Synthesis of Thiophene-annulated Naphthalene Diimide-based Small-Molecular Acceptors via Two-step C-H Activation

Thiophene-annulated naphthalene diimide (NTI)-based molecules have recently emerged as an important class of n-type electronic materials. However, their synthesis has predominantly been achieved by Stille or Suzuki coupling reactions despite the presence of a potential C-H bond in NTI. Additionally, the synthesis of NTI or more generally mono-functionalization of naphthalene diimide (NDI) starts with a cumbersome bromination that results in a low yield, is unselective, and requires tedious purification. We herein thus address these issues via a two-step C-H activation: a rhodium-catalyzed direct C-H iodinization is first presented for NDI, followed by establishing an efficient direct arylation protocol for NTI with high yield and robustness. Coupling of up to four NTI units on a benzene or pyrene core is demonstrated along with other aryl bromide substrates. All the herein reported NTI-based small molecules showed n-type semiconductor behavior under air.