Chemoselective synthesis of multi-functionalized alkynes and alkenes via transition-metal-free iodination of terminal alkynes.

A highly efficient method for the terminal iodination of alkynes is developed to access multi-functionalized alkynes containing an iodo and a propargyl ether group under mild reaction conditions using an I2/K2CO3 system in methanol. Reactions enable the synthesis of 1,2-diiodoalkenes containing an allyl ether via diiodination using the I2/KI reagent system in water under ultrasonication. Chemoselectivity has been achieved by a judicious choice of the reaction conditions for synthesizing monoiodination and diiodination products. This diversity-oriented synthesis requires no purification, allowing access to a variety of compounds in pure forms in excellent yields. The reactions are compatible with many substrates, and practical applications are demonstrated with a scale-up reaction.