Reaction of aldehydes and pyrazolones in the presence of sodium dodecyl sulfate in aqueous media

Article abstract of DOI:10.1081/SCC-200054854

The environmentally friendly condensation 3-methyl-1-phenyl-5-pyrazolone or 3-methyl-1H-5-pyrazolone with aromatic and aliphatic aldehydes was performed in water at refluxing temperature for 1 h using sodium dodecyl sulfate (SDS) as the surfactant catalyst (5 mol%), giving 4,4′-alkylmethylene-bis(3-methyl- 5-pyrazolones) in 78.3%-92.1% yields. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200054854

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Reaction of Aldehydes and
Pyrazolones in the Presence
of Sodium Dodecyl Sulfate in
Aqueous Media
Wei Wang a , Shu‐Xiang Wang a , Xin‐Ying Qin a &
Ji‐Tai Li a
a College of Chemistry and Environmental Science,
Hebei University, Key Laboratory of Analytical
Science and Technology, Baoding, China
Version of record first published: 16 Aug 2006.
To cite this article: Wei Wang , Shu‐Xiang Wang , Xin‐Ying Qin & Ji‐Tai Li (2005):
Reaction of Aldehydes and Pyrazolones in the Presence of Sodium Dodecyl Sulfate
in Aqueous Media, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:9, 1263-1269
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Synthetic Communicationsw, 35: 1263–1269, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200054854
Reaction of Aldehydes and Pyrazolones in
the Presence of Sodium Dodecyl Sulfate in
Aqueous Media
Wei Wang, Shu-Xiang Wang, Xin-Ying Qin, and Ji-Tai Li
College of Chemistry and Environmental Science, Hebei University,
Key Laboratory of Analytical Science and Technology, Baoding, China
Abstract: The environmentally friendly condensation 3-methyl-l-phenyl-5-pyrazolone
or 3-methyl-1H-5-pyrazolone with aromatic and aliphatic aldehydes was performed in
water at refluxing temperature for 1 h using sodium dodecyl sulfate (SDS) as the sur-
factant catalyst (5 mol%), giving 4,40-alkylmethylene-bis(3-methyl-5-pyrazolones) in
78.3%ꢀ92.1% yields.
Keywords: 4,40-Alkylmethylene-bis(3-methyl-5-pyrazolones), aqueous media, pyra-
zolones, sodium dodecyl sulfate
INTRODUCTION
Most chemical reactions of organic substances conducted in the laboratory as
well as in industry need organic solvents as reaction media. In 1980, Breslow
discovered that the Diels–Alder reaction performed in water can be greatly
accelerated.[1] Soon it was discovered that other organic reactions (such as
Claisen rearrangement,[2] aldol condensation,[3] Diels–Alder reaction,[4] and
Michael reaction[5] exhibited rate enhancements in water. To date, many
more organic transformations have been carried out in water.[6]
Received in Japan October 20, 2004
Address correspondence to Shu-Xiang Wang, College of Chemistry and Environ-
mental Science, Hebei University, Key Laboratory of Analytical Science and Techno-
logy, Hezuo Road No. 88, Baoding 071002, China. Fax: þ86-312-5079628; E-mail:
orgsyn@mail.hbu.edu.cn

1264
W. Wang et al.
Other reasons that make unique among solvents are that it is cheap, not
inflammable, and more important, it is not toxic. Choice of solvent is one of
the problems in performing eco-efficient processes.[7]
Although today’s environmental consciousness imposes the use of water
as a solvent on both industrial and academic chemists, organic solvents are
still used instead of water because most organic substances are insoluble in
water. Sodium dodecyl sulfate (SDS) is a surfactant, and the surfactant used
in water can make organic materials soluble, and it as stable in water, so it
can solve the drawback of the reactions in water. SDS has been used in a
number of organic reactions as a good catalyst. SDS used as a surfactant
catalyst is a new field in the organic reactions.[8] However, the use of SDS
as a catalyst in aqueous media for the synthesis of 4,40-alkylmethylene-
bis(3-methyl-5-pyrazolones) has not been reported. In this manuscript, we
report a general and highly efficient route for the synthesis of those
compounds using an inexpensive and commercially available SDS as
catalyst. This is an efficient synthesis in aqueous media, not only preserving
the simplicity but also consistently giving the corresponding products in
good yields (Scheme 1).
RESULTS AND DISCUSSION
The results are summarized in Table 1, which shows that the reaction using
SDS as a catalyst in aqueous media gives the corresponding products in
good yields (78.3–92.1%), although it involves the elimination of a
molecule of water. Similar unusual solvent effects have been previously
found in other reactions.[9]
To examine the generality of this process, several examples illustrating
this method for the synthesis of those compounds were studied. As shown
in Table 1, the effect of electron and the nature of substituents on the
aromatic ring did not show strongly obvious effects in terms of yields under
this reaction condition. Benzaldehyde and other aromatic aldehydes
Scheme 1.

Aldehydes and Pyrazolones
1265
Table 1. Synthesis of 4,40-arylidene-bis(3-methyl-pyrazolones) in water
Mp (8C)
Time
(h)
Yielda
(%)
Entry
R1
R2
Found
Lit.[10]
174
a
b
c
C6H5
2-ClC6H4
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
H
1
1
1
1
2
3
4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
86.8
88.7
91.2
91.5
91.6
91.9
92.1
90.2
88.7
88.4
90.6
88.3
90.8
92.1
90.0
78.3
87.0
83.7
80.7
88.8
91.2
171–172
236–237
153–154
207–209
3-ClC6H4
4-ClC6H4
d
210
4-ClC6H4
4-ClC6H4
4-ClC6H4
e
f
2, 4-Cl2C6H4
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
4-HOC6H4
4-CH3C6H4
3-OCH3-4-OHC6H3
H
228–230
224–225
149–150
230–232
152–153
203–204
200–201
227–229
213–214
230–232
224–226
262–264
271–272
300–302
231
g
h
i
152
231
152
204
199
j
k
l
m
n
o
p
q
r
isobutyraldehyde
C6H5
4-ClC6H4
H
4-HOC6H4
3-NO2C6H4
4-NO2C6H4
H
H
H
aIsolated yield.
containing electron-withdrawing groups (such as a nitro group, halide) or
electron-donating groups (such as a hydroxy group) were employed and
reacted well with 3-methyl-l-phenyl-5-pyrazolone to give 4,40-alkylmethylene-
bis-(3-methyl-l-phenyl-5-pyrazolones) in good to excellent yields. At the
same time, the aliphatic aldehydes also give the corresponding products
in good yields (see entries l and m). When changing 3-methyl-l-phenyl-5-
pyrazolone into 3-methyl-1H-5-pyrazolone, a similar result was given;
the reaction gave the corresponding compounds in good yields (see entries
n–r).
The catalyst plays a crucial role in the reaction. For example, 1d reacted
with 2 without any catalyst at refluxing temperature in water for 1 h to give the
product 3d in modest yield (57.4%). While using SDS (5 mol%) as catalyst,
the reaction give a white product in 91.5% yield at the same condition. By
changing the mount of the catalyst from 2.5 mol% to 5 mol%, 7.5 mol%,
and 10 mol%, the reaction results in 3d at 87.7%, 91.5%, 91.9%, and
92.4%, respectively. Higher amounts of the catalyst did not improve the

1266
W. Wang et al.
yields to a greater extent. And, under the identical condition, the yield of the
reaction was not affected in the presence of 5 mol% SDS after different time
intervals (1h, 2 h, 3 h, and 4 h). Thus, 5 mol% SDS was chosen as a quantitative
catalyst for these reactions and 1 h was chosen as the reaction time. The
catalyst could be reused 6 times for the synthesis of 3d without significant
loss of activity (as show in Table 2). SDS is an emulsifying agent, which
catalyzes this reaction and forms the stable colloidal particles in the
presence of the substrates in water and this colloid formation plays an
important role in acceleration of the reactions. In addition, it must be
pointed out that all of these reactions were carried out in water and those
1
products were characterized by mp, IR, H NMR, and elemental analyses.
In summary, a procedure for the preparation of 4,40-alkylmethylene-bis-
(3-methyl-5-pyrazolones) in aqueous media using SDS as the surfactant
catalyst (5 mol%) has been developed. It is noteworthy that the experimental
procedure is very simple, and strict anhydrous conditions are not required.
Water solution is a clean and environmentally desirable system. No harmful
organic solvents are used. This report has proposed and demonstrated a new
useful and attractive process for the synthesis of these compounds.
EXPERIMENTAL
Liquid aldehydes were purified by distillation prior to use. Melting points are
uncorrected. IR spectra were recorded on a Bio-Rad FTS-40 spectrometer
(KBr). Elemental analyses were measured on a Heraeus (CHNO, Rapid)
1
analyzer. H NMR spectra were measured on a Bruker Avance (400 MHz)
spectrometer using TMS as internal standard.
General Procedure
Pyrazolone (2 mmol), aldehyde (1.0 mmol), and SDS (0.05 mmol) in water
(20 mL) were added to a flask and were stirred at room temperature for
0.5 h. Then the mixture was stirred at refluxing for 1 h. After completion of
the reactions, the mixture was cooled to room temperature, the solid was
filtered off and washed with H2O, and the crude products were obtained.
The crude products were purified by recrystallization from ethanol (95%).
Table 2. Reuse of the catalyst for syntheses of 3d
Times
1
2
3
4
5
6
Yield/%
91.3
90.7
90.2
89.7
88.8
88.2

Aldehydes and Pyrazolones
1267
3b. Anal. calcd. for C27H23ClN4O2:C, 68.71; H, 4.91; N, 11.87. Found: C,
68.55; H, 4.48; 12.05. IR (KBr): nmax: 3450, 3060, 2925, 1620, 1560, 1505,
1
1441, 1367, 1299, 844, 757 cm21. H NMR (DMSO): d: 2.24 (s, 6H, CH3),
5.03 (s, IH, CH), 7.23–7.25 (m, 2H, ArH), 7.40–7.42 (m, 8H, ArH), 7.73–
7.75 (m, 4H, ArH).
3c. Anal. calcd. for C27H23ClN4O2: C, 68.71; H, 4.91; N, 11.87. Found: C,
68.46; H, 5.05; 11.62. IR (KBr): nmax: 3426, 3100, 2987, 1600, 1472, 1429,
1
1366, 1296, 1100, 1074, 870, 745 cm21. H NMR (DMSO): d: 2.33 (s, 6H,
CH3), 4.99 (s, 1H, CH), 7.24–7.31 (m, 5H, ArH), 7.33–7.35 (m, 1H, ArH),
7.43–7.47 (m, 4H, ArH), 7.70–7.72 (m, 4H, ArH).
3f. Anal. calcd. for C27H23N5O4: C, 67.21; H, 4.80; N, 14.51. Found: C,
67.15; H, 4.91; 14.36. IR (KBr): nmax: 3441, 3048, 2951, 1642, 1559, 1439,
1
1352, 1294, 1246, 880, 828, 736 cm21. H NMR (DMSO): d: 2.25 (s, 6H,
CH3), 5.44 (s, 1H, CH), 7.22–7.29 (m, 2H, ArH), 7.42–7.49 (m, 5H, ArH),
7.63–7.73 (m, 7H, ArH).
3l. Anal. calcd. for C21H20N4O2: C, 69.98; H, 5.59; N, 15.55. Found C,
69.73; H, 5.47; 15.38. IR (KBr): nmax: 3440, 3059, 2884, 2781, 1577, 1497,
1
1406, 1363, 1312, 1179, 904, 794, 751, 686 cm21. H NMR (DMSO): d:
2.23 (s, 6H, CH3), 3.24 (s, 2H, CH2), 7.23–7.25 (m, 2H, ArH), 7.42–7.46
(m, 4H, ArH), 7.70–7.72 (m, 4H, ArH).
3m. Anal. calcd. for C24H26N4O2: C, 71.62; H, 6.51; N, 13.92. Found: C,
71.54; H, 6.62; 13.85. IR (KBr): nmax: 3428, 3061, 2959, 2733, 1585, 1499,
1
1420, 1291, 1182, 1122, 1027, 901, 791, 750, 638 cm21. H NMR (DMSO):
d: 0.84 [S, 6H, CH(CH3)2], 2.21 (s, 6H, CH3), 2.50–2.64 [m, 1H,
CH(CH3)2], 2.99–3.01 [d, 1H, CHCH(CH3)2], 7.22–7.25 (m, 2H, ArH),
7.42–7.46 (m, 4H, ArH), 7.70–7.72 (m, 4H, ArH).
3n. Anal. calcd. for C15H16N4O2: C, 63.37; H, 5.67; N, 19.71. Found: C,
63.54; H, 5.42; N, 20.05. IR (KBr): nmax: 3415, 1606, 1530, 1491, 1388, 1143,
1
823, 783, 723 cm21. H NMR (DMSO): d: 2.08 (s, 6H, CH3), 4.82 (m, 1H,
CH), 7.13–7.14 (d, 3H, ArH), 7.19–7.23 (m, 2H, ArH).
3o. Anal. calcd. for C15H15ClN4O2: C, 56.52; H, 4.74; N, 17.58. Found:
C, 56.41; H, 4.42; N, 17.36 IR (KBr): nmax: 3437, 1614, 1488, 1388, 1094,
1
757 cm21. H NMR (DMSO): d: 2.08 (s, 6H, CH3), 4.82 (m, 1H, CH), 7.12
(s, 2H, ArH), 7.27 (m, 2H, ArH).
3p. Anal. calcd. for C15H16N4O3: C, 59.99; H, 5.37; N, 18.66. Found: C,
59.80; H, 5.42; N, 18.36. IR (KBr): nmax: 3266, 1561, 1514, 1466, 1400, 1174,
1
872, 786, 731 cm21. H NMR (DMSO): d: 2.06 (s, 6H, CH3), 4.71 (m, 1H,
CH), 6.58–6.60 (d, 2H, ArH), 6.90–6.92 (d, 2H, ArH).
3q. Anal. calcd. for C15H15N5O4: C, 54.71; H, 4.59; N, 21.27. Found: C,
54.50; H, 4.45; N, 20.98. IR (KBr): nmax: 3419, 2961, 1599, 1447, 1390, 1182,
1
837, 795, 764 cm21. H NMR (DMSO): d: 2.11 (s, 6H, CH3), 4.99 (ms, 1H,
CH), 7.54–7.57 (d, 2H, ArH), 7.96 (s, 1H, ArH), 8.03–8.04 (s, 1H, ArH).
3r. Anal. calcd. for C15H15N5O4: C, 54.71; H, 4.59; N, 21.27. Found: C,
54.52; H, 4.43; N, 21.05. IR (KBr): nmax: 3419, 2961, 1603, 1510, 1442, 1346,

1268
W. Wang et al.
1
1178, 880, 800, 772 cm21. H NMR (DMSO): d: 2.10 (s, 6H, CH3), 4.98
(s, 1H, CH), 7.36–7.39 (d, 2H, ArH), 8.11–8.13 (d, 2H, ArH).
ACKNOWLEDGMENT
We thank the Education Commission of Hebei Povince (201104) and Natural
Science Foundation of Hebei Province (203107), China, for supporting this
project.
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