New pyrazolone derivatives synthesis: comparison of the catalytic effect of three typically different Brønsted acid catalysts on the reaction progression

Via the one-pot condensation reaction of ethyl acetoacetate, aromatic aldehydes, 2,4-dinitrophenylhydrazine, and β-naphthol; new pyrazolone derivatives were synthesized in the presence of three Brønsted acid catalysts. These Brønsted acid catalysts are Silica sulfuric acid (SSA), tetra-n-butyl ammonium hydrogen sulfate (TBAHSO4) and [2,2′-Bipyridine]-1,1′-diium tricyanomethanide {[2,2′-BPyH][C(CN)3]2}. Each of these combinations has its own characteristics. SSA is a heterogeneous catalyst. TBAHSO4 is a phase transfer catalyst and {[2,2′-BPyH][C(CN)3]2} is an ionic liquid. We compared the obtained results of these catalysts. In most cases, the results were comparable. But, sometimes TBAHSO4 and {[2,2′-BPyH][C(CN)3]2} give the better results to the SSA in term of reaction time and yields. Even though, isolation of SSA from products was easier than the separation of two other catalysts.