4-[(3-Hydroxy-5-phenyl-1H-pyrazol-4-yl)methyl]-5-phenyl-1H-pyrazol-3(2H)-one

Abstract

The solid-state structure of the title compound, C19H16N4O2, is dominated by the keto–enol tautomerization of its two 1H-pyrazol-3-one moieties. Since all H atoms could be located in a difference Fourier synthesis, it was possible to distinguish the enol form from the keto form unambiguously. As a result of this tautomerization, an intra­molecular hydrogen bond embedded in an eight-membered ring is formed. The two-dimensional hydrogen-bonding system results from three additional inter­molecular hydrogen bonds of different strengths, all involved in eight- and ten-membered ring systems.