New efficient synthetic routes to trifluoromethyl substituted pyrazoles and corresponding β-diketones

Abstract

An improved and more efficient synthesis procedure for trifluoromethyl substituted pyrazoles, namely 3,5-bis(trifluoromethyl)-1H-pyrazole (1a), 5-(pentafluoroethyl)-3-(trifluoromethyl)-1H-pyrazole (1b), 5-(heptafluoropropyl)-3-(trifluoromethyl)-1H-pyrazole (1c), 5-(nonafluorobutyl)-3-(trifluoromethyl)-1H-pyrazole (1d), 5-phenyl-3-(trifluoromethyl)-1H-pyrazole (1g), 5-(pentafluorophenyl)-3-(trifluoromethyl)-1H-pyrazole (1h), 5-methyl-3- (trifluoromethyl)-1H-pyrazole (1e), and 5-(tert-butyl)-3-(trifluoromethyl)-1H-pyrazole (1f) is presented which starts from the corresponding β-diketones (2a–h). In addition, the preparation of some of the corresponding diketones (2b–d and 2h) is revisited with an emphasis on low-cost and easily available starting materials. All products were characterized using multinuclear (1H, 13C, 19F) NMR spectroscopy. Additionally, thermal properties of synthesized pyrazoles were characterized using differential scanning calorimetry.