Rh(III)-Catalyzed C-H amidation with N-Hydroxycarbamates: A new entry to N-Carbamate-protected arylamines

Article abstract of DOI:10.1021/ol403477w

An unprecedented Rh(III)-catalyzed direct intermolecular C-H amidation with N-hydroxycarbamates has been developed. Different directing groups, such as pyridine, pyrimidine, pyrazole, and N-OMe oxime, can be employed in this C-H amidation process, providi

Full text of DOI:10.1021/ol403477w

Letter
pubs.acs.org/OrgLett
Rh(III)-Catalyzed C−H Amidation with N‑Hydroxycarbamates: A New
Entry to N‑Carbamate-Protected Arylamines
Bing Zhou,* Juanjuan Du, Yaxi Yang,* Huijin Feng, and Yuanchao Li
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, PR China
S
* Supporting Information
ABSTRACT: An unprecedented Rh(III)-catalyzed direct
intermolecular C−H amidation with N-hydroxycarbamates
has been developed. Different directing groups, such as
pyridine, pyrimidine, pyrazole, and N-OMe oxime, can be
employed in this C−H amidation process, providing valuable
N-carbamate-protected arylamines (e.g., Cbz, Moz, Ac, Boc,
and Fmoc). More importantly, this process may afford a new
avenue for intermolecular C−H amidation where readily available N-hydroxycarbamates can be used as the nitrogen source
he arylamine functionality is a common motif in
Tbiologically active natural products, pharmaceuticals, and
functional materials.1 To date, the most reliable and practical
methods to attach amine groups to aromatic rings are
represented by Buchwald−Hartwig- and Ullman-type cross
couplings.2 However, these approaches need preactivated aryl
(pseudo)halides as the substrates. With the continuous
advancement in catalytic C−H bond activation,3 extensive
research has been devoted to metal-catalyzed direct C−H
amination reactions.4
To date, two strategies can be employed in metal-catalyzed
intermolecular (hetero)arene C−H amination. The first
strategy is direct C−H amination of activated arenes5 and
few chelate group containing arenes6 with amines or amides
under oxidative conditions (Scheme 1a). Alternatively, the use
of preactivated amino precursors (O-acylhydroxylamines,
chloroamines, NFSI, azides) has been demonstrated in redox-
neutral amination reactions (Scheme 1b).7,8 Despite these
advances, owing to the abundance and structural diversity of
arylamines, further development of novel catalytic amination
reactions (particularly ones employing other readily available
amino source) is still highly desirable.
Recently, Rh(III) complexes have been employed as a
promising catalyst for addition of aryl C−H bonds to polar C
N or CO groups.9 Very recently, we reported a mild Rh(III)-
catalyzed addition of aryl C−H bonds to nitrosobenzenes (N
O bonds) to give N,N-diarylhydroxylamines (Scheme 1c).10
Inspired by these works,11−14 herein we report the first example
of Rh(III)-catalyzed aryl C−H amidation with N-hydroxycar-
bamates giving access to N-carbamate protected arylamines
(Scheme 1d). Notably, this is the first example of employing
readily available N-hydroxycarbamates as the amino source in
the catalytic C−H amidation reaction, thus affording a new
direction for intermolecular amidation of C−H bonds with N-
hydroxycarbamates.
Our initial studies focused on the reaction of 2-phenyl-
pyridine (1a) and carbobenzyloxy (Cbz)-protected hydroxyl-
amine (2a). As shown in Table 1, heating a mixture of 1a with
2a, Cu(OAc)2, and catalyst [RhCp*Cl2]2 (2.5 mol %) in the
presence fo AgSbF6 (10 mol %) at 100 °C in DCE led to
product 3a in 30% yield. Interestingly, no hydroxylamine
product 4a was observed, presumably because 4a is unstable
and spontaneously decomposes to give 3a via nitroxide radical
intermediate.15 The structure of the amidation product 3a was
confirmed by single-crystal X-ray crystallography.16 The
prepared catalyst [RhCp*(CH3CN)3](SbF6)2 (2.5 mol %)
afforded a higher yield (entry 2). Next, other oxidants were
screened (entries 3−7), and Ag2CO3 was found to be the ideal
oxidant for the reaction (entry 7). A screen of the solvents gave
THF as an optimal one (entry 10). A decrease of yield was
observed when raising or lowering the reaction temperature
(entries 11 and 12). A control experiment showed that the Rh
catalyst was necessary for the reaction (entry 13), and both
Scheme 1. C−N Bond Formation via C−H Activation
Received: December 2, 2013
Published: December 26, 2013
© 2013 American Chemical Society
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Letter
a
Table 1. Optimization of the Rh-Catalyzed Amidation
Reaction
Scheme 2. Scope of Arene Substrates
a
entry
catalyst
oxidant
solvent
DCE
3a (%)
1
2
3
4
5
6
7
8
9
10
(Cp*RhCl2)2/AgSbF6
Cu(OAc)2
Cu(OAc)2
MnO2
30
57
20
15
60
60
70
65
55
77
70
67
0
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
DCE
DCE
DCE
DCE
DCE
DCE
PhMe
1,4-dioxane
THF
t-BuOOH
AgOAc
Ag2O
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
b
11
c
THF
12
THF
13
THF
d
14
Cp*Rh(MeCN)3(SbF6)2
Cp*Rh(MeCN)3(SbF6)2
THF
70
25
15
THF
a
1a (0.2 mmol), 2a (0.24 mmol), catalyst (0.005 mmol), oxidant (0.3
mmol), and solvent (1 mL) at 100 °C for 10 h. Yield of isolated
b
c
product. Reaction temperature = 120 °C. Reaction temperature = 80
d
°C. The reaction was carried out under Ar.
Ag2CO3 and oxygen could promote this transformation as an
oxidant (entries 14 and 15)
With the optimized reaction conditions in hand, we next
surveyed the scope of the reaction (Scheme 2). Both electron-
donating (3b, 3c, 3g, 3h) and -withdrawing (3d) groups on the
phenyl ring were well tolerated, as were halogen-substituted
substrates (3e, 3f, 3i). Meta-substituted derivatives showed high
regioselectivity in favor of the sterically more accessible C−H
bond (3g−i). In particular, the o-Me derivative is also a
productive substrate (3j), thus indicating high steric tolerance
of this system. Notably, the ester (3d) and halogen groups (3e,
3f) were well tolerated, making further functionalization
possible. In addition, this catalyst system also allowed for the
use of a heterocyclic system (3k).
a
Isolated yields. See the Supporting Information for details.
a
Scheme 3. Scope of Different N-Protecting Groups
In addition to the simple pyridine group, other directing
groups were also investigated (Scheme 2). First, a variety of
pyridinyl directing groups were evaluated, and we were
delighted to find that pyridines with electron-donating (3l−
o) and -withdrawing (3p) groups also participated in this
amidation reaction. Encouragingly, pyridine rings function-
alized with a methyl group at the 3- to 6-positions (3l−o) were
well tolerated, thus indicating high steric tolerance. Tricyclic
benzo[h]quinolone (3q) could also be amidated by this
method. In addition to pyridines, other N-based heterocycles,
such as pyrimidine (3r, 3s) and pyrazole (3t), could also serve
as effective directing groups for this amidation reaction. Next,
we investigated the replacement of the N-based heterocycles
with a more common and synthetically useful moiety. Thus O-
Me oxime have been shown to be an effective directing group,
giving the corresponding amidation products in moderate to
good yields (3u−w). Notably, only monoamidation product
was observed in all cases.
a
Isolated yields. See the Supporting Information for details.
delight, in addition to the N-Cbz group, other common N-
protecting groups (i.e., Moz (3x), Ac (3y), Boc (3z), and even
Fmoc (3aa)) could also be installed by this amidation reaction.
To shed light on the mechanism of amidation, the following
experiments were conducted. First, a cyclometalated Rh(III)
complex 5 could be used as a catalyst precursor and catalyzed
the amination of 1a to provide the desired product 3a in good
yield under the same catalytic conditions, thus indicating the
Next, different N-substituted hydroxylamines were examined
for the catalytic reaction conditions (Scheme 3). To our
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relevancy of C−H activation (eq 1). On the other hand, a
kinetic isotopic effect (KIE) of 1.5 in an intermolecular
under the standard conditions, 3a was obtained in 60% yield,
suggesting that pathway a should be more reliable (eq 4).
In summary, a novel Rh(III)-catalyzed arene C−H amidation
has been described for the first time, which employed the
readily available N-hydroxycarbamates as an nitrogen source. A
variety of N-carbamate protecting groups, such as Cbz, Moz,
Ac, Bocs and even Fmoc, could also be installed by this
amidation reaction, affording a complement to previous
amidation methods. More importantly, this process may
provide a new avenue for intermolecular arene C−H amidation
involving the use of N-hydroxycarbamates as the nitrogen
source.
ASSOCIATED CONTENT
* Supporting Information
■
S
competition experiment was observed, indicating that the C−H
bond cleavage might be not involved in the rate-limiting step
(eq 2).17 Futhermore, the addition of TEMPO (2 equiv) to the
reaction as a radical scavenger caused a slight decrease of the
yield (eq 3).
Experimental procedures, characterization of products, and
1
copies of H and 13C NMR spectra. The material is available
free of charge via the Internet at http://pubs.acs.org.
On the basis of the above observations, a possible mechanism
is proposed (Scheme 4). First, the five-membered rhadacycle A
AUTHOR INFORMATION
Corresponding Authors
■
*E-mail: zhoubing2012@hotmail.com.
*E-mail: spyyx@163.com.
Scheme 4. Proposed Mechanism
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Support of this work by the National Natural Science
Foundation of China (No. 21302200) is gratefully acknowl-
edged.
REFERENCES
■
(1) (a) Rappoport, Z., Ed. The Chemistry of Anilines; Wiley-VCH:
Weinheim, 2007. (b) Amino Group Chemistry: From Synthesis to the
Life Sciences; Ricci, A., Ed.; Wiley-VCH: Weinheim, 2008.
(2) (a) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Acc.
Chem. Res. 1998, 31, 805. (b) Muller, P.; Fruit, C. Chem. Rev. 2003,
103, 2905. (c) Hartwig, J. F. Acc. Chem. Res. 2008, 41, 1534. (d) Surry,
D. S.; Buchwald, S. L. Angew. Chem., Int. Ed. 2008, 47, 6338.
(e) Monnier, F.; Taillefer, M. Angew. Chem., Int. Ed. 2009, 48, 6954.
(f) Armstrong, A.; Collins, J. C. Angew. Chem., Int. Ed. 2010, 49, 2286.
(g) Qiao, J.-X.; Lam, P. Y. S. Synthesis 2011, 6, 829. (h) Zhang, M.
Synthesis 2011, 21, 3408. (i) Mei, T.-S.; Kou, L.; Ma, S.; Engle, K. M.;
Yu, J.-Q. Synthesis 2012, 44, 1778.
(3) (a) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem.
Soc. Rev. 2009, 38, 3242. (b) Xu, L.-M.; Yang, Z.; Shi, Z.-J. Chem. Soc.
Rev. 2010, 39, 712. (c) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010,
110, 1147. (d) Yeung, C. S.; Dong, V. M. Chem. Rev. 2011, 111, 1215.
(e) Ackermann, L. Chem. Rev. 2011, 111, 1315. (f) Wencel-Delord, J.;
Droge, T.; Liu, F.; Glorius, F. Chem. Soc. Rev. 2011, 40, 4740.
(g) Yamaguchi, J.; Yamaguchi, A. D.; Itami, K. Angew. Chem., Int. Ed.
2012, 51, 8960. (h) Wencel-Delord, J.; Glorius, F. Nat. Chem. 2013, 5,
369.
is formed through the coordination of 2-phenylpyridine to the
rhodium center and a subsequent ortho C−H bond activation.18
Coordination of B, generated from oxidation of 2a in situ, to A
gives C, which was transformed into seven-membered rhoda-
cycle D by migratory insertion or nucleophilic addition. D is
protonated to give the hydroxylamine intermediate 4a, and the
Rh(III) catalyst is regenerated (path a). Alternatively, 2a could
react with the Rh(III) center directly, giving the intermediate E
which undergoes reductive elimination to deliver the
intermediate 4a and Rh(I) catalyst (path b). Then oxidation
of the Rh(I) intermediate with Ag(I) slat regenerates the
Rh(III) catalyst. Oxidation of 4a with silver slat or air gives the
nitroxide F, which was transformed into aminyl radicals G via
dimerization and subsequent fragmentation, similarly to the
dimerization of peroxyl radicals. Finally, hydrogen abstraction
from solvents or 4a affords the prodcuct 3a.
(4) Selected reviews on C−H amination: (a) Beccalli, E. M.;
Broggini, G.; Martinelli, M.; Sottocornola, S. Chem. Rev. 2007, 107,
5318. (b) Collet, F.; Dodd, R. H.; Dauban, P. Chem. Commun. 2009,
5061. (c) Cho, S. H.; Kim, J. Y.; Kwak, J.; Chang, S. Chem. Soc. Rev.
2011, 40, 5068. (d) Stokes, B. J.; Driver, T. G. Eur. J. Org. Chem. 2011,
4071.
We next carried out an experiment to probe the reaction
pathway. When the freshly prepared B was used as the reagent
594
dx.doi.org/10.1021/ol403477w | Org. Lett. 2014, 16, 592−595

Organic Letters
Letter
(5) (a) Monguchi, D.; Fujiwara, T.; Furukawa, H.; Mori, A. Org. Lett.
2009, 11, 1607. (b) Wang, Q.; Schreiber, S. L. Org. Lett. 2009, 11,
5178. (c) Cho, S. H.; Kim, J. Y.; Lee, S. Y.; Chang, S. Angew. Chem.,
Int. Ed. 2009, 48, 9127. (d) Kim, J. Y.; Cho, S. H.; Joseph, J.; Chang, S.
Angew. Chem., Int. Ed. 2010, 49, 9899. (e) Zhao, H.; Wang, M.; Su, W.;
Hong, M. Adv. Synth. Catal. 2010, 352, 1301. (f) Miyasaka, M.;
Hirano, K.; Satoh, T.; Kowalczyk, R.; Bolm, C.; Miura, M. Org. Lett.
2011, 13, 359.
(6) (a) Chen, X.; Hao, X.-S.; Goodhue, C. E.; Yu, J.-Q. J. Am. Chem.
Soc. 2006, 128, 6790. (b) Thu, H.-Y.; Yu, W.-Y.; Che, C.-M. J. Am.
Chem. Soc. 2006, 128, 9048. (c) Uemura, T.; Imoto, S.; Chatani, N.
Chem. Lett. 2006, 35, 842. (d) Shuai, Q.; Deng, G.; Chua, Z.; Bohle, D.
S.; Li, C.-J. Adv. Synth. Catal. 2010, 352, 632. (e) Xiao, B.; Gong, T.-J.;
Xu, J.; Liu, Z.-J.; Liu, L. J. Am. Chem. Soc. 2011, 133, 1466. (f) Tran, L.
D.; Roane, J.; Daugulis, O. Angew. Chem., Int. Ed. 2013, 52, 6043.
(g) Zhao, H.; Shang, Y.; Su, W. Org. Lett. 2013, 15, 5106.
(7) For use of O-protected hydroxylamines, chloroamines, and NFSI
as the nitrogen source, see: (a) Ng, K.-H.; Chan, A. S. C.; Yu, W.-Y. J.
Am. Chem. Soc. 2010, 132, 12862. (b) Kawano, T.; Hirano, K.; Satoh,
T.; Miura, M. J. Am. Chem. Soc. 2010, 132, 6900. (c) Sun, K.; Li, Y.;
Xiong, T.; Zhang, J.; Zhang, Q. J. Am. Chem. Soc. 2011, 133, 1694.
(d) Yoo, E. J.; Ma, S.; Mei, T.-S.; Chan, K. S. L.; Yu, J.-Q. J. Am. Chem.
Soc. 2011, 133, 7652. (e) Matsuda, N.; Hirano, K.; Satoh, T.; Miura,
M. Org. Lett. 2011, 13, 2860. (f) Ng, K.-H.; Zhou, Z.; Yu, W.-Y. Org.
Lett. 2012, 14, 272. (g) Grohmann, C.; Wang, H.; Glorius, F. Org. Lett.
2012, 14, 656. (h) Tang, R.-J.; Luo, C.-P.; Yang, L.; Li, C.-J. Adv. Synth.
Catal. 2013, 355, 869. (i) Yu, S.; Wan, B.; Li, X. Org. Lett. 2013, 15,
3706. (j) Grohmann, C.; Wang, H.; Glorius, F. Org. Lett. 2013, 15,
3014. (k) Ng, K.-H.; Zhou, Z.; Yu, W.-Y. Chem. Commun. 2013, 49,
7031. (l) Zhou, B.; Du, J.; Yang, Y.; Li, Y. Org. Lett. 2013, 15, 2934.
(8) For the use of azides as the nitrogen source, see: (a) Kim, J. Y.;
Park, S. H.; Ryu, J.; Cho, S. H.; Kim, S. H.; Chang, S. J. Am. Chem. Soc.
2012, 134, 9110. (b) Shi, J.; Zhou, B.; Yang, Y.; Li, Y. Org. Biomol.
Chem. 2012, 10, 8953. (c) Shin, K.; Baek, Y.; Chang, S. Angew. Chem.,
Int. Ed. 2013, 125, 8189. (d) Ryu, J.; Shin, K.; Park, S. H.; Kim, J. Y.;
Chang, S. Angew. Chem., Int. Ed. 2012, 51, 9904. (e) Yu, D. G.; Suri,
M.; Glorius, F. J. Am. Chem. Soc. 2013, 135, 8802. (f) Thirunavukkar-
asu, V. S.; Raghuvanshi, K.; Ackermann, L. Org. Lett. 2013, 15, 3286.
(g) Kim, J.; Kim, J.; Chang, S. Chem.Eur. J. 2013, 19, 7328.
(h) Yadav, M. R.; Rit, R. K.; Sahoo, A. K. Org. Lett. 2013, 15, 1638.
(i) Zheng, Q.-Z.; Liang, Y.-F.; Qin, C.; Jiao, N. Chem. Commun. 2013,
49, 5654. (j) Zhou, B.; Yang, Y.; Shi, J.; Feng, H.; Li, Y. Chem.Eur. J.
2013, 19, 10511.
(12) For Rh(III)-catalyzed C−S bond formation, see: Yang, Y.; Hou,
W.; Qin, L.; Du, J.; Feng, H.; Zhou, B.; Li, Y. Chem.Eur. J. 2013,
DOI: 10.1002/chem.201303730.
(13) For Rh(III)-catalyzed C−H activation and subsequent coupling
with diazo compounds, sodium azide, aziridines, and cyano, see:
(a) Chan, W.-W.; Lo, S.-F.; Zhou, Z.; Yu, W.-Y. J. Am. Chem. Soc.
2012, 134, 13565. (b) Hyster, T. K.; Ruhl, K. E.; Rovis, T. J. Am.
Chem. Soc. 2013, 135, 5364. (c) Shi, Z.; Koester, D. C.; Boultadakis-
Arapinis, M.; Glorius, F. J. Am. Chem. Soc. 2013, 135, 12204. (d) Xie,
F.; Qi, Z.; Li, X. Angew. Chem., Int. Ed. 2013, 52, 11862. (e) Li, X.; Yu,
S.; Wang, F.; Wan, B.; Yu, X. Angew. Chem., Int. Ed. 2013, 52, 2577.
(f) Gong, T.-J.; Xiao, B.; Cheng, W.-M.; Su, W.; Xu, J.; Liu, Z.-J.; Liu,
L.; Fu, Y. J. Am. Chem. Soc. 2013, 135, 10630.
(14) Selected Rh(III)-catalyzed C−H functionalization with alkynes
and alkenes: (a) Liu, B.; Fan, Y.; Gao, Y.; Sun, C.; Xu, C.; Zhu, J. J. Am.
Chem. Soc. 2013, 135, 468. (b) Wang, H.; Schroder, N.; Glorius, F.
Angew. Chem., Int. Ed. 2013, 52, 5386. (c) Wang, H.; Grohmann, C.;
Nimphius, C.; Glorius, F. J. Am. Chem. Soc. 2012, 134, 19592.
(d) Zhen, W.; Wang, F.; Zhao, M.; Du, Z.; Li, X. Angew. Chem., Int. Ed.
2012, 51, 11819. (e) Li, B.-J.; Wang, H.-Y.; Zhu, Q.-L.; Shi, Z.-J.
Angew. Chem., Int. Ed. 2012, 51, 3948. (f) Pham, M. V.; Ye, B.; Cramer,
N. Angew. Chem., Int. Ed. 2012, 51, 10610. (g) Ye, B.; Cramer, N.
Science 2012, 338, 504. (h) Patureau, F. W.; Besset, T.; Kuhl, N.;
Glorius, F. J. Am. Chem. Soc. 2011, 133, 2154. (i) Hyster, T. K.; Rovis,
T. J. Am. Chem. Soc. 2010, 132, 10565. (j) Umeda, N.; Tsurugi, H.;
Satoh, T.; Miura, M. Angew. Chem., Int. Ed. 2008, 47, 4019. (k) Stuart,
D. R.; Bertrand-Laperle, M.; Burgess, K. M. N.; Fagnou, K. J. Am.
Chem. Soc. 2008, 130, 16474. (l) Ueura, K.; Satoh, T.; Miura, M. Org.
Lett. 2007, 9, 1407. (m) Ueura, K.; Satoh, T.; Miura, M. J. Org. Chem.
2007, 72, 5362.
(15) Forrester, A. R.; Fullerton, J. D.; McConnachie, G. J. Chem. Soc.,
Perkin Trans. 1 1983, 1759.
(16) CCDC 973749 (3a).
(17) Simmons, E. M.; Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51,
3066.
(18) (a) Li, L.; Brennessel, W. W.; Jones, W. D. J. Am. Chem. Soc.
2008, 130, 12414. (b) Li, L.; Brennessel, W.; Jones, W. D.
Organometallics 2009, 28, 3492.
(9) (a) Tsai, A. S.; Tauchert, M. E.; Bergman, R. G.; Ellman, J. A. J.
Am. Chem. Soc. 2011, 133, 1248. (b) Li, Y.; Li, B.-J.; Wang, W.-H.;
Huang, W.-P.; Zhang, X.-S.; Chen, K.; Shi, Z.-J. Angew. Chem., Int. Ed.
2011, 50, 2115. (c) Yang, L.; Correia, C. A.; Li, C.-J. Adv. Synth. Catal.
2011, 353, 1269. (d) Zhu, C.; Xie, W.; Falck, J. R. Chem.Eur. J.
2011, 17, 12591. (e) Tauchert, M. E.; Incarvito, C. D.; Rheingold, A.
L.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2012, 134, 1482.
(f) Li, Y.; Zhang, X.-S.; Chen, K.; He, K.-H.; Pan, F.; Li, B.-J.; Shi, Z.-J.
Org. Lett. 2012, 14, 636. (g) Hesp, K. D.; Bergman, R. G.; Ellman, J. A.
Org. Lett. 2012, 14, 2304. (h) Zhou, B.; Yang, Y.; Li, Y. Chem.
Commun. 2012, 48, 5163. (i) Li, Y.; Zhang, X.-S.; Zhu, Q.-L.; Shi, Z.-J.
Org. Lett. 2012, 14, 4498. (j) Zhou, B.; Yang, Y.; Lin, S.; Li, Y. Adv.
Synth. Catal. 2013, 355, 360. (k) Hou, W.; Zhou, B.; Yang, Y.; Feng,
H.; Li, Y. Org. Lett. 2013, 15, 1814. (l) Zhou, B.; Hou, W.; Yang, Y.; Li,
Y. Chem.Eur. J. 2013, 19, 4701. (m) Lian, Y.; Bergman, R. B.; Lavis,
L. D.; Ellman, J. A. J. Am. Chem. Soc. 2013, 135, 7122.
(10) Zhou, B.; Du, J.; Yang, Y.; Feng, H.; Li, Y. Org. Lett. 2013, 15,
6302.
(11) For recent reviews on RhIII-catalyzed C−H activation:
(a) Satoh, T.; Miura, M. Chem.Eur. J. 2010, 16, 11212.
(b) Colby, D. A.; Tsai, A. S.; Bergman, R. G.; Ellman, J. A. Acc.
Chem. Res. 2012, 45, 814. (c) Song, G.; Wang, F.; Li, X. Chem. Soc. Rev.
2012, 41, 3651. (d) Patureau, F. W.; Wencel-Delord, J.; Glorius, F.
Aldrichimica Acta 2012, 45, 31. (e) Chiba, S. Chem. Lett. 2012, 41,
1554. (f) Zhu, C.; Wang, R.; Falck, J. R. Chem.Asian J. 2012, 7,
1502.
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