Water → HCID 20198099, compound

Participants

Reaction Conditions

Reaction Steps

200 ml (3.74 moles) of concentrated sulphuric acid are added dropwise to 150 g (0.47 mole) of 1-methyl-3-(pyrazol-1-yl)-5-(3-trifluoromethylphenyl)-4-pyridone, with stirring, whereupon the temperature rises to 80° C. to 90° C. When the addition has ended, the mixture is warmed at 140° C., with stirring, until the evolution of gas has ended (about 45 minutes) and is then left to cool to about 40° C. to 50° C., 200 ml of water are carefully added in small portions and, when the addition has ended, the mixture is heated at the reflux temperature for about 60 minutes. The precipitate which separates out of the cooled reaction mixture is filtered off with suction, washed with a little water and dried at 80° C. 148 g (about 80% of theory) of a solid [5-(3-carboxyphenyl)-1-methyl-3-(pyrazol-1-yl)-4-pyridone-sulphuric acid adduct (xn H2SO4)] are obtained, 40 g of which (about 0.1 mole) are dissolved in a mixture of 700 ml of water and 700 ml of ethanol at 70° C. An aqueous barium hydroxide solution is added dropwise to this solution until the pH reaches 7.5, and the barium sulphate precipitated is filtered off with suction over kieselguhr. Solid carbon dioxide is added to the filtrate at room temperature until, at a pH value of 5.5, the free acid precipitates, which is filtered off with suction, washed with a little cold water and dried. 11.5 g (37% of theory) of 5-(3-carboxyphenyl)-1-methyl-3-(pyrazol-1-yl)-4-pyridone of melting point 280° C. are obtained.

Provenance & Evidence