Synthesis and identification of 1,1,3,3-tetra-[1,2-dihydro-1,5-dimethyl-2-phenyl-3-oxopyrazole]propane

Abstract

Pyrazole derivatives are of practical value as analytical reagents, dyes and medicinal substances. It is known that 1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3H-one (antipyrine) and its bidentate derivatives are good analytical reagents for d-metal ions (Cd2+, Fe3+, Sc3+, Ti4+, Zn2+, Co2+, etc.). The chelating ability of bi-, tri- and tetradentate antipyrine derivatives make them promising organic ligands for the synthesis of organometallic coordination polymers. Therefore, synthesis of new tetradentate derivatives of 1,2-dihydro-1,5-dimethyl-2-phenyl-3Hpyrazole-one seems to be a highly relevant research task. The aim of this work was to synthesize and study a new substance – 1,1,3,3-tetra-[1,2-dihydro-1,5-dimethyl-2-phenyl-3-oxopyrazole]propane (tetraantipyryl-propane). A review of existing methods for the synthesis of antipyrine derivatives through condensation of 1,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one with aliphatic and aromatic aldehydes was carried out. A method was developed for the preparation and purification of 1,1,3,3-tetra-[1,2-dihydro-1,5-dimethyl-2-phenyl-3-oxopyrazole]propane by the reaction of electrophilic substitution of the protonated form of propandial (malonic dialdehyde) in the aromatic ring of the oxopyrazole heterocycle with a yield of 17.1%. The resulting compound is a white crystalline substance, readily soluble in organic polar and non-polar solvents, but insoluble in water. The purity of the recrystallized synthesis product was confirmed by measuring its melting point and conducting a qualitative reaction with sodium nitrite to detect an unsubstituted oxopyrazole cycle in the reaction substrate. The structure of 1,1,3,3-tetra-[1,2-dihydro-1,5-dimethyl-2-phenyl-3-oxopyrazole]propane was established by mass spectrometry and Raman spectroscopy.