Aerobic C–C Bond Cleavage of Indoles by Visible-Light Photoredox Catalysis with Ru(bpy)32+

Article abstract of DOI:10.1002/ejoc.201701245

Photoredox catalysis with Ru(bpy)₃²⁺ (2,2′-bipyridine) has been used to enable the activation of oxygen in the aerobic C–C cleavage/oxygenation reaction of indoles. A number of indole substrates that contain various functional groups were successfully employed in the reaction to give a wide range of ortho-aminobenzaldehyde derivatives. These products can then be used as versatile building blocks for further synthetic modifications. Mechanistic studies suggest that the reaction proceeds through a radical pathway.

Full text of DOI:10.1002/ejoc.201701245

A Journal of
Accepted Article
Title: Aerobic C-C cleavage of indoles by visible light photoredox
catalysis with Ru(bpy)32+
Authors: Xiaochen Ji, Dongdong Li, Zhongzhen Wang, Muyun Tan,
Huawen Huang, and Guojun Deng
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201701245
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10.1002/ejoc.201701245
European Journal of Organic Chemistry
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Aerobic C–C Cleavage of Indoles by Visible Light Photoredox
2+
Catalysis with Ru(bpy)3
Xiaochen Ji,[a]* Dongdong Li,[a] Zhongzhen Wang,[a] Muyun Tan,[a] Huawen Huang,[a]* and Guo-Jun
Deng[a],[b]
2+
Abstract: Photoredox catalysis with Ru(bpy)3 enables oxygen
activation, which is applied to C–C cleavage/oxygenation reaction of
indoles. A number of indoles bearing functional groups work
smoothly to give a diverse of aromatic carbonyls, which are
demonstrated to be versatile building blocks for further diversification
to give broader range of functionalized molecules. Mechanistic
studies suggest a radical pathway of the reaction procedure.
C-H bond, and arylboronic acids with molecular oxygen was
successfully achieved under photocatalysis at room temperature.
Indole is a privileged structure that is frequently found as key
unit in pharmaceutical agents and naturally occurring products.[7]
Meanwhile, indoles are usually used as versatile building blocks
in synthetic methodologies, providing conscious access to a
diverse range of functional indoles, indole-fused heterocycles,
and among others.[8] In the field of aerobic functionalization of
indoles,[9,10] previously we developed palladium-catalyzed C3
arylation of indoles using cyclohexanones as aryl source under
oxygen atmosphere, where the aerobic dehydrogenation with
oxygen afforded the aryl moiety (Scheme 1a).[10d] Based on this
work, we subsequently designed an indole-to-carbazole cascade
strategy with the three-component annulation of indoles, ketones,
and electron-withdrawing alkenes, and analogously oxygen
Introduction
In the past decade, visible light-induced organic transformation
attracted intensive attention among synthetic chemistry.[1] As the
most commonly employed visible light photocatalysts, ruthenium
polypyridyl complexes represent bench stable, benign catalysts,
which function with broad utility to achieve bond-forming
reactions.[2] Importantly, these species via excitation of an
electron afford excited states which are found to be very
effective single-electron-transfer reagents. Typically, the
complex tris(2,2’-bipyridine)ruthenium(II), or Ru(bpy)32+, absorbs
visible light at 452 nm to give stable photoexcited states with
long lifetime (τ = 1100 nm), which allow it capable to engage in a
large number of organic electron-transfer reactions. As visible
light photocatalysts, Ru(bpy)32+ and related complexes has been
extensively investigated for applications in inorganic and
materials chemistry.[3]
played
a role of dehydrogenative aromatization for this
transformation (Scheme 1b).[10e] Very recently, copper-catalyzed
aerobic oxygenation/cyclization of indoles was disclosed with
oxygen as both oxygenation source and oxidant (Scheme 1c).[10f]
Herein, we apply photocatalysis as a powerful tool to realize
aerobic functionalization of indoles (Scheme 1d). In this protocol,
C–C bond cleavage of indoles is induced under oxygen
atmosphere by visible blue LED light combined with ruthenium
photoredox catalyst, affording 2-aminoarylcarbonyls in an atom-
economic fashion.
To the end of green and sustainable chemistry,[4] the aerobic
transformation with molecular oxygen as an ideal oxidant and
oxygenating reagents has attracted intensive attention during
the past decades.[5] Recently, the ingenious oxygen-involved
photocatalysis has been found to be a powerful tool to achieve
desired oxidative process.[6] Most importantly, energy-transfer
and electron-transfer readily occur between photocatalyst and
substrates, which thereby enable the activation of dioxygen to
form highly active singlet oxygen 1O2 or superoxide radical anion
under mild reaction conditions. For instance, oxygenating
functionalization of carbonyls, unsaturated hydrocarbons, benzyl
our previous work:
O
R
[Pd], ligand, O2
R2
(a)
+
- H2O
R2
N
R1
R
N
R1
R4
R3
O
a) condensation
R4
O
b) oxidation,
R2
2
R3
(b)
(c)
(d)
+
R2
N
R1
- H2O
EWG
EWG
N
R1
O
[Cu], O2
R1
[a]
Dr. X. Ji, D. Li, Z. Wang, M. Tan, Dr. H. Huang and Prof. G.-J. Deng
Key Laboratory of Environmentally Friendly Chemistry and
Application of Ministry of Education, College of Chemistry
Xiangtan University
R2
NOAc
R1
R2
+
N
R3
N
H
- H2O, - HOAc
N
R3
Xiangtan 411105, China.
this work:
E-mail: xcji@xtu.edu.cn; hwhuang@xtu.edu.cn
hxxy.web.xtu.edu.cn:8081/teacher.aspx?id=173
Prof. G.-J. Deng
R3
O
N
R3
visible light, O2
R2
R4
R4
[b]
O
N
R1
Beijing National Laboratory for Molecular Sciences and CAS Key
Laboratory of Molecular Recognition and Function Institute of
Chemistry
atom economy
mild conditions
gram-scalable
R2
R1
Chinese Academy of Sciences (CAS)
Beijing 100190 (P.R. China)
Scheme 1. Aerobic functionalization of indoles with dioxygen.
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/ejoc.201701245
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Results and Discussion
13
14
15
16
17
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
H2O (30) THF
trace
30
H2O (30) DMF
H2O (30) DMSO
H2O (30) DCE
We commenced our studies on the optimization of reaction
conditions by utilizing N-methylindole 1a as the model substrate,
combined with Ru(bpy)3Cl2·6H2O as the photocatalyst and blue
LED light source in acetonitrile media (Table 1). Trace amount of
2-aminobenzaldehyde 2a via oxidative C–C cleavage was
observed when the reaction was performed under oxygen
atmosphere (entry 1). Then a series of bases were screened,
and among them both phosphates and carbonates could
promote the oxidative C–C cleavage (entries 2–4), whereas
potassium tert-butoxide was found ineffective (entry 5). With
K3PO4·3H2O as the base, the addition of water further enhanced
the desired transformation (entries 6–9) and 30 equiv was found
to be optimal, which afforded the target product 2a in 85% yield.
This might be attributed to the dramatically increased solubility
of the inorganic base with water as cosolvent. When other
photocatalysts such as Ir(ppy)3, Rose Bengal, and Eosin Y were
employed, inferior results were obtained (entries 10–12). Then
the reaction was performed in other media (entries 13–17).
Among them, while polar DMF and DMSO decreased the yield
to 30% and 10%, respectively, THF, DCE, and toluene gave
trace amount of 2a. This would be attributed to the very poor
solubility of the catalyst and base in these solvents. Notably, the
reaction performed under air atmosphere generated the product
in moderate yield (entry 18). In comparison, 2-
aminobenzaldehyde was not formed under nitrogen atmosphere
(entry 19). Control experiments were conducted in the absence
of photocatalyst or without light stimulation, where in both cases
no desired product could be observed (entries 20–21). Finally,
when using 26 W CFL instead of 5W blue LED as the light
source, the yield of 2a dramatically decreased to 26% (entry 22).
10
trace
trace
55
H2O (30) toluene
H2O (30) CH3CN
H2O (30) CH3CN
H2O (30) CH3CN
H2O (30) CH3CN
H2O (30) CH3CN
18[c] Ru(bpy)3Cl2·6H2O K3PO4·3H2O
19[d] Ru(bpy)3Cl2·6H2O K3PO4·3H2O
0
20
K3PO4·3H2O
0
21[e] Ru(bpy)3Cl2·6H2O K3PO4·3H2O
22[f] Ru(bpy)3Cl2·6H2O K3PO4·3H2O
0
26
[a] reaction conditions: 1a (0.3 mmol), catalyst (3 mol%), base (0.5 equiv),
additive, solvent (0.1 M), O2 balloon, rt, 72 h. [b] isolated yield. [c] Under
air. [d] Under N2. [e] In dark. [f] 26 W CFL instead of 5 W blue LED.
With the optimized reaction conditions in hand, we turned
our attention to the scope of the aerobic C–C bond cleavage
of indoles (Scheme 2). Initially a range of N-substituted
indoles were tested for this visible light-triggered aerobic
oxidation. Indoles bearing ethyl (1b), benzyl (1c), allyl (1e),
and propargyl functionalities (1f) were all compatible with this
transformation,
affording
the
corresponding
2-
aminobenzaldehyde products in moderate to good yields.
Notably, silicon functionality (SEM) was also tolerated in the
present catalytic system (2d). Unfortunately, N-H indole and
N-Ts indole were found to be ineffective substrates for the
aerobic C–C bond cleavage. Then the reactions worked
smoothly with a large array of N-methylindoles bearing a C5
substituent. A number of functional groups, including methyl
(2g), methoxyl (2h), benzyl phenol ether (2i), aryl halides
(2j–2m), nitrile (2n), and arylaldehyde (2o) were compatible
with this transformation. While 1,4-dimethylindole 1p
afforded product 2p in excellent yield, 1,7-dimethylindole 1q
gave modest yield of the corresponding product. Ester group
at C6 position of N-methylindole was tolerated, giving product
2r in 66% yield. Notably, indoles bearing alkynyl and alkyenyl
groups were accommodated, generating 2s and 2t in 58%
and 64% yield, respectively. Then, we found that 1,3-
dimethylindole 1u worked smoothly to give 2-
aminoacetophenone 2u in 73% yield. Furthermore, 1,2-
disubstituted indoles proceeded well to afford the respected
amides in modest yields with methyl, phenyl, and ester
functionalities tolerated (2v–2x). Intriguingly, in the present
system the aerobic C–C bond cleavage of 1-methyl-7-
azaindole 1y also occurred, albeit in a lower yield.
Table 1. Optimization of the reaction conditions.[a]
Entry Catalyst
Base
additive
Solvent
Yield
(%)[b]
1
Ru(bpy)3Cl2·6H2O
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
trace
22
2
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K2HPO4·3H2O
Ru(bpy)3Cl2·6H2O K2CO3
3
15
4
21
5
Ru(bpy)3Cl2·6H2O tBuOK
trace
41
6
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
Ru(bpy)3Cl2·6H2O K3PO4·3H2O
H2O (10) CH3CN
H2O (20) CH3CN
H2O (30) CH3CN
H2O (40) CH3CN
H2O (30) CH3CN
H2O (30) CH3CN
H2O (30) CH3CN
7
70
8
85
9
60
10
11
12
Ir(ppy)3
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
trace
43
Rose Bengal
Eosin Y
14
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10.1002/ejoc.201701245
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Scheme 2. Scope of reaction.
Scheme 3. Control experiments.
To lighten the reaction mechanism of the visible light-triggered
C–C cleavage of indoles, a series of control experiments were
carried out (Scheme 3). First, 1-methylindoline-2,3-dione,
frequently observed as a byproduct, was proved not to be the
intermediate product because it could not transfer into the 2-
aminobenzaldehyde 2a under the standard reaction conditions.
The addition of a radical scavenger such as BHT and TEMPO
dramatically reduced the yield of the transformation, which
indicated a radical pathway of the present reaction. Furthermore,
when the singlet oxygen quencher (DABCO)[11] was added to the
reaction, the yield of 3a was also decreased to 15%. With
respect to the oxygen source of the product, 18O-labeled
dioxygen was used independently with 1-methylindole 1a, 1,3-
dimethylindole 1u, and 1,2-dimethyl indole 1v. The HRMS
analysis of the products revealed that products with one 18O
atom were the major products in all cases. While doubly labeled
products were observed, nonlabeled form was generated
probably through H/D exchange between the 18O-labled
products and water.[12]
The oxidative cleavage of indoles is a light-dependent
reaction, which can be demonstrated by the light-switch
experiment of the model reaction. As shown in Figure 1, the
yield of the model reaction was not enhanced when the reaction
mixture was stirred in dark. Thereby, the novelty of the
collaboration of photocatalysis and oxygen activation was
reflected again.
Figure 1. Light-control experiment.
Mechanistically, aerobic C-C bond cleavage[6j-l] and
indole oxidation[9] under photocatalysis with visible light
have been well investigated. Based on our experimental
results and previous reports,
mechanism was proposed (Scheme 4). First, indole 1a is
oxidized to indole radical cation by the activated
[Ru(bpy)3]2+*, which is in situ generated through light
a
possible reaction
A
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10.1002/ejoc.201701245
European Journal of Organic Chemistry
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oC, 2 h; then NaBH4 (2.0 equiv), MeOH, rt, 12 h. (e) KOH (2.0 equiv), H2O, 0
oC, 2 h; then hydroxylamine hydrochloride (3.0 equiv), KOH (6.0 equiv),
MeOH-H2O (4:1), 60 oC, 2 h. (f) KOH (1 equiv), CH3CN, rt, 12 h.
inducement to photocatalyst. In the meantime, reductive
species [Ru(bpy)3]+ was afforded, which reduces dioxygen
to superoxide ion O2
(B
) and transfers to [Ru(bpy)3]2+ itself.
•−
Then, radical-radical cross coupling occurs to deliver
superoxide intermediate , followed by intramolecular
nucleophilic addition to give dioxetane intermediate . Our
C
Conclusions
D
isotope labeling studies indicate that the final product 2a is
formed probably through path a together with path b.[13]
In summary, we have developed the visible light photoredox
catalysis with inexpensive Ru(bpy)3 for the aerobic C–C bond
2+
cleavage of indoles. By this protocol, efficient synthesis of ortho-
aminobenzaldehydes was achieved with broad functional group
tolerance. Compared with previous works, the present catalytic
system used much less base and enabled the aerobic
oxygenation in gram-scale. The versatile resultant products were
further diversified by synthetic modification with simple treatment.
Experimental Section
General methods. All reactions were carried out under the standard
conditions unless otherwise noted. Column chromatography was
performed using silica gel (200-300 mesh). 1H NMR and 13C NMR
spectra were recorded on a 400 MHz NMR spectrometer, and the
chemical shifts are referenced to signals at 7.26 and 77.0 ppm,
respectively. Generally, chloroform was used as the solvent with TMS as
the internal standard. HRMS was carried out on a high-resolution mass
spectrometer (LCMS-IT-TOF). The structure of known compounds was
Scheme 4. Possible reaction mechanism.
Significantly, an efficient gram-scale synthesis of 2a (1.37
g, 84%) was achieved to demonstrate the robust nature of
the mild photocatalysis at room temperature (Scheme 5a).
The incorporation of two carbonyl groups in the product 2a
allows it for further synthetic modification through simple
treatment. For example, hydrolysis of the formamide moiety
afforded 2-amino-benzaldehyde 3a in 99% yield (Scheme
5b), and the reduction of 2a gave benzyl alcohol 3b and 3c
in good yields (Scheme 5c-d). Moreover, the condensation
of 3a with hydroxylamine generated oxime 3d in excellent
yield (Scheme 5e). Finally, the formation of 4-quinolone 3e
through base-promoted Camps cyclization at room
temperature was achieved in excellent yield (Scheme 5f).
1
further corroborated by comparing their H NMR, 13C NMR data and MS
data with those in literature. Melting points were measured with a melting
point instrument and were uncorrected. All reagents were obtained from
commercial suppliers and used without further purification.
General procedure for the aerobic C–C bond cleavage of indoles.
Indole 1 (0.3 mmol, 1.0 equiv), K3PO4·3H2O (0.15 mmol, 0.5 equiv),
Ru(bpy)3Cl2·6 H2O (3 mol%), H2O (30 equiv) and acetonitrile (3.0 mL)
were added into a 15 mL tube successively. The reaction mixture was
stirred at room temperature under the irradiation by a 5W blue LED with
an oxygen balloon. The reaction was monitored by TLC. After completion,
the solvent was removed in vacuo, and the residue was separated by
column chromatography on silica gel (petroleum ether/EtOAc 2:1 to 1:1)
to give the pure product 2.
General procedure for the aerobic C–C bond cleavage of indole in
gram-scale reaction. 1-Methyl-1H-indole 1a (10 mmol, 1.0 equiv),
K3PO4·3H2O (5 mmol, 0.5 equiv), Ru(bpy)3Cl2·6 H2O (3 mol%), H2O (30
equiv) and acetonitrile (30 mL) were added into a 100 mL round bottom
flask successively. The reaction mixture was stirred for 96 h at room
temperature under the irradiation by a 7W blue LED with an oxygen
balloon. After completion, the solvent was removed in vacuo, and the
residue was separated by column chromatography on silica gel
(petroleum ether/ethyl acetate 2:1 to 1:1) to give the pure product 2a
(1.37 g, 84%).
N-(2-Formylphenyl)-N-methylformamide (2a).[9a] 2a was obtained in
85% yield (41.6 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 10.06
(s, 1.0H), 9.95 (s, 0.2H), 8.36 (s, 0.2H), 8.21 (s, 1.0H), 7.95-7.91 (m,
1.2H), 7.70-7.64 (m, 1.2H), 7.51 (t, J = 7.4 Hz, 1.0H), 7.47 (t, J = 7.6 Hz,
0.2H), 7.28 (d, J = 8.4 Hz, 1.0H), 7.26 (d, J = 9.2 Hz, 0.2H), 3.39 (s,
0.6H), 3.31 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 189.2, 189.0,
163.0, 162.7, 143.3, 141.2, 135.3, 135.1, 131.6, 130.9, 130.4, 130.4,
128.4, 128.0, 127.7, 127.3, 37.8, 34.5.
N-Ethyl-N-(2-formylphenyl)formamide (2b). 2b was obtained in 75%
yield (39.9 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 10.11 (s,
1.0H), 10.00 (s, 0.3H), 8.42 (s, 0.3 H), 8.19 (s, 1.0H), 8.00-7.96 (m, 1.3H),
7.72-7.67 (m, 1.3H), 7.56-7.49 (m, 1.3H), 7.31-7.25 (m, 1.3H), 3.88 (q, J
= 7.2 Hz, 2.0H), 3.79 (q, J = 7.2 Hz, 0.6H), 1.20 (t, J = 7.2 Hz, 1.0H), 1.15
(t, J = 7.2 Hz, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 189.4, 189.1, 162.7,
162.3, 142.2, 139.9, 135.2, 135.0, 132.7, 132.5, 130.5, 130.2, 128.9,
128.6, 128.5, 128.4, 45.8, 42.2, 14.8, 12.5. HRMS (ESI) m/z calcd for
C10H12NO2+ (M+H)+ 178.08626, found 178.08627.
Scheme 5. Diversification of the resultant products. Reaction conditions: (a)
Standard reaction conditions with 7 W blue LED. (b) KOH (2.0 equiv), H2O, 0
oC, 2 h. (c) NaBH4 (1.0 equiv), MeOH, 0 oC, 12 h. (d) KOH (2.0 equiv), H2O, 0
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N-Benzyl-N-(2-formylphenyl)formamide (2c).[9a] 2c was obtained in
66% yield (47.4 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 9.77 (s,
1.2H), 8.64 (s, 0.2H), 8.27 (s, 1.0H), 7.90 (td, J = 7.6, 1.6 Hz, 1.2H), 7.63-
7.56 (m, 1.2H), 7.51-7.46 (m, 1.2H), 7.31-7.28 (m, 1.2H), 7.26-7.23 (m,
2.4H), 7.19-7.06 (m, 3.6H), 4.98 (s, 2 H), 4.83 (s, 0.4H); 13C NMR (100
MHz, CDCl3): δ = 189.1, 189.0, 162.8, 162.2, 141.8, 135.3, 135.1, 135.0,
134.8, 132.7, 130.4, 130.3, 129.1, 129.0, 128.9, 128.7, 128.7, 128.5,
128.5, 128.4, 128.4, 128.0, 55.1, 50.7. HRMS (ESI) m/z calcd for
C15H14NO2+ (M+H)+ 240.10191, found 240.10178.
N-(2-Formylphenyl)-N-{[2-(trimethylsilyl)ethoxy]methyl}formamide
(2d). 2d was obtained in 50% yield (41.9 mg) as yellow oil. 1H NMR (400
MHz, CDCl3): δ = 10.10 (s, 1.0H), 9.99 (s, 0.9H), 8.51 (s, 0.9H), 8.30 (s,
1.0H), 7.98-7.94 (m, 1.9H), 7.71-7.66 (m, 1.9H), 7.54 (q, J = 8.4 Hz,
1.9H), 7.40 (d, J = 7.6 Hz, 1.0H), 7.33 (d, J = 8.0 Hz, 0.9H), 5.14 (s,
2.0H), 5.00 (s, 1.8H), 3.68 (t, J = 8.4 Hz, 2.0H), 3.58 (t, J = 8.2 Hz, 1.8H),
0.92 (t, J = 8.4 Hz, 3.8H), -0.01 (s, 17.1H); 13C NMR (100 MHz, CDCl3): δ
= 189.8, 189.7, 163.3, 163.0, 141.6, 139.6, 135.2, 135.0, 132.7, 132.3,
131.1, 130.6, 129.3, 128.9, 128.9, 128.8, 80.6, 75.1, 67.2, 66.1, 18.1,
17.9, -1.4. HRMS (ESI) m/z calcd for C14H22NO3Si+ (M+H)+ 280.13635,
found 280.13647.
(400 MHz, CDCl3): δ = 10.05 (d, J = 2.8 Hz, 1H), 9.93 (d, J = 2.4 Hz,
0.25H), 8.40 (s, 0.25H), 8.23 (s, 1.0H), 7.68-7.63 (m, 1.25H), 7.43-7.38
(m, 1.25H), 7.34-7.27 (m, 1.25H), 3.42 (s, 0.75H), 3.34 (s, 3.0H); 13C
NMR (100 MHz, CDCl3): δ = 187.8, 187.6, 163.0, 162.5, 160.6, 139.7,
137.5, 133.7, 133.5, 130.1, 129.3, 122.4, 122.1, 116.5, 116.2, 116.0,
37.9, 34.8. HRMS (ESI) m/z calcd for C9H9FNO2 (M+H)+ 182.06118,
+
found 182.06093.
N-(4-Chloro-2-formylphenyl)-N-methylformamide (2k).[9a] 2k was
obtained in 70% yield (41.5 mg) as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.03 (s, 1.0H), 9.90 (s, 0.25H), 8.37 (s, 0.25H), 8.22 (s, 1.0H), 7.93
(d, J = 2.8 Hz, 1.0H), 7.91 (d, J = 2.4 Hz, 0.25H), 7.66-7.62 (m, 1.25H),
7.26 (t, J = 4.2 Hz, 1H), 7.23 (d, J = 8.8 Hz, 0.25H), 3.41 (s, 0.75H), 3.33
(s, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 187.7, 187.6, 162.9, 162.4,
141.9, 139.6, 135.2, 134.9, 134.7, 134.5, 132.9, 132.8, 130.3, 129.9,
129.1, 128.6, 37.7, 34.6. HRMS (ESI) m/z calcd for C9H9ClNO2 (M+H)+
+
198.03163, found 198.03165.
N-(4-Bromo-2-formylphenyl)-N-methylformamide (2l).[9a] 2l was
obtained in 69% yield (49.9 mg) as yellow solid, M.p. 44~48 oC. 1H NMR
(400 MHz, CDCl3): δ = 10.02 (s, 1.0H), 9.89 (s, 0.25H), 8.37 (s, 0.25H),
8.22 (s, 1.0H), 8.09 (d, J = 2.4 Hz, 1.0H), 8.06 (d, J = 2.4 Hz, 0.25H),
7.82-7.78 (m, 1.25H), 7.19 (d, J = 8.4 Hz, 1.0H), 7.16 (d, J = 8.4 Hz,
0.25H), 3.41 (s, 0.75H), 3.33 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ =
187.6, 187.5, 162.9, 162.4, 142.4, 140.1, 138.1, 137.8, 133.5, 133.1,
133.0, 132.9, 129.3, 128.8, 122.3, 122.3, 37.6, 34.6. HRMS (ESI) m/z
calcd for C9H9BrNO2+ (M+H)+ 241.98112, found 241.98109.
N-Allyl-N-(2-formylphenyl)formamide (2e). 2e was obtained in 72%
yield (40.8 mg) as colorless oil. 1H NMR (400 MHz, CDCl3): δ = 10.08 (s,
1.0H), 9.98 (s, 0.3H), 8.43 (s, 0.3H), 8.22 (s, 1.0H), 7.97-7.93 (m, 1.3H),
7.70-7.64 (m, 1.3H), 7.54-7.47 (m, 1.3H), 7.31 (d, J = 7.6 Hz, 1H), 7.25 (d,
J = 9.2 Hz, 0.3H), 5.86-5.76 (m, 1.3H), 5.21-5.11 (m, 2.6H), 4.40 (d, J =
6.4 Hz, 2H), 4.30 (d, J = 6.4 Hz, 0.6H); 13C NMR (100 MHz, CDCl3): δ =
189.3, 189.2, 162.9, 162.1, 141.8, 140.0, 135.0, 134.8, 132.3, 132.2,
132.0, 131.2, 130.7, 130.1, 128.7, 128.5, 128.3, 128.1, 120.0, 119.5,
N-(2-Formyl-4-iodophenyl)-N-methylformamide
(2m).
2m
was
obtained in 38% yield (32.9 mg) as yellow solid, M.p. 87~89 oC. 1H NMR
(400 MHz, CDCl3): δ = 9.99 (s, 1.0H), 9.86 (s, 0.3H), 8.36 (s, 0.3H), 8.27
(d, J = 2.0 Hz, 1.0H), 8.25 (d, J = 2.0 Hz, 0.3H), 8.21 (s, 1.0H), 7.99 (dd,
J = 8.4, 2.0 Hz, 1.3H), 7.06-7.01 (m, 1.3H), 3.40 (s, 0.9H), 3.33 (s, 3.0H);
13C NMR (100 MHz, CDCl3): δ = 187.9, 187.4, 163.5, 163.4, 155.3, 153.7,
152.7, 139.5, 137.0, 124.1, 122.5, 122.0, 34.9, 32.0. HRMS (ESI) m/z
calcd for C9H9INO2+ (M+H)+ 289.96725, found 289.96719.
53.5, 49.6. HRMS (ESI) m/z calcd for C11H12NO2 (M+H)+ 190.08626,
+
found 190.08617.
N-(2-Formylphenyl)-N-(prop-2-yn-1-yl)formamide (2f). 2f was obtained
in 49% yield (27.5 mg) as yellow solid, M.p. 69-72 oC. 1H NMR (400 MHz,
CDCl3): δ = 10.12 (s, 1.0H), 10.01 (s, 0.2H), 8.46 (s, 0.2H), 8.20 (s, 1H),
8.01-7.96 (m, 1.2H), 7.75-7.71 (m, 1.2H), 7.61-7.56 (m, 1.2H), 7.42 (d, J
= 8.0 Hz, 1H), 7.37 (d, J = 8.0 Hz, 0.2H), 4.59 (d, J = 2.0 Hz, 2.0H), 4.47
(d, J = 2.4 Hz, 0.4H), 2.37 (t, J = 2.4 Hz, 0.2H), 2.22 (t, J = 2.4 Hz, 1.0H);
13C NMR (100 MHz, CDCl3): δ = 189.6, 189.3, 162.6, 161.7, 140.6, 135.2,
135.1, 132.9, 132.4, 131.0, 130.7, 129.3, 129.2, 129.0, 128.8, 74.8, 73.6,
N-(4-Cyano-2-formylphenyl)-N-methylformamide
(2n).
2n
was
obtained in 55% yield (31.0 mg) as yellow solid, M.p. 85~87 oC. 1H NMR
(400 MHz, CDCl3): δ = 10.05 (s, 1.0H), 9.89 (s, 0.4H), 8.40 (s, 0.4H),
8.27 (s, 1.0H), 8.26 (d, J = 2.0 Hz, 1.0H), 8.22 (d, J = 2.0 Hz, 0.4H), 7.96-
7.93 (m, 1.4H), 7.46 (d, J = 8.4 Hz, 1.0H), 7.43 (d, J = 8.4 Hz, 0.4H), 3.49
(s, 1.2H), 3.40 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 186.9, 186.6,
162.9, 162.2, 146.7, 144.3, 137.8, 137.4, 135.0, 133.2, 132.1, 131.2,
127.4, 126.8, 117.1, 116.8, 111.9, 111.8, 37.0, 34.1. HRMS (ESI) m/z
calcd for C10H9N2O2+ (M+H)+ 189.06585, found 189.06525.
40.4, 35.8. HRMS (ESI) m/z calcd for C11H10NO2 (M+H)+ 188.07060,
+
found 188.07060.
N-(2-Formyl-4-methylphenyl)-N-methylformamide (2g).[9a] 2g was
obtained in 68% (36.1 mg) yield as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.04 (s, 1.0H), 9.93 (s, 0.2H), 8.35 (s, 0.2H), 8.19 (s, 1.0H), 7.74-
7.73 (m, 1.2H), 7.48 (dd, J = 8.0, 2.0 Hz, 1.2H), 7.18-7.13 (m, 1.2H), 3.37
(s, 0.6H), 3.29 (s, 3.0H), 2.43 (s, 3.0H), 2.41 (s, 0.6H); 13C NMR (100
MHz, CDCl3): δ = 189.5, 189.2, 163.0, 162.7, 141.1, 138.8, 138.7, 136.0,
N-(2,4-Diformylphenyl)-N-methylformamide (2o). 2o was obtained in
31% yield (17.8 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 10.11
(s, 1.0H), 10.09 (s, 1.0H), 10.08 (s, 0.3H), 9.97 (s, 0.3H), 8.45 (d, J = 2.0
Hz, 1.0H), 8.42 (d, J = 1.6 Hz, 0.3H), 8.41 (s, 0.3H), 8.30 (s, 1.0H), 8.21-
8.18 (m, 1.3H), 7.50-7.45 (m, 1.3H), 3.50 (s, 0.9H), 3.41 (s, 3.0H); 13C
NMR (100 MHz, CDCl3): δ = 190.1, 189.8, 187.8, 187.8, 162.8, 162.4,
148.0, 145.7, 135.5, 135.2, 134.5, 134.1, 133.4, 132.2, 132.0, 131.3,
135.8, 131.6, 131.4, 131.0, 130.9, 127.8, 127.4, 37.9, 34.6, 20.9, 20.8.
+
HRMS (ESI) m/z calcd for
178.08621.
C
10H12NO2 (M+H)+ 178.08626, found
127.3, 127.2, 37.2, 34.2. HRMS (ESI) m/z calcd for C10H10NO3 (M+H)+
+
N-(2-Formyl-4-methoxyphenyl)-N-methylformamide (2h). 2h was
obtained in 57% yield (33.0 mg) as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.04 (s, 1.0H), 9.94 (s, 0.2H), 8.38 (s, 0.2H), 8.20 (s, 1.0H), 7.43 (t,
J = 1.6 Hz, 1.2H), 7.21 (d, J = 1.6 Hz, 2.0H), 7.19 (d, J = 4.8 Hz, 0.4H),
3.88 (s, 3H), 3.87 (s, 0.6H), 3.38 (s, 0.6H). 3.30 (s, 3.0H); 13C NMR (100
MHz, CDCl3): δ = 189.0, 188.8, 163.2, 162.8, 159.4, 159.2, 136.8, 134.5,
133.0, 132.5, 129.5, 128.7, 122.2, 121.9, 113.1, 112.8, 55.8, 55.7, 38.2,
192.06552, found 192.06609.
N-(2-Formyl-3-methylphenyl)-N-methylformamide (2p). 2p was
obtained in 80% yield (42.5 mg) as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.24 (s, 1.0H), 10.20 (s, 0.2H), 8.31 (s, 0.2H), 8.20 (s, 1.0H), 7.54-
7.50 (m, 1.2H), 7.29 (d, J = 7.6 Hz, 1.0H), 7.25 (d, J = 7.6 Hz, 0.2H), 7.11
(d, J = 8.0 Hz, 1.0H), 7.09 (d, J = 8.0 Hz, 0.2H), 3.37 (s, 0.6H), 3.29 (s,
3.0H), 2.63 (s, 3.0H), 2.61 (s, 0.6H); 13C NMR (100 MHz, CDCl3): δ =
191.0, 190.8, 162.8, 162.7, 144.6, 142.3, 142.2, 141.6, 134.0, 133.9,
131.8, 131.6, 130.6, 130.4, 125.7, 125.3, 38.1, 34.8, 20.7, 20.4. HRMS
(ESI) m/z calcd for C10H12NO2+ (M+H)+ 178.08626, found 178.08623.
N-(2-Formyl-6-methylphenyl)-N-methylformamide (2q). 2q was
obtained in 59% yield (31.3 mg) as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.06 (d, J = 1.6 Hz, 1.0H), 10.00 (d, J = 2.0 Hz, 0.5H), 8.36 (s, 0.5H),
8.10 (s, 1.0H), 7.81 (d, J = 7.6 Hz, 1.0H), 7.77 (d, J = 8.0 Hz, 0.5H), 7.58
(t, J = 7.4 Hz, 1.5H), 7.49-7.42 (m, 1.5H), 3.27 (d, J = 0.8 Hz, 1.5H), 3.22
(d, J = 1.2 Hz, 3.0H), 2.30 (s, 3.0H), 2.26 (s, 1.5H); 13C NMR (100 MHz,
CDCl3): δ = 190.0, 189.6, 162.7, 162.7, 141.5, 139.6, 138.1, 138.0, 137.2,
34.9. HRMS (ESI) m/z calcd for C10H12NO3 (M+H)+ 194.08117, found
+
194.08090.
N-(4-[Benzyloxy]-2-formylphenyl)-N-methylformamide (2i). 2i was
obtained in 56% yield (45.2 mg) as yellow oil. 1H NMR (400 MHz, CDCl3):
δ = 10.04 (s, 1.0H), 9.93 (s, 0.2H), 8.38 (s, 0.2H), 8.20 (s, 1.0H), 7.52 (d,
J = 2.8 Hz, 1.2H), 7.45-7.35 (m, 6.0H), 7.29-7.26 (m, 1.2H), 7.22-7.19 (m,
1.2H), 5.14 (s, 2.0H), 5.12 (s, 0.4H), 3.38 (s, 0.6H), 3.30 (s, 3.0H); 13C
NMR (100 MHz, CDCl3): δ = 188.9, 188.7, 163.2, 162.8, 158.5, 158.4,
136.9, 135.9, 135.7, 134.6, 133.0, 132.6, 129.8, 129.6, 128.8, 128.7,
128.6, 128.3, 128.2, 127.5, 122.8, 122.5, 114.3, 114.0, 70.5, 70.4, 38.1,
34.9. HRMS (ESI) m/z calcd for C16H16NO3 (M+H)+ 270.11247, found
+
270.11243.
137.1, 133.6, 132.0, 129.8, 129.2, 128.8, 128.5, 36.8, 33.7, 17.1, 16.9.
N-(4-Fluoro-2-formylphenyl)-N-methylformamide (2j).[9a] 2j was
obtained in 56% yield (30.4 mg) as yellow solid, M.p. 74~77 oC. 1H NMR
HRMS (ESI) m/z calcd for
178.08623.
C
10H12NO2 (M+H)+ 178.08626, found
+
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201701245
European Journal of Organic Chemistry
FULL PAPER
Methyl 4-formyl-3-(N-methylformamido)benzoate (2r). 2r was
139.5, 138.9, 132.8, 129.2, 128.7, 93.2, 93.1, 37.5, 34.5. HRMS (ESI)
m/z calcd for C8H9N2O2+ (M+H)+ 165.06585, found 165.06595.
1
obtained in 66% yield (43.8 mg) as light yellow solid, M.p. 96~98 oC. H
NMR (400 MHz, CDCl3): δ = 9.98 (s, 1.0H), 9.86 (s, 0.25H), 8.37-8.21 (m,
2.5H), 7.99 (dd, J = 8.4, 2.0 Hz, 1.25H), 7.06-7.01 (m, 1.25H), 3.40 (s,
0.75H), 3.33 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 188.4, 188.4,
165.2, 165.0, 162.9, 162.5, 143.5, 141.1, 136.1, 135.8, 134.7, 134.4,
130.9, 130.1, 129.0, 129.0, 128.7, 128.1, 52.8, 52.7, 37.5, 34.5. HRMS
(ESI) m/z calcd for C11H12NO4+ (M+H)+ 222.07608, found 222.07597.
N-[2-Formyl-4-(phenylethynyl)phenyl]-N-methylformamide (2s). 2s
was obtained in 58% yield (45.8 mg) as yellow solid, M.p. 104~107 oC.
1H NMR (400 MHz, CDCl3): δ = 10.07 (s, 1.0H), 9.95 (s, 0.2H), 8.38 (s,
0.2H), 8.26 (s, 1.0H), 8.10 (d, J = 2.0 Hz, 1.0H), 8.08 (d, J = 2.0 Hz,
0.2H), 7.81-7.79 (m, 1.2H), 7.56-7.53 (m, 2.4H), 7.40-7.36 (m, 3.6H),
7.28 (d, J = 8.0 Hz, 1.2H), 3.42 (s, 0.6H), 3.35 (s, 3.0H); 13C NMR (100
MHz, CDCl3): δ = 188.5, 188.3, 162.9, 162.5, 142.6, 140.4, 137.6, 137.4,
134.2, 133.6, 131.7, 131.5, 129.0, 128.8, 128.5, 128.4, 127.6, 127.3,
124.0, 122.2, 92.0, 91.5, 87.2, 86.8, 37.6, 34.4. HRMS (ESI) m/z calcd
for C17H14NO2+ (M+H)+ 264.10191, found 264.10202.
2-(Methylamino)benzaldehyde (3a).[9a] 3a was obtained in 99% yield
(40.0 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 9.81 (s, 1.0H),
8.25 (s, 1.0H), 7.46 (dd, J = 7.6, 1.6 Hz, 1.0H), 7.41 (t, J = 8.4 Hz, 1.0H),
6.71-6.66 (m, 2.0H), 2.93 (d, J = 5.2 Hz, 3.0H); 13C NMR (100 MHz,
CDCl3): δ = 193.9, 151.5, 136.5, 135.8, 118.3, 114.7, 110.3, 29.0.
N-[2-(Hydroxymethyl)phenyl]-N-methylformamide (3b). 3b was
obtained in 70% yield (34.7 mg) as orange oil. 1H NMR (400 MHz,
DMSO-d6): δ = 8.20 (s, 0.3H),8.04 (s, 1.0H), 7.53-7.50 (m, 1.3H), 7.39-
7.29 (m, 2.6H), 7.24 (d, J = 7.6 Hz, 1.0H), 7.16 (d, J = 7.6 Hz, 0.3H), 5.26
(t, J = 5.4 Hz, 1.0H), 5.13 (t, J = 5.6 Hz, 0.3H), 4.39 (d, J = 5.2 Hz, 2.0H),
4.31 (d, J = 5.6 Hz, 0.6H), 3.19 (s, 0.9H), 3.07 (s, 3.0H); 13C NMR (100
MHz, DMSO-d6): δ = 163.1, 162.7, 140.1, 139.9, 139.7, 138.3, 129.5,
128.6, 128.5, 128.1, 128.1, 128.1, 128.0, 127.3, 59.6, 59.5, 37.6, 33.5.
HRMS (ESI) m/z calcd for C9H12NO2 (M+H)+ 166.08626, found
+
166.08629.
[2-(Methylamino)phenyl]methanol (3c).[15] 3c was obtained in 84%
yield (34.5 mg) as light green oil. 1H NMR (400 MHz, DMSO-d6): δ =
7.08-7.04 (m, 2.0H), 6.52 (t, J = 7.4 Hz, 1.0H), 6.47 (d, J = 8.0 Hz, 1.0H),
5.09 (d, J = 4.8 Hz, 1.0H), 5.03 (t, J = 5.4 Hz, 1.0H), 4.35 (d, J = 5.6 Hz,
2.0H), 2.68 (d, J = 5.2 Hz, 3.0H); 13C NMR (100 MHz, DMSO-d6): δ =
147.6, 128.2, 127.4, 125.8, 115.4, 109.0, 61.4, 30.0.
Methyl (E)-3-[3-formyl-4-(N-methylformamido)phenyl]acrylate (2t). 2t
was obtained in 64% yield (47.7 mg) as light yellow solid, M.p. 115~118
1
oC. H NMR (400 MHz, CDCl3): δ = 10.08 (s, 1.0H), 9.95 (s, 0.3H), 8.38
(s, 0.3H), 8.25 (s, 1.0H), 8.09-8.07 (m, 1.3H), 7.81 (dd, J = 8.2, 2.2 Hz,
1.3H), 7.70 (d, J = 16.0 Hz, 1.3H), 7.33 (d, J = 8.0 Hz, 1.3H), 6.52 (d, J =
16.0 Hz, 1.3H), 3.81 (s, 3.0H), 3.81 (s, 0.9H), 3.44 (s, 0.9H), 3.35 (s,
3.0H); 13C NMR (100 MHz, CDCl3): δ = 188.4, 188.4, 166.6, 162.9, 162.5,
144.5, 142.2, 141.8, 141.1, 136.2, 134.4, 134.0, 133.8, 132.0, 131.6,
(E)-2-(Methylamino)benzaldehyde oxime (3d).[16] 3d was obtained in
87% yield (39.2 mg) as yellow solid. 1H NMR (400 MHz, CDCl3): δ = 8.26
(s, 1.0H), 7.30-7.26 (m, 1.0H), 7.13 (dd, J = 7.6, 1.2 Hz, 1.0H), 7.01 (s,
130.1, 129.3, 127.8, 127.4, 126.9, 120.4, 120.1, 51.9, 51.9, 37.5, 34.4.
1.0H), 6.97 (s, 1.0H), 6.79-6.66 (m, 2.0H), 2.94 (d, J = 4.8 Hz, 3.0H); 13
C
+
HRMS (ESI) m/z calcd for
248.09171.
C
13H14NO4 (M+H)+ 248.09173, found
NMR (100 MHz, CDCl3): δ = 154.3, 148.2, 132.7, 130.9, 115.2, 114.0,
109.8, 29.7.
N-(2-Acetylphenyl)-N-methylformamide (2u). 2u was obtained in 73%
yield (38.8 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 8.12 (s,
0.3H), 8.10 (s, 1.0H), 7.69 (dd, J = 7.6, 1.6 Hz, 1.0H), 7.63 (dd, J = 7.8,
1.4 Hz, 0.3H), 7.57-7.50 (m, 1.3H), 7.43 (td, J = 7.6, 1.2 Hz, 1.0H), 7.37
(td, J = 7.6, 1.2 Hz, 0.3H), 7.23 (dd, J = 8.0, 0.8 Hz, 1.0H), 7.20 (dd, J =
7.8, 1.0 Hz, 0.3H), 3.34 (s, 0.9H), 3.23 (s, 3.0H), 2.53 (s, 0.9H), 2.48 (s,
3.0H); 13C NMR (100 MHz, CDCl3): δ = 200.1, 199.6, 162.6, 162.4, 139.9,
137.4, 137.3, 136.6, 132.7, 132.3, 129.8, 128.4, 128.0, 127.7, 127.4,
1-Methylquinolin-4(1H)-one (3e).[17] 3e was obtained in 90% yield (42.8
mg) as yellow solid. 1H NMR (400 MHz, DMSO-d6): δ = 8.17 (dd, J = 8.4,
1.6 Hz, 1H), 7.97 (d, J = 7.6 Hz, 1H), 7.77-7.76 (m, 1H), 7.65 (d, J = 8.8
Hz, 1H), 7.40 (t, J = 7.4 Hz, 1H), 6.03 (d, J = 7.6 Hz, 1H), 3.81 (s, 3H);
13C NMR (100 MHz, DMSO-d6): δ = 176.5, 145.1, 140.6, 132.1, 126.6,
125.6, 123.4, 116.7, 108.7, 40.1.
37.8, 33.8, 29.5, 28.6. HRMS (ESI) m/z calcd for C10H12NO2 (M+H)+
+
Acknowledgements
178.08626, found 178.08606.
N-(2-Formylphenyl)-N-methylacetamide (2v). 2v was obtained in 67%
yield (35.6 mg) as yellow oil. 1H NMR (400 MHz, CDCl3): δ = 10.1 (s,
1.0H), 10.1 (s, 0.1H), 7.98 (dd, J = 7.6, 1.6 Hz, 1.0H), 7.90 (dd, J = 7.6,
1.6 Hz, 0.1H), 7.70 (td, J = 7.6, 1.6 Hz, 1.0H), 7.65 (td, J = 7.6, 1.6 Hz,
0.1H), 7.54 (t, J = 7.6 Hz, 1.0H), 7.46 (t, J = 7.6 Hz, 0.1H), 7.29 (dd, J =
8.0, 0.8 Hz, 1.0H), 7.24 (d, J = 8.0 Hz, 0.1H), 3.40 (s, 0.3H), 3.30 (s,
3.0H), 2.31 (s, 0.3H), 1.81 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ =
189.4, 170.4, 146.2, 135.8, 132.5, 130.3, 129.2, 129.0, 37.9, 22.4. HRMS
(ESI) m/z calcd for C10H12NO2+ (M+H)+ 178.08626, found 178.08623.
N-(2-Formylphenyl)-N-methylbenzamide (2w).[14] 2w was obtained in
76% yield (54.5 mg) as colorless oil. 1H NMR (400 MHz, CDCl3): δ =
10.10 (s, 1.0H), 7.73 (d, J = 6.8 Hz, 1.0H), 7.52 (t, J = 6.6 Hz, 1.0H), 7.34
(t, J = 6.6 Hz, 1.0H), 7.20-7.10 (m, 6.0H), 3.50 (s, 3.0H); 13C NMR (100
MHz, CDCl3): δ = 189.1, 170.9, 146.3, 135.1, 135.0, 131.7, 130.6, 129.9,
This work was support by the National Natural Science
Foundation of China (21602187 and 21502161), the
Collaborative Innovation Center of New Chemical Technologies
for Environmental Benignity and Efficient Resource Utilization,
Scientific Research Fund of Hunan Provincial Education
Department (16B251), the China Postdoctoral Science
Foundation Funded Project (2015M580691), and Hunan
Provincial Natural Science Foundation of China (2017JJ3299).
Keywords: aerobic synthesis • C-C bond cleavage • indoles •
photoredox catalysis • ortho-aminobenzaldehydes
+
129.3, 128.4, 127.9, 127.8, 39.1. HRMS (ESI) m/z calcd for C15H14NO2
(M+H)+ 240.10191, found 240.10194.
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Methyl 2-[(2-formylphenyl)(methyl)amino]-2-oxoacetate (2x). 2x was
obtained in 52% yield (34.7 mg) as yellow solid, M.p. 87~90 oC. 1H NMR
(400 MHz, CDCl3): δ = 10.13 (s, 1.0H), 10.04 (s, 0.1H), 7.95 (dd, J = 7.6,
1.2 Hz, 1.1H), 7.66(td, J = 7.8, 1.5 Hz, 1.1H), 7.56 (t, J = 7.4 Hz, 1.1H),
7.30 (d, J = 8.0 Hz, 1.1H), 3.96 (s, 0.3H), 3.51 (s, 3.0H), 3.42 (s, 0.3H),
3.37 (s, 3.0H); 13C NMR (100 MHz, CDCl3): δ = 188.8, 161.9, 160.9,
142.4, 135.1, 132.5, 130.7, 129.6, 129.1, 52.3, 37.3. HRMS (ESI) m/z
calcd for C11H12NO4+ (M+H)+ 222.07608, found 222.07600.
N-(3-Formylpyridin-2-yl)-N-methylformamide (2y).[9a] 2y was obtained
in 33% yield (16.1 mg) as yellow solid, M.p. 96~99 oC. 1H NMR (400 MHz,
CDCl3): δ = 10.03 (s, 1.0H), 9.84 (s, 0.3H), 8.70 (dd, J = 4.8, 1.6 Hz,
1.0H), 8.67 (d, J = 4.4 Hz, 0.3H), 8.50 (s, 0.3H), 8.44 (s, 1.0H), 8.30-8.25
(m, 1.3H), 7.42-7.36 (m, 1.3H), 3.60 (s, 0.9H), 3.50 (s, 3.0H); 13C NMR
(100 MHz, CDCl3): δ = 187.6, 187.5, 162.8, 162.3, 144.0, 143.7, 143.0,
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10.1002/ejoc.201701245
European Journal of Organic Chemistry
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10.1002/ejoc.201701245
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
O
N
R3
CHO
NH
O
C–C cleavage
R3
R4
R2
R4
O
N
R1
Xiaochen Ji,* Dongdong Li, Zhongzhen
Wang, Muyun Tan, Huawen Huang,*,
Guo-Jun Deng
CH2OH
NCHO
N
R2
R1
O2
2+
Ru(bpy)3
visible light
versatile for
diversification
gram-scalable
atom-economic
mild conditions
Page No. – Page No.
Photoredox catalysis with Ru(bpy)32+ enables aerobic C–C cleavage/oxygenation
reaction of indoles.
Aerobic C–C cleavage of indoles by
visible light photoredox catalysis with
Ru(bpy)3
2+
*methodology
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