Synthesis of two novel series of azoaldonitrones and preliminary evaluation of their antibacterial activity

Abstract

In this work two series of new azoaldonitrones have been synthesized. At first, azoaldehydes
[A1-A10] were prepared via coupling reactions between the diazonium salts of the primary
aromatic amines (2-amino-5-mercapto-1,3,4-thiadiazole, 3-aminopyridine,4-methoxyaniline,
2,4-dichloroaniline, 4-chloroaniline, 2-chloroaniline, 3-bromoaniline, 3-nitroaniline, 4-
nitroaniline and benzidine, respectively) and alkaline solution of 2-hydroxybenzaldehyde as
coupling reagent. Next, the resulting azoaldehydes [A1-A10] were introduced in acid-catalyzed
condensation reactions with N-phenylhydroxylamine in absolute ethanol to obtain ten new
azoaldonitrones [N1-N10] respectively. Later, treatment of azoaldehydes [A1-A5] with Nbenzylhydroxylamine
under the same conditions afforded five new azoaldonitrones [A11-A15]
respectively. The structures of the synthesized azoaldonitrones were confirmed by (C.H.N.S.)
elementary analysis and the spectroscopic methods including FT-IR and 1H NMR. The
synthesized azoaldonitrones [N1-N15] were tested for their antibacterial activity against two
pathogenic strains of bacteria Staphylococcus aureous (Gram-positive) and Escherichia coli
(Gram-negative). The results revealed that azoaldonitrones [N1] and [N11] which are containing
thiadiazole moiety showed higher activity against both strains of bacteria, while compound [N6]
appeared higher activity only against Gram-positive bacteria. Moreover, most of the prepared
azoaldonitrone compounds showed medium activity against Gram-positive bacteria and weak
activity against Gram-negative bacteria.