The nitrile imines generated by the oxidative dehydrogenation of aldehyde phenylhydrazones with chloramine-T in ethyl alcohol undergo 1,3-dipolar cycloaddition with benzalacetone in situ to afford 1-(3-aryl-1,4-diphenyl-4,5- dihydro-1H-pyrazol-5-yl)ethanones in good yield. The structure proofs of the synthesized new cycloadducts were provided by IR, 1H NMR, 13C NMR, Mass spectral studies and elemental analysis. The new compounds were evaluated in vitro for their antimicrobial and antioxidant activities.