The Reaction of Aroylacetaldehydes with Aroylhydrazines

Article abstract of DOI:10.1007/BF00810860

A series of aroylacetaldehyde aroylhydrazones were prepared and characterized.Their uv and 1H nmr spectra suggest the enol-imine structure rather than the keto-imine form. The pKa values of these aroylhydrazones were measured and correlated with the Hammett substitution constants.It was observed that benzoylacetaldehyde substituted in the p-position could be cyclized to form the 5-hydroxy-2-pyrazolines by refluxing in acidified ethanol, while formyldeoxybenzoin only gives the corresponding pyrazole due to steric requirements of the two phenyl groups.