Saccharin sulfonic acid (SASA) as a highly efficient catalyst for the condensation of 2-naphthol with arylaldehydes and amides (thioamides or alkyl carbamates) under green, mild, and solvent-free conditions

Article abstract of DOI:10.1080/10426507.2012.692131

Saccharin sulfonic acid (SaSA) is used as a highly efficient and recyclable catalyst for the one-pot multicomponent condensation of 2-naphthol with arylaldehydes and amides (thioamides or alkyl carbamates) under green, mild (70 °C), and solvent-free conditions. In this reaction, 1-amidoalkyl-2- naphthols, 1-thioamidoalkyl-2-naphthols, 1-carbamatoalkyl-2-naphthols, bis(1-amidoalkyl-2-naphthol)s, and bis(1-carbamatoalkyl-2-naphthol)s are produced in high to excellent yields and in relatively short reaction times. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Full text of DOI:10.1080/10426507.2012.692131

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Saccharin Sulfonic Acid (SASA) as
a Highly Efficient Catalyst for the
Condensation of 2-Naphthol With
Arylaldehydes and Amides (Thioamides
or Alkyl Carbamates) Under Green, Mild,
and Solvent-Free Conditions
Abdolkarim Zare a , Hamideh Kaveh a , Maria Merajoddin a , Ahmad
Reza Moosavi-Zare b , Alireza Hasaninejad c & Mohammad Ali Zolfigol
b
a Department of Chemistry , Payame Noor University , P.O. Box
19395-4697, Tehran , Iran
b Faculty of Chemistry , Bu-Ali Sina University , Hamedan ,
6517838683 , Iran
c Department of Chemistry, Faculty of Sciences , Persian Gulf
University , Bushehr , 75169 , Iran
Accepted author version posted online: 17 May 2012.Published
online: 31 May 2013.
To cite this article: Abdolkarim Zare , Hamideh Kaveh , Maria Merajoddin , Ahmad Reza Moosavi-
Zare , Alireza Hasaninejad & Mohammad Ali Zolfigol (2013) Saccharin Sulfonic Acid (SASA) as a Highly
Efficient Catalyst for the Condensation of 2-Naphthol With Arylaldehydes and Amides (Thioamides or
Alkyl Carbamates) Under Green, Mild, and Solvent-Free Conditions, Phosphorus, Sulfur, and Silicon
and the Related Elements, 188:5, 573-584, DOI: 10.1080/10426507.2012.692131
To link to this article: http://dx.doi.org/10.1080/10426507.2012.692131
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Phosphorus, Sulfur, and Silicon, 188:573–584, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.692131
SACCHARIN SULFONIC ACID (SASA) AS A HIGHLY
EFFICIENT CATALYST FOR THE CONDENSATION OF
2-NAPHTHOL WITH ARYLALDEHYDES AND AMIDES
(THIOAMIDES OR ALKYL CARBAMATES) UNDER GREEN,
MILD, AND SOLVENT-FREE CONDITIONS
Abdolkarim Zare,1 Hamideh Kaveh,1 Maria Merajoddin,1
Ahmad Reza Moosavi-Zare,2 Alireza Hasaninejad,3
and Mohammad Ali Zolfigol2
1Department of Chemistry, Payame Noor University, P.O. Box 19395-4697,
Tehran, Iran
2Faculty of Chemistry, Bu-Ali Sina University, Hamedan 6517838683, Iran
3Department of Chemistry, Faculty of Sciences, Persian Gulf University,
Bushehr 75169, Iran
GRAPHICAL ABSTRACT
O
X
SaSA (5 mol%)
OH
NH
+
+
Ar
H
R
NH2
70 °C, Solvent-free
5-60 min
Ar
OH
R = Alkyl, Aryl, Vinyl, Alkoxy X = O, S
O
X
R
75-97%
SaSA =
N SO3H
S
O
O
Abstract Saccharin sulfonic acid (SaSA) is used as a highly efficient and recyclable catalyst
for the one-pot multicomponent condensation of 2-naphthol with arylaldehydes and amides
(thioamides or alkyl carbamates) under green, mild (70 ◦C), and solvent-free conditions.
In this reaction, 1-amidoalkyl-2-naphthols, 1-thioamidoalkyl-2-naphthols, 1-carbamatoalkyl-
2-naphthols, bis(1-amidoalkyl-2-naphthol)s, and bis(1-carbamatoalkyl-2-naphthol)s are pro-
duced in high to excellent yields and in relatively short reaction times.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Received 18 March 2012; accepted 4 May 2012.
The authors gratefully acknowledge support of this work by the Research Affairs Office of Payame Noor
University, Bu-Ali Sina University (Grant number 32–1716 entitled development of chemical methods, reagents
and molecules), and Persian Gulf University, and also Center of Excellence in Development of Chemical Method
(CEDCM), Hamedan, Iran.
Address correspondence to Abdolkarim Zare, Department of Chemistry, Payame Noor University, P.O. Box
19395-4697, Tehran, Iran. E-mail: abdolkarimzare@yahoo.com
573

574
A. ZARE ET AL.
Keywords Saccharin sulfonic acid (SaSA); amide (thioamide or alkyl carbamate); 1-
amidoalkyl-2-naphthol; 1-thioamidoalkyl-2-naphthol; 1-carbamatoalkyl-2-naphthol; multi-
component reaction
INTRODUCTION
Green chemistry is the design, development, and implementation of chemical prod-
ucts and processes to reduce or eliminate the use and generation of substances hazardous
to human health and the environment.1 It is an innovative, nonregulatory, and economically
driven approach toward sustainability.1 The unequivocal value of green chemistry to the
business and to the environment is illustrated through industrial examples.1 The subject of
green chemistry is currently guided by a series of principles, and solvent-free is one of the
green chemical methods which have many advantages.2 For some reasons of economy and
pollution, solvent-free methods are of great interest in order to modernize classical proce-
dures making them to achieve in shorter reaction times, and with higher yields, improved
selectivity as well as easier purification of the products.2–8
Currently, the use of SO3H-containing catalysts has received considerable interest
by chemists due to their unique advantages such as efficiency, high reactivity, opera-
tional simplicity, environmental compatibility, nontoxicity, low cost, ease of isolation,
green nature, easy availability of their starting materials, and ability to promote a wide
range of reactions.7–18 Saccharin sulfonic acid (SaSA) is certainly one of the interesting
examples of SO3H-containing catalysts, which has been recently reported to promote or-
ganic transformations.15–18 This catalyst has successfully promoted the following reactions:
(i) preparation as well as deprotection of 1,1-diacetates,15 (ii) chemoselective trimethylsi-
lylation of alcohols,16 (iii) acetylation of alcohols, phenols, and amines,17 and (iv) N-Boc
protection of amines and formation of t-butyl ethers from alcohols.18
Multicomponent reactions (MCRs) have drawn great interest enjoying an outstanding
status in modern organic synthesis and medicinal chemistry, because they are one-pot
processes bringing together three or more components and show high atom economy
and high selectivity.19–24 Moreover, MCRs offer the advantage of simplicity and synthetic
efficiency over conventional chemical reactions.19–24
1-amidoalkyl-2-naphthol, 1-thioamidoalkyl-2-naphthol, and 1-carbamatoalkyl-2-
naphthol derivatives are of importance as they can be easily hydrolyzed to the biologically
interesting compounds, 1-aminoalkyl-2-naphthols. 1-aminoalkyl-2-naphthols have been
frequently applied as hypotensive and bradycardiac agents.25,26 For example, one of the
most important biologically active compounds, containing a 1-aminoalkyl-2-naphthol
moiety in its structure, is compound (a) which has been shown to have hypotensive and
bradycardic activities (Figure 1).26 1-amidoalkyl-2-naphthols can also be converted to
1,3-oxazine derivatives (b) (Figure 1).27 1,3-oxazines have potentially different biological
activities including antibiotic,28 antitumor,29 analgesic,30 anticonvulsant,31 antipsychotic,32
antimalarial,33 antianginal,34 antihypertensive,35 and antirheumatic36 properties.
The one-pot multicomponent condensation of 2-naphthol with aldehydes and amide
derivatives (or acetonitrile) has been used as a practical synthetic route toward 1-amidoalkyl-
2-naphthols.37–47 Some catalysts have been applied for this transformation, e.g., Ce(SO4)2,37
montmorillonite K-10,38 HClO4/SiO2,39 H3[P(Mo3O10)4],40 sulfonic acid functionalized
imidazolium salts,41 sulfamic acid/ultrasound,42 Sr(OTf)2,43 copper p-toluenesulfonate,44

SACCHARIN SULFONIC ACID AS A CATALYST
575
R
N
H
N
R
H
OH
O
(a)
(b)
Figure 1 The general structures of 1-aminoalkyl-2-naphthols (a) and 1,3-oxazines (b).
1-butyl-3-methylimidazolium bromide/microwave,45 polyethylene glycol-based dicationic
acidic ionic liquid,46 trityl chloride,47 Yb(OTf)3,48 and 2,4,6-trichloro-1,3,5-triazine.49 1-
thioamidoalkyl-2-naphthols have been prepared by the reaction between 2-naphthol, alde-
hydes, and thioamides using silica sulfuric acid.50 This transformation has been scarcely
studied in the literature. The useful protocol which has been utilized for the synthesis
of 1-carbamatoalkyl-2-naphthols involves the reaction of 2-napthol with aldehydes and
alkyl carbamates in the presence of some catalysts, such as 4-(1-imidazolium) butane
sulfonate,51 silica-supported NaHSO4,52 silica-supported Preyssler nanoparticles,53 and 1-
butyl-3-methylimidazolium bromide/p-toluene sulfonic acid.54 The synthesis of this class
of compounds has been also rarely reported.
Although some catalysts and methods for the synthesis of 1-amidoalkyl (thioami-
doalkyl or carbamatoalkyl)-2-naphthol derivatives are known, newer catalysts and methods
continue to attract attention for their difference with the others, generality and effectiveness.
Furthermore, most of the reported methods for the synthesis of the title compounds suffer
from one or more of the following drawbacks: the use of expensive40,46,48,53 and toxic49
catalysts, poor compliance with the green chemistry protocols,37,40,43,47 the use of large
amount of catalyst,37,42,45 low product yield,37,50–52,54 prolonged reaction time,37,40,43,47,50,51
application of an additional energy (ultrasound or microwave),42,45 and especially harsh
reaction conditions38,39,41,45,52,53 as well as no generality (in most of the reported proce-
dures, the synthesis of one type of the title compounds has been achieved).37–47,52,53 In this
work, we have found that SaSA is a catalyst which can solve the above mentioned disad-
vantages accompanied with the methods reported for the preparation of title compounds;
it is an inexpensive, nontoxic, recyclable, and green catalyst; 5 mol% of SaSA is sufficient
to promote the reaction efficiently and affords the desired p◦roducts in high to excellent
yields and in relatively short reaction times under mild (70 C), green, and solvent-free
conditions; and finally it can catalyze the synthesis of the three types of the compounds,
including 1-amidoalkyl-2-naphthols, 1-thioamidoalkyl-2-naphthols, and 1-carbamatoalkyl-
2-naphthols. Moreover, SaSA can catalyze the synthesis of bis(1-amidoalkyl-2-naphthol)s
and bis(1-carbamatoalkyl-2-naphthol)s.
In this paper, we report our results on the one-pot multicomponent condensation of
2-naphthol with arylaldehydes and amides (thioamides or alkyl carbamates) in the presence
◦
of catalytic amount of SaSA under green and solvent-free conditions at 70 C to give 1-
amidoalkyl (thioamidoalkyl or carbamatoalkyl)-2-naphthols (Scheme 1). Our protocol has
solved the above mentioned drawbacks, and improved efficiently the synthesis of the title
compounds.

576
A. ZARE ET AL.
O
R
NH2
OH
NH
SaSA (5 mol%), 70 °C, Solvent-free
R = Alkyl, Aryl, Vinyl
Ar
O
R
1a-m
S
O
H3C
NH2
OH
+
Ar
H
SaSA (5 mol%), 70 °C, Solvent-free
Ar
NH
OH
S
CH3
2a-d
O
H3CO
NH2
OH
O
SaSA (5 mol%), 70 °C, Solvent-free
Ar
NH
OCH3
SaSA =
N SO3H
O
S
O
O
3a-e
Scheme 1 The condensation of 2-naphthol with arylaldehydes and amides (thioamides or alkyl carbamates).
RESULTS AND DISCUSSION
At first, we selected the one-pot three-component condensation of 2-naphthol with
benzaldehyde and acetamide as model reaction to provide 1-amidoalkyl-2-naphthol 1a.
This reaction was studied in the absence of catalyst under solvent-free conditions at 70 ◦C
in which the product was obtained in 19% yield after 240 min. Afterward, the solvent-
free reaction was examined in the presence of different amounts of SaSA at range of
60 ◦C–80 ◦C; the respective results are summarized in Table 1. As it is clear from Table 1,
the best results for the preparation of 1-amidoalkyl-2-naphthol 1a were obtained when
5 mol% of SaSA was used at 70 ◦C (Table 1, entry 3). The use of excess of amount of the
catalyst or increment of the temperature did not lead to increasing the yield or decreasing
the reaction time.
Table 1 Optimization amount of the catalyst and the reaction temperature on the condensation of 2-naphthol
with benzaldehydes and acetamide
SaSA amount
(mol%)
Temperature
(◦C)
Time
(min)
Yield
a (%)
Entry
1
2
3
4
5
6
–
2.5
5
7.5
5
70
70
70
70
60
80
240
60
35
35
100
35
19
45
93
93
56
93
5
aIsolated yield.

SACCHARIN SULFONIC ACID AS A CATALYST
577
After optimization of the reaction conditions, 2-naphthol was reacted with different
aromatic aldehydes and various amides to show the efficiency and the generality of the
method; the corresponding results are displayed in the Table 2. As it is shown in Table 2,
all arylaldehydes including benzaldehyde and arylaldehydes carrying electron-releasing
substituents, electron-withdrawing substituents, or halogens, and also all amides consisting
of acetamide, benzamide, nicotinamide, and acrylamide afforded the desired 1-amidoalkyl-
2-naphthol derivatives in high to excellent yields (84%–97%) within relatively short reaction
times (20–60 min) (Table 2, compounds 1a–m). Interestingly, the method was highly
efficient when thioamides or alkyl carbamates were used instead of amides. In these cases,
1-thioamidoalkyl-2-naphthol and 1-carbamatoalkyl-2-naphthol derivatives were obtained
in high to excellent yields (75%–97%) and in relatively short reaction times (5–55 min)
(Table 2, compounds 2a–d and 3a–e).
Furthermore, when 2.2 equivalents of 2-naphthol was reacted with 1 equivalent of
terephthaldehyde (a bis-aldehyde) and 2.4 equivalents of amides (or methyl carbamate)
using 10% mol of SaSA at 70 ◦C in the absence of solvent, bis(1-amidoalkyl-2-naphthol)
derivatives 4a and 4b as well as bis(1-carbamatoalkyl-2-naphthol) 4c were obtained in high
yields (84%–88%) and in relatively short reaction times (35–60 min) (Table 3).
The above observations confirmed that our method and catalyst are highly efficient
and general.
To compare the efficiency of our method with the reported methods for the synthesis
of 1-amidoalkyl-2-naphthols, we have tabulated the results of these methods to perform
the condensation reaction between 2-naphthol, benzaldehyde and acetamide in Table 4.
As it is shown in Table 4, our method is superior to the previously reported methods in
term of reaction temperature, reaction time, and/or yield. Moreover, in spite of the reported
methods, in our protocol, the synthesis of the three types of the compounds, including 1-
amidoalkyl-2-naphthols, 1-thioamidoalkyl-2-naphthols, and 1-carbamatoalkyl-2-naphthols
have been achieved.
In another study, recyclability of the catalyst was investigated. For this purpose,
the reaction of 2-naphthol with benzaldehyde and methyl carbamate was performed
in the presence of SaSA several times, and the reaction mixtures were combined. Af-
terward, the product (3a) was extracted by hot ethyl acetate (the product is soluble in hot
ethyl acetate, but SaSA is not soluble in this solvent), and the remained catalyst was used
for the next run of the reaction. Catalytic activity of SaSA was restored within the limits of
the experimental errors for four successive recycle runs.
In a plausible mechanism, we suggest that at first, 2-naphthol is condensed with alde-
hyde in the presence of SaSA to provide ortho-quinone methide (o-QM). Afterward, o-QM
reacts with amide (thioamide or alkyl carbamate) to produce 1-amidoalkyl (thioamidoalkyl
or carbamatoalkyl)-2-naphthol. The SO3H group of SaSA, via hydrogen bonding with the
carbonyls of aldehyde and o-QM, activates them to accept nucleophilic attack by 2-naphthol
or amide (thioamide or alkyl carbamate). This mechanism, which has been reported in the
literature,41,51,52 is illustrated in Scheme 3.
In conclusion, we have introduced a new method for the one-pot three-component
condensation of 2-naphthol with aromatic aldehydes and amides (thioacetamides or alkyl
carbamates) using SaSA as an interesting SO3H-containing catalyst in solvent-free condi-
tions. The promising points for this method are efficiency, generality, high yields, relatively
short reaction times, cleaner reaction profile, simplicity, ease of preparation and recycla-
bility of the catalyst, easy work-up and purification of the products, and compliance with
the green chemistry protocols which makes it an attractive procedure for the preparation of

578

579

580
A. ZARE ET AL.
Table 4 Comparison of results of the reaction of 2-naphthol with benzaldehyde and acetamide using our method
with those obtained by reported methods
Temperature
(◦C)
Time
(min)
Yield
(%)
Catalyst
Ref.
a
Saccharin sulfonic acid
Ce(SO4)2
70
85
125
110
65
35
2160
90
40
210
5
93
72
89
89
95
94
–
b
37
38
39
40
41
Montmorillonite K10 clay
HClO4/SiO2
H3[P(Mo3O10)4]
Sulfonic acid functionalized
imidazolium salt
Sulfamic acid
120
28–30 (Ultrasound)
Reflux in CHCl3
80
130 (Microwave)
r.t.
80
80
15
600
90
89
90
94
94
92
90
85
83
92
93
90
42
43
44
45
47
48
51
55
56
56
57
Sr(OTf)2
Copper p-toluenesulfonate
[Bmim]Br
Trityl chlorideb
Yb(OTf)3
4-(1-Imidazolium)butanesulfonate
Fe(HSO4)3
Silphox
25
105
360
120
65
30
20
85
120
120
125
Silphos
K5CoW12O40·3H2O
120
aOur catalyst.
bIn this work, acetonitrile instead of acetamide has been used.
OH
NH
R'
CHO
O
R'
O
SaSA (10 mol%)
+
+
R'
NH2
HN
HO
70 °C, Solvent-free
O
OH
CHO
R' = CH3, Ph, OMe
4a-c
Scheme 2 The reaction of 2-naphthol with terephthaldehyde and amides (or methyl carbamate).
RCXNH2
OH
NH
ArCHO
SaSA
O
SaSA
X = O, S
OH
Ar
Ar
H
R
X
o-QM
Scheme 3 The proposed mechanism for the synthesis of 1-amidoalkyl (thioamidoalkyl or carbamatoalkyl)-2-
naphthols.

SACCHARIN SULFONIC ACID AS A CATALYST
581
1-amidoalkyl-2-naphthols, 1-thioamidoalkyl-2-naphthols, 1-carbamatoalkyl-2-naphthols,
bis(1-amidoalkyl-2-naphthol)s, and bis(1-carbamatoalkyl-2-naphthol)s as biologically im-
portant compounds.
EXPERIMENTAL
All chemicals were purchased from Merck or Fluka Chemical Companies (New
Delhi, India). The 1H NMR (250, 300, or 400 MHz) and 13C NMR (62.5, 75, or 100 MHz)
were run on a Bruker Avance DPX FT-NMR spectrometer. Mass spectra were obtained
with apparatus Shimadzu GC-MS-QP 1100 EX model. Melting points were recorded on a
Bu¨chi B-545 apparatus in open capillary tubes.
Preparation of SaSA
A flask (500 mL) charged with saccharin (17.1 g, 0.1 mol) was equipped with a
constant pressure dropping funnel containing chlorosulfonic acid (11.65 g, 0.1 mol) and a
gas outlet tube which was dipped into water to dissolve the generated HCl gas during the
reaction. The flask was put into an ice bath and chlorosulfonic acid was added dropwise
over a period of 10 min and the resulting mixture was stirred slowly for another 10 min. The
temperature of the mixture was brought up to the room temperature and was stirred for an
additional 30 min. The mixture was triturated with n-hexane (10 mL) and then filtered. The
solid residue was washed with n-hexane (10 mL) and dried under vacuum to give SaSA as
a white powder; mp 109 ◦C–111 ◦C (literature 110 ◦C–112 ◦C).15–18
General Procedure for the Condensation of 2-Naphthol with
Arylaldehydes and Amides (Thioamides and Alkyl Carbamates)
A well ground mixture of 2-naphthol (0.144 g, 1 mmol), arylaldehyde (1 mmol),
amide (thioamide or alkyl carbamate) (1.2 mmol) and SaSA (0.013 g, 0.05 mmol) was
stirred mechanically at 70 ◦C. The progress of the reaction was monitored by TLC. After
completion of the reaction, the reaction mixture was allowed to cool to room temperature,
and the resulting solid was recrystallized from hot ethanol (EtOH) (95%) to give pure 1-
amidoalkyl (thioamidoalkyl or carbamatoalkyl)-2-naphthol (compounds 1a–m, 2a–d, and
3a–e).
Note: In the case of liquid aldehydes, at first, a mixture of 2-naphthol, amide
(thioamide or alkyl carbamate) and SaSA were ground vigorously, and subsequently, alde-
hyde was added.
General Procedure for the Condensation Between 2-Naphthol,
Terephthaldehyde and Amides (or Alkyl Carbamates)
A well ground mixture of compounds consisting of 2-naphthol (0.317 g, 2.2 mmol),
terephthalaldehyde (0.144 g, 1 mmol), amide (or alkyl carbamate) (2.4 mmol), and SaSA
◦
(0.026 g, 0.1 mmol) was stirred magnetically at 70 C. After completion of the reaction,
as monitored by TLC, the reaction mixture was cooled to room temperature, and triturated
with hot EtOH (95%) (the impurities are soluble in hot EtOH; however, the product is
not soluble in this solvent) to give pure bis[1-amidoalkyl (or carbamatoalkyl)-2-naphthol]

582
A. ZARE ET AL.
(compounds 4a–c). The online Supplemental Materials contains sample 1H and 13C NMR
spectra for novel compounds 1l, 2d, 3e, and 4c (Figures S1–S8).
N-[(2-Hydroxynaphthalen-1-yl)(4-hydroxyphenyl)methyl]acrylamide
1
(1l). IR (KBr): 3398, 3231, 1642, 1604, 1482 cm−1; H NMR (400 MHz, DMSO-d6): δ
5.61 (d, J = 10.0 Hz, 1H), 6.14 (d, J = 16.8 Hz, 1H), 6.59 (dd, J = 10.0, 16.8 Hz, 1H),
6.68 (d, J = 8.4 Hz, 2H), 7.0 (d, J = 8.0 Hz, 2H), 7.14 (d, J = 8.4 Hz, 1H), 7.24–7.29
(m, 2H), 7.39 (s, 1H), 7.76–7.82 (m, 2H), 7.91 (s, 1H), 8.70 (d, J = 8.0 Hz, 1H), 9.28 (s,
1H), 9.99 (s, 1H); 13C NMR (100 MHz, DMSO-d6): δ 48.2, 115.3, 119.0, 119.2, 122.8,
123.8, 125.9, 126.7, 127.9, 128.9, 129.0, 129.5, 132.3, 132.6, 132.8, 153.6, 156.3, 164.7;
MS (m/z): 319 (M+). Anal. calcd. for C20H17NO3: C, 75.22; H, 5.37; N, 4.39; found: C,
75.45; H, 5.48; N, 4.31.
N-[(2-Hydroxynaphthalen-1-yl)(p-tolyl)methyl]thioacetamide (2b). IR
1
(KBr): 3354, 3163, 3024, 1596, 1121 cm−1; H NMR (300 MHz, DMSO-d6): δ 2.21 (s,
3H), 2.53 (s, 3H), 7.02, (d, J = 3.9 Hz, 4H), 7.18–7.28 (m, 3H), 7.37 (d, J = 7.2 Hz,
1H), 7.78 (t, J = 7.5 Hz, 3H), 7.96 (d, J = 8.4 Hz, 1H), 10.33 (s, 1H); 13C NMR
(75 MHz, DMSO-d6): δ 21.0, 33.5, 55.8, 117.6, 119.0, 119.4, 126.4, 127.0, 127.9, 128.7,
129.7, 130.1, 133.1, 136.2, 137.8, 154.0, 199.9; MS (m/z): 321 (M+). Anal. calcd. for
C20H19NOS: C, 74.73; H, 5.96; N, 4.36; found: C, 74.92; H, 5.88; N, 4.46.
N-[(2-Hydroxynaphthalen-1-yl)(3-nitrophenyl)methyl]thioacetamide
1
(2c). IR (KBr): 3365, 3172, 3021, 1587, 1520, 1339, 1113 cm−1; H NMR (400 MHz,
DMSO-d6): δ 2.63 (s, 3H), 7.28 (d, J = 12.0 Hz, 1H), 7.31 (t, J = 7.6 Hz, 1H), 7.49 (t,
J = 7.6 Hz, 1H), 7.58 (d, J = 5.2 Hz, 2H), 7.81–7.90 (m, 3H), 7.98 (s, 1H), 8.03 (d,
J = 8.4 Hz, 1H), 8.08–8.11 (m, 1H), 10.3 (s, 1H), 10.56 (d, J = 8.0 Hz, 1H); 13C NMR
(100 MHz, DMSO-d6): δ 33.3, 35.3, 116.5, 118.9, 121.1, 122.0, 122.9, 123.2, 127.5, 128.7,
129.2, 130.1, 130.9, 133.0, 133.5, 143.5, 148.2, 145.3. 201.3; MS (m/z): 352 (M+). Anal.
calcd. for C19H16N2O3S: C, 64.76; H, 4.58; N, 7.95; found: C, 64.51; H, 4.46; N, 8.04.
N-[(2-Hydroxynaphthalen-1-yl)(4-bromophenyl)methyl]thioacetamide
1
(2d). IR (KBr): 3351, 3147, 3029, 1595, 1107 cm−1; H NMR (400 MHz, DMSO-d6):
δ 2.59 (s, 3H), 7.09 (d, J = 8.4 Hz, 2H), 7.25 (d, J = 8.0 Hz, 1H), 7.31 (t, J = 7.2 Hz,
1H), 7.43–7.49 (m, 3H), 7.78–7.85 (m, 3H), 7.99 (d, J = 8.8 Hz, 1H), 10.20 (s, 1H), 10.40
(d, J = 8.0 Hz, 1H); 13C NMR (100 MHz, DMSO-d6): δ 33.4, 55.3, 117.0, 118.9, 120.0,
123.1, 123.2, 127.2, 128.7, 129.1, 130.4, 131.3, 131.4, 133.0, 140.4, 154.2, 200.6; MS
(m/z): 386 (M+). Anal. calcd. for C19H16BrNOS: C, 59.07; H, 4.17; N, 3.63; found: C,
59.34; H, 4.05; N, 3.54.
Methyl (4-Bromophenyl)(2-hydroxynaphthalen-1-yl)methylcarbamate
(3e). IR (KBr): 3405, 3227, 1675, 1582, 1441 cm−1; 1H NMR (400 MHz, DMSO-d6): δ
3.59 (s, 3H), 6.85 (d, J = 8.8 Hz, 1H), 7.19 (d, J = 8.0 Hz, 2H), 7.23–7.31 (m, 2H), 7.41
(t, J = 8.0 Hz, 1H), 7.47 (d, J = 8.4 Hz, 2H), 7.72 (d, J = 5.2 Hz, 1H), 7.78–7.83 (m, 2H),
7.91 (d, J = 7.2 Hz, 1H), 10.18 (s, 1H); 13C NMR (100 MHz, DMSO-d6): δ 50.4, 52.1,
118.8, 118.9, 119.9, 123.0, 127.1, 128.7, 128.8, 129.0, 130.0, 131.4, 132.4, 142.4, 153.4,
157.1; MS (m/z): 386 (M+). Anal. calcd. for C19H16BrNO3: C, 59.08; H, 4.18; N, 3.63;
found: C, 58.87; H, 4.27; N, 3.52.
N,N’ -[1,4-Phenylenebis((2-hydroxynaphthalen-1-yl)methylene)]diben-
1
zamide (4b). IR (KBr): 3404, 3180, 1635, 1601, 1477 cm−1; H NMR (400 MHz,
DMSO-d6): δ 7.26–7.39 (m, 8H), 7.44–7.59 (m, 10H), 7.78–7.88 (m, 6H), 7.94 (d,
J = 7.2 Hz, 2H), 8.13 (d, J = 8.4 Hz, 2H), 9.07 (d, J = 8.4 Hz, 2H), 10.39 (s, 2H); 13C
NMR (100 MHz, DMSO-d6): δ 49.7, 118.7, 119.2, 123.2, 127.0, 127.3, 127.8, 128.6,
128.9, 129.8, 130.3, 131.7, 132.7, 134.6, 135.3, 140.9, 153.6, 168.5; MS (m/z): 523 (M+

SACCHARIN SULFONIC ACID AS A CATALYST
583
– PhCO), 418 (M+ – 2PhCO), 380 (M+ – C17H12O2). Anal. calcd. for C42H32N2O4: C,
80.24; H, 5.13; N, 4.46; found: C, 80.51; H, 5.01; N, 4.60.
Dimethyl 1,4-Phenylenebis[(2-hydroxynaphthalen-1-yl)methylene]dicar-
bamate (4c). IR (KBr): 3421, 3244, 1695, 1603, 1477 cm−1; 1H NMR (400 MHz, DMSO-
d6): δ 3.55 (s, 6H), 6.78 (d, J = 8.4 Hz, 2H), 7.13 (s, 4H), 7.17–7.20 (dd, J = 4.0, 9.2 Hz,
2H), 7.27 (t, J = 7.6 Hz, 2H), 7.37 (d, J = 9.2 Hz, 2H), 7.61 (s, 2H), 7.75 (d, J = 8.8 Hz,
2H), 7.79 (d, J = 8.0 Hz, 2H), 7.91 (s, 2H), 10.08 (s, 2H); 13C NMR (100 MHz, DMSO-d6):
δ 50.7, 52.1, 118.9, 119.2, 122.9, 126.3, 126.7, 127.0, 128.8, 129.0, 129.7, 132.5, 140.9,
153.3, 156.9; MS (m/z): 536 (M+). Anal. calcd. for C32H28N2O6: C, 71.63; H, 5.26; N,
5.22; found: C, 71.39; H, 5.38; N, 5.07.
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