What question did this study set out to answer?

The aim is to evaluate the antibacterial activity of pyrazolo[3,4-d]pyrimidinones synthesized using novel deep eutectic solvents.

July 14, 2026Open Access

Chemo selective synthesis and antibacterial assessment of pyrazolo3,4-dpyrimidinones via a novel urea/thiourea-based ternary DES

FTFatemeh TamaddonYazd University ZRZahra RahimiYazd University EAEhsan Ahmadi‐AhmadAbadiYazd University

Key Points

The aim is to evaluate the antibacterial activity of pyrazolo[3,4-d]pyrimidinones synthesized using novel deep eutectic solvents.
Developed and characterized two ternary DESs: ZnCl2:ChCl:2thiourea (TDES1) and urea-based (TDES2).
Conducted in vitro antibacterial testing against four bacteria including E. coli and S. aureus.
Utilized DFT and EPS analyses to understand molecular interactions in synthesizing bio-active compounds.
TDES1 exhibited a notable decrease in melting points to 16 °C and had a density of 1.21 g/cm3.
Antibacterial screening showed vanillin derivatives had excellent activity against selected bacterial strains.
TDES2 demonstrated higher selectivity in chemo selective synthesis compared to TDES1.

Abstract

Despite advancements in deep eutectic solvents (DESs), their parallel tri-functionalities as reagent, catalyst, and solvent are incredible. Herein, the new ternary DES ZnCl 2 :ChCl:2thiourea (TDES1) was prepared, characterized, and compared with its urea analog (TDES2) in the chemo selective synthesis of anti-bacterial pyrazolo3,4 d pyrimidin(thi)ones (PyrPys). Molecular interactions between ZnCl 2 , 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/cm 3 , electrical conductivity 33 µS/cm, and viscosity 2632 cP. Theoretical DFT and EPS analyses established complex ZnCl 3 - Ch + as HBA interacted with thiourea’s NH 2 and OH of ChCl as HBDs, which was supported by experimental XPS analysis. TDESs contain dual Zn 2+ 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.

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