We describe the synthesis and electrochemical oxidation properties of ferrocene dimers bridged by a fused oligothiophene spacer (thienothiophene, benzodithiophene, and dithienothiophene), which are designed as new types of ferrocene dimers for the study of the oxidation process via a mixed‐valence state. The electrochemical properties of all ferrocene dimers were examined by a cyclic voltammetry technique. The voltammograms showed a reversible two‐electron oxidation wave derived from the two ferrocene fragments with a potential difference between the first and second oxidation waves (ΔE1/2 = E1/2(+1/+2) – E1/2(0/+1)), which ranges from 0 to +127 mV. This result indicates that the chemical structure of the fused oligothiophene spacer can be attuned to the two‐electron oxidation process of two ferrocene terminals via a mixed‐valence state.

Alkynyl propargyl sulfones underwent secondary amine-induced cyclization to give six-membered cyclic enaminosulfones, and the products were subjected to acidic hydrolysis to afford the corresponding cyclic -ketosulfones in high yields.