Mechanistic Studies on the Rh(III)-Mediated Amido Transfer Process Leading to Robust C-H Amination with a New Type of Amidating Reagent

作者：Park, Yoonsu; Park, Kyung Tae; Kim, Jeung Gon^*; Chang, Sukbok

来源：Journal of the American Chemical Society, 2015, 137(13): 4534-4542.

DOI：10.1021/jacs.5b01324

• N BOND FORMATION
• CARBON-NITROGEN BONDS
• SULFONYL AZIDES
• INTERMOLECULAR AMIDATION
• FORMING REACTIONS
• NATURAL-PRODUCTS
• SYNTHETIC ROUTE
• ATOM-TRANSFER
• PALLADIUM
• FUNCTIONALIZATION

Mechanistic investigations on the Cp*Rh(III)-catalyzed direct C-H amination reaction led us to reveal the new utility of 1,4,2-dioxazol-5-one and its derivatives as highly efficient amino sources. Stepwise analysis on the C-N bond-forming process showed that competitive binding of rhodium metal center to amidating reagent or substrate is closely related to the reaction efficiency. In this line, 1,4,2-dioxazol-5-ones were observed to have a strong affinity to the cationic Rh(III) giving rise to dramatically improved amidation efficiency when compared to azides. Kinetics and computational studies suggested that the high amidating reactivity of 1,4,2-dioxazol-5-one can also be attributed to the low activation energy of an imido-insertion process in addition to the high coordination ability. While the characterization of a cationic Cp*Rh(III) complex bearing an amidating reagent was achieved, its facile conversion to an amido-inserted rhodacycle allowed for a clear picture on the C-H amidation process. The newly developed amidating reagent of 1,4,2-dioxazol-5-ones was applicable to a broad range of substrates with high functional group tolerance, releasing carbon dioxide as a single byproduct. Additional attractive features of this amino source, such as they are more convenient to prepare, store, and use when compared to the corresponding azides, take a step closer toward an ideal C-H amination protocol.

• 出版日期2015-4-8