Catalyst-free method for the synthesis of pyranopyrazoles in magnetized water

Pyranopyrazoles are fused heterocyclic compounds that possess many biological properties such as fungicidal, bactericidal, and act as anticancer agents[1].Multi-component reactions (MCRs), are those reactions in which three or more reactants react together to give the production a single step under suitable reaction conditions [2]. From the 1950s, we have known that water can be magnetized when exposed to an applied magnetic field, although the magnetization effect is very small [3].Herein, we are reporting a simple and efficient synthesis of pyranopyrazoles (5) by a four component reaction of hydrazine (1), ethylacetoacetate (2), dimedone (3) and aromatic aldehydes (4) in magnetized water at 50 °C.Preparation of magnetized water in order to prepare a magnetized water, 5 mL distilled water was first put in a test tube, which was then put between two neodymium magnets NdFeB (10cm×5cm×4cm) with a magnetic field of 0.8T. After20 min, the test tube was subsequently removed from the instrument and used for the reaction.General procedure for synthesis of pyranopyrazoles To 10-mL round-bottomed flask equipped with a magnetic stirrer bar and containing magnetized water (5 mL), were added ethyl acetoacetate (1.0 mmol), hydrazine (1.0 mmol), an aldehyde (1.0 mmol), and dimedone (1.0 mmol). The reaction mixture was stirred at 50 °C, and monitored by thin layer chromatography (TLC) technique. After completion of the reaction, the precipitate thus formed was filtered and purified by recrystallization from ethanol to afford the desired product.