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Advisor(s)
Abstract(s)
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, giving an interesting fluorescent tetracyclic heteroaromatic
compound. The antimicrobial activity, the minimal
inhibitory concentrations (MICs) and the structure-activity
relationships (SARs) were evaluated. A selectivity with
low MICs was observed against Bacillus Cereus, and good
results were also obtained against Candida albicans. The acids
obtained by hydrolysis of the ester group, as non-proteinogenic
α,β-unsaturated β-amino acids, can be incorporated
into peptide chains to induce conformational constraints.
Description
Keywords
Amination Antimicrobial activity Benzothiophenes Diarylamines Fluorescence Palladium
Pedagogical Context
Citation
Queiroz, Maria João R.P.; Begouin, Agathe; Ferreira, Isabel C.F.R.; Kirsch, Gilbert; Calhelha, Ricardo C.; Barbosa, Sandra; Estevinho, Leticia M. (2004). Palladium-catalysed amination of electron-deficient or relatively electron-rich benzo[b]thienyl bromides - Preliminary studies of antimicrobial activity and SARs. European Journal of Organic Chemistry. ISSN 1434-193X. 2004:4, p. 3679-3685
Publisher
Wiley Intersicence