Design, synthesis, biological evaluation and molecular docking study based on novel fused pyrazolothiazole scaffold

3-(Pyridin-3-yl)-1-p-tolyl-1H-pyrazolo[3,4-d]thiazol-5-amine was used as a key synthon for a one-pot two- and three-component synthesis of new fused heterocyclic moieties as pyrazolo[3,4-d]thiazole derivatives containing new fused ring pyrimidines or imidazoles. The compounds were synthesized by using microwave irradiation as an eco-friendly technique besides the conventional heating. All the newly synthesized compounds were characterized on the basis of their physical, spectral and analytical data. Most of the synthesized compounds were evaluated for their in vitro antimicrobial potentialities and antioxidant activities, and the most promising compounds were selected to determine antitumor activity. Molecular docking was performed inside the active site of cathepsin D, and target compounds 5a–c had a good binding energy of − 16.87 to − 11.64 kcal/mol compared to that of original ligand of − 16.02 kcal/mol with different binding interactions, thereby suggesting that these compounds may possibly act as cathepsin D inhibitors and thus may participate in anticancer activity.