Design, Synthesis, Antibacterial, and Antifungal Evaluation of a New Series of Quinazoline—Thiazole and /or Quinazoline—Triazole Hybrids as Bioactive Heterocycles

Herein, a one‐pot reaction between cyclohexanone, thiourea, and 2,5‐dimethoxybenzaldehyde allowed to prepare hexahydroquinazoline‐2(1H)‐thione 4 firstly, which dollowed by reacting with hydrazine hydrate to produce the corresponding 2‐hydrazinylhexahydroquinazoline 6. Interesting analogs of thiazolo3,2‐aquinazoline 7‐13 where obtained when hexahydroquinazoline‐2(1H)‐thione 4 reacted with 1,2‐dibromoethane, chloroacetyl chloride, bromoacetic acid, bromoacetic acid/4‐chlorobenzaldehyde, 2‐bromopropionic acid, ethyl bromocyanoacetate, and/or bromomalononitrile; respectively. While triazolo4,3‐a quinazoline 14‐16 were created when 2‐hydrazinylhexahydroquinazoline 6 reacted with triethyl orthoformate, acetic anhydride, and carbon disulfide respectively. Additionally, the new analogs were examined for their antibacterial and antifungal properties against Escherichia coli, Staphylococcus aureus, and Candida albicans. It was discovered that triazolo4,3‐a quinazoline analogs 14‐16 have superior bacterial and fungal activity when compared to the corresponding conventional doses of Streptomycin and Griseofulvin. Towards Candida albicans; compounds 14, 15, and 16 increase activity with 1.14%, 1.15%, and 1.21%, respectively more than griseofulvin.While, for Staphylococcus aureus; compounds 14, 15, and 16 increase activity with 1.5%, 1.5%, and 1.7%, respectively more than streptomycin. Morever, for Escherichia coli; compounds 14, 15, and 16 increase activity with 1.19%, 1.21%, and 1.22%, respectively more than streptomycin. Finally, structure activity relationships show that quinazoline derivatives exhibit higher activity when fused to pyrazole ring 14–16 as compared when fused thiophene ring 7–13.