Copper-Catalyzed Stereospecific Synthesis Of Vinyl Iodides

Vinyl iodides are versatile reagents in organic synthesis. With high reactivity, they are widely used in the carbon-carbon and carbon-heteroatom bonds formation reactions. In addition, I-radiolabeled vinyl iodides can be used as radiopharmaceutical, which play an important role in biomedical field, such as organ function tests and radioimmunoassay, etc.In this paper, the stereospecific synthesis of vinyl iodides was investigated by using economic and environment friendly copper as catalyst. The main contents are as follows:The iodination of (E)-β-bromo-4-methylstyrene was selected as the model to optimize the reaction conditions, such as solvent, ligand, catalyst, reaction time and temperature. The best result was obtained when the model reaction was performed using KI as the iodine source in the presence of 10 mol% CU2O and 20 mol% L-Proline as the catalyst and ligand, respectively, in anhydrous ethanol at 110 ℃. Under optimum reaction conditions, the corresponding iodide product, (E)-β-iodo-4-methylstyrene, was obtained in 87% yield. Based on this, we examined the scope of substrates under this catalytic system. Results indicated that styrene based bromides and heteroaryl vinyl bromides can be converted into the corresponding iodides efficiently in 66-92% yields with complete retention of configuration.