Synthetic chemistry forms an important basis for the pharmaceutical and materials industries. It has been advancing to fulfill the growing demand for technology that handles molecules with a high precision and efficiency. A large volume of research has been dedicated to identifying and designing more efficient routes to synthesize molecules.
One of the major breakthrough achievements from such efforts was the employment of transition metals as catalysts for organic reactions. With the knowledge of reaction mechanisms involving these various transition metals, we are now able to break many strong chemical bonds with a low amount of energy and make bonds with high accuracy, once considered impossible.
The Center for Catalytic Hydrocarbon Functionalizations is one of the leading research groups in catalytic reactions of transition metals. Using these metal complexes as catalysts, the Center has been conducting in-depth research to directly install nitrogen atoms onto hydrocarbons to produce amino compounds that contain various nitrogen functional groups. These amino compounds have an industry-wide application for products such as medical, electronic and optical materials, but directly converting hydrocarbons into amino compounds has been a challenge for a long time. The most commonly employed technique is a complex process because hydrocarbons need to be pre-functionalized before nitrogen atoms are introduced. A great deal of recent research has focused on simplifying the process, resulting inmore efficient routes to functionalize hydrocarbons. The Center has recently succeeded in developinghighly stable and commercially viable process to form amino compounds.
In fact, back in 2012, the Center developed a rhodium-based catalytic system where azides, an amino source with three nitrogen atoms, were adopted in order to activate hydrocarbons. Though the system could produce amino compounds that are widely applicable for various molecules and was also environmentally friendly as it releases nitrogen as a single by-product. However, it was not without flaws: it needed large amounts of expensive rhodium metals and a high reaction temperature of over 80℃. The Center started investigating the mechanisms behind the rhodium-azide reaction and has recently found why it requires a high rhodium loading and an elevated reaction temperature. When rhodium catalysts activate a hydrocarbon to have nitrogen introduced, azide compounds should form a covalent bond with the catalysts by donating a pair of electrons. However, azide functional groups are turned out to have weak ability to coordinate with rhodium metals, requiring a high catalyst loading and high reaction temperature. In order to improve the efficiency of the process, a new amino source with high coordination propensity had to be found.
The Center set its eyes on dioxazolones which have sp2 hybridized nitrogen atoms. As their unshared electron pairs are easily activated with oxygen and form stronger bonds with catalytic metals, they seemed like a viable alternative to azides.
Upon substituting azides with dioxazolones, the Center found out, the same amidation reaction takes place at room temperature with amount of rhodium catalysts reduced by 60%. This newly developed amidating reagent of 1,4,2-dioxazol-5-ones is applicable to a broad range of substrates with high functional group tolerance and only releases carbon dioxide as a by-product. It is more convenient to prepare, store and use compared with potentially explosive azides and has a high commercial viability because it uses ecofriendly ester as solvents.
With further research, the Center identified the structure of the reaction intermediates and the reaction mechanisms through computational quantum chemistry and explained the higher reactivity of the process. Its research was recognized as a pioneering example of reaction development on the basis of mechanistic study and published in the Journal of the American Chemical Society in March 2015. The practical aspect of the research drew significant industrial interest, and thus, the Center continued the research, developing a large scale, ecofriendly manufacturing process.
The Center is currently studying how to replace expensive rhodium catalysts with lowpriced transition metals to take a step closer toward an ideal carbon-hydrogen amination process. Its goal is to shorten the process so that hydrocarbons can be activated in a highly stable, economical and ecofriendly manner.

Published paper
Yoonsu Park, Kyung Tae Park, Jeung Gon Kim, and Sukbok Chang, “Mechanistic Studies on the Rh(III)-Mediated Amido Transfer Process Leading to Robust C−H Amination with a New Type of Amidating Reagent”, Journal of the American Chemical Society, Vol. 137, no. 13, pp. 4534–4542 (2015)

References
Ji Young Kim et al., “Rhodium-Catalyzed Intermolecular Amidation of Arenes with Sulfonyl Azides via Chelation-Assisted C–H Bond Activation”, Journal of the American Chemical Society, Vol. 134, no. 22, pp. 9110-9113 (2012)
Kwangmin Shin, Hyunwoo Kim, and Sukbok Chang, “Transition-Metal-Catalyzed C–N Bond Forming Reactions Using Organic Azides as the Nitrogen Source: A Journey for the Mild and Versatile C–H Amination”, Accounts of Chemical Research, Vol. 48, no. 4, pp. 1040-1052 (2015)