Comparative Study of Microwave-assisted and Conventional Synthesis of 3-[1-(s-phenylimino) Ethyl]-2H-chromen-2-ones and Selected Hydrazone Derivatives

In this study, 3-acetylcoumarin 1, used as the essential precursor was synthesized by the reaction of salicyaldehyde with ethyl acetoacetate in the presence of a catalytic amount of piperidine in solvent-free medium. Schiff bases 2-9 were obtained by the condensation reaction of 3-acetylcoumarin, 1 with various aniline derivatives while reaction of 3-hydrazinoquinoxalin-2-one with four different 6-susbtituted 3-acetylcoumarins afforded the corresponding hydrazones 10-13. Both Schiff bases and hydrazone products were synthesized under microwave irradiation method and conventional synthetic strategy for comparative study. The microwave assisted reaction was remarkably successful and gave both Schiff bases and hydrazones in higher yields at shorter reaction time compared to conventional heating method. The characterization of the synthesized compounds were structurally confirmed by analytical data as well as spectroscopic means which involved 1H-and 13C-nmr, ir, UV-visible and mass spectra.