PROCESS FOR THE PREPARATION OF 1-PHENYL-3-CARBAMOYL-PYRAZOL-5-ONES

摘要

The invention relates to the preparation of 1-phenyl-3-carbamoyl-5-pyrazolones of the formula: in which the two symbols R and R' may be the same or different and each represents a hydrogen atom, an alkyl radical or a substituted alkyl radical containing 1 to 4 carbon atoms. An aqueous paste of diethyl oxalacetate phenylhydrazone is heated at a temperature not greater than 85 DEG C. until the hydrazone is completely melted, and the aqueous phase is then removed and the remaining hydrazone is treated with 2 to 12 molar equivalents of a compound of the formula HNRR' at a temperature between 20 DEG and 100 DEG C. The formation of 1-phenyl-3-carboxy-5-pyrazolone is thus avoided.