A metal-free redox arylation of alkynes with sulfoxides has been developed to provide unconventional access to diverse γ-arylated 1,3-dicarbonyl compounds in an atom-economical manner. Mechanistic studies suggest that a conjugated allenone intermediate was generated in situ, which solves the problem of reactivity and regioselectivity of unsymmetrical dialkyl-substituted internal alkynes and enables the functionalisation of a broad range of substrates bearing electron-withdrawing functional groups. The resulting arylated 1,3-dicarbonyl compounds are versatile and useful building blocks for further functionalisation.