Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient Conditions

Article abstract of DOI:10.1007/s10562-020-03332-7

Abstract: The synthesis of 2-amino-4H-chromenes through one-pot multicomponent reactions has received great attention due to the high atom efficiency and the broad bioactivities of the products. Here, the catalytic performances of a series of functional ionic liquids towards this type of reaction were investigated and the results showed that the ionic liquid, choline acetate ([Choline][Ac]), could efficiently promote this reactions under room temperature without the necessary of organic solvents. The reaction is easy to be conducted and the following work-up procedures are very simple. The pure products can be obtained through extraction and washing procedures, no column separation procedures are needed. Intriguingly, this reaction system can be easily scaled up to multi-gram, suggesting its perspective in industrial applications. In addition, the ionic liquid [Choline][Ac] can be easily prepared from cheap and biocompatible materials, and it can be feasibly recycled and reutilized for at least five cycles. Graphic Abstract: Various aldehydes, malononitrile and activated phenols could be converted to thecorresponding 2-amino-4H-chromenes with good to excellent isolated yields underthe catalysis of choline acetate at room temperature. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-020-03332-7

Catalysis Letters
https://doi.org/10.1007/s10562-020-03332-7
Biocompatible Ionic Liquid Promote One‑Pot Synthesis
of 2‑Amino‑4H‑Chromenes Under Ambient Conditions
Anlian Zhu1 · Qixing Li1 · Wanlu Feng1 · Dongshuang Fan1 · Lingjun Li1
Received: 10 March 2020 / Accepted: 26 July 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
The synthesis of 2-amino-4H-chromenes through one-pot multicomponent reactions has received great attention due to the
high atom efciency and the broad bioactivities of the products. Here, the catalytic performances of a series of functional
ionic liquids towards this type of reaction were investigated and the results showed that the ionic liquid, choline acetate
([Choline][Ac]), could efciently promote this reactions under room temperature without the necessary of organic solvents.
The reaction is easy to be conducted and the following work-up procedures are very simple. The pure products can be
obtained through extraction and washing procedures, no column separation procedures are needed. Intriguingly, this reac-
tion system can be easily scaled up to multi-gram, suggesting its perspective in industrial applications. In addition, the ionic
liquid [Choline][Ac] can be easily prepared from cheap and biocompatible materials, and it can be feasibly recycled and
reutilized for at least fve cycles.
Graphic Abstract
Various aldehydes, malononitrile and activated phenols could be converted to thecorresponding 2-amino-4H-chromenes
with good to excellent isolated yields underthe catalysis of choline acetate at room temperature.
Ar
ƾ Cheap and biocompatible
CN
OH
ionic liquid.
HO
O
NH2
R1
R1
ƾWide substrates generality.
ƾ Success in scale-up
utilization.
ƾ Simple operation and
work-up procedures.
Ar
OH
OH
CN
CHO
[Choline][Ac]
r.t.
Ar
NC
CN
O
NH2
OH
O
NH2
CN
Ar
product
ƾ Recyclable and reusable
catalytic ionic liquid.
malononitrile
Aldehyde
phenole
Keywords Ionic liquid · Choline acetate · 2-Amino-4H-chromenes · Room temperature
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-020-03332-7) contains
supplementary material, which is available to authorized users.
Extended author information available on the last page of the article
Vol.:(0123456789)
1 3

A. Zhu et al.
with simple synthetic procedures is still in great needed for
the further utilization of ionic liquids.
1 Introduction
In our continuous work on the development and utiliza-
tion of functional ionic liquids [32, 39–42], here, we found
that an ionic liquid choline acetate ([Choline][Ac]) could
promote the one-pot multicomponent reactions among alde-
hydes, malononitrile and activate phenols with excellent
activity and selectivity for the target 2-amino-4H-chromenes
under the solvent-free conditions at room temperature. No
organic solvent was needed in this reaction system and after
the reaction was completed, the products could be separated
by simple extraction and wash procedures, no column sepa-
ration procedures were necessary, which made the opera-
tion and work-up procedures very simple and applicable for
industrial applications. The successful scale-up trial of this
system to multi-grams and reutilization of ionic liquid to
fve cycles reinforced its industrial point. In addition, this
ionic liquid could be prepared from biocompatible and cheap
raw materials. So, the beneft from one-pot multicomponent
reaction itself plus the convenient preparation and reutiliza-
tion of ionic liquid, the concise operation and separation
procedures made the reaction system developed in this work
accorded greatly with the criteria of green chemistry.
2-Amino-4H-chromenes and their derivatives have received
great attention both in synthetic and biological aspects due
to their wide range of antibacterial [1], anti-infammatory
[2], antioxidant [3], anti-hiv [4], and anti-cancer activi-
ties [5]. The most intriguing method for their preparation
is through the one-pot multicomponent reactions(MCRs)
using malononitrile, activated phenoles and various alde-
hydes [6]. The reported catalytic systems have been involved
in tungstic acid functionalized mesoporous SBA-15 [7],
mesolite [8], Cu0.5Co0.5Fe2O4 nanoparticles [9], nanosized
MgO and Fe3O4 [10, 11], RGO-SO3H [12], DABCO [13],
{Mohr, 1975 #181}hydrotalcite [14], aqueous K2CO3 [15],
Et3N [16], MeSO3H [17], Sulfonic acid-functionalized MIL-
101 [18], iodine [19], L-proline [20], Fe(HSO4)3 [21], DBU
[22], Triethanolamine [23], molybdenum Schif base [24],
CNTs supported imidazolium-based ionic liquids [25, 26],
and so on. Although these catalytic methods simplifed the
synthetic and work-up procedures with high atom economy
coming from the inherent priorities of MCRs, most of them
required the use of volatile organic solvents, high reaction
temperature and sufered from the difculties to reutilize the
catalysts. In order to decrease the energy input, Dekamin
et al. [27] found an mechanochemical ball milling method
under the catalysis of potassium phthalimide at moderate
temperature, but the catalyst was still difcult to be reused.
So, the development of novel feasible and recyclable reac-
tion systems for the synthesis of 2-amino-4H-chromenes
with high catalytic activity under mild reaction conditions
is still urgent.
2 Experimental
2.1 Chemical and Apparatus
Resorcinol, 2-methylresorcinol, N,N-dimethylethanolamine,
diethanolamine, N,N-diethylethanolamine, betaine, 2-(meth-
ylamino)ethanol, triethanolamine, triethylamine, acetic acid
(Ac), propionic acid (Pro), n-butyric acid (But), n-pentanoic
acid (Pen), n-hexylic acid (Hex), lactic acid (Lac), malon-
onitrile, benzaldehyde, 4-nitrobenzaldehyde, 3-nitrobenza-
ldehyde, 2-nitrobenzaldehyde, 2-furaldehyde, 4-fuoroben-
zaldehyde, 4-bromobenzaldehyde, 2-bromobenzaldehyde,
p-methyl benzaldehyde, 4-methoxybenzaldehyde, 2-chlo-
robenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzal-
dehyde with AR grade were purchased from Aladdin Rea-
gents Company. DMSO-d6 and choline hydroxide (45 wt%
aqueous solution) were purchased from Sigma-Aldrich.
Anhydrous ethanol and n-hexane were purchased from Sin-
opharm Chemical Reagent Co. The water used in this work
was twice deionized.
Ionic liquids, as an excellent solvents and promising cata-
lysts, have showed signifcant performances to improve the
reactions through the modulating of reactivity and selectiv-
ity as well as facilitating the separation procedures, due to
their easy accessibility and tunable physicochemical prop-
erties [28–30]. The ingenious utilization of the synergetic
efects of cations and anions of ionic liquids has realized
many harsh reactions with high efciency under mild condi-
tions, decreasing the consuming of organic solvents and the
dependence of metal catalysts, and usually the whole time
and energy input can also be cut down [31–34]. This in a
great extent makes the whole related systems sustainable
and accorded with the principles of green chemistry [35].
However, as it has been witnessed that although the ionic liq-
uid catalytic systems can efciently relief the utilization of
organic solvents, their own synthetic procedures are usually
tedious and the organic solvents are unavoidable [36–38],
which without doubt will decrease the eco-efciency of the
whole production procedures. Therefore, the synthesis of
ionic liquids from biocompatible and renewable resources
1H NMR spectra and 13C NMR spectra were recorded
on BRUKER AV-400 and BRUKER AV-600 instrument at
room temperature by using TMS as internal standard. Melt-
ing points were taken from a XRC-1 Microscopic Melting
Point Measurer (Sichuan University instrument factory)
without correction.
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
The whole reaction process was monitored by TLC. After
2.2 Synthesis of Ionic Liquids
the reaction, the product was washed and centrifuged with
secondary water to remove the ionic liquid, the obtained
crude product was then recrystallized with ethanol to obtain
the pure target product.
The ionic liquids were synthesized through the reactions of
corresponding amines and acids. In a typical reaction for
the synthesis of [DMEOA][Ac], 0.1 mol N,N-dimethyleth-
anolamine (DMEOA) dissolved in 10 mL anhydrous ethanol
was slowly added to equal molar acetic acid under stirring
in an ice bath for 2 h, and then the mixture was reacted at
40 °C for further 24 h. The solvent was removed at 50 °C by
rotary evaporation under reduced pressure and then dried
under vacuum overnight to give the target ionic liquids. The
other ionic liquids including [DEEOA][Ac], [DEOA][Ac],
[TEOA][Ac], [Betain][Ac], [TEA][Ac], [MMEOA][Ac]
were also synthesized according to the above procedures.
Choline based ionic liquids like [Choline][Ac], [Choline]
[Pro], [Choline][Lac], [Choline][But], [Choline][Pen] and
[Choline][Hex] were synthesized in a similar way from Cho-
line hydroxide and corresponding acids.
2.4 Recycle and Reutilization of Ionic Liquid
The ionic liquid extracted with water after the completion of
reaction was rotary evaporated to remove most of the water
and then it was dried in a vacuum drying oven overnight.
The fully dried ionic liquid was directly used for the next
reaction cycle.
3 Results and Discussion
3.1 Structure Efect of Ionic Liquid on the Reaction
A series of ionic liquids based on ethanolamine were syn-
thesized and illustrated in Scheme 1. Their performances
in promoting the one-pot multicomponent synthesis of
2-amino-4H-chromenes were investigated using the reac-
tion of p-nitrobenzaldehyde, malonitrile and resorcinol as a
model and the results were collected in Table 1.The results
showed that when acetate anion was used, the ionic liquids
2.3 Typical Reaction Procedure for the Synthesis
of 2‑Amino‑4‑H‑Chromenes
Ionic liquid (0.5 mmol), phenols (0.5 mmol), aromatic alde-
hydes (0.5 mmol) were added to a 10 mL round-bottom fask
successively and stirred magnetically, and then malononitrile
(0.5 mmol) was added to the mixture at room temperature.
OH
OH
OH
H
OH
N
H2
N
N
NH
NH
CH3COO
CH3COO
CH3COO
[TEA][Ac]
CH3COO
CH3COO
[Choline][Ac]
[DEEOA][Ac]
OH
[MMEOA][Ac]
[DMEOA][Ac]
OH
O
OH
OH
OH
OH
HO
HN
N
H2N
N
N
CH3COO
OH
CF3COO
CH3CH2COO
CH3COO
CH3COO
[Choline][Pro]
OH
[Choline][TFA]
[Betaine][Ac]
OH
[TEOA][Ac]
[DEOA][Ac]
OH
OH
N
N
N
N
CH3CHCOO
OH
CH3CH2CH2CH2CH2COO
[Choline][Hex]
CH3CH2CH2CH2COO
CH3CH2CH2COO
[Choline][But]
[Choline][Pen]
[Choline][Lac]
Scheme 1 The structures of ionic liquids
1 3

A. Zhu et al.
Table 1 The efect of diferent ionic liquids on the reaction
Entrya
IL
Yield (%)b
Entrya
IL
Yield (%)b
1
2
3
4
5
6
7
[TEA][Ac]
50
90
89
96
60
72
70
8
9
10
11
12
13
14
[Betain][Ac]
10
8
87
60
80
78
85
[DMEOA][Ac]
[MMEOA][Ac]
[Choline][Ac]
[DEEOA][Ac]
[DEOA][Ac]
[TEOA][Ac]
[Choline][TFA]
[Choline][Pro]
[Choline][Lac]
[Choline][But]
[Choline][Pen]
[Choline][Hex]
aReaction conditions: resorcinol (0.5 mmol, 55.1 mg), p-nitrobenzaldehyde (0.5 mmol, 75.6 mg), malononitrile (0.5 mmol, 33.0 mg), IL
(0.5 mmol, 1.0 eq), room temperature, 3 h
bIsolated yield
with single hydroxyethly group on the nitrogen atom of
cations like MMEOA, DMEOA, and cholinum have excel-
lent performance towards the target products (entries 2–4,
Table 1), while ionic liquids with two ethyl groups or two or
three hydroxyethyl groups like DEEOA, DEOA and TEOA
only have moderate promoting efect (entries 6–7, Table 1).
However, the ionic liquids without hydroxyethyl group or
with carboxyl group on the cation like TEA or betaine have
poor catalytic activity (entries 1, 8, Table 1).The anion efect
of ionic liquids was investigated combining with the choline
cation. The results showed that the acetate anion has the
most excellent performance (entries 4, 9–14, Table 1), the
target product can arrive at 96% isolated yield under room
temperature. Although the further increase of the reaction
temperature to 40 °C using [Choline][Ac] as catalyst can
lead the completion of the reaction within 1 h, the room
temperature was still selected for the convenient operation
and lower energy input. The excellent performance of [Cho-
line][Ac] comparing with the other ionic liquids suggests
the importance of the synergetic efect of the cation and the
anion of ionic liquids. The proper basicity coming from the
anion and proper hydrogen bond donor ability from cation
of the ionic liquids are essential for the catalytic procedures.
2-amino-4H-chromenes, its amount efect on the model reac-
tion was investigated and the results were given in Table 2.
The results showed that the yield for the target compound
increased with the increase of the ionic liquid molar ratio to
substrates from 0.01 to 1.0 (entries 1–7, Table 2). When the
ionic liquid dosage was 1.0 equivalent, the yield reached the
highest, and the further increase of the ionic liquid amount
Table 2 The amount efect
Entrya
Ratiob
Yield (%)c
of ionic liquid on the model
reaction
1
2
3
4
5
6
7
8
0.01
0.02
0.05
0.1
0.2
0.5
53
55
58
85
88
90
96
94
1.0
1.5
aReaction conditions: resor-
cinol (0.5 mmol, 55.1 mg),
p-nitrobenzaldehyde (0.5 mmol,
75.6
mg),
malononitrile
(0.5 mmol, 33.0 mg), [Choline]
[Ac], room temperature, 3 h
3.2 Amount Efect of Ionic Liquid on the Reaction
bThe molar ratio of ionic liquid
to substrates
According to the well-deserved performance of the opti-
mized ionic liquid [Choline][Ac] in the production of
cIsolated yield
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
Table 3 Synthesis of various 2-amino-4H-chromene derivatives from aldehydes, malonitrile and resorcinols
Entrya
1
Ar
R1
H
Product
Time (h)
3
Yield (%)b
96
M.P. (°C)
Found
Report(Lit)
4-NO2C6H4
161–163
166–168 [27]
4a
2
3
C6H5
H
H
2
4
70
80
226–228
220–222
235–237 [27]
222–224 [27]
4b
4-BrC6H4
4c
4
5
4-ClC6H4
H
H
4
4
80
85
160–162
216–218
161–163 [27]
191–192 [27]
4d
4-FC6H4
4e
1 3

A. Zhu et al.
Table 3 (continued)
Entrya
Ar
R1
H
Product
Time (h)
5
Yield (%)b
90
M.P. (°C)
Found
Report(Lit)
6
3-ClC6H4
104–106
106–109 [43]
4f
7
8
3-NO2C6H4
H
H
3
3
90
82
174–176
167–169 [27]
97–99 [27]
4g
2-ClC6H4
100–101
4h
9
2-BrC6H4
H
H
3
5
90
85
206–208
196–198
205–206 [12]
188–190 [27]
4i
10
4-CH3C6H4
4j
11
4-OCH3C6H4
H
10
88
118–120
110–112 [27]
4k
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
Table 3 (continued)
Entrya
Ar
R1
H
Product
Time (h)
10
Yield (%)b
70
M.P. (°C)
Found
Report(Lit)
12
216–218
190–192 [27]
4l
13
14
15
16
4-NO2C6H4
2-CH3
2-CH3
2-CH3
2-CH3
4
92
60
70
92
110–112
–
4m
4-BrC6H4
4-ClC6H4
3-NO2C6H4
12
128–130
122–124
108–110
–
4n
9
220–221 [44]
4o
4
–
4p
1 3

A. Zhu et al.
Table 3 (continued)
Entrya
Ar
R1
Product
Time (h)
5
Yield (%)b
86
M.P. (°C)
Found
Report(Lit)
–
17
3-ClC6H4
2-CH3
148–150
4q
18
19
C6H5
2-CH3
12
77
81
128–130
–
4r
OHCC6H4
H
1
>300
>300 [11]
4s
aReaction conditions: resorcinol (0.5 mmol, 55.1 mg), aromatic aldehydes (0.5 mmol), malononitrile (0.5 mmol, 33.0 mg), [Choline][Ac]
(0.5 mmol, 81.5 mg)
bIsolated yield
has no signifcant infuence on the target compound produc-
Table 3) could also arrive at good isolated yields after 10 h
reaction. The reaction rate of 2-methylresorcinolwas a little
sluggish but it could also reacted with various aldehydes and
malonitrile, giving the target compounds with satisfactory
yields with a little prolonged reaction time(Entries 13–18,
Table 3). An interesting results was also obtained for the
reaction of terephthalaldehyde, two of its aldehyde groups
could both reacted with resorcinol and malonitrile with
exclusive chemo-selectivity (Entry 19, Table 3).
tion (entry 8, Table 2).
3.3 [Choline][Ac] Catalyzed Synthesis
of 2‑Amino‑4H‑Chromenes
The generality of this reaction system was frstly investigated
using the reactions of various aromatic aldehydes, maloni-
trile and resorcinols. The results collected in Table 3 showed
that diferent aromatic aldehydes with various substitutes
like electron-donating or electron-withdrawing groups, or
halogen groups could react with malonitrile and resorcinol
smoothly, leading to the satisfactory isolated yields for the
target yields within adequate reaction time (Entries 1–11,
Table 3). The heterocyclic aromatic aldehyde (Entry 12,
Furthermore, the reactivity of other activated phenols like
1-naphthol and 2-naphthol with aldehydes and malononi-
trile were also investigated to demonstrate the generality of
this novel reaction system. The results collected in Table 4
showed that the reactivity of 1-naphthol was higher than that
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
Table 4 Synthesis of various 2-amino-4H-chromene derivatives from aldehydes, malonitrile and naphthols
Entrya
1
Ar
Product
Time (h)
0.5
Yield (%)b
95
M.P. (°C)
Found
Report(Lit)
4-NO2C6H4
214–215
233–234 [27]
7a
2
3-NO2C6H4
0.6
94
206–208
211–213 [27]
7b
3
4
2-NO2C6H4
1
2
94
86
214–216
239–240
221–224 [24]
232–234 [27]
7c
4-ClC6H4
7d
1 3

A. Zhu et al.
Table 4 (continued)
Entrya
Ar
Product
Time (h)
5
Yield (%)b
82
M.P. (°C)
Found
Report(Lit)
5
3-ClC6H4
205–207
212–214 [23]
7e
6
7
4-FC6H4
4
2
80
86
215–216
233–235 [27]
232–234 [27]
7f
4-BrC6H4
240–242
7g
8
4-OCH3C6H4
7
82
139–140
187–189 [27]
7h
9
4-CH3C6H4
7
65
177–179
206–208 [27]
7i
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
Table 4 (continued)
Entrya
Ar
Product
Time (h)
4
Yield (%)b
80
M.P. (°C)
Found
Report(Lit)
10
C6H5
138–140
178–180 [10]
7j
11
4-NO2C6H4
7
95
142–144
187–189 [27]
8a
12
13
3-NO2C6H4
7
85
75
228–230
154–156
232–234 [27]
173–175 [26]
8b
4-ClC6H4
10
8c
14
3-ClC6H4
10
89
234–236
234–236 [45]
8d
1 3

A. Zhu et al.
Table 4 (continued)
Entrya
Ar
Product
Time (h)
14
Yield (%)b
90
M.P. (°C)
Found
Report(Lit)
15
4-FC6H4
222–224
226–228 [45]
8e
16
17
4-BrC6H4
14
10
87
75
210–212
260–262
238–240 [27]
283–285 [27]
8f
C6H5
8g
aReaction conditions: naphthol (0.5 mmol, 72.1 mg), aromatic aldehydes (0.5 mmol), malononitrile (0.5 mmol, 33.0 mg), [Choline][Ac]
(0.5 mmol, 81.5 mg)
bIsolated yield
of 2-naphthol, and both of them could be converted to the
target products with satisfactory yields.
3.5 Reusability of the Ionic Liquid
The reutilization of ionic liquid on the model reaction was
investigated and the results were illustrated in Fig. 1. It was
showed that the catalytic activity of choline acetate have
no signifcant decrease after fve cycles, suggesting the
excellent reusability. The FT-IR spectra of the fresh and
the reused ionic liquid have also been investigated and the
results were shown in Fig. 2. The results showed that this
ionic liquid have good stability in the reaction and recovered
procedures.
3.4 Scale‑up Experiment
Considering the good generality of this novel reaction sys-
tem in various aldehydes and phenols, we explored the
scale-up experiment to investigate its potential utilization
in industrial production. Ionic liquid (10 mmol), resorcinol
(10 mmol), p-nitrobenzaldehyde (10 mmol) and malon-
onitrile were added to a 25 mL round-bottom fask in turn
and stirred for 3 h at room temperature. The whole reaction
process was monitored by TLC. After the purifcation pro-
cedures, the pure product can arrive at 97%. After the reac-
tion was completed, 2 ml water was added to the reaction
mixtures, the crude product could be precipitated. The pure
product was then obtained by simple washing procedures
and the ionic liquid could be reutilized after simple drying.
3.6 Possible Mechanism
In the reaction procedure, the Knoevenagel reaction product
was monitored to be the reaction intermediate. According
to our previous work about the utilization of hydrogen bond
functionalized ionic liquids in synthesis, it was deduced that
1 3

Biocompatible Ionic Liquid Promote One-Pot Synthesis of 2-Amino-4H-Chromenes Under Ambient…
the hydroxyl group on the ionic liquid cation could acti-
vate the C=O of aldehyde, the ionic liquid anion actived
the α-H of malonitrile, leading to the formation of carbon
anions. Then the carbon anion attacked the carbonyl groups
of aldehyde to produce intermediate I. On the other hand,
the resorcinol was dehydrogenated by ionic liquid to produce
Phenoxy anion, which then reacted with intermediate I, and
after the following cyclization rearrangement procedures to
produce the target products (Scheme 2).
97
97
100
80
60
40
20
0
96
95
95
4 Conclusions
1
2
3
4
5
Runs
In this work, an efcient ionic liquid based catalytic sys-
tem for the preparation of 2-amino-4H-chromenewas was
reported. This ionic liquid could be easily prepared from
cheap and biocompatible materials. The reaction system
could be conducted at room temperature without the neces-
sary of additional organic solvents, and the work-up proce-
dures were very simple, no column purifcation was needed.
The following experiment suggested that the reaction sys-
tem could be scaled up to multi-gram scale. In addition, this
ionic liquid could be convenient recycled and reutilized for
at least fve cycles without signifcant activity decrease. The
above benefts of this reaction system showed that it is prom-
ising for the further utilization in industrial applications.
Fig. 1 The reutilization of ionic liquid
250
reused ionic liquid [Choline][Ac]
fresh ionic liquid [Choline][Ac]
200
150
T%
100
Acknowledgements This work was financially supported by the
National Natural Science Foundation of China (No. 21373079) and
S&T Research Foundation of Education Department of Henan Province
(No. 20A150022).
50
4000
3000
2000
1000
λ/cm-1
Fig. 2 FT-IR for the fresh and reused ionic liquid
Scheme 2 The plausible reac-
CN
CN
tion mechanism
H
O
Ac
Ar
CN
CN
-H2O
O
H
CN
CN
H
N
Ar
H
Intermediate I
[Choline][Ac]
HO
HO
OH
O
Ar
H
Ar
O
Ar
H
H
H
CN
CN
CN
CN
CN
Ar
O
HO
HO
O
NH
HO
NH2
HO
O
N
1 3

A. Zhu et al.
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Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
Afliations
Anlian Zhu1 · Qixing Li1 · Wanlu Feng1 · Dongshuang Fan1 · Lingjun Li1
* Anlian Zhu
alzhuchem@126.com
Ministry of Education, Collaborative Innovation Center
of Henan Province for GreenManufacturing of Fine
Chemicals, Henan Normal University, Xinxiang 453007,
Henan, People’s Republic of China
* Lingjun Li
lingjunlee@htu.cn
1
School of Chemistry and Chemical Engineering, Key
Laboratory of Green Chemical Media and Reactions,
1 3