Aspirin: an efficient catalyst for synthesis of bis (pyrazol-5-ols), dihydropyrano[2,3-c]pyrazoles and spiropyranopyrazoles in an environmentally benign manner

Abstract

This article aimed to present two facile and environmental friendly routes for the rapid assembly of biologically active compounds including pyrazol core using aspirin as a novel and green catalyst. The synthesis of bis(pyrazol-5-ol) derivatives was developed via one-pot, pseudo-five-component condensation, and the target dihydropyrano[2,3-c]pyrazoles and spiropyranopyrazoles were prepared by one-pot, four-component reaction. These reactions can be performed in tandem from readily available starting materials. The main merits of the present methods are operational simplicity, no need for column chromatography, inexpensive materials, avoidance of harmless and corrosive acid catalysts, short reaction times, good yields of the products, and utilization of aspirin as a non-toxic, cheap, commercially available, and efficient catalyst.