Iodine(III) Reagent-Mediated Intramolecular Amination of 2-Alkenylanilines to Prepare Indoles

Article abstract of DOI:10.1002/adsc.201701551

A variety of 3-substituted and 2,3-disubstituted indoles were synthesized efficiently in good yields through the intramolecular amination of 2-alkenylanilines promoted by readily available iodine(III) reagents in a short reaction time. Mechanistic studies showed that the reaction pathway went through a nitrenium ion and that 3-acetoxy indoline was the key intermediate in the indole formation. The indole product was easily prepared on a gram scale and amination also proceeded smoothly using catalytic 3,5-dimethylphenyl iodine in the presence of mCPBA. Furthermore, the indolo[3,2-a]carbazole scaffold was prepared in good yield in six steps from commercial ortho-iodoaniline. (Figure presented.).

Full text of DOI:10.1002/adsc.201701551

Title: Iodine(III) Reagent-Mediated Intramolecular Amination of 2-
Alkenylanilines to Prepare Indoles
Authors: Chun-Yang Zhao, Kun Li, Yu Pang, Jia-Qing Li, Cui Liang,
Gui-Fa Su, and Dong-Liang Mo
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201701551
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Iodine(III) Reagent-Mediated Intramolecular Amination of 2-
Alkenylanilines to Prepare Indoles
Chun-Yang Zhao,† Kun Li,† Yu Pang, Jia-Qing Li, Cui Liang, Gui-Fa Su*, and Dong-
Liang Mo*
a
State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Science and
Technology of China; School of Chemistry and Pharmaceutical Sciences, Guangxi Normal University, 15 Yu Cai Road,
Guilin 541004, China. E-mail: gfysglgx@163.com; moeastlight@mailbox.gxnu.edu.cn
C.-Y. Zhao and K. Li contributed equally to this work
†
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
heteroatom bonds in modern organic oxidation
indoles were synthesized efficiently in good yields through chemistry and have recently received much attention
Abstract. A variety of 3-substituted and 2,3-disubstituted
the intramolecular amination of 2-alkenylanilines promoted
by readily available iodine(III) reagents in a short reaction
time. Mechanistic studies showed that the reaction pathway
went through a nitrenium ion and that 3-acetoxy indoline
was the key intermediate in the indole formation. The
indole product was easily prepared on a gram scale and
amination also proceeded smoothly using catalytic 3,5-
dimethylphenyl iodine in the presence of mCPBA.
Furthermore, the indolo[3,2-a]carbazole scaffold was
prepared in good yield in six steps from commercial ortho-
iodoaniline.
in indole synthesis as alternatives to traditional
transition-metal-based procedures.[12,13] Muñiz and
coworkers reported a rapid and productive indole
preparation via the intramolecular amination of 2-
vinylanilines using a modified iodine(III) reagent
under mild conditions (Scheme 1-A).[14] This
successful process was based on a sterically
congested hypervalent iodine compound from the
family of Koser reagents, comprising iodosobenzene
combined with 2,4,5-trisisopropylbenzene sulfonic
acid. Modification of the Koser reagent anion to
improve the reactivity of the iodine(III) reagent was
key in this method. The modified Koser reagent anion
is not readily commercially but could be prepared in
one step from commercial materials[15]. However, 2-
Keywords: amination; 2-alkenylaniline; hypervalent iodine
compound; indole; C−N bond formation
vinylaniline
substrates
were
limited
to
monosubstituted terminal alkenes which were unable
to afford 2- or 3-substitued and 2,3-disubstituted
indoles. To prepare 2,3-disubstituted indoles, Muñiz
et al. continued to develop an iodine(III) reagent-
mediated intramolecular sequential electrophilic N−H
and C−H bonds functionalization between the aniline
and acetylene (Scheme 1-B).[16] The free 2,3-
disubstituted indoles can be obtained in good yileds
by the tracelesss tether removal under Ti(OiPr)4
combined with Mg and TMSCl. Although this
methodoly resolved the preparation of 2,3-
disubstituted indoles, it still suffered from multistep
preparation of starting matials and deprotecting
procedures. Based on the studies of electronic effects
on iodine(III) compounds by Muñiz’s group[17] and
Indole scaffolds are common in numerous
biologically active natural products and synthetic
compounds, including alkaloids, peptides and
materials in sciences.[1] Therefore, the development
of new methods to access privileged indole scaffolds
has received much attention in synthetic chemistry.[2]
Transition-metal catalysis has been applied in various
elegant syntheses of indoles, using palladium,[3]
rhodium,[4] and other catalysts[5]. Although the
transition-metal-catalyzed strategies have shown high
efficiency, metal-free strategies for indole preparation
are also desirable due to their advantages with regard
to purity requirements in biological and medicinal
research.[6] Many metal-free indole synthesis methods
have been developed,[7] but the most promising is the
intramolecular amination of 2-alkenylanilines owing
to the availablility of the starting materials, including
C(sp2)-H bond amination by sulfenium ions,[8] DDQ-
mediated amination,[9] selenium-catalzyed oxidative
amination using N-fluorobenzensulfonimide as
oxidant,[10] and NIS-mediated intramolecular
amination.[11] Hypervalent iodine(III) reagents are
versatile tools for the construction of carbon-
our research into hypervalent iodine compounds[18]
,
we became interested in accessing such substituted
indoles by using readily available iodine(III) reagents
and simple operations. We surmised that the
electronic and steric effects of iodobenzene in the
iodine(III) reagents would directly affect their
reactivity and the efficiency of amination of 2-
vinylaniline, particularly, for polysubstitituted
1
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
alkenes (Scheme 1-C). Herein, we report the
synthesis of 2,3-disubstituted indoles via the 3,5-
dimethyliodobenzene acetate-promoted intramolecuar
amination of 2-alkenylanilines.
these results showed that iodine(III) reagents
containing electron-danating group at para-, meta-, or
ortho-positions gave better yields than their elecron-
withdrawing groups counterparts, which were
consistent with Muñiz’s recent studies.[17] Pleasingly,
2l and 2m gave desired product 3a in 85% and 84%
yields, respectively (Table 1, entries 24 and 25).
Notably, the reaction time of this transformation was
less than 20 min. Therefore, optimal conditions for
the preparation of indole 3a were 2.0 equiv. of 2l in
MeCN at 100 °C for 15 min.
A) Muñiz's work, amination of 2-vinylanilines though modified anion of Koser reagent
SO3H
PhIO (1.1 equiv)
i-Pr
ArSO3H (1.1 equiv)
CHCl3, rt
R'
R'
N
NH
i-Pr
CO2R
CO2R
O3SAr
i-Pr
24 examples
32-92% yields
via
NHCO2R
B) Muñiz's work, iodine(III)-mediated N-H / C-H bonds functionalization between aniline and alkyne
AcO
I
OAc
MeO
AcO
I
OAc
AcO I OAc
Ar
AcO
I OAc
AcO
I
OAc
Ar
Ar
H
PhI(OAc)2
HFIP, rt
Ti(OiPr)4
O
S
N
N
O2N
R
N
H
Mg, TMSCl
MeO
H
S
O
R
O
R
O
OMe
CF3
4 examples
66-92% yields
18 eamples
35-87% yields
2d
2e
2f
2g
2h
C) This work, amination of 2-alkenylaniline through available iodine(III) and simple operations
R1
AcO
Me
I OAc
AcO
OAc
I
OAc
AcO
I
OAc
AcO
I
OAc
AcO
I
R1
OAc
R2
R3
Me
F3C
R2
ArI(OAc)2
R2
or
R
R
R
R3
NH
MeO
OMe F3C
CF3 Me
Me
N
N
MeCN, 100 °C
15-20 min
R4
R3 = H
R4
R1 = H, R2, R3  H
Me
2m
R4
2i
2j
2k
2l
Scheme 1. Amination of 2-alkenylanilines to access
indoles using iodine(III) reagents.
Figure 1. Iodine(III) reagents tested.
Table 1. Optimization of the reaction conditions.a
Initially, Koser reagent PhI(OH)OTs (2a) was used
to investigate the intramolecular amination of 1a to
synthesize 3-methyl indole. However, this reaction
resulted in a complex mixture with only 9% and 12%
yields of 3a obtained in DCM at rt and 80 °C,
respectively (Table 1, entries 1 and 2). Pleasingly,
product 3a was afforded in 28% and 40% yields
using PhI(OOCF3)2 (2b) and PhI(OAc)2 (2c),
respectively, at 80 °C for 15 min (Table 1, entries 3
and 4). Solvent screening showed that MeCN gave
the best result, with a 67% yield (Table 1, entries
5−9). Decreasing the amount of PhI(OAc)2 to 2.0
equiv. afforded 3a in 68% yield, which decreased to
to 60% when using only 1.0 equiv. of PhI(OAC)2
(Table 1, entries 10 and 11). The effect of
temperature was also investigated (Table 1, entries
12−15). Product 3a was obtained in 73% yield from
the reaction at 100 °C. Finally, the substituent effect
of the aryl group in iodine(III) reagent 2 (Figure 1) on
the yield of 3a was examined. Electron-donating or
electron-withdrawing para-substituents had litte
effect on the yield (Table 1, entries 16 and 17).
Iodine(III) reagent 2f, containing an electron-
donating group at the aryl meta-position, resulted in a
higher yield than iodine(III) reagent 2g, with an
electron-withdrawing group at the same position
(Table 1, entries 18 and 19). Lower yields of 3a were
afforded when using iodine(III) reagents 2h and 2i,
containing methoxy and trifluoromethyl groups,
respectively (Table 1, entries 20 and 21).
Interestingly, 3,5-dimethoxy-substituted iodine(III)
reagent 2j delivered product 3a in 79% yield, while
2k, containing trifluoromethyl groups, afforded 3a in
only 17% yield with recovery of substrate 1a (Table 1,
entries 22 and 23). Compared with reagents 2d-2k,
Me
Me
ArIX2 (2)
conditions, 15-20 min
NHTs
N
Ts
1a
3a
entry
1
2
3
4
5
6
7
8
solvent
DCM
DCM
DCM
DCM
T (°C)
rt
80
80
80
80
80
80
80
80
80
80
60
3a, yield (%)b
9
2
2a
2a
2b
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2d
2e
2f
12
28
40
32
49
56
36
67
68c
60d
68
59
73
69
62
59
68
27
51
29
79
17
87
84
toluene
THF
DMSO
EtOAc
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
rt
100
120
100
100
100
100
100
100
100
100
100
100
2g
2h
2i
2j
2k
2l
25
2m
a)
Reaction conditions: 1a (0.2 mmol), 2 (entries 1−9, 3.0
equiv.; entries 12−25, 2.0 equiv.), solvent (2.5 mL), 15−20
min; b) isolated yield; c) 2c (2.0 equiv.); d) 2c (1.0 equiv.).
2
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
R3
R3
With optimized conditions in hand, we set out to
3
6
R4
2
4
5
explore the generality of this amination method for
indole formation. The scope of aryl substituents on
various 2-alkenylaniline substrates was examined
(Table 2). A variety of 2-alkenylanilines bearing
substituents at 3, 4, 5 or 6-positions on the aryl ring
were well tolerated affording 3-methyl substituted
indoles in good to high yields (3a-j). When the N-
protecting group was replaced with an acetyl group,
desired product 3k was afforded in 67% yield.
However, using benzyl protecting group afforded
indole 3l in only 30% yield. This result suggested that
the N-protecting groups greatly influenced indole
formation. Next, different alkenyl moieties in
alkenylaniline 1 were also evaluated for the synthesis
of diversely substituted indoles. Various 3-aryl
substituted indoles were afforded in moderate to good
yields (3n-r). The methoxy substituent resulted in a
lower yield than fluoro and chloro substituents (3n-p).
Furthermore, when a 2,4,6-trimethyl group was
present on the aryl ring, desired product 3q was
obtained in 50% yield. Pleasingly, a thienyl
subsituent afforded 3r in 50% yield with the reaction
necessarily ran at room temperature. Diverse 2,3-
disubstituted indoles bearing aryl or alkyl with linear
or cyclic groups were afforded in good yields (3s-z).
For indole products 3x-z, using the classic Fisher
indole synthesis method gave higher yields. However,
classic Fisher indole synthesis procedures were not
compatible with ketones containing sensitive
functional groups owing to their reactions with
phenyl hydrazine. Compared to our method, the
sensitive functional groups such as ester, and vinyl
groups were compatible, affording the desired
products in moderate yields (3v-w). These
compounds could be applied in further useful
transformations in organic synthesis.
3, 5-Me2C6H3I(OAc)2 (2l)
R4
R1
R1
1
N
R2
MeCN, 100 °C
15-20 min
NH
R2
1
3
R1 = H, 3a (87%)
Me
Me
R1
R1 = Me,
R1 = F,
(71%)
(79%)
3b
3c
R1 = F, 3f (76%)
R1 = Cl,
R1 = I,
(65%)
3g
N
R1
R1 = Cl, 3d (68%)
R1 = Br, 3e (63%)
Me
(66%)
N
3h
Ts
Ts
Cl
Me
Me
Me
N
N
N
N
Ts
Ts
Bn
3l
(30%)
Ac
Cl
3i
3j
3k
(67%)
Ph
(58%)
(67%)
Cl
S
X
X = 4-OMe, 3n (51%)
X = 4-F,
X = 4-Cl,
X = 2,4,6-Me3, 3q (50%)
3o (71%)
3p (75%)
N
N
N
Ts
Ts
3r (50%)c
Ts
3m
(82%)
Ph
Ph
Me
Ph
OAc
Ph
Me
Me
N
N
Ts
N
N
Ts
Ts
Ts
3s (64%)
3t (55%)
3u (58%)
3v (52%)
Ph
Ph
N
N
Ts
3w (37%)
N
N
Ts
Ts
Ts
3x (30%, 50%d) 3y (63%, 71%d) 3z (50%, 63%d)
a) Reaction conditions: 1 (0.2 mmol), 2l (2.0 equiv), MeCN
b)
c)
(2.0 mL), 15−20 min;
isolated yields; run at room
temperature; isolated yields by Fisher indole synthesis
from ketones and phenyl hydrazine in
HOAc at 120 °C.
d)
To probe the reaction mechanism, controlled
experiments were performed. The addition of
TEMPO (2.0 equiv.) under optimal conditions still
afforded desired product 3a in 91% yield (Scheme 2-
1), indicating that the reaction did not involve a
radical process. When substrate 1x was reacted with
iodine reagent 2l at 100 °C for 15 min, products 3x
and 4x were afforded in 30% and 26% yields,
respectively (Scheme 2-2). The structure of 4x was
determined from 2D NMR spectra. Further
experiments showed that compound 4x was
converted to compound 3x in 40% yield under the
optimal conditions while compound 3x cannot
convert to compound 4x (Scheme 2-3). These results
suggested that compound 4x was a key intermediate
in the formation of indole 3x. Elimination of cis OAc
and proton group revealed that the formation of
indoles at last step was E1 elimination. When
compound 5, the precursor to 1a, was treated under
the optimal conditions, compound 6 and TsNH2 were
obtained in 52% and 55% yields, respectively
(Scheme 2-4). Treatment of compound 5 with
iodine(III) reagent 2l in MeOH at 0 °C for 5 min gave
compound 7 in 79% yield (Scheme 2-5). When
aniline 8 containing an additional methyl protecting
group was subjected to the optimal conditions even
for 24 h, the reaction did not occur and aniline 8 was
Table 2. Scope of 2-alkenylanilines 1.a,b
3
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
Me
OAc
Me
recovered in 90% yield (Scheme 2-6). Interestingly,
aniline 1l in Table 2 not only gave indole 3l in 28%
yield under the optimal conditions but also afforded
aniline 9 and benzaldehyde in 21% and 55% yields,
Me
Me
2
(2.0 equiv)
Me
+
MeCN, 100 °C
15 min
Me
N
Ts
3u
N
NHTs
Ts
11
10
respectively (Scheme 2-7). Compound
9
and
2l
19%
55%
0%
0%
benzaldehyde might be generated from the oxidation
of N-atom to imine group by iodine(III) reagent 2l
and a sequence of hydrolysis. These results suggested
that the iodine(III) reagent initially oxidized the N-
atom rather than the alkene during the indole
formation.
2m
Scheme 3. Testing the trisubstituted alkene 10.
Based on the experimental results, a plausible
mechanism for the formation of indole 3 was
proposed (Scheme 4). Iodine(III) reagent 2 combines
with alkenylaniline 1 to form intermediate A
Me
Me
TEMPO (2.0 equiv)
2l
(2.0 equiv)
eliminating acetic acid. Intermediate
A
then
1)
2)
N
MeCN, 100 °C
15 min
NHTs
undergoes reductive elimination to generate
nitrenium ion B,[16,19] as supported by the results in
Schemes 2-4 and 2-5. Isomerization of B forms
intermediate C and D. Intermediate D then undergoes
intramolecular nucleophilic attack by the N-atom to
give intermediate E. Trapping of intermediate E by
an OAc anion results in 3-oxygenated indolines 4 or 9.
When R2 or R3 are protons, compound 4 undegoes E1
elimination to give indole product 3.
Ts
3a (91%)
1a
AcO
2l (2.0 equiv)
+
MeCN, 100 °C
15 min
H
N
Ts
N
Ts
NHTs
1x
3x
4x
(26%)
(30%)
40%
AcO
2l
MeCN, 100 °C
3)
4)
15 min
N
H
N
Ts
Ts
HO
4x
3x
0%
R1
R1
R1
R1
HO
Me
Me
R2
R3
R2
R3
R2
R3
O
R2
ArI(OAc)2
2l (2.0 equiv)
Me
TsNH2
55%
+
Me
R3
MeCN, 100 °C
15 min
N
NTs
NHTs
NTs
I
A
NHTs
HOAc
C
O
Ts
B
ArI +
5
OAc
1
6, 52%
OAc
Ar
HO
HO
Me
Me
Me
R1
MeO
R1
R1
AcO
(2.0 equiv)
R1
R2
2l
R2
R3
R3 = H
5)
6)
7)
MeO
Me
OAc
R2
R3
R2
MeOH, 0 °C
5 min
N
R3
NHTs
N
Ts
N
N
N
5
HOAc
Ts
Ts
7, 79% Ts
Ts
D
Me
4
E
3
2l
(2.0 equiv)
no reaction
Me
Scheme 4. Proposed mechanism.
MeCN, 100 °C
15 min - 24 h
NTs
Me
8
Me
Me
These useful indole scaffolds encouraged us to
perfom this method on a gram scale. When akene 1a
(1.6 g) was reacted with 2l, indole 3a (1.3 g) was
obtained in 78% yield accompanied by 3,5-
dimethylphenyl iodine (1.56 g) (Scheme 5-1). To
avoid the large amount of aryliodine produced in this
reaction, we attempted using a catalytic amount of
2l
(2.0 equiv)
PhCHO
55%
+
+
MeCN, 100 °C
15 min
N
NH2
NH
Bn
Bn
3l (30%)
9 (21%)
1l
Scheme 2. Mechanistic studies.
aryliodine
in
the
presence
of
meta-
According to the results shown in Scheme 2-2, a
trisubstituted alkene might inhibit acetoxy
elimination to afford a 3-oxygenated indoline or
rearrangement product. As shown in Scheme 3, when
aniline 10 was subjected to the optimal conditions,
desired product 11 was obtained in 19% yield along
with strarting material recovery, but rearrangement
product 3u was not observed. These results indicated
that no carbocation should form at the 3-position of
the indoline intermediate. To our delight, a 55% yield
of product 11 was afforded when 2,4,6-trimethyl
substituted iodine(III) reagent 2m with was used.
chloroperoxybenzoic acid (mCPBA) as terminal
oxidant (Scheme 5-2). When 0.2 equiv. of 3,5-
dimethylphenyl iodine was combined with BF3•Et2O
(2.0 equiv.) in the presence of 3.0 equiv. of mCPBA
and HOAc in MeCN at 80 °C for 30 min, product 3a
was isolated in 75% yield.
4
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
1) Gram scale preparation of indole 3a
Scheme 6. Synthesis of indolo[3,2-a]carbazole alkaloid.
Me
Me
I
2l (2.0 equiv)
+
In summary, we have developed a facile method
for the synthesis of 3-substituted and 2,3-
disubstituted indoles via the intramolecular amination
of 2-alkenylanilines with readily available
hypervalent iodine reagents. These reaction requires a
short reaction time to provide a wide range of indoles
in good yields. Mechanistic studies suggested that
acetoxy-substituted indoline was the key intermediate
in indole formation. Furthermore, the indole were
easily prepared at the gram-scale and by catalysis
with 3,5-dimethylphenyl iodine in the presence of
mCPBA. Finally, indolo[3,2-a]carbazole was
synthesized in good yield in six steps from
commercial ortho-iodoaniline.
MeCN, 100 °C
NHTs
N
Me
3a
, 1.3 g,78% yield 1.56 g
Me
20 min
Ts
1a
, 1.6 g, 6.0 mmol
2) Catalytic 3,5-dimethylphenyl iodine
I
(20 mol%)
Me
Me
Me
Me
BF3·Et2O (2.0 equiv)
mCPBA (3.0 equiv)
HOAc (10.0 equiv)
MeCN, 80 °C, 30 min
75% yield
NHTs
N
Ts
1a
3a
Scheme 5. Gram scale preparation and use of catalytic 3,5-
dimethylphenyl iodine.
Experimental Section
As this method proved to be efficient for various
substrates, we envisioned its application to the
synthesis of indolocarbazole alkaloids. This family of
compounds are found in many natural products,
pharmaceuticals, photorefractive materials, and
organic dyes, and have attracted much attention in
synthetic and biological fields.[20] We postulated that
indolo[3,2-a]carbazole[21] could be accessed from
simple commercial ortho-iodoaniline. As shown in
Scheme 6, 2-alkenylaniline 12 was prepared in 75%
yield through the palladium-catalyzed cross-coupling
of N-Ts-o-iodoaniline with alkenylboronic acid.
When alkenylaniline 12 was subjected to the optimal
conditions, desired indole 13 was afforded in 78%
yield in 15 min. Compound 14 was obtained in 90%
yield by the subsequent hydrolysis using concentrated
HCl solution, and then underwent Fisher-indole
synthesis by reacting with PhNHNH2 in HOAc to
give compound 15 in 65% yield. Removal of the Ts
group with NaOH afforded indolo[3,2-a]carbazole 16
in 79% yield. This approach provides an alternative
method to accessing indolocarbazole scaffolds.
General procedure for the synthesis of indole 3a: In a
Teflon-sealed reaction flask was charged with 2-
alkenylaniline 1a (0.2 mmol) and 3,5-Me2C6H3I(OAc)2 2l
(0.4 mmol, 2.0 equiv.) under air. MeCN (2.5 mL) was
added. And then, the reaction vessel was sealed with a
Teflon cap. The reaction mixture was stirred vigorously at
100 °C for 15−20 min until the substrate 1a disappeared
(monitored by TLC). At this time, the solvent was removed
under reduced pressure and the crude product was purified
by flash chromatography (dry loading with SiO2) using
eluents (1:30 ethyl acetate:petroleum ether to 1:10) to
provide product 3a as a white solid (0.049 g, 87%). mp:
1
95−96 °C; H NMR (500 MHz, CDCl3): δ 7.98 (d, J = 8.0
Hz, 1H), 7.74 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 7.5 Hz, 1H),
7.32−7.29 (m, 2H), 7.24−7.21 (m, 1H), 7.19 (d, J = 7.5 Hz,
2H), 2.32 (s, 3H), 2.23 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 144.6, 135.4, 135.2, 131.7, 129.7, 126.7, 124.5,
123.0, 122.9, 119.3, 118.5, 113.6, 21.4, 9.6; IR (thin film)
3456, 3014, 2954, 1612, 1458, 1210, 1009, 733 cm−1;
HRMS (ESI) m/z C16H16NO2S (M+H)+ 286.0896, found
286.0899.
Acknowledgements
This work was supported by the “Overseas 100 Talents Program”
of Guangxi Higher Education, Basic Research Program of
Guangxi Normal University (2014ZD005) and National Natural
Science Foundation of China (21562005, 21602037, 21462008),
Natural Science Foundation of Guangxi (2016GXNSFFA380005),
State Key Laboratory for Chemistry and Molecular Engineering
of Medicinal Resources, Ministry of Science and Technology of
China (CMEMR2015-A05). We also thank Dr. Simon Partridge,
from Liwen Bianji, Edanz Editing China (www.liwenbianji.cn/ac),
for the manuscript proofreading.
O
O
O
(HO)2B
I
I
TsCl
97%
O
Pd(PPh3)2Cl2
75%
NH2
NHTs
NHTs
12
2l
, MeCN
78%
120 °C, 15 min
References
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O
HCl, DCM
O
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
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7
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10.1002/adsc.201701551
Advanced Synthesis & Catalysis
COMMUNICATION
Iodine(III) Reagent-Mediated Intramolecular
Amination of 2-Alkenylanilines to Prepare Indoles
R3
R3
R4
ArI(OAc)2
NH
R4
R1
R1
N
R2
26 examples
MeCN, 100 °C, 15 - 30 min
NH
R2
N
Adv. Synth. Catal. Year, Volume, Page – Page
H
R3
OAc
Indolo[3,2-a]carbazole
30% yield in six steps
28 - 87% yields
R4
R1
N
Chun-Yang Zhao, Kun Li, Yu Pang, Jia-Qing Li,
Cui Liang, Gui-Fa Su*, and Dong-Liang Mo*
R2
via
8
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