The efficient synthesis of dibenzo[d,d′]benzo[1,2-b:4,3-b′]dithiophene and cyclopenta[1,2-b:4,3-b′]bis(benzo[d]thiophen)-6-one

With 3,3′-bi[benzo[b]thiophenyl] as starting material, dibenzo[d,d′]benzo[1,2-b:4,3-b′]dithiophene, a [5]heterohelicene, was synthesized efficiently in 60% yield via formylation and McMurry reaction. Cyclopenta[1,2-b:4,3-b′]bis(benzo[d]thiophen)-6-one, another interesting helical ketone, was also prepared in 79% yield via deprotonation and ketonization of 3,3′-bi[benzo[b]thiophenyl]. In addition, the single-crystal structure of dibenzo[d,d′]benzo[1,2-b:4,3-b′]dithiophene and UV–vis spectra of both title compounds are described.