 - 2698
(2012/04/23)
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- Three-component coupling using arynes and DMF: Straightforward access to coumarins via ortho-quinone methides
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ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner. The Royal Society of Chemistry 2011.
- Yoshida, Hiroto,Ito, Yu,Ohshita, Joji
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supporting information; experimental part
p. 8512 - 8514
(2011/09/16)
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- Efficient microwave-assisted synthesis of 3-benzothiazolo and 3-benzothiazolino coumarin derivatives catalyzed by heteropoly acids
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Heteropoly acids are reported as efficient catalysts for the microwave-assisted synthesis of 3-benzothiazolo and 3-benzothiazolino coumarin from o-aminothiophenol derivatives with 3-acetly and 3-cyanochromen-2-one in good to excellent isolated yields (73-95%). This study suggests new techniques for the synthesis of chromene derivatives using an inexpensive and easily available catalyst, a simple procedure, short reaction time, and good to excellent yields of the products.
- Khoobi,Ramazani,Foroumadi,Hamadi,Hojjati,Shafiee
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experimental part
p. 1036 - 1042
(2012/02/04)
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- Preparation and characterization of substituted 3-benzothiazol-2- ylcoumarins
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A series of substituted 3-benzothiazolylcoumarins was prepared from condensation of 2-hydroxybenzaldehyde and 2-cyanomethylbenzothiazole to investigate the effect of the nature and position of substituents on their absorption and fluorescent behavior. Com
- Chao, Richard Y.,Ding, Mei-Fang,Chen, Jhao-Yu,Lee, Chuan-Chen,Lin, Shaw-Tao
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p. 213 - 221
(2011/04/18)
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- 2-(1,3-Benzothiazol-2-yl)ethanethioamides in Heterocyclic Synthesis: Novel Synthesis of Pyridine, Pyridopyrimidine, Coumarin, Thiazolone and Triazole Derivatives
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The utility of 2-(1,3-benzothiazol-2-yl)ethanethioamide in the synthesis of several new pyridine, coumarin, pyridopyrimidine, thiazolone and triazole derivatives is reported.
- Elneairy, Mohamed A. A.,Abdel-Rahman, Taha M.,Hammad, Ahmed M.
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p. 2834 - 2849
(2007/10/03)
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- Simple and efficient one-pot preparation of 3-substituted coumarins in water
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3-Cyanocoumarin and seven derivatives [4-Me; 6-NO2; 7-OH; 7-OMe; 8-OH; 5,7-OMe; 6,7-(-CH=CH-)-2] and eight coumarins substituted at C-3 (CO2Et; NO2; Ph; p-NO2-C6H4; Ph-SO2; 2-pyridyl; 2-thienyl; 2-benzothiazolyl) were prepared, on multigram scale by a one-pot procedure in water alone, by the Knoevenagel reaction of o-hydroxyaryl aldehydes and o-hydroxyacetophenone with acetonitriles. The yields are high and the procedure does not require organic solvents. The reactions carried out in heterogeneous aqueous phase, sometimes in the presence of a surfactant, always have higher yields than the same reactions executed in homogeneous ethanolic medium.
- Brufola, Gianluca,Fringuelli, Francesco,Piermatti, Oriana,Pizzo, Ferdinando
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p. 1257 - 1266
(2007/10/03)
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- AN EFFICIENT ONE-POT SYNTHESIS OF 3-(2-BENZOTHIAZOLYL)COUMARINS
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Some 3-(2-benzothiazolyl)coumarin imines and 3-(2-benzothiazolyl)coumarins are prepared from 2-benzothiazolylacetonitrile and 2-hydroxybenzaldehydes in ethanol in the presence of catalytic amount of NaOH.
- Dryanska, Veneta
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p. 203 - 210
(2007/10/02)
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