Multiwalled carbon nanotubes/guanidine/Ni (II): A new and effective organometallic catalyst for the green synthesis of pyrazolopyranopyrimidines

Abstract

In this research, we report the first example of the use of multiwalled carbon nanotubes/guanidine/Ni (II) as a new and effective catalyst. The supported catalyst was prepared through a new method and characterized by Fourier transform infrared, scanning electron microscopy, energy‐dispersive spectroscopy, inductively coupled plasma, thermogravimetric analysis, ultraviolet diffuse reflectance spectroscopy, and transmission electron microscopy. Obtained catalyst was used for green and efficient synthesis of pyrazolopyranopyrimidines via four‐component reaction of hydrazine hydrate, ethyl acetoacetate, barbituric acid, and aromatic aldehydes under ultrasonic condition. All products were obtained in high yields and short reaction times. Also, the prepared catalyst was easily separated from the reaction mixture and reused for several times without significant loss of activity.