Photoinduced Cross-Coupling of Amines with 1,2-Diiodobenzene and Its Application in the Synthesis of Carbazoles

Article abstract of DOI:10.1055/s-0037-1609444

A facile and efficient process for the preparation of various tertiary aminobenzenes and carbazole derivatives via photoinduced cross-coupling of amines with 1,2-diiodobenzene is reported. Mechanistic investigations indicate that the transformation proceeds via nucleo-philic addition of an amine to the benzyne intermediate accompanied with a proton transfer process, followed by an oxidative cyclization of the generated diphenylamine to furnish the corresponding carbazole products.

Full text of DOI:10.1055/s-0037-1609444

SYNTHESIS
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
© Georg Thieme Verlag Stuttgart · New York
2018, 50, A–I
special topic
A
en
X. Zhao et al.
Special Topic
Synthesis
Photoinduced Cross-Coupling of Amines with 1,2-Diiodobenzene
and Its Application in the Synthesis of Carbazoles
Xinxin Zhaoa
R1
N
R2
R1, R2 = aliphatic group
Ming Chena
Binbin Huanga
Chao Yanga
Yuan Gaob
8 examples
35–73% yield
X
Y
R1
R2
hn
N
H
+
R
N
Wujiong Xia*a
0
0
0
0
0-
0
0
1
9-
3
9
6
9-
5
2
0
R1 or R2 = aromatic group
Ar
X, Y = halogen
22 examples
24–71% yield
a State Key Lab of Urban Water Resource and Environment,
School of Science, Harbin Institute of Technology,
Shenzhen 518005, P. R. of China
xiawj@hit.edu.cn
b School of Chemistry and Chemical Engineering, Yantai
University, 30 Qingquan Rd, Laishan District, Yantai
264005, P. R. of China
Published as part of the Special Topic Modern Radical
Methods and their Strategic Applications in Synthesis
Received: 09.02.2018
Accepted after revision: 13.03.2018
Published online: 08.05.2018
Carbazoles, as one of the particularly important classes
of nitrogen-containing functional compounds, are a signifi-
cant area of research due to their presence in the frame-
works of a wide spectrum of natural products and biolo-
gically active molecules (Figure 1).6 Moreover, many carba-
zoles have been proven to be key motifs in the synthesis of
electrical and thermal materials.7 Consequently, tremen-
dous efforts have been devoted toward the development of
strategies for the construction of carbazole frameworks. All
these tactics can generally be classified into two categories:
(i) construction of the central pyrrolyl ring via intramolecu-
lar C–C or C–N coupling,8 and (ii) installation of a new aro-
matic ring onto an indole derivative via inter- or intra-
molecular benzannulation.9 However, most of these proce-
dures require complex and expensive metal catalysts (such
as Pd and Ru), harsh reaction conditions, or complicated
steps. Therefore, developing an inexpensive and practical
method to access carbazoles is still in high demand.
Over the past decades, direct addition of amines to the
triple bond of a benzyne intermediate has been extensively
studied to access various nitrogen-containing products
(Scheme 1);8a,10,11 however, formation of the benzyne inter-
mediate often requires a strong base (e.g., organolithium re-
agents), thereby limiting wider application of the process.
Based on previous literature,12 the benzyne intermediate
could be easily obtained from a dihalobenzene precursor
under photoirradiation. Hence, we envisioned that an inter-
molecular cross-coupling might take place via a nucleo-
philic addition process between aminobenzenes and halo-
benzenes to furnish nitrogen-containing compounds under
the irradiation of ultraviolet light. In this report, we
DOI: 10.1055/s-0037-1609444; Art ID: ss-2018-c0084-st
Abstract A facile and efficient process for the preparation of various
tertiary aminobenzenes and carbazole derivatives via photoinduced
cross-coupling of amines with 1,2-diiodobenzene is reported. Mechanis-
tic investigations indicate that the transformation proceeds via nucleo-
philic addition of an amine to the benzyne intermediate accompanied
with a proton transfer process, followed by an oxidative cyclization of
the generated diphenylamine to furnish the corresponding carbazole
products.
Key words aminobenzenes, cross-coupling, carbazoles, oxidative
cyclization
Aminobenzenes represent one of the most common
subunits present in various organic compounds across
pharmaceutical and materials sciences;1 numerous meth-
odologies have therefore been developed for their prepara-
tion. Among all the synthetic protocols, amination of ben-
zene halides provides the most attractive method to gener-
ate C(sp2)–N bonds. For example, the transition-metal-
catalyzed (usually a Pd-based catalyst) C(sp2)–N cross-cou-
pling reactions,2 e.g., the Buchwald–Hartwig and Ullmann–
Goldberg reactions,3 have been extensively studied over the
past decades. Furthermore, Fu and co-workers have dedi-
cated many years to the study of different types of copper-
catalyzed photoinduced C–N coupling reactions.4 In 2016,
Johannes developed a visible-light catalytic cross-coupling
of primary aryl amines with aryl halides.5 However, tech-
niques that do not employ metal catalysts to directly
achieve the arylation of amines under mild conditions are
still rare and attractive.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

B
X. Zhao et al.
Special Topic
Synthesis
product 2a being isolated in 27% yield (entry 1). In order to
gauge the reactivity of 1a, other dihalobenzenes such as II
and III were employed, with the desired product 2a being
obtained (entries 2 and 3). The reaction with 1,2-diiodo-
benzene (IV) showed a much better result than with the
other dihalobenzenes (entry 4). When the reaction was car-
ried out without protection of the nitrogen, a dramatic de-
crease in the yield was observed, probably due to the strong
radical-scavenging activity of air (entry 5). Subsequent sol-
vent screening revealed that the reaction conducted in hep-
tane afforded 2a in a higher yield than in other media (en-
tries 6–14). Notably, polar solvents such as methanol and
acetonitrile showed a negative effect on the photoreaction.
Moreover, changing the glass vessel to a quartz tube led to
an appreciable decrease in the yield, which indicated that
H
N
O
Cl
Cl
O
O
N
N
H
N
N
OH
O
O
H
R1
R2
OH
N
OH
H
MeO
HO
NHMe
Tjipanazole A1: R1 = Me, R2 = H
Tjipanazole A2: R1 = H, R2 = Me
antifungal agent
Staurosporine
protein kinase inhibitor
Clausamine A
antitumor agent
Br
N
N
N
O
H
HO
N
H
N
H
Br
Ellipticine
Glycomaurin
P7C3
Table 1 Optimization of the Reaction Conditionsa
Figure 1 Representative carbazole-based natural products and
bioactive carbazole derivatives
N
X
H
N
hν
Previous reports
+
Y
solvent
a) intramolecular cycloaddition
1a
2a
N
I
I
I
I
I
X
Y
organolithium/
strong base
NH2
:
X
NH2
Cl
F
Br
NH
I
II
III
IV
N
X = halogen
Yield (%)b
b) intermolecular coupling reaction
Entry
N
hν
Solvent
R
1
2
I
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
300 nm
350 nm
HPML
heptane
heptane
heptane
heptane
heptane
1,2-DCE
hexane
THF
27
35
42
72
18
45
67
40
42
39
22
25
28
34
48
40
46
42
organolithium/
strong base
R'
X
N
R
R'
R
R'
II
R''
N
+
N
+
R''
3
III
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
R''
X = halogen
4
R1
N
5c
6
This work
X
R2
R1
R2
R1
R2
7
R1, R2 = aliphatic group
hν
N
H
+
+
N
H
8
Y
R
N
9
1,4-dioxane
toluene
MeCN
X, Y = halogen
Ar
10
11
12
13c
14
15d
16e
17
18
R
1 or R2 = aromatic group
MeOH
Scheme 1 Previous reports and the design of this cross-coupling
DMSO
reaction
DMF
heptane
heptane
heptane
heptane
describe our findings on this facile photochemical method
to access diverse tertiary aminobenzenes and carbazoles
from simple starting materials.
The proposed cross-coupling was initially explored by
using N-benzylpropan-2-amine (1a) as a nucleophile and 1-
fluoro-2-iodobenzene (I) as the benzyne precursor (Table
1). Exposure of a degassed heptane solution of both 1a and I
in a glass container to irradiation using a low-pressure mer-
cury lamp (λ = 300 nm) led to the desired cross-coupling
MPML
a Reaction conditions: 1a (0.2 mmol), N (0.1 mmol), solvent (10 mL), glass
tube, N2 atmosphere (unless otherwise noted), 6–8 h.
b Yield of isolated product.
c Reaction conducted under an air atmosphere.
d Reaction conducted in a quartz tube.
e Reaction time: 24 h.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

C
X. Zhao et al.
Special Topic
Synthesis
the favorable wavelength for reaction was no less than
300 nm (entry 15). However, a longer reaction time was re-
quired to completely consume 1a when the light-emitting
spectrum was chosen at 350 nm (entry 16). Other light
sources, for example, a high-pressure mercury lamp (HPML)
and a medium-pressure mercury lamp (MPML), did not im-
prove the yield of 2a (entries 17 and 18).
the oxidative cyclization of the in situ formed diphenyl-
amine intermediates.13 With this assumption in mind, a se-
ries of carbazoles was synthesized to demonstrate the ap-
plication of this reaction model. As shown in Scheme 3, it
was notable that the desired N-methylcarbazole (4a) could
be readily prepared from substrate 3a in a yield of up to
71%. Replacing the methyl group with other substituents,
such as ethyl, allyl, 2-propyl and benzyl, delivered the cor-
responding products 4b–e smoothly in yields of 24–52%.
Furthermore, we were satisfied to find that four- to seven-
membered aliphatic rings, as well as a six-membered oxo-
heterocyclic ring were tolerated in this transformation, giv-
ing the corresponding carbazole derivatives 4f–j in moder-
ate yields. As for the photoreaction of non-substituted phe-
nylamine (3k), the carbazole product 4k was isolated in 25%
yield, indicating that this photoreaction was applicable to
primary phenylamines, albeit in a weak manner.
With optimized conditions in hand, the substrate scope
with respect to the amine partner was screened. As re-
vealed in Scheme 2, diverse types of tertiary aminoben-
zenes were readily prepared in moderate to high yields by
employing aliphatic amines with 1,2-diiodobenzene (IV). In
addition to 2a, N-phenylated products 2b and 2c could be
successfully prepared from their corresponding secondary
amines in 73% and 35% yields, respectively. Cyclic amines
also readily tolerated the reaction conditions and provided
the corresponding aminobenzenes 2d–f in good yields. It is
noteworthy that aliphatic amine 1g, containing two nitro-
gen atoms, underwent the cross-coupling reaction with IV
on both nitrogen atoms to afford product 2g in moderate
yield, even when the loading of 1g was reduced to 1 equiva-
lent. Next, the reaction between benzocyclic amine 1h and
IV was tested, and delightfully, the reaction proceeded suc-
cessfully under the optimized conditions to deliver 2h in
50% yield.
Next, diverse structural variations of R1 and R2 were
evaluated. For example, compound 3l bearing a strong
electron-withdrawing cyano group at the para position
afforded the desired product 4l in a low yield of 23%. Simi-
larly, p-halo- and p-trifluoromethyl-substituted substrates
were also tolerated under the photoreaction conditions,
providing the corresponding products 4m, 4n and 4o in
52%, 50% and 34% yields, respectively. In addition, sub-
strates 3p and 3q furnished products 4p and 4q in yields of
30% and 28%, respectively. Remarkably, the substrate scope
could be extended to tetrahydroquinoline (3r), which was
successfully transformed into product 4r in a moderate 53%
yield. Furthermore, substrate 3s bearing a meta-chlorine
atom gave a mixture of two regioisomers 4s and 4s′ in a
ratio of 1:1, while the meta-methyl-substituted reactant 3t
provided 4t and 4t′ in a ratio of 3:5 and an overall yield of
52%.13d,e,14 According to the literature,13d,e o- substituted
compounds could also afford two products. As expected,
the o-methyl-substituted substrate 3u delivered two carba-
zole derivatives: 1,9-dimethyl-9H-carbazole (4u) and prod-
uct 4a, which may be generated via elimination of the
methyl group. As for substrate 3v with a bulkier o-tert-
butyl group, 4a was obtained as the exclusive product,
probably due to the strong steric effect.
In order to gain more insight into this photochemical re-
action, control experiments were carried out by using 3a as
a model substrate with 1,2-diiodobenzene (IV). To our de-
light, after a reduced irradiation time of 2 hours, a small
amount of N-methyl-N-phenylaminobenzene (3A) was iso-
lated (Scheme 4, eq 1). A deeper investigation identified 3A
as an important intermediate which could be finally con-
verted into the carbazole 4a when exposed to the standard
reaction conditions (Scheme 2, eq 2).
Scheme 2 Photoinduced cross-coupling between 1,2-diiodobenzene
and different aliphatic amines. Unless otherwise noted, all reactions
were conducted under the optimized conditions: 1 (0.2 mmol), IV
(0.1 mmol), heptane (10 mL), glass tube, N2 atmosphere, λ = 300 nm,
6–10 h; reactions were monitored by TLC. Yields are those of isolated
products. a The amount of 1g was decreased to 1.0 equivalent.
Based on the control experiments and the relevant liter-
ature,8a,10,11 a tentative reaction mechanism is proposed in
Scheme 5. Upon absorbing the energy of UV light, 1,2-
diiodobenzene (IV) is excited to form the benzyne interme-
Subsequently, we turned our attention to the photo-
chemical behavior of N-substituted secondary phenyl-
amines. In general, such a photoreaction protocol led to the
formation of carbazole derivatives, which may stem from
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

D
X. Zhao et al.
Special Topic
Synthesis
R1
N
R1
I
I
NH
300 nm
heptane
R2
+
R2
IV
3
4
N
N
N
N
N
4b 52%
4c 24%
4d 48%
4e 42%
4a 71%
O
N
N
N
N
N
4f 57%
4g 60%
4h 41%
4i 40%
4j 50%
N
N
N
N
H
N
F3C
NC
F
Cl
4l 23%
4m 52%
4n 50%
4o 34%
4k 25%
N
N
N
N
N
Cl
O
+
O
O
Cl
4s/4s' = 1:1, 48%a
4p 30%
4q 28%
4r 53%
N
N
N
N
N
NH
+
+
4a/4u = 6:1, 40%a
4a 37%
4t/4t' = 3:5, 52%a
3v
Scheme 3 Photoinduced preparation of carbazole derivatives. Unless otherwise noted, all reactions were conducted under the optimized conditions:
3 (0.2 mmol), IV (0.1 mmol) in heptane (10 mL), glass tube, N2 atmosphere, λ = 300 nm, 8–12 h; reactions were monitored by TLC. Yields are those of
isolated products. a The ratio of the generated mixture was determined by NMR spectroscopy.
2 (Scheme 5, path a). As for aminobenzene 3, formation of
N
I
I
N
NH
the tertiary aminobenzene IM3 is followed by an oxidative
cyclization process, with the generated iodine as an oxi-
dant, to give the final carbazole derivative 4 (Scheme 5,
path b).
300 nm
heptane
(1)
(2)
+
+
3A
4a
3a
IV
In summary, we have developed a novel cross-coupling
reaction to achieve the arylation of secondary aliphatic
amines as well as secondary aminobenzenes. This synthetic
protocol provides an efficient method to access tertiary am-
inobenzenes and carbazoles. Moreover, the reaction is trig-
gered by UV light and the developed conditions are mild
and tolerate readily accessible starting materials. Mechanis-
tic investigations disclosed that the generated benzyne in-
termediate was trapped by the secondary amine nucleop-
hiles to give the tertiary adducts, while the final carbazole
products were produced by oxidative cyclization of diphe-
nylamines, which were generated from the secondary ami-
nobenzenes in a one-pot reaction.
N
I
I
N
300 nm
heptane
+
3A
IV
4a
Scheme 4 Control experiments
diate IM1 by eliminating two iodine radicals, which proba-
bly couple with each other to afford an iodine molecule. On
the other hand, as a good nucleophile, the nitrogen lone
pair electrons of amine 1 interact with the triple bond of
IM1 to deliver IM2. An intramolecular proton transfer in
IM2 then takes place to give tertiary aminobenzene product
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

E
X. Zhao et al.
Special Topic
Synthesis
I
R1
N
– 2I
I
R2
hν
IV
2
R'
N
1
R1
NH
R2
proton transfer
R2
R
path b
4
N H
R1
I2
IM1
path a
IM2
nucleophilic
addition
H
N
R
R'
R'
N
R
3
IM3
Scheme 5 Proposed mechanism
13C NMR (101 MHz, CDCl3): δ = 147.92, 129.37, 115.50, 112.01, 44.44,
12.68.
HRMS (ESI): m/z [M + H]+ calcd for C10H16N: 150.1277; found:
150.1272.
All solvents were purified according to the reported procedures.15
Thin-layer chromatography (TLC) was performed with Merck GF254
silica gel precoated TLC plates. Flash column chromatography was
performed using Merck silica gel (200–300 mesh), eluting with petro-
leum ether/EtOAc. Melting points were determined using a Mettler–
Toledo capillary melting point apparatus and are uncorrected. 1H
NMR (400 MHz) and 13C NMR (151 MHz) spectra were recorded on a
Bruker AV-400 instrument, with CDCl3 as the solvent and TMS as the
internal standard. 1H NMR chemical shifts are reported in parts per
million relative to the chemical shift of CDCl3 at 7.26 ppm, followed by
multiplicity (standard abbreviations) and integration. 13C NMR spec-
tra are reported relative to the central signal of the CDCl3 triplet at
77.16 ppm. HRMS (ESI) spectra were recorded on a Bruker Esquire LC
mass spectrometer using electrospray ionization.
N,N-Diisopropylaniline (2c)
Yield: 6.2 mg (35%); yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.22 (dd, J = 8.4, 7.4 Hz, 2 H), 6.93 (d,
J = 8.1 Hz, 2 H), 6.81 (t, J = 7.2 Hz, 1 H), 3.80 (sept, J = 6.7 Hz, 2 H), 1.24
(d, J = 6.7 Hz, 12 H).
13C NMR (101 MHz, CDCl3): δ = 148.11, 128.53, 119.66, 118.48, 47.73,
21.46.
HRMS (ESI): m/z [M + H]+ calcd for C12H20N: 178.1590; found:
178.1592.
Cross-Coupling Products 2; General Procedure
Under an N2 atmosphere, substrate 1 (0.2 mmol) and 1,2-diiodoben-
zene (IV) (0.1 mmol) were placed in a dry glass tube. Heptane (10 mL)
was added and the well-stirred mixture was irradiated under UV light
(300 nm) until the reaction was complete (TLC monitoring). The sol-
vent was removed in vacuo and the residue was purified by silica gel
column chromatography to afford the coupling product 2.
1-Phenylpiperidine (2d)
Yield: 10.1 mg (63%); yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.31–7.23 (m, 2 H), 6.96 (d, J = 7.9 Hz, 2
H), 6.83 (t, J = 7.3 Hz, 1 H), 3.20–3.13 (m, 4 H), 1.72 (dt, J = 11.3, 5.7 Hz,
4 H), 1.58 (qd, J = 6.3, 2.2 Hz, 2 H).
13C NMR (101 MHz, CDCl3): δ = 152.39, 129.13, 119.33, 116.68, 50.83,
26.00, 24.46.
N-Benzyl-N-isopropylaniline (2a)
HRMS (ESI): m/z [M
+
H]+ calcd for C11H16N: 162.1277;
Yield: 16.2 mg (72%); pale yellow oil.
found:162.1275.
1H NMR (400 MHz, CDCl3): δ = 7.38–7.31 (m, 4 H), 7.28–7.18 (m, 3 H),
6.79–6.68 (m, 3 H), 4.45 (s, 2 H), 4.30 (dq, J = 13.2, 6.6 Hz, 1 H), 1.25 (d,
J = 6.6 Hz, 6 H).
N-Cyclohexyl-N-methylaniline (2e)
Yield: 10.6 mg (56%); yellow oil.
13C NMR (101 MHz, CDCl3): δ = 149.41, 140.90, 129.23, 128.53,
126.52, 126.36, 116.51, 113.31, 48.52, 48.30, 20.00.
HRMS (ESI): m/z [M + Na]+ calcd for C16H19NNa: 248.1410; found:
248.1415.
1H NMR (400 MHz, CDCl3): δ = 7.29–7.21 (m, 2 H), 6.81 (d, J = 8.3 Hz, 2
H), 6.71 (t, J = 7.2 Hz, 1 H), 3.59 (tt, J = 11.3, 3.4 Hz, 1 H), 2.80 (s, 3 H),
1.90–1.78 (m, 4 H), 1.71 (d, J = 13.0 Hz, 1 H), 1.43 (qdd, J = 12.7, 10.7,
2.6 Hz, 4 H), 1.22–1.10 (m, 1 H).
13C NMR (101 MHz, CDCl3): δ = 150.31, 129.21, 116.37, 113.31, 58.28,
31.29, 30.18, 26.35, 26.09.
HRMS (ESI): m/z [M + H]+ calcd for C13H20N: 190.1590; found:
190.1585.
N,N-Diethylaniline (2b)
Yield: 10.9 mg (73%); yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.31–7.22 (m, 2 H), 6.73 (d, J = 8.1 Hz, 2
H), 6.69 (t, J = 7.2 Hz, 1 H), 3.39 (q, J = 7.1 Hz, 4 H), 1.26–1.16 (m, 6 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

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X. Zhao et al.
Special Topic
Synthesis
4-Phenylmorpholine (2f)
9-Allyl-9H-carbazole (4c)
Yield: 11.4 mg (70%); white solid; mp 49.0–49.8 °C.
Yield: 5.0 mg (24%); white solid; mp 52–53 °C.
1H NMR (400 MHz, CDCl3): δ = 7.29 (dt, J = 9.8, 4.9 Hz, 2 H), 6.91 (dd,
J = 17.8, 7.7 Hz, 3 H), 3.88 (dd, J = 10.7, 5.9 Hz, 4 H), 3.22–3.11 (m, 4 H).
13C NMR (101 MHz, CDCl3): δ = 151.42, 129.32, 120.18, 115.85, 67.08,
1H NMR (400 MHz, CDCl3): δ = 8.12 (d, J = 7.8 Hz, 2 H), 7.46 (t, J = 7.3
Hz, 2 H), 7.39 (d, J = 8.2 Hz, 2 H), 7.24 (d, J = 7.1 Hz, 2 H), 6.01 (ddd, J =
21.9, 10.1, 4.9 Hz, 1 H), 5.17 (d, J = 9.3 Hz, 1 H), 5.05 (d, J = 18.1 Hz, 1
H), 4.97–4.89 (m, 2 H).
13C NMR (151 MHz, CDCl3): δ = 140.52, 132.45, 125.83, 123.07,
120.49, 119.16, 116.93, 108.91, 45.41.
49.50.
HRMS (ESI): m/z [M + H]+ calcd for C10H14NO: 164.1070; found:
164.1065.
HRMS (ESI): m/z [M + H]+ calcd for C15H14N: 208.1121; found:
208.1115.
1,4-Diphenylpiperazine (2g)
Yield: 10.5 mg (44%); white solid; mp 153.5–154.5 °C.
1H NMR (400 MHz, CDCl3): δ = 7.30 (dd, J = 8.6, 7.4 Hz, 4 H), 6.99 (d,
J = 7.9 Hz, 4 H), 6.90 (t, J = 7.3 Hz, 2 H), 3.35 (s, 8 H).
9-Isopropyl-9H-carbazole (4d)
Yield: 10.0 mg (48%); white solid; mp 120.5–121.5 °C.
1H NMR (400 MHz, CDCl3): δ = 8.12 (d, J = 7.8 Hz, 2 H), 7.53 (t, J = 9.0
Hz, 2 H), 7.49–7.42 (m, 2 H), 7.23 (t, J = 7.4 Hz, 2 H), 5.08–4.94 (m, 1
H), 1.73 (d, J = 7.0 Hz, 6 H).
13C NMR (151 MHz, CDCl3): δ = 151.41, 129.34, 120.21, 116.49, 49.58.
HRMS (ESI): m/z [M + H]+ calcd for C16H19N2: 239.1543; found:
239.1545.
13C NMR (151 MHz, CDCl3): δ = 139.54, 125.45, 123.40, 120.45,
118.63, 110.10, 46.78, 20.95.
HRMS (ESI): m/z [M + H]+ calcd for C15H16N: 210.1277; found:
210.1277.
1-Phenylindoline (2h)
Yield: 9.8 mg (50%); pale yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.40–7.33 (m, 2 H), 7.24 (dd, J = 7.3, 6.4
Hz, 2 H), 7.18 (dd, J = 15.5, 6.0 Hz, 2 H), 7.09 (t, J = 7.4 Hz, 1 H), 7.01–
6.95 (m, 1 H), 6.76 (td, J = 7.3, 0.9 Hz, 1 H), 3.97 (t, J = 8.5 Hz, 2 H), 3.14
(t, J = 8.4 Hz, 2 H).
13C NMR (151 MHz, CDCl3): δ = 147.14, 144.23, 131.38, 129.27,
127.18, 125.15, 121.00, 118.93, 117.73, 108.21, 52.18, 28.28.
9-Benzyl-9H-carbazole (4e)
Yield: 10.8 mg (42%); white solid; mp 121.5–122.5 °C.
1H NMR (400 MHz, CDCl3): δ = 8.15 (d, J = 7.8 Hz, 2 H), 7.47–7.42 (m, 2
H), 7.38 (d, J = 8.1 Hz, 2 H), 7.30–7.22 (m, 5 H), 7.19–7.14 (m, 2 H),
5.53 (s, 2 H).
13C NMR (151 MHz, CDCl3): δ = 140.78, 137.30, 128.90, 127.57,
126.53, 125.98, 123.14, 120.52, 119.33, 109.02, 46.67.
HRMS (ESI): m/z [M + H]+ calcd for C14H14N: 196.1121; found:
196.1119.
HRMS (ESI): m/z [M + H]+ calcd for C19H16N: 258.1277; found:
258.1271.
Carbazoles 4; General Procedure
Under an N2 atmosphere, substrate 3 (0.2 mmol) and 1,2-diiodoben-
zene (IV) (0.1 mmol) were placed in a dry glass tube. Heptane (10 mL)
was added and the well-stirred mixture was irradiated under UV light
(300 nm) until the reaction was complete (TLC monitoring). The sol-
vent was removed in vacuo and the residue was purified by silica gel
column chromatography to afford the corresponding carbazole 4.
9-Cyclobutyl-9H-carbazole (4f)
Yield: 12.6 mg (57%); white solid; mp 100.5–101.3 °C.
1H NMR (400 MHz, CDCl3): δ = 8.11 (d, J = 7.8 Hz, 2 H), 7.60 (d, J = 8.3
Hz, 2 H), 7.49–7.41 (m, 2 H), 7.23 (dd, J = 11.0, 3.9 Hz, 2 H), 5.20 (quin,
J = 8.8 Hz, 1 H), 3.18–2.96 (m, 2 H), 2.73–2.58 (m, 2 H), 2.16–1.93 (m,
2 H).
9-Methyl-9H-carbazole (4a)
13C NMR (151 MHz, CDCl3): δ = 140.23, 125.49, 123.40, 120.41,
118.88, 110.32, 50.13, 29.40, 15.37.
Yield: 12.9 mg (71%); white solid; mp 91.5–92.5 °C. The yield of 4a
starting from 3v was 6.7 mg (37%).
1H NMR (400 MHz, CDCl3): δ = 8.11 (d, J = 7.8 Hz, 2 H), 7.49 (t, J = 7.6
Hz, 2 H), 7.41 (d, J = 8.1 Hz, 2 H), 7.30–7.20 (m, 2 H), 3.87 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 141.11, 125.80, 122.89, 120.44,
HRMS (ESI): m/z [M + H]+ calcd for C16H16N: 222.1277; found:
222.1275.
118.95, 108.55, 29.22.
9-Cyclopentyl-9H-carbazole (4g)
HRMS (ESI): m/z [M + H]+ calcd for C13H12N: 182.0964; found:
Yield: 14.1 mg (60%); white solid; mp 76.5–77.5 °C.
182.0964.
1H NMR (400 MHz, CDCl3): δ = 8.12 (d, J = 7.7 Hz, 2 H), 7.45 (ddd, J =
12.3, 9.5, 4.7 Hz, 4 H), 7.25–7.19 (m, 2 H), 5.16 (quin, J = 8.9 Hz, 1 H),
2.49–2.31 (m, 2 H), 2.23–2.01 (m, 4 H), 1.96–1.78 (m, 2 H).
9-Ethyl-9H-carbazole (4b)
13C NMR (151 MHz, CDCl3): δ = 139.73, 125.42, 123.38, 120.49,
118.68, 109.94, 55.81, 29.15, 25.49.
Yield: 10.2 mg (52%); white solid; mp 69–70 °C.
1H NMR (400 MHz, CDCl3): δ = 8.16 (d, J = 7.8 Hz, 2 H), 7.64–7.39 (m, 4
HRMS (ESI): m/z [M + Na]+ calcd for C17H17NNa: 258.1253; found:
258.1252.
H), 7.28 (t, J = 7.4 Hz, 2 H), 4.41 (q, J = 7.2 Hz, 2 H), 1.47 (t, J = 7.2 Hz, 3
H).
13C NMR (151 MHz, CDCl3): δ = 140.03, 125.72, 123.03, 120.54,
118.85, 108.54, 77.37, 76.95, 37.62, 13.93.
9-Cyclohexyl-9H-carbazole (4h)
HRMS (ESI): m/z [M + H]+ calcd for C14H14N: 196.1121; found:
Yield: 10.2 mg (41%); white solid; mp 142–143 °C.
196.1120.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

G
X. Zhao et al.
Special Topic
Synthesis
1H NMR (400 MHz, CDCl3): δ = 8.16 (d, J = 7.7 Hz, 2 H), 7.61 (d, J = 8.2
Hz, 2 H), 7.48 (t, J = 7.7 Hz, 2 H), 7.26 (dd, J = 9.8, 5.1 Hz, 2 H), 4.54 (tt,
J = 12.1, 3.6 Hz, 1 H), 2.52–2.38 (m, 2 H), 2.04 (t, J = 13.2 Hz, 4 H), 1.90
(d, J = 12.8 Hz, 1 H), 1.65–1.53 (m, 2 H), 1.50–1.40 (m, 1 H).
13C NMR (151 MHz, CDCl3): δ = 157.39 (d, J = 234.9 Hz), 141.91,
137.50, 126.39, 123.22 (d, J = 9.6 Hz), 122.44 (d, J = 4.1 Hz), 120.68,
118.92, 113.49 (d, J = 25.5 Hz), 109.02 (d, J = 9.1 Hz), 108.85, 106.14
(d, J = 23.7 Hz), 29.39.
13C NMR (101 MHz, CDCl3): δ = 139.81, 125.37, 123.38, 120.39,
HRMS (ESI): m/z [M + H]+ calcd for C13H11FN: 200.0870; found:
118.60, 110.34, 55.51, 30.86, 26.66, 25.82.
200.0872.
HRMS (ESI): m/z [M + H]+ calcd for C18H20N: 250.1590; found:
250.1589.
3-Chloro-9-methyl-9H-carbazole (4n)
Yield: 10.8 mg (50%); white solid; mp 40–41 °C.
1H NMR (400 MHz, CDCl3): δ = 8.07 (dd, J = 4.7, 2.8 Hz, 2 H), 7.57–7.50
9-Cycloheptyl-9H-carbazole (4i)
Yield: 10.5 mg (40%); white solid; mp 145–146 °C.
(m, 1 H), 7.47–7.40 (m, 2 H), 7.34–7.27 (m, 2 H), 3.84 (s, 3 H).
1H NMR (400 MHz, CDCl3): δ = 8.17 (d, J = 7.7 Hz, 2 H), 7.58 (d, J = 8.2
Hz, 2 H), 7.50 (t, J = 7.6 Hz, 2 H), 7.28 (t, J = 7.4 Hz, 2 H), 4.75 (tt, J =
11.0, 4.0 Hz, 1 H), 2.65–2.44 (m, 2 H), 2.13 (ddd, J = 13.5, 7.2, 3.3 Hz, 2
H), 1.98 (dt, J = 9.6, 6.3 Hz, 2 H), 1.92–1.68 (m, 6 H).
13C NMR (151 MHz, CDCl3): δ = 141.51, 139.38, 126.49, 125.78,
124.43, 123.93, 121.95, 120.60, 120.11, 119.32, 109.50, 108.81, 29.29.
HRMS (ESI): m/z [M + H]+ calcd for C13H11ClN: 216.0575; found:
216.0580.
13C NMR (101 MHz, CDCl3): δ = 139.53, 125.38, 123.29, 120.42,
118.57, 100.06, 57.48, 33.20, 27.89, 26.58.
HRMS (ESI): m/z [M + H]+ calcd for C19H22N: 264.1747; found:
9-Methyl-3-(trifluoromethyl)-9H-carbazole (4o)
Yield: 8.5 mg (34%); white solid; mp 55.5–56.5 °C.
264.1749.
1H NMR (400 MHz, CDCl3): δ = 8.36 (s, 1 H), 8.13 (d, J = 7.8 Hz, 1 H),
7.71 (dd, J = 8.6, 1.1 Hz, 1 H), 7.58–7.51 (m, 1 H), 7.45 (d, J = 8.3 Hz, 2
H), 7.34–7.28 (m, 1 H), 3.88 (s, 3 H).
9-(Tetrahydro-2H-pyran-4-yl)-9H-carbazole (4j)
Yield: 12.6 mg (50%); white solid; mp 217.5–218.5 °C.
13C NMR (151 MHz, CDCl3): δ = 142.46, 141.70, 126.79, 125.48 (q, J =
271.2 Hz), 121.18 (q, J = 32.2 Hz), 122.51, 122.49, 122.65 (q, J = 3.6
Hz), 120.69, 119.93, 117.98 (q, J = 4.1 Hz), 109.03, 108.61, 29.41.
HRMS (ESI): m/z [M + H]+ calcd for C14H11F3N: 250.0838; found:
250.0836.
1H NMR (400 MHz, CDCl3): δ = 8.14 (d, J = 7.7 Hz, 2 H), 7.61 (d, J = 8.3
Hz, 2 H), 7.52–7.44 (m, 2 H), 7.26 (t, J = 7.4 Hz, 2 H), 4.75 (tt, J = 12.4,
4.3 Hz, 1 H), 4.25 (dd, J = 11.6, 4.7 Hz, 2 H), 3.67 (td, J = 12.1, 1.8 Hz, 2
H), 2.82 (qd, J = 12.6, 4.7 Hz, 2 H), 1.88 (dd, J = 12.9, 2.5 Hz, 2 H).
13C NMR (151 MHz, CDCl3): δ = 139.54, 125.60, 123.48, 120.53,
118.99, 110.07, 68.17, 52.36, 30.62.
HRMS (ESI): m/z [M + H]+ calcd for C17H18NO: 252.1383; found:
3-Methoxy-9-methyl-9H-carbazole (4p)
Yield: 6.3 mg (30%); white solid; mp 97.5–98.5 °C.
252.1385.
1H NMR (400 MHz, CDCl3): δ = 8.06 (d, J = 7.8 Hz, 1 H), 7.60 (d, J = 2.4
Hz, 1 H), 7.47 (t, J = 7.6 Hz, 1 H), 7.37 (d, J = 8.2 Hz, 1 H), 7.31 (d, J = 8.8
Hz, 1 H), 7.20 (t, J = 7.4 Hz, 1 H), 7.13 (dd, J = 8.8, 2.5 Hz, 1 H), 3.94 (s, 3
H), 3.84 (d, J = 6.0 Hz, 3 H).
9H-Carbazole (4k)
Yield: 4.2 mg (25 %); white solid; mp 243–244 °C.
1H NMR (400 MHz, CDCl3): δ = 8.09 (t, J = 9.3 Hz, 3 H), 7.48–7.41 (m, 4
H), 7.30–7.22 (m, 2 H).
13C NMR (151 MHz, CDCl3): δ = 139.59, 125.97, 123.47, 120.47,
119.58, 110.71.
13C NMR (151 MHz, CDCl3): δ = 153.69, 141.62, 136.23, 125.77,
123.14, 122.68, 120.38, 118.46, 114.93, 109.24, 108.66, 103.46, 56.29,
29.32.
HRMS (ESI): m/z [M + H]+ calcd for C14H14NO: 212.1070; found:
212.1069.
HRMS (ESI): m/z [M + H]+ calcd for C12H10N: 168.0808; found:
168.0805.
5-Methyl-5H-[1,3]dioxolo[4,5-b]carbazole (4q)
Yield: 6.3 mg (28%); white solid; mp 127–128 °C.
9-Methyl-9H-carbazole-3-carbonitrile (4l)
Yield: 4.7 mg (23%); white solid; mp 92–93 °C.
1H NMR (400 MHz, CDCl3): δ = 7.93 (d, J = 7.8 Hz, 1 H), 7.47 (s, 1 H),
7.37 (q, J = 7.3 Hz, 2 H), 7.21–7.14 (m, 1 H), 6.89 (s, 1 H), 6.02 (s, 2 H),
3.79 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 147.48, 142.14, 140.85, 136.91,
124.17, 123.07, 119.40, 118.77, 115.86, 108.54, 101.16, 99.71, 90.27,
29.47.
1H NMR (400 MHz, CDCl3): δ = 8.39 (d, J = 1.0 Hz, 1 H), 8.10 (d, J = 7.8
Hz, 1 H), 7.71 (dd, J = 8.5, 1.5 Hz, 1 H), 7.60–7.54 (m, 1 H), 7.45 (t, J =
8.8 Hz, 2 H), 7.36–7.30 (m, 1 H), 3.89 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 142.70, 141.65, 129.12, 127.33,
125.34, 123.07, 121.96, 120.83, 120.78, 120.57, 109.27, 109.24,
101.68, 29.49.
HRMS (ESI): m/z [M + H]+ calcd for C14H12NO2: 226.0863; found:
226.0865.
HRMS (ESI): m/z [M + H]+ calcd for C14H11N2: 207.0917; found:
207.0915.
5,6-Dihydro-4H-pyrido[3,2,1-jk]carbazole (4r)
Yield: 11.0 mg (53%); white solid; mp 86–87 °C.
1-Fluoro-9-methyl-9H-carbazole (4m)
Yield: 10.3 mg (52%); white solid; mp 150–151 °C.
1H NMR (400 MHz, CDCl3): δ = 8.11 (d, J = 7.8 Hz, 1 H), 7.91 (d, J = 7.5
Hz, 1 H), 7.52–7.42 (m, 1 H), 7.36 (d, J = 8.1 Hz, 1 H), 7.23 (t, J = 7.5 Hz,
1 H), 7.19 (d, J = 7.8 Hz, 1 H), 7.15 (t, J = 7.3 Hz, 1 H), 4.27–4.12 (m, 2
H), 3.06 (t, J = 6.1 Hz, 2 H), 2.29 (dt, J = 12.0, 6.0 Hz, 2 H).
1H NMR (400 MHz, CDCl3): δ = 8.05 (d, J = 7.8 Hz, 1 H), 7.75 (dd, J = 8.9,
2.5 Hz, 1 H), 7.50 (t, J = 7.7 Hz, 1 H), 7.40 (d, J = 8.2 Hz, 1 H), 7.31 (dd,
J = 8.8, 4.2 Hz, 1 H), 7.22 (ddd, J = 11.4, 7.2, 2.7 Hz, 2 H), 3.85 (s, 3 H).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

H
X. Zhao et al.
Special Topic
Synthesis
13C NMR (151 MHz, CDCl3): δ = 139.95, 137.89, 125.35, 123.08,
122.92, 120.97, 120.95, 120.63, 118.84, 118.60, 118.06, 108.30, 41.04,
25.04, 22.51.
HRMS (ESI): m/z [M + Na]+ calcd for C15H13NNa: 230.0940; found:
230.0933.
Funding Information
We are grateful for the financial support from China NSFC (Nos.
21372055, 21472030 and 21672047) and SKLUWRE (No. 2018DX02).
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Supporting Information
Supporting information for this article is available online at
Combined yield (1:1 mixture of regioisomers): 10.3 mg (48%); white
solid.
https://doi.org/10.1055/s-0037-1609444.
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1H NMR (400 MHz, CDCl3): δ = 8.61 (d, J = 7.9 Hz, 0.47 H), 8.04 (d, J =
7.8 Hz, 0.47 H), 7.96 (d, J = 8.3 Hz, 0.45 H), 7.56–7.45 (m, 1 H), 7.38
(dd, J = 17.0, 9.1 Hz, 2 H), 7.32–7.23 (m, 1.69 H), 7.20 (ddd, J = 9.9, 6.3,
1.3 Hz, 1 H), 3.82 (dd, J = 13.7, 5.4 Hz, 3 H).
13C NMR (151 MHz, CDCl3): δ = 142.17, 141.65, 141.38, 141.10,
131.57, 128.90, 126.35, 126.10, 125.99, 123.19, 122.37, 121.91,
121.47, 121.21, 120.38, 120.10, 119.80, 119.51, 119.47, 119.44,
108.78, 108.76, 108.39, 106.92, 29.40, 29.29.
References
(1) (a) Hong, Y.; Senanayake, C. H.; Xiang, T.; Vandenbossche, C. P.;
Tanoury, G. J.; Bakale, R. P.; Wald, S. A. Tetrahedron Lett. 1998,
39, 3121. (b) Huyskens, F. L.; Huyskens, P. L.; Persoons, A. P.
J. Chem. Phys. 1998, 108, 8161. (c) Kuwano, R.; Utsunomiya, M.;
Hartwig, J. F. J. Org. Chem. 2002, 67, 6479. (d) Corbet, J. P.;
Mignani, G. Chem. Rev. 2006, 106, 2651.
HRMS (ESI): m/z [M + H]+ calcd for C13H11ClN: 216.0575; found:
(2) (a) Fors, B. P.; Buchwald, S. L. J. Am. Chem. Soc. 2010, 132, 15914.
(b) Beletskaya, I. P.; Cheprakov, A. V. Organometallics 2012, 31,
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Organometallics 2012, 31, 3402.
216.0585.
2,9-Dimethyl-9H-carbazole (4t) and 4,9-Dimethyl-9H-carbazole
(4t′)
(3) For Buchwald–Hartwig reactions, see: (a) Marion, N.; Navarro,
O.; Mei, J.; Stevens, E. D.; Scott, N. M.; Nolan, S. P. J. Am. Chem.
Soc. 2006, 128, 4101. (b) Lee, D. H.; Taher, A.; Hossain, S.; Jin, M.
J. Org. Lett. 2011, 13, 5540. (c) Shelkar, R. S.; Shendage, S. S.;
Nagarkar, J. M. Tetrahedron Lett. 2013, 54, 3233. (d) Topchiy, M.
A.; Asachenko, A. F.; Nechaev, M. S. Eur. J. Org. Chem. 2014, 3319.
(e) Ruiz-Castillo, P.; Blackmond, D. G.; Buchwald, S. L. J. Am.
Chem. Soc. 2015, 137, 3085. For Ullmann reactions, see: (f) Ma,
D.; Cai, Q.; Zhang, H. Org. Lett. 2003, 5, 2453. (g) Zhou, F.; Guo, J.;
Liu, J.; Ding, K.; Yu, S.; Cai, Q. J. Am. Chem. Soc. 2012, 134, 14326.
(4) (a) Bissember, A. C.; Lundgren, R. J.; Creutz, S. E.; Peters, J. C.; Fu,
G. C. Angew. Chem. Int. Ed. 2013, 52, 5129. (b) Ziegler, D. T.; Choi,
J.; Muñoz-Molina, J. M.; Bissember, A.; Peters, J. C.; Fu, G. C.
J. Am. Chem. Soc. 2013, 135, 13107. (c) Matier, C. D.; Schwaben,
J.; Peters, J. C.; Fu, G. C. J. Am. Chem. Soc. 2017, 139, 17707.
(5) Oderinde, M. S.; Jones, N. H.; Juneau, A.; Frenette, M.; Aquila, B.;
Tentarelli, S.; Robbins, D. W.; Johannes, J. W. Angew. Chem. Int.
Ed. 2016, 55, 13219.
Combined yield (3:5 mixture of regioisomers): 10.1 mg (52%); white
solid.
1H NMR (400 MHz, CDCl3): δ = 8.30 (d, J = 7.9 Hz, 0.64 H), 8.20–8.02
(m, 0.78 H), 7.67–7.28 (m, 4.77 H), 7.21–7.06 (m, 1 H), 3.85 (d, J = 11.9
Hz, 3 H), 3.06–2.95 (m, 1.91 H), 2.67 (s, 1.15 H).
13C NMR (151 MHz, CDCl3): δ = 141.52, 141.12, 141.09, 140.99,
135.90, 133.47, 125.54, 125.19, 125.11, 123.49, 122.95, 122.65,
121.35, 120.56, 120.44, 120.06, 120.05, 118.88, 118.81, 108.75,
108.40, 108.26, 106.10, 29.09, 28.99, 22.39, 20.94.
HRMS (ESI): m/z [M + H]+ calcd for C14H14N: 196.1121; found:
196.1126.
9-Methyl-9H-carbazole (4a) and 1,9-Dimethyl-9H-carbazole (4u)
Combined yield (6:1 mixture of regioisomers): 7.3 mg (40%); white
solid.
1H NMR (400 MHz, CDCl3): δ = 8.13 (d, J = 7.8 Hz, 2 H), 8.09 (d, J = 7.8
Hz, 0.18 H), 7.97 (d, J = 7.6 Hz, 0.18 H), 7.55–7.49 (m, 2 H), 7.48–7.46
(m, 0.18 H), 7.42 (d, J = 8.2 Hz, 2 H), 7.39 (d, J = 8.3 Hz, 0.19 H), 7.32–
7.25 (m, 2 H), 7.24–7.21 (m, 0.17 H), 7.20 (d, J = 7.0 Hz, 0.17 H), 7.13
(t, J = 7.4 Hz, 0.18 H), 4.13 (s, 0.5 H), 3.87 (s, 3 H), 2.88 (s, 0.5 H).
(6) For selected reviews, see: (a) Knölker, H. J.; Reddy, K. R. Chem.
Rev. 2002, 102, 4303. (b) Li, J.; Grimsdale, A. C. Chem. Soc. Rev.
2010, 39, 2399. (c) Schmidt, A. W.; Reddy, K. R.; Knölker, H. J.
Chem. Rev. 2012, 112, 3193.
(7) (a) Venkateswararao, A.; Thomas, K. R. J.; Lee, C. P.; Li, C. T.; Ho,
K. C. ACS Appl. Mater. Interfaces 2014, 6, 2528. (b) Dijken, A. V.;
Bastiaansen, J. J. A. M.; Kiggen, N. M. M.; Langeveld, B. M. V.;
Rothe, C.; Monkman, A.; Bach, I.; Stossel, P.; Brunner, K. J. Am.
Chem. Soc. 2004, 126, 7718. (c) Qian, X.; Zhu, Y. Z.; Chang, W. Y.;
Song, J.; Pan, B.; Lu, L.; Gao, H. H.; Zheng, J. Y. ACS Appl. Mater.
Interfaces 2015, 7, 9015.
13C NMR (151 MHz, CDCl3): δ = 141.75, 141.10, 139.81, 128.92,
125.79, 125.68, 123.63, 123.03, 122.87, 120.50, 120.43, 120.11,
119.17, 118.97, 118.94, 118.34, 108.65, 108.54, 32.42, 29.19, 20.52.
HRMS (ESI): m/z [M + H]+ calcd for C14H14N: 196.1121; found:
196.1124.
(8) (a) Noji, T.; Fujiwara, H.; Okano, K.; Tokuyama, H. Org. Lett.
2013, 15, 1946. (b) Jordan-Hore, J. A.; Johansson, C. C. C.; Gulias,
M.; Beck, E. M.; Gaunt, M. J. J. Am. Chem. Soc. 2008, 130, 16184.
(c) Ackermann, L.; Althammer, A. Angew. Chem. Int. Ed. 2007, 46,
1627. (d) Humne, V.; Dangat, Y.; Vanka, K.; Lokhande, P. Org.
Biomol. Chem. 2014, 12, 4832. (e) Kuwahara, A.; Nakano, K.;
Nozaki, K. J. Org. Chem. 2005, 70, 413.
N-Methyl-N-phenylaniline (3A)
1H NMR (400 MHz, CDCl3): δ = 7.46–7.35 (m, 4 H), 7.16 (dd, J = 8.6, 0.9
Hz, 4 H), 7.08 (t, J = 7.3 Hz, 2 H), 3.43 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 149.12, 129.27, 121.35, 120.53, 40.30.
The analytical data match those reported in the literature.2c
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–I

I
X. Zhao et al.
Special Topic
Synthesis
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