Phosphomolybdic Acid: An Efficient and Recyclable Solid Acid Catalyst for the Synthesis of 4,4′-(Arylmethylene)bis(1H-pyrazol-5-ols)

Abstract

An efficient and environmentally friendly method has been developed for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) by condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone in the presence of phosphomolybdic acid as a recyclable catalyst in ethanol at ambient temperature in excellent yields.

GRAPHICAL ABSTRACT

Keywords:

• Aromatic aldehydes
• bispyrazole
• catalysis
• 3-methyl-l-phenyl-5-pyrazolone
• phosphomolybdic acid

ACKNOWLEDGMENTS

The author is thankful to SAIF, Indian Institute of Technology, Mumbai, for providing the spectral facility and the University Grants Commission for providing a research fellowship.

Notes

^a Reaction conditions: Benzaldehyde (0.01 mol), 3-methyl-l-phenyl-5-pyrazolone (0.02 mol), phosphomolybdic acid (10 mol%), and solvent (5 vol).

^b Yield: isolated.

^a Reaction conditions: benzaldehyde (0.01 mol), 3-methyl-l-phenyl-5-pyrazolone (0.02 mol), phosphomolybdic acid (mol%), and solvent (5 vol).

^b Yield: isolated.

^a Reaction condition: aldehyde (0.01 mol), 3-methyl-1-phenyl-5-pyrazolone (0.02 mol), phosphomolybdic acid (10 mol%), and ethanol (5 vol) at rt.

^b Yield: isolated.