Synthetic Access to Hydrogen and Halogen Derivatives of 3-Amino-4-nitrothiophenes

The unique synthesis of 3‐amino‐4‐nitrothiophenes 2 provides easy access to reference species of a new family of push‐pull substituted thiophenes. The chemoselective modification of 2 into suitable derivatives was accomplished by selective S‐oxidation of the vinylsulfanyl unit, followed by substitution of the vinylsulfinyl group of 3 by nucleophiles. Dihalothiophenes were formed this way in very good yields. A subsequent selective dehalogenation at the 2, 5 or 2 and 5 positions also proved feasible, and the push‐pull unit was untouched. The new 2,5‐dihalothiophenes could be interesting monomers for conducting polymers. Starting from per‐substituted 3‐amino‐4‐nitrothiophenes with a 2‐chloro‐ and a 5‐vinylsulfanyl substituent the formation of vinyl‐S‐oxides and subsequent substitution against nucleophiles is reported. Additionally, dehalogenation of the formed halothiophenes is possible with three different methods, which lead to selective dehalogenation at the 2, 5 or 2 and 5 position.