Iron(II)-Catalyzed\nSynthesis of Nitrated Dihydropyrazole\nvia a Nitrification and C–H Activation/Cyclization Cascade\nReaction

A route for nitrification and C–H activation/cyclization\nof (<i>E</i>)-<i>N</i>-allyl-<i>N</i>′-benzylidenebenzenesulfonohydrazide and cobalt nitrate via\nan iron(II)-catalyzed cascade reaction to synthesize nitrated dihydropyrazoles\nhas been developed. The method features convenient operation and good\nfunctional group tolerance. In addition, it employs insensitive and\ninexpensive FeSO<sub>4</sub> as the catalyst and provides a direct\napproach for the preparation of dihydropyrazoles.