Activating C-H Bonds Over C-Br Bonds to Make Oligothiophenes

Significance

Expanding on previous work, Mori and co-workers have developed an efficient method to preferentially activate the C-H bond located alpha to the sulfur in thiophene, even in brominated thiophenes. While their previous work utilized AgF, the less expensive and more robust combination of AgNO₃ and KF is preferred here, though in both cases a superstoichiometric amount is required. Precaution should be taken when working up the reaction because hydrofluoric acid is a byproduct, along with metallic silver. The use of the resulting brominated oligothiophenes in the Stille and Sonogashira reaction is demonstrated.