Zinc benzenesulfonate-promoted ecofriendly and efficient synthesis of 1-amidoalkyl-2-naphthols

Article abstract of DOI:10.1080/00397911.2010.527424

A three-component, one-pot condensation of 2-naphthol, aldehydes, and amides catalyzed by zinc benzenesulfonate gives 1-amidoalkyl-2-naphthols in good yields at 80°C under solvent-free conditions. The catalytic activities of zinc benzenesulfoante and 12 o

Full text of DOI:10.1080/00397911.2010.527424

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Zinc Benzenesulfonate–Promoted Eco-
Friendly and Efficient Synthesis of 1-
Amidoalkyl-2-naphthols
Min Wang a , Zhi Guo Song b & Yan Liang a
a College of Chemistry and Chemical Engineering , Bohai University ,
Jinzhou , China
b Center for Science and Technology Experiment , Bohai University ,
Jinzhou , China
Accepted author version posted online: 04 Aug 2011.Published
online: 17 Oct 2011.
To cite this article: Min Wang , Zhi Guo Song & Yan Liang (2012) Zinc Benzenesulfonate–Promoted
Eco-Friendly and Efficient Synthesis of 1-Amidoalkyl-2-naphthols, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 42:4, 582-588, DOI:
10.1080/00397911.2010.527424
To link to this article: http://dx.doi.org/10.1080/00397911.2010.527424
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Synthetic Communications1, 42: 582–588, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.527424
ZINC BENZENESULFONATE–PROMOTED ECO-
FRIENDLY AND EFFICIENT SYNTHESIS OF
1-AMIDOALKYL-2-NAPHTHOLS
Min Wang,1 Zhi Guo Song,2 and Yan Liang1
1College of Chemistry and Chemical Engineering, Bohai University, Jinzhou,
China
2Center for Science and Technology Experiment, Bohai University, Jinzhou,
China
GRAPHICAL ABSTRACT
Abstract A three-component, one-pot condensation of 2-naphthol, aldehydes, and amides
catalyzed by zinc benzenesulfonate gives 1-amidoalkyl-2-naphthols in good yields at
80 ꢀC under solvent-free conditions. The catalytic activities of zinc benzenesulfoante and
12 other metal benzenesulfonates were compared. After the reaction, zinc benzenesulfoante
can be recycled several times without distinct loss of catalytic activity.
Keywords 1-Amidoalkyl-2-naphthols; metal benzenesulfonates; multicomponent
reaction; solvent-free conditions
INTRODUCTION
Amidoalkyl naphthol derivatives have attracted considerable interest because
of their pharmaceutical and agricultural activities. For example, 1-aminomethyl-2-
naphthols have been reported to show cardiovascular activity.[1] The hypotensive
and bradycardiac effects of these compounds in normotensive rats as well as their
in vitro inotropic and aortic contraction effects in the isolated left atria and aorta
of rat have been evaluated. 1-Naphthaleneacetic acid and 2-naphthoxyacetic acid
have been reported to act as plant-growth regulators.[2,3] Because of the importance
of the title compounds, clean synthetic methods for them have gained considerable
attention.
A recent publication reported 1-amidoalkyl-2-naphthols could be synthesized by
a three-component condensation of 2-naphthol, aldehydes, and amides in the presence
of 10mol% para-toluenesulfonic acid (p-TSA) through the tandem process of
Received August 12, 2010.
Address correspondence to Min Wang, College of Chemistry and Chemical Engineering, Bohai
University, Jinzhou 121000, China. E-mail: minwangszg@yahoo.com.cn
582

SYNTHESIS OF 1-AMIDOALKYL-2-NAPHTHOLS
583
Scheme 1. ZBS-promoted synthesis of 1-amidoalkyl-2-naphthols.
ortho-quinone methide (o-QM).[4] Although the use of p-TSA satisfies the reaction, the
method suffers from several drawbacks in terms of green chemistry such as high tem-
perature (125ꢀC) and unrecovered catalyst. Therefore, some modified procedures
using various homogeneous or heterogeneous catalysts including H2NSO3H,[5] oxalic
acid,[6] Fe(HSO4)3,[7] Sr(OTf)2,[8] I2,[9] K5CoW12O40 ꢁ 3H2O,[10] Yb(OTf)3 in ionic
liquid,[11] montmorillonite K10,[12] TMSCl=NaI,[13] and Al2O3-HClO4
have also
[14]
been reported. Though most of these methods achieved good to excellent yields, they
suffer from at least one of the following disadvantages: long reaction time, toxic and
corrosive solvent, higher reaction temperature (>100 ꢀC), and the use of additional
microwave or ultrasonic irradiation. Hence, there is great interest in developing green
and efficient methods for the synthesis of 1-amidoalkyl-2-naphthols.
Recently, metal sulfonates have attracted attention because of their distinct
advantages such as low toxicity, low cost, and relative insensitivity to air and moist-
ure. In our recent study on their catalytic activity, we found they could act as mild
and efficient Lewis acid catalysts for one-pot multicomponent reactions (MCRs)
such as the Biginelli reaction[15] and Mannich reaction.[16] In a continuation of our
investigations on their application, we found they could catalyze one-pot synthesis
of 1-amidoalkyl-2-naphthols derivatives 4 by three-component condensation of
2-naphthol 1, various aldehydes 2, and different amides 3 in the presence of zinc
benzenesulfonate (ZBS) under thermal solvent-free conditions (Scheme 1).
RESULTS AND DISCUSSION
First, we compared the catalytic activity of 13 metal benzenesulfonates
(2 mol%) for the amidoalkylation using 2-naphthol, benzaldehyde, and benzamide
as a model reaction (Table 1). These reactions were carried out at 80 ꢀC under
solvent-free conditions. After screening several trials, it is interesting to note that
transition-metal benzenesulfonates are able to catalyze the reaction to high extent
with 66–92% yields. Especially for entries 2–6, the yields of the products were almost
the same (89–92%). Among the examined transition metal, rare earth metal, and Al
and Mg benzenesulfonates, ZBS gave great yields and it is inexpensive, so ZBS was
selected as the most promising catalyst (Table 1, entry 2).
Next, we investigated the effect of reaction temperature on the synthesis of
1-amidoalkyl-2-naphthols using the reaction of 2-naphthol, benzaldehyde, and
benzamide in the presence of ZBS as a model. It was found that the reaction carried
out at a lower temperature (60 ꢀC) needs longer reaction time. When it was carried
out at 100 ꢀC, a decreased yield (87%) was obtained in a short reaction period (0.2 h).
Therefore, the optimal reaction temperature is 80 ꢀC.

584
M. WANG, Z. G. SONG, AND Y. LIANG
Table 1. Screening of metal benzenesulfonates for the condensation of 2-naphthol, benzaldehyde, and
benzamide
Entry
M(C6H5SO3)x ꢁ aH2O
Time (h)
Yield (%)
1
2
–
8
0a
92
92
91
90
89
66
87
84
82
80
54
86
62
Zn(C6H5SO3)2 ꢁ 6H2O
Fe(C6H5SO3)2 ꢁ 6H2O
Cu(C6H5SO3)2 ꢁ 6H2O
Y(C6H5SO3)3 ꢁ 2H2O
Co(C6H5SO3)2 ꢁ 6H2O
Ni(C6H5SO3)2 ꢁ 6H2O
La(C6H5SO3)3 ꢁ 2H2O
Sm(C6H5SO3)3 ꢁ 2H2O
Nd(C6H5SO3)3 ꢁ 2H2O
Eu(C6H5SO3)3 ꢁ 2H2O
Ce(C6H5SO3)3 ꢁ 2H2O
Al(C6H5SO3)3 ꢁ 7H2O
Mg(C6H5SO3)2 ꢁ 2H2O
0.25
0.5
0.25
0.25
0.7
1
3
4
5
6
7
8
0.25
0.25
0.25
0.25
1
9
10
11
12
13
14
0.25
6
aYield refers to catalyst-free conditions.
Thus, to explore the reaction scope of ZBS-catalyzed amidoalkylation, reac-
tions of 2-naphthol, aromatic aldehydes, aliphatic aldehydes and different amides
(benzamide, urea and acetamide) in the presence of ZBS were carried out at
80 ꢀC. The results are summarized in Table 2. As can be seen, the nature of
Table 2. The one-pot, three component condensation of 2-naphthol, aldehydes, and amines in the
presence of ZBS
Mp
Entry
R1
R2
Time (h)
Product
Yield (%)
Observed
Reported
1
2
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
NH2
NH2
NH2
CH3
0.25
1
4a
4b
4c
4d
4e
4f
92–84a
91
87
89
86
84
83
87
66
54
60
75
83
87
58
51
74
30
15
24
235–237
260–263
234–236
239–241
266–268
186–189
235–238
211–213
207–209
218–221
244–246
240–242
179–181
197–198
152–155
242–244
254–255
208–209
217–219
177–179
233–235[14]
266–267[17]
233–235[18]
239–241[6]
–
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
2-ClC6H4
3
1
4
1
5
1
6
4-ClC6H4
3
187–188[8]
–
7
2.4–Cl2C6H3
4-CH3C6H4
4-CH3OC6H4
4-(CH3)2NC6H4
CH3CH2
1
4g
4h
4i
8
2
209–211[18]
206–208[17]
220–221[17]
244–245[8]
–
172–174[5]
192–193[18]
150–153[19]
241–243[10]
255–256[8]
206–207[17]
222–223[7]
173–175[20]
9
5
10
11
12
13
14
15
16
17
18
19
20
3
4j
6.5
0.5
1
4k
4l
CH3CH2CH2
C6H5
4m
4n
4o
4p
4q
4r
4s
4t
3-NO2C6H4
2-ClC6H4
C6H5
1
1
6.5
6
3-NO2C6H4
2-ClC6H4
CH3
CH3
3
4-CH3C6H4
CH3CH2
CH3
CH3
11
12
aYields refer to four runs with ZBS.

SYNTHESIS OF 1-AMIDOALKYL-2-NAPHTHOLS
585
substituents on the aromatic ring showed significant effects on the conversation. The
reactions of aldehydes with electron-withdrawing groups afforded better yields of
products than those with electron-donating groups. The scope of different amines
was also examined. When benzamide was used as an amine component, both aro-
matic aldehydes and aliphatic aldehydes worked well, affording moderate to good
yields of corresponding products (Table 2, entries 1–12). The condensation
yields with acetamide were lower than those with benzamide and urea (Table 2,
entries 16–20). In addition to urea, the amidoalkylation of thiourea with 2-napthol
and benzaldehyde was also investigated, and no corresponding products were
isolated.
Further, the reusability of ZBS was investigated. When the reaction was com-
pleted, the reaction mixture was washed with water. The catalyst remaining in the
aqueous phase could be recovered by evaporating the filtrate, and then ZBS was
recovered and reused for next run. No significant decrease in activity was observed
even up to four runs (Table 2, entry 1), which demonstrated that ZBS was water
tolerant and efficient for this condensation.
CONCLUSION
In conclusion, a new protocol for synthesizing 1-amidoalkyl-2-naphthols deri-
vatives has been developed. The present protocol enjoys mild reaction conditions,
short reaction time, and simple workup. Moreover, the catalyst can be recovered
conveniently and reused for at least four reaction cycles without distinct loss of
activity. Currently, studies on the extension of this protocol are ongoing in our
laboratory.
EXPERIMENTAL
Melting points were determined using a RY-1 micromelting-point apparatus.
Infrared (IR) spectra were recorded on a Scimitar 2000 series Fourier transform
1
instrument of Varian. H NMR spectra were recorded on a Bruker AV-500 spec-
trometer in dimethylsulfuric (DMSO-d6) using tetramethylsilane (TMS) as an inter-
nal standard. 13C NMR spectra were performed on Bruker AV-500 spectrometer at
125 MHz in DMSO-d6 using TMS as an internal standard. Elemental analyses were
carried out on a EA 2400II elemental analyzer (Perkin-Elmer) and agreed favorably
with the calculated values.
Synthesis of 1-Amidoalkyl-2-naphthols Derivatives
ZBS (0.2 mmol) was added to a mixture of 2-naphthol (10 mmol), An aldehyde
(10 mmol), and an amide (11 mol). The reaction mixture was magnetically stirred on
a preheated water bath at 80 ꢀC. After completion of the reaction (monitored by
thin-layer chromatography, TLC), the reaction mixture was cooled to rt and washed
with water, and the residue was recrystallized from ethanol. The catalyst remaining
in the aqueous phase could be recovered by evaporating the filtrate. The products
1
were characterized by comparing their mp, IR, H NMR, 13C NMR, and elemental

586
M. WANG, Z. G. SONG, AND Y. LIANG
analysis with those reported for the authentic samples. Spectral data for some new
compounds are as follows.
N-((2-Chlorophenyl)(2-hydroxynaphthalen-1-yl)methyl)benzamide (4e).
White solid. Mp: 266–268 ꢀC. IR (KBr): v 3426, 3067, 1633, 1573, 1538, 1346,
1
1075, 822, 752, 711 cmꢂ1. H NMR (500 MHz, DMSO-d6): d 9.93 (s, 1H, OH),
9.01 (d, 1H, J ¼ 6.2 Hz, NH), 8.08 (d, 1H, J ¼ 8.6 Hz, ArH), 7.89 (d, 2H, J ¼ 7.3 Hz,
ArH), 7.82 (d, 1H, J ¼ 7.7 Hz, ArH), 7.78 (d, 1H, J ¼ 8.8 Hz, ArH), 7.52 (t, 1H,
J ¼ 7.3 Hz, ArH), 7.44–7.40 (m, 5H, ArH), 7.36 (d, 1H, J ¼ 5.0 Hz, CH), 7.30–7.22
(m, 3H, ArH), 7.19 (d, 1H, J ¼ 8.8 Hz, ArH). 13C NMR (125 MHz, DMSO-d6): d
165.4, 153.7, 138.8, 134.2, 132.9, 132.7, 131.1, 130.1, 129.4, 128.6, 128.5, 128.3,
128.1, 127.4, 126.6, 126.3, 122.8, 122.3, 118.6, 116.8, 48.6. Anal. calcd. for
C24H18NO2Cl: C, 74.32; H, 4.68; N, 3.61. Found: C, 74.41; H, 4.60; N, 3.55%.
N-((2,4-Dichlorophenyl)(2-hydroxynaphthalen-1-yl)methyl)benzamide
(4g). White solid. Mp: 235–238 ꢀC. IR (KBr): v 3423, 3069, 1633, 1574, 1536, 1344,
1
1074, 819, 748, 709 cmꢂ1. H NMR (500 MHz, DMSO-d6): d 9.98 (s, 1H, OH), 9.17
(d, 1H, J ¼ 6.3 Hz, NH), 8.05 (d, 1H, J ¼ 8.6 Hz, ArH), 7.89 (d, 2H, J ¼ 7.2 Hz,
ArH), 7.82 (d, 1H, J ¼ 7.6 Hz, ArH), 7.78 (d, 1H, J ¼ 8.8 Hz, ArH), 7.57 (d, 1H,
J ¼ 2.1 Hz, ArH), 7.52–7.42 (m, 5H, ArH), 7.37 (dd, 1H, J ¼ 2.1, 6.3 Hz, CH),
7.30–7.27 (m, 2H, ArH), 7.18 (d, 1H, J ¼ 8.8 Hz, ArH). 13C NMR (125 MHz,
DMSO-d6): d 165.5, 153.8, 138.2, 134.1, 133.6, 132.7, 132.1, 131.4, 131.2,
129.6, 128.6, 128.3, 128.1, 127.5, 126.7, 126.5, 122.6, 122.4, 118.6, 116.1, 48.3. Anal.
calcd. for C24H17NO2Cl2: C, 68.26; H, 4.06; N, 3.32. Found: C, 68.34; H, 4.01; N,
3.34%.
N-(1-(2-Hydroxynaphthalen-1-yl)butyl)benzamide (4l). White solid. Mp:
240–242 ꢀC. IR (KBr): v 3415, 3221, 3204, 1632, 1575, 1528, 1342, 1074, 815, 747,
.
715 cmꢂ1 1H NMR (500 MHz, DMSO-d6): d 10.08 (s, 1H, OH), 8.60 (d, 1H,
J ¼ 6.3 Hz, NH), 8.22 (d, 1H, J ¼ 7.7 Hz, ArH), 7.81 (t, 3H, J ¼ 7.2 Hz, ArH), 7.71
(d, 1H, J ¼ 8.8 Hz, ArH), 7.53–7.44 (m, 4H, ArH), 7.31 (t, 1H, J ¼ 7.3 Hz, ArH),
7.20 (d, 1H, J ¼ 8.8 Hz, ArH), 6.04 (q, 1H, J ¼ 7.0 Hz, CH), 2.19–2.11 (m, 1H,
CH2), 1.92–1.85 (m, 1H, CH2), 1.51–1.41 (m, 1H, CH2), 1.33–1.23 (m, 1H, CH2),
0.93 (t, 3H, J ¼ 7.3 Hz, CH3). 13C NMR (125 MHz, DMSO-d6): d 165.2, 152.8,
134.7, 132.1, 131.0, 128.5, 128.4, 128.3, 128.2, 126.9, 126.2, 122.3, 119.8, 118.6,
118.5, 46.6, 36.0, 19.6, 13.8. Anal. calcd. for C21H21NO2: C, 78.97; H, 6.63; N,
4.39. Found: C, 78.88; H, 6.59; N, 4.42%.
ACKNOWLEDGMENT
This research work was financially supported by the Committee of Science and
Technology of Liaoning Province of China (No. 20091001).
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