Synthesis of polyfluorophenyl substituted-4,5-dihydropyrazole derivatives via 1,3-dipolar cycloaddition of nitrile imine with ethyl acrylate

Oxidation of aldehyde 4-chloro-2,3,5,6-tetrafluorophenylhydrazones (1) with [bis(acetoxy)iodo]benzene leads to the formation of nitrile imines (2) which reacted in situ with ethyl acrylate to produce 3-substituted-1-(4-chloro-2,3,5,6-tetrafluorophenyl)-5-ethoxycarbonyl-4,5-dihydropyrazoles (3) in moderate to good yields. The structures of new compounds were fully confirmed by their spectral data, elemental analyses and X-ray diffraction (XRD) analysis. A plausible reaction mechanism for the synthesis of title compounds is presented.