Silica vanadic acid (oxo-vanadium has been supported on silica) with Lewis and Bronsted acid site is introduced as an efficient, reusable, and heterogeneous catalyst for tandem Knoevenagel–Michael reaction of two equivalents of 5-methyl-2-phenyl-2, 4-dihydro-3H -pyrazol-3-one with various aromatic aldehydes for the synthesis of 4, 4?- (arylmethylene) bis (1 H -pyrazol-5-ol) s at room temperature. The present methodology offers several advantages over existing methodologies, such as excellent yields, short reaction time, simple procedure, easy work-up, mild reaction conditions, and synthesis of wide range of products. This procedure gave the products in excellent yields within very short reaction times over other vanadium (V) compounds. Also this catalyst can be reused six times without appreciable loss of its catalytic activity.
