Evaluation of catalytic activity of two newly prepared functionalized sulfonic acids ionic liquids in the synthesis of carbamatoalkyl naphthols under mild conditions

Article abstract of DOI:10.1134/S1070363217020268

Catalytic activity of two newly prepared functionalized sulfonic acids ionic liquids, [MPyrrSO₃H]Cl (IL₁) and [MMorSO₃H]Cl (IL₂), is studied in one-pot three-component synthesis of carbamatoalkyl naphthols by th

Full text of DOI:10.1134/S1070363217020268

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 2, pp. 311–315. © Pleiades Publishing, Ltd., 2017.
Evaluation of Catalytic Activity of Two Newly Prepared
Functionalized Sulfonic Acids Ionic Liquids in the Synthesis
of Carbamatoalkyl Naphthols under Mild Conditions1
M. Dehghan, A. Davoodnia*, M. R. Bozorgmehr, and F. F. Bamoharram
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, 91735-413 Iran
*e-mail: adavoodnia@mshdiau.ac.ir; adavoodnia@yahoo.com
Received September 26, 2016
Abstract—Catalytic activity of two newly prepared functionalized sulfonic acids ionic liquids, [MPyrrSO3H]Cl
(IL1) and [MMorSO3H]Cl (IL2), is studied in one-pot three-component synthesis of carbamatoalkyl naphthols
by the reaction of β-naphthol with aromatic aldehydes and methyl or benzyl carbamate. The efficiently
catalyzed reaction proceeded under solvent-free conditions. The synthesis was characterized by easy work-up,
absence of volatile and hazardous organic solvents, and recyclability of the catalysts.
Keywords: sulfonic acid functionalized ionic liquids, carbamatoalkyl naphthols, solvent-free synthesis
DOI: 10.1134/S1070363217020268
INTRODUCTION
involved one-pot three-component reaction of β-naphthol
with aromatic aldehydes and methyl or benzyl
carbamate under solvent-free conditions (Scheme 1).
Carbamatoalkyl naphthols can be synthesized by a
multi-component reaction (MCR) [1–5] and converted
further to biologically active 1-aminomethyl-2-naphthol
derivatives by carbamate hydrolysis. The hypotensive
and bradycardiac effects of the latter compounds have
been evaluated [6, 7]. A number of methods has been
developed for the synthesis of carbamatoalkyl
naphthols [8–18] each of which possessed some
advantages. Nevertheless, development of new efficient
recyclable catalysts for the synthesis of carbamatoalkyl
naphthols was of certain demand. Over recent years,
Brønsted acidic ionic liquids (IL) [19–21] received
close attention as environmentally friendly catalysts.
Initially, catalytic activity of IL1 and IL2 was
optimized in the synthesis of methyl (4-chlorophenyl)-
(2-hydroxynaphthalen-1-yl)methylcarbamate 4b via
the reaction of β-naphthol (1 mmol) with 4-chloro-
benzaldehyde (1 mmol) and methyl carbamate
(1.1 mmol) (Table 1). A non-catalyzed reaction was
tested under solvent-free conditions but without a
significant yield (entry 1). On the contrary, the reaction
catalyzed by IL1 or IL2 under solvent-free conditions
demonstrated enhanced rate of formation of 4b. The
best result was achieved at 100°C in the presence of
10 mol % of IL1 or IL2 (entry 9). The test of various
media, EtOH, MeOH, CH2Cl2, CH3CN, and solvent
free, in the presence of 10 mol % of IL1 or IL2
exhibited solvent-free conditions to be the most
favorable.
In conjunction with our interest in ILs, recently,
two new functionalized sulfonic acids ILs, 1-methyl-1-
sulfonic acid pyrrolidinium chloride [MPyrrSO3H]Cl
(IL1) and 4-methyl-4-sulfonic acid morpholinium
chloride [MMorSO3H]Cl (IL2) (see figure), were
synthesized [22]. The new recyclable ILs demonstrated
high catalytic activity in the synthesis of 1,8-dioxo-
octahydroxanthenes. Following our earlier studies of
new environmental friendly methods of synthesis of
organic compounds based on reusable catalysts
[23–26], we present application of the above ILs in the
synthesis of carbamatoalkyl naphthols. The process
O
N
N
Me
SO3H
Me
SO3H
Cl
[MPyrrSO3H]Cl (IL1)
Cl
[MMorSO3H]Cl (IL2)
1 The text was submitted by the authors in English.
Structures of IL1 and IL2.
311

312
DEHGHAN et al.
Scheme 1.
Ar
NHCO2R
OH
OH
IL1 or IL2
H2NCO2R
+ ArCHO
+
Solvent-free
100 °C
1
2
3
4a−4o
Ar = 2-ClC6H4, R = Me (a), Ar = 4-ClC6H4, R = Me (b), Ar = 3-BrC6H4, R = Me (c), Ar = 4-BrC6H4, R = Me (d), Ar = 4-
MeC6H4, R = Me (e), Ar = 3-O2NC6H4, R = Me (f), Ar = 3-Pyridyl, R = Me (g, new compound), Ar = C6H5, R = Me (h), Ar =
2-ClC6H4, R = CH2C6H5 (i), Ar = 4-ClC6H4, R = CH2C6H5 (j), Ar = 3-BrC6H4, R = CH2C6H5 (k), Ar = 4-BrC6H4, R =
CH2C6H5 (l), Ar = 4-FC6H4, R = CH2C6H5 (m), Ar = 4-O2NC6H4, R = CH2C6H5 (n), Ar = C6H5, R = CH2C6H5 (o).
The optimized reaction conditions were applied to
the reaction of various aromatic aldehydes with β-
naphthol and methyl or benzyl carbamate (Table 2). In
all cases the products were isolated in high yields
within short reaction time. Melting points, TLC and
spectroscopic data (for selected products) indicated
that only one product was formed in all cases. No side-
products were detected upon purification. According to
the accumulated data IL2 proved to be the better
catalyst than IL1 in terms of yield and reaction time.
ILs could be recovered from the reaction mixtures
by cooling to room temperature, adding warm distilled
water, filtration and evaporation of water from the
filtrate. The residual ionic liquid was repeatedly
washed with diethyl ether and dried under vacuum at
60°C. The recycled catalyst could be used in four
cycles to follow (IL1 : IL2 catalysts, yields, %: 96 : 98,
96 : 97, 94 : 95, 93 : 93 and 92 : 93).
Table 1. Optimization of conditions for synthesis of 4b
catalyzed by IL1 or IL2
a
Time,
min
IL1 : IL2
Entry Catalyst,
T, °C
IL1 : IL2
Yieldb, %
IL1 : IL2
Solvent
no.
mol %
1
2
–
5
–
100
80
60 : 60 Trace : Trace
–
7 : 5
4 : 3
6 : 5
6 : 5
4 : 3
4 : 2
7 : 6
3 : 2
4 : 2
8 : 6
6 : 3
7 : 4
58 : 66
71 : 74
70 : 72
69 : 74
84 : 89
80 : 85
75 : 79
96 : 98
88 : 92
70 : 74
88 : 92
85 : 88
52 : 69
54 : 70
53 : 58
63 : 70
Although the reaction mechanism was not studied,
the speculative one may be presented (Scheme 2).
Ortho-quinone methide (o-QM) intermediate [II]
readily forms in situ by the Knoevenagel condensation
of β-naphthol 1 and an aromatic aldehyde 2 via the
intermediate 2*. The subsequent Michael addition of
methyl or benzyl carbamate to the o-QM intermediate
2* can lead to the final products 4. We believe that the
catalysts, IL1 and IL2 ≡ HA, could act as Brønsted
acids and promote the reaction by increasing the
electrophilic character of the carbonyl groups in
aldehydes and o-QM intermediate 2*. However, under
the reaction conditions used, the intermediates were
not detected.
3
5
–
100
110
80
4
5
–
5
7
–
6
7
–
100
110
80
7
7
–
8
10
10
10
15
15
15
15
15
15
15
–
9
–
100
110
80
10
11
12
13
14
15
16
17
–
–
–
100
110
–
EXPERIMENTAL
EtOH
Reflux 40 : 30
IL1 and IL2 were synthesized according to the
earlier method [22]. All chemicals were purchased
from Merck and Aldrich and used without purification.
Melting points were measured on a Stuart SMP3
melting point apparatus. IR spectra were recorded on a
MeOH Reflux 45 : 30
CH2Cl2 Reflux 50 : 40
CH3CN Reflux 40 : 30
1
a
Tensor 27 Bruker spectrophotometer in KBr disks. H
Reaction conditions: β-naphthol (1 mmol), 4-chlorobenzaldehyde
(1 mmol) , and methyl carbamate (1.1 mmol). b Isolated yields.
and 13C NMR spectra were measured on a Bruker 300
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 2 2017

EVALUATION OF CATALYTIC ACTIVITY
313
Scheme 2.
H2NCO2R
3
AH
Ar
HA
O
Ar
NHCO2R
OH
Ar
Ar
H
OH
H
O
O
2
−H2O
HA
OH
1*
2*
4a−4o
1
FT spectrometer in DMSO-d6 using TMS as the internal
standard.
aldehyde) was added. The mixture was heated on the
oil bath at 100°C for 2–5 min. The reaction was
monitored by TLC. Upon completion, the reaction mixture
was cooled down to room temperature and warm
distilled water was added. The product was filtered off,
washed repeatedly with warm distilled water and
recrystallized from ethanol to give carbamatoalkyl
naphthols 4a–4o. The previously known products were
General procedure for the synthesis of carba-
matoalkyl naphthols 4a-o catalyzed by IL1 and IL2.
To a mixture of β-naphthol (1 mmol), an aromatic
aldehyde (1 mmol) and methyl or benzyl carbamate
(1.1 mmol), IL1 or IL2 (10 mol % based on aromatic
Table 2. Synthesis of carbamatoalkyl naphthols 4a–4o using IL1 or IL2 as catalystsa
Yieldb, %
IL1 : IL2
mp, ºC
calculated
Time, min
IL1 : IL2
Comp. no
Ar
R
found
4a
4b
4c
4d
4e
4f
2-ClC6H4
4-ClC6H4
3-BrC6H4
4-BrC6H4
4-MeC6H4
3-O2NC6H4
3-Pyridyl
C6H5
Me
5 : 4
3 : 2
4 : 3
4 : 2
5 : 4
3 : 2
5 : 4
3 : 3
5 : 4
4 : 3
5 : 4
5 : 3
5 : 4
4 : 3
4 : 4
85 : 89
96 : 98
89 : 97
87 : 90
85 : 87
92 : 95
85 : 89
94 : 97
83 : 85
88 : 92
82 : 85
84 : 88
90 : 94
88 : 91
94 : 95
183–185
202–204
194–196
198–200
188–190
248–250
207–209
218–220
168–169
183–185
184–186
185–187
187–189
206–208
182–183
181–183 [15]
203–205 [15]
190–192 [15]
197–199 [15]
187–189 [15]
249–251 [10]
New
Me
Me
Me
Me
Me
4g
4h
4i
Me
Me
220–222 [10]
163–165 [16]
178–180 [13]
186–187 [16]
188–190 [15]
185–186 [16]
202–204 [13]
180–182 [15]
2-ClC6H4
4-ClC6H4
3-BrC6H4
4-BrC6H4
4-FC6H4
4-O2NC6H4
C6H5
CH2C6H5
CH2C6H5
CH2C6H5
CH2C6H5
CH2C6H5
CH2C6H5
CH2C6H5
4j
4k
4l
4m
4n
4o
a
Reaction conditions: β-naphthol (1 mmol), an aromatic aldehyde (1 mmol), methyl or benzyl carbamate (1.1 mmol), IL1 or IL2 (10 mol %),
100ºC, solvent-free. b Isolated yields.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 2 2017

314
DEHGHAN et al.
characterized by comparison of their melting points
with those of authentic samples and in some cases by
Benzyl (2-chlorophenyl)(2-hydroxynaphthalen-1-
yl)methylcarbamate (4i). IR spectrum, νmax, cm–1:
1
1
IR and H NMR spectra. Structure of the new product
3420 (NH), 3169 (OH), 1700 (C=O). H NMR spec-
4g was also confirmed by 13C NMR spectrum.
trum, δ, ppm: 5.05 ABq (2H, Δν = 25.3 Hz, JAB
=
12.9 Hz, CH2), 6.93 d (1H, J = 8.1 Hz, CH), 7.16 d
(1H, J = 9.0 Hz, Harom), 7.22–7.57 m (11H, Harom), 7.77
d (1H, J = 8.7 Hz, Harom), 7.82 d (1H, J = 7.8 Hz,
Methyl (2-chlorophenyl)(2-hydroxynaphthalen-1-
yl)methylcarbamate (4a). IR spectrum, νmax, cm–1:
1
3430 (NH), 3210 (OH), 1691 (C=O). H NMR spec-
Harom), 8.01 br.s (1H, NH), 8.04 d (1H, J = 8.4 Hz,
trum, δ, ppm: 3.54 s (3H, OCH3), 6.88 d (1H, J =
8.1 Hz, CH), 7.14 d (1H, J = 8.7 Hz, Harom), 7.25–7.90
m (9H, Harom, NH), 8.02 d (1H, J = 8.7 Hz, Harom), 9.94
s (1H, OH).
Harom), 9.94 s (1H, OH).
Benzyl (4-chlorophenyl)(2-hydroxynaphthalen-1-
yl)methylcarbamate (4j). IR spectrum, νmax, cm–1:
1
3425 (NH), 3170 (OH), 1678 (C=O). H NMR spec-
Methyl (4-chlorophenyl)(2-hydroxynaphthalen-1-
trum, δ, ppm: 5.09 ABq (2H, Δν = 19.5 Hz, JAB
=
yl)methylcarbamate (4b). IR spectrum, νmax, cm–1:
12.6 Hz, CH2), 6.91 d (1H, J = 8.7 Hz, CH), 7.22–7.45
m (12H, Harom), 7.77–7.95 m (4H, Harom, NH), 10.19 s
(1H, OH).
1
3421 (NH), 3310 (OH), 1711 (C=O). H NMR spec-
trum, δ, ppm: 3.59 s (3H, OCH3), 6.84 d (1H, J =
8.1 Hz, CH), 7.23 d (2H, J = 8.4 Hz, Harom), 7.26–7.37
m (3H, Harom), 7.41 t (1H, J = 7.8 Hz, Harom), 7.70–7.85
m (4H, Harom, NH), 7.90 d (1H, J = 8.1 Hz, Harom),
10.16 s (1H, OH).
Benzyl (4-bromophenyl)(2-hydroxynaphthalen-1-
yl)methylcarbamate (4l). IR spectrum, νmax, cm–1:
1
3423 (NH), 3169 (OH), 1680 (C=O). H NMR spec-
trum, δ, ppm: 5.08 ABq (2H, Δν = 19.2 Hz, JAB
=
Methyl (4-bromophenyl)(2-hydroxynaphthalen-
12.6 Hz, CH2), 6.88 d (1H, J = 8.7 Hz, CH), 7.15–7.50
m (12H, Harom), 7.77–7.97 m (4H, Harom, NH), 10.17 s
(1H, OH).
1-yl)methylcarbamate (4d). IR spectrum, νmax, cm–1:
1
3419 (NH), 3198 (OH), 1683 (C=O). H NMR spec-
trum, δ, ppm: 3.58 s (3H, OCH3), 6.82 d (1H, J =
8.7 Hz, CH), 7.16 d (2H, J = 8.4 Hz, Harom), 7.22 d
(1H, J = 9.0 Hz, Harom), 7.29 t (1H, J = 7.2 Hz, Harom),
7.41 t (1H, J = 7.8 Hz, Harom), 7.47 d (2H, J = 8.4 Hz,
Harom), 7.70–7.92 m (4H, Harom, NH), 10.15 s (1H, OH).
Benzyl (2-hydroxynaphthalen-1-yl)(4-nitrophenyl)-
methylcarbamate (4n). IR spectrum, νmax, cm–1: 3422
1
(NH), 3369 (OH), 1692 (C=O). H NMR spectrum, δ,
ppm: 5.10 ABq (2H, Δν = 17.7 Hz, JAB = 12.6 Hz,
CH2), 7.00 d (1H, J = 8.4 Hz, CH), 7.24 d (1H, J =
9.0 Hz, Harom), 7.27–7.45 m (7H, Harom), 7.49 d (2H,
J = 8.7 Hz, Harom), 7.80–8.10 m (4H, Harom, NH), 8.16
d (2H, J = 8.7 Hz, Harom), 10.25 s (1H, OH).
Methyl (2-hydroxynaphthalen-1-yl)(3-nitrophenyl)-
methylcarbamate (4f). IR spectrum, νmax, cm–1: 3422
1
(NH), 3227 (OH), 1687 (C=O). H NMR spectrum, δ,
ppm: 3.61 s (3H, OCH3), 6.96 s (1H, CH), 7.23 d (1H,
J = 9.0 Hz, Harom), 7.31 t (1H, J = 7.2 Hz, Harom), 7.44 t
(1H, J = 7.5 Hz, Harom), 7.57 t (1H, J = 7.8 Hz, Harom),
7.64 d (1H, J = 7.8 Hz, Harom), 7.84 t (2H, J = 8.7 Hz,
Benzyl (2-hydroxynaphthalen-1-yl)(phenyl)methyl-
carbamate (4o). IR spectrum, νmax, cm–1: 3423 (NH),
1
3191 (OH), 1672 (C=O). H NMR spectrum, δ, ppm:
H
arom), 7.93–8.00 m (2H, Harom, NH), 8.08 d (1H, J =
5.10 ABq (2H, Δν = 21.0 Hz, JAB = 12.6 Hz, CH2),
6.95 d (1H, J = 8.7 Hz, CH), 7.15–7.45 m (13H,
8.4 Hz, Harom), 8.12 s (1H, Harom), 10.28 s (1H, OH).
H
arom), 7.77–7.87 m (3H, Harom, NH), 7.95 d (1H, J =
Methyl (2-hydroxynaphthalen-1-yl)(pyridin-3-
8.1 Hz, CH), 10.17 s (1H, OH).
yl)methylcarbamate (4g). IR spectrum, νmax, cm–1:
1
3428 (NH, OH, overlapped), 1724 (C=O). H NMR
CONCLUSIONS
spectrum, δ, ppm: 3.59 s (3H, OCH3), 6.91 d (1H, J =
8.4 Hz, CH), 7.23 d (1H, J = 8.7 Hz, Harom), 7.27–7.34
m (2H, Harom), 7.43 t (1H, J = 7.5 Hz, Harom), 7.62 d
(1H, J = 8.1 Hz, Harom), 7.78–7.88 m (3H, Harom, NH),
7.98 d (1H, J = 8.4 Hz, Harom), 8.40 d.d (1H, J = 4.6,
0.9 Hz, Harom), 8.46 d (1H, J = 1.8 Hz, Harom), 10.22 s
(1H, OH). 13C NMR spectrum, δ, ppm: 49.2, 52.2,
118.4, 118.7, 123.1, 123.2, 123.7, 127.2, 128.8, 129.1,
130.2, 132.3, 134.2, 138.2, 148.0, 153.5, 157.0.
Two newly synthesized ILs acted as recyclable
catalysts in one-pot three-component synthesis of car-
bamatoalkyl naphthols by the reaction of β-naphthol
with aromatic aldehydes and methyl or benzyl
carbamate under solvent-free conditions. The process
was characterized by easy product separation, short
reaction time, high yield, absence of hazardous organic
solvents, and reusability of the catalysts.
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EVALUATION OF CATALYTIC ACTIVITY
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13. Song, Z., Sun, X., Liu, L., and Cui, Y., Res. Chem.
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ACKNOWLEDGMENTS
The authors express their gratitude to the Islamic
Azad University, Mashhad Branch for its financial
support.
14. Wang, M., Liu, Y., Song, Z., and Zhao, S., Bull.
Chem. Soc. Ethiop., 2013, vol. 27, p. 421. doi 10.4314/
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