Synthesis of thiophene-pyrazole conjugates as potent antimicrobial and radical scavengers

Abstract

The current study presents the synthesis of thiophene-appended pyrazoles through 3+2 annulations of chalcones 3(a-g)with aryl hydrazine hydrochlorides 4(a-d) in acetic acid (30%) under reflux conditions produced the thiophene-pyrazole hybrids 5(a-g) in good yields. Structures of synthesized new pyrazoles were confirmed by spectral studies, and elemental analysis. Further, preliminary biological evaluation studies show that compounds 5b and 5f having chloro substitution only in the thiophene ring exhibited excellent inhibition (12.5-25.0 µg/mL) against all the tested organisms in comparison with that of the standard. Compounds, 5a, 5c and 5g having electronegative chloro substitutions each in the aromatic and thiophene rings showed excellent (12.423-31.213 µg mL-1) DPPH radical scavenging potencies. The synthesis of pyrazoline derivatives and the efficacy of some of the synthesized molecules as antimicrobial and antioxidant agents validate the significance of this study.

Keywords

• Antimicrobial
• Antioxidant
• Chalcone
• Cyclocondensation
• Radical scavengers