Environment friendly synthesis of trifluoromethyl-festooned pyrazolo[1,5-a]pyrimidines with promising biological activity

A series of 7-(3,5-bis(trifluoromethyl)phenylpyrazolo[1,5-a]pyrimidine derivatives and 7-(4-(trifluoromethyl)phenyl)pyrazolo[1,5-a]pyrimidine bearing trifluoromethyl group were efficiently synthesized in good to high yields by reacting the precursors (E)-1-(3,5-bis(trifluoromethyl)phenyl)-3-(dimethylamino)prop-2-en-1-one (1) and (E)-3-(dimethylamino)-1-(4-(trifluoromethyl)phenyl)prop-2-en-1-one (4) with aminopyrazoles under ultrasonic irradiation assisted by KHSO₄ at 60 °C in aqueous media. The structures of the compounds were confirmed by comprehensive structural and analytical characterization techniques (¹H NMR, ¹³C NMR, FT-IR, MS, HR-MS) with further validation by X-ray crystallographic analysis of a selected compound 3a. Antimicrobial evaluation of the compounds revealed moderate to comparable activities with compounds 3f, 3i, 6a, 6c and 6f as potential bioactive scaffolds.