Synthesis and antitumor activity of novel pyridazinone derivatives containing 1,3,4-thiadiazole moiety

Abstract

A series of novel pyridazinone derivatives containing the 1,3,4-thiadiazole moiety were synthesized and characterized by 1H NMR, 13C NMR, spectroscopies HRMS and IR. Among them, the structure of compound 5c (2-(Tert-butyl)−4-chloro-5-((5-((2-ethylphenyl)amino)−1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One) was unambiguously confirmed via single crystal X-ray diffraction analysis. The inhibitory activity of all the target compounds against MGC-803 and Bcap-37 was determined by MTT assay, with doxorubicin (the inhibition rates were 95.5 ± 0.4% and 95.7 ± 1.0% respectively) as a control. The preliminary results showed that the inhibitory activity of compound 5n (2-(Tert-butyl)−4-chloro-5-((5-((3-fluorophenyl)amino)−1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One) was superior to the others. The inhibition rates of MGC-803 and Bcap-37 cells were 86.3 ± 2.2% and 92.3 ± 0.6% at a concentration of 10 μmol/L, respectively. The preliminary structure-activity relationship showed that when the 2-position of the benzene ring was substituted by a methyl group, such as compound 5j (2-(Tert-butyl)−4-chloro-5-((5-((2,3-dimethylphenyl)amino)−1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One), it exhibited good anticancer activity on MGC-803 cells. Besides, introducing fluorine, chlorine, or trifluoromethyl group onto the benzene ring, such as compound 5 m (2-(Tert-butyl)−4-chloro-5-((5-((4-(trifluoromethoxy)phenyl)amino)−1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One), displayed good anticancer activity on MGC-803 and Bcap-37 cells.