Comparison of Ullmann/RCM and Ullmann/Bis-hydrazone Coupling Reactions: New Access to Benzodithiophenes for Dye-Sensitized Solar Cell and Thiahelicene Applications

The use of CuTC (Liebeskind's catalyst), followed by methylenation and ring-closing metathesis, or bis-hydrazone coupling reactions is described. This approach establishes an alternative non-photochemical synthesis of the strategically important 1,2-b:4,3-b′ BDT regioisomer, which has previously been underused in applications such as dye-sensitized solar cells and nonlinear optics because of the difficulty of synthesis on a large scale.