Synthesis of Fused 4-Iodoselenophene[2,3-b]thiophenes by Electrophilic Cyclization of 3-Alkynylthiophenes

We present here our results on the electrophilic cyclization reaction of 3‐alkynylthiophenes with different electrophiles such as I2, ICl, and PhSeBr. The cyclization reaction proceeded cleanly under mild reaction conditions, giving fused 4‐iodoselenophene[2,3‐b]thiophenes in excellent yields. In addition, the obtained chalcogenophenes were readily transformed into more complex products through palladium‐ or copper‐catalyzed cross‐coupling reactions with thiols, boronic acids, and organozinc reagents. The electrophilic cyclization reaction of 3‐alkynylthiophenes with different electrophiles proceeded cleanly under mild reaction conditions, giving fused 4‐iodoselenophene[2,3‐b]thiophenes in excellent yields. The obtained chalcogenophenes were readily transformed into more complex products through palladium‐ or copper‐catalyzed cross‐coupling reactions.