Environmentally benign synthesis of 3-methyl-4-[(1,3-diphenyl-1H-pyrazol-4-yl)-methylene]-1-phenylpyrazolin-5-(4H)-ones in an ionic liquid

The condensation of 1,3-diphenyl-1H-pyrazole-3-carbaldehydes with 3-methyl-1-phenylpyrazolin-5-(4H)-one in an ionic liquid (ethylammonium nitrate) afforded 3-methyl-4-(1,3-diphenyl-1H-pyrazolo-4-yl)methylene-1-phenylpyrazolin-5-(4H)-ones in an excellent yield at room temperature.