A novel route for an iron-catalyzed tandem sulfonylation, C(sp2)-H activation, cyclization reaction which uses N-phenyl-N-(prop-2-yn-1-yl)benzenesulfonamide and benzenesulfonohydrazide to synthesize derivatives of (Z)-2-phenyl-4-((phenylsulfonyl)methylene)-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxide 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 benzothiazides.