Iodine-Catalyzed Regioselective Oxidative Cyclization of Aldehyde Hydrazones with Electron-Deficient Olefins for the Synthesis of Mefenpyr-Diethyl

A regioselective
synthesis of polysubstituted dihydropyrazoles
and pyrazoles through an iodine-catalyzed oxidative cyclization strategy
of aldehyde hydrazones with electron-deficient olefins is described.
The protocol adopts very mild reaction conditions and provides desirable
yields. The reaction is supposed to proceed via a cascade C–H
functionalization, C–N bond formation, and oxidation sequential
processes. The overall simplicity and regioselectivity of the catalytic
system make this approach a valuable and step-economical tool to construct
a C–C bond for the synthesis of Mefenpyr-Diethyl.