N,N-Dibromobenzenesulfonamide: A useful regenrable reagent for bromination of various carbanionic substrates

Article abstract of DOI:10.1080/10426500490459768

N,N-Dibromobenzenesulfonamide(dibromoamine-B), which is prepared easily in high yield, has been employed as effective brominating agent for carbanionic substrates under mild conditions. β-Diketones and β-ketoesters were brominated by this reagent without using any bases. The reagent can be recovered, rebrominated, and reused several times.

Full text of DOI:10.1080/10426500490459768

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Phosphorus, Sulfur, and Silicon and the Related
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N,N-DIBROMOBENZENESULFONAMIDE: A USEFUL
REGENRABLE REAGENT FOR BROMINATION OF VARIOUS
CARBANIONIC SUBSTRATES
a
b
a
Mahmood Tajbakhsh , Ardeshir Khazaei , Majid Shabani Mahalli & Ramin Ghorbani Vaghi
b
a
University of Mazadaran , Babolsar, Iran
b
University of Bu-Ali Sina , Hamadan, Iran
Published online: 16 Aug 2010.
To cite this article: Mahmood Tajbakhsh , Ardeshir Khazaei , Majid Shabani Mahalli & Ramin Ghorbani Vaghi (2004) N,N-
DIBROMOBENZENESULFONAMIDE: A USEFUL REGENRABLE REAGENT FOR BROMINATION OF VARIOUS CARBANIONIC SUBSTRATES,
Phosphorus, Sulfur, and Silicon and the Related Elements, 179:6, 1159-1163, DOI: 10.1080/10426500490459768
To link to this article: http://dx.doi.org/10.1080/10426500490459768
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Phosphorus, Sulfur, and Silicon, 179:1159–1163, 2004
Copyright ꢀC Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490459768
N,N-DIBROMOBENZENESULFONAMIDE: A USEFUL
REGENRABLE REAGENT FOR BROMINATION
OF VARIOUS CARBANIONIC SUBSTRATES
a
b
Mahmood Tajbakhsh, Ardeshir Khazaei,
a
b
Majid Shabani Mahalli, and Ramin Ghorbani Vaghi
a
University of Mazadaran, Babolsar, Iran, and University
b
of Bu-Ali Sina, Hamadan, Iran
(
Received September 11, 2003; accepted October 16, 2003)
N,N-Dibromobenzenesulfonamide(dibromoamine-B), which is pre-
pared easily in high yield, has been employed as effective brominating
agent for carbanionic substrates under mild conditions. β-Diketones
and β-ketoesters were brominated by this reagent without using any
bases. The reagent can be recovered, rebrominated, and reused several
times.
Keywords: β-Dicarbonyl compounds; bromination; dibromoamine-B
Since α-bromo carbonyl componds and 1-bromo-1-alkynes are useful
synthetic intermediates in a number of widely different organic
transformations, numerous methods are available for bromina-
tion of the α-position of carbonyl compounds, alkynes, and other
organic compounds using various brominating reagents. These
1
2
include: KMnO4/HBr/CH3CN and KBrO3/KBr/Dowex for bromi-
nation of 1,3-dicarbonyl substrates, N-bromosuccinimide for bromi-
3
4
nation of carboxylic acids, carbonyl-conjucated alkynes, nitro
5
compounds, N-bromosaccharin for brominating of the benzylic and α-
6
carbonylic positions, triphenyl phosphine and CBr4 for bromination
of primary alkynes,7 benzyl trimethylammonium tribromide, tetra
8
9
10
butylammonium tribromide, trimethylamine-boron bromide, car-
bon tetrabromide,11 1,2-dibromoethane, quinolinium bromochromate
12
We are thankful to the Mazandaran and Bu-Ali Sina Universities Research Council
for the partial support of this work.
Address correspondence to Mahmood Tajbakhsh, Department of Chemistry, School
of Sciences, University of Mazandaran, PO Box 453, Babolsar, Iran. E-mail:
tajbakhsh@umz.ac.ir
1
159

1
160
M. Tajbakhsh et al.
QBC),13 sodium hypobromite-sodium bisulfite (NaBrO3/NaHSO3),
14
(
1
5
and others also were applied for brominating organic compounds. All
these reagents have some disadvantages such as instability, low yield,
toxic reagents, nonselectivity, and tedious work-up.
RESULTS AND DISCUSSION
The N,N-dibromobenzenesulfonamide is a stable crystalline compound
easily prepared16 by brominating directly a sodium carbonate or bi-
carbonate solution of the benzenesulfonamide, which gives an almost
quantitative yield of the pure product. The reaction seems to proceed
in two steps, C6H5SO2NBrNa first dissolving to give a yellow solu-
tion; then the second step occurs, and the yellow dibromide precipiates
(
Scheme 1).
SCHEME 1
Treatment of carbanions with N,N-dibromobenzenesulfonamide
results in the transfer of bromine from nitrogen to carbon. A broad
variety of anions, including β-diketones, β-ketoesters, malonates, nitro-
alkanes, and alkynes can be brominated in high yield (Table I). It should
be mentioned that β-diketones and β-ketoesters are brominated at room
◦
temperatures and 60 C, respectively, without using any base.
The sulfonamide formed in this reaction is easily recovered, rebromi-
nated, and reused several times.
EXPERIMENTAL
The chemicals were obtained from Aldrich Chemical Co. and were
used as received without further purification. Fluka silica gel plates
(
F254) were used for TLC. Elemental analyses (CHN) were performed
on a Perkin-Elmer 2400 CHN analyzer. The IR spectra were recorded
on a Perkin-Elmer 130 spectrophotometer and H NMR spectra were
1
recorded in CCl4 on a Varian (60 and 90 MHz) spectrometer using TMS
as an internal standard.

Dicarbonyl Compounds
1161
TABLE I Bromination of Carbanions with N,N-Dibromobenzenesulfonamide
Temp. Time Yielda
◦
Entry
Substrate
Product
Base
( C)
(min)
(%)
1
2
3
4
5
6
7
8
9
CH3COCH2COCH3
CH3COCH2CO2C2H5 CH3COCBr2CO2C2H5
CH3COCBr2COCH3
—
—
—
NaH
NaH
NaH
NaH
NaH
NaH
NaH
r.t.
60
60
0
0
0
0
0
0
0
30
240
120
60
60
60
60
60
60
60
85
92
85
87
88
88
90
91
95
78
PhCOCH2COPh
CH2(CO2C2H5)2
CH3CH(CO2C2H5)2
PhCH(CO2C2H5)2
NCCH2CO2C2H5
CH3CHNO2CH3
PhC CH
PhCOCBr2COPh
CBr2(CO2C2H5)2
CH3CBr(CO2C2H5)2
PhCBr(CO2C2H5)2
NCCBr2CO2C2H5
CH3CBrNO2CH3
PhC CBr
1
0
C4H9C CH
C4H9C CBr
aYield refers to the isolated productsv that exhibited physical and spectral properties
in accordance with the assigned structure.
Preparation of N,N-Dibromobenzenesulfonamide
In a 250 ml three-necked flask were placed 5 g of benzenesulfon-
amide, 3.6 g of KOH and 25 ml of water; then 10 g of bromine
were added with vigorous stirring. The resulting precipitate of N,N-
dibromobenzenesulfonamide was filtered, washed in water and dried.
The yield was 9.8 (98%).
a) Bromination of Acidic Organic Compound
in the Presence of a Base
A solution of carbanion in anhydrous tetrahydrofuran [prepared in
conventional fashion by adding an 80% dispersion of NaH (20 mmol)
in oil to the substrate (10 mmol) in THF (10 ml)] was added under dry
nitrogen to a stirred slurry of the reagent (10 mmol) in CH2Cl2 (15 ml)
◦
at 0 C. The reaction mixture was allowed to warm to room temperature
and treated with diethyl ether (50 ml). The mixture was then washed
with 0.5 M oxalic acid (30 ml), 10% aqueous potassium hydrogen carbon-
ate (30 ml), and saturated brine (30 ml), dried (MgSO4) and evaporated
under reduced pressure. The residue was washed with n-hexane and
filtered. The filtrate was evaporated to give the pure product in high
yield (Table I). The solid phase was removed by filtration and recrystal-
lized with ethanol and water to give the recovered sulfonamide in 80%
yield.
b) Bromination of β-Diketones and β-Ketoesters
without Base
To a solution of β-diketone or β-ketoester (9 mmol) in carbon tetra-
chloride or cyclohexane (20 ml) was added the reagent (9 mmol), and the

1
162
M. Tajbakhsh et al.
◦
mixture was stirred at room temperature and 60 C, 5 h for β-ketoeseters
and 1/2 h for β-diketones. The progress of the reaction was monitored by
TLC (eluent: hexane/EtoAc 5:1). The reaction mixture was filtered. The
filtrate was evaporated to yield the α,α-dibromo β-diketones as pale
yellow oils. All products were characterized by physical and spectral
methods (M.P. IR, NMR, and CHN analysis).
1
3
,3-Dibromo-2,4-pentandione: H NMR(CCl4)δ = 2.57 (s, 6H,
2
CH3). Anal. Calc. for C5H6Br2O2: C, 23.32; H, 2.21. Found: C, 23.21;
H, 2.29.
1
Ethyl 2,2-dibromo acetoacetate: H NMR(CCl4)δ = 1.15(t, 3H,
CH3 CH2); 2.59 (s, 3H, CH3); 4.37(q, 2H, CH3 CH2)/Anal. Calc. for
C6H8Br2O3: C, 25.00; H, 2.78. Found: C, 25, 10; H, 2.80.
1
2
-Bromo-2-nitropropane: H NMR(CCl4)δ = 2.28 (s, 6H, 2CH3).
Anal. Calc. for C5H6BrNO2: C, 21.43; H, 3.57; N, 8.33. Found: C, 21.68;
H, 3.90; N, 8.50.
Diethyl-2,2-dibromo malonate: 1H NMR(CCl4)δ = 1.25 (t, 6H,
2
2
CH2 CH3); 4 (q, 4H, 2CH3 CH2). Anal. Calc. for C7H10Br2O4: C,
6.41; H, 3.14. Found: C, 26.10; H, 3.00.
1
Diethyl 2-bromo-2-methylmalonate: H NMR(CCl4)δ = 1.3(t,
6
H, 2CH2 CH3); 2(s, 3H, CH3); 4.2(q, 4H, 2CH3 CH2). Anal. Calc. for
C8H13BrO4: C, 37.94; H, 5.14. Found: C, 37.61; H, 4.98.
1
Diethyl 2-bromo-2-phenylmalonate: H NMR(CCl4)δ = 1.2(t, 6H,
2
CH2 CH3); 4(q, 4H, 2CH3 CH2), 7(s, 5H, aromatic H). Anal. Calc. for
C13H15BrO4: C, 49.52; H, 4.76. Found: C, 49.27; H, 4.71.
1
-Bromo-2-phenylacetylene: 1H NMR(CCl4)δ = 6.8(s, 5H, aro-
matic H). Anal. Calc. for C8H5Br: C, 53.04; H, 2.76. Found: C, 52.97;
H, 2.71.
1
Ethyl 2,2-dibromo cyanoaceteate: H NMR(CCl4)δ = 1.25(t, 3H,
CH2 CH3); 4(q, 2H, CH3 CH2). Anal. Calc. for C5H5Br2NO2: C, 22.14;
H, 1.84. N. 5.17, Found: C, 22.52; H, 1.99; N, 5.26.
1
3,3-Dibromo-1.3-diphenyl-1,3-propanedione: H NMR(CCl4)δ =
7
.2(d, 10H, Aromatic H). Anal. Calc. for C15H15Br2O2: C, 47.12; H, 2.62.
Found: C, 47.34; H, 2.51.
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Dicarbonyl Compounds
1163
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