The substitution reactions of thiophene and 2-methylthiophene with the electrophilic selenenylating agent produced from the 2, 2′-dithienyl diselenide by oxidation with iodobenzene diacetate involve only the α-positions and give rise to the formation of oligo (seleno-2, 5-thienylenes). Products deriving from the attack at the α-positions of thiophene and 2-methylthiophene were also observed starting from the 5, 5′-dimethyl-2, 2′- ...