Synthesis of 3-Benzoyl-4-styryl-2-pyrazolines and Their Oxidation to the Corresponding Pyrazoles

The 3-benzoyl-4-styryl-2-pyrazolines 2a−g were prepared from the regioselective 1,3-dipolar cycloaddition reactions of (E,E)-cinnamylideneacetophenones 1a−g and diazomethane. The new compounds 3-(2-benzofuranyl)-4-styryl-2-pyrazolines (5c,d) were also obtained as by-products in some cases. The oxidation of the 3-benzoyl-4-styryl-2-pyrazolines 2a−g into 3(5)-benzoyl-4-styrylpyrazoles 3a−g is also reported. Configurational and conformational features of all compounds were established by NMR spectroscopy.