Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO

Article abstract of DOI:10.1016/j.tet.2016.11.009

A novel and simple strategy for the visible light-induced efficient synthesis of indol-3-yl aryl ketones from readily available arylsulfonyl chlorides and indoles with CO at room temperature was developed. This metal-free protocol has good functional group tolerance and avoids the use of transition-metal catalysts, additives, and alkaline or acidic reaction medium.

Full text of DOI:10.1016/j.tet.2016.11.009

Tetrahedron xxx (2016) 1e7
Contents lists available at ScienceDirect
Tetrahedron
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Visible light-induced carbonylation of indoles with arylsulfonyl
chlorides and CO
,
b
,
,
b
,
,
Xiangguang Li a *, Deqiang Liang a **, Wenzhong Huang a b, Hongfu Zhou a, Zhao Li a,
,
Baoling Wang a b, Yinhai Ma a, Hai Wang b
a Department of Chemical Science & Technology, Kunming University, Kunming 650214, China
b Key Laboratory of Yunnan Provincial Higher Education Institutions for Organic Optoelectronic Materials and Devices, Kunming University, Kunming
650214, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and simple strategy for the visible light-induced efficient synthesis of indol-3-yl aryl ketones
from readily available arylsulfonyl chlorides and indoles with CO at room temperature was developed.
This metal-free protocol has good functional group tolerance and avoids the use of transition-metal
catalysts, additives, and alkaline or acidic reaction medium.
Received 2 September 2016
Received in revised form
25 October 2016
Accepted 2 November 2016
Available online xxx
© 2016 Elsevier Ltd. All rights reserved.
Keywords:
Indol-3-yl aryl ketones
Carbonylation
Arylsulfonyl chlorides
Indoles
Visible light photocatalysis
1. Introduction
procedures of indol-3-yl aryl ketones mainly include Friedel-Crafts
reactions,3 Vilsmeier-Haack type reactions,4 and Grignard re-
The development of new and expedient synthetic strategies for
aromatic ketones from readily available starting materials has
gained considerable attention in organic chemistry for decades,
owing to the biological activity of aromatic ketones and their
widespread prevalence in natural products, functional materials
and pharmaceuticals.1 Among the reported techniques, metal-free
reactions are of great importance in the development of new
technologies for the synthesis of aromatic ketones. Particularly, as
an important class of nitrogen-containing heterocyclic aromatic
ketones, indol-3-yl aryl ketones are the common building blocks in
natural products, biological active compounds and pharmaceuti-
cals, and have showed excellent biological and pharmaceutical
activity.2 Consequently, the construction of indol-3-yl aryl ketones
has received increasing attention. The well-known synthetic
actions.5 Recently, some promising protocols involving transition-
metal-catalyzed acylation of CeH bonds for the synthesis of
indol-3-yl aryl ketones has been developed.6 However, most of
these reactions employ acids, bases or transition metals as the
catalysts. Given the fact that some functional groups are sensitive to
acids or bases, and the price of transition metal is generally high,
which makes these reactions limited in use.
Over the last several years, visible-light-induced organic trans-
formation has emerged as a powerful and promising tool, which
has become a new research hotspot due to its efficient synthesis
with safety and sustainability.7 However, most of the studies were
based on the use of transition metal (usually Ru and Ir) polypyridyl
complexes, which, under visible light irradiation, invoke a long-
lived charge transfer state and initiate a series of transformations
involving a single-electron transfer process with various functional
groups. Although there are many advantages for ruthenium and
iridium polypyridyl complexes in visible-light photocatalysis,
exorbitant price and environmental pollution limit their further
application in industrial processes. Besides, the strong coordinating
ability of CO and stability of carbonyl complexes of transition-metal
reduce the use of such organometallic catalysts in carbonylation
* Corresponding author. Department of Chemical Science & Technology, Kunming
University, Kunming 650214, China.
** Corresponding author. Key Laboratory of Yunnan Provincial Higher Education
Institutions for Organic Optoelectronic Materials and Devices, Kunming University,
Kunming 650214, China.
E-mail addresses: lixiangguang@iccas.ac.cn (X. Li), ldq5871@126.com (D. Liang).
http://dx.doi.org/10.1016/j.tet.2016.11.009
0040-4020/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Li X, et al., Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO, Tetrahedron
(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009

2
X. Li et al. / Tetrahedron xxx (2016) 1e7
Table 1
reaction. Organic dyes have been used as a viable alternative in
photoredox catalysis.8 Recently, Gu and co-workers reported their
study on visible-light-induced indol-3-yl aryl ketone synthesis
using aryl diazonium salts as a robust aryl radical source.9 Given the
wide availability of arylsulfonyl chlorides, some of them like p-
toluenesulfonyl chloride being industrially produced on ton scale,
this compound class appears to be attractive for the formation of
aryl radical precursors.10 Gu reported that arylsulfonyl chlorides
could generate aryl radicals with the aid of the excited state [Eosin
Y*].11 In the presence of a certain amount of CO, the intermediate
acyl radicals could be easily and efficiently created from aryl radi-
cals, then acyl radicals would be further oxidized to acylium ion by
the oxidized dye radical cation. We presumed that indoles might
serve as a good nucleophile to attack the acylium ion intermediate.
Herein, we describe our preliminary results on the development of
visible-light-mediated carbonylation of indoles and arylsulfonyl
chlorides for the synthesis of indol-3-yl aryl ketones under
transition-metal-free, base-free and acid-free conditions in carbon
monoxide atmosphere (Scheme 1).
Optimization of the reaction conditionsa.
Entry
Catalyst
Solvent
Yieldb (%)
1
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Fluorescein
Rhodamine B
Rose Bengal
Eosin Y
CH3CN
CH3CN
DMSO
THF
EtOAc
PhCF3
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
81
63
48
24
trace
trace
57
46
35
64
0
2c
3
4
5
6
7
8
9
10d
11
12e
none
Eosin Y
0
a
Reaction conditions: 1a (0.3 mmol), 2a (0.4 mmol), catalyst (2 mol%), solvent
2. Results and discussion
(3.0 mL), room temperature, CO (80 atm), 5 W green LED light for 8 h.
b
Isolated yields.
5 W white LED light.
CO (70 atm).
In the dark.
c
Initially, we focused our efforts on optimizing the reaction
conditions for the carbonylation reaction between benzenesulfonyl
chloride 1a and N-methylindole 2a. After a series of trials, treat-
ment of the benzenesulfonyl chloride 1a with 2a and Eosin Y under
irradiation with 5 W green LED light and a CO pressure of 80 atm in
MeCN at room temperature afforded the desired product 3aa in the
highest yield (Table 1, entry 1). Replacing 5 W green LED light with
5 W white LED light had a negative effect (Table 1, entry 2).
Screening of the solvents such as DMSO, THF, EtOAc and PhCF3,
revealed that they were less effective than MeCN (Table 1, entries
3e6 versus entry 1). A number of other organic dyes, including
Fluorescein, Rhodamine B and Rose Bengal, were subsequently
investigated, and they were found to be less effective than Eosin Y
(Table 1, entries 7e9 versus entry 1). Lower pressures of CO led to a
low conversion (Table 1, entry 10). Furthermore, it was found that
both visible-light photoredox catalysts and visible light are indis-
pensable for the reaction to take place (Table 1, entries 11e12).
With a set of optimized conditions in hand, we then investigated
the above visible-light photocatalysis protocol to a series of both
arylsulfonyl chlorides 1 and indoles 2 to extend the substrate scope.
We initially explored the scope of arylsulfonyl chlorides 1 in the
presence of substrate 2a, Eosin Y, CO, and 5 W green LED light. As
summarized in Table 2, the standard reaction conditions were
found to be compatible with a wide range of arylsulfonyl chlorides
1. The good tolerance of functional groups in the reaction makes
both electron-donating and -withdrawing arylsulfonyl chlorides
successfully converted to the corresponding products in moderate
to good yields (Table 2, entries 1e6). In addition, it was observed
that the efficiency of the reaction was not affected in the presence
d
e
of alkyl, ether, and halide groups, as well as the substituent at meta
position on the arene group (Table 2, entry 7). However, when using
the ortho-substituted arylsulfonyl chloride as the substrate, the
yield of corresponding product 3ai was decreased (Table 2, entry 8),
which suggested that the efficiency of the reactions was affected by
the steric effect. Notably, indol-3-yl naphthyl ketones 3aj could be
obtained directly in 51% yield by using the visible-light-induced
acylation process (Table 2, entry 9), which is high affinity binding
to the cannabinoid CB1 and CB2 receptors. It should be noted that
the metal-free protocol can introduce heterocycles into this system,
too, which makes this methodology more valuable for the prepa-
ration of pharmaceuticals and functional materials (Table 2, entry
10).
We then further investigated the substrate scope by reacting
benzenesulfonyl chloride 1a with different indoles. Apart from 2a,
1-ethyl-2-methyl-1H-indole 2b smoothly reacted with 1a, leading
to the corresponding product 3ba in 72% yield (Table 3, entry 1).
Application of substrates 2c and 2d with electron-withdrawing
groups, produced the desired products 3ca and 3da in a moder-
ate yields (Table 3, entries 2e3). N-Methylindoles bearing electron-
donating groups, such as methyl and methoxyl, reacted smoothly to
provide the corresponding substituted indol-3-yl phenyl ketones
3ea-3ga in moderate to good yields (Table 3, entries 4e6). In
addition, 1-methyl-1H-pyrrolo[2,3-b]pyridine 2h could deliver the
expected product 3ha in 51% yield (Table 3, entry 7). To our delight,
free NH-indoles 2i-2k could be smoothly converted to the expected
products in moderate yields (Table 3, entries 8e10).
To gain insights into the mechanism of the reaction, a series of
control experiments were conducted. It has been reported that the
reaction of arylsulfonyl chlorides with N-methylindoles can deliver
1-methyl-3-(arylsulfonyl)-1H-indoles,12 but when we investigated
our protocol in Tables 1e3, no sulfonylated product or related in-
termediates were found in our conditions. Recently Zheng have
developed a visible light mediated 3-sulfenylation of N-methyl-
indoles with arylsulfonyl chlorides.13 When 1-methyl-3-(phenyl-
thio)-1H-indole 4 was subjected to the reaction, no desired product
was obtained (Scheme 2, equation 1), which might exclude 4 as the
intermediate of this redox reaction. Addition of a radical-trapping
Scheme 1. Synthetic route to indol-3-yl aryl ketones via carbonylation process.
Please cite this article in press as: Li X, et al., Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO, Tetrahedron
(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009

X. Li et al. / Tetrahedron xxx (2016) 1e7
3
Table 2
Scope of arylsulfonyl chlorides 1a.
Entry
1
Arylsulfonyl chlorides 1
Products 3
Yieldb (%)
74
2
78
3
4
5
70
59
57
6
7
68
65
8
9
49
51
10
55
a
Reaction conditions: 1 (0.3 mmol), 2a (0.4 mmol), Eosin Y (2 mol%), MeCN (3.0 mL), room temperature, CO (80 atm), 5 W green LED light for 8 h.
Isolated yields.
b
reagent, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (1.0 equiv)
to the model reaction, no aryl ketone was obtained and the TEMPO
trapped intermediates 5 and 6 were detected (Scheme 2, equation
Based on the control experiments and previous reports,8,11 the
mechanism of this transformation was hypothesized as shown
in Scheme 3. Under visible-light irradiation, the photocatalyst
was excited, which resulted in the reduction of the phenyl-
sulfonyl chloride through a single-electron transfer process to
yield aryl radical A and the dye radical cation [Eosin Yþ$]. The
aryl radical A then trapped a CO molecule and delivered the acyl
radical B, which was further oxidized by [Eosin Yþ$] to yield
acylium C while [Eosin Yþ$] was reduced to the ground state to
complete the catalytic cycle. Finally, nucleophilic attack of the
2), indicating that the photoreaction proceeds via
a radical
pathway. Furthermore, when no photocatalyst was used and/or the
reaction was performed under dark conditions, the product yields
severely dropped. Even at increased temperature (up to 80 ꢀC) in
the dark, no desired product was formed, which means that ho-
molytic bond cleavage of the starting material to an aryl radical
under these conditions was excluded.
Please cite this article in press as: Li X, et al., Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO, Tetrahedron
(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009

4
X. Li et al. / Tetrahedron xxx (2016) 1e7
Table 3
Scope of indoles 2
for the increased usefulness of the reaction. In particular, this
a
.
carbonylation reaction uses the simple and readily available Eosin Y
as an efficient organic catalyst, rather than transition-metal com-
plexes. The transition-metal complexes involving additives, alka-
line or acidic reaction medium are often high cost with noble metal,
and are intractable to be completely removed from products,
especially in the pharmaceutical drug production. Further investi-
gation on the practical application of the reaction is underway.
b
Entry
1
Indoles 2
Products 3
Yield (%)
4. Experimental section
72
4.1. General materials and methods
Reagents were obtained commercially and used as received.
Solvents were purified and dried by standard methods. The sup-
plier of the autoclave irradiation set up is YanZheng Co. Ltd., China.
All title products were characterized by Infrared (IR), MS, 1H NMR,
13C NMR and High Resolution mass spectrometry (HRMS). IR
spectra were reported in frequency of the absorption (cmꢁ1). 1H
NMR and 13C NMR spectra were recorded in deuterated solvents
using a BRUKER AVANCE 400 (400 MHz) NMR Spectrometer. 1H
NMR spectra were recorded on 400 MHz in CDCl3 or DMSO-d6, and
13C NMR spectra were recorded on 100 MHz in CDCl3 or DMSO-d6
using tetramethylsilane (TMS) as an internal standard. Chemical
2
55
3
4
53
76
shift values (d) are given in ppm. Coupling constants (J) were
measured in Hz. GC-MS analyses were performed on a SHIMADZU
QP2010. High Resolution mass spectrometer (HRMS) spectra were
recorded on a Bruker micrOTOF-Q II analyzer. 200e300 mesh silica
gel was used for column chromatography.
5
57
4.2. General procedure for synthesis of indol-3-yl aryl ketones 3
6
7
67
51
To an 8 mL vial equipped with a magnetic stir bar was charged
with 1 (0.3 mmol), 2 (0.4 mmol), Eosin Y (2 mol%) and dry MeCN
(3.0 mL), The vial was purged with N2 in the dark and then trans-
ferred into an autoclave with a Quartz window bottom. After the
autoclave was flushed three times, 80 atm of CO was slowly filled.
The reaction was irradiated with external LEDs at room tempera-
ture for 8 h. After the reaction was finished, the gas was carefully
released and the vial retrieved, the reaction mixture was diluted
with 8 mL H2O, extracted with ethyl acetate (15 mL ꢂ 3). The ex-
tractions were washed with brine and then dried with Na2SO4.
After concentrated in vacuum, the resulting residue was purified by
column chromatography on silica gel (hexane/ethyl acetate ¼ 5:1 to
2:1) to give the desired products 3.
8
9
50
47
(1-Methyl-1H-indol-3-yl)(phenyl)methanone (3aa).14 Yield:
81%, 57.1 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.37e8.34 (m, 1H), 7.73
(d, J ¼ 6.8 Hz, 2H), 7.73e7.38 (m, 4H), 7.29 (dd, J ¼ 3.6 Hz, J ¼ 4.0 Hz,
3H), 3.78 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 190.9, 140.9, 137.9,
10
44
d
137.5, 131.1, 128.6, 128.3, 127.1, 123.6, 122.74, 122.73, 115.5, 109.6,
33.6, IR (neat cmꢁ1): 1657 (C]O); LRMS (EI 70 ev) m/z (%): 235 (Mþ,
100); HRMS m/z (ESI) calcd for C16H13NNaO (M þ Na)þ 258.0889,
found 258.0897.
a
Reaction conditions: 1a (0.3 mmol), 2 (0.4 mmol), Eosin Y (2 mol%), MeCN
(3.0 mL), room temperature, CO (80 atm), 5 W green LED light for 8 h.
b
Isolated yields.
(4-Methoxyphenyl)(1-methyl-1H-indol-3-yl)methanone
(3ab).14 Yield: 74%, 58.8 mg; 1H NMR (400 MHz, CDCl3)
d:
8.40e8.38 (m, 1H), 7.81 (d, J ¼ 8.4 Hz, 2H), 7.51 (s, 1H), 7.31e7.23 (m,
indole 2a to C generated the product 3aa.
3H), 6.97 (d, J ¼ 8.4 Hz, 2H), 3,88 (s, 3H), 3.81 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 189.3, 162.1, 137.2, 137.0, 133.2, 130.4, 127.3,
3. Conclusion
123.1, 122.2, 122.0, 115.2, 113.2, 109.6, 55.2, 33.4; IR (neat cmꢁ1):
1643 (C]O); LRMS (EI 70 ev) m/z (%): 265 (Mþ, 100); HRMS m/z
(ESI) calcd for C17H15NNaO2 (M þ Na)þ 288.0994, found 288.1002.
(1-Methyl-1H-indol-3-yl)(p-tolyl)methanone (3ac).14 Yield:
In conclusion, we have developed a novel and simple visible-
light-mediated carbonylation for the direct synthesis of indol-3-yl
aryl ketones from commercially available arylsulfonyl chlorides
and indoles. The utilization of inexpensive, readily available start-
ing materials and catalysts is significantly advantageous, allowing
78%, 58.3 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.43e8.41 (m, 1H), 7.76
(d, J ¼ 8.0 Hz, 2H), 7.50 (s, 1H), 7.37e7.34 (m, 3H), 7.30 (d, J ¼ 7.2 Hz,
2H), 3.84 (s, 3H), 2.43 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 190.5,
d
Please cite this article in press as: Li X, et al., Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO, Tetrahedron
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X. Li et al. / Tetrahedron xxx (2016) 1e7
5
(4-Chlorophenyl)(1-methyl-1H-indol-3-yl)methanone
(3ag).15 Yield: 68%, 54.9 mg; 1H NMR (400 MHz, CDCl3)
d
:
8.39e8.36 (m, 1H), 7.74 (d, J ¼ 8.4 Hz, 2H), 7.49 (s, 1H), 7.45 (d,
J ¼ 8.4 Hz, 2H), 7.35e7.32 (m, 3H), 3.86 (s, 3H); 189.1, 138.9, 137.6,
137.5, 137.1, 130.1, 128.5, 127.1, 123.6, 122.6, 122.3, 115.3, 109.8, 33.2;
IR (neat cm-1): 1664 (C]O); LRMS (EI 70 ev) m/z (%): 269 (Mþ,
100); HRMS m/z (ESI) calcd for C16H12ClNNaO (M þ Na)þ 292.0500,
found 292.0504.
(3-Chlorophenyl)(1-methyl-1H-indol-3-yl)methanone
(3ah).15 Yield: 65%, 52.4 mg; 1H NMR (400 MHz, CDCl3)
d: 8.42 (d,
J ¼ 5.6 Hz, 1H), 7.82 (t, J ¼ 6.6 Hz, 2H), 7.68 (d, J ¼ 7.6 Hz, 1H), 7.52 (t,
J ¼ 8.4 Hz, 2H), 7.43e7.37 (m, 3H), 3.85 (s, 3H); 13C NMR (100 MHz,
CDCl3) d:189.0, 142.4, 137.9, 137.5, 134.2, 130.9, 129.6, 128.6, 128.5,
126.7, 123.8, 122.9, 122.6, 115.1, 109.7, 33.6; IR (neat cm-1): 1655
(C]O); LRMS (EI 70 ev) m/z (%): 269 (Mþ, 100); HRMS m/z (ESI)
calcd for C16H12ClNNaO (M þ Na)þ 292.0500, found 292.0508.
(2-Chlorophenyl)(1-methyl-1H-indol-3-yl)methanone
Scheme 2. Control experiments.
(3ai).14 Yield: 49%, 39.5 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.37 (d,
J ¼ 5.6 Hz, 1H), 7.48e7.42 (m, 3H), 7.40e7.36 (m, 4H), 7.34e7.30 (m,
1H), 3.80 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 188.8, 140.5, 138.8,
141.4, 138.0, 137.5, 137.2, 128.7, 128.5, 127.1, 123.6, 122.6, 122.4, 115.5,
109.6, 33.2, 21.3; IR (neat cmꢁ1): 1649 (C]O); LRMS (EI 70 ev) m/z
(%): 249 (Mþ,100); HRMS m/z (ESI) calcd for C17H15NNaO (M þ Na)þ
272.1046, found 272.1041.
d
137.7, 130.9, 130.2, 130.0, 128.6, 126.44, 126.41, 123.8, 123.0, 122.6,
116.4, 109.7, 33.6; IR (neat cmꢁ1): 1649 (C]O); LRMS (EI 70 ev) m/z
(%): 269 (Mþ, 100); HRMS m/z (ESI) calcd for C16H12ClNNaO
(M þ Na)þ 292.0500, found 292.0508.
(4-Fluorophenyl)(1-methyl-1H-indol-3-yl)methanone
(3ad).15 Yield: 70%, 53.1 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.41 (d,
J ¼ 6.4 Hz, 1H), 7.88 (d, J ¼ 6.0 Hz, 2H), 7.49 (s, 1H), 7.36 (s, 3H),
7.16e7.12 (m, 2H), 3.84 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 189.2,
(1-Methyl-1H-indol-3-yl)(naphthalen-3-yl)methanone
(3aj).6b Yield: 51%, 43.6 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.42 (s,
1H), 8.21 (s, 1H), 7.87e7.84 (m, 4H), 7.51e7.47 (s, 3H), 7.30 (s, 3H),
3.74 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 190.5, 138.0, 137.9, 137.2,
d
165.6 (d, J ¼ 258.8 Hz),137.5 (d, J ¼ 1.4 Hz), 137.0 (d, J ¼ 3.1 Hz),131.1
(d, J ¼ 29.5 Hz), 127.1, 123.6, 122.7, 122.5, 115.2 (d, J ¼ 21.8 Hz), 109.7,
33.5; IR (neat cmꢁ1): 1659 (C]O); LRMS (EI 70 ev) m/z (%): 253
(Mþ, 100); HRMS m/z (ESI) calcd for C16H12FNNaO (M þ Na)þ
276.0795, found 276.0791.
d
134.6, 132.4, 129.1, 128.8, 128.1, 127.6, 127.0, 126.4, 125.4, 123.6,
122.5, 122.4, 115.5, 109.6, 33.5; IR (neat cmꢁ1): 1650 (C]O); LRMS
(EI 70 ev) m/z (%): 285 (Mþ, 100); HRMS m/z (ESI) calcd for
(1-Methyl-1H-indol-3-yl)(4-nitrophenyl)methanone (3ae).14
C
20H15NNaO (M þ Na)þ 308.1046, found 308.1050.
Yield: 59%, 49.6 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.41 (d,
J ¼ 6.4 Hz, 1H), 8.31 (d, J ¼ 8.0 Hz, 2H), 7.91 (d, J ¼ 8.0 Hz, 2H), 7.49
(s, 1H), 7.38 (s, 3H), 3.87 (s, 3H); 13C NMR (100 MHz, CDCl3)
: 188.3,
Benzofuran-2-yl(1-methyl-1H-indol-3-yl)methanone (3ak).
Yield: 55%, 45.4 mg; 1H NMR (400 MHz, CDCl3)
d: 8.58 (d, J ¼ 5.2 Hz,
d
1H), 8.46 (s, 1H), 7.73 (d, J ¼ 7.6 Hz, 1H), 7.63 (s, 2H), 7.46 (t,
J ¼ 7.6 Hz, 1H), 7.38e7.30 (m, 4H), 3.94 (s, 3H); 13C NMR (100 MHz,
149.2, 146.0, 138.2, 137.7, 129.4, 126.9, 124.2, 123.4, 123.0, 122.5,
115.3, 109.8, 33.2; IR (neat cmꢁ1): 1657 (C]O); LRMS (EI 70 ev) m/z
(%): 280 (Mþ, 100); HRMS m/z (ESI) calcd for C16H12N2NaO3
(M þ Na)þ 303.0673, found 303.0679.
CDCl3) d: 177.1, 155.3, 154.9, 137.9, 137.1, 127.5, 127.3, 127.1, 123.8,
123.6, 123.04, 123.00, 122.9, 114.4, 112.09, 112.02, 119.7, 33.8; IR
(neat cmꢁ1): 1648 (C]O); LRMS (EI 70 ev) m/z (%): 275 (Mþ, 100);
HRMS m/z (ESI) calcd for C18H13NNaO2 (M þ Na)þ 298.0838, found
298.0843.
(4-(Trifluoromethyl)phenyl)(1-methyl-1H-indol-3-yl)meth-
anone (3af).9 Yield: 57%, 51.8 mg; 1H NMR (400 MHz, CDCl3)
d: 8.42
(d, J ¼ 5.6 Hz, 1H), 7.90 (d, J ¼ 8.0 Hz, 2H), 7.76 (d, J ¼ 8.0 Hz, 2H),
(1-Ethyl-2-methyl-1H-indol-3-yl)(phenyl)methanone
7.49 (s, 1H), 7.39 (d, J ¼ 8.0 Hz, 3H), 3.86 (s, 3H); 13C NMR (100 MHz,
(3ba).16 Yield: 72%, 56.8 mg; 1H NMR (400 MHz, CDCl3)
d: 7.78 (d,
CDCl3)
d: 189.4, 144.0, 138.0, 137.6, 129.8, 129.7, 128.8, 128.55,
J ¼ 7.6 Hz, 2H), 7.57 (t, J ¼ 7.4 Hz, 1H),7.47 (t, J ¼ 7.6 Hz, 2H), 7.35 (dd,
128.52, 126.9, 126.89, 126.86, 125.37, 125.33, 124.0, 123.1, 122.7,
115.4, 109.7, 33.6; IR (neat cmꢁ1): 1666 (C]O); LRMS (EI 70 ev) m/z
(%): 303 (Mþ, 100); HRMS m/z (ESI) calcd for C17H12F3NNaO
(M þ Na)þ 326.0763, found 326.0771.
J ¼ 8.4 Hz, J ¼ 8.4 Hz, 2H), 7.23 (t, J ¼ 7.6 Hz, 1H), 7.09 (t, J ¼ 7.6 Hz,
1H), 4.24 (q, J ¼ 7.2 Hz, 2H), 2.61 (s, 3H), 1.43 (t, J ¼ 7.4 Hz, 3H); 13
C
NMR (100 MHz, CDCl3) d: 192.8, 143.8, 141.4, 135.3, 131.3, 128.9,
128.1, 127.2, 121.9, 121.2, 120.9, 113.6, 109.1, 37.9, 14.7, 12.1; IR (neat
cmꢁ1): 1662 (C]O); LRMS (EI 70 ev) m/z (%): 263 (Mþ, 100); HRMS
m/z (ESI) calcd for C18H17NNaO (M þ Na)þ 286.1203, found
286.1210.
(6-Fluoro-1-methyl-1H-indol-3-yl)(phenyl)methanone
(3ca).15 Yield: 55%, 41.7 mg; 1H NMR (400 MHz, CDCl3)
d: 8.41 (dd,
J ¼ 5.2 Hz, J ¼ 2.8 Hz, 1H), 7.83 (t, J ¼ 7.6 Hz, 2H), 7.58e7.47 (m, 4H),
7.13e7.08 (m, 1H), 7.06e7.02 (m, 1H), 3.78 (s, 3H); 13C NMR
(100 MHz, CDCl3) d: 190.5, 161.6, 159.2, 140.6, 138.16, 138.13, 137.8,
137.7, 131.3, 128.5, 128.1, 123.9, 123.8, 123.41, 123.40, 115.5, 111.3,
111.0, 96.5, 96.3, 33.5; IR (neat cmꢁ1): 1667 (C]O); LRMS (EI 70 ev)
m/z (%): 253 (Mþ, 100); HRMS m/z (ESI) calcd for C16H12FNNaO
(M þ Na)þ 276.0795, found 276.0799.
(6-Chloro-1-methyl-1H-indol-3-yl)(phenyl)methanone
(3da).6b Yield: 53%, 42.8 mg; 1H NMR (400 MHz, CDCl3)
d
: 8.33 (d,
J ¼ 8.4 Hz,1H), 7.79 (d, J ¼ 7.2 Hz, 2H), 7.53 (d, J ¼ 6.8 Hz,1H), 7.47 (s,
3H), 7.31e7.27 (m, 2H), 3.78 (s, 3H); 13C NMR (100 MHz, CDCl3)
190.4, 140.2, 138.0, 137.8, 131.2, 129.3, 128.5, 128.1, 125.4, 123.5,
d
:
Scheme 3. Plausible mechanism for synthesis of 3aa.
Please cite this article in press as: Li X, et al., Visible light-induced carbonylation of indoles with arylsulfonyl chlorides and CO, Tetrahedron
(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009

6
X. Li et al. / Tetrahedron xxx (2016) 1e7
123.1, 115.2, 109.6, 33.2; IR (neat cmꢁ1): 1671 (C]O); LRMS (EI 70
ev) m/z (%): 269 (Mþ, 71); HRMS m/z (ESI) calcd for C16H12ClNNaO
(M þ Na)þ 292.0500, found 292.0494.
Acknowledgement
We are grateful for the financial support from the National
Natural Science Foundation of China (21502077), the National
College Students Innovation Project (201500393002), the Applied
Basic Research Programs of Yunnan Science and Technology
Department (2015FD088), the General Projects of Yunnan Educa-
tion Department (2015Y396), the Research Foundation for Intro-
duced Talents (YJL14010), the Scientific Research Funds (XJL14013,
HHCX201501) of Kunming University, and the Innovation Team
Project of Kunming University (2015CXTD03).
(1,5-Dimethyl-1H-indol-3-yl)(phenyl)methanone
(3ea).17
d: 8.23 (s, 1H),
Yield: 76%, 56.8 mg; 1H NMR (400 MHz, CDCl3)
7.77 (d, J ¼ 6.4 Hz, 2H), 7.51 (d, J ¼ 7.6 Hz, 1H), 7.43 (t, J ¼ 6.4 Hz,
3H), 7.24e7.18 (m, 2H), 3.77 (s, 3H), 2.49 (s, 3H); 13C
NMR (100 MHz, CDCl3) d: 190.4, 140.3, 138.1, 135.7, 132.2, 130.6,
128.4, 128.0, 127.2, 125.2, 122.2, 114.5, 109.0, 33.1, 21.2; IR (neat
cmꢁ1): 1649 (C]O); LRMS (EI 70 ev) m/z (%): 249 (Mþ, 100);
HRMS m/z (ESI) calcd for C17H15NNaO (M þ Na)þ 272.1046, found
272.1053.
(4-Methoxy-1-methyl-1H-indol-3-yl)(phenyl)methanone
Appendix B. Supplementary data
(3fa).14 Yield: 57%, 45.3 mg; 1H NMR (400 MHz, CDCl3)
d: 7.79 (d,
Copies of 1H and 13C NMR spectra for all products. Supple-
mentary data associated with this article can be found in the online
version, at http://dx.doi.org/10.1016/j.tet.2016.11.009. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
J ¼ 7.6 Hz, 2H), 7.47 (t, J ¼ 7.4 Hz, 1H), 7.31e7.26 (m, 3H), 7.12 (t,
J ¼ 7.6 Hz, 1H), 6.81 (d, J ¼ 8.0 Hz, 1H), 6.63 (d, J ¼ 8.0 Hz, 1H), 3.72
(s, 3H), 3.63 (s, 3H); 13C NMR (100 MHz, CDCl3)
d: 191.0, 154.3,140.7,
139.1, 135.4, 131.3, 129.7, 127.4, 124.4, 116.6, 116.5, 102.8, 102.1, 55.4,
33.5; IR (neat cmꢁ1): 1649 (C]O); LRMS (EI 70 ev) m/z (%): 265
(Mþ, 100); HRMS m/z (ESI) calcd for C17H15NNaO2 (M þ Na)þ
288.0994, found 288.0999.
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: 8.27 (d,
Yield: 67%, 50.0 mg; 1H NMR (400 MHz, CDCl3)
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(1-Methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)(phenyl)meth-
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d:
8.65 (d, J ¼ 7.6 Hz, 1H), 8.44 (dd, J ¼ 4.8 Hz, J ¼ 0.4 Hz, 1H), 7.79 (d,
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148.0, 144.3, 139.7, 137.2, 131.4, 131.0, 128.6, 128.3, 119.4, 118.2, 113.6,
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d: 192.3, 145.0, 142.0, 135.4,
131.5, 128.8, 128.4, 127.7, 122.3, 121.4, 120.4, 112.9, 111.7, 14.6; IR
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(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009

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(2016), http://dx.doi.org/10.1016/j.tet.2016.11.009