Silver nanoparticles: An efficient and versatile reagent for the synthesis of 1-amidoalkyl-2-naphthols

Article abstract of DOI:10.1080/15533174.2016.1216126

Silver nanoparticles have been prepared and shown to efficiently catalyze the one-pot, three-component reaction of 2-naphthol, aldehydes, and acetamide at reflux, to afford the corresponding 1-amidoalkyl-2-naphthols at high yield. The present method has s

Full text of DOI:10.1080/15533174.2016.1216126

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Silver nanoparticles: An efficient and versatile reagent for the synthesis of 1-amidoalkyl-2-
naphtols
Alireza Hassanabadi, Fatemeh Hakimi*
Department of Chemistry, Payamenoor University, PO BOX 19395-3697 Tehran, Iran and Nano
Structured Coatings Institute,Yazd payame Noor University, PO Code 89431-74559 Yazd, Iran.
*
Corresponding author. E-mail: fatemeh.hakimi@yahoo.com
Abstract
Silver nanoparticles has been prepared and shown to efficiently catalyse the one-pot, three-
component reaction of 2-naphtol, aldehydes, and acetamide at reflux, to afford the corresponding
1
-amidoalkyl-2-naphtols high yield. The present method has several advantages such as high
yields, easy purification, mild reaction conditions, easy work-up, survival of different functional
groups and short reaction times.
Keywords
Silver nanoparticles, 2-naphtol, aldehydes, acetamide, 1-amidoalkyl-2-naphtols, one-pot reaction
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1
. Introduction
Multicomponent reaction (MCR ) are very important and efficient methods in organic synthesis
S
to access complex structures from three or more reactions. Compounds bearing 1,3-amino-
oxygenated functional groups are usually found in various biologically important natural
[
1]
products and potent drugs, including nucleoside antibiotics and HIV protease inhibitors. 1-
[
2]
Amidoalkyl-2-naphtol derivatives which exhibit important cardiovascular, bradycardiac, and
[
3]
hypertensive activity. Previously some catalysis have been utilized for synthesis of 1-
[
4-24]
amidoalkyl-2-naphtols.
Catalytic activities of nanoparticles differ from the chemical properties of the bulk materials. For
[
8]
instance, showed that the bleaching of the organic dyes by application of potassium
peroxodisulphate in aqueous solution at room temperature is enhanced strongly by the
[
8]
application of silver containing nanoparticles. Furthermore, silver nanoparticles (AgNPs) was
found to catalyze the chemiluminescence from luminol–hydrogen peroxide system with catalytic
[
9]
activity better than Au and Pt colloid. Moreover, used silver nanoparticles supported halloysite
nanotubes (Ag/HNTs), with Ag content of about 11% to catalyze the reduction of 4-nitrophenol
[
25]
with NaBH in alkaline aqueous solutions.
4
In this article we investigated the new method for synthesis of 1-amidoalkyl-2-naphtols
derivatives in the presence of AgNPs at reflux.
2
2
.Experimental
.1. Material and instrumentation
Melting points were determined with an Electrothermal 9100 apparatus. IR spectra were
1
13
recorded on a Shimadzu IR-470 spectrometer. H and C NMR spectra were recorded on Bruker
2
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DRX-400 Avance spectrometer for solutions in d -DMSO using TMS as an internal standard.
6
The morphologies of the products were observed using TEM of Philips CM10 and SEM of a
Holland Philips XL30 microscope with an accelerating voltage of 20 kV. The chemicals for this
work were purchased from Fluka (Buchs, Switzerland) and were used without further
purification.
2
.2. Synthesis of silver nanocrystals
Silver nitrate (1 mol) and dodecanoic acid DDA (0.3 mol) were dissolved into n-butylamine (2
mol)/toluene (300 mL) completely, which resulted in a molar concentration [Ag] above 2 M.
After addition of equimolar reductant, the solution became dark brown and then was refluxed for
1
h. After completion of the reaction, products were precipitated by addition of an
acetone/methanol mixture. The precipitates were collected through a glass funnel filter and then
washed several times with methanol and acetone.
2
.3. General procedure for preparation of compounds 3a-l
A mixture of 2-naphthol (1 mmol,), aldehyde (1 mmol), acetamide (1.2 mmol) and catalyst (0.03
g) Ag NPs was grounded in a mortar for 2 minute and then refluxed in ethyl acetate for 30 min.
The progress of the reaction was monitored by TLC. The product is insoluble in hot ethyle
acetate. After completion of the reaction the mixture was dissolved in C H OH, filtered and
2
5
washed with diethyl ether (5 ml) for isolation of catalyst. The solvent was evaporated under
reduced pressure and the product was obtained.
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2
2
.4. Selected data :
.4.1. N-[(2-hydroxy-3-methoxyphenyl)(2-hydroxynaphthalen-1-yl)methyl]
acetamide (3j):
o
-1
Yellow powder, m.p. 157-159 C, IR (KBr) (ν cm ): 3347, 3321, 1635. Analyses: Calcd. for
max
C H NO : C, 71.20; H, 5.68; N, 4.15%. Found: C, 71.4; H, 5.5; N, 4.3. MS (m/z, %): 337 (6).
20
19
4
1
H NMR (400 MHz, d -DMSO): δ 2.02 (3H, s, CH ), 3.73 (3H, s, OCH ), 5.11(1 H, broad s,
6
3
3
3
3
OH), 6.16 (1H, d, J = 8 Hz, NCH), 7.04-7.74 (9H, m, aromatic), 8.00 (1 H, d, J = 8 Hz,
HH
HH
1
3
NH), 9.53 (1 H, broad s, OH)ppm. C NMR (100.6 MHz, d -DMSO): δ 21.4 (CH ), 37.2 (CH),
6
3
5
1
2
5.2 (OCH ), 112.1, 115.3, 118.7, 119.6, 121.0, 122.0, 123.9, 126.3, 128.3, 129.2, 129.4, 130.1,
3
33.0, 143.0, 151.8, 152.1 and 173.0 ppm.
.4.2. Methyl 4-[acetylamino(2-hydroxynaphtalen-1-yl)methyl]benzoate (3k):
o
-1
Pale brown powder, m.p. 220-222 C, IR (KBr) (νmax cm ): 3343, 3310, 1743, 1641. Analyses:
Calcd. for C H NO : C, 72.19; H, 5.48; N, 4.01%. Found: C, 72.0; H, 5.3; N, 4.2. MS (m/z, %):
2
1
19
4
1
3
49 (3). H NMR (400 MHz, d -DMSO): δ 2.10 (3H, s, CH ), 3.79 (3H, s, OCH ), 6.24 (1H, d,
6 3 3
3
3
JHH = 8 Hz, NCH), 6.73-7.86 (10H, m, aromatic), 8.13 (1 H, d, JHH = 8 Hz, NH), 9.55 (1 H,
1
3
broad s, OH)ppm. C NMR (100.6 MHz, d -DMSO): δ 23.3 (CH ), 48.6 (CH), 51.4 (OCH ),
6
3
3
1
1
2
15.4, 117.5, 118.8, 119.3, 122.1, 122.5, 123.2, 126.3, 128.1, 128.8, 130.4, 133.3, 147.2, 153.4,
67.9 and 171.3 ppm.
.4.3. N-[(2-hydroxynaphthalen-1-yl)(4-methylaminophenyl)methyl]acetate (3l).
o
-1
Brown powder, m.p. 121-123 C, IR (KBr) (ν
cm ): 3350, 3345, 1681. Analyses: Calcd. for
max
C H N O : C, 74.98; H, 6.29; N, 8.74%. Found: C, 75.1; H, 6.4; N, 8.9. MS (m/z, %): 320 (5).
20
20
2
2
1
H NMR (400 MHz, d -DMSO): δ 2.17 (3H, s, CH ), 2.69 (3H, s, NCH ), 3.90 (1H, broad s,
6
3
3
4
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3
3
NH), 6.23 (1H, d, J = 8 Hz, NCH), 6.85-7.64 (10H, m, aromatic), 8.16 (1 H, d, JHH = 8 Hz,
HH
1
3
NH), 9.67 (1 H, broad s, OH)ppm. C NMR (100.6 MHz, d -DMSO): δ 23.5 (CH ), 29.6
6
3
(
NCH ), 48.5 (CH), 114.2, 115.3, 118.8, 121.9, 123.3, 126.8, 128.7, 128.9, 129.6, 133.5, 145.2,
3
1
31.3, 134.0, 153.2, and 172.1 ppm.
3
. Result and Discussions
Herein, we attempted to synthesize organicsoluble silver nanoparticles in the organic phase using
silver nitrate as a precursor by adsorption method as versatile reagent for the synthesis of 1-
amidoalkyl-2-naphtols by the three-component condensation of 2-naphthol 1, aldehyde 2, and
acetamide (Scheme 1).
Initially, the fully organic phase system contains silver nitrate as a silver precursor, n-butylamine
(CH (CH ) NH ) as a medium for dissolving the silver salt, dodecanoic acid (CH (CH ) CO H)
3 2 3 2 3 2 10 2
[
DDA] as a capping molecule, toluene as a medium, and NaBH as a reducing reagent were used
4
for silver NPs synthesis as received without further purification. The dodecanoic acid is held as a
silver salt and the mechanistic role of silver ions that are stabilizing the enolates of the 1,3-
dicarbonyl compound that would be required for the reaction. A scheme for direct synthesis of
silver nanoparticles from silver nitrate in the organic phase is illustrated in scheme 2. Formation
of silver nanoparticles was observed with UV spectroscope, which showed surface plasmon
peaks in the range between 380 and 450 nm in scheme 3.
The product was characterised by SEM in Scheme 4. The sem image shows that particle size is
between 70-100nm. The nanoparticles were typically dispersed in toluene for further
characterization using fieldemission transmission electron microscopy (TEM). TEM samples
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were prepared by placing a drop of the colloidal dispersion in toluene on an amorphous carbon-
coated grid in scheme 5. The tem image shows nanoporous that their size is 5nm. The molecular
structure of the capping molecule on the as synthesized nanoparticles was investigated through
1
H NMR in scheme 6. It shows that there were no protons in polar groups such as amino or
carboxylic acid, but only in hydrocarbon (C–H).
To optimize the reaction conditions, the reaction of 2-naphthol, 4-nitrobenzaldehyde and
acetamide was used as a model reaction.
In order to establish the better catalytic activity of silver NPs, we have compared the reaction
using other catalysts at reflux and for 30 min. The results are listed in Table 1. The problems in
the reported protocols such as prolonged reaction time and poor yields prompted us to develop a
new rapid method affording excellent yield using a solid phase acidic green catalyst for the
synthesis of 1-amidoalkyl-2-naphtols.
To determine the optimum quantity of Ag NPs, the reaction of 2-naphthol, 4-nitrobenzaldehyde
and acetamide was carried out at reflux using different quantities of Ag NPs (Table 2). Ag NPs
of 0.03 g gave an excellent yield in 30 min (Table 2, entry 2).
The above reaction was also examined in various solvents (Table 3). The results indicated that
different solvents affected the efficiency of the reaction. Most of these solvents required a longer
time and gave moderate yields, and the best results were obtained when ethyl acetate was used as
solvent (Table 3, entry 4).
To optimise the temperature in the mentioned reaction, we have carried out a model study with a
2
-naphthol, 4-nitrobenzaldehyde and acetamide using 0.03 g of catalyst at various temperatures
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(Table 4). Table 3 clearly demonstrates that reflux is an effective temperature in terms of
reaction time and yield.
To study the scope of the reaction, a series of aldehydes, 2-naphthol and acetamide catalysed by
Ag NPs as catalyst were examined. The results are shown in Table 5. In all cases, aldehydes
substituted with either electron-donating or electron-withdrawing groups underwent the reaction
smoothly and gave products in good yields.
1
13
The compounds 3a-i were characterised by H, C-NMR and IR spectroscopy and elemental
[
26-31]
analyses.
Compounds 3j-l were new and their structures were deduced by elemental and spectral analysis.
1
The mass spectrum of compound 3j showed the molecular ion peak at 337. The H NMR
spectrum of 3j exhibits two sharp lines at δ = 2.02 and 3.73 ppm for the protons of methyl
groups. The methine proton (δ= 6.16) and NH proton couple each other and a doublet is
observed for NH proton at 8.00 ppm which disappears after addition of some D O to the d -
2
6
DMSO solution of 3j. There are observed multiplets between 7.04 and 7.74 ppm which are
1
3
related to aromatic protons. The C NMR spectrum of compound 3j shows 20 distinct signals in
consistent with the proposed structure. The IR spectrum of compound 3j also supported the
−
1
suggested structure and showed absorption bonds at 3347, 3321 and 1635 cm .
. Conclusions
4
In conclusion, we have developed using Ag NPs as an inexpensive, non- volatile, non- explosive,
easy to handle, non-corrosive and environmentally benign catalyst for the synthesis of
7
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biologically active 1-amidoalkyl-2-naphtols from 2-naphthol, acetamide and various aldehyde
compounds.
Acknowledgements
The research council of payamenoor university is gratefully acknowledged for the financial
support for this work.
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Table 1 Evaluation of the activity of different catalysts for the synthesis of 1-amidoalkyl-2-
naphtols
a
Isolated yield.
a
Entry
Catalyst
-
Time /min)
30
Yield /%
1
2
20
30
Ce(SO4)2
30
10
30
30
30
30
3
4
I2
35
46
K 10 clay
-
5
K CoW O . 3H O
30
57
5
12 40
2
6
7
8
9
FeCl .SiO2
30
30
30
60
80
72
75
3
HClO -SiO2
4
NaHSO . H O
4
2
Al(H PO )
30
30
2
4 3
1
1
0
1
p-TSA
58
65
Sulfamic acid
1
1
2
3
Silica sulfuric acid
Silver NPs
70
98
11
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Table 2 Optimisation amount of Ag NPs for the synthesis of 1-amidoalkyl-2-naphtols
a
Isolated yield.
Time
a
Entry Catalyst
Yield (%)
(min)
1
2
0.04
0.03
30
96
98
30
30
30
3
4
0.02
0.01
80
60
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Table 3 Effect of the solvent on the synthesis of 1-amidoalkyl-2-naphtols by Ag NPs
Time
a
Entry Solvent
Yield /%
/
min
1
2
CHCl3
EtOH
30
30
45
30
Solvent-
free
EtOAc
3
4
30
30
40
98
a
Isolated yield.
13
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Table 4 Optimisation of temperature using Ag NPs as catalyst
a
Temperature Time Yield
Entry
/
°C
/min /%
1
2
3
25
60
30
30
30
20
30
98
Reflux
a
Isolated yield.
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Table 5 Reaction between 2-naphthol, aldehydes and acetamide catalyzed by Ag
nanoparticles (0.03 g) at reflux
O
R
NH
OH
OH
O
O
Ag Nanoparticles
+
+
EtOAc , reflux, 30 min
NH2
R
H C
H
3
1
2
3
m.p.(°C)
R
%Yield
98
*
reported [Ref.]
3
found
a
b
c
263-265[26]
252-256[27]
242-243[28]
2
-NO C H
2
6 4
260-262
254-256
3
-NO C H
97
98
2
6 4
4
-NO C H
243-245
238-240
228-230
2
6 4
237-238[27]
226-228[27]
215-217[28]
206-208[29]
d
3-Cl C H
94
6
4
e
4-ClC H
96
6
4
f
2-OHC H
90
214-216
6
4
g
208-210
3
-CH OC H
92
85
80
3
6 4
212[30]
212[31]
-
h
4
-OH-3-CH O C H
213-214
211-213
3
6
3
i
Me
j
2
-OH-3-CH O C H 90
157-159
220-222
121-123
3
6 3
k
l
4-CO CH C H
6 4
90
-
-
2
3
4-NHCH
C H
3
6 4
85
*Yields refer to the pure isolated prodoucts
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O
R
NH
O
OH
OH
O
Ag Nanoparticles
+
+
EtOAc , reflux, 30 min
NH2
R
H C
H
3
1
2
3
Scheme 1: Synthesis of 1-amidoalkyl-2-naphtols in the presence of silver NPs as catalyst
16
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Scheme 2: Experimental schemes for direct synthesis of silver nanoparticles in fully organic
phase through in situ ligand exchange
17
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Scheme 3: UV–visible spectrum for silver nanoparticles dissolved into toluene
18
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Scheme 4: The SEM images of silver nanoparticles
19
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Scheme 5: The TEM images of silver nanoparticles
20
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1
Scheme 6: The H-NMR spectrum of silver nanoparticles dissolved into deuteratedchloroform
21
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