The tellurophene motif has garnered research interest, e.g., for organic electronics due to useful properties such as narrow band gaps, high charge carrier mobilities, and the redox capability of tellurium. Tellurophenes can, for example, be used in the production of OLEDs (organic LEDs). They could also have applications in the fields of medicinal chemistry and pharmacology.

Edgars Paegle and Pavel Arsenyan, Latvian Institute of Organic Synthesis, Riga, Latvia, have developed a simple method for the preparation of benzo[b]tellurophenes (general reaction pictured). The team found that a cyclization of o-haloarylalkynes in the presence of Te, NaOH, and dimethyl sulfoxide (DMSO), with water as an additive, occurs via  simple mixing of the starting materials and heating overnight. The reaction gives the corresponding benzo[b]tellurophenes in up to 90 % yield (as determined by gas chromatography) without the need for a dry and inert atmosphere. According to the researchers, it occurs through a S_NAr/5-endo–dig cascade process.

The developed reaction can be extended to aryl iodide substrates that are not suitable for the direct cyclization approach when CuI is used as a catalyst for the telluration. The obtained benzo[b]tellurophene derivatives can be further transformed, which can be useful in pharmaceutical chemistry. They could, e.g., provide a path to the tellurium analogues of SERM (selective estrogen receptor modulator) and SERD (selective estrogen receptor degrader) agents such as raloxifene.

• Simple Access to 2‐Arylbenzo[b]tellurophenes,
  Edgars Paegle, Pavel Arsenyan,
  Eur. J. Org. Chem. 2023.
  https://doi.org/10.1002/ejoc.202201367