Journal of the American Chemical Society
Article
Notes
the acyl azides. We were pleased to observe that a number of
1,4,2-dioxazol-5-ones having alkyl substituents at the 3-position
were highly facile to afford alkyl amidated products in excellent
yields (7j−l). An additional array of modified directing groups
was also investigated to find out that amide (7m−n), ketoxime
(7o), and N-oxide (7p) worked well albeit under slightly more
demanding conditions. However, ketone, a weakly coordinating
directing group, was not effective (7q).
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We thank Dr. Sung-Woo Park, Dr. Jaesung Kwak, and Mr.
Kwangmin Shin (Institute for Basic Science, Korea) for
valuable discussions and Ms. Seohee Oh (KAIST) for XRD
analysis. Y.P. is a recipient of Kwanjeong Educational
Foundation scholarship. This research was supported by the
Institute for Basic Science (IBS-R010-D1) in Korea.
The present arene C−H amidation with 1,4,2-dioxazol-5-
ones was highly efficient under mild conditions to allow for a
facile performance even in a large scale (eq 1). For instance, the
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CONCLUSIONS
■
We have described herein the development of a robust direct
C−H amidation using a new type of amidating reagent.
Stepwise analysis on the Cp*Rh(III)-catalyzed C−H amidation
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 with a strong
affinity could be employed as a new amidating reagent, thus
resulting in excellent amidation efficiency. Experimental and
computational works proved that the combination of the strong
coordination ability of 1,4,2-dioxazol-5-ones and low activation
energy of an imido insertion process is attributed to the origin
of high reactivity. In addition, isolation and characterization of a
cationic Cp*Rh(III) complex bearing an amino source were
realized. The understanding of coordination propensity of
metal center and nitrogen sources and the observation of its
turnover to an amido inserted rhodacycle allowed a clear
picture on the C−H amination process. The newly developed
Cp*Rh(III)-catalyzed reaction with 1,4,2-dioxazol-5-ones was
found to be highly efficient over 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 that they are more convenient to prepare, store,
and use when compared to the corresponding azides will make
a step closer toward an ideal C−H amination protocol.
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ASSOCIATED CONTENT
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Detailed experimental procedure and characterization of new
compounds, Cartesian coordinates of computed structures, and
X-ray analysis. This material is available free of charge via the
AUTHOR INFORMATION
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Corresponding Authors
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J. Am. Chem. Soc. XXXX, XXX, XXX−XXX