Formation of radical cation and dication of 1,3,4,6-tetrakis(isopropylthio)2λ4δ2-thieno[3,4-c]thiophene and their reactions with nucleophiles

Abstract

1,3,4,6-Tetrakis(isopropylthio)-2λ⁴δ²-thieno[3,4-c]thiophene 1 formed the complex 2 with I₂ in hexane at –30 °C. The ESR spectrum of the complex 2 in MeCN solution showed that the spin densities in the π-electron system are large in the 1-,3-,4- and 6-positions. The complex 2 reacted with amines in MeCN to give the C-C coupling products 4a–c in high yields. The oxidation of 1 with I₂ in the presence of aniline in benzene gave the thiophene derivative 5 in a high yield by hydrogen abstraction at the 3-position. The compound 1 was oxidised to its dication by NOBF₄. The dication reacted with amines, alcohols and water to give the ring-opening products 10–14 and with thiols and NaBH₄ to give the adducts 23–25.