One–pot A3–coupling solvent–free synthesis of propargylamines by Pd–impregnated Al–based LDHs synthesized from aluminum salt slag

Several Al³⁺–based LDHs with different divalent cations have been synthesized by coprecipitation from aluminum salt slag and have been impregnated with Pd. After their characterization by PXRD, FT–IR, thermal analysis, N₂ adsorption–desorption isotherms at –196 °C and electron microscopy (SEM and TEM), they were used as heterogeneous catalysts in the A³–coupling reaction (benzaldehyde + morpholine + phenylacetylene) to produce propargylamines. The catalyst that showed the best results was NiAl–Pd and the optimal reaction conditions were: catalyst dose 30 mg, temperature 80 °C and reaction time 6 h. In addition, this catalyst showed a good cyclic behavior, retaining a catalytic activity higher than 80 % after 4 cycles.