γ‐Fe<sub>2</sub>O<sub>3</sub>@Cu<sub>3</sub>Al‐LDH/HEPES a novel heterogeneous amphoteric catalyst for synthesis of annulated pyrazolo[3,4‐d]pyrimidines
Farzaneh Ghobakhloo, Davood Azarifar, Masoud Mohammadi, Masoumeh Ghaemi
Abstract
An efficient synthetic method for the heterogenization of bifunctional zwitterionic HEPES catalyst on LDH modified γ‐Fe 2 O 3 magnetic nanoparticles (MNPs) was developed to create a novel polar catalytic environment for tandem catalysis. The efficiency of the resulted acid/base bifunctional catalyst (γ‐Fe 2 O 3 @Cu 3 Al‐LDH/HEPES) was investigated in Biginelli‐like synthesis of biologically active pyrazolo[3,4‐d]pyrimidines via the cyclocondensation of 3‐methyl, 1‐phenyl‐H1‐pyrazole‐5‐ol with various aromatic aldehydes and urea derivatives in a mixture of water and ethanol (1:1) under reflux conditions. Besides, the desired products were reached with high conversions and powerful reusability. Utilization of simple and mild reaction conditions, hybrid bifunctional catalytic groups, short reaction time, green and safe solvent, high catalytic performance and good recyclability, easy purification of the products, and simple magnetically work‐up make this methodology an interesting and effective option in the Biginelli reaction.