A water-ethanol on-off fiber catalyst for the synthesis of substituted 2-amino-2-chromenes

Article abstract of DOI:10.1039/c4ra03985h

A DMAP (4-dimethylaminopyridine) functionalized polyacrylonitrile fiber catalyst (PAN_DMAPF) was prepared and used to efficiently catalyze three-component condensation reactions among an aldehyde, malononitrile and α-naphthol in water to afford

Full text of DOI:10.1039/c4ra03985h

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PAPER
A water–ethanol on–off fiber catalyst for the
synthesis of substituted 2-amino-2-chromenes
Cite this: RSC Adv., 2014, 4, 26122
a
ab
Yazhi Zhen,ab Huikun Lin,ab Shiyao Wang and Minli Tao
*
A DMAP (4-dimethylaminopyridine) functionalized polyacrylonitrile fiber catalyst (PANDMAPF) was prepared
and used to efficiently catalyze three-component condensation reactions among an aldehyde,
malononitrile and a-naphthol in water to afford the corresponding substituted 2-amino-2-chromenes.
The PANDMAPF exhibited excellent catalytic activities in water and methanol, but failed to show any
catalytic activity in ethanol and solvents with low polarity. In other words, water can turn the reaction on
but ethanol shuts it off. This differs greatly from the same reaction catalyzed by free DMAP or by a
tertiary amine functionalized polyacrylonitrile fiber. The PANDMAPF catalyst is applicable to a wide range
of aromatic aldehydes (80–99%). Moreover, this newly developed fiber catalyst also exhibited excellent
recyclability and reusability (up to seven times) without any additional treatment.
Received 1st May 2014
Accepted 3rd June 2014
DOI: 10.1039/c4ra03985h
www.rsc.org/advances
catalytic systems and nano-sized MgO4 are used in heteroge-
neous catalytic systems. Heterogeneous catalysts have several
1. Introduction
advantages over conventional homogeneous catalysts, such as
simpler post-treatments, reusability and the generation of less
pollution. Thus the development of new heterogeneous cata-
lysts is very important.
In accordance with sustainable development strategies, much
attention has been given to performing organic transformations
in benign media, especially multi-component condensation
reactions in which two or more steps are combined in one pot
without isolation of any intermediates. The use of toxic and
volatile organic solvents as reaction media has aggravated ever-
increasing environmental concerns. Therefore, environmen-
tally friendly processes that can be conducted in green solvents
are of urgently needed. The low cost of water along with its non-
toxic nature, makes it an ideal media for chemical synthesis and
transformations. Further, using a multi-component one-pot
condensation approach could result in tremendous, potential
cost savings in the areas of raw materials, energy, equipment,
labor and time. These advantages become even more attractive
if such reactions can be conducted using heterogeneous recy-
clable catalysts.
Substituted 2-amino-chromenes are widely employed as
pigments, cosmetics, photoactive materials,1 biodegradable
agrochemicals, and represent an important class of chemicals
which are the main constituents of many natural products.
However, most of the reported synthesis methods require pro-
longed reaction times, stoichiometric reagents, toxic solvents,
and the yields are only moderate.
DMAP is an efficient catalyst that has been studied inten-
sively since it was rst reported.5,6 Some homogeneous catalysts
have used soluble polymers as a support to immobilize DMAP
or its analogues.7–12 These homogeneous catalysts have a similar
efficiency to free DMAP, however, the separation is difficult.
Heterogeneous catalysts based on epoxy resins or mesoporous
silica13–16 have overcome this disadvantage, but their catalytic
efficiencies are lower than that of free DMAP. Thus the devel-
opment of heterogeneous catalysts with high catalytic efficien-
cies is of particular interest.
In our previous work, functionalized bers were successfully
used to catalyze a three-component Bigineili reaction17 and the
synthesis of thiophene derivatives.18,19 In this paper, a DMAP
functionalized polyacrylonitrile ber (PANDMAPF) was prepared
and used to catalyze the synthesis of substituted 2-amino-
chromenes in water. This ber catalyst showed an on–off
characteristic in water–ethanol system, and an excellent reus-
ability and recyclability.
Generally, for the synthesis of the substituted 2-amino-2-
chromenes, DMAP (4-dimethylaminopyridine)2 and DBU(1,8-
diazabicyclo[5.4.0]undec-7-ene)3 are used in homogeneous
2. Experimental
2.1 Reagents
aDepartment of Chemistry, School of Sciences, Tianjin University, Tianjin, 300072,
China
bCollaborative Innovation Center of Chemical Science and Engineering(Tianjin),
Tianjin 300072, China. E-mail: mltao@tju.edu.cn; Fax: +86-22-27403475; Tel: +86-
22-27890922
Polyacrylonitrile bers with lengths of 10 cm and diameters of
30 ꢀ 0.5 mm were purchased from the Fushun Petrochemical
Corporation of China. All aldehydes, naphthols, malononitrile,
N,N0-dimethyl-1, 3-propanediamine and the other reagents were
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of analytical grade and used without further purication. The ltered out. The HCl concentration of the remaining solution
water was deionized.
was determined by titration with 0.100 mol Lꢂ1 NaOH. The
exchange capacity was calculated based on the amount of acid
consumed.20
2.2 Apparatus and instruments
Elemental analysis was determined with an Elementar vario EL
analyzer. A model XL-30 scanning electron microscope (Philips)
was employed to characterize the surface of the modied bers.
FTIR spectra were collected with an AVATAR360 FTIR spec-
2.5 General procedure for the synthesis of 2-amino-2-
chromenes
A mixture of an aldehyde (1 mmol), malononitrile (1 mmol), a-
naphthol (1 mmol) and PANDMAPF (20 mol%) in 15 mL of water
was reuxed for 1 h (Scheme 2). Aer completion of the reac-
tion, the PANDMAPF was ltered and extracted with ethanol for 3
h using a Soxhlet extractor in order to collect all the adsorbed
products. The extracted ethanol was combined with the ltrate.
Aer removing the solvent with a rotary evaporator, the residue
was recrystallized with ethanol to give 2-amino-2-chromenes.
1
trometer (Thermo Nicolet). H NMR spectra were recorded on
an AVANCE III (600 MHz) instrument using TMS as the internal
standard. Melting points were taken on a Yanagimoto MP-500
apparatus.
2.3 Preperation of the ber catalyst
As the ber catalyst works through the DMAP moiety immobi-
lized on the ber, so N,N0-dimethyl-N-(4-pyridyl)-1,3-propane-
diamine was introduced to chemically bond the DMAP part on
the ber by –NH group.
3. Results and discussions
2.3.1 N,N0-Dimethyl-N-(4-pyridyl)-1,
3-propanediamine.
In this paper, a simple and efficient protocol for the synthesis of
2-amino-2-chromenes using PANDMAPF as a novel and eco-
friendly heterogeneous catalyst is described. The PANDMAPF has
selectivity to the solvent and the yields could be controlled by
adjusting the ratio of water to ethanol.
First, 4-chloropyridine hydrochloride (30 g, 0.2 mol) was added in
batches to a mixture of N,N0-dimethyl-1,3-propanediamine (62.5
mL), water (125 mL) and sodium carbonate (42.4 g, 0.4 mol) over
a course of 6 h. Then the mixture was reuxed for 12 h using TLC
(Thin Layer Chromatography) to track the reaction. Aer
completion of the reaction, the aqueous phase was extracted with
CH2Cl2 three times and the organic layers were combined. The
solvent was removed by evaporation and the residue was distilled
under reduced pressure to obtain a pale yellow oily substance
(bp: 178–180 ꢁC/40 mmHg, yield: 53.8%) which was determined
to be N,N0-dimethyl-N-(4-pyridyl)-1, 3-propanediamine.
2.3.2 DMAP Functionalized polyacrylonitrile ber (PAN-
DAMPF). The dried PANF (1 g) was put into a mixture of water (50
g) and N,N0-dimethyl-N-(4-pyridyl)-1, 3-propanediamine (50 g) in
a 250 mL three-neck ask and heated to reux for 18 h. The
modied PANF was ltered out and washed with deionized
water at 60–70 ꢁC until the pH of the wash water was 7. Then the
ber catalyst PANDAMPF was dried overnight under vacuum at 60
ꢁC. And the process was shown as Scheme 1.
3.1 Synthesis of PANDAMPF
The ber catalyst PANDMAPF was synthesized by graing N,N0-
dimethyl-N-(4-pyridyl)-1,3-propanediamine onto the surface of
PANF using water as the solvent. The extent of the modication
was determined from the acid exchange capacity and the weight
gain of the ber catalyst, where, the weight gain ¼ (the weight of
PANDMAPF ꢂ the weight of PANF)/(the weight of PANF). The
reaction conditions were optimized and the results are shown in
Table 1.
Table 1 shows that the weight gain increased with reaction
time and with w(amine)/w(H2O) ratio. Taking the strength of
the ber into consideration, entry 5 was selected as the optimal
condition. The acid exchange capacities of the ber catalysts
were determined as described in the Experimental section and
then used to determine the effective number of functional
groups. The titration result (0.67 mmol gꢂ1) was in good
2.4 Acid exchange capacities of the ber catalyst
The dried PANDAMPF (0.200 g) was immersed into 20 mL of accordance with the result calculated from the weight gain (0.66
0.100 mol Lꢂ1 HCl for 12 h. The neutralized ber was then mmol gꢂ1).
Scheme 1 Preparation of fiber catalyst PANDMAPF.
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Scheme 2 The three-component condensation reaction.
Table 1 Optimization of the synthesis conditions
Entry
w(amine)/w(H2O)
Time (h)
Weight gain (%)
1
2
3
4
5
6
1/2
3/4
1/1
1/1
1/1
1/1
14
14
12
14
18
20
2.1
6.5
7.8
9.1
15.8
19.4
3.2 Characterization of the ber catalyst
3.2.1 Elemental analysis. The elemental analysis of PANF,
PANDMAPF, PANDMAPF-1 (PANDMAPF used one time), and PAN-
DMAPF-7 (PANDMAPF reused seven times) are shown in Table 2.
Compared with PANF, PANDMAPF has less nitrogen and
carbon and more hydrogen. The formation of –CONH2 and
–CONMeR (R ¼ PyNMeCH2CH2CH2–, the DAMP moiety) groups
from the hydrolysis of the cyano groups and the immobilization
of the DAMP moiety account for this. In entries 3 and 4, the
carbon content increased and the hydrogen content decreased
which is probably due to the adsorption of the reaction inter-
mediates and product during the reaction.
Fig. 1 The SEM photograph of (a) PANF, (b) PANDMAPF, (c) PANDMAPF-
1, (d) PANDMAPF-7.
PANDMAPF has a new emerging broad peak at 3000–3700 cmꢂ1
.
3.2.2 Scanning electron microscopy (SEM). To distinguish
the differences among PANF, PANDAMPF and PANDAMPF used for
times, SEM photographs were taken. The SEM photographs
show that the PANF has a smooth surface, and that the surface
became slightly rougher aer it was modied with N,N0-
dimethyl-N-(4-pyridyl)-1,3-propanediamine. The surface of
PANDMAPF was unchanged aer it was used once and aer it was
used seven times. These results indicate that the ber catalyst
maintained its integrity aer being reused many times (Fig. 1).
3.2.3 Fourier-transfer infrared spectroscopy (FTIR). FTIR is
a useful tool to prove whether the N,N0-dimethyl-N-(4-pyridyl)-
1,3-propanediamine was graed onto the surface of PANF.
Compared to the IR spectrum of PANF, the spectrum of
This peak is evidence for the existence of –CONH2 groups which
is formed by the hydrolysis of –CN. In addition, the C–N
absorption peak at 2242 cmꢂ1 is weaker in PANDMAPF than in
PANF, which suggests that part of the cyano groups have dis-
appeared. The ester C]O stretching vibration at 1731 cmꢂ1 is
smaller in PANDMAPF than in PANF which is due to the ami-
nolysis and hydrolysis reactions. The new peak at 1554 cmꢂ1 in
the PANDMAPF spectrum is due to the frame vibrations of pyri-
dine which demonstrates the successful graing of N,N0-
dimethyl-N-(4-pyridyl)-1, 3-propanediamine onto the surface of
PANF. The characteristic peaks in PANDMAPF-7 are all weakened
due to the absorption of the reaction intermediates and product
during the reaction (Fig. 2).
3.3 Catalytic activities
Table
2 Elemental analysis of PANF, PANDMAPF, PANDMAPF-1,
3.3.1 Catalytic activities. The catalytic activity of PANDMAPF
for the three-component condensation reaction was investi-
gated in different solvents and the results are listed in Table 3.
As shown in Table 3, in the absence of any catalyst, the three-
component condensation with a-naphthol gave a low yield of
28% (Table 3, entry 1), whereas in the presence of PANF, the
yield decreased to 14% (Table 3, entry 2). This might be due to
PANDMAPF-7
Entry
Sample
N (%)
H (%)
C (%)
1
2
3
4
PANF
23.68
21.32
21.75
21.68
6.52
7.12
5.67
6.81
65.55
61.04
62.61
63.13
PANDMAPF
PANDMAPF-1
PANDMAPF-7
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organic reaction in water22 which can also be completely turned
off in ethanol. This result demonstrates that it is possible in
some cases to effectively catalyze an organic reaction in water
and that expensive and poisonous organic solvents are not
necessary.
Mechanism for this three-component reaction is depicted in
Scheme 3. In this three-component one-pot reaction, PANDMAPF
acts as the Brønsted proton scavenger and two steps of this
reaction take place on the surface of PANDMAPF. The rst step is
to form the Knoevenagel intermediate A. PANDAMPF would take
a proton away from naphthol which is adsorbed on the PAN-
DMAPF and generate the intermediate B by which naphthol is
activated. Then the nal product C was produced.
PANTF is different from the PANDMAPF in that it can undergo
long-range interactions with the anions. This may be the reason
why the three-component condensation reaction could be
conducted in both water and ethanol when PANTF was used as
the catalyst (Table 3, entries 5 and 6).
3.3.2 Effect of the solvent. The effect of several commonly
used solvents on the three-component reaction of 4-chlor-
obenzaldehyde, malononitrile and a-naphthol catalyzed by
PANDMAPF was then investigated and the results are shown in
Table 4. Proton donating solvents with higher polarities such as
methanol and H2O afforded fairly high yields (Table 4, entries 1
and 2). Among these solvents, water is the best choice in terms
of yield, expense, availability and being environmentally
benign. In solvents with aprotic and weaker polarities (Table 4,
entries 3–10), no nal products were obtained.
Next the effect of the solvent polarity was studied in more
details. Solvents with different polarities were obtained by
adjusting the ratio of water to ethanol and the results are shown
in Table 4 (entries 11–15). As the polarity of the solvent
increased, so did the yield. This is because naphthol is insoluble
in highly polar solvents, which forces it to accumulate on the
PANDMAPF surface, thus facilitating the activation of naphthol
to produce the nal product. These results demonstrate that the
reaction can be turned on just by adding enough water to the
Fig. 2 Fourier-transfer infrared spectra of the fibers.
Table 3 Catalytic activities of catalysts
Entry
Catalyst
Solvent
Yielda (%)
Yieldb (%)
1
2
3
4
5
6
7
8
None
PANF
H2O
H2O
CH3CH2OH
H2O
CH3CH2OH
H2O
28 (0)d
14 (0)d
81
72
94
90
0
97
0
0
DMAP
DMAP
PANTF
PANTFc
PANDMAP
PANDMAP
61
51
62
76
0
F
F
CH3CH2OH
H2O
51
a
Reactions were carried out with 4-chlorobenzaldehyde (1 mmol),
malononitrile (1 mmol) and a-naphthol (1 mmol) in the presence of
different catalysts (0.20 mmol) in water or ethanol (15 mL) under
b
reux for 1 h. Reactions were carried out under the same conditions
c
with b-naphthol instead of a-naphthol. PANTF was prepared by
d
graing N,N-dimethyl-1,3-propanediamine onto PANF.21 The yields
in () were obtained with ethanol as the solvent.
the adsorption of the reactants onto the surface of PANF, which system.
would reduce the collisions among the reactants. When ethanol
The experimental results prove that in ethanol, the reaction
was used as the solvent, with either the PANF catalyst or no terminates at step of the formation of Knoevenagel interme-
catalyst, there is no reaction. Using free DAMP as the catalyst diate A. This is because naphthol has a good solubility in
gave good catalytic activity in both water and ethanol (Table 3, ethanol which made it difficult to access the ber catalyst and
entries 3 and 4), but ethanol is much better due to the good undergo the next step.
solubility of the reactants in ethanol. Good solubilities ensure
sufficient collisions which facilitates the reaction. In addition, a
tertiary amine functionalized PANF (PANTF) gave excellent
3.4 Optimization of the reaction conditions
catalytic activity, both in water and ethanol (Table 3, entries 5
and 6). The yields were relatively low when b-naphthol was used catalyst loading on the three-component reaction was explored
as the reactant which due to steric hindrance. and the results are shown in Fig. 3. The yields of the conden-
3.4.1 Effect of catalyst amount. The effect of the amount of
Surprisingly, PANDAMPF did not show any catalytic activity in sation reaction increased greatly from 65% to 97% as the
ethanol (Table 3, entry 7), but exhibited excellent catalytic amount of catalyst increased from 5 to 20 mol%. However, no
activity in water (Table 3, entry 8). In ethanol, the reaction further increase in the yield was observed when the amount of
stopped at the Knoevenagel intermediate A (Scheme 3). In catalyst was increased from 20 to 30 mol%. Therefore 20 mol%
water, the reaction proceeded to the end with a high yield of of PANDMAPF was selected for all subsequent reactions.
97% which indicates that the graed DMAP is very important to
3.4.2 Effect of reaction time. The effect of reaction time
the catalytic activity and to solvent selectivity. To the best of our (from 10 to 70 min) on the yield was also investigated and the
knowledge, this is the rst catalyst to quantitatively catalyze an results are shown in Fig. 4. There was a sharp increase in the
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Scheme 3 The possible reaction mechanism.
Table 4 Effect of solvents
Entry
Solvent
Polarity
Yield of Aa,b (%)
Yield of producta,b (%)
1
2
3
4
5
6
7
8
Water
Methanol
Acetonitrile
1,4-Dioxane
Ethanol
Ethyl acetate
Tetrahydrofuran
Dichloromethane
Toluene
10.20
6.60
6.20
4.80
4.30
4.30
4.20
3.40
2.40
0.10
5.41d
6.94d
8.33d
9.19d
9.78d
—
—
98
99
99
93
98
97
99
97
99
28
17
—
—
97
94
0
0
0
0
0
0
0
0
0
68
80
97
96
9
10
11
12
13
14
15
Cyclohexane
Water–ethanol (1 : 14)c
Water–ethanol (3 : 12)c
Water–ethanol (6 : 9)c
Water–ethanol (9 : 6)c
Water–ethanol (12 : 3)c
a
Reactions were carried out with 4-chlorobenzaldehyde (1 mmol), malononitrile (1 mmol) and a-naphthol (1 mmol) in the presence of PANDMAP
F
(0.2700 g, containing 0.20 mmol of effective group) in different solvents (15 mL of each) under reux for 1 h. b Isolated yield aer recrystallization
with ethanol. c The proportion is a volume ratio. d Calculated value.
yield when the time was increased from 10 to 60 min. No further adhered onto the PANDMAPF. The ber catalyst was then reused
increase in yield was observed if longer reaction times were directly in the next cycle without any additional treatment. The
applied. So 60 min of reux was chosen as the optimal reaction yields were 97%, 96%, 97%, 97%, 91%, 81%, 80% for the rst
time for the condensation reaction.
seven cycles respectively. The decrease in the sixth and seventh
cycle may be due to the deactivation of catalyst which was
caused by the accumulation of micromolecules on the surface.
Nevertheless, compared to homogeneous catalysts2,3,23,24 and
other heterogeneous catalysts,4,25 this new ber catalyst has
3.5 Recyclability of PANDMAPF
PANDMAPF was reused for the three-component reaction to test
its recyclability. Aer each run, the ber catalyst was ltered out
and washed with ethanol to remove any residue that had
advantages of
recyclability.
a
simple work-up procedure and good
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Table 5 Three-component condensation reaction
Entry
R
mp (ꢁC)
Lit. mp (ꢁC)
Yielda,b (%)
1
2
3
4
5
6
7
8
H
p-Cl
p-F
208–210
237–239
224–225
210–211
182–184
232–233
188–189
212–213
236–238
242–244
239–241
211–212
231–232
230–232
210–212
182–183
—
93
97
88
98
96
96
88
99
89
98
80
m-NO2
p-OCH3
m-OCH3
o-OCH3
m-CF3
o-CF3
m-OH
p-OH
204
215.5–216.5
239–240
250–253
245–247
Fig. 3 Effect of catalyst amount on the three-component conden-
sation reaction with 4-chlorobenzaldehyde (1 mmol), malononitrile
(1 mmol) and a-naphthol (1 mmol).
9
10
11
a
Reactions were carried out with aldehyde (1 mmol), malononitrile
(1 mmol) and a-naphthol (1 mmol) in the presence of PANDMAP
F
(0.2700 g, containing 0.20 mmol of effective group) in different
b
solvents (15 mL of each) under reux for 1 h. Isolated yield aer
recrystallization with ethanol.
2-Amino-4-(4-chlorophenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 2). 1H NMR (600 MHz, DMSO) d 8.25 (d, J ¼
8.2 Hz, 1H), 7.90 (d, J ¼ 7.7 Hz, 1H), 7.76–7.52 (m, 3H), 7.38 (t, J ¼
15.2 Hz, 2H), 7.34–7.19 (m, 4H), 7.10 (d, J ¼ 8.4 Hz, 1H), 4.96
(s, 1H).
2-Amino-4-(4-uorophenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 3). 1H NMR (600 MHz, DMSO) d 8.24 (d, J ¼
8.2 Hz, 1H), 7.90 (d, J ¼ 7.8 Hz, 1H), 7.62 (m, J ¼ 20.1, 14.8, 7.0
Hz, 3H), 7.29 (m, 2H), 7.21 (s, 2H), 7.15 (m, J ¼ 8.3 Hz, 2H), 7.11
(d, J ¼ 8.4 Hz, 1H), 4.96 (s, 1H).
2-Amino-4-(3-nitrophenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 4). 1H NMR (600 MHz, DMSO) d 8.27 (d, J ¼
8.4 Hz, 1H), 8.19 (m, 2H), 7.92 (d, J ¼ 8.1 Hz, 1H), 7.76 (d, J ¼ 7.6
Hz, 1H), 7.70–7.58 (m, 4H), 7.36 (s, 2H), 7.17 (d, J ¼ 8.5 Hz, 1H),
5.22 (s, 1H).
Fig. 4 Effect of reaction time on the three-component condensation
reaction with 4-chlorobenzaldehyde (1 mmol), malononitrile (1 mmol)
and a-naphthol (1 mmol).
2-Amino-4-(4-methoxyphenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 5). 1H NMR (600 MHz, DMSO) d 8.24 (d, J ¼ 8.4
Hz, 1H), 7.87 (d, J ¼ 23.5, 7.0 Hz, 1H), 7.69–7.48 (m, 3H), 7.17 (d, J
¼ 8.6 Hz, 2H), 7.14 (s, 2H), 7.09 (d, J ¼ 8.5 Hz, 1H), 6.89 (d, J ¼ 13.2
Hz, 2H), 4.85 (s, 1H), 3.71 (s, 3H).
3.6 Extension of the substrate
PANDMAPF was then applied to different kinds of aromatic
aldehydes (Table 5) and the condensation products were
obtained in excellent yields ranging from 80% to 99%.
Relatively low yields were obtained for entries 7 and 9
because of steric effects. The lower yield for entry 11 is
because of the protonation of the hydroxyl group on the
benzene ring or the quinoid transformation of the molecular
structure.
2-Amino-4-(3-methoxyphenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 6). 1H NMR (600 MHz, DMSO) d 8.24 (d, J ¼ 8.4
Hz, 1H), 7.88 (d, J ¼ 8.1 Hz, 1H), 7.65–7.54 (m, J ¼ 14.7, 12.6, 7.4
Hz, 3H), 7.20 (m, 1H), 7.16–7.09 (m, 3H), 7.08–6.99 (m, 2H), 6.88 (t,
J ¼ 7.4 Hz, 1H), 5.26 (s, 1H), 3.81 (s, 3H).
1H data for selected compounds are given below:
2-Amino-4-(2-methoxyphenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 7). 1H NMR (600 MHz, DMSO) d 8.24 (d, J ¼ 8.4
Hz, 1H), 7.88 (d, J ¼ 8.1 Hz, 1H), 7.65–7.54 (m, J ¼ 14.7, 12.6, 7.4
Hz, 3H), 7.20 (m, 1H), 7.15–7.09 (m, 3H), 7.04 (m, 2H), 6.88 (t, J ¼
7.4 Hz, 1H), 5.26 (s, 1H), 3.81 (s, 3H).
2-Amino-4-phenyl-4H-benzo[h]chromene-3-carbonitrile (Table 5,
entry 1). 1H NMR (600 MHz, DMSO) d 8.25 (d, J ¼ 8.3 Hz, 1H), 7.85
(t, J ¼ 40.6 Hz, 1H), 7.77–7.44 (m, 3H), 7.32 (t, J ¼ 7.2 Hz, 2H),
7.29–7.16 (m, 5H), 7.12 (d, J ¼ 8.4 Hz, 1H), 4.91 (s, 1H).
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2-Amino-4-(3-(triuoromethyl)phenyl)-4H-benzo[h]chromene-
3-carbonitrile (Table 5, entry 8). 1H NMR (600 MHz, DMSO) d
8.27 (d, J ¼ 8.3 Hz, 1H), 7.91 (d, J ¼ 8.0 Hz, 1H), 7.61 (m, J ¼ 29.9,
20.9, 11.0 Hz, 7H), 7.31 (s, 2H), 7.14 (d, J ¼ 8.4 Hz, 1H), 5.13
(s, 1H).
Notes and references
1 D. Armesto, W. M. Horspool, N. Martin, A. Ramos and
C. Seoane, J. Org. Chem., 1989, 54, 3069.
2 A. T. Khan, M. Lal, S. Ali and M. M. Khan, Tetrahedron Lett.,
2011, 52, 5327.
3 J. M. Khurana, B. Nand and P. Saluja, Tetrahedron, 2010, 66,
5637.
4 D. Kumar, V. B. Reddy, B. G. Mishra, R. K. Rana,
M. N. Nadagouda and R. S. Varma, Tetrahedron, 2007, 63,
3093.
5 W. Steglich and G. Hoee, Angew. Chem., Int. Ed. Engl., 1969,
8, 981.
2-Amino-4-(2-(triuoromethyl)phenyl)-4H-benzo[h]chromene-
3-carbonitrile (Table 5, entry 9). 1H NMR (600 MHz, DMSO) d 8.29
(d, J ¼ 8.4 Hz, 1H), 7.90 (d, J ¼ 8.1 Hz, 1H), 7.76 (d, J ¼ 7.9 Hz,
1H), 7.67 (t, 1H), 7.60 (t, 3H), 7.44 (t, J ¼ 7.6 Hz, 1H), 7.36–7.25 (m,
3H), 6.88 (d, J ¼ 8.5 Hz, 1H), 5.21 (s, 1H).
2-Amino-4-(3-hydroxyphenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 10). 1H NMR (600 MHz, DMSO) d 9.37 (s, 1H),
8.24 (d, J ¼ 8.3 Hz, 1H), 7.90 (d, J ¼ 8.1 Hz, 1H), 7.61 (m, J ¼ 23.0,
15.0, 7.3 Hz, 3H), 7.23–7.01 (m, 4H), 6.72 (d, J ¼ 7.5 Hz, 1H), 6.61
(s, 2H), 4.79 (s, 1H).
6 L. M. Litvinenko and A. I. Kirichenko, Dokl. Akad. Nauk SSSR,
1967, 176, 197.
2-Amino-4-(4-hydroxyphenyl)-4H-benzo[h]chromene-3-carbon-
itrile (Table 5, entry 11). 1H NMR (600 MHz, DMSO) d 9.36
(s, 1H), 8.23 (d, J ¼ 8.3 Hz, 1H), 7.89 (d, J ¼ 8.0 Hz, 1H),
7.76–7.51 (m, 3H), 7.14–6.96 (m, 5H), 6.70 (d, J ¼ 8.1 Hz, 2H),
4.78 (s, 1H).
7 D. E. Bergbreiter and C. M. Li, Org. Lett., 2003, 5, 2445.
8 D. E. Bergbreiter, P. L. Osburn, T. Smith, C. M. Li and
J. D. Frels, J. Am. Chem. Soc., 2003, 125, 6254.
9 D. E. Bergbreiter, P. L. Osburn and C. M. Li, Org. Lett., 2002,
4, 737.
N,N0-Dimethyl-N-(4-pyridyl)-1,3-propanediamine. 1H NMR 10 B. P. Mason, A. R. Bogdan, A. Goswami and D. T. McQuade,
(600 MHz, DMSO) d 8.07 (d, J ¼ 3.6 Hz, 2H), 6.58 (d, J ¼ 4.5 Hz, Org. Lett., 2007, 9, 3449.
2H), 3.39 (t, J ¼ 7.0 Hz, 2H), 2.91 (s, 3H), 2.44 (t, J ¼ 6.3 Hz, 2H), 11 A. W. Miller and S. T. Nguyen, Org. Lett., 2004, 6, 2301.
2.26 (s, 3H), 1.63 (m, 2H).
12 C. Roux, M. Candy, J.-M. Pons, O. Chuzel and C. Bressy,
Angew. Chem., Int. Ed., 2014, 53, 766.
13 H. T. Chen, S. Huh, J. W. Wiench, M. Pruski and V. S. Y. Lin,
J. Am. Chem. Soc., 2005, 127, 13305.
4. Conclusions
14 K. E. Price, B. P. Mason, A. R. Bogdan, S. J. Broadwater,
J. L. Steinbacher and D. T. McQuade, J. Am. Chem. Soc.,
2006, 128, 10376.
15 J. T. Huang, Q. Wang, J. K. Yao, L. M. Zhang and J. W. Sun, J.
Appl. Polym. Sci., 1999, 71, 1101.
16 J. Lu and P. H. Toy, Synlett, 2011, 659.
17 X.-L. Shi, H. Yang, M. Tao and W. Zhang, RSC Adv., 2013, 3,
3939.
18 C. Z. Xu, J. G. Du, L. C. Ma, G. W. Li, M. L. Tao and
W. Q. Zhang, Tetrahedron, 2013, 69, 4749.
19 L. C. Ma, L. W. Yuan, C. Z. Xu, G. W. Li, M. L. Tao and
W. Q. Zhang, Synthesis, 2013, 45, 45.
20 A. A. Shunkevich, Z. I. Akulich, G. V. Mediak and
V. S. Soldatov, React. Funct. Polym., 2005, 63, 27.
21 G. Li, J. Xiao and W. Q. Zhang, Green Chem., 2011, 13, 1828.
22 G. Li, J. Xiao and W. Q. Zhang, Green Chem., 2012, 14, 2234.
23 K. Gong, H. L. Wang, J. Luo and Z. L. Liu, J. Heterocycl.
Chem., 2009, 46, 1145.
In this paper, a DMAP functionalized ber catalyst PANDMAP
F
was prepared for the rst time and was employed as a novel and
efficient catalyst for the synthesis of various substituted 2-
amino-2-chromenes using a three-component condensation
approach. The three-component reaction proceeded smoothly
in water (80–97% yield) when catalyzed by PANDMAPF, whereas
in ethanol under the same conditions, no reaction took place.
In ethanol the reaction was found to terminate aer the
formation of the Knoevenagel intermediate A. The reaction
could be turned-on by adding enough water to the reaction
system. This ber catalyst is suitable for a wide range of
aromatic aldehydes and can be easily recycled and reused up to
seven times without any additional treatment. The attractive
features of this ber catalyst make it be an excellent choice for
the green synthesis of 2-amino-2-chromenes.
Acknowledgements
24 M. G. Dekamin, M. Eslami and A. Maleki, Tetrahedron, 2013,
69, 1074.
25 R. Maggi, R. Ballini, G. Sartori and R. Sartorio, Tetrahedron
Lett., 2004, 45, 2297.
The authors thank the Natural Science Foundation of China
(no. 21306133) and Tianjin Research Program of Application
Foundation and Advanced Technology (no. 14JCYBJC22600) for
their nancial support.
26128 | RSC Adv., 2014, 4, 26122–26128
This journal is © The Royal Society of Chemistry 2014