Meglumine‐based Sustainable Three‐component Deep Eutectic Solvent Applicable for the Synthesis of Pyrazoloquinazoline‐3‐carboxylates as a Sensing Probe for Cu2+ Ions

An unprecedented meglumine‐based three‐component deep eutectic solvent (3c‐DES) (MegPAc) was synthesized using meglumine, p‐toluenesulfonic acid (PTSA), and acetic acid as a renewable, and non‐toxic solvent. The exploitation of the MegPAc as an eco‐friendly reaction media to construct a selective and sensitive small organic molecular sensing probe, namely, pyrazolo[5,1‐b]quinazoline‐3‐carboxylates (PQCs) was executed. Captivatingly, the MegPAc served the dual role of solvent and catalyst, and it delivered the title components with 69–94 % yields within 67–150 minutes. Furthermore, a UV‐visible study unfolds the selective detection of Cu2+ ions with our synthetic probe 4 ba and resulted in hypsochromic shift due to electrostatic interactions. Additionally, 1H NMR titration study and density functional theory (DFT) calculations were performed to attest the binding mechanism of sensing probe 4 ba and Cu2+ ions. Worthy of mention, this protocol unveils the efficacy of meglumine‐based 3c‐DES for the first time as a bio‐renewable system to synthesize the PQCs.