The oxidation of p-chloroiodobenzene (I) with peracetic acid (II) in acetic acid affords 4-chloroiodosobenzene diacetate (III), which is then condensed with thiophene (IV) by means of acetic anhydride and trifluoroacetic acid yielding (p-chlorophenyl)-2-thienyliodonium trifluoroacetate (V). Finally this salt is treated with HCl in aqueous formic acid. (1-4)