Sodium dodecyl benzene sulfonate-catalyzed reaction for green synthesis of biologically active benzylpyrazolyl-coumarin derivatives, mechanism studies, theoretical calculations

Abstract

In the present work, a multicomponent protocol has been described for the synthesis of various benzylpyrazolyl-coumarin 5a-i structures, involving the reaction of 4-hydroxycoumarin, ethyl acetoacetate, hydrazine hydrate, and aldehydes, using an ethanol-water (1:1) mixture as the reaction medium and sodium dodecylbenzenesulfonate (SDBS) as the catalyst. This new approach has advantages such as short reaction time, recovery of the catalysts after the catalytic reaction and their reuse without loss of activity, as well as the lightening of the process. The structures of the obtained benzylpyrazolylcoumarins were determined and confirmed by melting point, 1H NMR and 13C NMR. The determination of antioxidant activity of the obtained benzylpyrazolylcoumarin 5a-i derivatives was studied using the DPPH scavenging assay. Molecular modeling studies using DFT (density function theory) calculations showed that there are six tautomeric structures A to F in which structure C is more stable than the others.