Tetrakis(alkylthio)thieno[3,4‐c]thiophene: Synthesis, stability, and reactivity

The synthesis of tetrakis(alkylthio)thieno[3,4‐c]thiophenes la‐e by the dimerization reaction of bis(alkylthio)cyclopropenethiones is described. The remarkable thermodynamic and kinetic stability suggests the significant electron‐accepting conjugation of the alkylthio substituents to the carbanionic 1, 3, 4, and 6 carbons in the framework. The isopropylthio‐ and ethylthio‐substituted thienothiophenes 1d and 1e undergo cycloaddition reactions with dienophiles such as N‐phenylmaleimide and dimethyl acetylenedicarboxylate to give the cycloadducts in moderate yields.