Hantzsch synthesis of 1,4-dihydropyridine derivatives over ZnO/ZrO2 catalyst under solvent free condition
Hantzsch synthesis of 1,4-dihydropyridine derivatives is accomplished using novel and efficient ZnO/ZrO2 catalyst. The catalysts prepared by facile precipitation and wet impregnation method have been characterized by using techniques like XRD, SEM, EDS, UV-diffuse reflectance spectra, FTIR, XPS, BET surface area. Ex situ Pyridine absorption FTIR spectroscopy is used to determine the Bronsted and Lewis acidic sites. Enhanced activity of the zirconia supported zinc catalyst is attributed to tetragonal phase, more acidic sites and high surface area of the catalyst. The products attained in good to excellent yields in short duration under solvent free condition, minimizing the disposal problem and energy dissipation. The catalyst can be reused umpteen times without significant loss in activity.
Hantzsch synthesis; green protocol; zirconia supported zinc; tetragonal phase; 1,4-dihydropyridines
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