Synthesis of 4,4-(arylmethylene)bis(1H-pyrazol-5-ols) via multi-component reactions by using silica-bonded sulfamic acid derivatives

The one-pot, multi-component synthesis of 4,4-(arylmethylene)bis(1H-pyrazol-5-ols) by tandem Knoevenagel-Michael reaction of phenylhydrazine, ethyl acetoacetate and aldehydes in the presence of silica-bonded N-propylpiperazine sulfamic acid (SBPPSA) as a recyclable solid acid catalyst was reported. SBPPSA showed much the same efficiency when used in consecutive reaction runs