N,N′,N,N′-tetrabromo-benzene-1,3-disulfonylamide as a novel reagent for oxidative aromatization of 1,3,5-trisubstituted pyrazolines under heterogeneous and solvent-free conditions

Article abstract of DOI:10.1080/10426500490466797

1,3,5-Trisubstituted pyrazolines were converted to the corresponding pyrazoles in good yields under heterogeneous and solvent-free conditions by N,N′,N,N′-tetrabromo-benzene-1,3-disulfonylamide [TBBDA] at ambient temperature.

Full text of DOI:10.1080/10426500490466797

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Phosphorus, Sulfur, and Silicon and the Related
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N,N′,N,N′-TETRABROMO-BENZENE-1,3-
DISULFONYLAMIDE AS A NOVEL REAGENT FOR
OXIDATIVE AROMATIZATION OF 1,3,5-TRISUBSTITUTED
PYRAZOLINES UNDER HETEROGENEOUS AND SOLVENT-
FREE CONDITIONS
Ramin Ghorbani-Vaghei a , Davood Azarifar a , Ardeshir Khazaei a & Behrooz Maleki a
a Department of Chemistry, Faculty of Science, Bu-Ali Sina University , Hamadan, Iran
Published online: 16 Aug 2010.
To cite this article: Ramin Ghorbani-Vaghei , Davood Azarifar , Ardeshir Khazaei & Behrooz Maleki (2004) N,N′,N,N′-
TETRABROMO-BENZENE-1,3-DISULFONYLAMIDE AS A NOVEL REAGENT FOR OXIDATIVE AROMATIZATION OF 1,3,5-
TRISUBSTITUTED PYRAZOLINES UNDER HETEROGENEOUS AND SOLVENT-FREE CONDITIONS, Phosphorus, Sulfur, and Silicon and
the Related Elements, 179:9, 1877-1881, DOI: 10.1080/10426500490466797
To link to this article: http://dx.doi.org/10.1080/10426500490466797
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Phosphorus, Sulfur, and Silicon, 179:1877–1881, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490466797
N,N ꢀ,N,N ꢀ-TETRABROMO-BENZENE-1,3-
DISULFONYLAMIDE AS A NOVEL REAGENT
FOR OXIDATIVE AROMATIZATION
OF 1,3,5-TRISUBSTITUTED PYRAZOLINES
UNDER HETEROGENEOUS AND
SOLVENT-FREE CONDITIONS
Ramin Ghorbani-Vaghei, Davood Azarifar, Ardeshir Khazaei,
and Behrooz Maleki
Department of Chemistry, Faculty of Science, Bu-Ali Sina
University, Hamadan, Iran
(Received December 30, 2003; accepted February 5, 2004)
1,3,5-Trisubstituted pyrazolines were converted to the corresponding
pyrazoles in good yields under heterogeneous and solvent-free condi-
tions by N,Nꢁ,N,Nꢁ-tetrabromo-benzene-1,3-disulfonylamide [TBBDA]
at ambient temperature.
Keywords: Aromatization; oxidative; pyrazolines; TBBDA
INTRODUCTION
Five-membered heterocyclic compounds are important constitutents
that often exist in biologically active natural products and synthetic
compounds of medicinal interest.1 Among them, 1,3,5-trisubstituted
pyrazolines can be easily prepared from phenylhydrazine and chal-
cone derivatives.2 Therefore, oxidative aromatization of pyrazolines
with oxidizing reagents should provide an efficient method for the
preparation of pyrazole derivatives. For this oxidative conversion of
pyrazolines, a limited number of reports exist in the literature, which
include Zr(NO3),3 Pd/C,4 Co (II) and oxygen,5 iodobenzene diacetate,6
lead tetraacetate,7 MnO2,8 potassium permanganate,9 and NBS.10 They
either require too severe of a reaction condition or their use is accom-
panied by products of decompositions and ring scission.
Address correspondence to Ramin Ghorbani-Vaghei, Department of Chemistry, Fac-
ulty of Science, Bu-Ali Sina University, Hamadan, Iran. E-mail: ghorbani@basu.ac.ir
1877

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1878
R. Ghorbani-Vaghei et al.
FIGURE 1
RESULTS AND DISCUSSION
We now wish to report a mild general route for the oxidative dehy-
drogenation of 1,3,5-trisubstituted pyrazolines to the corresponding
pyrazoles using the new reagent N,N,ꢁN,N,ꢁ-tetrabromo-benzene-1,3-
disulfonylamide [TBBDA] (Figure 1), which is relatively easy to make,
under heterogeneous and solvent-free conditions. The reaction proceeds
smoothly and in high yield under fairly mild conditions compared to the
methods reported previously.
The generality of the method is evident from the fact that a wide
variety of substituted pyrazolines underwent smooth oxidation in good
yields.
The reaction of 1,3,5-trisubstituted pyrazolines with TBBDA in
carbon tetrachloride and solid phase at room temperature afforded
pyrazoles without side products (Scheme 1).
SCHEME 1
The results of the conversion of various 1,3,5-trisubstituted pyrazo-
lines to their corresponding pyrazoles under heterogeneous and solvent-
free conditions are presented in Table I.
Solvent-free organic synthesis seems to be a highly useful technique,
especially for industry, and it has many advantages: reduced pollution,
low costs, and simplicity in process and handling (these factors are
especially important in industry).3,11,12

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Pyrazoles
1879
TABLE I Aromatization of 1,3,5-Trisubstituted Pyrazolines with TBBDA
in Solution (I) and Solvent-Free (II) Conditions at Room Temperature
Reagent/
Product
Time (h) Yield (%)
Substrate Producta
R1
R2
I
II
I (II)
I (II)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
2-Naphtyl
2-Naphtyl
Ph
4-CH3C6H4
3-CH3C6H4
4-OCH3C6H4 3-CH3C6H4
4-OCH3C6H4 2-CH3C6H4
4-OCH3C6H4 Ph
2-CH3C6H4
Ph
Ph
3-CH3C6H4
2-ClC6H4
1
1
2.75 0.3 (0.9)
2.75 0.3 (1)
94 (82)
90 (80)
92 (78)
90 (78)
78 (68)
90 (76)
86 (70)
90 (75)
75 (62)
92 (80)
88 (73)
80 (70)
72 (62)
90 (72)
85 (66)
90 (79)
1.25 2.75 0.3 (1)
2.25 3.75 0.6 (1.3)
2
2
2.25 3.25 0.5 (1)
1.75
2
3.5
3
0.3 (0.8)
0.5 (1.25)
3
0.3 (1)
4-OCH3C6H4 4-ClC6H4
3.75 0.6 (1.25)
3-CH3C6H4
2-Naphthyl
2-Naphthyl
2-Naphthyl
3-CH3C6H4
2-CH3C6H4
4-ClC6H4
3-CH3C6H4
4-ClC6H4
2-ClC6H4
4-N(CH3)2C6H4 2.25 3.75 0.4 (0.9)
4-N(CH3)2C6H4
2
2
3.5
3
0.5 (1.25)
0.4 (1)
2.5
2.25 3.5
4
0.3 (1.3)
0.3 (0.9)
2
2
3.75 0.3 (1)
3 0.3 (1.1)
4-OCH3C6H4 2-ClC6H4
aProducts were characterized by their physical properties, comparison with authentic
samples, and by spectroscopic methods.
The advantages of TBBDA are as follows:
1. The preparation of TBBDA is easy.
2. TBBDA is stable in atmospheric conditions for three months.
3. After completion of the reaction and evaporation of solvent, the
sulphonamide is recovered and can be reused many times without
decreasing the yield.
Since TBBDA contains four bromine atoms that are attached to ni-
trogen atoms, it is very possible that this reagent releases Br+, which
can act as an electrophilic species,13 in situ.
CONCLUSIONS
From the results obtained, we find that the described procedure and
the reaction conditions are simple. The new reagent (TBBDA) is stable,
and the recovered reagent can be reused.
Infrared (IR) and nuclear magnetic resonance (NMR) spectra were
recorded using a Shimadzu 435-U-04 spectrophotometer (KBr pellets)
and a 90 MHz Jeol FT-NMR spectrometer, respectively.