Abstract An innovative, eco-friendly, and effective approach was established for synthesizing derivatives of 3,3,6,6-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione (2a-2j) through a one-pot, multicomponent reaction involving dimedone and diverse substituted benzaldehydes. The reactions were catalyzed by magnesium oxide nanoparticles (MgO-NPs) derived from coconut seed coat ash (CSCA), prepared using a modified procedure. Among several investigated synthetic approaches, including conventional heating, microwave irradiation, solvent-free grinding, and ionic liquid catalysis, the MgO@CSCA-mediated protocol in aqueous ethanol proved most efficient, affording high product yields (81.14–89.88%) within short reaction times (as low as 10 min). Structural elucidation of the synthesized compounds was achieved through FTIR, 1H and 13C NMR spectroscopy, HRMS, and elemental analysis. The inclusion of electron-withdrawing and electron-donating groups on the aryl ring significantly affected the spectral characteristics and reaction rates. Comparative catalyst screening revealed that MgO@CSCA-NPs outperformed conventional acidic and heterogeneous systems in terms of yield, rate, and reusability, with successful recyclability over five consecutive cycles. These findings highlight the significant potential of biogenic MgO@CSCA nanocatalysts for sustainable organic synthesis and reinforce their utility in the rapid generation of pharmacologically promising xanthene scaffolds under eco-friendly conditions.
Nirwan et al. (Tue,) studied this question.