Synthesis and Characterization of Novel Heterocyclic Chalcones from 1-Phenyl-1<i>H</i>-pyrazol-3-ol

An efficient synthetic route to construct diverse pyrazole-based chalcones from 1-phenyl-1H-pyrazol-3-ols bearing a formyl or acetyl group on the C4 position of pyrazole ring, employing a base-catalysed Claisen–Schmidt condensation reaction, is described. Isomeric chalcones were further reacted with N-hydroxy-4-toluenesulfonamide and regioselective formation of 3,5-disubstituted 1,2-oxazoles was established. The novel pyrazole-chalcones and 1,2-oxazoles were characterized by an in-depth analysis of NMR spectral data, which were obtained through a combination of standard and advanced NMR spectroscopy techniques