An efficient Friedel-Crafts alkylation for the synthesis of 3-indolyl-3-hydroxy oxindoles and unsymmetrical 3,3-diaryl oxindoles catalyzed by Dabco-based ionic liquids in water

Article abstract of DOI:10.1039/c7nj00174f

A convenient and rapid method for the syntheses of 3-indolyl-3-hydroxy oxindoles and unsymmetrical 3,3-diaryl oxindoles has been developed by using Dabco-based ionic liquid catalysts. The two ionic liquid catalysts, [Dabco-H][BF₄] and [Dabco-H][HSO₄] were found to be highly efficient catalysts for controlled 3-indolylation of isatins in water. When [Dabco-H][BF₄] was employed as the catalyst in water at 55 °C, the reaction between isatins and indoles stops at the step of addition of the two components and afforded 3-indolyl-3-hydroxy oxindoles. While increasing the reaction temperature to 90 °C, the catalyst [Dabco-H][HSO₄] could drive the reaction further and afford symmetrical 3,3-diindolyl oxindoles. By using the two kinds of ionic liquids, a two-step protocol for the efficient synthesis of unsymmetrical 3,3-diaryl oxindoles has also been developed. The use of water as the reaction medium makes the process environmentally benign. The catalysts can be recycled five times without activity loss.

Full text of DOI:10.1039/c7nj00174f

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An efficient Friedel-Crafts alkylation for synthesis of 3-indolyl-3-hydroxy oxindoles and unsymmetrical
3
,3-diaryl oxindoles catalyzed by Dabco-base ionic liquids in water
Jun Tong, LuꢀShan Huang and DaꢀZhen Xu*
National Engineering Research Center of Pesticide (Tianjin), State Key Laboratory and Institute of
ElementoꢀOrganic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People’s Republic of
China
Fax: +86 22 2350 5948; Eꢀmail: xudazhen@nankai.edu.cn
Keywords
Ionic liquid, water, green chemistry, 3ꢀindolylꢀ3ꢀhydroxy oxindoles, 3,3ꢀdiaryl oxindoles
Abstract
A convenient and rapid method for syntheses of 3ꢀindolylꢀ3ꢀhydroxy oxindoles and unsymmetrical 3,3ꢀdiaryl
oxindoles has been developed by using Dabcoꢀbase ionic liquid catalysts. The two ionic liquids catalysts,
[
DabcoꢀH][BF
isatins in water. When [DabcoꢀH][BF
and indoles stops at the step of addition of the two components and provided 3ꢀindolylꢀ3ꢀhydroxy oxindoles.
While raising the reaction temperature to 90°C, the catalyst [DabcoꢀH][HSO ] could drive the reaction further and
4
] and [DabcoꢀH][HSO
4
] were found as highly efficient catalysts for controlled 3ꢀindolylation of
4
] was employed as the catalyst in water at 55°C, the reaction between isatin
4
afford symmetrical 3, 3ꢀdiindolyl oxindoles. By using the two kinds of ionic liquids, a twoꢀstep protocol for
efficient synthesis of unsymmetrical 3,3ꢀdiaryl oxindoles has been also developed. The use of water as the reaction
medium makes the process environmentally benign. The catalysts can be recycled five times without activity loss.
Introduction
Today, the concept of green chemistry has been deeply rooted in the people’s hearts. In organic synthesis,
increasing attention is being focused on using environmental friendly reagents and conditions. One of the key areas
of green chemistry is the elimination of solvents in chemical processes or the replacement of hazardous organic
[
1]
solvents with nonpolluting alternative reaction media, particularly aqueous media. Water is cheap, safe,
[
2ꢀ4]
nonꢀtoxic and readily available compared to organic solvent.
It has unique physical and chemical properties,
which may be utilized for attaining reactivity and selectivity that cannot be realized in common organic solvents.
So, to perform the organic reactions in water is one of the fundamental challenges and it has received considerable
[
5]
attention.
[
6]
Indoles and its derivatives are widespread in nature and have been identified as an important kind of compounds.
[7]
They often appeared a wide variety of pharmacologically and biological activities. In particular, C3
functionalised oxindoles are featured heterocyclic nuclei in a number of natural products as well as medicinally
[
8]
relevant kinds of compounds. Among them, the 3ꢀsubstituted 3ꢀhydroxy oxindoles and 3,3ꢀdiaryl oxindoles have
attracted much attention due to their broad spectrum of biological activities including antiviral, antibacterial,
antiꢀinflammatory, antiangiogenic, antifungal and anticonvulsant and they are also as new targets for cancer
[
9ꢀ13]
chemotherapy.
Moreover, both of their subclasses are useful building blocks as key intermediates in the total
[14]
synthesis of natural products. The synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles often involves a FriedelꢀCrafts
type of electrophilic substitution between the indoles and electronꢀdeficient carbonyl compounds such as isatins. A
[
15]
number of methods have been reported for synthesis of this kind compounds, but more examples usually results
[16]
in the formation of symmetrical 3,3ꢀdiindolyl oxindoles in a single step.
In sharp contrast, methods for the

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[17]
synthesis of unsymmetrical 3,3ꢀdiaryl oxindoles are rare,
especially base on the arylation of
[18]
3
ꢀindolylꢀ3ꢀhydroxy oxindoles. Even though, synthetic strategies for the two kinds compounds often suffer from
metal catalyst, expensive reagents, long reaction times, hazardous organic solvents and unrecyclable catalysts. In
view of the above, to control the reaction affording monoꢀsubstituted 3ꢀindolylꢀ3ꢀhydroxy oxindoles and which
further react with other aromatic nucleophiles to obtain unsymmetrical 3,3ꢀdiaryl oxindoles are quite challenging
and highly desirable.
Over the past decades, ionic liquids (ILs) have received much attention in academia and successfully applied in
many areas, including organic synthesis, electrochemistry, materials chemistry, and chemical separations. In
organic synthesis, there have been many reports describing the successful use of ILs as “green” solvents or
[19]
recovered catalysts.
Recently, we have reported a series of quaternary alkylammonium ILs based on the
skeleton of 1,4ꢀdiazobicyclo [2.2.2] octane (DABCO), and they are shown to be very effective catalysts for many
[20ꢀ25]
important reactions.
here, we wish to disclose our study on using the Dabcoꢀbase ILs as highly efficient catalysts in controlling
ꢀindolylation of isatins for syntheses of 3ꢀindolylꢀ3ꢀhydroxy oxindoles and unsymmetrical 3,3ꢀdiaryl oxindoles in
As a result of our ongoing interest in green chemistry and ILs catalyzed organic reactions,
3
the solvent of water.
Results and discussion
The ionic liquid catalysts which we have synthesized such as 1ꢀbutylꢀ1,4ꢀdiazabicyclo[2.2.2]octanylium bromide
(
[DabcoꢀC ]Br), chloride ([DabcoꢀC ]Cl), 1ꢀ(2,3ꢀdihydroxypropyl)ꢀ1,4ꢀdiazabicyclo[2.2.2]octanylium chloride
4 4
(
[DabcoꢀDHP]Cl), and 1,4ꢀdiazabicyclo[2.2.2]octane hydroacetate ([DabcoꢀH][AcO]), hydrotetrafluoroborate
[DabcoꢀH][BF ]), hydrochloride ([DabcoꢀH]Cl) and hydrogensulfate ([DabcoꢀH][HSO ]) are shown in Figure
(
4
4
[21, 23]
1
.
Figure 1. Structures of the Dabcoꢀbase ionic liquid catalysts.
Initially, the reaction between isatin (1a) and indole (2a) was employed as the model reaction to screen the
Dabcoꢀbase ILs catalysts in water as well as other common solvents in order to develop appropriate reaction
conditions. As can be seen from the results summarized in Table 1, all tested Dabcoꢀbase ILs catalysts could drive
the reaction, but a mixture of 3ꢀ(indolꢀ3ꢀyl)ꢀ3ꢀhydroxy oxindole (3a) and 3, 3ꢀdiindolyl oxindole (4a) were formed
in most cases (Table 1, entries 1–4 and 6). The encouraging results obtained when [DabcoꢀH][BF
DabcoꢀH][HSO ] were employed in the reaction, they worked well to afford the products 3a and 4a in good yield
respectively (Table 1, entries 5 and 7). For comparison, other solvents were also tried in the presence of
4
] and
[
4
[
DabcoꢀH][BF
Table 1, entries 8−11). Thus, a typical reaction procedure for the synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles from
](10 mol%) in water at 55 °C has been
established (Table 1, Entry 12) (Condition A). Then we raised the temperature up to 90°C, the reaction that
4
] under 55°C, but a mixture of products 3a and 4a were obtained with moderate to good yields
(
isatins (1 mmol) and indoles (1 mmol) catalyzed by [DabcoꢀH][BF
4

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4
between isatins (1 mmol) and indoles (2 mmol) catalyzed by [DabcoꢀH][HSO ] could afford 3, 3ꢀdiindolyl
oxindole (4a) in an excellent yield of 98% within only 2 hours (Table 1, Entry 13)(Condition B). When the
reaction was carried out in water without using catalyst at 90°C, none of 3a or 4a was obtained that indicates the
necessity of the catalyst (Table 1, entry 14).
In this procedure, after completion of the reaction, the crude products were easily separated from the mixture just
by filtering. The ionic liquid catalysts dissolved in water which could be easily recovered and directly reused in the
next recycling run under the same conditions. Water is cheap, safe, nonꢀtoxic and readily available, using water as
solvent allowed these Friedel–Crafts alkylation reactions to be performed in a very simple and green manner.
Table 1. Friedel–Crafts reaction of isatin and indole catalyzed by Dabcoꢀbase ionic liquid catalysts under different
a
conditions
b
Entry
Cat
Solvent
T (°C)
T (h)
Yield (%)
3
a
4a
21
12
12
16
ꢀꢀꢀ
67
82
<5
17
13
8
1
2
3
4
5
6
7
[DabcoꢀC
4
]Br
]Cl
H
H
2
2
O
O
55
55
55
55
55
55
55
55
55
2
2
1
2
1
2
3
6
6
1
6
1
2
6
48
49
72
65
85
16
ꢀꢀꢀ
57
66
73
76
85
ꢀꢀꢀ
ꢀꢀꢀ
[DabcoꢀC
4
[DabcoꢀDHP]Cl
[DabcoꢀH]AcO
H O
2
H
H
H
H
2
2
2
2
O
O
O
O
[DabcoꢀH][BF
4
]
[DabcoꢀH]Cl
[DabcoꢀH][HSO
4
]
c
8
[DabcoꢀH][BF4]
CH CN
3
c
9
[DabcoꢀH][BF
[DabcoꢀH][BF
[DabcoꢀH][BF
[DabcoꢀH][BF
4
]
4
]
4
]
4
]
THF
c
1
0
2 5
C H OH 55
c
11
(ClCH
2
)
2
55
55
90
90
c
1
1
1
2
3
4
H
2
O
ꢀꢀꢀ
98
ꢀꢀꢀ
[DabcoꢀH][HSO4] H O
2
ꢀꢀꢀ
2
H O
a
b
c
, ,
Conditions: isatin (1a 1 mmol) and indole (2a 2 mmol), Dabcoꢀbase catalyst (0.1 mmol), and solvent 1.0 mL.
Isolated yield.
1
mmol indole (2a) was used.
Having optimized the conditions, we then explored the generality of this method for the synthesis of
ꢀindolylꢀ3ꢀhydroxy oxindoles from isatins and indoles in the presence of 10 mol% the IL catalyst [DabcoꢀH][BF4]
3
in water under 55°C (Condition A). As shown in Table 2, the Friedel–Crafts reactions between isatins and indoles
with different substituents all proceeded well to afford the corresponding 3ꢀindolylꢀ3ꢀhydroxy oxindoles in good to

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excellent yields (83ꢀ96%) within 30ꢀ90 min, and only monoindolylation products were formed under this
condition.
a
4
Table 2. Synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles catalyzed by [DabcoꢀH][BF ] in water.
b
Entry
1
isatin
Indole
Product T (min) Yield (%)
3a
3b
3c
3d
3e
60
30
45
30
90
85
93
91
96
83
O
Br
2
3
4
5
O
O
O
2a
2a
2a
2a
N
H
1b
O
MeO
O2N
N
H
c
1
O
N
H
d
1
6
7
1e
1e
1e
3f
3g
3h
60
60
60
92
95
93
8
9
1e
1e
3i
3j
45
60
94
93
1
0
1
1
1a
1a
2d
2f
3k
3l
60
90
96
90
1
2

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a
, , 4
Conditions: isatins (1 1 mmol) and indoles (2 1 mmol), ionic liquid catalyst [DabcoꢀH][BF ] (0.1 mmol), and
water 1.0 mL.
b
Isolated yield.
This is a simple and mild reaction, which is readily amenable on large scale synthesis for 3ꢀindolylꢀ3ꢀhydroxy
oxindoles. By using this procedure (Condition A), we tried out the reactions on a 50ꢀmmol scale, 11.2 g of 3a and
1
3.8 g of 3k were prepared in the yield of 85% and 94% respectively (Figure 2). Therefore, this is an easy access
to obtain 3ꢀindolylꢀ3ꢀhydroxy oxindoles on large scale.
NH
NH
MeO
O
O
OH
OH
N
H
N
H
3a
3k
11.2 g, yield 85%
13.8 g, yield 94%
Figure 2. Synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles 3a and 3k on 50 mmol scale.
The catalytic Friedel–Crafts reaction of 3ꢀindolylꢀ3ꢀhydroxy oxindoles (3) and aromatic compounds is an atom
economic procedure to construct both structural motifs, and it just produces water as waste. The key intermediates
3
can be prepared on large scale in a very single step from isatins as shown in Figure 2. Reactions for the synthesis
of 3,3ꢀdiaryl oxindoles from isatins often suffered a large excess amount of strong acids or superacids. Here, in
order to take advantage of the different catalytic activities between [DabcoꢀH][BF ] and [DabcoꢀH][HSO ], we
4
4
planned a twoꢀstep green protocol for the synthesis of 3,3ꢀdiindolyl oxindoles in a more controlled manner. In this
protocol, the key intermediate 3ꢀ(indolꢀ3ꢀyl)ꢀ3ꢀhydroxy oxindole (3a), which was synthesized under Condition A,
was treated with 1 equiv of another molecule of indole under Condition B to give the desired 3,3ꢀdiindolyl
oxindole (4a) in an excellent yield of 98%. This means that unsymmetrical 3,3ꢀdiindolyl oxindoles even
unsymmetrical 3,3ꢀdiaryl oxindoles could be achieved by using this twoꢀstep protocol.
Scheme 1. Twoꢀstep protocol for the efficient synthesis of 3,3ꢀdiindolyl oxindole 4a.
Next, the scope of 3ꢀindolylꢀ3ꢀhydroxy oxindoles and indoles was investigated under Condition B for the synthesis
of unsymmetrical 3,3ꢀdiindolyl oxindoles. As shown in Table 3, a number of unsymmetrical 3,3ꢀdiindolyl
oxindoles with enough diversity could be readily obtained by this method. The influence of indoles with different
substituents was studied, which found that all the differently substituted indoles, with electronꢀwithdrawing or
ꢀ
(
donating groups worked well with 3ꢀindolylꢀ3ꢀhydroxy oxindoles to afford the desired products in excellent yields
95ꢀ98%) within only 0.5ꢀ1 hour.
a
Table 3. Synthesis of unsymmetrical 3, 3ꢀdiindolyl oxindoles catalyzed by [DabcoꢀH][HSO ] in water.
4

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Time
h)
Yield
Entry
1
3
Indole
Product
b
(
(%)
4a
0.5
98
2
3
4
5
3a
3a
3a
3a
4b
4c
4d
4e
0.5
0.75
0.5
98
98
98
98
0.75
6
7
2a
4d
0.75
97
3h
3h
2b
2c
4f
1
95
97
8
4g
0.5
a
Conditions: 3ꢀindolylꢀ3ꢀhydroxy oxindoles (1 mmol) and indoles (1 mmol), ionic liquid catalyst
[
b
DabcoꢀH][HSO
Isolated yield.
4
] (0.1 mmol), and water 1.0 mL.
Afterwards, to demonstrate the generality of this method, we further investigated other (hetero)aromatic
compounds, including Nꢀmethylpyrrole, phenol, pꢀcresol, pꢀchlorophenol and N,Nꢀdimethylaniline, instead of
indoles to broaden the substrates of this Friedel–Crafts reaction under Condition B. As shown in Table 4, all the
substrates were well tolerated to furnish the desired FriedelꢀCrafts products in good to excellent yields within only
0
.5ꢀ2 hour. Excellent regioselectivity was observed in the case of phenol, only the para Friedel–Crafts products
were obtained (Table 4, entries 3ꢀ4). While the para position of phenol was blocked, such as pꢀcresol and
pꢀchlorophenol, the reaction gave the ortho alkylated products in excellent yields (Table 4, entries 5ꢀ7). It is very
important that pꢀchlorophenol and N,Nꢀdimethylaniline were the first time as the substrates employed in this
reaction (Table 4, entries 7 and 8). All the Friedel–Crafts products of unsymmetrical 3,3ꢀdiaryl oxindoles in Table
4
are new compounds.
a
4
Table 4. Synthesis of unsymmetrical 3,3ꢀdiaryl oxindoles catalyzed by [DabcoꢀH][HSO ] in water.

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Time
h)
Yield
Entry
1
ArꢀH
Product
b
(
(%)
0.5
0.5
96
97
NH
MeO
O
2
N
N
H
Me
O
5
b
NH
3
4
5
0.5
0.5
1
93
85
95
N
H
OH
5
c
6
7
1
0.5
2
92
94
88
8
a
Conditions: 3ꢀindolylꢀ3ꢀhydroxy oxindoles (1 mmol) and aromatic compounds (1 mmol), ionic liquid catalyst
[
b
DabcoꢀH][HSO
Isolated yield.
4
] (0.1 mmol), and water 1.0 mL.
The reusability of the catalyst was also examined for the synthesis of 4b. After completion of the reaction, the
catalyst could be easily recycled by filtering the products from the mixture. The filtrate containing the water and
the IL catalyst [DabcoꢀH][HSO
It was observed that this Dabcoꢀbase catalyst could be recovered and reused in the Friedel–Crafts reaction of
ꢀ(indolꢀ3ꢀyl)ꢀ3ꢀhydroxy oxindole (3a) and 5ꢀbromoindole for five times at least.
4
] could be directly reused for the next cycle. The results are presented in Figure 3.
3

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4
Figure 3. Recycling of the catalyst [DabcoꢀH][HSO ] for the synthesis of 4b.
A reasonable pathway for the synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles (3) and unsymmetrical 3,3ꢀdiaryl
oxindoles (4 or 5) catalyzed by [DabcoꢀH][HSO ] is shown in Scheme 2. The step I involves the formation of
activated isatin (M-1) followed by its reaction with indole to generate intermediate M-2 that subsequently
undergoes a hydrogen transfer to yield 3 and [DabcoꢀH][BF ]. In the following step II which reacts under 90°C in
water, the protonation of 3 is done by [DabcoꢀH][HSO ] to give the intermediate M-3. The lone pair electron of
4
4
4
2
nitrogen in M-3 causes the exit of the living group (H O) and gives the intermediate M-4, which subsequently
undergoes further addition with the (hetero)aromatic molecule to afford the final products unsymmetrical
3
,3ꢀdiaryl oxindoles (4 or 5).
X
H
SO42-
H
N
X
N
H
N
N
H
-H2O
O
OH2
BF4
SO42-
H
O
O
N
X
NH
OH
N
H
N
H
H
M-2
M-3
X
N
X
M-4
O
O
HSO4
N
H
N
H
O
N
N
3
H
H
N
N
O
BF4
Ar H
BF4
NH
O
N
H
H
NH
O
Ar
M-1
X
O
N
H
O
Ar
SO42-
N
X
H
M-5
N
H
5
Scheme 2. Proposed reaction mechanism.
Conclusion
In conclusion, we have described a green and novel protocol for highly efficient synthesis of 3ꢀindolylꢀ3ꢀhydroxy
oxindoles and unsymmetrical 3,3ꢀdiaryl oxindoles using catalytic amount of efficiently reusable Dabcoꢀbase ionic
liquid catalysts. All the reactions, using water as solvent, allowed FriedelꢀCrafts reactions to be performed in a
very simple, clean and green manner. The method also offers several other significant advantages including simple
operation, excellent yield, short reaction time, atom economy, scaling up to multigram quantities, high
chemoselectivity, no use of metals, ease of separation and recyclability of the catalyst, as well as the ability to
tolerate a wide variety of substitutions in the components. To the best of our knowledge, such an efficient

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FriedelꢀCrafts reaction performed in water for the synthesis of 3ꢀindolylꢀ3ꢀhydroxy oxindoles and unsymmetrical
,3ꢀdiaryl oxindoles is reported for the first time. Further investigations and applications of this transformation for
3
the synthesis of other biologically active molecules are still in progress. Results from such investigations will be
reported soon.
Experimental
General experimental information. All chemicals were purchased from commercial suppliers and were used
without further purification. Flash column chromatography was performed on silica gel (200–300 mesh). Melting
1
13
points were determined with an Xꢀ4 apparatus and are uncorrected. H NMR and C NMR spectra were recorded
on a Bruker AVꢀ400 spectrometer with DMSOꢀd as the solvent. Chemical shifts are reported relative to TMS as
6
1
internal standard. The H NMR data are reported as the chemical shift in parts per million, multiplicity (s, singlet;
d, doublet; t, triplet; m, multiplet), coupling constant in hertz, and number of protons. HRMS were obtained on an
IonSpec FTꢀICR mass spectrometer with ESI resource.
General procedure for the synthesis of 3-indolyl-3-hydroxy oxindoles (3). A 5ꢀmL round bottomed flask was
4
charged with the isatins (1, 1 mmol), indoles (2, 1 mmol), [DabcoꢀH][BF ] catalyst (0.1 mmol), and water 1.0 mL.
Then the mixture was vigorously stirred at 55°C. The formation of the products was monitored by TLC. After
completion of the reaction, the mixture was cooled to room temperature, filtered and washed with cold methanol (2
mL), and then dried to obtain the crude products 3, which were purified by the crystallization technique and no
column purification was followed. The catalyst [DabcoꢀH][BF ] was left in water and directly reused in the next
4
recycling run under the same conditions. This catalytic system including the ionic liquid catalyst and water could
be recovered and reused in the reaction for five times at least.
[15(g)]
1
3
-hydroxy-3-(1H-indol-3-yl)indolin-2-one (3a)
δ = 6.35 (s, 1H, OH), 6.86 (t, 1H, J = 7.6 Hz, ArH), 6.90 (d, 1H, J = 7.6 Hz, ArH), 6.94 (t, 1H, J = 7.6 Hz, ArH),
.02 (t, 1H, J = 7.6 Hz, ArH), 7.07 (d, 1H, J = 2.0 Hz, ꢀC HNH), 7.24 (d, 2H, J = 8.0 Hz, ArH), 7.34 (t, 2H, J = 8.8
6
Red solid, mp 196ꢀ198 °C; H NMR (400MHz, DMSOꢀd ):
7
4
13
Hz, ArH), 10.34 (s, 1H, NH), 10.98 (s, 1H, NH); C NMR (100MHz, DMSOꢀd
6
): δ = 75.3, 110.0, 111.9, 115.8,
118.9, 120.7, 121.5, 122.1, 123.9, 125.2, 125.3, 129.5, 133.9, 137.2, 142.1, 178.9.
[15(g)]
1
5-bromo-3-hydroxy-3-(1H-indol-3-yl)indolin-2-one (3b)
White solid, mp 236ꢀ238 °C; H NMR (400MHz,
6
DMSOꢀd ): δ = 6.53 (s, 1H, OH), 6.87ꢀ6.92 (m, 2H, ArH), 7.05 (t, 1H, J = 8.0 Hz, ArH), 7.11 (d, 1H, J = 2.4 Hz,
1
3
ꢀ
C HNH), 7.34 (t, 3H, J = 8.0 Hz, ArH), 7.43 (d, 1H, J = 8.0 Hz, ArH), 10.51 (s, 1H, NH), 11.04 (s, 1H, NH);
4
C
6
NMR (100MHz, DMSOꢀd ): δ = 75.0, 111.7, 111.9, 113.4, 114.8, 118.8, 120.1, 121.3, 123.7, 124.8, 127.4, 131.8,
1
36.0, 136.9, 141.0, 178.0.
-hydroxy-3-(1H-indol-3-yl)-5-methoxyindolin-2-one (3c) White solid, mp 203ꢀ205 °C; H NMR (400MHz,
): δ = 3.65 (s, 3H, OCH ), 6.35 (s, 1H, OH), 6.84 (s, 3H, ArH), 6.86 (t, 1H, J = 8.0 Hz, ArH), 7.02 (t, 1H,
J = 7.6 Hz, ArH), 7.09 (d, 1H, J = 2.4 Hz, ꢀC HNH), 7.34 (t, 2H, J = 7.6 Hz, ArH), 10.17 (s, 1H, NH), 10.98 (s, 1H,
[26]
1
3
DMSOꢀd
6
3
4
13
NH); C NMR (100MHz, DMSOꢀd
6
): δ = 55.5, 75.4, 110.1, 111.6, 111.6, 113.7, 115.5, 118.6, 120.4, 121.1, 123.6,
25.0, 134.8, 135.0, 136.9, 155.0, 178.5.
-hydroxy-3-(1H-indol-3-yl)-5-nitroindolin-2-one (3d)
): δ = 6.76 (s, 1H, OH), 6.94 (t, 1H, J = 7.2 Hz, ArH), 7.05ꢀ7.12 (m, 3H, ArH and ꢀC
J = 8.0 Hz, ArH), 7.51 (d, 1H, J = 8.0 Hz, ArH), 8.06 (s, 1H), 8.26 (d, 1H, J = 7.2 Hz, ArH), 11.09 (s, 1H, NH),
1
[15(g)]
1
3
Yellow solid, mp 230ꢀ232 °C; H NMR (400MHz,
HNH), 7.37 (d, 1H,
DMSOꢀd
6
4
1
3
1
1.13 (s, 1H, NH); C NMR (100MHz, DMSOꢀd
6
): δ = 74.6, 110.1, 111.8, 114.0, 118.9, 120.1, 120.4, 121.5,
24.0, 124.8, 126.6, 134.3, 137.0, 142.4, 148.2, 178.6.
-hydroxy-3-(1H-indol-3-yl)-1-methylindolin-2-one (3e)
): δ = 3.17 (s, 1H, CH ), 6.44 (s, 1H, OH), 6.88 (t, 1H, J = 7.2 Hz, ArH), 7.02ꢀ7.10 (m, 4H, ArH and
1
[15(g)]
1
3
White solid, mp 115ꢀ118 °C; H NMR (400MHz,
DMSOꢀd
6
3

New Journal of Chemistry
Page 10 of 16
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DOI: 10.1039/C7NJ00174F
1
3
4 6
C HNH), 7.30ꢀ7.39 (m, 4H, ArH), 11.02 (s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 26.4, 75.1, 108.9, 111.9,
115.5, 119.0, 120.7, 121.5, 122.8, 124.0, 124.7, 125.3, 129.6, 133.2, 137.2, 143.5, 177.0.
[
15(g)]
1
3
-hydroxy-3-(5-bromo-1H-indol-3-yl)-1-methylindolin-2-one (3f)
): δ = 3.13 (s, 3H, CH
ArH and C HNH), 7.18 (dd, 1H, J = 1.6Hz, J = 8.4 Hz, ArH), 7.32ꢀ7.40 (m, 3H, ArH), 7.80 (s, 1H, ArH), 11.23 (s,
White solid, mp 215ꢀ217 °C; H NMR
(
400MHz, DMSOꢀd
6
3
), 6.52 (s, 1H, OH), 6.93 (d, 1H, J = 2.4 Hz, ArH), 7.07ꢀ7.11 (m, 2H,
4
1
3
1
1
3
H, NH); C NMR (100MHz, DMSOꢀd
25.6, 127.5, 129.8, 132.6, 136.0, 143.5, 176.8.
-hydroxy-3-(5-nitro-1H-indol-3-yl)-1-methylindolin-2-one (3g) White solid, mp 208ꢀ210 °C; H NMR
): δ = 3.15 (s, 3H, CH ), 6.70 (s, 1H, OH), 7.10ꢀ7.15 (m, 3H, 2ArH and C HNH), 7.40ꢀ7.44
6
): δ = 26.4, 74.8, 109.1, 111.7, 114.0, 115.3, 122.9, 123.9, 124.1, 124.8,
1
(
400MHz, DMSOꢀd
6
3
4
(
m, 2H, ArH), 7.54 (d, 1H, J = 8.8 Hz, ArH), 7.98ꢀ8.01 (dd, 1H, J = 1.6 Hz, J = 8.8 Hz, ArH), 11.76 (s, 1H, NH);
1
3
6
C NMR (100MHz, DMSOꢀd ): δ = 26.4, 74.7, 109.2, 112.6, 117.1, 118.3, 119.2, 123.1, 124.9, 125.0, 127.7,
1
6
3
30.0, 132.1, 140.5, 140.8, 143.6, 176.6. Anal. Calcd for C17
3.09; H, 4.23; N, 13.08.
13 3 4
H N O : C, 63.16; H, 4.05; N, 13.00. Found: C,
[27]
1
-hydroxy-3-(5-methoxy-1H-indol-3-yl)-1-methylindolin-2-one (3h)
Pale solid, mp 110ꢀ112 °C; H NMR
(
400MHz, DMSOꢀd ): δ = 3.15 (s, 3H, CH ), δ = 3.61 (s, 3H, OCH ), 6.41 (s, 1H, OH), 6.68 (dd, 1H, J = 2.4 Hz, J
6 3 3
=
4
8.8 Hz, ArH), 6.79 (d, 1H, J = 2.0 Hz, ArH), 6.99 (d, 1H, J = 2.4 Hz, ArH), 7.04ꢀ7.09 (m, 2H, ArH and C HNH),
1
3
7
.22 (d, 1H, J = 8.8 Hz, ArH), 7.31 (d, 1H, J = 7.2 Hz, ArH), 7.36 (t, 1H, J = 7.6 Hz, ArH), 10.85 (s, 1H, NH); C
6
NMR (100MHz, DMSOꢀd ): δ = 26.3, 55.5, 75.1, 102.7, 108.9, 111.4, 112.5, 115.1, 122.8, 124.7, 124.8, 125.7,
1
29.6, 132.3, 133.1, 143.5, 153.2, 177.0.
-hydroxy-3-(1-methyindol-3-yl)-1-methylindolin-2-one (3i) White solid, mp 93ꢀ95 °C; H NMR (400MHz,
): δ = 3.15 (s, 3H, CH ), δ = 3.71 (s, 3H, CH ), 6.43 (s, 1H, OH), 6.91 (t, 1H, J = 7.6 Hz, ArH), 7.03ꢀ7.09
m, 4H, ArH and C HNH), 7.30 (d, 1H, J = 7.2 Hz, ArH), 7.35ꢀ7.38 (m, 3H, ArH); C NMR (100MHz,
DMSOꢀd ): δ = 26.4, 32.8, 74.9, 109.0, 110.1, 114.7, 119.1, 121.1, 121.6, 122.8, 124.7, 125.7, 128.3, 129.6, 133.11,
[28]
1
3
DMSOꢀd
6
3
3
1
3
(
4
6
1
37.6, 143.5, 176.9.
[
15(g)]
1
3
-hydroxy-3-(2-methyl-1H-indol-3-yl)-1-methylindolin-2-one (3j)
White solid, mp 224ꢀ226 °C; H NMR
), 6.35 (s, 1H, OH), 6.71ꢀ6.74 (m, 1H, ArH),
.88ꢀ6.92 (m, 2H, ArH), 6.97ꢀ7.01 (m, 1H, ArH), 7.06 (d, 1H, J = 7.6 Hz, ArH), 7.18ꢀ7.24 (m, 2H, ArH), 7.32 (t,
(
6 3 3
400MHz, DMSOꢀd ): δ = 3.17 (s, 3H, NCH ), δ = 2.38 (s, 3H, CH
6
1
13
6
H, J = 7.2 Hz, ArH), 10.89(s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 13.7, 26.4, 76.0, 109.0, 109.7, 110.7,
118.7, 119.5, 120.3, 122.9, 124.9, 127.0, 129.5, 135.3, 137.6, 143.4, 177.3.
[
15(h)]
1
3
-hydroxy-3-(5-methoxy-1H-indol-3-yl)indolin-2-one (3k)
): δ = 3.65(s, 3H, OCH ), 6.41 (s, 1H, OH), 6.75 (d, 1H, J = 7.2 Hz, ArH), 6.91 (s, 1H, ArH), 6.95 (d, 1H,
J = 7.2 Hz, ArH), 7.01 (t, 1H, J = 6.4 Hz, ArH), 7.06 (s, 1H, ꢀC HNH), 7.29 (s, 3H, ArH), 10.38 (s, 1H, NH), 10.88
): δ = 55.6, 75.4, 103.1, 110.0, 111.3, 112.5, 115.4, 122.2, 124.7, 125.3,
25.8, 129.5, 132.4, 133.8, 142.1, 153.2, 178.9.
-hydroxy-3-(2-methyl-1H-indol-3-yl)indolin-2-one (3l)
): δ = 2.46 (s, 3H, CH ), 6.33 (s, 1H, OH), 6.78 (t, 1H, J = 7.6 Hz, ArH), 6.95 (t, 3H, J = 7.6 Hz, ArH),
.00 (t, 1H, J = 7.2 Hz, ArH), 7.28ꢀ7.29 (m, 3H, ArH), 10.39 (s, 1H, NH), 10.92 (s, 1H, NH); C NMR (100MHz,
DMSOꢀd ): δ = 13.7, 76.3, 109.8, 110.0, 110.7, 118.6, 119.6, 120.2, 122.1, 125.4, 127.0, 129.4, 133.9, 134.6, 135.3,
42.0, 179.1.
White solid, mp 193ꢀ195 °C; H NMR (400MHz,
DMSOꢀd
6
3
4
1
3
(
s, 1H, NH); C NMR (100MHz, DMSOꢀd
6
1
[
15(h)]
1
3
Pale solid, mp 188ꢀ190 °C; H NMR (400MHz,
DMSOꢀd
6
3
1
3
7
6
1
General procedure for the synthesis of unsymmetrical 3,3-diaryl oxindoles (4 and 5).
A 5ꢀmL round bottomed flask was charged with the 3ꢀindolylꢀ3ꢀhydroxy oxindoles (3, 1 mmol), (hetero)aromatic
compounds (1 mmol), [DabcoꢀH][HSO
4
] catalyst (0.1 mmol), and water 1.0 mL. Then the mixture was vigorously
stirred at 90 °C. The formation of the products was monitored by TLC. After completion of the reaction, the

Page 11 of 16
New Journal of Chemistry
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DOI: 10.1039/C7NJ00174F
mixture was cooled to room temperature, filtered and washed with cold water (2 mL), and then dried to obtain the
products 4 or 5. In general, no further purification method was required. The catalyst [DabcoꢀH][HSO ] was left in
water and directly reused in the next recycling run under the same conditions. The catalyst [DabcoꢀH][HSO
could be recovered and reused in the reaction for five times at least.
4
4
]
[
15(h)]
1
1
H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4a)
DMSOꢀd ): δ = 6.79 (t, 2H, J = 7.6 Hz, ArH), 6.86 (d, 2H, J = 2.0 Hz, ꢀC
.99 (t, 3H, J = 8.0 Hz, ArH), 7.18ꢀ7.27 (m, 4H, ArH), 7.34 (d, 2H, J = 8.0 Hz, ArH), 10.58 (s, 1H, NH), 10.92 (s,
White solid, mp 277ꢀ280 °C; H NMR (400MHz,
6
4
HNH), 6.91 (t, 1H, J = 7.6 Hz, ArH),
6
2
1
5
13
H, NH); C NMR (100MHz, CDCl
24.8, 125.6, 127.7, 134.5, 136.8, 141.2, 178.7.
-bromo-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4b)
): δ = 6.83 (t, 1H, J = 7.6 Hz, ArH), 6.95ꢀ7.05 (m, 4H, ArH and ꢀC
HNH), 7.18 (d, 1H, J = 8.0 Hz, ArH), 7.26 (d, 2H, J = 7.6 Hz, ArH), 7.39 (d, 1H, J = 8.0 Hz, ArH), 7.57 (d, 1H,
3 6
+DMSOꢀd ): δ = 52.5, 109.5, 111.5, 114.2, 118.1, 120.7, 120.8, 121.3, 124.2,
[18(d)]
1
Pale solid, mp >300 °C; H NMR
HNH), 7.14 (s, 1H,
(
ꢀ
400MHz, DMSOꢀd
6
4
C
4
J = 8.8 Hz, ArH), 7.96 (d, 1H, J = 9.6 Hz, ArH), 8.38 (s, 1H, ArH), 10.80 (s, 1H, NH), 11.05 (s, 1H, NH), 11.78 (s,
1
3
1
1
5
H, NH); C NMR (100MHz, DMSOꢀd
6
): δ = 52.8, 110.4, 112.3, 112.8, 114.6, 117.0, 117.6, 117.6, 119.0, 120.4,
21.6, 122.3, 124.8, 125.4, 125.9, 128.5, 128.7, 134.2, 137.4, 140.6, 140.8, 141.8, 178.9.
[
29]
1
-nitro-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4c)
): δ = 6.82 (t, 1H, J = 7.6 Hz, ArH), 6.90 (d, 2H, J = 7.2 Hz, ArH), 6.95 (t, 1H, J = 7.2 Hz,
ArH), 7.00ꢀ7.05 (m, 2H, ArH), 7.14ꢀ7.26 (m, 4H, ArH and ꢀC HNH), 7.37 (t, 2H, J = 7.6 Hz, ArH), 7.47 (s, 1H,
Yellow solid, mp 295ꢀ297 °C; H NMR
(
400MHz, DMSOꢀd
6
4
1
3
ArH), 10.69 (s, 1H, NH), 11.00 (s, 1H, NH), 11.22 (s, 1H, NH); C NMR (100MHz, DMSOꢀd
6
): δ = 52.5, 109.8,
111.0, 111.8, 113.8, 114.1, 114.2, 118.5, 120.3, 121.2, 121.8, 123.4, 123.6, 124.5, 125.0, 125.6, 126.0, 127.6, 128.2,
1
34.2, 135.8, 137.0, 141.4, 178.8.
[27]
1
4-methoxy-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4d)
Pale solid, mp >300 °C; H NMR
(
400MHz, DMSOꢀd
J = 9.2 Hz, ArH), 7.59 (d, 1H, J = 8.0 Hz, ArH), 10.84 (s, 1H, NH), 11.03 (s, 1H, NH), 11.18 (s, 1H, NH);
NMR (100MHz, DMSOꢀd ): δ = 52.7, 55.2, 103.5, 109.6, 110.6, 111.7, 112.2, 113.9, 114.3, 118.4, 120.9, 121.1,
6 4
): δ = 3.73 (s, 3H, OMe), 6.92 (s, 2H, ArH), 7.01ꢀ7.25 (m, 6H, ArH and ꢀC HNH), 7.47 (t, 4H,
1
3
C
6
1
21.6, 124.5, 125.1, 125.2, 125.9, 126.2, 128.0, 132.3, 134.7, 137.1, 141.5, 152.6, 178.9.
[
18(c)]
1
1
-methyl-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4e)
): δ = 3.70 (s, 3H, Me), 6.76ꢀ6.86 (m, 4H, ArH and ꢀC
.96ꢀ7.02 (m, 2H, ArH), 7.07 (t, 1H, J = 7.6 Hz, ArH), 7.19ꢀ7.26 (m, 4H, ArH), 7.34 (t, 2H, J = 7.2 Hz, ArH),
Pale solid, mp 290ꢀ292 °C; H NMR
(
400MHz, DMSOꢀd
6
4
HNH), 6.91 (t, 1H, J = 7.6 Hz, ArH),
6
1
1
3
0.59 (s, 1H, NH), 10.94 (s, 1H, NH); C NMR (100MHz, CDCl +DMSOꢀd ): δ = 32.5, 52.7, 109.6, 109.7, 111.7,
3
6
113.8, 114.4, 118.4, 118.4, 120.8, 121.0, 121.2, 121.4, 121.5, 124.5, 125.0, 125.8, 126.3, 127.8, 128.5, 134.7, 137.1,
1
37.5, 141.5, 178.9.
-bromo-5''-methoxy-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4f) Pale solid, mp 230ꢀ232 °C; H
): δ = 3.73 (s, 3H, OMe), 6.84 (s, 1H, ArH), 6.93 (dd, 1H, J = 2.0 Hz, J = 8.8 Hz,
ArH), 7.07 (d, 1H, J = 2.0 Hz, ArH), 7.16ꢀ7.19 (m, 2H, ꢀC HNH), 7.23 (d, 1H, J = 7.6 Hz, ArH), 7.36 (d, 1H, J =
1
5
NMR (400MHz, DMSOꢀd
6
1
2
4
8
.4 Hz, ArH), 7.41ꢀ7.50 (m, 3H, ArH), 7.57 (d, 1H, J = 8.4 Hz, ArH), 7.69 (s, 1H, ArH), 10.90 (s, 1H, NH), 11.05
1
3
(
s, 1H, NH), 11.42 (s, 1H, NH); C NMR (100MHz, DMSOꢀd
6
): δ = 52.5, 55.2, 102.9, 109.8, 110.6, 111.1, 112.4,
113.8, 113.8, 114.0, 121.8, 123.4, 123.7, 125.0, 125.2, 126.0, 127.6, 128.2, 132.3, 134.2, 135.9, 141.4, 152.7, 178.8.
+
HRMS (ESI) exact mass calcd for C25
-methoxy-5''-nitro-1H,1''H-[3,3':3',3''-terbenzo[b]pyrrol]-2'(1'H)-one (4g) Yellow solid, mp 270ꢀ272 °C; H
NMR (400MHz, DMSOꢀd ): δ = 3.55 (s, 3H, OMe), 6.52 (s, 1H, ArH), 6.75 (d, 1H, J = 8.4 Hz, ArH), 6.95 (s, 1H,
HNH), 7.00 (t, 1H, J = 7.2 Hz, ArH), 7.08 (d, 1H, J = 7.6 Hz, ArH), 7.20 (s, 1H, ꢀC HNH), 7.27ꢀ7.33 (m, 3H,
ArH), 7.60 (d, 1H, J = 8.8 Hz, ArH), 7.99 (d, 1H, J = 8.8 Hz, ArH), 8.44 (s, 1H, ArH), 10.84 (s, 1H, NH), 10.92 (s,
3 2
H18BrN O Na [M + Na] m/z 494.0480, found 494.0476.
1
5
6
ꢀ
C
4
4
13
1
6
H, NH), 11.81 (s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 52.9, 55.6, 103.1, 110.3, 111.1, 112.8, 114.2,

New Journal of Chemistry
Page 12 of 16
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DOI: 10.1039/C7NJ00174F
117.1, 117.5, 119.0, 122.4, 125.5, 125.6, 126.3, 126.4, 128.6, 128.8, 132.6, 132.7, 134.2, 140.6, 141.9, 153.2, 179.0.
+
HRMS (ESI) exact mass calcd for C25
-(1H-indol-3-yl)-3-(1-methyl-1H-pyrrol-2-yl)indolin-2-one (5a) Yellow solid, mp 265ꢀ267 °C; H NMR
400MHz, DMSOꢀd ): δ = 3.23 (s, 3H, Me), 5.57ꢀ5.58 (m, 1H, ArH), 5.88 (t, 1H, J = 3.2 Hz, ArH), 6.66 (s, 1H,
ArH), 6.86ꢀ6.89 (m, 2H), 6.94 (t, 2H, J = 7.2 Hz, ArH), 7.05 (t, 1H, J = 7.6 Hz, ArH), 7.19ꢀ7.23 (m, 3H), 7.36 (d,
18 4 4
H N O Na [M + Na] m/z 461.1226, found 461.1230.
1
3
(
6
1
3
1
1
1
3
6
H, J = 8.0 Hz, ArH), 10.66 (s, 1H, NH), 11.04 (s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 35.4, 53.5, 106.1,
09.9, 110.2, 112.1, 114.6, 119.1, 120.8, 121.6, 122.1, 123.4, 125.2, 125.3, 126.2, 128.5, 130.3, 134.5, 137.2, 141.2,
+
78.3. HRMS (ESI) exact mass calcd for C21
H
17
N
3
ONa [M + Na] m/z 350.1269, found 350.1277.
1
-(1H-indol-3-yl)-5-methoxy-3-(1-methyl-1H-pyrrol-2-yl)indolin-2-one (5b) White solid, mp 248ꢀ250 °C; H
NMR (400MHz, DMSOꢀd ): δ = 3.24 (s, 3H, Me), 3.56 (s, 3H, OMe), 5.60ꢀ5.61 (m, 1H, ArH), 5.90 (t, 1H, J = 3.2
6
1 2
Hz, ArH), 6.57 (d, 1H, J = 2.0 Hz, ArH), 6.68 (t, 1H, J = 2.0 Hz, ArH), 6.72 (dd, 1H, J = 2.4 Hz, J = 8.8 Hz,
ArH), 6.82 (d, 1H, J = 2.4 Hz, ArH), 6.92ꢀ6.97 (m, 2H), 7.19ꢀ7.26 (m, 3H), 10.66 (s, 1H, NH), 10.89 (s, 1H, NH);
1
3
6
C NMR (100MHz, DMSOꢀd ): δ = 35.0, 44.0, 52.9, 54.9, 102.2, 105.5, 109.4, 109.7, 110.9, 112.1, 113.7, 121.6,
1
23.3, 124.7, 126.2, 127.9, 129.7, 131.8, 134.2, 140.6, 152.7, 177.8. HRMS (ESI) exact mass calcd for
+
C H N O Na [M + Na] m/z 380.1375, found 380.1369.
2
2
19
3
2
1
3
-(4-hydroxyphenyl)-3-(1H-indol-3-yl)indolin-2-one (5c) White solid, mp 166ꢀ168 °C; H NMR (400MHz,
DMSOꢀd ): δ = 6.68 (d, 2H, J = 8.8 Hz, ArH), 6.77ꢀ6.81 (m, 2H), 6.93ꢀ6.96 (m, 2H), 6.99ꢀ7.02 (m, 2H), 7.07 (d,
H, J = 8.8 Hz, ArH), 7.19ꢀ7.22 (m, 2H), 7.33 (d, 1H, J = 8.0 Hz, ArH), 9.37 (s, 1H, OH), 10.59 (s, 1H, NH),
6
2
1
1
13
6
0.98 (s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 56.4, 109.6, 111.5, 114.9, 115.6, 118.2, 120.7, 120.9,
21.5, 124.3, 125.1, 125.4, 127.8, 128.5, 130.8, 134.4, 136.9, 141.1, 156.2, 178.8. HRMS (ESI) exact mass calcd
+
for C22
H
17
N
2
O
2
[M + H] m/z 341.1290, found 341.1291.
1
3
-(4-hydroxyphenyl)-3-(1H-indol-3-yl)-5-methoxyindolin-2-one (5d) White solid, mp 200ꢀ202 °C; H NMR
400MHz, DMSOꢀd ): δ = 3.50 (s, 3H, OMe), 6.43 (s, 1H, Ar), 6.69 (d, 3H, J = 7.6 Hz, ArH), 6.74 (s, 1H, Ar),
.95 (t, 2H, J = 7.6 Hz, ArH), 7.09 (d, 2H, J = 8.0 Hz, ArH), 7.21 (t, 3H, J = 9.2 Hz, ArH), 9.35 (s, 1H, OH), 10.57
(
6
6
1
3
(
s, 1H, NH), 10.81 (s, 1H, NH); C NMR (100MHz, DMSOꢀd ): δ = 55.0, 56.4, 103.2, 109.5, 110.4, 112.0, 114.8,
6
115.2, 121.5, 125.0, 125.2, 125.9, 127.7, 128.6, 130.7, 132.1, 134.4, 141.2, 152.4, 156.2, 178.8. HRMS (ESI) exact
+
mass calcd for C23
-(2-hydroxy-5-methylphenyl)-3-(1H-indol-3-yl)indolin-2-one (5e) Yellow solid, mp 131ꢀ132 °C; H NMR
400MHz, DMSOꢀd ): δ = 1.98 (s, 3H, Me), 6.52 (d, 1H, J = 2.0 Hz, ArH), 6.58 (d, 1H, J = 8.0 Hz, ArH), 6.73 (s,
19 2 3
H N O [M + H] m/z 371.1396, found 371.1403.
1
3
(
6
1
7
H, ArH), 6.82ꢀ6.87 (m, 3H, ArH), 6.89ꢀ6.91 (m, 2H, ArH), 7.04 (t, 1H, J = 7.6 Hz, ArH), 7.15ꢀ7.19 (m, 1H, ArH),
.35 (d, 1H, J = 8.0 Hz, ArH), 7.49 (t, 1H, J = 8.4 Hz, ArH), 9.14 (s, 1H, OH), 10.16 (s, 1H, NH), 10.93 (s, 1H,
13
NH); C NMR (100MHz, DMSOꢀd
6
): δ = 20.4, 55.6, 108.8, 111.5, 113.4, 115.2, 117.9, 120.6, 121.0, 122.7, 124.1,
1
24.6, 125.8, 126.2, 126.7, 127.3, 128.3, 130.3, 133.8, 137.2, 138.3, 142.4, 152.6, 179.2. HRMS (ESI) exact mass
+
19 2 2
calcd for C23H N O [M + H] m/z 355.1447, found 355.1440.
1
3
-(2-hydroxy-5-methylphenyl)-3-(5-methoxy-1H-indol-3-yl)indolin-2-one (5f) White solid, mp 142ꢀ143 °C; H
NMR (400MHz, DMSOꢀd ): δ = 2.01 (s, 3H, Me), 3.55 (s, 3H, OMe), 6.50 (d, 1H, J = 1.6 Hz, ArH), 6.59 (d, 1H, J
8.0 Hz, ArH), 6.72 (dd, 1H, J = 8.4 Hz, J = 2.4 Hz, ArH), 6.77 (s, 1H, ArH), 6.83ꢀ6.90 (m, 4H, ArH), 6.95 (s,
H, ArH), 7.15ꢀ7.19 (m, 1H, ArH), 7.25 (d, 1H, J = 8.8 Hz, ArH), 9.13 (s, 1H, OH), 10.16 (s, 1H, NH), 10.80 (s,
6
=
1
2
1
1
1
1
3
6
H, NH); C NMR (100MHz, DMSOꢀd ): δ = 20.4, 55.3, 55.6, 105.3, 108.8, 110.9, 111.9, 112.9, 115.3, 120.6,
24.1, 125.4, 126.2, 126.4, 127.3, 128.3, 130.4, 132.4, 133.9, 142.4, 152.2, 152.6, 179.3. HRMS (ESI) exact mass
+
calcd for C24
H
21
N
2
O
3
[M + H] m/z 385.1552, found 385.1545.
1
3
-(5-chloro-2-hydroxyphenyl)-3-(5-methoxy-1H-indol-3-yl)indolin-2-one (5g) White solid, mp 126ꢀ127 °C; H
NMR (400MHz, DMSOꢀd ): δ = 3.58 (s, 3H, OMe), 6.51 (d, 1H, J = 1.6 Hz, ArH), 6.71 (d, 1H, J = 8.4 Hz, ArH),
.75 (dd, 1H, J = 8.8 Hz, J = 2.4 Hz, ArH), 6.84ꢀ6.86 (m, 2H, ArH), 6.91ꢀ6.94 (m, 2H, ArH), 7.01 (s, 1H, ArH),
6
6
1
2

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7
.14 (dd, 1H, J
OH), 10.22 (s, 1H, NH), 10.89 (s, 1H, NH); C NMR (100MHz, DMSOꢀd
12.0, 112.1, 116.9, 120.7, 121.7, 124.0, 125.7, 125.9, 127.6, 127.7, 129.0, 129.5, 132.4, 133.0, 142.6, 152.4, 153.8,
1 2
= 8.4 Hz, J = 2.4 Hz, ArH), 7.18ꢀ7.22 (m, 1H, ArH), 7.29 (d, 1H, J = 8.8 Hz, ArH), 9.76 (s, 1H,
13
6
): δ = 55.3, 55.4, 105.3, 108.9, 111.0,
1
+
1
78.4. HRMS (ESI) exact mass calcd for C23
-(4-(dimethylamino)phenyl)-3-(1H-indol-3-yl)indolin-2-one (5h) White solid, mp 145ꢀ147 °C; H NMR
): δ = 2.92 (s, 6H, Me), 6.69 (d, 2H, J = 7.6 Hz, ArH), 6.89 (d, 1H, J = 2.8 Hz, ArH), 6.92ꢀ6.93
m, 1H, ArH), 6.96 (d, 1H, J = 6.8 Hz, ArH), 6.99 (d, 1H, J = 7.6 Hz, ArH), 7.12 (t, 1H, J = 8.4 Hz, ArH), 7.19 (t,
H, J = 7.6 Hz, ArH), 7.25 (d, 3H, J = 8.8 Hz, ArH), 7.29ꢀ7.32 (m, 2H, ArH), 8.12 (s, 1H, NH), 8.49 (s, 1H, NH);
2 3
H18ClN O [M + H] m/z 405.1006, found 405.1011.
1
3
(
(
400MHz, CDCl
3
1
1
3
3
C NMR (100MHz, CDCl ): δ = 40.71, 40.76, 57.19, 110.00, 111.26, 116.74, 119.52, 121.54, 122.07, 122.61,
1
24.19, 125.71, 125.92, 127.85, 128.71, 134.82, 137.03, 140.00, 180.37. HRMS (ESI) exact mass calcd for
+
C
24
H
22
N
3
O [M + H] m/z 368.1763, found 368.1770.
Acknowledgments
This work was financially supported by the National Natural Science Foundation of China (NSFC) (No.
2
1302101), NFFTBS (No. J1103306), and National Training Programs of Innovation and Entrepreneurship for
Undergraduates (No. 201610055092). We also thank the Nankai University State Key Laboratory of
ElementoꢀOrganic Chemistry for support.
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DOI: 10.1039/C7NJ00174F
An efficient Friedel-Crafts alkylation for synthesis of
-indolyl-3-hydroxy oxindoles and unsymmetrical 3,3-diaryl
3
oxindoles catalyzed by Dabco-base ionic liquids in water
Jun Tong, Lu-Shan Huang and Da-Zhen Xu*
An efficient, green and reusable catalystic system for controlled 3-indolylation of isatins.