SCHEME 8: SYNTHESIS OF HYDROXYALKENOYL-3-METHYL-1H-PYRAZOL-5(4H)-ONES
SCHEME11: SYNTHESIS OF BISINDOLYLPYRAZOLONE DERIVATIVES
The process comprises the following steps: firstly, the pH of methanol solution of phenylhydrazine is adjusted to be between 5.0 and 6.5 with hydrochloric acid, acetoacetic ester is added drop by drop when the solution is mixed, the temperature is controlled between 40 DEG C and 90 DEG C, and the reflux reaction lasts for 1 to 6 hours secondly, the methanol in the reaction solution is distilled, the pH is adjusted to be neutral, the reaction solution is stirred, and the reflux reaction lasts for 1 to 3 hours at the temperature between 60 DEG C and 80 DEG C thirdly, the reaction solution is cooled after the reaction is completed, the crystal is separated, and the crude product is acquired through filtration fourthly, the crude product is dissolved in a solvent with methanol under the hot condition and recrystallized, and the finished product of white crystal 1-benzyl-3-methyl-5-pyrazole alkone can be prepared.
SCHEME15: SYNTHESIS OF UNSUBSTITUTED PYRAZOLONE DERIVATIVES
In this laboratory experiment, students synthesize 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one by selective C-acylation of 3-methyl-1-phenyl-1-pyrazol-5-one. Calcium hydroxide is used to push the tautomeric equilibrium toward the enol form, to protect the hydroxyl functionality as a complex, to trap the liberated hydrogen chloride, and to keep the reaction media basic. The product is obtained in excellent yield and recrystallized from various solvents and solvent systems. The chromatographic and physical parameters are determined and the results are analyzed. The signals in the NMR spectra of acyl pyrazolone are assigned and then compared with those of three previously synthesized acyl pyrazolones and two corresponding O-acylated products.