A novel method of iodination and azo bond formation by nitrogen triiodide

A green, multi-gram, and convenient method of iodination is presented. This method allows for in-situ formation and safe utilization of nitrogen triiodide for C–I bond formation on a series of pyrazole derivatives. Nitrogen triiodide is commonly known for visual demonstrations in chemistry-popularization experiments, and thus far, it has minimal application in synthetic or industrial chemistry. By increasing the amount of nitrogen triiodide in the reaction mixture, it is possible to achieve the selective formation of azo bond between pyrazole derivatives. In this manner prepared iodinated pyrazoles can be utilized as versatile building blocks in organic synthesis, especially in C–C and N–C coupling reactions. Furthermore, numerous iodinated organic molecules are bioactive. Pyrazoles bonded by azo bonds can be utilized in photodynamic therapy and photo-switching as they have a relatively high half-life of isomerization between E/Z isomers (up to 1000 days) and usually the two isomers have different bioactivity. Overall, eight new structures were prepared, isolated, and described by NMR experiments and other spectral methods. The described method displays the potential to be utilized as a rapid and non-expensive iodination procedure for a broader series of organic molecules and it could be considered a viable alternative to other commonly used iodination reactions such as the use of molecular iodine or potassium iodide with oxidation regents, pure N-iodosuccinimide or activated with a Lewis acid, or N-iodosaccharin.