•Mild conditions.•Readily available reactants.•Good-to-high yields.•New reaction mechanism.In this study, sulfones are synthesized from sulfonylhydrazones catalyzed by iron(III) phthalocyanine chloride. This reaction offers broad substrate scope, occurs under mild conditions, utilized readily available reactants, and forms products in good-to-high yields. Crossover experiments reveal that the reaction occurs via an intramolecular process, which is possibly different from other studies reported previously. The method provides a novel, simple, and promising strategy for synthesizing functionalized sulfones in the research field of sulfur chemistry.