Efficient preparation of some new 1-carbamato-alkyl-2-naphthols using N-halo reagents in neutral media

Article abstract of DOI:10.1039/c3ra45036h

A new and simple procedure for the synthesis of some new 1-carbamato-alkyl-2-naphthol derivatives via one-pot three-component condensation of arylaldehydes, 2-naphthol, and benzylcarbamate in the presence of catalytic amounts of 1,3,5-trichloro-1,3,5-tria

Full text of DOI:10.1039/c3ra45036h

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Efficient preparation of some new 1-carbamato-
alkyl-2-naphthols using N-halo reagents in neutral
media†
Cite this: RSC Adv., 2014, 4, 1388
a
a
b
*
*
Ardeshir Khazaei, Fatemeh Abbasi and Ahmad Reza Moosavi-Zare
Received 11th September 2013
Accepted 12th November 2013
A new and simple procedure for the synthesis of some new 1-carbamato-alkyl-2-naphthol derivatives via
one-pot three-component condensation of arylaldehydes, 2-naphthol, and benzylcarbamate in the
presence of catalytic amounts of 1,3,5-trichloro-1,3,5-triazinane-2,4,6-trione (TCCA) and 1,3-dichloro-
5,5-dimethylhydantoin (DCDMH) under solvent-free conditions is described.
DOI: 10.1039/c3ra45036h
www.rsc.org/advances
Multi-component reactions (MCRs) play an interesting role in friendly method accompanied with higher yields is still needed.
combinatorial chemistry due to the ability to synthesize target Moreover, limited protocols have reported on the replacement
products with greater efficiency and atom economy by forming of amide with benzylcarbamate.24–28
structural complexity in a single step from three or more reac-
tants. Moreover, MCRs offer advantages of simplicity and inexpensive, low toxicity, easily available reagent, has been
synthetic efficiency over conventional chemical reactions.1–3 widely used in organic transformations.29 1,3-dichloro-5,5-
Trichloro-1,3,5-triazinane-2,4,6-trione (TCCA) (Fig. 1), an
1-Amidoalkyl-2-naphthols and 1-carbamatoalkyl-2-naph- dimethylhydantoin (DCDMH) (Fig. 1) is a stable, low cost and
thols are of importance as they can be easily converted to 1- commercially available heterocycle which has rarely used as a
aminoalkyl-2-naphthol derivatives by hydrolysis, which are source of chlorine ion or radical in chlorination30,31 or oxidation
biologically important compounds. 1-Aminoalkyl-2-naphthols reactions.32,33 But, as our knowledge, there are no reports of
have been applied as hypotensive and bradycardiac agents.4,5 1- catalytic application of DCDMH and TCCA in the synthesis of 1-
Amidoalkyl-2-naphthols can be also converted to 1,3-oxazine carbamato-alkyl-2-naphthols until now.
derivatives.6 Several pharmaceutical properties have been
reported for 1,3-oxazines, e.g., antibiotic,7 antitumor,8 and DCDMH and TCCA as homogenous and neutral catalysts in the
analgesic activities.9
preparation of 1-carbamato-alkyl-2-naphthols by one-pot, three-
Herein, we were interested to examine the catalytic activity of
The synthesis of 1-amidoalkyl-2-naphthols can be carried out component coupling of 2-naphthol, aromatic aldehydes, and
by multi-component condensation reaction of 2-naphthol, benzylcarbamate (Scheme 1).
aromatic aldehydes, and acetonitrile or various amides in the
presence of different catalysts such as p-toluenesulfonic acid,10 bis (1-carbamatoalkyl-2-naphthol)s (Scheme 2).
sulfamic acid/ultrasound,11 oxalic acid,12 Fe(HSO4)3,13
First of all, to optimize the reaction conditions (amount of
H3PMo12
40$xH2O/SiO2,14 trityl chloride,15,16 sulfonic acid catalysts and temperature), the reaction of 2-naphthol (1 mmol),
Moreover, TCCA and DCDMH can catalyze the synthesis of
O
functionalized imidazolium salt,17 iodine,18 silica-supported benzaldehyde (1 mmol) and benzylcarbamate (1.1 mmol) was
perchloric acid,19 NaHSO4$H2O,20 Bi(NO3)3$5H2O,21 supported selected as a model reaction, and its behavior was studied in the
ionic liquid catalyst (SILC),22 SnCl4$5H2O.23 However, some of presence of different amounts of catalysts (TCCA and DCDMH)
the reported methods are associated with one or more of the under thermal solvent-free conditions. The results are
following disadvantages such as low yield, long reaction time, summarized in Tables 1 and 2. As Tables 1 and 2, indicates that
toxic and corrosive solvent, strong acidic media, high reaction
ꢀ
temperature (>100 C) and using of toxic, corrosive, expensive
and large amount catalysts. Because of the importance of these
compounds, the improvement of a milder, faster, and more eco-
aFaculty of Chemistry, Bu-Ali Sina University, Hamedan 6517838683, Iran. E-mail:
Khazaei_1326@yahoo.com; Fax: +98 8118257407
bDepartment of Chemistry, University of Sayyed Jamaleddin Asadabadi, Asadabad,
6541835583, Iran. E-mail: moosavizare@yahoo.com
† Electronic supplementary information (ESI) available. See DOI:
Fig. 1 The structure of trichloro-1,3,5-triazinane-2,4,6-trione (TCCA)
10.1039/c3ra45036h
and 1,3-dichloro-5,5-dimethylhydantoin (DCDMH).
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Table
3
Preparation of 1-carbamato-alkyl-2-naphthols from 2-
naphthol, aromatic aldehydes and benzylcarbamate using TCCA and
DCDMH at 80 ꢀ
C
Time (min)/ Time (min)/
Yielda (%)
(TCCA)
Yielda (%)
(DCDMH)
Entry
R
M.p. ꢀC (Lit.)
1a
2a
3a
4a
5a
6a
7a
8a
C6H5
4/87
2/93
2/90
3/92
3/89
4/84
5/89
7/83
7/88
16/87
4/90
5/81
5/80
11/85
4/86
16/79
9/80
18/76
30/58
25/72
35/47
180–182 (180–182)27
198–200 (208–210)26
196–197 (200–202)26
200 (202–204)26
214–216 (211–213)26
183–185
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
2-ClC6H4
3-ClC6H4
4-ClC6H4
2,4-diClC6H3 2/90
4-FC6H4
4-BrC6H4
1-C10H7
4-CH3C6H4
Scheme 1 The synthesis of 1-carbamato-alkyl-2-naphthols.
176–177 (178–180)26
202–204 (208–210)26
202–203
9a
3/84
4/88
10/80
15/60
10a
11a
12a
13a
14a
180–182
214–217
152–154
202–204
2-OCH3C6H4 7/78
4-OCH3C6H4 30/50
165–167
a
Isolated yield.
DCDMH at 80 ꢀC under solvent-free condition. The correspond-
ing results are displayed in Table 3. As it can be seen in Table 3,
the reactions were carried out efficiently within 2–35 min, and the
most desired products were produced in high to excellent yields.
Thus, TCCA and DCDMH are highly efficient, general and mild
organic catalysts for the preparation of 1-carbamato-alkyl-2-
naphthols. The inuence of electron-releasing substituents,
electron-withdrawing substituents and halogens on the aromatic
ring of arylaldehydes on the reaction results was investigated. As
Table 3 indicates, electron-withdrawing substituents and halo-
gens had no signicant effect on the yields, and arylaldehydes
bearing these substituents were reacted faster than benzaldehyde
(entries 2a–10a, products which were prepared using TCCA);
however, electron-releasing groups decreased the yields and
increased the reaction times (entries 12a–14a).
Scheme 2 The synthesis of bis(1-carbamatoalkyl-2-naphthol)s.
Table 1 Optimization of the amount of TCCA and the reaction
temperature
Entry Catalyst (mol%) Temperature (ꢀC) Time (min) Yielda (%)
1
2
3
4
5
5
10
15
10
10
80
80
80
70
90
4
4
4
5
7
83
87
72
79
87
a
Isolated yield.
Our method also worked well when 2-naphthol was reacted
with bis-aldehyde (terephthaldehyde) and benzylcarbamate in
the presence of 10 mol% of TCCA and DCDMH (Scheme 2). The
use of 1 equiv. of 2-naphthol, 1 equiv. of terephthalaldehyde
and 1.1 equiv. of benzylcarbamate in the reaction afforded 1-
carbamato-alkyl-2-naphthol (1b) and bis(carbamato-alkyl-2-
naphthol) (2b) in 82 : 11% in 3 min and 77 : 18% in 19 min for
TCCA and DCDMH, respectively. However, the condensation of
2 equiv. of 2-naphthol with 1 equiv. of the aldehyde and 2.2
equiv. of benzylcarbamate gave compounds 1b:2b in 67 : 29%
in 2 min and 61 : 35% in 17 min for TCCA and DCDMH,
respectively. For the synthesis of bis(1-carbamatoalkyl-2-naph-
thol) (2b), increase the amount of catalyst to 20 mol%, due to
two formyl groups in terephthaldehyde, did not improve the
corresponded time and yield.
Table 2 Optimization of the amount of DCDMH and the reaction
temperature
Entry Catalyst (mol%) Temperature (ꢀC) Time (min) Yielda (%)
1
2
3
4
5
5
10
15
10
10
80
80
80
70
90
4
4
4
5
7
78
83
68
75
83
a
Isolated yield.
higher yield and shorter reaction time were obtained using 10
ꢀ
mol% of catalysts at 80 C under solvent-free conditions.
To assess the efficiency and the scope of the organic catalyst in
the preparation of 1-carbamato-alkyl-2-naphthols, the conden-
sation of 2-naphthol with various arylaldehydes and benzylcar-
bamate was examined in the presence of 10 mol% of TCCA and
To show the advantage, applicability and efficiency of TCCA
and DCDMH over the reported catalysts for the synthesis of 1-
carbamatoalkyl-2-naphthols from benzaldehyde, b-naphthol
and benzylcarbamte, we have compared results and turn-over
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Fig. 2 IR spectra of benzaldehyde and mixture of benzaldehyde and
DCDMH.
generation of Cl+ from the catalysts, the reaction is catalyzed.
So, in a proposed reaction mechanism which supported by the
literature,29,34–36 we suggest that aldehyde and catalysts (TCCA or
DCDMH) produce intermediate I and II (Scheme 3). Then, 2-
naphthol attacks to I and II to give intermediates III. Interme-
diate III converts to IV aer tautomerisation. Finally, one
molecule of benzylcarbamate attacks to IV and by removing one
molecule H2O in this step, the corresponded product and
catalyst are obtained.
In another investigation, to conrm that HCl could not
produce from TCCA and DCDMH to catalyze the reaction, the
model reaction was performed in the presence of hydrochloric
acid (10% and 20%). As it shown of Table 4, indicates that TCCA
and DCDMH were more effective than HCl to catalyze the reaction.
To prove the formation of intermediate I and II, benzalde-
ꢀ
hyde was reacted with catalysts at 80 C, and then IR and UV
Scheme 3 The plausible mechanism for the synthesis of 1-carbama-
toalkyl-2-naphthols catalyzed by TCCA and DCDMH.
Table 4 Comparison result of TCCA and DCDMH with other reported
catalysts in the synthesis of benzyl (2-hydroxynaphthalen-1-yl)(phenyl)
methylcarbamate at 80 ꢀ
C
Catalyst
(mol%)
Time
(min)
Yielda
(%)
TOF
Catalyst
(minꢂ1 b
)
Ref.
c
TCCA
10
10
2
4
7
36
9
87
83
85
84
2.175
1.185
1.180
0.93
—
c
DCDMH
Al(MS)3.4H2O
[(CH2)4SO3HPy]
[HSO4]d
HCl
—
26
27
10
c
10
20
300
300
30
35
0.01
0.005
—
c
HCl
—
a
Isolated yield. b Turn-over frequency. c Our work. d N-(4-sulfonic acid)
butylpyridinium hydrogen sulfate.
frequency (TOF ¼ yield (%)/[reaction time (min) ꢁ mol% of
catalyst]) of our catalysts with other reported catalysts. As shown
in Table 4, TCCA and DCDMH can act as effective catalysts with
respect to reaction times and yields of the obtained products.
Since TCCA and DCDMH contain chlorine atoms which
Fig. 3 UV spectra of benzaldehyde, TCCA, DCDMH and complexes of
bonded to nitrogen atoms in heterocyclic ring. By in situ benzaldehyde and Cl+ (I and II) at 80 ꢀC in dichloromethane.
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aldehydes and benzylcarbamate using trichloroisocyanuric acid
(TCCA) and 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as
ꢀ
homogenous organic catalysts at 80 C under solvent-free and
neutral conditions.37 Moreover, bis (1-carbamatoalkyl-2-naph-
thol)s have synthesized under these reaction conditions.38 The
advantages of the presented method are efficiency, generality,
high yield, short reaction time, cleaner reaction prole, and
simplicity.
Acknowledgements
The authors acknowledge to Bu-Ali Sina University Research
Councils, Center of Excellence in Development of Chemistry
Methods (CEDCM) and National Foundation of elites (BMN) for
support of this work.
Notes and references
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IR (Nujol): ymax (cmꢂ1) of C]O in benzaldehyde (1703)
decreased to 1682 in the reaction mixture (Fig. 2).
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(I and II). UV studies were performed in dichloromethane as
solvent. The maximum of absorption for benzaldehyde appear
at 243 nm and for TCCA at 234 nm and DCDMH at 231 nm. But
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compounds and then react with 2-naphthol to give III, which
reacts with benzylcarbamate to produce 1-carbamato-alkyl-2-
naphthols. To investigate that the catalyst was completely
recovered during the reaction and proceeded the synthesis of 1-
carbamatoalkyl-2-naphthols; we have recorded the UV spectra
of the catalyst and reaction mixture in dichloromethane as
solvent respectively. We have exactly observed the maximum of
absorption for the catalysts in UV spectrum of the reaction
mixture. Based on, it is clear that TCCA and DCDMH was
recovered unchanged aer the completion of the reaction
(Fig. 4) and the proposed mechanisms were acceptable.
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NMR (90 MHz, DMSO-d6): d (ppm) 5.09 (2H), 6.94–8.12
(17H), 10.23 (s, 1H, OH); 13C NMR (22.5 MHz, DMSO-d6): d
(ppm) 50.26, 65.82, 117.80, 118.46, 120.50, 121.38, 122.60,
126.82, 127.57, 127.67, 128.24, 128.61, 129.57, 129.86,
131.91, 132.71, 144.99, 153.11, 156.28; IR (KBr, cmꢂ1):
3389, 3352, 1694, 1629, 1527, 1514, 1438, 1348, 1333,
1276, 1233, 1142, 1048, 1016, 922, 830, 810, 743, 624.
Benzyl(3-chlorophenyl) (2-hydroxynaphthalen -1-yl) methyl-
carbamate 6a: white solid; Rf (EtOAc/n-hexane: 4/6) ¼ 0.65;
m.p. 183–185 ꢀC ; 1H NMR (90 MHz, DMSO-d6): d (ppm)
5.09 (2H), 6.88-8.00 (17H), 10.19 (s, 1H, OH); 13C NMR
(22.5 MHz, DMSO-d6): d (ppm) 50.35, 65.82, 118.27, 118.52,
122.61, 124.77, 125.83, 126.34, 126.73, 127.55, 128.24,
128.45, 128.58, 129.59, 129.86, 131.99, 132.98, 136.89,
145.10, 153.00, 155.96; IR (KBr, cmꢂ1): 3435, 3241, 1675,
1629, 1575, 1507, 1439, 1327, 1271, 1227, 1064, 947,
892, 813, 784, 754, 702. Benzyl (2,4-dichlorophenyl)
(2-hydroxynaphthalen-1-yl) methylcarbamate 8a: white
solid; Rf (EtOAc/n-hexane: 4/6) ¼ 0.60; m.p. 202–204 ꢀC
(ref. 26 mp 208–210 ꢀC); 1H NMR (90 MHz, DMSO-d6): d
(ppm) 5.05 (2H), 6.87–8.06 (16H), 9.94 (s, 1H, OH); 13C
NMR (22.5 MHz, DMSO-d6): d (ppm) 49.66, 65.53, 116.46,
118.66, 122.51, 126.50, 127.36, 127.59, 128.20, 128.56,
129.67, 131.19, 132.05, 132.55, 133.29, 137.06, 138.76,
153.59, 155.47; IR (KBr, cmꢂ1): 3417, 3343, 3031, 1678,
1628, 1585, 1513, 1432, 1341, 1271, 1139, 1054, 936, 878,
844, 744.
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38 General procedure for the condensation between 2-
naphthol, terephthaldehyde and alkyl carbamates:
A
mixture of 2-naphthols (0.288 g, mmol),
2
35 S. Habibzadeh and H. Ghasemnejad-bosra, J. Chin. Chem.
Soc., 2001, 58, 1.
terephthaldehyde (0.268g, 2 mmol or 0.134g, 1 mmol),
benzylcarbamate (0.320g, 2.2 mmol) and (0.0464g TCCA or
0.0394g DCDMH, 0.2 mmol, 10 mol%), in a 10 mL round-
bottomed ask, was stirred in an oil-bath (80 ꢀC). Aer
completion of the reaction, as monitored by TLC, The
reaction was cooled to room temperature, washed with hot
water. Aerward, warm aqueous ethanol (15%, 30 mL) was
added to crude products, and stirred for 10 min
(1-carbamato-alkyl-2-naphthol 1b is soluble in warm
aqueous ethanol and bis(1-amidoalkyl-2-naphthol) 2b is
insoluble in this solvent). During this time, the crude
1-carbamato-alkyl-2-naphthol 1b was dissolved in the
aqueous ethanol, and the pure bis(1-amidoalkyl-2-
naphthol) 2b was remained. Thus, bis (1-amidoalkyl-2-
naphthol) 2b was easily separated by ltration and pure
1-carbamato-alkyl-2-naphthol (1b) was recrystallized from
EtOH(95%).
36 S. F. Hojati, M. Gholizadeh, M. Haghdoust and
F. Shaezadeh, Bull. Korean Chem. Soc., 2010, 31, 3238.
37 General procedure for the synthesis of 1-carbamato-alkyl-2-
naphthol derivatives: a mixture of 2-naphthols (0.288g, 2
mmol), aldehydes (2 mmol), benzylcarbamate (.320 g, 2.2
mmol) and (0.0464g TCCA or 0.0394g DCDMH, 0.2 mmol,
10 mol%), in a 10 mL round-bottomed ask sealed with a
stopper, was stirred in an oil-bath (80 ꢀC). Aer
completion of the reaction, as monitored by TLC, The
reaction was cooled to room temperature, washed with hot
water and the pure solid products (compounds 1a–14a)
were obtained by recrystallization from ethanol (95%).
Benzyl
(2-hydroxynaphthalen-1-yl)(3-nitrophenyl)-
methylcarbamate 3a: yellow solid; Rf (EtOAc/n-hexane:
4/6) ¼ 0.50; m.p. 196–197 ꢀC (ref. 26 mp 200–202 ꢀC); 1H
1392 | RSC Adv., 2014, 4, 1388–1392
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