FeCl3-diorganyl dichalcogenides promoted cyclization of 2-organochalcogen-3-alkynylthiophenes: synthesis of chalcogenophene[2,3-b]thiophenes

We report here our results on the FeCl3-diorganyl dichalcogenides intramolecular cyclization of 2-organochalcogen-3-alkynylthiophenes. The cyclization reaction proceeded cleanly under mild reaction conditions giving the (S)-Se-, (S)-S- and (S)-Te-heterocycles in good yields. In addition, the obtained chalcogenophenes were readily transformed into more complex products using the palladium cross-coupling reaction with boronic acids. Conversely, using a metal-halogen exchange reaction with n-BuLi, the chalcogenophenes produced the lithium-intermediate which was trapped with aldehyde furnishing the desired secondary alcohol in good yield.