Tetrabutyl ammonium bromide-mediated benzylation of phenols in water under mild condition

Article abstract of DOI:10.1016/j.tet.2014.01.004

Benzylation of phenol was successfully achieved in water under room temperature mediated by tetrabutylammonium bromide (TBAB) for only 2 h affording the corresponding benzyl phenyl ether with good to excellent yields. This protocol is very efficient, simple, avoiding catalysts, easy to work-up after reaction, and especially 'green'.

Full text of DOI:10.1016/j.tet.2014.01.004

Tetrahedron 70 (2014) 2669e2673
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Tetrabutyl ammonium bromide-mediated benzylation of phenols in
water under mild condition
,
a
a,
Hailei Wang a, Yuping Ma b, Heng Tian a, Ajuan Yu a , Junbiao Chang , Yangjie Wu
*
*
a The College of Chemistry and Molecular Engineering, Key Laboratory of Chemical Biology and Organic Chemistry of Henan, Zhengzhou University,
Zhengzhou 450052, PR China
b China Tobacco Industrial Co. Ltd., Zhengzhou 450052, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Benzylation of phenol was successfully achieved in water under room temperature mediated by tetra-
butylammonium bromide (TBAB) for only 2 h affording the corresponding benzyl phenyl ether with good
to excellent yields. This protocol is very efficient, simple, avoiding catalysts, easy to work-up after re-
action, and especially ‘green’.
Received 8 September 2013
Received in revised form 27 December 2013
Accepted 3 January 2014
Available online 9 January 2014
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
Benzylation
Phenols
Water
Phase transfer catalysis (PTC)
1. Introduction
the water. Therefore, performing organic reactions in water may
profit by these beneficial aspects. So, the concept of water mediated
Benzylation of phenol is a very important organic reaction and
was first reported by McKillop using dichloromethane as a solvent
in 1974.1 Since then, a wide variety of procedures have been de-
veloped to reach this goal, including the use of crown ethers,2
phase-transfer catalysis (PTC),3 ionic liquids,4 microwave method,
and so on.5 However, most of protocols suffer rigorous conditions,
such as the strong base and high temperature. Furthermore, many
of the above-mentioned methods carried out in toxic, volatile, and
flammable organic solvent, examples of dichloromethane, aceto-
nitrile, and 2-methyltetrahydrofuran or in high boiling point polar
solvent, such as N,N-dimethylformamide. Thus, the development of
an efficient, safe, and environmentally friendly method of benzy-
lation of phenol is very attractive.
Organic reactions in water have recently attracted great in-
terests. The substitution of organic solvent as reaction media by
water minimizes the environmental impact, besides lowering the
cost and decreasing operational danger. In addition to economic
and human aspects, water presents many physico-chemical prop-
erties that can be useful in the reactions, such as high polarity, ion
solvating capacity, and the ability to form hydrogen bonds to form
a structured liquid, and to aggregate apolar molecules dissolved in
nucleophilic displacement reactions, as a green protocol, needs
more attention. In recent years, a variety of PTCs involving the
application of tetrabutyl ammonium bromide (TBAB) has been
successfully conducted using water or co-solvent for reaction me-
dium.6 Interested in this area, in this paper we reported the use of
tetrabutyl ammonium bromide (TBAB) as the phase transfer cata-
lyst for the preparation of benzyl phenyl ether in aqueous media
under mild conditions.
2. Results and discussion
To extend applicability of water as a green reaction media and
for the search of facile benzylation method, we initially in-
vestigated on the model reaction of benzyl bromide and phenol in
pure water to optimize the reaction conditions. To our delight, an
86% isolated yield of desired product was obtained with 1 equiv of
tetrabutyl ammonium chloride (TBAC) as the phase transfer cata-
lyst, K3PO4 as the base at room temperature for 2 h (Table 1, entry
1). Phenol underwent O-alkylation instead of extensive C-alkyl-
ation in water under our weak base conditions, which was sharp in
contrast to the existed report.5m,n Surprisingly, the yield was dra-
matically improved up to 98% when TBAB instead of TBAC was used
as a phase transfer catalyst (Table 1, entry 2). Other inorganic bases,
such as K2HPO4$3H2O, NaOH, KOH, and K2CO3 can also be used in
this reaction instead of K3PO4 (Table 1, entries 3e6). Among all the
* Corresponding authors. Fax: þ86 371 6776 6667; e-mail addresses: yuajuan@
zzu.edu.cn (A. Yu), wyj@zzu.edu.cn (Y. Wu).
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.01.004

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H. Wang et al. / Tetrahedron 70 (2014) 2669e2673
Table 2 (continued)
Table 1
Optimization of reaction conditionsa
Entry
Phenol
Product
Yieldb(%)
79
O
OH
Phase transfer catalyst
Br
6
+
1f
base, H2O
3fa
1a
2a
3a
7
8
93
98
Entry
Phase transfer catalyst
Base
t (h)
Yieldb (%)
1g
1h
3ga
1
2
3
4
5
6
7
8
9
TBAC
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
d
K3PO4
K3PO4
K2HPO4$3H2O
NaOH
KOH
2
2
2
2
2
2
2
2
1
2
83
98
73
39
64
3ha
3ia
K2CO3
90
K3PO4 (1.5 equiv)
K3PO4 (1.2 equiv)
K3PO4 (1.5 equiv)
K3PO4 (1.5 equiv)
97c
90c
89c
d
9
82
99
1i
10
a
Unless otherwise noted, the reaction conditions were as follows: phenol
(0.5 mmol), benzyl bromide (1.2 equiv), phase transfer catalyst (1.0 equiv), base
(2.0 equiv), and water (2 mL), room temperature, air, in a sealed tube.
10
b
Isolated yields.
TBAB (0.5 equiv).
1j
c
3ja
bases, the K3PO4 gave the highest yield (Table 1, entry 2). An iso-
lated yield of 97% was obtained even when the quantities of TBAB
and the base were decreased to 0.5 and 1.5 equiv, respectively
(Table 1, entries 7, 8). However, the yield of the reaction was de-
creased when shorten the time to 1 h (Table 1, entry 9). No ben-
zylation of phenol to benzyl phenyl ether was observed under the
reaction conditions in the absence of phase transfer catalyst (Table
1, entry 10).
11
12
98
88
1k
3ka
1l
3la
With the optimized conditions in hand, the substrate scope of
commercially available phenols was investigated and the results
were summarized in Table 2. Generally speaking, the reaction
proceeded smoothly in the presence of a variety of functional
groups including electron-donating, electron-neutral, and electron-
withdrawing, such as methyl, methoxyl, chloro, bromo, tertiary
butyl, formacyl, and cyano groups. It was noteworthy that the
sterically hindered substrates also delivered the desired product in
high yields (Table 2, entries 7e10). Especially, even for the 1,2-
benzenediol that bearing two hydroxyl in ortho-position could
also give the corresponding product in high yield of 90% (Table 2,
13
90
86
1m
1n
3ma
3na
14
15
66
76
1o
3oa
Table 2
Benzylation of benzyl bromide with different phenolsa
16
Entry
1
Phenol
Product
Yieldb(%)
97
1p
3pa
a
Reaction conditions: phenol (0.5 mmol), benzyl bromide (1.2 equiv), TBAB
(0.5 equiv), base (1.5 equiv), and water (2 mL), room temperature, 2 h, air, in a sealed
tube.
1a
3aa
b
Isolated yields.
2
3
4
5
74
99
99
99
1b
3ba
entry 13). It would be specially mentioned that naphthol 1o and
heterocycle phenol 1p were both tolerated and afforded the
etherification products in moderate yields (Table 2, entries 14e16).
In order to make a more systematic study, different kinds of
groups on the phenyl ring in the benzyl bromide were also exam-
ined. As shown in Table 3, the reaction was not significantly affected
by the steric effect of the phenols (Table 3, entries 6, 7, 11). For
example, the benzylation of 1a with ortho-benzyl bromide pro-
ceeded smoothly, affording the corresponding products 3ah in al-
most quantitative yield. Also the electronic properties of the groups
at the aryl moiety of benzyl bromides had some effect on the re-
action. Generally, the benzyl bromides bearing electron-
1c
3ca
3da
3ea
1d
1e

H. Wang et al. / Tetrahedron 70 (2014) 2669e2673
2671
withdrawing groups produced the corresponding products in
4. Experimental section
4.1. General details
slightly higher yields. Benzyl bromides with electron-deficient
substituents, which were more prone to undergo nucleophilic
substitution reaction with phenol than the analogs with electron-
rich groups.
1H NMR, 13C NMR spectra were recorded on a Bruker DPX-400
spectrometer with CDCl3 as the solvent and TMS as an internal
standard. IR spectra was measured using a NEXUS 470 FT-IR ap-
paratus. High-resolution mass spectra were ensured on a MALDI-
FTMS. Benzyl bromide that with a substituent on the phenyl ring
was synthesized according to the reported literature.7 The other
chemicals were bought from commercial sources and used as re-
ceived unless otherwise noted. Solvents, such as ethyl acetate, pe-
troleum ether, and dichloromethane were used for column
chromatography and thin-layer chromatography without further
purification.
Table 3
Benzylation of different benzyl bromide with phenola
Entry
1
Benzyl bromide
Product
Yieldb (%)
82
2b
3ab
3ac
3ad
3ae
3af
2
3
4
5
6
84
76
95
98
83
2c
4.2. General procedure for benzylation of phenols
Phenol (0.5 mmol), benzyl bromide (1.2 equiv), TBAB (0.5 equiv),
K3PO4 (1.5 equiv), and water (2 mL) were added to a reaction vessel.
The mixture was stirred at room temperature for 2 h under air. After
the reaction was completed, the mixture was diluted with water
and extracted with CH2Cl2 (15 mLꢀ3). The combined organic layer
was dried with anhydrous sodium sulfate and concentrated under
reduced pressure. The residue was purified by thin layer chroma-
tography (TLC) on silica gel GF254 (ethyl acetate/petroleum ether) to
give the pure product.
2d
2e
2f
4.2.1. Benzyl phenyl ether (3aa).5d 1H NMR (400 MHz, CDCl3):
d
7.48e7.31 (m, 7H), 7.03e6.98 (m, 3H), 5.10 (s, 2H); 13C NMR
2g
2h
3ag
(100 MHz, CDCl3)
114.9, 70.0.
d 158.9, 137.2, 129.5, 128.6, 128.0, 127.5, 121.0,
7
98
4.2.2. Benzyl 4-methylphenyl ether (3ba).8 1H NMR (400 MHz,
3ah
3ai
CDCl3):
d
7.42e7.27 (m, 5H), 7.06 (d, J¼8.3 Hz, 2H), 6.86 (d, J¼8.4 Hz,
2H), 5.01 (s, 2H), 2.27 (s, 3H); 13C NMR (100 MHz, CDCl3)
137.4, 130.2, 130.0, 128.6, 127.9, 127.5, 114.8, 70.2, 20.6.
d 156.8,
8
93
95
99
2i
4.2.3. Benzyl 4-methoxyphenyl ether (3ca).5d 1H NMR (400 MHz,
CDCl3):
7.42e7.35 (m, 4H), 7.30 (t, J¼7.1 Hz, 1H), 6.92e6.88 (m,
2H), 6.84e6.80 (m, 2H), 5.01 (s, 2H), 3.76 (s, 3H); 13C NMR
d
9
(100 MHz, CDCl3):
114.7, 70.8, 55.8.
d 154.0, 153.0, 137.4, 128.6, 127.9, 127.5, 115.9,
2j
3aj
4.2.4. Benzyl 4-chlorophenyl ether (3da).5j 1H NMR (400 MHz,
10
CDCl3):
d 7.42e7.30 (m, 5H), 7.24e7.20 (m, 2H), 6.90e6.87 (m, 2H),
2k
3ak
5.03 (s, 2H); 13C NMR (100 MHz, CDCl3):
128.1, 127.5, 125.9, 116.2, 70.4.
d 157.4, 136.6, 129.4, 128.7,
11
90
4.2.5. Benzyl 4-bromophenyl ether (3ea).5d 1H NMR (400 MHz,
CDCl3):
7.43e7.32 (m, 7H), 6.87e6.85 (m, 2H), 5.04 (s, 2H); 13C
2l
3al
d
a
Reaction conditions: phenol (0.5 mmol), benzyl bromide (1.2 equiv), TBAB
(0.5 equiv), base (1.5 equiv), and water (2 mL), room temperature, 2 h, air, in a sealed
tube.
NMR (100 MHz, CDCl3):
116.8, 113.2, 70.3.
d 157.9, 136.6, 132.3, 128.7, 128.1, 127.5,
b
Isolated yields.
4.2.6. Benzyl 4-tert-butylphenyl ether (3fa).5j 1H NMR (400 MHz,
CDCl3):
d
7.49e7.34 (m, 7H), 6.97 (d, J¼8.7 Hz, 2H), 5.09 (s, 2H), 1.35
3. Conclusion
(s, 9H); 13C NMR (100 MHz, CDCl3):
127.5, 126.3, 114.4, 70.1, 34.1, 31.6.
d 156.7, 143.7, 137.4, 128.6, 127.9,
In conclusion, the present procedure using an easily available
phase transfer catalyst TBAB provides an efficient and convenient
procedure for the benzylation of phenols. This method offers
marked improvements with regard to operational applicability,
high isolated yields of products, and greenness of procedure,
avoiding hazardous organic solvents and toxic catalysts, and thus, it
provides a facile and practical procedure for the preparation of
benzyl phenyl ethers.
4.2.7. Benzyl 2-methylphenyl ether (3ga).5j 1H NMR (400 MHz,
CDCl3):
7.57e7.40 (m, 5H), 7.29e7.24 (m, 2H), 7.00 (t, J¼7.1 Hz,
2H), 5.18 (s, 2H), 2.42 (s, 3H); 13C NMR (100 MHz, CDCl3):
157.0,
d
d
137.7, 130.9, 128.6, 127.9, 127.2, 127.2, 126.9, 120.8, 111.6, 69.9, 16.6.
4.2.8. Benzyl 2-bromophenyl ether (3ha).5d 1H NMR (400 MHz,
CDCl3):
d
7.61 (d, J¼7.8 Hz, 1H), 7.53 (d, J¼7.5 Hz, 2H),

2672
H. Wang et al. / Tetrahedron 70 (2014) 2669e2673
7.46e7.35 (m, 3H), 7.27 (t, J¼8.0 Hz, 1H), 6.97 (d, J¼8.2 Hz, 1H),
6.89 (t, J¼7.6 Hz, 1H), 5.18 (s, 2H); 13C NMR (100 MHz, CDCl3):
2H), 6.99e6.93 (m, 3H), 5.14 (s, 2H); 13C NMR (100 MHz, CDCl3):
158.1, 147.6, 144.6, 129.7, 127.6, 123.8, 121.6, 114.8, 68.6.
d
d
155.1, 136.6, 133.5, 128.7, 128.5, 128.0, 127.1, 122.2, 114.0,
112.6, 70.8.
4.2.21. 4-(Phenoxymethyl)benzonitrile (3af).12 1H NMR (400 MHz,
CDCl3):
7.64 (d, J¼8.2 Hz, 2H), 7.52 (d, J¼8.4 Hz, 2H), 7.30e7.26 (m,
2H), 6.99e6.92 (m, 3H), 5.10 (s, 2H); 13C NMR (100 MHz, CDCl3):
158.2, 142.6, 132.4, 129.7, 127.6, 121.5, 118.7, 114.8, 111.7, 68.8.
d
4.2.9. Benzyl 2-methoxyphenyl ether (3ia).9 1H NMR (400 MHz,
CDCl3):
d
7.49 (d, J¼7.4 Hz, 2H), 7.40 (t, J¼7.3 Hz, 2H), 7.33 (t,
d
J¼7.1 Hz, 1H), 6.99e6.87 (m, 4H), 5.19 (s, 2H), 3.92 (s, 3H); 13C NMR
(100 MHz, CDCl3):
d
149.8, 148.3, 137.4, 128.6, 127.9, 127.4, 121.6,
4.2.22. 2-Fluorobenzyl phenyl ether (3ag). Yellow liquid; 1H NMR
(400 MHz, CDCl3): 7.57e7.53 (m, 1H), 7.35e7.30 (m, 3H), 7.18 (t,
J¼7.4 Hz, 1H), 7.11 (t, J¼8.8 Hz, 1H), 7.04e6.99 (m, 3H), 5.16 (s, 2H);
13C NMR (100 MHz, CDCl3):
161.8, 159.3, 158.7, 129.8, 129.8, 129.7,
120.9, 114.4, 112.1, 71.1, 56.0.
d
4.2.10. Benzyl 2,4-dimethyphenyl ether (3ja).10 1H NMR (400 MHz,
d
CDCl3):
d
7.59e7.43 (m, 5H), 7.13 (s, 1H), 7.08 (d, J¼8.2 Hz, 1H), 6.91
129.6, 124.4, 124.4, 124.3, 121.2, 115.5, 115.3, 114.9, 63.7, 63.6. HRMS-
ESI (positive ESI): m/z calcd for C13H12FO (MþH)þ: 203.0867, found:
203.0872. IR (KBr pellet, cmꢁ1): 3064, 3041, 2926, 2882, 2854, 1620,
1599, 1588, 1500, 1496, 1456, 1383, 1305, 1240, 1172, 1154, 1111,
1078, 1032, 1014, 993, 943, 883, 836, 753.
(d, J¼8.2 Hz, 1H), 5.17 (s, 2H), 2.43 (s, 3H), 2.42 (s, 3H); 13C NMR
(100 MHz, CDCl3):
127.1, 127.0, 111.7, 70.2, 20.6, 16.5.
d 155.0, 137.9, 131.8, 129.9, 128.6, 127.8, 127.3,
4.2.11. 4-(Benzyloxy)benzonitrile (3ka).5d 1H NMR (400 MHz,
CDCl3):
d
7.58 (d, J¼8.7 Hz, 2H), 7.42e7.35 (m, 5H), 7.02 (d, J¼8.8 Hz,
4.2.23. 2-Nitrobenzyl phenyl ether (3ah).13 1H NMR (400 MHz,
2H), 5.12 (s, 2H); 13C NMR (100 MHz, CDCl3):
128.8, 128.4, 127.5, 119.2, 115.6, 104.3, 70.3.
d
162.0, 135.7, 134.0,
CDCl3):
J¼7.5 Hz, 1H), 7.47 (t, J¼7.7 Hz, 1H), 7.32 (t, J¼8.0 Hz, 2H), 7.02e6.99
(m, 3H), 5.48 (s, 2H); 13C NMR (100 MHz, CDCl3):
158.2, 147.0,
d
8.15 (d, J¼8.2 Hz, 1H), 7.91 (d, J¼7.8 Hz, 1H), 7.67 (t,
d
4.2.12. 4-(Benzyloxy)benzaldehyde (3la).11 1H NMR (400 MHz,
134.0, 133.8, 129.7, 128.6, 128.3, 125.0, 121.6, 115.0, 66.8.
CDCl3):
d
9.89 (s, 1H), 7.84 (d, J¼8.6 Hz, 2H), 7.45e7.36 (m, 5H), 7.08
(d, J¼8.6 Hz, 2H), 5.15 (s, 2H); 13C NMR (100 MHz, CDCl3):
d
190.8,
4.2.24. 3-Chlorobenzyl phenyl ether (3ai).14 1H NMR (400 MHz,
163.8, 136.0, 132.0, 130.2, 128.8, 128.4, 127.5, 115.2, 70.3.
CDCl3):
2H); 13C NMR (100 MHz, CDCl3):
128.1, 127.5, 125.4, 121.3, 115.0, 69.1.
d
7.49 (s, 1H), 7.37e7.33 (m, 5H), 7.05e7.00 (m, 3H), 5.06 (s,
d
158.6, 139.3, 134.6, 130.0, 129.7,
4.2.13. 1,2-Di(benzyloxy)benzene (3ma).5a 1H NMR (400 MHz,
CDCl3):
d
7.50 (d, J¼7.4 Hz, 4H), 7.42e7.32 (m, 6H), 7.01e6.92 (m,
4H), 5.20 (s, 4H); 13C NMR (100 MHz, CDCl3):
127.8, 127.4, 121.7, 115.4, 71.4.
d
149.2, 137.5, 128.5,
4.2.25. 3-Methoxybenzyl phenyl ether (3aj).15 1H NMR (400 MHz,
CDCl3):
7.35 (t, J¼7.8 Hz, 3H), 7.08e7.01 (m, 5H), 6.94e6.91 (m,
1H), 5.09 (s, 2H), 3.85 (s, 3H); 13C NMR (100 MHz, CDCl3):
160.0,
d
d
4.2.14. Benzyl
a
-naphthyl ether (3na).11 1H NMR (400 MHz, CDCl3):
158.9, 138.8, 129.7, 129.6, 121.1, 119.8, 115.0, 113.6, 113.0, 69.9, 55.3.
d
8.45 (d, J¼7.4 Hz, 1H), 7.90e7.87 (m, 1H), 7.61e7.41 (m, 9H), 6.94
(d, J¼7.6 Hz, 1H), 5.30 (s, 2H); 13C NMR (100 MHz, CDCl3):
d
154.6,
4.2.26. 3-Nitrobenzyl phenyl ether (3ak).16 1H NMR (400 MHz,
137.3, 134.7, 128.7, 128.0, 127.6, 127.5, 126.6, 126.0, 125.9, 125.4,
122.3, 120.6, 105.3, 70.2.
CDCl3):
J¼7.8 Hz, 1H), 7.55 (t, J¼8.0 Hz, 1H), 7.34e7.30 (m, 2H), 7.02e6.98
(m, 3H), 5.14 (s, 2H); 13C NMR (100 MHz, CDCl3):
158.1, 148.3,
139.3, 133.1, 129.6, 129.5, 122.8, 122.0, 121.4, 114.8, 68.4.
d
8.31 (s, 1H), 8.16 (dd, J¼8.3 Hz, J¼1.3 Hz, 1H), 7.77 (d,
d
4.2.15. Benzyl
7.81e7.74 (m, 3H), 7.53e7.26 (m, 9H), 5.20 (s, 2H); 13C NMR
(100 MHz, CDCl3): 156.8, 137.0, 134.6, 129.5, 129.1, 128.7, 128.1,
b
-naphthyl ether (3oa).11 1H NMR (400 MHz, CDCl3):
d
d
4.2.27. a
-Naphthylmethyl phenyl ether (3al).17 1H NMR (400 MHz,
127.7, 127.6, 126.8, 126.4, 123.8, 119.1, 107.2, 70.1.
CDCl3):
d
8.11 (d, J¼7.6 Hz, 1H), 7.96e7.89 (m, 2H), 7.66e7.49 (m,
4H), 7.38 (t, J¼7.8 Hz, 2H), 7.13e7.04 (m, 3H), 5.53 (s, 2H); 13C NMR
4.2.16. 4-(Phenylmethoxy)quinoline (3pa).5f 1H NMR (400 MHz,
(100 MHz, CDCl3): d 159.0, 133.9, 132.5, 131.7, 129.7, 129.1, 128.8,
CDCl3):
J¼7.3 Hz,1H), 7.31e7.26 (m, 5H), 7.10 (d, J¼7.1 Hz, 2H), 7.29e7.27 (m,
1H), 5.28 (s, 2H); 13C NMR (100 MHz, CDCl3):
178.3, 143.7, 140.1,
d
8.42 (d, J¼8.0 Hz, 1H), 7.60 (d, J¼7.8 Hz, 1H), 7.48 (t,
126.7, 126.6, 126.0, 125.4, 123.8, 121.2, 115.0, 68.7.
d
Acknowledgements
135.2, 132.2, 129.2, 128.3, 127.4, 126.9, 126.1, 123.7, 116.2, 110.3, 56.4.
We are grateful to the National Natural Science Foundation of
China (21205107, 21172202, 21172200) and Postdoctoral Scholar-
ship of China (2012M511592) for financial support of this research.
4.2.17. 4-Methylbenzyl phenyl ether (3ab).3d 1H NMR (400 MHz,
CDCl3):
d
7.36e7.29 (m, 4H), 7.22 (d, J¼7.8 Hz, 2H), 7.01e6.96 (m,
3H), 5.04 (s, 2H), 2.38 (s, 3H); 13C NMR (100 MHz, CDCl3):
137.8, 134.1, 129.5, 129.3, 127.7, 120.9, 114.9, 69.9, 21.3.
d 158.9,
Supplementary data
4.2.18. 4-Chlorobenzyl phenyl ether (3ac).4b 1H NMR (400 MHz,
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.01.004.
CDCl3):
d
7.39e7.29 (m, 6H), 6.98 (t, J¼8.4 Hz, 3H), 5.04 (s, 2H); 13
C
NMR (100 MHz, CDCl3):
114.9, 69.2.
d 158.6, 135.7, 133.8, 129.6, 128.8, 121.2,
References and notes
4.2.19. 4-Bromobenzyl phenyl ether (3ad).3d 1H NMR (400 MHz,
1. McKillop, A.; Fiaud, J. C.; Hug, R. P. Tetrahedron 1974, 30, 1379.
2. (a) Banerjee, S. K.; Gupta, B. D.; Singh, K. J. Chem. Soc., Chem. Commun. 1982,
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