Ultrasonic irradiation assisted efficient regioselective synthesis of CF(3)-containing pyrazoles catalyzed by Cu(OTf)(2)/Et(3)N

BACKGROUND: Most of the known approaches to the synthesis of CF(3)-containing organic compounds suffer from serious drawbacks. For example the starting materials required for these methods are rather difficult to obtain, or they are fairly toxic and inconvenient to work with and methods for direct fluorination and trifluoromethylation do not always allow the introduction of the CF(3)-group at the required position of a molecule. RESULTS: An efficient and attractive regioselective synthesis of a series of novel pyrazoles containing the trifluromethyl moiety was achieved using Cu(OTf)(2)/Et(3)N as an efficient catalytic system under ultrasonic irradiation. CONCLUSIONS: Cu(OTf)(2)/Et(3)N catalyst showed a great advantage over all the investigated catalysts, and the ultrasonic irradiation method offered high yields of pyrazoles in short reaction time compared with classical conditions. gHMBC spectra of the product were used to rationalize the observed regioselectivity.