Electrophilic Cyclization of (<i>Z</i>)-Selenoenynes:  Synthesis and Reactivity of 3-Iodoselenophenes

We present here our results of the electrophilic cyclization reaction of (<i>Z</i>)-selenoenynes with different electrophiles such as I<sub>2</sub>, ICl, PhSeBr, and PhSeCl. The cyclization reaction proceeded cleanly under mild reaction conditions, and 3-substituted selenophenes were formed in moderate to excellent yields. We observed that the nature of solvent and structure of (<i>Z</i>)-selenoenyne were important to the cyclization reaction. In addition, the obtained 3-iodoselenophenes were readily transformed to more complex products using a metal−halogen exchange reaction with <i>n</i>-BuLi and trapping the intermediate formed with aldehydes, furnishing the desired secondary alcohols in good yields. Conversely, using the palladium or copper catalyzed cross-coupling reactions with terminal alkynes or alkyl alcohols, we were able to convert 3-iodoselenophene to Sonogashira or Ullmann type products, respectively, in good yields.