P-Toluenesulfonic acid-catalyzed solvent-free synthesis and biological evaluation of new 1-(4′,6′-dimethylpyrimidin-2′-yl)-5-amino-4H-3-arylpyrazole derivatives

Abstract

A solvent-free quick synthesis of 1-(4′,6′-dimethylpyrimidin-2′-yl)-5-amino-4H-3-arylpyrazoles (3) was accomplished by grinding 2-hydrazino-4,6-dimethylpyrimidine (1) and β-ketonitriles (2) in the presence of p-Toluenesulfonic acid as a catalyst. Subsequently, 5-aminopyrazoles (3) were converted to their corresponding N-acetamide (4) and N-trifluoroacetamide (5) derivatives by treating (3) with acetic anhydride/acetic acid and trifluoroacetic anhydride/trifluoroacetic acid, respectively. The newly synthesized compounds were fully characterized using IR, NMR (1H, 13C, and 19F), mass spectral studies, and elemental analyses. All of the fifteen compounds were screened for their in vitro antibacterial activity against two Gram-positive and two Gram-negative pathogenic bacteria such as Bacillus pumilus, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, respectively. Additionally, nine of these compounds were screened for their cytotoxicity against the human Caucasian promyelocytic leukemia (HL-60) cell line using the alamarBlue® assay. Preliminary results reveal that compounds 3a, 3b, 3d, 5a, and 5d are showing moderate-to-significant cytotoxic and antibacterial activity.