Gold(i)-catalyzed synthesis of 2-substituted indoles from 2-alkynylnitroarenes with diboron as reductant

Article abstract of DOI:10.1039/c7ob01918a

An efficient method for the synthesis of 2-substituted indoles via a diboron/base promoted tandem reductive cyclization of o-alkynylnitroarene under Au catalysis conditions has been disclosed. This reaction is efficient and convenient, affording 2-substituted indoles with broad functional groups tolerance and excellent yields.

Full text of DOI:10.1039/c7ob01918a

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Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
benzene
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Gold(I)-Catalyzed Synthesis of 2-Substituted Indoles from 2-
Alkynylnitroarenes with Diboron as Reductant
Wenqiang Fu,a Kai Yang,a Jinglong Chenb and Qiuling Song*a
Received 00th January 20xx,
Accepted 00th January 20xx
An efficient method for the synthesis of 2-substituted indoles via a diboron/base promoted tandem reductive cyclization
of o-alkynylnitroarene under Au catalysis conditions has been disclosed. This reaction is efficient and convenient, affording
2-substituted indoles with broad functional groups tolerance and excellent yields.
DOI: 10.1039/x0xx00000x
www.rsc.org/
as effective catalysts for the activation of C-C triple bonds,8 we
1. Introduction
The indole ring constitutes one of the most significant
structural skeletons in pharmacologically and biologically active
molecules.1 Among them, 2-substituted indoles represent a
subclass of biologically and synthetically useful scaffolds.2 They
are also present in medicinally-active compounds, such as
Heterocombretastatin, CDK inhibitors and cytotoxic agents,
etc.3 (Figure 1). Traditional methods for the preparation of 2-
substituted indoles are mainly based on the Fischer indole
synthesis,4 however, harsh reaction conditions sometimes limit
the functional group tolerance. Thus, the development of
efficient methods to construct these molecules has
evoked considerable attention. Among the various indole
syntheses, the metal- or base-catalyzed preparation of indoles
starting from 2-alkynylanilines has been predominant.5
However, the application of 2-nitroarylacetylenes to construct
indoles via one step has been rarely reported in previous works.
In 2009, the Tokunaga group reported a two-step in one
pot reaction by converting 1-ethynyl-2-nitrobenzene
derivatives to 2-substituted indoles with nano-Au/Fe2O3 as
catalyst in hydrogen atmosphere (Scheme 1a),6 nevertheless,
high temperature, high hydrogen pressure as well as special
reaction apparatus limits the practical application in organic
synthesis. Recently, we have reported the diborane-mediated
deoxygenation of 2-nitrostyrenes to form indoles via reductive
cyclization in good to high yields (Scheme 1b).7 However, when
2-nitroarylacetylenes was subjected to the previous system, no
desired indole was observed. As gold complexes have emerged
Figure 1 Several active molecules containing 2-substituted
indoles.
examined their use in the reductive cyclization of 2-
alkynylnitroarenes to form indoles. It is well-known that
stoichiometric amount of metal reductants, such as Zn,9 Ni,10
In,11 have been employed as reductant to reduce nitro group to
amino group, however, the waste from these reductive agents
cause the isolation of the aniline products troublesome from
the
reaction
mixture.
Despite
the
fact
that
diboron reagents have been widely used in organic synthesis as
an efficient borylation agent,12 their use as reductants13 has
rarely been reported in synthesis of indoles. As part of our
a Institute of Next Generation Matter Transformation, College of Chemical
Engineering & College of Material Sciences Engineering at Huaqiao University, 668
Jimei Blvd, Xiamen, Fujian, 361021, P. R. China
Fax: 86-592-6162990; email: qsong@hqu.edu.cn
b Quanzhou Jersey Biosciences, Quanzhou, Fujian, 362200, P. R. China
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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Scheme 1 a, b) Recent important advance about indole
synthesis. c) This study.
1p and 2-(thiophen-2-yl)-1H-indole 1q were also good
candidates in this indole transformation, giving the
Table 1 Optimization of the reaction for synthesis of 2-phenyl-
1H-indole 2a
.
continuous interest in the development of new synthetic
methods of new organoboron compound as well as discovery
of new reactivity of diboron compounds, we envision that in
the presence of both Au catalyst and diboron reagent, 2-
alkynyl nitroarene could be smoothly transformed into 2-
substituted indoles in suitable conditions (Scheme 1c). Herein,
we report an indole synthesis via gold catalyzed reductive
cyclization to convert 2-alkynylnitroarenes into 2-substituted
indoles with diboron as reductant.
2. Results and discussion
We commenced our hypothesis by using 1-nitro-2-
(phenylethynyl)benzene (1a) as the substrate and B2cat2 as
reductant for the reaction optimization. The initial reaction was
using
commercially
available
1,3-bis(2,6-
diisopropylphenyl)imidazol-2-ylidene gold(I)chloride (IPrAuCl) as
o
the catalyst and heated at 100 C in THF (Table 1). As a result,
the desired 2-phenyl-1H-indole (2a) was indeed formed in 29%
yield (Table 1, entry 2) via a reductive cyclization in presence of
2.0 equiv of Na2CO3 and 2.0 equiv of B2cat2. Subsequently, we
systematically investigated various bases and NaOtBu
demonstrated to be the optimal one (Table 1, entries 1-5). We
also screened the solvent effect, which revealed that CH3CN
was superior to DCE and THF (Table 1, entries 6-7). To our
delight, when the amount of B2cat2 was increased to 3.5 equiv,
the desired product 2a was obtained in 78% isolated yield
(Table 1, entry 8). Interestingly, when B2pin2 was used instead
of B2cat2, no amount of product 2a was detected (Table 1,
entry 9), which disclosed the specific reactivity of B2cat2 for this
reaction. No corresponding product 2a was observed when the
reaction was performed under air (Table 1, entry 10). Whereas,
an array of different gold sources and metal salts were tested
and stagnant reactions were observed by using Ph3PAuCl,
Tf2NAuCl, FeCl3, ZnCl2 and NiCl2 as catalysts (Table 1, entries
11-15), which indicated remarkable catalytic performance of
the IPrAuCl as Lewis acid. Notably, only marginal
improvements were gained when the reaction temperature
was reduced to 70oC and the reaction time was decreased to 6
h (Table 1, entries 16-17). Controlled experiment was carried
out without IPrAuCl (Table 1, entry 18) no product 2a was
detected, and that conclusiveness of IPrAuCl as catalyst.
corresponding desired products 2p and 2q in 70% and 56%
yields respectively. In addition to the R2 groups, we also
investigated the effect of R1 groups on 1-nitro-2-
(phenylethynyl)benzene derivatives (1r-1v). To our satisfaction,
R1
catalyst, base
R1
R2
R2
+
B2cat2
solvent, 100 o
C
N
H
NO2
1, 0.2 mmol
2
F
Cl
N
H
N
H
N
H
2a, 78%
2b, 75%
2c, 73%
4
CF3
O
O
N
N
H
N
H
H
2d, 73%
2e, 62%
2f, 55%
n
N
H
N
H
N
H
2j, 64%
2k, 77%
2g, n=0, 82%
2h, n=1, 67%
2i, n=2, 78%
N
H
N
H
F
Cl
2l, 61%
2m, 66%
N
N
H
N
H
N
H
The optimal reaction conditions (entry 8, Table 1) were
used to explore the scope and limitation of indole synthesis
2n, 74%
2o, 78%
2p, 70%
S
(Table 2).
A
number of functionalized 1-nitro-2-
N
H
N
H
N
H
F
(phenylethynyl)benzene derivatives were inspected initially. It
is noteworthy that electronic effects of substituents on the
aromatic rings of 1-nitro-2-(phenylethynyl)benzene derivatives
had no significant influence and corresponding indoles were
2q, 56%
2r, 48%
2s, 64%
F
N
H
N
H
N
H
Cl
2t, 44%
2u, 83%
2v, 66%
obtained in good yields (2a-2l). When the sterically demanding
N
N
((2-nitrophenyl)ethynyl)naphthalenes
(
1n and 1o) were
N
H
N
H
NH2
2w', 33%
submitted to the standard conditions, respectively, the
corresponding products 2n and 2o were obtained in 74% and
78% yield. To our delight, 3-((2-nitrophenyl)ethynyl)quinoline
2xa, 36%
2w, 0%
Reaction condition: 1 (0.2 mmol), NaOtBu (2 equiv), IPrAuCl (2.5 mol%), B2cat2 (3.5 equiv) and
CH3CN (2 mL), at 100 oC under N2, 12 h. a) NaOMe (2eq).
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of hydroxylamine 11 14b
the aminate 13 14b
state 14 by
cation.17 Finally, protonation of intermediate 15 to give the
corresponding product 2w'
.
Then deoxygenation of 12 generates
Scheme 2 Synthesis of 2-substituted indoles through 2-alkynyl
nitroarenes.
the desired 2-substituted indoles were achieved in moderate to
,
which is further translated into transition
c
oordinating with the catalytically active gold
good yields (2r-2v). Of note, when the 3-nitro-2-
(phenylethynyl)pyridine 1w was used as substrate, no
corresponding indole product 2w was observed, instead,
reduced product (E)-2-styrylpyridin-3-amine 2w' was obtained
in 33% yield. Probably due to the strong coordination of
.
pyridine ring, which lead to the undesired reduction of 1w
.
Whereas 2p containing a 3-quinoline framework was obtained
in good yield owing to the weaker coordination of quinoline
than pyridine. In addition to the aromatic substituents of R2
group, the substrate 1x bearing the cyclopropyl substituent
was also amenable to this reaction, albeit low yield of 2x was
obtained.
Scheme 4 Potential reaction intermediates.
Some extra experiments were implemented to obtain more
information for the verification of the reaction mechanism. In
our previous work,7 2-phenyl-1H-indol-1-ol 16 could be
deoxygenated to produce 2-phenylindol 2a (Scheme 4a). Not
surprisingly, when 2-phenyl-1H-indol-1-ol 16 was subjected to
standard conditions, 98% yield of 2-phenylindol 2a was
obtained. And 90% yield of 2-phenylindol 2a was also achieved,
when the reaction was performed without IPrAuCl (Scheme
4b), which suggests that oxygen-borane of species 5 might be
formed in the absence of Au leading to the formation of the
desired product. When the 2-(phenylethynyl)aniline 17 and (E)-
2-styrylaniline 18 was used as substrates under standard
conditions, no 2-phenylindol 2a was observed (Scheme 4c, 4d),
which verified that this reaction doesn’t undergo the two-step
process via reduction of 1-nitro-2-(phenylethynyl)benzene to
amine first and subsequent cyclization of 2-ethynylaniline to
lead to indoles.
Scheme 3 Plausible Mechanism
On the basis of previous report,7,14 the plausible reaction
mechanism for the formation of indoles is described in Scheme
3. Initially, base activate diboron to generate the anionic sp2-
sp3 diborane reagents
water, the nucleophile
intermediate 4 14b,15
Rearrangement of
mediated deoxygenation14 of
6 14b
which is further transformed into species
Afterwards, base-mediated deboronation of
borate-nitroso anion 8 7,16
which attacks the carbon-carbon reaction
triple bond in the presence of IPrAuCl to render the alkynylnitroarenes derivatives to render indole derivatives.
intermediate
via a 6π-electron-5-atom electrocyclization.7 Our future work is aimed at further mechanistic studies and
Subsequently, once again B2cat2-mediated deoxygenation of synthetic application of this novel protocol.
3
[B2cat2tBuO]-.14b With the help of
attaches to engender the
and diborane-
3
1
3. Conclusions
.
4
5
produces the nitroso species In conclusion, we have disclosed a Au-catalyzed synthesis of 2-
with B2cat2.7 substituted indoles from 2-alkynylnitroarenes derivatives by
generates the using B2cat2 as a reductant. Our experiments suggest that this
undergoes reductive cyclization of 2-
,
7
7
,
9
species
indoles
9
and protonation of 10 deliver the 2-substituted
2. Especially, when 1w was used as substrate, 3-
4. Experimental section
nitroso-pyridine species 6w was formed as the represented
path in the top of Scheme 3. In the presence of , 3-nitroso-
3
4.1 General information
pyridine species 6w is transformed to 12 which is an analogue
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All chemicals were purchased from Adamas Reagent, energy (m, 1H). 13C NMR (125 MHz, CDCl3) δ 137.9, 136.8, 132.4, 129.3,
chemical company, J&K Scientific Ltd, Bide Pharmatech Ltd and 129.1, 127.8, 125.2, 122.4, 120.7, 120.3, 110.9, 100.0.
Tansoole. Unless stated otherwise, reactions were performed in
oven-dried or flame-dried glassware using a Schlenk line under a according to the general procedure
2-(4-fluorophenyl)-1H-indole (2b).18 Compound 2b was prepared
(petroleum ether/ethyl
A
nitrogen atmosphere. All solvents were commercially obtained, and acetate = 50:1 v/v). The product was obtained as a white solid in
1
reactions were performed without specific drying of solvents. Flash 75% yield. H NMR (500 MHz, CDCl3) δ 8.23 (s, 1H), 7.69 – 7.57 (m,
column chromatography was performed over silica gel (200-300 3H), 7.40 (d, J = 8.0 Hz, 1H), 7.22 (t, J = 7.5 Hz, 1H), 7.18 – 7.11 (m,
mesh).
3H), 6.77 (s, 1H). 13C NMR (125 MHz, CDCl3) δ 162.4 (d, J = 246.1
1H-NMR and 13C-NMR spectra were recorded in CDCl3 on a Hz), 137.0, 136.8, 129.3, 128.7, 126.9 (d, J = 8.0 Hz), 122.4, 120.7,
Bruker Avance 500 spectrometer (500 MHz 1H, 125 MHz 13C) at 120.4, 116.1 (d, J = 21.8 Hz), 110.9, 100.0.
room temperature. Chemical shifts were reported in ppm on the
scale relative to CDCl3 (δ = 7.26 for 1H-NMR , δ = 77.00 for 13C-NMR) according to the general procedure
2-(4-chlorophenyl)-1H-indole (2c).18 Compound 2c was prepared
(petroleum ether/ethyl
A
as an internal reference. Coupling constants (J) were reported in acetate = 50:1 v/v). The product was obtained as a white solid in
1
Hertz (Hz).The following abbreviations are used to indicate signal 73% yield. H NMR (500 MHz, CDCl3) δ 8.25 (s, 1H), 7.64 (d, J = 7.8
multiplicity: s = singlet, d = doublet, t = triplet, q = quartet, m = Hz, 1H), 7.59 – 7.52 (m, 2H), 7.40 (t, J = 8.7 Hz, 3H), 7.22 (t, J = 7.6
multiplet, and br = broad. High resolution mass spectra were Hz, 1H), 7.15 (t, J = 7.5 Hz, 1H), 6.81 (d, J = 0.8 Hz, 1H). 13C NMR (125
recorded using a Thermo Fisher Scientific LTQ FT Ultra or Waters MHz, CDCl3) δ 136.9, 136.7, 133.4, 130.9, 129.2, 129.1, 126.3, 122.7,
Micromass GCT Premier instrument.
120.7, 120.4, 110.9, 100.4.
2-(4-(trifluoromethyl)phenyl)-1H-indole (2d).18 Compound 2d
4.2 General procedure for starting materials (1)
was prepared according to the general procedure
A
(petroleum ether/ethyl acetate 50:1 v/v). The product was
=
1
To
a solution of 1-nitro-2-iodobenzene (2.0 mmol) in
obtained as a white solid in 73% yield. H NMR (500 MHz, CDCl3) δ
8.38 (s, 1H), 7.76 (d, J = 8.2 Hz, 2H), 7.68 (dd, J = 18.4, 8.1 Hz, 3H),
7.43 (d, J = 8.1 Hz, 1H), 7.23 (d, J = 7.4 Hz, 1H), 7.15 (t, J = 7.5 Hz,
1H), 6.93 (d, J = 1.7 Hz, 1H). 13C NMR (125 MHz, DMSO) δ 137.9,
136.5, 136.3, 128.8, 127.7 (d, J = 31.3 Hz), 126.31 (d, J = 3.8 Hz),
125.8, 124.8 (d, J = 270.0 Hz), 122.9, 121.0, 120.2, 112.0, 101.2.
2-(4-methoxyphenyl)-1H-indole (2e).6 Compound 2e was
triethylamine (10 ml) at room temperature was added PdCl2(PPh3)2
(0.028 g, 0.02 mmol). The resultant suspension was stirred for 10
min followed by addition of alkynes (2.2 mmol) and then CuI (0.015
g, 0.04 mmol). This mixture was then stirred for 6 h. The reaction
mixture was washed with NH4Cl aq. (sat.) and brine, and dry over
Na2SO4. The solvent were removed, and the residue was subjected
to silica-gel column chromatography.
prepared
(petroleum ether/ethyl acetate
according
to
the
=
general
procedure
B
10:1 v/v). The product was
1
4.3 General process for the synthesis of 2-Substituted Indoles (2)
obtained as a white solid in 62% yield. H NMR (500 MHz, CDCl3) δ
8.26 (s, 1H), 7.60 (dd, J = 7.8, 5.6 Hz, 3H), 7.39 (d, J = 8.0 Hz, 1H),
7.14 (dt, J = 30.3, 7.3 Hz, 2H), 6.98 (d, J = 8.6 Hz, 2H), 6.72 (s, 1H),
3.86 (s, 3H).13C NMR (125 MHz, CDCl3) δ 160.0, 138.0, 136.7, 129.4,
126.5, 125.2, 121.9, 120.4, 120.2, 114.5, 110.7, 98.9, 55.4.
General procedure A. To a mixture of 1-nitro-2-alkynylbenezenes
1 (0.2 mmol, 1.0 equiv), B2cat2 (167 mg, 3.5 equiv) and IPrAuCl (3.1
mg, 2.5 mol%) was added NaOtBu (38.4 mg, 2.0 equiv), MeCN (2
mL). The resulting mixture was heated to 100 °C. After 12 h, the
mixture was cooled to room temperature. The solution was
extracted with 3 × 10 mL of ethyl acetate. The combined organic
phases were washed with 2 × 10 mL of brine. The resulting organic
phase was dried over Na2SO4. Upon completion of the reaction, the
solvent was evaporated under reduced pressure and the residue
was purified by flash column chromatograph to give the desired
product 2.
General procedure B. To a mixture of 1-nitro-2-alkynylbenezenes
1 (0.2 mmol, 1.0 equiv), B2cat2 (167 mg, 3.5 equiv) and IPrAuCl (3.1
mg, 2.5 mol%) was added NaOtBu (38.4mg, 2 equiv), MeCN (2 mL).
The resulting mixture was heated to 100 °C. After 12 h, the mixture
was cooled to room temperature. The solution was extracted with 3
× 10 mL of ethyl acetate. The combined organic phases were
washed with 5 × 10 mL of K2CO3 aq. (sat.). The resulting organic
phase was dried over Na2SO4. Upon completion of the reaction, the
solvent was evaporated under reduced pressure and the residue
was purified by flash column chromatograph to give the desired
product 2.
2-(4-(pentyloxy)phenyl)-1H-indole (2f).19 Compound 2f was
prepared
(petroleum ether/ethyl acetate
according
to
the
=
general
procedure
A
50:1 v/v). The product was
1
obtained as a white solid in 55% yield. H NMR (500 MHz, CDCl3) δ
8.25 (s, 1H), 7.62 (d, J = 7.8 Hz, 1H), 7.57 (d, J = 8.6 Hz, 2H), 7.38 (d, J
= 8.0 Hz, 1H), 7.18 (t, J = 7.5 Hz, 1H), 7.12 (t, J = 7.4 Hz, 1H), 6.97 (d,
J = 8.6 Hz, 2H), 6.72 (s, 1H), 4.00 (t, J = 6.6 Hz, 2H), 1.86 – 1.79 (m,
2H), 1.48 – 1.39 (m, 4H), 1.29 (d, J = 12.3 Hz, 2H), 0.96 (t, J = 7.1 Hz,
3H). 13C NMR (125 MHz, CDCl3) δ 159.0, 138.1, 136.6, 129.5, 126.5,
125.0, 121.9, 120.3, 120.2, 115.0, 110.7, 98.7, 68.2, 29.0, 28.2, 22.5,
14.1.
2-(p-tolyl)-1H-indole (2g).18 Compound 2g was prepared
according to the general procedure
A (petroleum ether/ethyl
acetate = 50:1 v/v). The product was obtained as a white solid in
1
82% yield. H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.64 (d, J = 7.8
Hz, 1H), 7.58 – 7.55 (m, 2H), 7.40 (dd, J = 8.1, 0.8 Hz, 1H), 7.26 (d, J =
7.9 Hz, 2H), 7.22 – 7.17 (m, 1H), 7.13 (td, J = 7.5, 1.0 Hz, 1H), 6.80
(dd, J = 2.1, 0.7 Hz, 1H), 2.41 (s, 3H). 13C NMR (125 MHz, CDCl3) δ
138.1, 137.7, 136.7, 129.7, 129.6, 129.4, 125.1, 122.1, 120.5, 120.2,
110.8, 99.4, 21.3.
4.4 Characterization data for products
2-(4-ethylphenyl)-1H-indole (2h). Compound 2h was prepared
according to the general procedure
A (petroleum ether/ethyl
2-phenyl-1H-indole (2a).18 Compound 2a was prepared
acetate = 50:1 v/v). The product was obtained as a white solid in
according to the general procedure
A (petroleum ether/ethyl
1
67% yield. H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.66 (d, J = 7.8
acetate = 50:1 v/v). The product was obtained as a white solid in
78% yield. 1H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.67 (dt, J = 7.5,
4.0 Hz, 3H), 7.46 (t, J = 7.7 Hz, 2H), 7.41 (dd, J = 8.1, 0.8 Hz, 1H), 7.38
– 7.32 (m, 1H), 7.25 – 7.18 (m, 1H), 7.18 – 7.10 (m, 1H), 6.89 – 6.80
Hz, 1H), 7.60 (d, J = 8.1 Hz, 2H), 7.40 (d, J = 8.0 Hz, 1H), 7.30 (d, J =
8.0 Hz, 2H), 7.22 (t, J = 7.6 Hz, 1H), 7.15 (td, J = 7.6, 0.9 Hz, 1H), 6.82
(s, 1H), 2.72 (q, J = 7.6 Hz, 2H), 1.32 – 1.29 (m, 3H). 13C NMR (125
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MHz, CDCl3) δ 144.1, 138.1, 136.7, 129.8, 129.4, 128.6, 125.2, 122.1, (petroleum ether/ethyl acetate
ARTICLE
=
50:1 v/v). The product was
1
120.6, 120.2, 110.9, 99.5, 28.7, 15.6. HRMS (ESI, m/z): calculated for obtained as a white solid in 78% yield. H NMR (500 MHz, CDCl3) δ
C16H15N [M+H]+: 222.1277; found: 222.1279.
2-(4-propylphenyl)-1H-indole (2i).20 Compound 2i was prepared 7.60 – 7.49 (m, 2H), 7.46 (d, J = 8.0 Hz, 1H), 7.26 (d, J = 7.6 Hz, 1H),
according to the general procedure
(petroleum ether/ethyl 7.19 (t, J = 7.4 Hz, 1H), 6.99 (s, 1H). 13C NMR (125 MHz, CDCl3) δ
8.48 (s, 1H), 8.07 (s, 1H), 7.97 – 7.80 (m, 4H), 7.71 (d, J = 7.8 Hz, 1H),
A
acetate = 50:1 v/v). The product was obtained as a white solid in 137.8, 137.0, 133.5, 132.8, 129.6, 129.3, 128.7, 128.0, 127.8, 126.7,
1
78% yield. H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.63 (d, J = 7.8 126.1, 123.8, 123.0, 122.5, 120.7, 120.3, 110.9, 100.6.
Hz, 1H), 7.59 (d, J = 8.1 Hz, 2H), 7.40 (d, J = 8.0 Hz, 1H), 7.26 (d, J =
8.0 Hz, 2H), 7.22 – 7.16 (m, 1H), 7.13 (t, J = 7.5 Hz, 1H), 6.80 (d, J = according to the general procedure
3-(1H-indol-2-yl)quinoline (2p).25 Compound 2p was prepared
B
(petroleum ether/ethyl
1.3 Hz, 1H), 2.68 – 2.60 (m, 2H), 1.74 – 1.63 (m, 2H), 0.98 (t, J = 7.3 acetate = 10:1 v/v). The product was obtained as a yellow solid in
Hz, 3H). 13C NMR (125 MHz, CDCl3) δ 142.5, 138.1, 136.7, 129.8, 70% yield. 1H NMR (500 MHz, DMSO) δ 11.86 (s, 1H), 9.47 (d, J = 2.3
129.4, 129.1, 125.1, 122.1, 120.5, 120.2, 110.8, 99.4, 37.8, 24.5, Hz, 1H), 8.74 (d, J = 2.1 Hz, 1H), 8.07 – 7.98 (m, 2H), 7.76 (ddd, J =
13.9.
2-(4-(tert-butyl)phenyl)-1H-indole (2j).21 Compound 2j was 7.9 Hz, 1H), 7.48 (dd, J = 8.1, 0.8 Hz, 1H), 7.22 (d, J = 1.4 Hz, 1H),
prepared according to the general procedure
7.17 (ddd, J = 8.1, 7.1, 1.1 Hz, 1H), 7.06 (td, J = 7.5, 0.9 Hz, 1H).13
8.4, 6.9, 1.4 Hz, 1H), 7.66 (ddd, J = 8.0, 6.9, 1.1 Hz, 1H), 7.61 (d, J =
A
C
(petroleum ether/ethyl acetate = 50:1 v/v). The product was NMR (125 MHz, DMSO) δ 148.5, 146.6, 137.5, 134.7, 129.8, 129.3,
1
obtained as a white solid in 64% yield. H NMR (500 MHz, CDCl3) δ 128.8, 128.6, 128.1, 127.6, 127.4, 125.5, 122.3, 120.4, 119.7, 111.5,
8.34 (s, 1H), 7.65 – 7.60 (m, 3H), 7.48 (d, J = 8.5 Hz, 2H), 7.41 (d, J = 100.5.
8.1 Hz, 1H), 7.22 – 7.18 (m, 1H), 7.13 (dd, J = 10.9, 3.8 Hz, 1H), 6.81
(d, J = 1.4 Hz, 1H), 1.38 (s, 9H). 13C NMR (125 MHz, CDCl3) δ 150.9, according to the general procedure
138.0, 136.7, 129.6, 129.4, 126.0, 124.9, 122.1, 120.6, 120.2, 110.9, acetate = 50:1 v/v). The product was obtained as a yellow solid in
2-(thiophen-2-yl)-1H-indole (2q).26 Compound 2q was prepared
(petroleum ether/ethyl
A
1
99.5, 34.7, 31.3.
56% yield. H NMR (500 MHz, CDCl3) δ 8.24 (s, 1H), 7.61 (d, J = 7.9
2-(m-tolyl)-1H-indole (2k).22 Compound 2k was prepared Hz, 1H), 7.37 (dd, J = 8.1, 0.7 Hz, 1H), 7.31 – 7.26 (m, 2H), 7.23 –
according to the general procedure
A (petroleum ether/ethyl 7.19 (m, 1H), 7.16 – 7.12 (m, 1H), 7.10 (dd, J = 5.0, 3.6 Hz, 1H), 6.80
acetate = 50:1 v/v). The product was obtained as a white solid in – 6.67 (m, 1H). 13C NMR (125 MHz, CDCl3) δ 136.5, 135.6, 132.4,
1
77% yield. H NMR (500 MHz, CDCl3) δ 8.35 (s, 1H), 7.64 (d, J = 7.8 129.1, 128.0, 124.6, 122.9, 122.6, 120.6, 120.5, 110.8, 100.4.
Hz, 1H), 7.52 – 7.46 (m, 2H), 7.40 (d, J = 8.1 Hz, 1H), 7.34 (t, J = 7.6
6-methyl-2-phenyl-1H-indole (2r).18 Compound 2r was prepared
Hz, 1H), 7.17 (ddd, J = 23.9, 11.5, 7.1 Hz, 3H), 6.83 (d, J = 2.0 Hz, 1H), according to the general procedure
A (petroleum ether/ethyl
2.44 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 138.7, 138.0, 136.8, 132.3, acetate = 50:1 v/v). The product was obtained as a white solid in
1
129.3, 128.9, 128.5, 125.9, 122.3, 122.2, 120.6, 120.2, 110.9, 99.9, 48% yield. H NMR (500 MHz, CDCl3) δ 8.21 (s, 1H), 7.68 – 7.61 (m,
21.6.
2-(3-fluorophenyl)-1H-indole (2l).18 Compound 2l was prepared 7.19 (d, J = 0.5 Hz, 1H), 6.98 (dd, J = 8.0, 0.9 Hz, 1H), 6.80 (dd, J =
according to the general procedure
(petroleum ether/ethyl 2.1, 0.8 Hz, 1H), 2.49 (s, 3H). 13C NMR (125 MHz, CDCl3) δ 137.3,
2H), 7.53 (d, J = 8.0 Hz, 1H), 7.47 – 7.40 (m, 2H), 7.34 – 7.29 (m, 1H),
A
acetate = 50:1 v/v). The product was obtained as a white solid in 137.2, 132.6, 132.3, 129.0, 127.5, 127.1, 125.0, 122.1, 120.3, 110.9,
1
61% yield. H NMR (500 MHz, CDCl3) δ 8.27 (s, 1H), 7.67 (d, J = 7.9 99.8, 21.9.
Hz, 1H), 7.46 – 7.37 (m, 3H), 7.36 – 7.31 (m, 1H), 7.24 (dd, J = 8.1,
6-fluoro-2-phenyl-1H-indole (2s).27 Compound 2s was prepared
1.1 Hz, 1H), 7.19 – 7.15 (m, 1H), 7.06 – 7.00 (m, 1H), 6.90 – 6.81 (m, according to the general procedure
A (petroleum ether/ethyl
1H). 13C NMR (125 MHz, CDCl3) δ 163.3 (d, J = 244.5 Hz), 136.9, acetate = 50:1 v/v). The product was obtained as a white solid in
1
136.6 (d, J = 2.6 Hz), 134.6 (d, J = 8.2 Hz), 130.6 (d, J = 8.6 Hz), 129.1, 64% yield. H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.63 (d, J = 7.5
122.9, 120.9, 120.7 (d, J = 2.8 Hz), 120.5, 114.5 (d, J = 21.1 Hz), Hz, 2H), 7.54 (dd, J = 8.1, 5.5 Hz, 1H), 7.45 (t, J = 7.4 Hz, 2H), 7.34 (t,
112.0 (d, J = 22.6 Hz), 111.1, 100.9.
2-(3-chlorophenyl)-1H-indole (2m).23 Compound 2m was (s, 1H). 13C NMR (125 MHz, CDCl3) δ 161.0 (d, J = 236.6 Hz), 138.4,
prepared according to the general procedure 136.7 (d, J = 12.4 Hz), 132.1, 129.1, 127.8, 125.8, 125.0, 121.4 (d, J =
(petroleum ether/ethyl acetate = 50:1 v/v). The product was 10.0 Hz), 109.1 (d, J = 24.3 Hz), 99.9, 97.3 (d, J = 25.9 Hz).
J = 7.2 Hz, 1H), 7.09 (d, J = 9.2 Hz, 1H), 6.91 (t, J = 8.5 Hz, 1H), 6.80
A
1
obtained as a white solid in 66% yield. H NMR (500 MHz, CDCl3) δ
8.31 (s, 1H), 7.68 – 7.60 (m, 2H), 7.56 – 7.49 (m, 1H), 7.43 – 7.33 (m, according to the general procedure
6-chloro-2-phenyl-1H-indole (2t).27 Compound 2t was prepared
(petroleum ether/ethyl
A
2H), 7.29 (ddd, J = 8.0, 2.0, 1.0 Hz, 1H), 7.23 (ddd, J = 8.2, 7.1, 1.1 acetate = 50:1 v/v). The product was obtained as a white solid in
1
Hz, 1H), 7.15 (td, J = 7.6, 0.9 Hz, 1H), 6.85 (dd, J = 2.1, 0.8 Hz, 1H). 44% yield. H NMR (500 MHz, CDCl3) δ 8.34 (s, 1H), 7.65 (d, J = 7.5
13C NMR (125 MHz, CDCl3) δ 137.0, 136.3, 135.0, 134.2, 130.3, Hz, 2H), 7.53 (d, J = 8.4 Hz, 1H), 7.45 (t, J = 7.7 Hz, 2H), 7.36 (dd, J =
129.1, 127.6, 125.2, 123.2, 122.9, 120.9, 120.5, 111.0, 101.0.
18.0, 10.6 Hz, 2H), 7.09 (dd, J = 8.4, 1.5 Hz, 1H), 6.80 (d, J = 0.9 Hz,
2-(naphthalen-1-yl)-1H-indole (2n).23 Compound 2n was 1H). 13C NMR (125 MHz, CDCl3) δ 138.6, 137.1, 131.9, 129.1, 128.0,
prepared
according
to
the
general
procedure
A
127.8, 125.2, 121.5, 121.0, 110.8, 100.0, 99.9.
(petroleum ether/ethyl acetate = 50:1 v/v). The product was
obtained as a yellow solid in 74% yield. H NMR (500 MHz, CDCl3) δ according to the general procedure
5-fluoro-2-phenyl-1H-indole (2u).18 Compound 2u was prepared
1
A (petroleum ether/ethyl
8.33 (dd, J = 8.1, 1.3 Hz, 2H), 7.97 – 7.85 (m, 2H), 7.72 (d, J = 7.8 Hz, acetate = 50:1 v/v). The product was obtained as a white solid in
1
1H), 7.65 (dd, J = 7.1, 1.1 Hz, 1H), 7.58 – 7.50 (m, 3H), 7.46 (dd, J = 83% yield. H NMR (500 MHz, CDCl3) δ 8.32 (s, 1H), 7.69 – 7.63 (m,
8.1, 0.7 Hz, 1H), 7.26 (dd, J = 15.2, 1.2 Hz, 1H), 7.22 – 7.16 (m, 1H), 2H), 7.46 (t, J = 7.7 Hz, 2H), 7.38 – 7.26 (m, 3H), 6.95 (td, J = 9.1, 2.5
6.82 (dd, J = 2.0, 0.7 Hz, 1H).13C NMR (125 MHz, CDCl3) δ 136.7, Hz, 1H), 6.79 (d, J = 1.5 Hz, 1H). 13C NMR (125 MHz, CDCl3) δ 158.2
136.4, 133.9, 131.5, 131.1, 128.9, 128.6, 128.5, 127.2, 126.7, 126.2, (d, J = 233.3 Hz), 139.7, 133.3, 132.0, 129.6 (d, J = 10.4 Hz), 129.1,
125.7, 125.4, 122.2, 120.6, 120.2, 110.9, 103.7.
2-(naphthalen-2-yl)-1H-indole (2o).24 Compound 2o was 23.3 Hz), 100.1 (d, J = 4.7 Hz).
prepared according to the general procedure
128.0, 125.2, 111.5 (d, J = 9.7 Hz), 110.6 (d, J = 26.3 Hz), 105.4 (d, J =
A
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DOI: 10.1039/C7OB01918A
ARTICLE
Journal Name
4
5
(a) G. Fabriz and S. Cacchi, Chem. Rev., 2005, 105, 2873; (b) B.
A. Haag, Z.-G. Zhang, J.-S. Li and P. Knochel, Angew. Chem.,
2009, 121, 9786; Angew. Chem. Int. Ed., 2010, 49 , 9513; (c) S.
6-methyl-2-(p-tolyl)-1H-indole (2v). Compound 2v was prepared
according to the general procedure (petroleum ether/ethyl
A
acetate = 50:1 v/v). The product was obtained as a white solid in
1
Müller, M. J. Webber and B. List, J. Am. Chem. Soc., 2011,
66% yield. H NMR (500 MHz, CDCl3) δ 8.18 (s, 1H), 7.56 – 7.50 (m,
133, 18534; (d) M. Inman, A. Carbone and C. J. Moody, J. Org.
Chem., 2012, 77, 1217.
(a) N. Sakai, K. Annaka, A. Fujita, A. Sato and T. Konakahara,
3H), 7.25 (d, J = 7.9 Hz, 2H), 7.17 (s, 1H), 6.97 (d, J = 8.0 Hz, 1H), 6.77
– 6.73 (m, 1H), 2.49 (s, 3H), 2.41 (s, 3H). 13C NMR (125 MHz, CDCl3)
δ 137.5, 137.4, 137.2, 132.0, 129.8, 129.7, 127.2, 124.9, 122.0,
120.2, 110.8, 99.2, 21.8, 21.3. HRMS (ESI, m/z): calculated for
C16H15N [M+H]+: 222.1277; found: 222.1282.
Org. Lett., 2004, 6, 1527; J. Org. Chem., 2008, 73, 4160; (b) K.
Hirano, Y. Inaba, K. Takasu, S. Oishi, Y. Takemoto, N. Fujii and
H. Ohno, J. Org. Chem., 2011, 76, 9068; (c) E. Kumaran and
W. K. Leong, Tetrahedron Lett., 2014, 55, 5495; (d) A.
(E)-2-styrylpyridin-3-amine (2w').28 Compound 2w' was
Gimeno, A. Rodr
í
Arellano, M. Medio-Sim
guez-Gimeno, A. B. Cuenca, C. R. de
n and G. Asensio, Chem. Commun.,
prepared
according
to
the
general
procedure
A
ó
(petroleum ether/ethyl acetate = 50:1 v/v). The product was
obtained as a yellow solid in 33% yield. H NMR (500 MHz, CDCl3) δ
1
2015, 51, 12384; (e) Y. Kitazawa, R. Takita, K. Yoshida, A.
Muranaka, S. Matsubara and M. Uchiyama, J. Org. Chem.,
2017, 82, 1931.
Y. Yamane, X. Liu, A. Hamasaki, T. Ishida, M. Haruta, T.
Yokoyama and M. Tokunaga, Org. Lett., 2009, 11, 5162.
K. Yang, F. Zhou, Z. Kuang, G. Gao, T. G. Driver and Q. Song,
Org. Lett., 2016, 18, 4088.
8.11 (dd, J = 3.6, 2.4 Hz, 1H), 7.66 (d, J = 15.7 Hz, 1H), 7.57 (d, J = 7.4
Hz, 2H), 7.37 (dd, J = 10.4, 4.7 Hz, 2H), 7.31 – 7.26 (m, 1H), 7.20 (d, J
= 15.7 Hz, 1H), 7.03 – 6.99 (m, 2H), 3.82 (s, 2H). 13C NMR (126 MHz,
CDCl3) δ 141.6, 140.4, 140.0, 137.1, 133.1, 128.7, 128.1, 127.0,
123.4, 123.0, 122.0.
6
7
8
2-cyclopropyl-1H-indole (2x).29 Compound 2x was prepared
according to the general procedure
(a) S. T. Staben, J. J. Kennedy-Smith, and F. D. Toste, Angew.
Chem. Int. Ed., 2004, 43, 5350; (b) G. Seidel, R. Mynott and A.
A (petroleum ether/ethyl
acetate = 100:1 v/v). The product was obtained as a colorless oil in
36% yield. H NMR (500 MHz, CDCl3) δ 7.86 (s, 1H), 7.57 (d, J = 5.8
F
ü
rstner, Angew. Chem. Int. Ed., 2009, 48, 2510; (c) S. Fl
ü
ügge,
A. Anoop, R. Goddard, W. Thiel and A. F rstner, Chem. Eur. J.,
1
2009, 15, 8558; (d) T. N. Hooper, M. Green and C. A. Russell,
Chem. Commun., 2010, 46, 2313; (e) T. J. Brown and R. A.
Widenhoefer, J. Organomet. Chem., 2011, 696, 1216; (f) B.
Lu, Y. Luo, L. Liu, L. Ye, Y, Wang and L. Zhang, Angew. Chem.
Int. Ed., 2011, 50, 8358; (g) A. Das, C. Dash, M. Yousufuddin,
M. A. Celik, G. Frenking and H. V. R. Dias, Angew. Chem. Int.
Ed., 2012, 51, 3940; (h) O. S. Morozov, A. V. Lunchev, A. A.
Bush, A. A. Tukov, A. F. Asachenko, V. N. Khrustalev, S. S.
Zalesskiy, V. P. Ananikov and M. S. Nechaev, Chem. Eur. J.,
2014, 20, 6162; (i) R. E. M. Brooner and R. A. Widenhoefer,
Angew. Chem. Int. Ed., 2013, 52, 11714; (j) R. Dorel and A. M.
Echavarren, Chem. Rev., 2015, 115, 9028.
Hz, 1H), 7.29 (d, J = 7.9 Hz, 1H), 7.20 – 7.10 (m, 2H), 6.21 (s, 1H),
2.00 – 1.93 (m, 1H), 1.01 (d, J = 7.2 Hz, 2H), 0.82 (s, 2H). 13C NMR
(125 MHz, CDCl3) δ 141.8, 135.8, 128.8, 121.0, 119.8, 119.7, 110.3,
97.7, 8.9, 7.4.
Acknowledgements
Financial support from the Recruitment Program of Global
Experts (1000 Talents Plan), the Natural Science Foundation of
Fujian Province (2016J01064), Fujian Hundred Talents Plan,
Program of Innovative Research Team of Huaqiao University
(Z14X0047) and Subsidized Project for Cultivating
Postgraduates’Innovative Ability in Scientific Research of
Huaqiao University (for W. Fu) are gratefully acknowledged.
We also thank the Instrumental Analysis Center of Huaqiao
University for analysis support.
9
K. Okuma, J. Seto, K. Sakaguchi, S. Ozaki, N. Nagahora and K.
Shioji, Tetrahedron Lett., 2009, 50, 2943.
10 A. Yasuhara, A. Kasano, and T. Sakamoto, J. Org. Chem., 1999,
64, 2301.
11 J. S. Kim, J. H. Han, J. J. Lee, Y. M. Jun, B. M. Lee and B. H. Kim,
Tetrahedron Lett., 2008, 49, 3733.
12 E. C. Neeve, S. J. Geier, I. A. I. Mkhalid, S. A. Westcott and T.
B. Marder, Chem. Rev., 2016, 116, 9091.
13 (a) W. Ding and Q. Song, Org. Chem. Front., 2016,
Xuan and Q. Song, Org. Lett., 2016, 18, 4250.
3, 14; (b) Q.
Competing financial interests
14 (a) H. P. Kokatla, P. F. Thomson, S. Bae, V. R. Doddi, and M. K.
Lakshman, J. Org. Chem., 2011, 76, 7842; (b) H. Lu, Z. Geng, J.
Li, D. Zou, Y. Wu and Y. Wu, Org. Lett., 2016, 18, 2774.
The authors declare no competing financial interests.
15 (a) Q. Feng, K. Yang and Q. Song, Chem. Commun., 2015, 51
,
Notes and references
15394; (b) S. Nave, R. P. Sonawane, T. G. Elford and V. K.
Aggarwal, J. Am. Chem. Soc., 2010, 132, 17096.
16 M. J. Hesse, C. P. Butts, C. L. Willis and V. K. Aggarwal, Angew.
Chem. Int. Ed., 2012, 51, 12444.
17 O. S. Morozov, A. V. Lunchev, A. A. Bush, A. A. Tukov, A. F.
Asachenko, V. N. Khrustalev, S. S. Zalesskiy, V. P. Ananikov
and M. S. Nechaev, Chem. Eur. J., 2014, 20, 6162.
18 M. Shen, B. E. Leslie and T. G. Driver, Angew. Chem. Int. Ed.,
2008, 47, 5056.
19 E. Eichhorn, M. Winkler, A. Sellmer, U. Möllmann and S.
Mahboobi, Eur. J. Med. Chem., 2008, 43, 633.
20 K. Saito, Y. Shibata, M. Yamanaka, and T. Akiyama, J. Am.
Chem. Soc., 2013, 135, 11740.
21 P. R.-Marqués, M. A. R.-Crespo, A. L.-Pérez and A. Corma, J.
Am. Chem. Soc., 2015, 137, 11832.
22 S. Yu, L. Qi, K. Hu, J. Gong, T. Cheng, Q. Wang, J. Chen and H.
Wu, J. Org. Chem., 2017, 82, 3631.
1
(a) X. Yu, E.-J. Park, T. P. Kondratyuk, J. M. Pezzuto and D.
Sun, Org. Biomol. Chem., 2012, 10, 8835; (b) N. K. Kaushik, N.
Kaushik, P. Attri, N. Kumar, C. H. Kim, A. K. Verma and E. H.
Choi, Molecules., 2013, 18, 6620.
2
3
(a) M. Lv and H Xu, Cur. Pharm. Des., 2009, 15, 2120; (b) S.
Lal and T. J. SnapeDfge, Cur. Med. Chem., 2012, 19, 4828.
(a) M. Piqu
é
rez, M. Pr
, M. González, I. Buira, E. Méndez, J. Terencio, C.
íncep, A. Palomer, A. Guglietta and J. L. Falcó,
Pé
Eur. J. Med. Chem., 2006, 41, 985; (b) U. Jacquemard, N. Dias,
A. Lansiaux, C. Bailly, C. Logé, J.-M. Robert, O. Lozach, L.
Meijer, J.-Y. Mérour and S. Routier, Bioorg. Med. Chem.,
2008, 16, 4932; (c) R. K. Chang, J. M.-C. Wai, C. N. D. Marco,
V. Cofre, R. M. DiPardo, S. P. Cook, M. J. Cato, A. Jovanovska,
M.O. Urban, M. Leitl, R. H. Spencer, S. A. Kane, G. D.
Hartman, M. T. Bilodeau and S. D. Kuduk, Bioorg. Med. Chem.
Lett., 2009, 19, 4059.
6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C7OB01918A
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ARTICLE
23 L. Joucla, N. Batail and L.Djakovitch, Adv. Synth. Catal., 2010,
352, 2929.
24 J. Zhao, Y. Zhang and K. Cheng, J. Org. Chem., 2008, 73, 7428.
25 S.Cacchi, G. Fabrizi and L. M. Parisi, Org. Lett., 2003, 5, 3843.
26 K. Yang, F. Zhou, Z. Kuang, G. Gao, T. G. Driver and Q. Song,
Org. Lett., 2016, 18, 4088.
27 F. Zhou, D.-S. Wang and T. G. Driver, Adv. Synth. Catal., 2015,
357, 3463.
28 S. Ortgies and A. Breder, Org. Lett., 2015, 17, 2748.
29 Y. Wang, L. Ye and L. Zhang, Chem. Commun., 2011, 47, 7815.
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