Synthesis, antibacterial, and antioxidant evaluation of novel series of condensed thiazoloquinazoline with pyrido, pyrano, and benzol moieties as five-and six-membered heterocycle derivatives

A novel synthesis of thiazolo[2,3-b]quinazolines 4(a–e), pyrido[2^′,3^′:4,5]thiazolo[2,3-b] quinazolines {5(a–e), 6(a–e), and 7(a–e)}, pyrano[2^′,3^′:4,5]thiazolo[2,3-b]quinazolines 8(a–e), and benzo[4,5]thiazolo[2,3-b]quinazoloine9(a–e) derivatives starting from 2-(Bis-methylsulfanyl-methylene)-5,5-dimethyl-cyclohexane-1,3-dione 2 as efficient α,α dioxoketen dithioacetal is reported and the synthetic approaches of these types of compounds will provide an innovative molecular framework to the designing of new active heterocyclic compounds. In our study, we also present optimization of the synthetic method along with a biological evaluation of these newly synthesized compounds as antioxidants and antibacterial agents against the bacterial strains, like S. aureus, E. coli, and P. aeruginosa. Among all the evaluated compounds, it was found that some showed significant antioxidant activity at 10 µg/mL while the others exhibited better antibacterial activity at 100 µg/mL. The results of this study showed that compound 6(c) possessed remarkable antibacterial activity, whereas compound 9(c) exhibited the highest efficacy as an antioxidant. The structures of the new synthetic compounds were elucidated by elemental analysis, IR,¹H-NMR, and¹³C-NMR.