The synthesis of 4,4´-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s using boric acid aqueous solution system

Bis(pyrazolyl)methanes (BPMs) including 4,4´-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s have a broad spectrum of approved biological activity, being usedas anti-inflammatory, antipyretic, gastric secretion stimulatory, antidepressant, antibacterial, and antifilarial agents [1]. 4,4´-(arylmethylene)-bis(3-methyl-1-phenyl- 1H-pyrazol-5-ol)s, were prepared by various methods including application of piperidine in ethanolic solution [2], tandem Knoevenagel-Michael reaction in benzene solutions [3], application of sodium dodecyl sulfate in aqueous media [4], and electrocatalytic synthesis [5]. Having above facts, we have reported the preparation of bis(pyrazolyl)methanes by the condensation reaction of phenylhydrazine, ethyl acetoacetate and aryl aldehydes in the presence of boric acid, at 70 °C under aqueous conditions as a mild and green reaction condition (Scheme 1).