Facile synthesis of bromoallenes via N-bromosuccinimide/CH 3SCH3 for the bromination of propargyl alcohols

Article abstract of DOI:10.1016/j.cclet.2012.06.031

A novel and convenient way has been developed for the preparation of bromoallenes from propargyl alcohols by the reagent combination of N-bromosuccinimide and dimethyl sulfide. Bromoallenes with high regioselectivity were obtained in a convenient method.

Full text of DOI:10.1016/j.cclet.2012.06.031

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 999–1002
www.elsevier.com/locate/cclet
Facile synthesis of bromoallenes via N-bromosuccinimide/
CH3SCH3 for the bromination of propargyl alcohols
*
Wen Feng Jiang, Xue Song Liu, Xin Du , Jian Wei Wei, Chun Yu Bao
Department of Chemistry, Dalian University of Technology, Dalian 116023, China
Received 12 April 2012
Available online 19 July 2012
Abstract
A novel and convenient way has been developed for the preparation of bromoallenes from propargyl alcohols by the reagent
combination of N-bromosuccinimide and dimethyl sulfide. Bromoallenes with high regioselectivity were obtained in a convenient
method.
# 2012 Xin Du. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Bromoallene; N-Bromosuccinimide; Propargyl alcohol; Dimethyl sulfide
1. Introduction
Bromoallenes are useful intermediates in organic synthesis, because they provide a key substrate in common
organic synthesis including cyclizations, additions etc. [1–7]. They are also vital in building complex and bioactive
molecules such as medicines and agrochemicals [8,9]. It is necessary to develop a facile and practical method
preparation of bromoallenes. During the past few years, several methods have been reported to prepare bromoallenes.
Including the isomerization of 3-bromopropyne in the presence of cuprous halide [10], substitution of propargylic
derivatives in the presence of Grignard reagents and cuprous halide [11] and intramolecular displacement of
propargylic derivatives connecting with a nucleophilic moiety [12–14]. However, all of these methods have some
shortcomings such as poor yield, hard to operation and toxic halogenating reagent conditions. These previous
researches encouraged us to develop a facile method for preparation of bromoallenes under metal-free, easy of
operation and without of toxic halogenating reagent conditions. Corey et al. reported that the sulfonium salt generated
by combination of N-bromosuccinimide and dimethyl sulfide could convert allyl alcohols to the corresponding
bromides in good yield [15]. So, we investigated on the preparation of bromoallenes and found that propargyl alcohols
could be easily converted to corresponding bromoallenes by a reagent combination of N-bromosuccinimide and
dimethyl sulfide in a mild way. In this letter, we report this efficient, convenient and new method.
2. Experimental
1H and 13C NMR spectra were recorded in CDCl3 solution on a Varian Inova-400 spectrometer (400 MHz for 1H,
100 MHz for 13C). The chemical shifts were reported in ppm downfield (d) from TMS. IR spectra were recorded on a
* Corresponding author.
E-mail address: duxin@dlut.edu.cn (X. Du).
1001-8417/$ – see front matter # 2012 Xin Du. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.06.031

1000
W.F. Jiang et al. / Chinese Chemical Letters 23 (2012) 999–1002
NEXUS FT-IR spectrometer. High-resolution mass spectra were recorded on a Q-TOF mass spectrometry
(Micromass, England) equipped with Z-spray ionization source. TLC was carried out on SiO2 (silica gel 60 F254,
Merck). Flash chromatography was carried out on SiO2 (silica gel 60, 200–300 mesh).
A mixture of propargyl alcohol (1.00 mmol), N-bromosuccinimide (1.45 mmol) and dimethyl sulfide (1.20 mmol)
in 10 mL of dichloromethane was stirred magnetically at room temperature for 3 h. The solvent was removed under
reduced pressure, and then the crude product was purified by flash-column chromatography on silica gel (eluent:
hexane) to give pure bromoallenes in 50–91% yields (Table 1).
Table 1
Preparation of bromoallenes 2 from propargyl alcohols 1 using NBS/CH3SCH3.
Br
HO
Ar
CH3SCH3 (1.4 equiv)
•
R
NBS (1.5 equiv)
CH2Cl2, rt, 3 h
Ar
nBu
1
2
Entry
1
Substrate 1
Product 2
Yield (%)a,b
91
OH
Br
•
nBu
nBu
1c
Br
Br
2c
Br
Br
Br
2
88
HO
nBu
•
nBu
1d
2d
3
4
HO
Br
50
52
nBu
•
nBu
Br
1e
Br
2e
Br
OH
•
nBu
nBu
Br
Br
F
Br
Br
F
2f
1f
5
89
Br
HO
nBu
•
nBu
2g
1g
Br
Br
OH
6
Br
91
•
nAm
nAm
2h
Br
1h
Br
7
8
90
89
Br
OH
•
nBu
nBu
2i
1i
OH
Br
•
nBu
nBu
2i
Cl
1j
Cl

W.F. Jiang et al. / Chinese Chemical Letters 23 (2012) 999–1002
1001
Table 1 (Continued )
Entry
Substrate 1
Product 2
Yield (%)a,b
88
9
Br
OH
•
nBu
nBu
F
1k
2k
F
10
60
OH
Br
•
nHex
nHex
Cl
1l
Cl
2l
a
Isolated yields.
2d–h are unknown compounds, and were characterized by IR, 1H and 13C NMR, and HRMS.
b
2.1. 1-Bromo-4-(3-bromohepta-1,2-dienyl)benzene 2c
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.45 (d, 2H, J = 8.4 Hz), 7.18 (d, 2 Hz, J = 8.4 H), 6.13 (t, J = 2.8 Hz,
1H), 2.50–2.54 (m, 2H), 1.51–1.59 (m, 2H), 1.35–1.42 (m, 2H), 0.90 (m, 3H, J = 7.2 Hz).
2.2. 1-Bromo-3-(3-bromohepta-1,2-dienyl)benzene 2d
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.45 (d, 1H, J = 4 Hz), 7.37–7.39 (m, 1H), 7.18–7.23 (m, 2H), 6.12 (t,
1H, J = 4 Hz), 2.51–2.55 (m, 2H), 1.52–1.59 (m, 2H), 1.36–1.42 (m, 2H), 0.92 (t, 3H, J = 7.2 Hz); 13C NMR
(100 MHz, CDCl3): d 200.2, 135.3, 131.6, 131.3, 131.1, 126.3, 122.9, 99.1, 96.7, 37.6, 30.0, 21.7, 13.7; IR (neat) n:
2957, 2929, 2871, 1952, 1587, 1487, 1464, 1379, 1109, 1071, 1010, 953, 850, 818 cmÀ1; HRMS (EI) calcd. for
C13H14Br2: 327.9473 [M]+; found: 327.9462.
2.3. 1-(3-Bromohepta-1,2-dienyl)-2-bromobenzene 2e
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.55 (dd, 1H, J = 1.2, 8.0 Hz), 7.46 (dd, 1H, J = 1.6, 8.0 Hz), 7.27–
7.31 (m, 1H), 7.08–7.13 (m, 1H), 6.65 (t, 1H, J = 2.8 Hz), 2.51–2.55 (m, 2H), 1.55–1.59 (m, 2H), 1.38–1.42 (m, 2H),
0.91 (t, 3H, J = 7.2 Hz); 13C NMR (100 MHz, CDCl3): d 200.9, 133.2, 132.5, 129.3, 129.3, 127.6, 123.4, 99.1, 96.5,
37.6, 30.0, 21.8, 13.7; IR (neat) n: 2957, 2928, 2860, 1953, 1477, 1465, 1444, 1380, 1050, 831, 751 cmÀ1; HRMS (EI)
calcd. for C13H14Br2: 327.9473 [M]+; found: 327.9462.
2.4. 4-Bromo-2-fluoro-3-(3-bromohepta-1,2-dienyl)benzene 2f
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.23–7.26 (m, 3H), 6.34 (t, 1H, J = 2.8 Hz,), 2.50–2.54 (m, 2H), 1.53–1.57
(m, 2H), 1.37–1.41(m, 2H), 0.91(t, 3H, J = 7.2 Hz); 13C NMR (100 MHz, CDCl3): d 200.8, 159.9 (d, J = 127.0 Hz), 130.1,
128.0, 121.2 (d, J = 92.4 Hz), 120.1, 119.6 (d, J = 24.0 Hz), 96.8, 92.1, 37.8, 29.9, 21.9, 13.9; IR (neat) n: 2960, 2927, 2871,
1952, 1600, 1507, 1234, 1160, 871 cmÀ1; HRMS (EI) calcd. for C13H13FBr2: 345.9357 [M]+; found: 345.9368.
2.5. 1-(3-Bromohepta-1,2-dienyl)-3,5-dibromobenzene 2g
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.54 (s, 1H), 7.37 (m, 2H), 6.05 (t, 1H, J = 2.8 Hz), 2.510–2.55 (m, 2H),
1.53–1.57 (m, 2H), 1.36–1.42 (m, 2H), 0.92 (t, 3H, J = 7.3); 13C NMR (100 MHz, CDCl3): d 200.9, 137.1, 133.5, 129.4,
129.4, 123.4, 98.0, 97.2, 53.6, 37.6, 30.1, 21.9, 13.9, IR (neat) n:2924, 2853, 1952, 1491, 1464, 1378, 1093, 1014, 850 cmÀ1
.
2.6. 1-Bromo-4-(3-bromoocta-1,2-dienyl)benzene 2h
1
Colorless oil; H NMR (400 MHz, CDCl3): d 7.46 (d, 2H, J = 8.4 Hz), 7.11 (d, 2H, J = 8.4 Hz), 6.14 (t, 1H,
J = 2.8 Hz), 2.50–2.54 (m, 2H), 1.55–1.58 (m, 2H), 1.30–1.35 (m, 4H), 0.88 (t, 3H, J = 7.2 Hz); 13C NMR (100 MHz,
CDCl3): d 200.0, 132.0, 132.0, 131.8, 129.9, 129.2, 129.2, 99.4, 37.9, 32.3, 30.8, 27.6, 22.3, 14.0; IR (neat) n: 2957,
2929, 2871, 1952, 1487, 1464, 1109, 1010, 953, 850, 818 cmÀ1
.
2.7. 1-(3-Bromohepta-1,2-dienyl)-4-methylbenzene 2i
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.22 (d, 2H, J = 8 Hz), 7.14 (d, 2H, J = 8 Hz), 6.18 (t, 1H, J = 2.8 Hz),
2.50–2.54 (m, 2H), 2.35 (s, 3H), 1.52–1.60 (m, 2H), 1.36–1.43 (m, 2H), 0.90 (t, 3H, J = 7.2 Hz).

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W.F. Jiang et al. / Chinese Chemical Letters 23 (2012) 999–1002
2.8. 1-(3-Bromohepta-1,2-dienyl)-4-chlorobenzene 2j
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.29–7.33 (m, 2H), 7.22–7.26 (m, 2H), 6.14 (t, 1H, J = 2.8 Hz), 2.50–
2.55 (m, 2H), 1.50–1.59 (m, 2H), 1.34–1.41 (m, 2H), 0.88 (t, 3H, J = 7.2 Hz).
2.9. 1-(3-Bromohepta-1,2-dienyl)-4-fluorobenzene 2k
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.58–7.62 (m, 2H), 7.04–7.08 (m, 2H), 6.63–6.67 (m, 1H), 2.34–2.40
(m, 2H), 1.50–1.59 (m, 2H), 1.24–1.26 (m, 2H), 0.97 (t, 3H, J = 7.2 Hz).
2.10. 1-(3-Bromonona-1,2-dienyl)-2-chlorobenzene 2l
Colorless oil; 1H NMR (400 MHz, CDCl3): d 7.46 (dd, 1H, J = 1.6, 7.6 Hz), 7.36 (dd, 1H, J = 1.6, 7.6 Hz), 7.16–
7.26 (m, 2H), 6.65 (t, 1H, J = 2.8 Hz), 2.50–2.55 (m, 2H), 1.54–1.60 (m, 2H), 1.26–1.38 (m, 6H), 0.87 (t, 3H,
J = 7.2 Hz).
3. Results and discussion
We examined the bromination of propargyl alcohols 1c–l with N-bromosuccinimide (NBS) and dimethyl sulfide
and the results were showed in Table 1. When the reaction of 1c was performed under these conditions, the desired
bromoallene 2c was obtained in 91% yield (entry 1). Good yields of bromoallenes 2d, 2g, 2h, 2i, 2j and 2k were
obtained from the reactions of 1d, 1g, 1h and 1i, and the obtained bromoallenes were 88% (entry 2), 89% (entry 5),
91% (entry 6), 90% (entry 7), 89% (entry 8) and 88% (entry 9) respectively. The bromination of 1e and 1f gave
bromoallene 2e, 2f and 2l in relatively lower yield (50%, 52% and 60% respectively, entry 3, entry 4 and entry 10).
Neither the electron-donating group nor the electron-withdrawing group located at the para or meta position of
aromatic ring significantly influenced the bromorination. However, the group located at the ortho position of aromatic
ring affected the bromorination reaction. Even when R on 1 was changed from n-butyl group to n-hexyl group, the
desired product was still obtained in similar yield. Jacobs and Brill reported that 3-bromopropyne could be converted
to the corresponding bromoallen, but this bromoallen would isomerize back very easily [10]. So an aryl substituent in
the propargyl alcohol is essential for this reaction.
In conclusion, we demonstrated an efficient and convenient method for the preparation of bromoallenes. In this
method, the reagent combination of N-bromosuccinimide and dimethyl sulfide was utilized to convert propargyl
alcohols to bromoallenes for the first time.
Acknowledgments
Thanks financial support from the Fundamental Research Funds for the Central Universities (No. DUT12LK07).
Dr. Bao thanks financial support from the Fundamental Research Funds for the Central Universities (No.
DUT11SM01).
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