BPBSBDM as an influential Brønsted acidic ionic liquid catalyst in preparing bis(pyrazolyl)methanes under mild conditions

At first, 1,4-Bis(pyridinium bi-sulfonic acid)benzene dimethylsulfonate (BPBSBDM), as a new Brønsted acidic ionic liquid (BAIL), is efficiently synthesized and revealed utilizing FT-IR (Fourier-transform infrared spectroscopy), TGA (thermogravimetric analysis), ¹³C NMR, ¹H NMR and Mass data. Subsequently, its catalytic activity was studied in preparing bis(pyrazolyl)methane derivatives through the one-pot multicomponent coupled domino reactions (MCDRs) among 1 mmol aldehydes (aryl, heteroaryl, or alkyl aldehydes), 2 mmol ethyl acetoacetate, and 2 mmol phenylhydrazine/hydrazine hydrate under optimal conditions (50 °C, solvent-free, and 4 mol% of BPBSBDM) in high yields (89–98%), and in short times (2–7 min). Our protocol has the advantages of reasonable turnover number (TON: 22.25 to 24.50) and turnover frequency (TOF: 3.17 to 12.25 min⁻¹) values, high yields of products, non-metallic nature of the catalyst, short reaction times, eco-friendly and economy, easy recyclability and good reproducibility. In addition, three derivatives 8a, 9a and 10a were synthesized and fully identified for the first time.