Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Jun 10;131(22):7558-9.
doi: 10.1021/ja902893u.

Understanding the differential performance of Rh2(esp)2 as a catalyst for C-H amination

David N Zalatan  1 , J Du Bois
Affiliations

Understanding the differential performance of Rh2(esp)2 as a catalyst for C-H amination

David N Zalatan et al. J Am Chem Soc. .

Abstract

Catalytic amination of saturated C-H bonds is performed efficiently with the use of Rh(2)(esp)(2). Efforts to identify pathways for catalyst degradation and/or arrest have revealed a single-electron oxidation event that gives rise to a red-colored, mixed-valence dimer, [Rh(2)(esp)(2)](+). This species is fortuitously reduced by carboxylic acid, a byproduct generated in the reaction cycle with each turnover of the diacyloxyiodine oxidant. These findings have led to the conclusion that the high performance of Rh(2)(esp)(2) is due in part to the superior kinetic stability of its one-electron oxidized form relative to other dimeric Rh complexes.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Intermolecular benzylic C–H amination efficiently catalyzed by Rh2(esp)2. Tces) SO2OCH2CCl3.
Figure 2
Figure 2
One-electron oxidation of Rh2(esp)2 and Rh2(O2CnPr)4.
Figure 3
Figure 3
Ligand exchange promoted by iodine oxidant.
Figure 4
Figure 4
Product analysis gives mechanistic insight.
Figure 5
Figure 5
Reduction of [Rh2(esp)2]+ by R′CO2H. Rh2(esp)2 = (green); Rh2(esp)2·2(R′CO2H) = (dark blue); [Rh2(esp)2]+ = (red); recorded UV/visible spectrum following treatment of [Rh2(esp)2]+ with R′CO2H = (light blue).
Figure 6
Figure 6
Improved reaction performance using an alternative hypervalent iodine oxidant.
See this image and copyright information in PMC

References

    1. For recent reviews on C–H amination, see: Dauban P, Dodd RH. In: Amino Group Chemistry. Ricci A, editor. Wiley-VCH; Weinheim, Germany: 2008. pp. 55–92.Davies HML, Manning JR. Nature. 2008;451:417–424.

    1. Espino CG. Ph. D. Thesis. Stanford University; Stanford, CA: 2004. Du Bois J. Chemtracts–Org Chem. 2005;18:1–13.. Reactions conducted with Rh2(O2C13Me)4 show Me13CO2H within 60 seconds of initiation.

    1. Espino CG, Fiori KW, Kim M, Du Bois J. J Am Chem Soc. 2004;126:15378–15379. - PubMed
    1. Fiori KW, Du Bois J. J Am Chem Soc. 2007;129:562–568. - PubMed

    1. Use of PhI(O2CnPr)2 is preferred over PhI(OAc)2 for mechanistic studies given its greater solubility in organic solvents.

Publication types