Visible-Light-Promoted Diiodination of Alkynes Using Sodium Iodide

1,2-Diiodoalkenes can be used as precursors for synthesis of functional molecules such as heterocyclic drugs and organic conjugated materials due to their derivability of functional groups. Herein, alkynes can be converted into 1,2-transdiiodioalkenes efficiently and conveniently by using inexpensive and stable sodium iodide as iodine source and air as oxidant under the visible-light (blue light) with normal temperature and atmospheric pressure. The corresponding reactions were operated under mild conditions with inexpensive and easily accessible reagents, which obviate the need of transition-metal-catalysts or oxidizing reagents. Meanwhile, this method is compatible with a wide range of substrates, including terminal and internal alkynes even the peptide and carbohydrates containing a variety of heteroatoms and active hydrogen.