Iron(II)-Catalyzed Synthesis of Nitrated Dihydropyrazole via a Nitrification and C–H Activation/Cyclization Cascade Reaction

A route for nitrification and C-H activation/cyclization of (E)-N-allyl-N'-benzylidenebenzenesulfonohydrazide and cobalt nitrate via an iron(II)-catalyzed cascade reaction to synthesize nitrated dihydropyrazoles has been developed. The method features convenient operation and good functional group tolerance. In addition, it employs insensitive and inexpensive FeSO₄ as the catalyst and provides a direct approach for the preparation of dihydropyrazoles.