Abstract: The invention relates to stabilizers containing at least two phenolic groups bonded to one another via a connecting radical (II) which is a polyol with a number-average molecular weight of from 75×F g/mol to 250×F g/mol, preferably from 100×F g/mol to 200×F g/mol, in particular from 100×F g/mol to 150×F g/mol, where the term F is the number of phenolic groups in the molecule.

Abstract: The preparation of 3-amino-1-phenylpyrazol-5-one by heating phenylhydrazine and a lower cyanoacetic acid alkyl ester in a polar solvent, using a lower alcoholate of an alkali metal as the condensation agent, leads to particularly high yields and quality, if the phenylhydrazine and 1 to 1.2 moles of the alcoholate are initially taken, the cyanoacetic ester is metered in and the reaction is carried out at 105.degree. to 140.degree. C., volatile alcohols which have been liberated from the ester and, if appropriate, from the alcoholate being distilled off at the reaction temperature. It is advantageous to employ the phenylhydrazine in an excess of up to about 200 mole % and to select, as the polar solvent, an alcohol or ether having a boiling point above 105.degree. C.

Abstract: Diaminophenyl ureas of the formula ##STR1## in which R is an inert substituent, are obtained from the corresponding dinitrophenyl urea by way of reduction, especially catalytic hydrogenation. Through a cyclization process, while splitting off ammonia, these ureas yield the corresponding aminobenzimidazolones, advantageously without an intermediate isolation of the diaminophenyl ureas.