Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols using N,N,N',N'-tetrabromobenzene-1,3-disulfonamide

Article abstract of DOI:10.2478/s11532-010-0077-0

N,N,N,'N'-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.

Full text of DOI:10.2478/s11532-010-0077-0

Cent. Eur. J. Chem. • 8(5) • 2010 • 1086–1089
DOI: 10.2478/s11532-010-0077-0
Central European Journal of Chemistry
Efficient and solvent-free synthesis of 1-
amidoalkyl-2-naphthols using N,N,N’,N’–
tetrabromobenzene-1,3-disulfonamide
Research Article
Ramin Ghorbani-Vaghei1*, Seyedeh Mina Malaekehpour2
1Department of Organic Chemistry, Faculty of Chemistry,
Bu-Ali Sina University, 65174 Hamedan, Iran
2Department of Chemistry, Faculty of Science,
Payame Noor University, 6519949831 Hamedan, Iran
Received 5 April 2010; Accepted 21 May 2010
Abstract:
N,N,N,’N’–Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoal-
kyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.
Keywords: Amidoalkyl naphthols • TBBDA • Catalyst • Solvent-free • MCRS
© Versita Sp. z o.o.
aromatic aldehyde, and amide in the presence of a
catalyst.
1. Introduction
In recent years, ZrOCl2 [9], FeCl3•SiO2 [10],
Montmorillonite K10 [11], I2 [12], K5CoW12O40•3H2O [13],
TEBSA HSO4 [14], VB1 [15], P2O5 [16], Yb(OTf)3 Bmim
BF4 [17], CuPMo [18], NKC-9 [19], and H3Mo12O40P
[20] have been utilized, as catalysts, for this synthesis.
In continuation of our interest in the application of
N,N,N’,N’-tetrabromobenzene-1,3-disulfonamide
[TBBDA] [21] (Fig. 1) in organic synthesis [22-26] we
report here a convenient method of a one-pot synthesis
of 1-amidoalkyl-2-naphthol derivatives from various
aromatic aldehydes, β-naphthol, and urea, carried
out with high yields in the presence of TBBDA, at
room temperature, and under solvent-free conditions
(Scheme 1). This reaction is simple, green, and requires
no toxic organic solvents. The advantages of using
TBBDA as a catalyst are as follows:
Multicomponent reactions (MCRs) are a powerful and
useful synthetic tool to produce complex molecules
from simple precursors by a one-pot procedure [1].
Since they are performed without the need to isolate
any intermediate the process reduces the reaction time
and saves both energy and raw materials [2]. Therefore,
the design of novel MCRs has attracted a great deal
of attention from research groups working in the field
of medicinal chemistry, drug discovery, and materials
science [3]. Reactions such as Biginelli [4], Ugi [5], and
Manich [6] are some examples of MCRs.
Amidoalkyl naphthols are an important group of
compounds because they have been found to possess
useful biological activities. Furthermore, 1-amidoalkyl-
2-naphthols can be converted to useful and important
biological building blocks and their hydrolysis leads to
1-amino methyl 2-naphthols, compounds that exhibit
•
•
The preparation of TBBDA is easy;
Under normal conditions TBBDA is stable for
three to four months;
hypotensive
and bradycardia effects in humans
[7-8]. Thus, the synthesis of amidoalkyl naphthols is
an important and useful task in organic chemistry. A
straightforward method of synthesis of these compounds
involves a three-component condensation of β-naphthol,
•
After completion of the reaction, TBBDA can
be reused in a consecutive condensation for
five more runs.
* E-mail: rgvaghei@yahoo.com
1086

R. Ghorbani-Vaghe, S. M. Malaekehpour
(Table 1, monitored by TLC (n-hexane/acetone = 8/2)),
1,2-dichloroethane (2 mL) was added, insoluble solid
was collected by simple filtration and washed with water
(10 mL). TBBDA, soluble in dichloroethane, was
recovered after evaporation of the solvent. The pure
products were obtained by recrystallization from ethanol.
The spectral data of the new amidoalkyl naphthols are
given below.
Br2N
NBr2
S
S
O
O
O
O
TBBDA
Figure 1. N,N,N’,N’-Tetrabromobenzene-1,3-disulfonamide
O
O
NH
2.3 Characterisation of the selected data
[(4-Hydroxyphenyl)-(2-hydroxy naphthalen-1-yl)methyl]
urea entry 2. White solid; M.p.: 146-148˚C 1H NMR
(90 MHz, DMSO-d6) δ = 10.13 (s, 1H), 7.62-7.49 (m,
2H), 7.25-6.86 (m, 8H), 6.63 (s, 2H), 5.79 (s, 2H) ppm;
13 C NMR (90 MHz, DMSO-d6): δ = 157.7, 149.8, 140.1,
130.5, 129.4, 129.3, 128.3, 127.6, 127.4, 125.2, 124.7,
122.9, 122.7, 120.8, 120.0, 47.8 ppm; IR (KBr) ν = 3454,
3338, 3290, 2968, 2931, 2874, 1656, 1626, 1537, 1440,
1356, 1268, 937 cm-1. MS (m/z) = 308 (1H+).
NH2
R
OH
TBBDA (0.1 g)
Solvent-free, r.t.
NH2
H2N
OH
+
3
1
RCHO
4a-j
2
R = Ar, alkyl
Scheme 1. Synthesis
of amidoalkyl naphthols, with catalytic
amount of TBBDA, under solvent-free conditions
Table 1.Preparation of 1-amidoalkyl-2-naphthols under solvent-free
conditions
Entry
Aldehyde 2
Product
[Ref.]
Yield
(%)a
Time
(min )
[(4-Nitrophenyl)-(2-hydroxy naphthalen-1-yl)methyl]
1
urea entry 5. Yellow solid; M.p.: 163-165˚C H NMR
1
2
C6H5
4a [9]
4b -
4c [9]
4d [9]
4e -
4f [9]
4g [9]
4h [9]
4i [11]
90
88
57
50
p-(OH)C H
(90 MHz, DMSO-d6) δ = 10.26 (s, 1H), 7.97-7.73 (m,
3H),7.62-7.23 (m, 7H), 7.05 (s, 2H) 6.58 (s, 2H) ppm;
13C NMR (90 MHz, DMSO-d6): δ = 160.1, 150.1, 134.4,
132.6, 129.5, 129.2, 128.1, 127.9, 127.7, 127.2, 125.7,
123.7, 122.5, 120.8, 119.9, 49.2 ppm; IR (KBr.) ν = 3445,
3347, 3299, 3006, 2836, 1661, 1595, 1539, 1509, 1454,
1370, 1237, 999 cm-1. MS (m/z) = 339 (2H+).
3
4
5
6
7
8
9
p-(Cl)C66H44
2-ClC H
94
97
90
92
92
89
90
45
30
36
80
25
60
60
p-(NO2)6C64H4
m-(NO2)C6H4
p-(H CO)C H4
C3H3CH 6
3,4,5-(2
H3CO) C6H2
10
p-(NMe32)C6H4
4j [27]
97
30
a
All Products were characterized based on their physical properties, by
comparison with the authentic samples, and by spectroscopic methods.
3. Results and Discussion
2. Experimental Procedure
Initially, we decided to explore the role of TBBDA as
a catalyst in the synthesis of amidoalkyl naphthols
(Scheme 1). In the absence of a catalyst no amidoalkyl
naphthol was observed, even after a prolonged reaction
time. The effect of the catalyst was also studied under
various conditions. In all cases the amount of the
catalyst was crucial to a good yield and reaction rate. It
was determined that 0.1 g of the catalyst (TBBDA) was
optimal to this reaction. If less than 0.1 g of TBBDA was
used the low yields resulted, even after a long reaction
time; the yield of the products did not increase when
more than 0.1 g of TBBDA was used.
2.1 Materials and methods
Substrates, solvents, and other chemicals were
purchased from Fluka, Merck, and Aldrich chemical
companies. The progress of the reaction was
monitored by (TLC SiO2, n-hexane : acetone). IR
spectra (KBr) were recorded on a Shimadzu Fx-90
infrared spectrophotometer and the nuclear magnetic
resonance (NMR) spectra were obtained on a Jeol
90 MHz spectrometer using TMS as the internal
standard. BNBTS was prepared according to our
previously reported procedure [21].
In order to optimize the reaction conditions we
examined different molar ratios of β-naphthol, aldehyde,
urea, and TBBDA. We determined that the use of
1:1:1:1 molar ratio of benzaldehyde, β-naphthol, and
urea with 0.1 g (0.2 mmol) of TBBDA gives high yields
of 1-amidoalkyl-2-naphthols at room temperature and
under solvent-free conditions.
2.2 General procedure for the synthesis of
amidoalkyl naphthols with TBBDA in
solvent-free conditions
TBBDA (0.1 g, 0.2 mmol) was added to a mixture of
aldehyde (2 mmol), 2-naphthol (0.28 g, 2 mmol), and
urea (0.1 g, 2.2 mmol) (for solid compounds 5 drops
of CH2Cl2 was added) and the mixture was stirred at
room temperature. After completion of the reaction
In recent years, there has been an increased interest
in reactions that proceed in the absence of solvents
1087

Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols
using N,N,N’,N’–tetrabromobenzene-1,3-disulfonamide
Table 2. Comparison of efficiency various catalysts in the synthesis of amidoalkyl naphthols
Entry
Catalyst
Condition
Time(min)[h]
Yield (%)
Ref.
1
2
3
4
5
6
7
8
9
10
11
TBBDA (0.1 g)
ZrOCl2 (0.1 mmol)
Montmorillonite K10 (0.1 g)
I2 (5 mol%)
Solvent-free
ClCH2CH2Cl
Solvent-free/125◦C
ClCH2CH2Cl
Neat/125◦C
(57)
[14]
[1.5]
[12]
[4.5]
[10]
[2]
(10)
[4]
(90)
[1.5]
90
83
86
91
87
92
90
73
80
93
85
This work
[9]
[11]
[12]
[12]
[13]
[13]
[14]
[15]
[18]
[20]
I2 (5 mol%)
K5CoW12O40 .3H2O (1 mol%)
K5CoW12O40 .3H2O (1 mol%)
ClCH2CH2Cl
Neat/125◦C
[TEBSA][HSO4] (0.05 mmol)
VB1 (10 mol %)
Solvent-free/ 120◦C
Alcohol/ 80◦C
CuPMo (5 mol%)
H3Mo12O40P (0.0002)
Solvent-free/ 100◦C
Reflux/CCl4
R
NHCONH2
OH
recycling of the catalyst in the synthesis of
Table 3.The
amidoalkylnaphthols
from
2-chlorobenzaldehyde,β-
naphthol, and urea
RCHO
Br2N
NBr2
S
S
O
O
O
O
Entry
Time (min)
Yield (%)a
NH2
NH2
O
1
2
3
4
5
30
30
30
30
30
97
95
93
90
88
R
O
reagent
Br
Br
O
R
H
a Yields of isolated products
OH
TBBDA
R
because they offer decrease in pollution, low cost, and
simplicity of the process. Therefore we decided to test
this reaction using solvent-free conditions and various
ratios of the catalyst. The generality of this process
was demonstrated by the wide range of substituted
aldehydes used to synthesize amidoalkyl naphthols with
good to high yields (Table 1).
In all cases, amidoalkyl naphthols were the main
products and no by-products were observed. Aromatic
aldehydes with both the electron-withdrawing groups
and the electron-releasing groups, as well as an aliphatic
aldehyde, gave high yields of the desired products. All
products were characterized by comparison with the
authentic samples using TLC and spectral and physical
data.
O
Br
R
H
OH
O
reagent
H2O
+
TBBDA
Scheme 2. Possible mechanism for the synthesis of amido-
alkyl naphthols.
bonded to nitrogen atoms, it is possible that this catalyst
releases Br+ in situ, which can act as an electrophilic
species [21-26].Therefore, the following mechanism can
be suggested for the synthesis of amidoalkyl naphthols
(Scheme 2) [16-19].
4. Conclusions
The advantages of TBBDA over catalysts commonly
used in the synthesis of amidoalkyl naphthols from
benzaldehyde, β-naphthol and urea are shown in
Table 2.
Our experiments also determined that TBBDA is a
reusable catalyst and that after five runs its catalytic
activity is almost the same as that of a fresh catalyst.
The summary of this part of the experiment is shown in
Table3.Thefirstrun,inthepresenceofTBBDAandunder
solvent-free conditions, gave 97% yield of amidoalkyl
naphthols. The second run, with TBBDA recovered from
In conclusion, we have introduced a convenient method
of synthesis of amidoalkyl naphthols from aldehydes,
β-naphthol, and urea in the presence of catalytic
amount of TBBDA, at room temperature under solvent-
free conditions in good to high yields. The method has
the advantages of short reaction times, simplicity, easy
workup, and environmental friendliness (non-corrosive
catalyst).
the first run, gave 95% of the products. The average Acknowledgement
chemical yield for five consecutive runs, using TBBDA
recovered from the previous run, was 92%. The results We are thankful to Bu-Ali Sina University, Center of
of all five runs are shown in Table 3.
Excellence and Development of Chemical Methods
Since TBBDA contains bromine atoms which are (CEDCM) for financial support.
1088

R. Ghorbani-Vaghe, S. M. Malaekehpour
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