AbstractTreatment of several substituted benzils [3,3′‐ and 4,4′‐dimethyl‐; 2,2′‐, 3,3′‐ and 4,4′‐dichloro‐; 3,3′‐dibromo‐; 4‐(N,N‐dimethylamino)‐] with an excess of chlorosulfonic acid gave the corresponding 3‐chloro‐2‐phenylbenzofuran disulfonyl dichlorides. Disubstitution was confirmed by microanalytical and spectral data for the corresponding bis(N,N‐dimethylaminsulfonamides). The positions of electrophilic substitution were not confirmed with 3,3′‐dimethyl‐, 2,2′‐ and 3,3′‐dichlorobenzils. With 4,4′‐dichlorobenzil, a smaller amount of chlorosulfonic acid enabled the isolation of 3,6,4′‐trichloro‐2‐phenylbenzofuran‐5‐sulfonyl chloride, which was identified by X‐ray analysis of theN,N‐dimethylsulfonamide. The cyclisation failed with 3,3′‐dimethoxy‐, a