Efficient bromination of alkenes and alkynes using potassium bromide and diacetoxy iodobenzene

Article abstract of DOI:10.1080/00397910801979379

Bromination of alkenes and alkynes has efficiently been carried out at room temperature in short reaction times using KBr and diacetoxy iodobenzene in CH2Cl2-H2O (1:1) to prepare the corresponding trans-dibromo compounds in excellent yields. Copyright Taylor & Francis Group, LLC.

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Efficient Bromination of
Alkenes and Alkynes Using
Potassium Bromide and
Diacetoxy Iodobenzene
Biswanath Das a , Yallamalla Srinivas a , Chittaluri
Sudhakar a , Kongara Damodar a & Ravirala Narender
a
a Organic Chemistry Division I , Indian Institute of
Chemical Technology , Hyderabad, Andhra Pradesh,
India
Published online: 22 Dec 2008.
To cite this article: Biswanath Das , Yallamalla Srinivas , Chittaluri Sudhakar ,
Kongara Damodar & Ravirala Narender (2008) Efficient Bromination of Alkenes
and Alkynes Using Potassium Bromide and Diacetoxy Iodobenzene, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 39:2, 220-227, DOI: 10.1080/00397910801979379
To link to this article: http://dx.doi.org/10.1080/00397910801979379
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Synthetic Communications1, 39: 220–227, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910801979379
Efficient Bromination of Alkenes and Alkynes
Using Potassium Bromide and Diacetoxy
Iodobenzene
Biswanath Das, Yallamalla Srinivas, Chittaluri Sudhakar,
Kongara Damodar, and Ravirala Narender
Organic Chemistry Division I, Indian Institute of Chemical Technology,
Hyderabad, Andhra Pradesh, India
Abstract: Bromination of alkenes and alkynes has efficiently been carried out at
room temperature in short reaction times using KBr and diacetoxy iodobenzene
in CH2Cl2-H2O (1:1) to prepare the corresponding trans-dibromo compounds in
excellent yields.
Keywords: Alkene, alkyne, DIB, trans-dibromo compound
The bromination of alkenes and alkynes is an important transformation
in organic synthesis.[1] The protection and deprotection of double bonds
via a bromination–debromination strategy can conveniently be utilized in
synthetic routes.[2] The bromine group can also easily be converted into
other functionalities.[1] Additionally, the brominated alkenes are useful
precursors to organometallic reagents.[3] The classical bromination
involves the use of hazardous elemental bromine.[1] To avoid this reagent,
several other protocols for bromination have been discovered.[4–10] How-
ever, the occurrence of side reactions, low selectivity, poor yields, and
application of costly reagents are drawbacks in several methods. Here
we report an efficient method for bromination of alkenes and alkynes.
In continuation of our work[11–13] on the development of useful syn-
thetic methodologies, we have observed that the bromination of alkenes
Received December 22, 2007.
Part 158 in the series, ‘‘Studies on Novel Synthetic Methodologies.’’
Address correspondence to B. Das, Organic Chemistry Division I, Indian Insti-
tute of Chemical Technology, Uppal Road, Hyderabad 500 007, Andhra Pradesh,
India. E-mail: biswanathdas@yahoo.com
220

Bromination of Alkenes and Alkynes
221
Scheme 1. Bromination of alkenes and alkynes using KBr and diacetoxy
iodobenzene.
and alkynes to the corresponding vicinal dibromo compounds can easily
be carried out using KBr and diacetoxy iodobenzene (DIB) in CH2Cl2-
H2O (1:1) (Scheme 1).
In recent years, hypervalent iodine reagents have gained much
importance in organic synthesis because of their interesting activity,
ready availability, and easy handling.[14,15] Previously we applied DIB
to the preparation of isoxazolines from activated alkenes by treatment
with aldoximes.[16] We have now discovered that this reagent in combi-
nation with KBr is highly effective for bromination of various alkenes
and alkynes (Table 1). a,b- Unsaturated carbonyl compounds and
cycloalkenes were also efficiently brominated.
The conversion occurred at room temperature under mild reaction
conditions. The reaction was complete within 15–30 min and the yields
were excellent (92–98%). CH2Cl2-H2O (1:1) was found to be a suitable
medium for this conversion.
The bromination of alkenes and alkynes (except phenyl acetylene)
produced solely the trans-vicinal dibromo compounds. Phenyl acetylene
afforded the corresponding trans-(E)-dibromo derivative as the major
product (84%) along with the cis-(Z)-dibromo compound in minor quan-
tity (12%). The bromonium ion (Brþ ) generated in situ by the reaction of
KBr and DIB reacts with the alkene or alkyne to form a cyclic bromo-
nium ion intermediate, which is attacked by a bromide ion from the
reverse side, forming selectively the trans-vicinal dibromo compound.
No tetrabromo derivatives were obtained from alkynes.
In conclusion, we have developed a simple, novel, mild, and efficient
method for high-yielding preparation of vicinal trans-dibromo com-
pounds from alkenes and alkynes by treatment with a combination of
KBr and DIB. The molecular bromine that is toxic can thus be avoided.
A new synthetic utility of hypervalent iodine has also been disclosed.

222

223

224

Bromination of Alkenes and Alkynes
225
EXPERIMENTAL
General
A mixture of alkene or alkyne (0.5 mmol), KBr (1.5 mmol), and DIB
(0.5 mmol) in CH2Cl2-H2O (1:1) (5 mL) was stirred at room temperature.
The reaction was monitored by thin-layer chromatography (TLC). After
completion, the organic layer was separated, washed with saturated aque-
ous NaHCO3 solution (3 ꢀ 5 mL), and dried over anhydrous Na2SO4.
The solvent was removed under reduced pressure. The residue was sub-
jected to column chromatography (silica gel, hexane–EtOAc) to obtain
pure dibromo product.
The spectral (1H NMR and MS) and analytical data of some rep-
resentative dibromo compounds are given next.
Data
1,2-Dibromo-1-(4-bromo)-1-phenylethane (Table 1, entry 3)
ꢁ
1
White solid, mp 56–58 C. H NMR (CDCl3, 200 MHz): d 7.55 (d, 2H,
J ¼ 8.0 Hz), 7.35 (d, 2H, J ¼ 8.0 Hz), 5.05 (dd, 1H, J ¼ 9.0, 5.0 Hz),
4.04 (dd, 1H, J ¼ 12.0, 5.0 Hz), 3.94 (dd, 1H, J ¼ 12.0, 9.0 Hz); FABMS:
m=z 363, 365, 367, 369 [M þ Na]þ . Anal. calcd. for C8H7Br3: C, 28.23; H,
2.06. Found: C, 27.87; H, 1.98.
2,3-Dibromo-1-phenyl-3-(4-chloro)-phenyl propane-1-one
(Table 1, entry 6)
ꢁ
1
White solid, mp 160–161 C. H NMR (CDCl3, 200 MHz): d 8.06 (d, 2H,
J ¼ 8.0 Hz), 7.80–7.30 (m, 7H), 5.71 (d, 1H, J ¼ 9.0 Hz), 5.57 (d, 1H,
J ¼ 9.0 Hz); FABMS: m=z 423, 425, 427, 429 [M þ Na]þ . Anal. calcd.
for C15H11OBr2Cl: C, 44.94; H, 2.75. Found: C, 43.64; H, 2.67.
2,3-Dibromo-3-(4-methoxy)-phenyl-methyl propanoate
(Table 1, entry 7)
Viscous, 1H NMR (CDCl3, 200 MHz): d 7.92 (d, 2H, J ¼ 8.0 Hz), 6.94 (d,
2H, J ¼ 8.0 Hz), 3.91 (s, 2H), 3.86 (s, 3H), 2.56 (s, 3H); FABMS: m=z
357, 359, 361 [M þ Na]þ . Anal. calcd. for C11H12O2Br2: C, 39.52; H,
3.59. Found: C, 38.49; H, 3.51.

226
B. Das et al.
2,3-Dibromo-ethyl propanoate (Table 1, entry 8)
1
Viscous, H NMR (CDCl3, 200 MHz): d 4.36 (dd, 1H, J ¼ 10.0, 4.0 Hz),
4.30 (q, 2H, J ¼ 7.0 Hz), 3.92 (dd, 1H, J ¼ 12.0, 10.0 Hz), 3.66 (dd, 1H,
J ¼ 12.0, 4.0 Hz), 1.36 (t, 3H, J ¼ 7.0 Hz); FABMS: m=z 281, 283, 285
[M þ Na]þ . Anal. calcd. for C5H8O2Br2: C, 23.25; H, 3.10. Found: C,
22.09; H, 3.16.
1,2-Dibromo-tetradecane (Table 1, entry 12)
1
Viscous, H NMR (CDCl3, 200 MHz): d 4.13 (m, 1H), 3.84 (dd, 1H,
J ¼ 12.0, 4.0 Hz), 3.57 (dd, 1H, J ¼ 12.0, 10.0 Hz), 2.15 (m, 1H), 1.76
(m, 1H), 1.64–1.20 (m, 20H), 0.88 (t, 3H, J ¼ 7.0 Hz); FABMS: m=z
377, 379, 381 [M þ Na]þ . Anal. calcd. for C14H28Br2: C, 47.46; H,
7.91. Found: C, 46.34; H, 7.84.
2,3-Dibromo-propyl-(4-chloro)-phenyl-ether (Table 1, entry 13)
Viscous, 1H NMR (CDCl3, 200 MHz): d 7.24 (d, 2H, J ¼ 8.0 Hz), 6.85 (d,
2H, J ¼ 8.0 Hz), 3.85 (d, 2H, J ¼ 6.0 Hz), 4.45–4.26 (m, 3H); FABMS:
m=z 349, 351, 353, 355 [M þ Na]þ . Anal. calcd. for C9H9OBr2Cl: C,
33.08; H, 2.76. Found: C, 32.83; H, 2.82.
1,2-Dibromo-1-heptene (Table 1, entry 15)
Viscous, 1H NMR (CDCl3, 200 MHz): d 6.39 (s, 1H), 2.60 (t, 2H,
J ¼ 7.0 Hz), 1.63–1.51 (m, 2H), 1.40–1.23 (m, 4H), 0.88 (t, 3H,
J ¼ 7.0 Hz); FABMS: m=z 277, 279, 281 [M þ Na]þ . Anal. calcd. for
C7H12Br2: C, 33.07; H, 4.72. Found: C, 31.96; H, 4.66.
ACKNOWLEDGMENTS
The authors thank Council of Scientific and Industrial Research and
University Grants Commission, New Delhi, for financial assistance.
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