Synthesis, biological evaluation and molecular modeling study of 5-trifluoromethyl-Δ²-pyrazoline and isomeric 5/3-trifluoromethylpyrazole derivatives as anti-inflammatory agents.

Searching for new anti-inflammatory agents, we have prepared a series of potential COX-2 inhibitors, 1-(4,6-dimethylpyrimidin-2-yl)-5-hydroxy-5-trifluoromethyl-Δ(2)-pyrazolines (3) and 1-(4,6-dimethylpyrimidin-2-yl)-3-trifluoromethylpyrazoles (4), by refluxing 2-hydrazino-4,6-dimethylpyrimidine (1) with a number of trifluoromethyl-β-diketones (2) in ethanol. Further dehydration of compounds (3) to the corresponding 1-(4,6-dimethylpyrimidin-2-yl)-5-trifluoromethylpyrazoles (5) was also achieved. Fifteen of these compounds were screened for their anti-inflammatory activity using the carrageenan-induced rat paw edema assay. While all the compounds exhibited significant anti-inflammatory activity (47-76%) as compared to indomethacin (78%), 3-trifluoromethylpyrazoles (4) were found to be the most effective agents (62-76%). To rationalize this anti-inflammatory activity, docking experiments molecular dynamics simulations were performed to study the ability of these compounds to bind into the active site of the COX-2 enzyme.