Palladium-catalyzed coupling reactions towards the synthesis of well-defined thiophene-oligomers

Heck- and Ullmann-type palladium-catalyzed reactions were used in order to perform the synthesis of 3′,4″-dioctyl-2,2′,5′2″,5″,2′″-tetrathienyl. The desired oligothiophene was synthesized in five steps with a total yield of 38% by a Heck-type reaction of bromo-derivatives and a yield of 45% by an Ullmann-type reaction of iodo-precursors.