Chemo selective synthesis and antibacterial assessment of pyrazolo[3,4-d]pyrimidinones via a novel urea/thiourea-based ternary DES
摘要
Despite advancements in deep eutectic solvents (DESs), their parallel tri-functionalities as reagent, catalyst, and solvent are incredible. Herein, the new ternary DES ZnCl2:ChCl:2thiourea (TDES1) was prepared, characterized, and compared with its urea analog (TDES2) in the chemo selective synthesis of anti-bacterial pyrazolo[3,4 d]pyrimidin(thi)ones (PyrPys). Molecular interactions between ZnCl2, ChCl, and thiourea at mole ratios 1:1:2 resulted in a substantial decrease in melting points to 16 °C in TDES1 with density 1.21 g/cm3, electrical conductivity 33 µS/cm, and viscosity 2632 cP. Theoretical DFT and EPS analyses established complex ZnCl3-Ch+ as HBA interacted with thiourea’s NH2 and OH of ChCl as HBDs, which was supported by experimental XPS analysis. TDESs contain dual Zn2+ and thiourea/urea in a liquid homogeneous structure. These homogeneous TDESs were used as replacements for either urea/thiourea solid component, Lewis acid catalyst, or solvent in the chemo selective synthesis of bio-active PyrPys. Such multi-roles of TDESs are accountable for reaction promoting, minimizing the auxiliary substances, and chemo selectivity, even though with a higher selectivity for TDES2. Screening the in vitro antibacterial activities of the given PyrPys against Escherichia coli (E. Coli), Bacillus cereus (B. cereus), Staphylococcus aureus (S. Aureus), and Salmonella, confirmed excellent bioactivities for the vanillin derivatives.