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| Abreu, Rui M.V.; Falcão, Soraia; Ferreira, Isabel C.F.R.; Queiroz, Maria João R.P.; Vilas-Boas, Miguel. |
| Cyclic voltammetry was used to evaluate the antioxidant activity of 7-aryl or 7-heteroarylamino-2,3-dimethylbenzo[b]thiophenes previously synthesized by some of us, comparing their oxidation potentials with those of the well-known synthetic standards (BHA, BHT). Compounds with electron-donating groups on the arylamine moiety have lower Ep/2 than compounds with electron-withdrawing groups or electron-deficient rings (pyridines). The position of the methoxy group on the arylamine moiety also changes the oxidation potential: lower Ep/2 for the diarylamines with methoxy groups in the para position. Comparing the first peak potential with the ones of BHA and BHT, the diarylamine compounds show lower oxidation potential, and therefore higher reducing power. A... |
| Tipo: Article |
Palavras-chave: Benzo[b]thiophene; Diarylamines; Antioxidant properties; Electrochemical assays. |
| Ano: 2009 |
URL: http://hdl.handle.net/10198/2717 |
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| Ferreira, Isabel C.F.R.; Queiroz, Maria João R.P.; Vilas-Boas, Miguel; Estevinho, Leticia M.; Begouin, Agathe; Kirsch, Gilbert. |
| The antioxidant properties of substituted diarylamines in the benzo[b]thiophene series were evaluated by their reducing power and free radical scavenging activity. The results were compared with those of standards: acid ascorbic for the first method and BHA and BHT for the second. For both methods it was possible to establish some structure–activity relationships (SARs) based on the position of the arylamination on the benzo[b]thiophene moiety, the presence of different substituents on the phenyl ring (F, 1 or 2 OMe) and on the thiophene ring (H, CO2Et, CO2H). |
| Tipo: Article |
Palavras-chave: Diarylamines; Benzothiophenes; Antioxidant activity; Structure–activity relationships. |
| Ano: 2006 |
URL: http://hdl.handle.net/10198/825 |
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| Queiroz, Maria João R.P.; Begouin, Agathe; Ferreira, Isabel C.F.R.; Kirsch, Gilbert; Calhelha, Ricardo C.; Barbosa, Sandra; Estevinho, Leticia M.. |
| Several diarylamines in the benzo[b]thiophene series were prepared in good to high yields by palladium-catalysed amination of ethyl 3-bromobenzo[b]thiophene-2-carboxylate with anilines and 5-aminoindole in the presence of Pd(OAc)2, BINAP and Cs2CO3 in toluene. The presence of the ester group at the 2-position of the benzo[b]thiophene moiety increases the yields and lowers the heating times relative to the reactions performed with 3-bromobenzo[b]thiophene. When aminopyridines were used instead of anilines, the ligand and the solvent need to be changed to XANTHPHOS and dioxane in the amination reaction. With 2-aminopyridine a onepot C−N coupling and intramolecular cyclization involving the nitrogen atom of the pyridine ring occurred, with loss of ethanol,... |
| Tipo: Article |
Palavras-chave: Amination; Antimicrobial activity; Benzothiophenes; Diarylamines; Fluorescence; Palladium. |
| Ano: 2004 |
URL: http://hdl.handle.net/10198/820 |
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| Queiroz, Maria João R.P.; Ferreira, Isabel C.F.R.; Calhelha, Ricardo C.; Estevinho, Leticia M.. |
| New 7-aryl or 7-heteroarylamino-2,3-dimethylbenzo[b]thiophenes were prepared by palladium-catalyzed Buchwald–Hartwig cross-coupling of 7-bromo or 7-amino-2,3-dimethylbenzo[b]thiophenes, previously prepared by us, with substituted (4-methoxy or 3,4-dimethoxy) anilines and 3-aminopyridine or with substituted (3-methoxy or 4-cyano) bromobenzenes and 2-bromopyridine, respectively, using Pd(OAc)2, rac-BINAP or Xantphos as ligands, and Cs2CO3 as base. Their antioxidant properties were evaluated by several methods: reducing power, scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, inhibition of erythrocyte hemolysis and inhibition of lipid peroxidation using the b-carotene linoleate system. EC50 values for all the methods were determined and it... |
| Tipo: Article |
Palavras-chave: Diarylamines; Benzo[b]thiophenes; Buchwald–Hartwig coupling; Antioxidant activity. |
| Ano: 2007 |
URL: http://hdl.handle.net/10198/839 |
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| Ferreira, Isabel C.F.R.; Queiroz, Maria João R.P.; Kirsch, Gilbert. |
| Diarylamines in the benzo[b]thiophene series bearing electron donating or withdrawing groups, were prepared by Buchwald– Hartwig C–N coupling in moderate to high yields. The conditions used were Pd(OAc)2 (3 mol%), BINAP as ligand (4 mol%) and Cs2CO3 as base (1.4 equiv.), in toluene at 1008C, being 6-bromo or amino benzo[b]thiophenes coupled, respectively, with substituted anilines or phenylbromides. The 6-aminobenzo[b]thiophene derivatives were also prepared by palladium catalyzed C–N coupling of the corresponding 6-bromo compounds with benzophenone imine, followed by acidic hydrolysis of the imino derivatives. When 4-nitrobromobenzene and 4-bromobenzonitrile were used as coupling components, triarylamines were also isolated in small amounts. The presence... |
| Tipo: Article |
Palavras-chave: Buchwald–Hartwig coupling; Palladium; Amination; Diarylamines; Benzo[b]thiophenes. |
| Ano: 2003 |
URL: http://hdl.handle.net/10198/818 |
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| Ferreira, Isabel C.F.R.; Calhelha, Ricardo C.; Estevinho, Leticia M.; Queiroz, Maria João R.P.. |
| Gram positive (Bacillus cereus, B. subtilis), Gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria, and Candida albicans as a representative of fungi were used for screening the in vitro antimicrobial activity of diarylamines in the 2,3,5-trimethylbenzo[ b]thiophene series bearing different substituents, synthesized by us using the palladium-catalyzed C–N coupling methodology. The minimal inhibitory concentration (MIC) and structure–activity relationships (SARs) were evaluated. |
| Tipo: Article |
Palavras-chave: Diarylamines; Antimicrobial activity; SAR; Benzothiophenes. |
| Ano: 2004 |
URL: http://hdl.handle.net/10198/821 |
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