Simple and Efficient Three Component One-Pot Synthesis of Pyrazolo[1,5,a]Pyrimidines

A series of novel 5-(2-bromophenyl)-N-cyclohexyl-2-(methylthio)-6-nitro-7-phenyl-4,7-dihydropyrazolo [1,5-a] pyrimidine-3-carboxamides were synthesized by a one-pot reaction of 5-amino-N-cyclohexyl-3-(methylthio)-1H-pyrazole-4-carboxamide, 1-(2-bromophenyl)-2-nitroethanone and aryl aldehydes in the presence of boric acid in water at refluxing temperature. Structures of compounds were demonstrated by Fourier transform infrared, ¹H NMR, ¹³C NMR and elemental analysis. The advantages of this method are mild reaction condition, good yields, and operational simplicity.