Development Of Novel Thienopyrimidine Hybrids: Synthesis, Characterization And Multi-Target Biological Evaluation

A new array of thienopyrimidine-based Schiff bases, specifically 2-(2-(substitutedbenzylidene) hydrazinyl)-5,6- dimethylthieno[2,3-d] pyrimidin-4(3H)-one (4a–j), was prepared by a multistep convergent approach. Synthesis was initiated with a Gewald reaction involving ethyl methyl ketone, ethyl cyanoacetate, and elemental sulfur to afford ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate. Further cyclization with potassium thiocyanate gave the critical 2-mercaptothieno[2,3-d] pyrimidin4(3H)-one intermediate. The target Schiff bases were obtained by hydrazinolysis followed by acid-catalyzed condensation with diverse substituted aromatic aldehydes. All the newly synthesized compounds were fully characterized using melting point measurement, elemental analysis, FTIR, 1H NMR, 13C NMR, and mass spectrometry. This novel scaffold affords a highly privileged template aptly suited for biological assessments against multiple targets and medicinal chemistry studies