title: Synthesis and antioxidant activity evaluation of new 7-aryl or 7-heteroarylamino-2,3-dimethylbenzo[b]thiophenes obtained by Buchwald-Hartwig C-N cross-coupling.
abstract: 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 beta-carotene linoleate system. EC50 values for all the methods were determined and it was possible to establish some structure-activity relationships (SARs) based on the presence and position of different substituents on the phenyl ring (1 or 2 OMe and CN), on the presence of a pyridine ring and on the position of its nitrogen atom relative to the N-H bond.
authors.affiliation: Centro de Química, Campus de Gualtar, Universidade do Minho, 4710-057 Braga, Portugal. mjrpq@quimica.uminho.pt
authors.forename: Maria-João R P
authors.initials: MJ
authors.lastname: Queiroz
authors.forename: Isabel C F R
authors.initials: IC
authors.lastname: Ferreira
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Calhelha
authors.forename: Letícia M
authors.initials: LM
authors.lastname: Estevinho
mesh_terms: D000975:Antioxidants / Q000138:chemical synthesis* / Q000494:pharmacology*; D003432:Cross-Linking Reagents; D016166:Free Radical Scavengers / Q000138:chemical synthesis; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D015227:Lipid Peroxidation / Q000187:drug effects; D013329:Structure-Activity Relationship; D013876:Thiophenes / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D003432:Cross-Linking Reagents; D016166:Free Radical Scavengers; D013876:Thiophenes