A Green Synthetic Strategy for Pyrazolo[1,5-a]pyrimidin-7(4H)-one Derivatives by the Reaction of Aminopyrazoles and Symmetric/Non-symmetric Alkynes Assisted by KHSO4 in Aqueous Media

Abstract

Pyrazolo[1,5-a]pyrimidine and its derivatives possess important pharmacological properties and hence they have drawn substantial attention as a privileged scaffold to design and explore novel drugs in medicinal chemistry. We herein report a green synthetic approach for a library of pyrazolo[1,5-a]pyrimidin-7(4H)-one derivatives under ultrasonic irradiation which is one of the green approaches to minimize environmental impact in synthetic organic chemistry.Aminopyrazoles were reacted with symmetric and non-symmetric alkynes assisted by KHSO4 under the influence of US in aqueous ethanol to give pyrazolo[1,5-a]pyrimidines in good yields. This strategy worked well with dimethyl acetylenedicarboxylate (DMAD) and ethyl/methyl propiolate and the corresponding products were obtained in good yields. The structures of the products were well established with the help of their analytical and spectral data (1H NMR, 13C NMR, FT-IR, MS).