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.