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).