H-β-zeolite catalyzed synthesis of β-bromostyrenes from styrene bromohydrins

Article abstract of DOI:10.1016/j.tetlet.2014.01.118

Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.

Full text of DOI:10.1016/j.tetlet.2014.01.118

Tetrahedron Letters 55 (2014) 1793–1795
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
H-b-zeolite catalyzed synthesis of b-bromostyrenes from styrene
bromohydrins
Venkatanarayana Pappula, Ramachandra Reddy Donthiri, Darapaneni Chandra Mohan,
⇑
Subbarayappa Adimurthy
Academy of Scientific & Innovative Research, CSIR–Central Salt & Marine Chemicals Research Institute, G.B. Marg, Bhavnagar 364 002, Gujarat, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of b-bromostyrenes from styrene bromohydrins using H-b-zeolite as catalyst under moderate
conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.
Ó 2014 Elsevier Ltd. All rights reserved.
Received 4 January 2014
Revised 23 January 2014
Accepted 25 January 2014
Available online 1 February 2014
Keywords:
b-Bromostyrenes
H-b-zeolite
Dehydration
Heterogeneous catalysis
Synthetic methods
b-Aryl vinyl halides are key intermediates in the synthesis of
fine chemicals and numerous biologically active compounds.1 They
have traditionally been prepared through the classical Hunsdiecker
reaction involving the halo decarboxylation of cinnamic acid deriv-
atives,2 olefination of aromatic aldehydes,3 homologation of benzyl
bromides with dihalomethanes,4 and reduction of 1,1-dihaloalk-
enes.5 A powerful alternative strategy involves the intermediates
of vinylboranes,6 vinylsilanes,7 vinylstannanes,8 and vinylzirco-
nates9 with halogen analogues. However, with few exceptions,
these methods require expensive and/or rare metal catalysts
(Scheme 1). Therefore, improvements to achieve environmentally
benign and cost-effective approaches would be highly desirable.
Due to an appealing application of b-aryl vinyl bromides in the
synthesis and our interest on environment-friendly brominations
since a decade,10 we intended to obtain these vinyl intermediates
via selective dehydration of corresponding bromohydrins. Our pre-
vious efforts on selective intramolecular dehydration of styrene
bromohydrin with various Brønsted acid catalysts led to the
undesired condensation product ether instead of the desired b-
bromostyrene.11 This precedent enforced us to further investigate
the selective catalytic system to access b-bromostyrenes.12 Herein,
Bronsted acid sites in the micropores and Lewis active acid sites
on the external surface.13 Because of these properties of H-b-zeo-
lite, it has been used as heterogeneous catalyst in organic
transformations.14,15
First, the selective dehydration was performed by choosing
styrene bromohydrin (1a) as model substrate and H-b-zeolite as
heterogeneous acid catalyst and the results are illustrated in
Table 1. After the reaction of 1a in toluene with 5% (w/w) of H-b-
zeolite at 100 °C for 12 h, the desired product 2a was detected in
11% GC yield (Table 1, entry 1). When the catalyst loading was in-
creased to 10% and 20% (w/w), the yield of 2a was increased to 20%
and 30%, respectively (Table 1, entries 2 and 3). A clear improve-
ment was observed when the reaction temperature was raised
from 100 to 120 °C, and 2a was obtained in 55% isolated yield
(Table 1, entry 4). Furthermore, when chlorobenzene was utilized
as solvent at 120 °C, 2a was obtained in 72% isolated yield (Table 1,
entry 5). Decrease of the catalyst loading and temperature
decreased the yield (Table 1, entries 6–8). Other solvents and neat
conditions were not favorable for this transformation (Table 1,
entries 9–14). When the reaction time was decreased to 9 and
6 h, the same (72%) yield of 2a was obtained (Table 1, entries 15
and 16). Based on the above screening results, the optimal condi-
tions can be determined (Table 1, entry 15). To the best of our
knowledge the selective catalytic dehydration of bromohydrins
to access b-bromostyrenes has never been reported.
we describe
a strategy for the selective dehydration of
bromohydrins that enable us to access b-aryl vinyl bromides using
H-b-zeolite as heterogeneous catalyst. H-b-zeolite possesses
With the optimized conditions in hand, the substrate scope of
the reaction was investigated (Table 2). All substrates examined
⇑
Corresponding author. Tel.: +91 278 2567760; fax: +91 278 2567562.
E-mail address: adimurthy@csmcri.org (A. Subbarayappa).
http://dx.doi.org/10.1016/j.tetlet.2014.01.118
0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.

1794
V. Pappula et al. / Tetrahedron Letters 55 (2014) 1793–1795
Table 2
Priveous Works
Scope for the synthesis of b-bromostyrenesa
M
E/Zb
Ph
Entry
1
Product
Isolated yield (%)
72
COOH
Ph
Br
E
Ph
Br
C
R = H;
2a
85:15
A
R
Br
Ph
2
3
4
–CH3
–tBu
–Ph
–Br
–CI
2b
2c
2d
2e
2f
64
77
60
66
72
11
87:13
84:16
88:12
84:16
85:15
71:29
B
D
H
Br
Br
Ph
O
Ph
5
Current Work
OH
6
Hunsdiecker reaction
Takai olefination
A:
B:
7c
–NO2
2g
Br
C: Homologation of benzyl bromides
Ph
8
9
Br
R = –Br
–CI
2h
2i
70
67
84:16
84:16
Reduction of 1,1-dihaloalkenes
D:
Dehydration reaction
E: Halogenation reaction
10
11
–F
–CH3
–NO2
2j
2k
21
52
55
17
76:24
88:12
74:26
R
Scheme 1.
12c
13
14
15
16
R = –Br
–Cl
–CH3
–F
2m
2n
2o
2p
63
62
66
38
80:20
83:17
83:17
99:01
Br
Br
Table 1
Optimization of reaction conditionsa
R
OH
Br
+ H2O
H-β-zeolite
17
18
2q
2r
65
57
83:17
81:19
Br
solvent, temp,12 h
2a
1a
Br
Entry H-b-zeolite
Solvent
Temp (°C) Yield (%) E/Zb
(wt%)
Cl
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15c
5
10
20
20
20
10
20
20
10
10
20
10
10
10
20
Toluene
Toluene
Toluene
Toluene
Chloro benzene
Chloro benzene
Chloro benzene
Chloro benzene
Benzene
100
100
100
120
120
120
80
100
90
110
90
11b
20b
30b
55
72
66
81:19
90:10
73:27
90:10
85:15
84:16
76:24
82:18
78:22
80:20
79:21
80:20
79:21
78:22
85:15
19
2s
70
100:–
Br
Cl
Ph
20
21
22
2t
78
—
—
—
17
57
Br
36b
47b
24b
10b
12b
14b
72
Br
Br
2u
2v
77
Xylene
Cyclo hexane
Cyclo hexane
CCI4
Neat
Chloro
80
75
100
120
61d
a
b
c
Conditions: See Table 1 entry 15.
E/Z ratio determined by 1H NMR.
Reaction time 12 h.
benzene
Chloro benzene
16c
20
120
72
85:15
29% yield of naphthalene was observed along with 2v by 1H NMR.
d
The bold values represent the optimized conditions.
a
Conditions: 1a (1.25 mmol), solvent (1.0 mL), isolated yield unless otherwise
stated.
Yield and E/Z ratio were determined based on GC–MS (area%).
Reaction time 6 and 9 h in entries 15 and 16, respectively.
The stability and reusability of H-b-zeolite catalyst for the selec-
b
c
tive dehydration of styrene bromohydrin under optimized condi-
tions have been examined at gram scale (10 mmol). After each
cycle, the catalyst was separated from the reaction mixture by fil-
tration, reactivated by simple treatment with mineral acid,16 and
subsequently reused under identical reaction conditions.17 The
recyclability data indicates that there is no considerable loss of cat-
alytic activity for at least three repeated cycles (Fig. 1). However, in
each recycle the E/Z ratio of the product remains the same (85/15).
When the catalyst is reused without activation, the reaction was
incomplete even after long reaction time compared to activated
catalyst. Probably, it may be due to the acidic character of the cat-
alyst. As the number of recyclability increases its acidic property
slightly decreases, presumably due to leaching of H+ ions. Hence,
a slight decrease in the catalytic activity was observed. However,
the catalytic activity can be restored by simple treatment of the
catalyst with mineral acids at room temperature. The H-b-zeolite
catalyst utilized in the present study is commercially available.
The fresh and reused catalysts have been characterized by XRD
(Fig. 2) and FT-IR analysis (see Fig. S1 in the Supporting informa-
tion). The XRD analysis of the reused catalyst well matched with
the fresh catalyst, this study also suggests that crystallinity and
phase purity of the reused catalyst are comparable.
under optimized conditions afford the corresponding products in
moderate to good yield. The selective dehydration of para-substi-
tuted styrene bromohydrins with both electron-efficient and elec-
tron-deficient appears to be invariant to the electronic properties
as the reaction proceeded smoothly to give the corresponding
products (2b–2f) in moderate to good yield 60–77%. However,
the strong electron withdrawing nitro group at para-position gave
low yield (11%) of product 2g. The electron rich substituents either
at ortho or meta position of styrene bromohydrin provided moder-
ate to good yields of b-bromostyrenes (2h–2k) and (2m–2o)
respectively. Electron withdrawing groups at both ortho/meta sub-
stituents also gave products 2l and 2p in low yield 17% and 38%,
respectively. Disubstituents at 2,5- and 2,4- and sterically demand-
ing disubstituents at 2,6 positions of styrene bromohydrins were
readily transformed into corresponding products (2q–2s).
Alpha-substituted b-bromostyrene (2t) can also be obtained in
good yield (78%). Interestingly, the cyclic vinyl bromides such as
2-bromo-1H-indene (2u) and 3-bromo-1,2-dihydronaphthalene
(2v) also resulted in 77% and 32% yield, respectively.

V. Pappula et al. / Tetrahedron Letters 55 (2014) 1793–1795
1795
Acknowledgments
72
68
V.P, R.R.D, and D.C.M are thankful to UGC New Delhi, India for
their fellowships. We thank, CSIR (CS-0123 INDUS MAGIC) and
DST, Govt. India (SR/S1/OC-13/2011) for financial support[CSMCRI,
PRIS No. 114/2013].
65
63
Supplementary data
Supplementary data (detailed experimental procedure and
spectroscopic data) associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2014.01.
118.
fresh
1
2
3
References and notes
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Figure 1. Recyclability study of catalyst.
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Figure 2. XRD Analysis of catalyst.
The present catalytic system has the following significant
advantages over previously reported procedures for the synthesis
of b-bromostyrenes: (i) atom efficiency and no by-product forma-
tion [only water is eliminated in the process], (ii) applicable for a
variety of substituted styrenes (including alpha substituted deriv-
atives), (iii) H-b-zeolite catalyst is inexpensive and commercially
available, and (iv) easy separation of the catalyst and it can be
reused up to three consecutive cycles without appreciable loss of
catalytic activity.
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In conclusion we have developed a green catalytic method for
the synthesis of b-bromostyrenes through intramolecular dehydra-
tion of bromohydrins using H-b zeolite as heterogeneous and
recyclable catalyst. The present method is applicable to a variety
of substituted styrene derivatives under moderate conditions.
The present approach highlights a useful alternative to the tradi-
tional Hunsdiecker reaction involving the halo decarboxylation of
cinnamic acid derivatives. Notably, water is the only by-product
generated, making this transformation more atom-economical
and greener, than the traditional methods.
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16. The recovered catalyst was activated with mineral acid, which showed same
selectivities as with fresh catalyst than the unactivated catalyst.
17. Synthesis of b-bromostyrene 2a: In a 25 mL round bottomed flask, 250 mg
(1.2 mmol) of 2-bromo 1-phenyl ethanol (1a), 50 mg (20 W/W%) H-b-zeolite,
and 1.0 mL of chlorobenzene were placed. The reaction flask was placed in an
oil bath at120 °C for 6 h; the progress of the reaction was monitored by TLC.
After completion of the reaction, the flask was allowed to attain room
temperature, and filtered through Whatman filter paper and washed with
10 mL of diethyl ether. Upon removal of the solvent under reduced pressure,
the left out residue was purified by column chromatography on silica gel (200–
400 mesh) and hexane as eluent to obtain 2a in (0.16 g) 72% yield.