Carboxylate-Assisted Iridium-Catalyzed C-H Amination of Arenes with Biologically Relevant Alkyl Azides

Article abstract of DOI:10.1002/chem.201504880

An iridium-catalyzed C-H amination of arenes with a wide substrate scope is reported. Benzamides with electron-donating and -withdrawing groups and linear, branched, and cyclic alkyl azides are all applicable. Cesium carboxylate is crucial for both reactivity and regioselectivity of the reactions. Many biologically relevant molecules, such as amino acid, peptide, steroid, sugar, and thymidine derivatives can be introduced to arenes with high yields and 100 % chiral retention. Ir responsible! A direct C-H amination between benzamide derivatives and various alkyl azides was achieved using iridium catalysis (see scheme; NTf=trifluoromethanesulfonyl amide). Cesium carboxylate was found to be the promoter and regiocontroller of this reaction. By this method, many biological active molecules can be introduced to benzamide components with high yields and 100 % chiral retention.

Full text of DOI:10.1002/chem.201504880

DOI: 10.1002/chem.201504880
Communication
&
Amination
Carboxylate-Assisted Iridium-Catalyzed CÀH Amination of Arenes
with Biologically Relevant Alkyl Azides
[a]
[a]
[a]
[a]
[a]
[a, b]
Tao Zhang, Xuejiao Hu, Zhen Wang, Tiantian Yang, Hao Sun, Guigen Li,
and
[a]
Hongjian Lu*
Abstract: An iridium-catalyzed CÀH amination of arenes
with a wide substrate scope is reported. Benzamides with
electron-donating and -withdrawing groups and linear,
branched, and cyclic alkyl azides are all applicable. Cesium
carboxylate is crucial for both reactivity and regioselectivi-
ty of the reactions. Many biologically relevant molecules,
such as amino acid, peptide, steroid, sugar, and thymidine
derivatives can be introduced to arenes with high yields
and 100% chiral retention.
Figure 1. Alkylamine sources in directed CÀH amination.
Given the ubiquity of arylamines in natural products, drug mol-
ecules, organic optoelectronic materials, and synthetic inter-
mediates, facile methods to introduce nitrogen substituents
onto aromatic rings have been a major focus of new method-
edge, primary alkylamines and their analogues have been un-
derdeveloped as substrates for the direct CÀH amination, even
[
5,6]
though they are abundant in nature (Figure 1a).
The report-
ed methods normally require external oxidants and/or bases;
this limits their practical application, as many compounds, es-
pecially biological active compounds, are oxidation/base sensi-
tive. Therefore, a method of direct CÀH amination with high
functional group tolerance is still needed.
[
1]
ology development. Extensive research on Cu- and Pd-cata-
lyzed CÀN cross coupling reactions of aryl(pseudo)halide sub-
strates led to the development of Ullmann–Goldberg, Buch-
[2]
wald–Hartwig, and Chan–Lam aminations. As aryl(pseudo)ha-
lides are not always readily accessible, a metal-catalyzed ami-
nation of arenes through CÀH activation has recently emerged
Azides are an important source of amines and have unique
advantages. For example, they are easy to prepare, green (gen-
[3]
as an alternative method for its evident advantage. However,
there are two major challenges of a direct CÀH amination.
First, the CÀH bond has high energy barrier to dissociate;
second, the newly formed amino groups have the tendency to
retain coordination with the metal catalysts. As a consequence,
the direct CÀH aminations developed to date are most limited
to amino sources with a strong electron-withdrawing group,
such as sulfonyl and carbonyl group, conjugated to the nitro-
erate N gas as the sole by-product), and reactions with azides
2
could be conducted under mild conditions (oxidative or basic
[
3f]
conditions are not necessary). In addition, due to the ex-
panding popularity of click chemistry, many alkyl azides, in-
[
7]
cluding biologically relevant ones, are readily available. How-
ever, applications of alkyl azides as an alkylamine source in
metal-catalyzed direct CÀH amination reactions are less ex-
plored. To the best of our knowledge, only three reports have
been described recently that employs alkyl azides as the sub-
[
3]
[4a–d]
gen atom. Recently, secondary alkylamines
and their ana-
[4e–h]
[8a,b]
[8c]
logues, for example, N-chloroamines
and N-hydroxyamine-
strates in Rh
and Ir catalytic systems. The major limita-
[4i–p]
s
have also been widely used in the metal-catalyzed CÀH
tions of these methods are i) the azide substrates and/or
arenes need to be electron-deficient to give high yields, and
ii) only linear alkyl azides are used in these reactions; branched
alkyl azides are not applicable (Figure 1b).
amination of chelation-group-containing substrates, probably
benefitting from the steric hindrance of newly formed tertiary
amino groups (Figure 1a). However, to the best of our knowl-
Inspired by the Ir-catalyzed direct CÀH amination of arenes
[
8c,9]
[10]
with organic azides
and our previous studies, we herein
[
a] T. Zhang, X. Hu, Z. Wang, T. Yang, H. Sun, Prof. G. Li, Prof. H. Lu
Institute of Chemistry & BioMedical Sciences
School of Chemistry and Chemical Engineering
Nanjing University, Nanjing, (China)
report a method of Ir-catalyzed intermolecular CÀH amination
of arenes. With the promotion of CsOAc, this method is well
applicable to linear, branched, and cyclic alkyl azides; it is also
suitable to benzamides bearing electron-donating and with-
drawing groups (Figure 1c).
E-mail: hongjianlu@nju.edu.cn
[
b] Prof. G. Li
Department of Chemistry and Biochemistry
Amination of the CÀH bond at the ortho-position of
benzamide can produce anthranilamide, a motif found in
Texas Tech University, Lubbock, TX 79409-1061 (USA)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201504880.
[
11]
many drug candidates. Therefore, we chose benzamide and
Chem. Eur. J. 2016, 22, 2920 – 2924
2920
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
[
a]
[a]
Table 1. Optimization of reaction conditions.
Table 2. Scope of benzamides 1.
[b]
Entry
Silver salt Additive
Solvent
T [8C] Yield [%]
1
2
3
4
5
6
7
8
9
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
AgNTf
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
NaOAc
NaOAc
AgOAc
HOAc/Li
KOAc
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
dioxane
THF
benzene
o-xylene
50
–
–
8
28
<5
8
13
57
–
140
140
140
140
140
140
140
140
140
140
140
140
140
[
c]
2
CO
3
HOAc
CsOPiv
CsOAc
CsF
1
0
Cs
2
CO
3
–
1
1
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
33
36
30
54
14
77
29
15
58
70
88
1
1
1
1
1
1
1
1
2
2
2
3
4
5
6
7
8
9
0
1
CF
3
CH
2
OH 140
140
PhCl
PhCl
PhCl
PhCl
PhCl
PhCl
PhCl
AgOTf
AgBF
AgSbF
140
140
140
150
120
120
[a] Reaction conditions: 1 (0.3 mmol), 2a (0.2 mmol), isolated yield.
4
6
AgNTf
AgNTf
AgNTf
2
2
We then studied the effects of meta-substitution on the ben-
zamide 1 (Table 3). Meta-substitution can affect both the acces-
sibility and electron density of the reaction site, which are the
major factors controlling and differentiating the reactivity and
[
d]
2
2
2
87
[
a] Reaction conditions: 1a (0.36 mmol), 2a (0.2 mmol). [b] Yield was cal-
1
culated based on crude H NMR spectra using CH
[
(
2
Br
(1.0 equiv). [d] Optimized conditions: 1a
0.3 mmol), 2a (0.2 mmol), [{IrCp*Cl (4 mol%), AgNTf (16 mol%),
2
as the standard.
2 3
c] LiOAc (1.0 equiv)/Li CO
[
12]
selectivity of CÀH bonds. In this reaction, the CÀH amination
generally takes place predominately at the less hindered posi-
tion with high regioselectivity (3qa–va). However, when the
meta-substituent on the benzamide was chlorine, bromine,
and methoxyl, a mixture of regioisomers was obtained (3wa–
ya, 3’wa–ya). This can be explained by the ortho-directing
2
}
2
]
2
CsOAc (50 mol%), PhCl (2 mL).
N (CH ) CO Me (2a) as the substrates (Table 1 and Table S1 in
3
2 3
2
the Supporting Information). We began our research with the
[8c]
Chang’s optimized amination conditions; using [{IrCp*Cl } ]/
2
2
AgNTf as the catalyst and NaOAc as the additive, no desired
Table 3. Cesium carboxylate controlled regioselectivity of meta-substitut-
ed benzamides 1.
2
[a]
product was formed even after increasing the reaction temper-
ature to 1408C (Table 1, entries 1 and 2). Subsequently, a variety
of carboxylates (entries 3–8) and cesium salts (entries 9 and 10)
were screened in DCE, and we were delighted to discover that
the desired product 3aa was obtained in 57% yield when
CsOAc was used as the additive (entry 8). After solvents (en-
tries 11–16), silver salts (entries 17–19), temperatures (entries 20
and 21), and the stoichiometry of additive (entry 22) were
screened, the optimal conditions for this amination were
found (entry 22). No desired product was formed in the
[
8a,b]
presence of other metals, such as [{RhCp*Cl } ]/AgNTf ,
2
2
2
[
(
RhCp*(MeCN) ](SbF ) , [{Ru(p-cymene)Cl2}2], and Pd(OAc)2
3 6 2
Table S1 in the Supporting Information).
We then explored the scope of this reaction with a series of
substrates (1; Table 2). Benzamides with various N-alkyl substi-
tutions could be used in the reaction (3aa–ea). Both electron-
withdrawing and -donating groups at the para-position of the
phenyl ring were well tolerated (3 fa–na). Functional groups,
such as ester, halogen, methoxyl, and amino, were also tolerat-
ed. Finally, the reaction efficiency is independent of the ortho-
substitution of the phenyl ring (3oa–pa).
[a] 1 (0.3 mmol), 2a (0.2 mmol), CsOAc (50 mol%), PhCl (2 mL), isolated
yield. [b] The ratio of the products 3/3’. [c] 1 (0.3 mmol), 2a (0.2 mmol),
2 2 2
[{IrCp*Cl } ] (8 mol%), AgNTf (32 mol%), CsOPiv (50 mol%), PhCl (2 mL).
Chem. Eur. J. 2016, 22, 2920 – 2924
www.chemeurj.org
2921
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
effect of the strongly electronegative substituents, an outcome
that was also observed in the rhodium, ruthenium, and cobalt-
[12]
catalyzed CÀH activation reactions.
Interestingly, after
screening various additives (Table S2 in the Supporting Infor-
mation), we found that both the reactivity and regioselectivity
could be controlled by the carboxylate salts. When the cesium
salt with a bulky carboxylate ligand (CsOPiv) was used as the
additive, the high regioselectivity was regained and the reac-
tions predominantly gave the products with substitutes at the
less hindered site.
Next, we examined the scope of the alkyl azides 2 (Table 4).
In addition to the linear azides with different functional
groups, cyclic and branched alkyl azides were also well tolerat-
ed (3ab–ai). a,a,a-Trisubstituted alkyl azides, substrates with
a high steric hindrance, successfully formed the anthranila-
mides (3aj–al), which are often difficult to synthesize through
Scheme 1. Mechanistic studies.
[13a]
traditional Pd-catalyzed cross-coupling reactions.
This is es-
pecially important because bulky alkyl-substituted amines are
frequently found in biologically active molecules, in which they
increase lipophilicity and/or improve metabolic stability of
[
13b]
those molecules.
[
a]
Table 4. Scope of alkyl azides 2.
Figure 2. Proposed mechanism.
According to the aforementioned experiments and previous
[
8,9]
studies,
a possible mechanistic pathway is proposed in
Figure 2. First, the active Ir species, [IrCp*(O CR)(NTf )], is
2
2
formed by the [{IrCp*Cl } ], AgNTf , and RCO Cs. This coordi-
2
2
2
2
nates with benzamide 1, inducing the CÀH bond cleavage
through transition state I, in which the regioselectivity can be
[
a] 1a (0.3 mmol), 2 (0.2 mmol), PhCl (2 mL), isolated yield.
[
12a]
controlled by both the substrate and carboxylate.
This pro-
III
duces the cyclometalated Ir complex II. Coordination of the
alkyl azide with the complex II forms III, which undergoes mi-
The control experiments shows that i) [{Ir(Cp*)Cl } ] and
2
2
AgNTf are essential for this reaction, while CsOAc is a great
gratory insertion, releasing N , to give IV. Finally, protonolysis
2
2
promoter, ii) AgNTf and CsOAc cannot be replaced by AgOAc,
of IV provides the amination product 3 and regenerates the
active Ir species.
2
iii) AgNTf (8 mol%) is the lowest amount needed to afford the
2
product in good yield, and iv) the radical inhibitor TEMPO (one
equivalent) had no significant effect on the reaction (Table S3
in the Supporting Information). To study the reaction mecha-
nism further, a series of experiments were also carried out
Finally, we examined the compatibility of this method with
several biological active molecules (Table 5). The azide deriva-
tives of steroids, which were readily synthesized from their
original bioactive structures (see the Supporting Information),
were used as substrates to produce 3am–ao in high to excel-
lent yields. Natural amino acid leucine and dipeptide-based
alkyl azides were also compatible (3ap–ar). Both of the deriva-
tive of glucosamine and drug zidovudine underwent this ami-
nation reaction with good yields (3as–at). Steroid-based azides
also reacted with both electron-withdrawing and -donating
groups substituted benzamides to form the desired products
in high yields (3gm–gn and 3mm–mn). It is worth mentioning
(
Scheme 1). A significant primary kinetic isotope effect was ob-
served (K /K =4.0), while no H/D scrambling occurred in the
H
D
reaction between 1a and [D ]-1a. We then performed a com-
5
petitive experiment, which revealed that electron-rich arenes
III
are preferred in the reaction. The cyclometalated Ir complex II
(
Figure 2) was proposed to be involved in the catalytic cycle,
because iridium complex 4 can catalyze direct CÀH amination
smoothly.
Chem. Eur. J. 2016, 22, 2920 – 2924
www.chemeurj.org
2922
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
reduced pressure and the crude reaction mixture was purified by
silica gel column chromatography with n-hexane/EtOAc as an
eluent to give the desired product.
[
a]
Table 5. Applications of biologically relevant azides.
Acknowledgements
We are grateful for financial support by National Natural Sci-
ence Foundation of China (21332005, 21472085).
Keywords: amides · azides · CÀH activation · homogeneous
catalysis · iridium
[1] a) N. K. Boaen, M. A. Hillmyer, Chem. Soc. Rev. 2005, 34, 267; b) R. Hili,
A. K. Yudin, Nat. Chem. Biol. 2006, 2, 284; c) The Chemistry of Anilines
(Ed.: Z. Rappoport), Wiley-VCH, Weinheim (Germany), 2007; d) A. Ricci,
in Amino Group Chemistry: From Synthesis to the Life Sciences, Wiley-
VCH, Weinheim (Germany), 2008.
[
[
2] a) G. Evano, N. Blanchard, M. Toumi, Chem. Rev. 2008, 108, 3054; b) I. P.
Beletskaya, A. V. Cheprakov, Organometallics 2012, 31, 7753; c) J. Bariw-
al, E. van der Eycken, Chem. Soc. Rev. 2013, 42, 9283.
3] For selected reviews of CÀH amination through a CÀH activation path-
way, see: a) T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147;
b) S. H. Cho, J. Y. Kim, J. Kwak, S. Chang, Chem. Soc. Rev. 2011, 40, 5068;
c) G. Y. Song, F. Wang, X. W. Li, Chem. Soc. Rev. 2012, 41, 3651; d) N.
Kuhl, N. Schrçder, F. Glorius, Adv. Synth. Catal. 2014, 356, 1443; e) M. L.
Louillat, F. W. Patureau, Chem. Soc. Rev. 2014, 43, 901; f) K. Shin, H. Kim,
S. Chang, Acc. Chem. Res. 2015, 48, 1040; g) P. Subramanian, G. C.
Rudolf, K. P. Kaliappan, Chem. Asian J. 2015, DOI: 10.1002/
asia.201500361.
[
a] 1 (0.3 mmol), 2 (0.2 mmol), PhCl (2 mL), isolated yield. [b] Gram scale
reaction. [c] Isolated yield of a mixture of 3at and 3at’ (3at(R=Boc)/
at’(R=H)=3.7/1), see Scheme S2 in the Supporting Information for de-
3
tails.
[
4] For selected examples of CÀH activation/amination with secondary al-
kylamines or their analogues to form tertiary amines, see: a) L. D. Tran,
J. Roane, O. Daugulis, Angew. Chem. Int. Ed. 2013, 52, 6043; Angew.
Chem. 2013, 125, 6159; b) Q. Li, S. Y. Zhang, G. He, Z. Y. Ai, W. A. Nack,
G. Chen, Org. Lett. 2014, 16, 1764; c) A. M. Martínez, N. Rodriguez, R. G.
Arrayas, J. C. Carretero, Chem. Commun. 2014, 50, 2801; d) Q. Q. Yan,
Z. K. Chen, W. L. Yu, H. Yin, Z. X. Liu, Y. H. Zhang, Org. Lett. 2015, 17,
2482; e) T. Kawano, K. Hirano, T. Satoh, M. Miura, J. Am. Chem. Soc.
that the reaction can be scaled up to gram scale with a similarly
high yield (3am; 1.51 g, 90%). Impressively, the chirality of all
these products is 100% retained.
In summary, we have developed an Ir-catalyzed CÀH amina-
tion of arenes using alkyl azides as the primary alkylamine
source. We found that cesium carboxylate is crucial and can
control both the reactivity and regioselectivity of the reaction.
This method has very wide substrate scope; both linear and
sterically hindered branched alkyl amino groups can be insert-
ed to various benzamides with high yields. This reaction does
not require oxidative conditions and is therefore friendly for
many biologically relevant molecules, such as sugar, peptide,
steroid, and thymidine derivatives. Moreover, a complete trans-
fer of chirality is obtained under these reaction conditions. We
expect that this method can serve as a robust method to syn-
thesize anthranilamide derivatives, which are found in many
drug molecules.
2
6
010, 132, 6900; f) C. Grohmann, H. Wang, F. Glorius, Org. Lett. 2012, 14,
56; g) F.-N. Ng, Z. Zhou, W.-Y. Yu, Chem. Eur. J. 2014, 20, 4474; h) T.
Matsubara, S. Asako, L. Ilies, E. Nakamura, J. Am. Chem. Soc. 2014, 136,
46; i) E. J. Yoo, S. Ma, T.-S. Mei, K. S. L. Chan, J.-Q. Yu, J. Am. Chem. Soc.
2011, 133, 7652; j) Z. Dong, G, Dong, J. Am. Chem. Soc. 2013, 135,
8350; k) M. Shang, S.-H. Zeng, S.-Z. Sun, H.-X. Dai, J.-Q. Yu, Org. Lett.
6
1
2
2
013, 15, 5286; l) K. Wu, Z. L. Fan, Y. Xue, Q. Z. Yao, A. Zhang, Org. Lett.
014, 16, 42; m) Q. Gou, G. Liu, Z. Liu, J. Qin, Chem. Eur. J. 2015, 21,
15491; n) J. He, T. Shigenari, J.-Q. Yu, Angew. Chem. Int. Ed. 2015, 54,
6545; Angew. Chem. 2015, 127, 6645; o) H. Shi, D. J. Babinski, T. Ritter, J.
Am. Chem. Soc. 2015, 137, 3775; p) D. Zhu, G. Yang, J. He, L. Chu, G.
Chen, W. Gong, K. Chen, M. D. Eastgate, J.-Q. Yu, Angew. Chem. Int. Ed.
2015, 54, 2497; Angew. Chem. 2015, 127, 2527.
[
5] For examples of CÀH amination with primary alkylamines; Daugulis
group reported a Cu-catalyzed CÀH amination of N-benzoyl-8-amino-
quinoline with alkyl amines. In the case of primary alkylamines (4 exam-
ples), moderate to low product yields (20–52%) were obtained, see:
ref. [4a]. Chang group just reported an Ir-catalyzed CÀH amination of
arenes with primary alkylamines under oxidative conditions (3.2 equiv
of AgNTf
665.
2
as the oxidant), see: H. Kim, S. Chang, ACS Catal. 2015, 5,
Experimental Section
6
[
6] For examples of CÀH amination with primary alkylamine analogues; Rh-
catalyzed CÀH amination of acetophenone o-methyloximes with N-(ter-
tiary alkyl)-N-chloroamines, see: a) K. H. Ng, Z. Y. Zhou, W. Y. Yu, Chem.
Commun. 2013, 49, 7031; Rh-catalyzed CÀH amination of phenidones
with N-alkyl-o-benzoyl-hydroxyamines, see: b) Y. Xue, Z. Fan, X. Jiang, K.
Wu, M. Wang, C. Ding, Q. Yao, A. Zhang, Eur. J. Org. Chem. 2014, 7481;
electrooxidative coupling of functional primary alkylamines with aro-
matics, see: c) T. Morofuji, A. Shimizu, J. Yoshida, J. Am. Chem. Soc.
2015, 137, 9816.
To a screw-capped vial equipped with a spinvane triangular-
shaped Teflon stir bar were added benzamide (1, 0.3 mmol), alkyl
azides (2, 0.2 mmol), [{IrCp*Cl } ] (6.4 mg, 4 mol%), AgNTf2
2
2
(
12.4 mg, 16 mol%), CsOAc (19.2 mg, 50 mol%), and chloroben-
zene (2 mL) under N conditions. The reaction mixture was stirred
2
in a pre-heated oil bath at 1208C for 24 h. The reaction was cooled
to room temperature, filtered through a pad of celite, and then
washed with CH Cl (10 mL”3). The solvents were removed under
2
2
Chem. Eur. J. 2016, 22, 2920 – 2924
www.chemeurj.org
2923
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Communication
[
[
[
7] a) R. Huisgen, Pure Appl. Chem. 1989, 61, 613; b) H. C. Kolb, K. B. Sharp-
less, Drug Discovery Today 2003, 8, 1128; c) S. Bräse, C. Gil, K. Knepper,
V. Zimmermann, Angew. Chem. Int. Ed. 2005, 44, 5188; Angew. Chem.
[10] a) H. Lu, X. P. Zhang, Chem. Soc. Rev. 2011, 40, 1899; b) H. Lu, C. Q. Li, H.
Jiang, C. L. Lizardi, X. P. Zhang, Angew. Chem. Int. Ed. 2014, 53, 7028;
Angew. Chem. 2014, 126, 7148; c) M. A. Ali, X. Yao, H. Sun, H. Lu, Org.
Lett. 2015, 17, 1513.
[11] For selected examples: betrixaban (CID 10275777) and tariquidar (CID
148201).
[12] a) L. Ackermann, Chem. Rev. 2011, 111, 1315; b) B. Punji, W. F. Song, G. A.
Shevchenko, L. Ackermann, Chem. Eur. J. 2013, 19, 10605; c) D.-C. M.
Schinkel, I. Marek, L. Ackermann, Angew. Chem. Int. Ed. 2013, 52, 3977;
Angew. Chem. 2013, 125, 4069; d) N. J. Webb, S. P. Marsden, S. A. Raw,
Org. Lett. 2014, 16, 4718; e) Y. Zhang, D. H. Wang, S. L. Cui, Org. Lett.
2015, 17, 2494.
[13] a) P. Ruiz-Castillo, D. G. Blackmond, S. L. Buchwald, J. Am. Chem. Soc.
2015, 137, 3085; b) L. Wanka, K. Iqbal, P. R. Schreiner, Chem. Rev. 2013,
113, 3516.
2005, 117, 5320; d) M. Meldal, C. W. Torn, Chem. Rev. 2008, 108, 2952;
e) S. Brase, K. Banert, Organic Azides: Synthesis and Applications, Wiley-
VCH, Weinheim (Germany), 2010.
8] Rhodium-catalyzed CÀH amination of arenes with linear alkyl azides,
see: a) K. Shin, Y. Baek, S. Chang, Angew. Chem. Int. Ed. 2013, 52, 8031;
Angew. Chem. 2013, 125, 8189; b) H. Wang, Y. Yu, X. Hong, Q. Tan, B. Xu,
J. Org. Chem. 2014, 79, 3279; Iridium-catalyzed direct C-7 amination of
indolines with linear alkyl azides, see: c) K. Shin, S. Chang, J. Org. Chem.
2014, 79, 12197.
9] For examples of Ir-catalyzed CÀH amination with sulfonyl, carbonyl,
phosphoryl, and phenyl azides, see: a) J. Ryu, J. Kwak, K. Shin, D. Lee, S.
Chang, J. Am. Chem. Soc. 2013, 135, 12861; b) D. Lee, Y. Kim, S. Chang,
J. Org. Chem. 2013, 78, 11102; c) T. Kang, Y. Kim, D. Lee, Z. Wang, S.
Chang, J. Am. Chem. Soc. 2014, 136, 4141; d) J. Kim, S. Chang, Angew.
Chem. Int. Ed. 2014, 53, 2203; Angew. Chem. 2014, 126, 2235; e) H. Kim,
J. Park, J. G. Kim, S. Chang, Org. Lett. 2014, 16, 5466; f) C. D. Pan, N. Jin,
H. L. Zhang, J. Han, C. J. Zhu, J. Org. Chem. 2014, 79, 9427.
Received: December 4, 2015
Published online on January 28, 2016
Chem. Eur. J. 2016, 22, 2920 – 2924
www.chemeurj.org
2924
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim