Ten variously substituted derivatives (IVa–j) of 4′(quinazol‐4‐on‐3‐yl) azobenzene were prepared. The effects of the nature and orientation of the substituents on the colour and dyeing properties of these dyes on polyester and acrylic fibres were evaluated.
3‐(1H‐Indol‐3‐yl)‐1H‐pyrazol‐5‐amine 3 was prepared in a quantitative yield by heating 3‐(1H‐indol‐3‐yl)‐3‐oxopropanenitrile 2 in dry ethanol with hydrazine hydrate, and utilized as key intermediate for the synthesis of some new pyrazolo[1,5‐a]pyrimidines and pyrazolo[5,1‐c]triazines. Structures of the newly synthesized compounds were established by elemental analysis and spectral data and evaluated as antioxidant agents. Most of the tested compounds belonging to the pyrazolo[1,5‐a]pyrimidine series exhibited better activities than members of the pyrazolotriazine one.
3‐Methyl‐1‐thiocarbamoyl‐2‐pyrazolin‐5‐one has been utilized as a core for the synthesis of some 1‐(thiazol‐2‐yl)‐pyrazolin‐5‐one derivatives through diazo‐coupling reaction and/or Knoevenagel condensation followed by heterocyclization with some α‐halogenated reagents such as bromoacetone, phenacyl bromide, and ethyl bromoacetate. Base prompted addition of the core compound to an equimolar amount of phenyl isothiocyanate furnished 3‐methyl‐4‐phenylthiocarbamoyl‐1‐thiocarbamoyl‐2‐pyrazolin‐5‐one which undergoes heterocyclization with α‐halogenated reagents at the more reactive phenylthiocarbamoyl moiety to afford the corresponding 4‐(thiazol‐2‐yl)‐1‐thiocarbamoyl‐2‐pyrazolin‐5‐ones. The new synthesized thiazolyl–pyrazolone compounds were evaluated for their potential antioxidant activity by using (ABTS Radical Cation Decolorization Assay).
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