A new bifunctional heterogeneous nanocatalyst for one-pot reduction-Schiff base condensation and reduction–carbonylation of nitroarenes

Abstract

In this work, synthesis of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H and its activity as a bifunctional heterogeneous nanocatalyst containing Pd–NHC and acidic functional groups, are described. This newly synthesized nanomagnetic catalyst is fully characterized by different methods such as FT-IR, XPS, TEM, VSM, ICP and TG analysis. At first, the catalytic activity of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H is evaluated for the reduction of nitroarenes in aqueous media using NaBH₄ as a clean source of hydrogen generation at ambient temperature. Using the promising results obtained from the nitroarene reduction, this catalytic system is used for two one-pot protocols including reduction-Schiff base condensation and reduction–carbonylation of various nitroarenes. In these reactions the in situ formed amines are further reacted with aldehydes to yield imines or carbonylated to amides. The desired products are obtained in good to high yields in the presence of Pd–NHC-γ-Fe₂O₃-n-butyl-SO₃H as a bifunctional catalyst. The catalyst is reused with the aid of a magnetic bar for up to six consecutive cycles without any drastic loss of its catalytic activity.