A Green and Efficient One-Pot Pseudo-Five-Component Reaction for Synthesis of Bis(pyrazol-5-ol) Derivatives via Tandem Cyclocondensation-Knoevenagel-Michael Reaction

A simple, green and efficient approach for one-pot pseudo-five-component synthesis of the 4,4'-(arylmethylene) bis(1H-pyrazol-5-ol) derivatives from hydrazines, dialkyl acetylenedicarboxylats/beta-ketoesters and aromatic aldehydes catalyzed by Dabco-base ionic liquids in aqueous media has been successfully developed. All the reactions were performed under 3 mol% of ionic liquid catalyst, and afforded the corresponding bis(pyrazol-5-ol)s in excellent yields (81-98 %). This method also offers several other notable advantages, such as environmental friendliness, short reaction times, easy workup and reusability of the inexpensive catalyst.