ABSTRACT
This study presents a new environmentally sustainable catalytic method for the synthesis of symmetrically substituted pyridine derivatives and substituted alkene derivatives using zinc phosphate (Zn3(PO4)2·4H2O) as a non-toxic and green heterogeneous catalyst. The catalytic support was prepared by a co-precipitation method, and it was applied for the first time as a heterogeneous catalyst in organic synthesis. Trisubstituted pyridine derivatives were prepared with excellent yields (82-94%) via a three-component, one-pot synthesis of aromatic aldehydes, substituted acetophenones, and ammonium acetate in the presence of 0.4 mol% of Zn3(PO4)2·4H2O using an ethanol/water (4/1) mixture as the solvent, while substituted alkenes were synthesized with up to 90% yield using the prepared catalyst. The experimental results demonstrate the efficiency of these new catalytic syntheses that present various advantages such as short reaction times, excellent yields, and an environmentally friendly profile.
ABSTRACT
In this work, we have developed a simple and very effective experimental strategy for the reaction of Knoevenagel via the condensation of aromatic aldehydes substituted with active methylene compounds in the presence of hybrid nanocomposites xMCl2-yNaPO3 (MCl2 = 2,2'-dibenzimidazolyl butane dichlorhydrates), under ecological conditions. The Phosphate-Benzimidazole hybrid nanocomposite as heterogeneous catalysts has demonstrated a high catalytic activity for the Knoevenagel condensation in ethanol as an ecological solvent. It has several advantages such as light reaction conditions, a simple and ecological working procedure. Meanwhile, xMCl2-yNaPO3 can be recovered by simple filtration and this catalytic system having an interesting lifetime (five cycles) with no decrease in activity.
