Eco-friendly and efficient multi-component method for preparation of 1-amidoalkyl-2-naphthols under solvent-free conditions by dodecylphosphonic acid (DPA)

Article abstract of DOI:10.1016/j.crci.2011.11.012

An efficient and direct eco-friendly protocol for the preparation of 1-amidoalkyl-2-naphthols employing a multi-component, one-pot condensation reaction between β-naphthol, aromatic or aliphatic aldehydes and benzamide or acetamide in the presence of dode

Full text of DOI:10.1016/j.crci.2011.11.012

C. R. Chimie 15 (2012) 365–369
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Full paper/Memoire
Eco-friendly and efficient multi-component method for preparation
of 1-amidoalkyl-2-naphthols under solvent-free conditions by
dodecylphosphonic acid (DPA)
*
Maryam Zandi, Ali Reza Sardarian
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
An efficient and direct eco-friendly protocol for the preparation of 1-amidoalkyl-2-
Received 14 June 2011
naphthols employing a multi-component, one-pot condensation reaction between
b-
Accepted after revision 16 November 2011
Available online 27 January 2012
naphthol, aromatic or aliphatic aldehydes and benzamide or acetamide in the presence of
dodecylphosphonic acid under solvent-free conditions has been described.
´
ß 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords:
Multi-component
b-naphthol
Dodecylphosphonic acid
1-amidoalkyl-2-naphthol
Aldehyde
1. Introduction
effects and bradycardia [7,8], by an amide hydrolysis
reaction.
Multi-component reactions (MCRs) play an important
role in combinatorial chemistry because of their ability to
synthesize small drug-like molecules with several degrees
of structural diversity. These reactions allow compounds to
be synthesized in few steps and usually in a one-pot
manner [1]. Being time and energy saving while having
simple procedures, high bond forming efficiency and low
expenditures are among the advantages of these reactions
[2]. Therefore finding and designing new MCRs has been
the subject of extensive research.
The preparation of 1-amidoalkyl-2-naphthols can be
carried out by condensation of aryl aldehydes, -naphthol,
b
and acetonitrile or amides in the presence of Lewis or
BrØnsted acid catalysts such as montmorillonite K10 clay
[9], Ce(SO4)2 [10], iodine [11], K5CoW12O40.3H2O [12], p-
TSA [13], sulfamic acid [14], cation-exchanged resins [15],
FeCl3.SiO2 [16], silica-sulfuric acid [17], BrØnsted acidic
ionic liquid [18], Fe(HSO4)3 [19], Sr(OTf)2 [20], PPA-SiO2
[21], oxalic acid [22], molybdophosphoric acid [23], ZrOCl2
[24], and thiamine hydrochloride [25].
Compounds containing 1,3-amino-oxygenated func-
tional groups are frequently found in biologically active
natural products and potent drugs such as nucleoside
antibiotics and HIV protease inhibitors [3–6]. Further-
more, 1-amidoalkyl-2-naphthols can be converted
to useful and important biological building blocks and
to 1-aminomethyl-2-naphthols, which exhibit depressor
However, most of the synthetic protocols for 1-
amidoalkyl-2-naphthol reported so far suffer from draw-
backs such as unsatisfactory yields, long reaction times,
and the production of environmental pollutants. Therefore,
a great demand still exists for versatile, simple, and
environmentally friendly processes whereby 1-ami-
doalkyl-2-naphthols may be formed under simple and
practical conditions.
Herein, we report a convenient, mild and efficient
procedure for a one-pot three-component synthesis of new
1-amidoalkyl 2-naphthol derivatives from various aryl and
* Corresponding author.
E-mail address: sardarian@susc.ac.ir (A.R. Sardarian).
1631-0748/$ – see front matter ß 2012 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.11.012

366
M. Zandi, A.R. Sardarian / C. R. Chimie 15 (2012) 365–369
R1
NHCOR2
OH
OH
DPA
R1CHO +
1
R2CONH2
+
Solvent free
90 oC
2
3
4a-s
R1 = aryl or alkyl
R2 = CH3, Ph
Scheme 1.
alkyl aldehydes,
presence of DPA [26] as an effective and cost efficient
catalyst under solvent-free conditions (Scheme 1).
b
-naphthol and different amides in the
(1 mmol) as the test substrate and benzamide (1.2 mmol)
in the presence of DPA (0.1 mmol) was performed in
different solvents, such as H2O, EtOH/H2O (1:1), toluene,
acetonitrile, and ethyl acetate (Table 1, entries 2–6) under
reflux conditions. The reaction did not proceed at all in any
of the solvents except in toluene in which the desired
product was obtained in 48% yield. Then the model
reaction was investigated under solvent-free conditions in
2. Results and discussion
Initially, to optimize and find the best conditions, the
reaction of
b-naphthol (1 mmol), 4-nitrobenzaldehyde
Table 1
Investigated conditions for preparation of 1-amidoalkyl-2-naphthol using of dodecylphosphonic acid (DPA) as catalyst.
Entry
Solvent
Catalyst (mol%)
Temp. (8C)
Time (min)
Yield (%)a
1
2
3
4
5
6
7
8
9
10
Solvent-free
H2O
DPA (10 mol%)
DPA (10 mol%)
DPA (10 mol%)
DPA (10 mol%)
DPA (10 mol%)
DPA (10 mol%)
DPA (5 mol%)
DPA (20 mol%)
DPA (10 mol%)
DPA (10 mol%)
90
20
120
120
120
120
120
20
88
–
Reflux
Reflux
Reflux
Reflux
Reflux
90
EtOH: H2O
Toluene
–
48
–
Acetonitrile
Ethyl acetate
Solvent-free
Solvent-free
Solvent-free
Solvent-free
–
45
90
45
85
90
20
50
20
100
20
a
Isolated yields.
Table 2
The reaction of
b-naphthol, amides and aldehydes in solvent-free conditions.
Entry
1
R1
R2
Product
4a
Time (min)
20
Yielda (%)
88
Mp (lit.(8C)
4-NO2C6H4
C6H5
240
(239–241 [22])
2
3
4
3-NO2C6H4
C6H5
C6H5
C6H5
C6H5
4b
4c
4d
20
20
20
90
90
85
241
(240–242 [27])
235
(235–237 [24])
4-CH3OC6H4
196
(197–199 [23])
5
6
4-(CH3)2CHC6H4
2-BrC6H4
C6H5
C6H5
4e
4f
20
20
90
88
210
229
(228–230 [14])
7
C6H5CH2CH2
C6H5CH = CH
9-Phenanthryl
1-Pyrenyl
2-Naphtyl
CH3(CH2)10
CH3CH2
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
CH3
4g
4h
4i
30
30
20
20
20
30
30
60
20
80
85
81
86
90
70
60
N.R
88
158
8
234
9
251
10
11
12
13
14
15
4j
246
4k
4l
218
166
4m
4n
4o
226
9-Anthryl
C6H5
–
230
(228–230 [11])
16
C6H5CH = CH
CH3
4p
20
81
173
(174–175.5 [23])
17
18
19
9-Phenantryl
2-BrC6H4
CH3
CH3
CH3
4q
4r
4s
20
20
30
86
88
72
273
204
110
CH3(CH2)10
a
Isolated yields.

M. Zandi, A.R. Sardarian / C. R. Chimie 15 (2012) 365–369
367
the presence of DPA (10 mol%) at 90 8C and the desired
product was formed in 88% yield (Table 1, entry 1).
Decreasing of the yield was observed when the reaction
was repeated in the presence of 5 mol% of the catalyst
(Table 1, entry 7). Enhancement of the catalyst loading to
20 mol% did not show any effect on the yield or the reaction
time (Table 1, entry 8).
Also the effect of temperature was studied and the
results indicated that the best yield was provided at 90 8C
(Table 1, entries 1, 9 and 10). At lower temperatures than
that, the reaction did not proceed properly and most of the
initial substances remained unreacted.
These optimized reaction conditions were then applied
on the preparations of 1-amidoalkyl-2-naphthols with a
variety of aromatic and aliphatic aldehydes (Table 2).
Aromatic aldehydes bearing electron-donating and with-
drawing substituents led to good yields of the desired 1-
amidoalkyl-2-naphthols (Table 2, entries 1–6). Even
hindered polynuclear aromatic aldehydes such as 2-
naphthaldehyde, phenantherene-9-carbaldehyde and
pyrene-1-carbaldehyde gave good yields under the same
condition (Table 2, entries 9–11). In contrast to the
previously reported methods in literature [11,19,23], in
which aliphatic aldehydes were not transformed to the
corresponding 1-amidoalkyl-2-naphtols, also in our study
they were converted to the desired product in good yields
were aided by microwave or ultrasound (Table 3, entry 2
and 10).
3. Conclusion
In summary, we have therefore established a catalytic,
environmental friendly route for the one-pot preparation of
a range of new 1-amidoalkyl-2-naphthols witharomatic and
aliphatic aldehydes by using DPA, which is commercially
available and easy to produce, that has not been reported
before. In addition, this method offers several significant
advantages such as: high conversions, easy handling, short
reaction times, easy and green work up, cost efficient and
versatility. These advantages, in general, highlight this
protocol as a useful and attractive methodology, among
the methods reported in the literature, for the rapid
synthesis of 1-amidoalkyl-2-naphthols as precursors of
biological active 1-aminoalkyl-2-naphthols.
4. Experimental
The 1H and 13C NMR spectra were recorded on Bruker
Advance DPX FT spectrometer at 250 and 62.9 MHz,
respectively, and with TMS as an internal standard.
Elemental analyses were performed on Thermofinnigan
1112 flash EA. The synthesized 1-amidoalkyl-2-naphthols
were fully characterized with 1H-NMR, 13C-NMR spectros-
copy and CHN analysis.
when mixed with
b-naphthol and benzamide in the
presence of DPA under solvent-free conditions at 90 8C
(Table 2, entries 12 and 13).
Using acetamide as an aliphatic amide, instead of
benzamide, resulted in the corresponding 1-amidoalkyl-2-
4.1. General procedure for the synthesis of 1-amidoalkyl-2-
naphthols with dodecylphosphonic acid (DPA)
naphthols in good yields when it was treated with
b-
naphthol and aromatic or aliphatic aldehydes in the
presence of DPA at 90 8C (Table 2, entries 15–19).
For showing efficiency of DPA compared to the
reported catalysts in literature, including Lewis acids
and BrØnsted acids, a study was designed on the reaction
A mixture of
b-naphthol (1 mmol), aromatic aldehyde
(1 mmol) and amide (1.2 mmol) and DPA (0.1 mmol) in
5 mL round bottomed flask, which was equipped with a
condenser, was heated at 90 8C. After completion of the
reaction (monitored by TLC), the resulted powder was
dissolved in 20 mL of hot ethanol. Then 20 mL of water was
added to the reaction mixture. The resulting precipitate
was filtered. Then the solid product was purified by
recrystallization in aqueous ethanol.
of
b-naphthol, acetamide, and benzaldehyde as a model.
These data, which are shown in Table 3, revealed that DPA
is a better catalyst than most of the conventional catalysts
mentioned, with the exception being the protocols that
Table 3
A comparison among efficiency of dodecylphosphonic acid (DPA) and some reported acids on the reaction of
b–naphthol, benzaldehyde and acetamide.
Entry
Catalyst
Mole %
Time/yield (%)/condition
1
Fe(HSO4)3
5
65 min/83/solvent-free (85 8C) [19]
7 min/90/solvent-free/microwave [19]
11 min/86/solvent-free (120 8C) [16]
2 h/90/solvent-free (125 8C) [12]
1.5 h/89/solvent-free (125 8C) [9]
4.5 h/87/solvent-free (125 8C) [11]
3.5 h/94/ethylacetate (65 8C) [23]
5 min/80/solvent-free (120 8C) [21]
15 h/89/ClCH2CH2Cl (rt) [13]
2
Fe(HSO4)3
5
3
FeCl3.SiO2
0.025 g
1
4
K5CoW12O40.3H2O
K-10 clay
5
0.1 g
5
6
I2
7
Molybdophosphoric Acid
PPA-SiO2
0.12 g
0.03 g
10
8
9
PTSA
10
11
12
13
14
15
16
Sulfamic acid
Sulfamic acid
[TEBSA][HSO4]
ZrOCl2
50
15 min/89/solvent-free/sonication[14]
4 h/72/solvent-free (28–30 8C) [14]
10 min/81/solvent-free (120 8C) [18]
11 h/79/ClCH2CH2Cl (rt) [24]
50
5
10
Thiamine.HCl
Cyanuric chloride (TCT)
DPA
10
4 h/88/EtOH [25]
10
50 min/93/solvent-free (100 8C)
20 min/88/solvent-free (90 8C)
10

368
M. Zandi, A.R. Sardarian / C. R. Chimie 15 (2012) 365–369
4.2. Spectral data for new compounds
N-(1-(2-Hydroxynaphthalen-1-yl)dodecyl)benza-
mide (4l, C29H37NO2): white solid, m.p 167 8C, 1H NMR
(250 MHz, DMSO-d6): = 0.88(t, 3H), 1.23(m, 18H), 1.67(m,
2H), 6.02(t,1H), 7.21(d,1H), 7.36(t, 1H), 7.53(t, 3H), 7.65(d,
1H), 7.83 (d, 2H), 8.23 (d, 1H), 8.64 (d, 1H), 10.18 (s, 1H). 13
NMR (62 MHz, DMSO-d6): = 13.86, 22, 26.22, 28.87, 31.19,
33.76, 46.79, 118.54, 119.78, 122.33, 126.20, 126.84, 128.33,
131.06, 132.07, 134.63, 152.81, 165.29. Anal. Calcd:C, 80.70;
H, 8.64; N, 3.25. Found: C, 80.74; H, 8.58; N, 3.24.
N-((2-Hydroxynaphthalen-1-yl) (4-isopropylphenyl)
methyl)benzamide (4e, C27H25NO2): white solid, m.p
210 8C, 1H NMR (250 MHz, DMSO-d6):
(m, 1H), 7.00 (d, 1H), 7.09 (m, 6H), 7.42 (m, 4H), 7.75
(m, 4H), 8.08 (d, 1H), 9.01 (d, 1H), 10.34 (s, 1H). 13C
d
d
= 1.10 (d, 6H), 2.72
C
d
NMR (62 MHz, DMSO-d6):
d = 23.81, 32.97, 49.11,
118.34, 122.61, 126.06, 126.49, 126.69, 127.02, 127.39,
128.13, 128.30, 128.45, 128.55, 129.20, 131.14, 131.34,
132.25, 134.30, 139.28, 146.64, 153.05, 165.50. Anal.
Calcd: C, 82.00; H, 6.37; N, 3.54. Found: C, 81.89; H,
6.28; N, 3.48.
N-(1-(2-Hydroxynaphthalen-1-yl)propyl)benzamide
(4 m, C20H19NO2): white solid, m.p 226 8C, 1H NMR
(250 MHz, DMSO-d6):
d = 0.90 (t, 3H), 1.89 (m, 2H), 5.85
(t, 1H), 7.09 (d, 1H), 7.29 (dd, 1H), 7.43 (m, 4H), 7.66 (d, 1H),
7.75 (m, 3H), 8.18 (d, 1H), 8.61 (d, 1H), 10.08 (s, 1H). 13C
N-(1-(2-Hydroxynaphthalen-1-yl)-3-phenylpropyl)
benzamide (4 g, C26H23NO2): white solid, m.p 158 8C, 1H
NMR (62 MHz, DMSO-d6):
d = 11.35, 26.91, 48.49, 118.57,
NMR (250 MHz, DMSO-d6):
5.98 (d, 1H), 7.13–7.24 (m, 6H), 7.40–7.47 (m, 4H), 7.66–
7.82 (m, 4H), 8.02 (d,1H), 8.66 (d, 1H), 10.16 (s, 1H). 13C
d
= 2.04 (m, 2H), 2.74 (t, 2H),
119.53, 122.34, 126.22, 126.87, 128.19, 131.06, 132.23,
134.71, 152.85, 165.37. Anal. Calcd: C, 78.66; H, 6.27; N,
4.59. Found: C, 78.65; H, 6.20; N, 4.55.
NMR (62 MHz, DMSO-d6):
d
= 32.46, 35.60, 46.70, 118.59,
(E)- N-(1-(2-Hydroxynaphthalen-1-yl)-3-phenylal-
lyl) acetamide (4p, C21H19NO2): white solid, m.p 173 8C,
119.62, 122.38, 125.66, 126.22, 126.96, 127.33, 128.18,
128.26, 128.35, 128.45, 128.52, 131.13, 132.02, 134.63,
141.68, 152.90, 165.55. Anal. Calcd: C, 81.86; H, 6.08; N,
3.67. Found: C, 81.86; H, 5.98; N, 3.52.
1H NMR (250 MHz, DMSO-d6):
d = 1.89 (s, 3H), 6.48 (d, 1H),
6.52 (m, 2H), 7.16 (m, 7H), 7.43 (m, 1H), 7.70 (m, 1H), 7.76
(m, 1H), 8.10 (d, 1H), 8.35 (d, 1H), 10.02 (s, 1H). 13C NMR
(E)-N-(1-(2-Hydroxynaphthalen-1-yl)-3-phenylallyl
benzamide (4 h, C26H21NO2): white solid, m.p 234 8C, 1H
(62 MHz, DMSO-d6): d = 27.87, 52.53, 123.51, 127.61,
128.30, 131.27, 132.47, 133.60, 135.81, 137.28, 141.84,
158.24, 173.93. Anal. Calcd: C, 79.47; H, 6.03; N, 4.41.
Found: C, 79.38; H, 5.98; N, 4.33.
N-(2-Hydroxynaphthalen-1-yl)(phenanthren-9-yl)
methyl) acetamide (4q, C27H21NO2): white solid, m.p
273 8C, 1H NMR (250 MHz, DMSO-d6):
d = 1.89 (s, 3H), 7.08
NMR (250 MHz, DMSO-d6):
d = 7.08 (1H, d), 7.17 (d, 1H),
7.21 (m, 4H), 7.41 (m, 3H), 7.75 (m, 3H), 8.07 (d, 1H),
9.01 (d, 1H), 10.43 (s, 1H). 13C NMR (62 MHz, DMSO-d6):
d
= 48.15, 123.51, 127.61, 128.30, 131.27, 132.47, 133.60,
135.81, 137.28, 141.84, 158.24, 165.54. Anal. Calcd: C,
82.30; H, 5.58; N, 3.69. Found: C, 82.27; H, 5.55; N, 3.66.
N-((2-Hydroxynaphthalen-1-yl)(phenanthren-9-
(m, 7H), 7.59 (m, 6H), 7.80 (m, 6H), 8.31 (d, 1H), 8.78 (d,
1H), 8.87 (s, 1H), 9.27 (d, 1H), 10.20 (s, 1H). 13C NMR
yl)methyl) benzamide (4i, C32H23NO2): Pink solid, m.p
(62 MHz, DMSO-d6): d = 28.87, 48.18, 117.47, 118.80,
251 8C, 1H NMR (250 MHz, DMSO-d6):
d
= 7.06 (m, 7H),
122.46, 122.62, 123.53, 124, 126.53, 126.61, 126.89,
127.07, 127.44, 128.19, 128.48, 128.63, 129.69, 130.41,
130.71, 131.23, 134.18, 154.83, 173.17. Anal. Calcd: C,
82.84; H, 5.41; N, 3.58. Found: C, 82.78; H, 5.34; N, 3.42.
N-((2-Bromophenyl)(2-hydroxynaphthalen-1-
7.59 (m, 6H), 7.80 (m, 6H), 8.31 (d, 1H), 8.75 (d, 1H), 8.88 (s,
1H), 9.27 (d, 1H), 10.19 (s, 1H). 13C NMR (62 MHz, DMSO-
d6):
d = 48.15, 117.47, 118.80, 122.46, 122.62, 123.53, 124,
126.53, 126.61, 126.89, 127.07, 127.44, 128.19, 128.48,
128.63, 129.69, 130.41, 130.71, 131.23, 134.18, 153.83,
165.37. Anal. Calcd: C, 84.74; H, 5.11; N, 3.09. Found: C,
84.68; H, 5.05; N, 3.04.
N-((2-Hydroxynaphthalen-1-yl)(pyren-1-yl)methyl)
benzamide (4j, C34H23NO2): Yellow solid, m.p 246 8C, 1H
yl)methyl)acetamide (4r, C19H16BrNO2): white solid, m.p.
204 8C, 1HNMR (250 MHz, DMSO-d6):
d = 1.87 (s, 3H), 6.91
(d, 1H), 7.06–7.29 (m, 5H), 7.47 (t, 2H), 7.69 (m, 2H), 7.92 (d,
1H), 8.54 (d, 1H), 9.73 (s, 1H). 13C NMR (62 MHz, DMSO-d6):
d
= 22.28, 49.84, 116.95, 118.57, 122.18, 122.69, 122.78,
NMR (250 MHz, DMSO-d6):
(m, 5H), 7.80–8.49 (m, 14H), 8.85 (d, 1H), 9.37 (d, 1H),
10.33 (s, 1H). 13C NMR (62 MHz, DMSO-d6):
= 48.29,
d
= 7.22 (d, 1H), 7.25–7.46
126.21, 126.82, 128.20, 128.42, 128.50, 129.31, 130.15,
132.49,132.89, 141.26,153.59,168.42. Anal. Calcd:C, 61.64;
H, 4.36; N, 3.78. Found: C, 61.58; H, 4.28; N, 3.74.
d
117.96, 122.51, 122.93, 124.46, 125.20, 125.34, 126.18,
127.10, 127.22, 127.40, 127.76, 128.25, 128.50, 130.07,
130.19, 130.68, 134.15, 134.81, 153.68, 165.41. Anal.
Calcd: C, 85.51; H, 4.85; N, 2.93. Found: C, 85.49; H, 4.81;
N, 2.89.
N-(1-(2-Hydroxynaphthalen-1-yl)dodecyl)aceta-
mide (4 s, C24H35NO2): white solid, m.p. 110 8C, 1HNMR
(250 MHz, DMSO-d6):
d = 0.79 (t, 3H), 1.15 (m, 18H), 1.80
(s, 3H), 1.91 (m, 2H), 5.68 (t, 1H), 7.11(d, 1H), 7.20 (m, 1H),
7.37 (m, 1H), 7.62 (d, 1H), 7.72 (d, 1H), 7.98 (d, 1H), 8.00 (d,
1H), 9.82 (s, 1H). 13C NMR (62 MHz, DMSO-d6):
d = 13.87,
22.02, 22.67, 26.23, 28.62, 28.77, 28.90, 31.22, 33.56, 45.73,
118.49, 119.74, 122.13, 122.47, 125.98, 128.14, 128.24,
128.41, 132.23, 152.92, 168.36. Anal. Calcd: C, 78.00; H,
9.55; N, 3.79. Found: C, 77.94; H, 9.48; N, 3.75.
N-((2-Hydroxynaphthalen-1-yl)(naphthalen-1-
yl)methyl) benzamide (4k, C28H21NO2): Pink solid, m.p
218 8C, 1H NMR (250 MHz, DMSO-d6):
d = 7.30 (d, 1H),
7.41–7.48 (m, 7H), 7.76–7.80 (m, 7H), 7.88 (d, 1H), 8.14 (d,
1H), 9.12 (d, 1H), 10.47 (s, 1H). 13C NMR (62 MHz, DMSO-
d6):
d = 49.44, 118.14, 118.66, 122.70, 124.37, 125.25,
Acknowledgement
125.64, 126.09, 127.15, 127.30, 127.64, 127.80, 128.38,
128.48, 128.63, 129.52, 131.45, 131.89, 132.67, 139.52,
153.28, 165.90. Anal. Calcd: C, 83.35; H, 5.25; N, 3.47.
Found: C, 83.32; H, 5.19; N, 3.44.
We gratefully acknowledge the support of this work by
Shiraz University Research Council.

M. Zandi, A.R. Sardarian / C. R. Chimie 15 (2012) 365–369
369
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