Selective water-based oxychlorination of phenol with hydrogen peroxide catalyzed by manganous sulfate

Article abstract of DOI:10.1039/c7ra00319f

An efficient method for the selective oxychlorination of phenol to 2,4-dichlorophenol catalyzed by manganous(ii) sulfate is developed using hydrogen chloride as a chlorinating source, hydrogen peroxide as an oxidant and water as a solvent. The catalyst has high activity and selectivity under mild conditions. The products are automatically isolated from aqueous solution, which also contains the catalyst at the end of the reaction, and hence product separation and catalyst recycling are both simple in this system. The performance of manganous(ii) sulfate with the oxidative chlorinating system HCl/H₂O₂ indicates that this is a promising synthetic method for the manufacture of various 2,4-dichlorophenol derivatives.

Full text of DOI:10.1039/c7ra00319f

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Selective water-based oxychlorination of phenol
with hydrogen peroxide catalyzed by manganous
sulfate†
Cite this: RSC Adv., 2017, 7, 13467
a
b
b
a
*
*
Hongchuan Xin, Shilei Yang, Baigang An and Zengjian An
An efficient method for the selective oxychlorination of phenol to 2,4-dichlorophenol catalyzed by
manganous(II) sulfate is developed using hydrogen chloride as a chlorinating source, hydrogen peroxide
as an oxidant and water as a solvent. The catalyst has high activity and selectivity under mild conditions.
The products are automatically isolated from aqueous solution, which also contains the catalyst at the
end of the reaction, and hence product separation and catalyst recycling are both simple in this system.
The performance of manganous(II) sulfate with the oxidative chlorinating system HCl/H2O2 indicates that
this is a promising synthetic method for the manufacture of various 2,4-dichlorophenol derivatives.
Received 9th January 2017
Accepted 16th February 2017
DOI: 10.1039/c7ra00319f
rsc.li/rsc-advances
Chlorination of phenols is a key synthetic method because
An alternative solution is oxidative chlorination, i.e. oxy-
chloro-substituted phenols are essential materials in the chlorination, which uses chloride anions as a chlorine source in
synthesis of herbicides, pharmaceuticals, insecticides, dyes, the presence of an oxidant (Scheme 2).7–12 In these systems,
etc.1,2 Among the various chloro-substituted phenols, main chloride anions are oxidized to chlorine by the oxidant and
products include p-chlorophenol, o-chlorophenol, 2,4-dichlor- subsequently incorporated into the products. In general, chlo-
ophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol, which rinating agents, such as sulfuryl chloride,4,13 N-chlor-
belong to a group named “light chlorophenols”.3 In this group, osuccinimide,11,12 copper chloride,14–16 titanium tetrachloride17
2,4-dichlorophenol is the most important material since it is an and p-toluene sulfonyl chloride,18 are used as chlorine sources,
intermediate for 2,4-dichlorophenoxyacetic acid, a herbicide and reagents like sulfuric acid,19 perchloric acid,12,20 lithium
that is widely used in crops, rice and other massive cultivations. diisopropylamide,18 dimethylsulfoxide,21 etc.22 are employed as
Traditional methods for the synthesis of 2,4-dichlorophenol oxidants. While the utilization of chlorine atoms in oxy-
usually involve electrophilic aromatic chlorination of phenol chlorination is remarkably increased compared to only half in
with chlorine gas (Scheme 1).3–5 However, the utilization of traditional methods, further research is still required to use
chlorine atoms in these processes is quite low, nearly half of the cheaper and environmentally friendly reagents.
chlorine is released as waste gas, which results in a waste of
material and environment hazards.6,7
Compared with most studies focused on the synthesis of
monochloro-substituted phenols,4,23–28 the oxychlorination of
phenols to 2,4-dichlorophenols is rather limited so far.3,20,29 For
example, Gusevskaya et al. reported a method for aerobic oxy-
chlorination of phenols over a CuCl2 catalyst, in which metal
chlorides were used as chlorinating agents.30,31 Feng et al. found
a microwave method for aerobic oxychlorination of phenols
catalyzed by CuCl2 with hydrochloric acid as a chlorine source.23
However, these methods are exploited for the synthesis of p-
chlorophenols. Notably, Ratnasamy et al. developed a prom-
ising method for the oxychlorination/oxybromination of
aromatics including phenols over copper phthalocyanines
Scheme
1 Traditional methods for the synthesis of 2,4-
dichlorophenol.
aKey Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess
Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101,
China. E-mail: anzj@qibebt.ac.cn
bSchool of Chemical Engineering, University of Science and Technology Liaoning,
Anshan 114051, China. E-mail: bgan@ustl.edu.cn
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra00319f
Scheme 2 Oxychlorination for the synthesis of 2,4-dichlorophenol.
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On the other hand, the use of water as a solvent is particularly
attractive because: (1) water is cheaper than VOC solvents; (2)
the risk of explosions using a water-based system is much lower
than that for systems containing VOCs; (3) 2,4-dichlorophenol
is almost insoluble in water, and hence the product can be
obtained by simple phase separation, which is convenient in
application. However, this is a challenging topic, especially
since catalytic methods for 2,4-dichlorophenol with high
activity and selectivity have not been reported previously.
Herein, we present an efficient manganous(II) sulfate-
catalyzed oxychlorination of phenol in water using the oxida-
tive chlorinating system HCl/H2O2 (Scheme 4). Complete
conversion of phenol and high selectivity for 2,4-dichlor-
ophenol are both achieved under mild conditions. To the best
of our knowledge, this is the rst report on selective water-based
oxychlorination of phenol into 2,4-dichlorophenol in the liquid
phase under VOC-free conditions.
Scheme 3 Oxychlorination for the synthesis of 2,4-dichlorophenol
with environmentally friendly oxidants.
Scheme 4 Oxychlorination for the synthesis of 2,4-dichlorophenol
with H2O2 in water.
Table 1 Results for the oxychlorination of 1a over various catalysts
In a typical reaction, phenol (1a) and a catalyst were added
into water in a glass ask, and gaseous HCl was introduced to
form a homogeneous solution. Then, 30% of an aqueous solu-
tion of H2O2 was added to start the reaction. In the initial study,
the molar ratio of HCl : H2O2 : 1a at 7.1 : 1.9 : 1 was used to
screen the catalysts, and the results are shown in Table 1. In the
absence of H2O2, no reaction occurred even with a prolonged
time (Table 1, run 1). When H2O2 was added in the absence of
a catalyst, conversion of 1a reached 69% with a total yield of
67%, the products were composed of <1% of 2,4-dichlorophenol
(1b), 45% of p-chlorophenol (p-) and 21% of o-chlorophenol (o-)
(Table 1, run 2). In the presence of H2O2, metal salts showed
different activities. Among the tested metal salts, NaCl, CaCl2,
MgCl2, ZnCl2, FeSO4, FeCl3, NiSO4, Co(OAc)2, Co(acac)2, LiCl,
Cu(NO3)2, Cu(OAc)2 and CuBr2 had a poor effect (Table 1, run 3–
15), as both the conversions and total yields were lower than
those using H2O2 alone. Notably, CuCl2 and MnSO4 indicated
high activities; the product distribution showed a dependence
on the catalysts. A conversion of 85% for 1a was obtained over
CuCl2, the total yield was 83%, containing <1% of 1b, 54% of p-
and 29% of o- (Table 1, run 16). Conversion of 1a over MnSO4
reached as high as 93% with a total yield of 91%, and the
products were 16% of 1b, 49% of p-, 26% of o- and trace 2,6-
dichlorophenol (1c) (Table 1, run 17). Obviously, MnSO4 is more
effective in the formation of 1b. Meanwhile, various manganese
compounds were used, and the effect of anions on the reactions
was tested (Table 1, run 18–20). Conversions and yields over
MnCl2 and Mn(NO3)2 were comparable with those of MnSO4.
Because the solubility of MnO2 in the solution was not good and
some solid precipitate was always observed during the reaction,
its activity was poor. These results indicated that anions had no
effect on the reactions, and Mn2+ was key in this system.
Reactions over MnSO4 were optimized, and the results are
listed in Table 2. The effect of the catalyst was examined at
a ratio of HCl : H2O2 : 1a ¼ 7.1 : 1.9 : 1 (Table 2, run 1–3). As
MnSO4 was varied from 1 mol% to 10 mol%, 1a was completely
converted at room temperature, the total yield decreased from
91% to 80%, the yield of 1b increased from 16% to 57%, but the
yield for p-decreased from 49% to 15% and o- was from 26% to
8%. In these processes, trace 1c was found. Obviously, over 5
calculated from GC dataa
Yieldd (%)
Run Catalyst
Conversionb (%) Total yieldc (%) 1b p- o- 1c
1e
2
—
—
<1
69
38
45
40
36
54
61
56
—
67
34
41
38
33
51
55
40
20
27
28
16
23
51
83
91
89
90
65
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
<1 45 21
<1 22 12
<1 26 14
<1 22 16
<1 19 14
<1 41 10
<1 33 22
<1 25 15
3
4
5
6
7
8
9
NaCl
CaCl2
MgCl2
ZnCl2
FeSO4
FeCl3
NiSO4
10
11
12
13
14
15
16
17
18
19
20
Co(OAc)2 21
Co(acac)2 28
LiCl
Cu(NO3)2 18
Cu(OAc)2 27
CuBr2
CuCl2
MnSO4
MnCl2
<1 15
<1 19
5
8
48
<1 18 10
<1 12
<1 16
4
7
56
85
93
91
<1 34 17
<1 54 29
16 49 26 Trace
14 47 28 Trace
19 45 26 Trace
Mn(NO3)2 94
MnO2 67
8
38 19
—
a
Reaction conditions: 1a: 21.3 mmol, catalyst:
1 mol%, HCl:
151.3 mmol, H2O2 (30% aq. solution): 4.05 ml, 39.7 mmol, H2O:
b
9.8 ml, rt., 3 h. Conversion (%) ¼ [the converted 1a (mol)/initial 1a
c
(mol)] ꢀ 100. Total yield (%) ¼ [all products (mol)/initial 1a (mol)] ꢀ
d
e
100. Yield (%) ¼ [target product (mol)/initial 1a (mol)] ꢀ 100. No
H2O2 was added.
encapsulated in zeolites with HCl and alkali chlorides/bromides
as halogen sources and dioxygen and hydrogen peroxide as
oxidants,32 but the selectivity for 2,4-dichloroaromatics was low.
Moreover, VOCs (volatile organic compounds) are usually
present in these systems (Scheme 3).
As for oxychlorination, we consider a desirable route for the
chlorination of phenols with HCl using environmentally
friendly oxidants, such as dioxygen or hydrogen peroxide,23,32,33
in which chlorine anions are incorporated into the product via
oxidation and water is the only by-product from the oxidants.
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Table 2 Results for the optimization of reaction conditions calculated from GC dataa
Yieldd (%)
T
(ꢁC)
HCl : H2O2 : 1a
(molar ratio)
Run
MnSO4 (mol%)
Conversionb (%)
Total yieldc (%)
1b
p-
o-
1c
1
2
3
1
5
10
1
1
1
1
1
1
25
25
25
25
45
60
80
90
80
80
80
80
80
80
80
80
7.1 : 1.9 : 1
7.1 : 1.9 : 1
7.1 : 1.9 : 1
2.4 : 1.9 : 1
2.4 : 1.9 : 1
2.4 : 1.9 : 1
2.4 : 1.9 : 1
2.4 : 1.9 : 1
2.4 : 2.8 : 1
2.1 : 2.8 : 1
2.1 : 2.8 : 1
2.0 : 2.0 : 1
2.0 : 2.0 : 1
2.1 : 2.8 : 1
2 : 2.8 : 1
93
91
82
80
74
86
92
95
83
97
95
96
91
83
93
92
88
16
55
57
9
49
16
15
39
38
31
13
11
1
26
9
8
25
22
18
9
Trace
Trace
Trace
Trace
100
100
76
89
94
100
100
100
100
100
94
85
100
96
4
5e
25
41
72
65
93
91
34
31
58
89
85
73
1
6e
Trace
3
2
3
7e
8e
5
9f
Trace
Trace
23
25
10
Trace
2
10g
11g
12h
13h
14g,i
15j
16k
1
1
3
—
—
1
1
1
39
35
15
2
3
4
Trace
Trace
1
2
2
9
1
2.1 : 3.7 : 1
100
2
a
b
Reaction conditions: 1a: 21.3 mmol, HCl: 151.3 mmol, H2O2 (30% aq. solution): 4.05 ml, 39.7 mmol, H2O: 9.8 ml, 3 h. Conversion (%) ¼ [the
converted 1a (mol)/initial 1a (mol)] ꢀ 100. c Total yield (%) ¼ [all products (mol)/initial 1a (mol)] ꢀ 100. d Yield (%) ¼ [target product (mol)/initial 1a
(mol)] ꢀ 100. e HCl: 50.4 mmol. f HCl: 50.4 mmol, H2O2 (30% aq. solution): 6.08 ml, 58.8 mmol. g HCl: 44.7 mmol, H2O2 (30% aq. solution): 6.08 ml,
h
i
j
58.8 mmol. HCl: 42.6 mmol, H2O2 (30% aq. solution): 4.35 ml, 42.6 mmol. Under Ar atmosphere. HCl: 42.6 mmol, H2O2 (30% aq. solution):
6.08 ml, 58.8 mmol. k HCl: 44.7 mmol, H2O2 (30% aq. solution): 8.10 ml, 79.4 mmol.
Table 3 Recycle test results of the catalysta
of o- and 3% of 1c. Further increasing the temperature to 90 ꢁC
resulted iꢁn over-oxidation and the total yield decreased to 83%.
Thus, 80 C is desirable for the reactions.
Yieldd (%)
Run time Conversionb (%) Total yieldc (%) 1b p- o-
When we increased the amount of H2O2, i.e. the ratio of
HCl : H2O2 : 1a was varied from 2.4 : 1.9 : 1 to 2.4 : 2.8 : 1, the
yield of 1b reached as high as 93% with 1% of p-, trace o- and 3%
of 1c (Table 2, run 9). If HCl was further decreased and
HCl : H2O2 : 1a was tuned to 2.1 : 2.8 : 1, the total yield was
95%, and the yield for 1b was 91% with 1% of p-, trace o- and 3%
of 1c (Table 2, run 10). In the absence of MnSO4, the full
conversion of 1a with a total yield of 96% was achieved, and the
yield for 1b was 34% with 39% of p-, 23% of o- and trace 1c
(Table 2, run 11). When the reaction was carried out based on
the theoretical equation (Scheme 4), i.e. HCl : H2O2 : 1a was
2.0 : 2.0 : 1, 85% of 1a was converted with a total yield of 83%,
and the products were 58% of 1b, 15% of p-, 10% of o- and 1% of
1c (Table 2, run 13). In the absence of MnSO4, 94% of 1a was
converted with a total yield of 91%, containing 31% of 1b, 35%
of p-, 25% of o- and trace 1c (Table 2, run 12). Obviously, the
presence of MnSO4 signicantly increased the yield of 1b, and
hence MnSO4 is key for the selective chlorination of 1a to 1b.
When the reaction was performed under an Ar atmosphere
(Table 2, run 14), the results were comparable with those in air
(Table 2, run 10), so oxygen has no effect on the reactions. If 1a
was chlorinated based on a ratio of HCl : 1a at 2.0 : 1, the yield
of 1b was 85% with 3% of p-, 2% of o- and 2% of 1c (Table 2, run
15). As a large excess amount of H2O2 was used (HCl : H2O2-
: 1a ¼ 2.1 : 3.7 : 1), over-oxidation occurred and the total yield
decreased to 88% (Table 2, run 16). Because the decomposition
of H2O2 is inevitable, the used amount of H2O2 in the reaction is
higher than the theoretical value. The utilization of H2O2 and
1c
1
3
6
100
100
98
95
94
92
91
90
88
1
1
2
Trace
Trace
Trace
3
2
1
a
Reaction conditions: 1a: 21.3 mmol, MnSO4: 1 mol%, HCl: 44.7 mmol,
H2O2 (30% aq. solution): 6.08 ml, 58.8 mmol, H2O: 9.8 ml, 80 ꢁC, 3 h.
b
Conversion (%) ¼ [the converted 1a (mol)/initial 1a (mol)] ꢀ 100.
c
d
Total yield (%) ¼ [all products (mol)/initial 1a (mol)] ꢀ 100. Yield
(%) ¼ [target product (mol)/initial 1a (mol)] ꢀ 100.
Scheme
5 Oxychlorination for the synthesis of 2,4-dichloro-
substituted phenol derivatives with H2O2 under VOC-free conditions.
mol% of MnSO4 resulted in lower total yields due to over-
oxidation. When the amount of HCl was reduced and
HCl : H2O2 : 1a was varied to 2.4 : 1.9 : 1, the conversion of 1a
was 76% with a total yield of 74%, containing 9% of 1b, 39% of
p-, 25% of o- and trace 1c (Table 2, run 4). A large excess amount
of HCl promotes the formation of 1b. The effect of temperature
was tested at a HCl : H2O2 : 1a ratio of 2.4 : 1.9 : 1 (Table 2, run
5–8). As the temperature was increased from 45 ꢁC to 90 ꢁC, 1a
was completely converted at 80 ꢁC and the total yield was 95%;
the yield for 1b reached a maximum of 72% with 13% of p-, 9%
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was further used in the chlorination of various phenol deriva-
tives (see ESI, Table 1S†). Although monochloro-substituted
phenols, such as p- and o-, are undesirable products in our
reactions, these compounds can be efficiently converted into 1b
in our method. Complete conversion of p- was obtained in
a high yield of 96% for 1b, and the yield of 1b was 94% for the
total conversion of o-. Thus, monochloro-substituted phenols
can be effectively utilized, and the by-product that remains in
our system is only 1c. As for bromo- or iodo-substituted
phenols, side-reactions of debromination/deiodination
occurred and resulted in a complex mixture. This method is
effective for alkylphenols, which were successfully chlorinated
as various 2,4-dichlorophenols. A yield of 75% was achieved for
3b from o-cresol (3a), and an 81% yield for 4b was obtained
from 2-tert-butylphenol (4a). Complete conversion of 5a (3,5-
dimethylphenol) was achieved, and the yield for 5b was 86%.
The chlorination of ethers of phenol can also be easily per-
formed under similar conditions. Complete conversion of ani-
sole (6a) led to a yield of 82% for 6b, and a high yield of 81% for
7b was achieved from 3,5-dimethylanisole (7a). Thus, we
consider that our study offers a versatile synthetic method in
the manufacture of various 2,4-dichlorophenol derivatives
(Scheme 5).
Scheme 6 A reaction pathway of the oxychlorination of phenol over
an Mn2+ catalyst.
HCl based on the optimized conditions (Table 2, run 10) is 66%
and 87%, respectively.
When HCl : H2O2 : 1a was 3.1 : 4.2 : 1, full conversion of 1a
ꢁ
was achieved at 80 C for 3 h and the total yield was 91%, the
yield for 2,4,6-trichlorophenol was 73% with 11% of 1b, 7% of
1c and trace p- and o-. If HCl : H2O2 : 1a was increased to
3.5 : 4.2 : 1, full conversion of 1a with a total yield of 94% was
obtained, and 80% of 2,4,6-trichlorophenol with 6% of 1b and
8% of 1c were found as the products. Thus, while the perfor-
mance of MnSO4 is better in the synthesis of 1b, it is also active
in the synthesis of 2,4,6-trichlorophenol.
The molar ratio of H2O2 : 1a was 2 : 1 according to the
theoretical equation (Scheme 4), but it was 2.8 : 1 under the
optimized conditions (Table 2, run 10). The used amount of
H2O2 is higher than the theoretical value. It is well known that
the catalytic decomposition of H2O2 over metal ions is inevi-
table, and the interactions of Mn2+ with H2O2 lead to numerous
reactive species, such as oxygen atoms, active oxygen species or
OHc/OOHc radicals, which are possible active species for reac-
tions. In our experiments, when a free radical scavenger, 2,6-di-
tert-butyl-4-methyl phenol, was added into the reactions, the
yield of 1b signicantly decreased to 30%. Although this result
indicates that a free radical pathway is possibly involved in the
reactions, our attempts to nd out the free radicals or active
species failed because of the complexity of this system. In
controlled experiments, we found that the addition of H2O2 into
an aqueous solution of HCl immediately resulted in light yellow
gas, which was Cl2 based on GC-MS analysis. Thus, while the
exact free radicals or active species are not yet clear, the main
pathway can be presented as shown in Scheme 6: HCl is
oxidized by H2O2 to Cl2; the generated Cl2 reacts with 1a to form
1b with the release of HCl, which is re-oxidized and re-used
until 1a is exhausted. Details of the reaction mechanism are
under investigation, and we will report the results in future.
In our experiments, we found that the reagents formed
a homogeneous solution before reaction, and two discrete
phases were observed at the end of the reaction. The top phase
is an aqueous solution containing the catalyst, and the lower is
an organic phase mainly composed of 1b, p-, o- and 1c. This
means that the products automatically come out from the
aqueous solution. This property is really convenient for product
collection via phase separation. Moreover, since MnSO4
remains in the aqueous solution, recycling of the catalyst is
simple.
In fact, commercial hydrochloric acid can be directly used
rather than gaseous HCl in the reactions, as similar results were
also obtained under the optimized conditions. However, we
think that the use of gaseous HCl is more economical, partic-
ularly for large scale production. If hydrochloric acid is used,
the products can be obtained by phase separation, but the
collection of the catalyst requires the removal the whole
aqueous solution via evaporation. Then, the collected catalyst,
1a and hydrochloric acid are mixed for the next run. As gaseous
HCl is used, the products were isolated by phase separation, the
remaining aqueous solution was concentrated by removing
excess water from the solution of H2O2 under reduced pressure,
and gaseous HCl was introduced into the concentrated solu-
tion. Then, 1a is added for the next run. Compared with gaseous
HCl, it is clear that more water needs to be evaporated when
using hydrochloric acid.
Conclusions
Based on the optimized conditions, the recycle test results of
the catalyst are shown in Table 3. Aer each run, the same
procedure was performed until the catalyst was used 6 times.
These results indicate that the catalyst was recyclable, and no
signicant decrease in activity was observed even aer 6 runs.
Since 2,4-dichloro-substituted phenol derivatives present
a series of valuable materials for ne chemicals, this method
In summary, we have developed a simple, mild and efficient
method for oxychlorination of phenol to 2,4-dichlorophenol
catalyzed by manganous(II) sulfate in the liquid phase. In this
system, hydrogen chloride was used as a chlorinating agent,
hydrogen peroxide as an oxidant and water as a solvent. We
envisage that our method will be effective in the manufacture of
various 2,4-dichlorophenol derivatives based on the following
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reasons: (1) high activity and selectivity; (2) VOC free; (3) simple 1H), 3.86 (s, 3H); 13C NMR (150 MHz, CDCl3) d: 153.9, 129.9,
product separation and recyclable catalyst.
127.9, 125.6, 123.2, 112.8, 56.3.
2,4-Dichloro-3,5-dimethylanisole. 1H NMR (600 MHz, CDCl3)
d: 6.67 (s, 1H), 3.86 (s, 3H), 2.47 (s, 3H), 2.36 (s, 3H); 13C NMR
(150 MHz, CDCl3) d: 153.2, 136.3, 134.9, 126.8, 120.9, 111.4,
59.3, 21.2, 18.2.
Experimental section
Typical procedure for oxychlorination of phenol
Phenol and a catalyst were added to water in a three-neck ask
equipped with a gas inlet, a liquid inlet and a reux condenser
(open to air). Gaseous HCl was introduced and dissolved as an
aqueous solution. The ask was immersed in a preheated oil
bath and vigorously stirred with a magnetic stirrer. Then, H2O2
(30% aq. solution) was added dropwise by a channel pump
during the reaction. At the end of the reaction, the mixtures
were le to stand for 1.5 h, and an isolated organic phase from
the aqueous solution formed at the bottom. The organic phase
was collected and diluted with acetonitrile to prepare the
sample for quantitative analysis. The conversions and yields
were determined by gas chromatography. Each experiment was
reproduced at least three times. The experimental error in the
determination of the conversions and yields normally did not
exceed 4%. Pure products were obtained by column chroma-
tography using silica gel (petroleum ether) and conrmed by
Acknowledgements
We are thankful for the funding support from the Innovative
Research Team in College and Universities of Liaoning Province
(No. LT2014007).
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GC-MS, H and 13C NMR.
1H NMR and 13C NMR analytical data of products
2,4-Dichlorophenol. 1H NMR (600 MHz, CDCl3) d: 7.32 (d, J ¼
2.4 Hz, 1H), 7.15 (dd, J ¼ 2.4, 9.6 Hz, 1H), 6.95 (d, J ¼ 9.0 Hz,
1H), 5.51 (s, 1H); 13C NMR (150 MHz, CDCl3) d: 150.2, 128.6,
128.56, 125.6, 120.4, 117.1.
1
4-Chlorophenol. H NMR (600 MHz, CDCl3) d: 7.19 (d, J ¼ 10 L. Yang, L. Zhan and S. S. Stahl, Chem. Commun., 2009, 6460–
9.0 Hz, 2H), 6.76 (d, J ¼ 8.4 Hz, 2H), 4.90 (s, 1H); 13C NMR (150
MHz, CDCl3) d: 154.1, 129.6, 125.7, 116.7.
6462.
11 X. Sun, G. Shan, Y. Sun and Y. Rao, Angew. Chem., Int. Ed.,
2013, 52(16), 4440–4444.
1
2-Chlorophenol. H NMR (600 MHz, CDCl3) d: 7.29 (m, 1H),
7.16 (m, 1H), 7.01 (m, 1H), 6.85 (m, 1H), 5.62 (s, 1H); 13C NMR 12 Y. Goldberg and H. Alper, J. Org. Chem., 1993, 58(11), 3072–
(150 MHz, CDCl3) d: 151.4, 129.1, 128.5, 121.4, 119.9, 116.3.
3075.
2,6-Dichlorophenol. 1H NMR (600 MHz, CDCl3) d: 7.26 (d, J ¼ 13 L. Delaude and P. Laszlo, J. Org. Chem., 1990, 55(18), 5260–
7.8 Hz, 2H), 6.82 (t, J ¼ 8.4 Hz, 1H), 5.85 (s, 1H); 13C NMR (150
MHz, CDCl3) d: 147.9, 128.3, 121.2, 121.1.
5269.
14 S. R. Bansal, D. C. Nonhebel and J. M. Mancilla, Tetrahedron,
1973, 29(7), 993–999.
1
2,4,6-Trichlorophenol. H NMR (600 MHz, CDCl3) d: 7.28 (s,
2H), 5.81 (s, 1H); 13C NMR (150 MHz, CDCl3) d: 146.9, 128.1, 15 X. Wan, Z. Ma, B. Li, K. Zhang, S. Cao, S. Zhang and Z. Shi, J.
125.4, 121.6.
2,4-Dichloro-6-methylphenol. H-NMR (600 MHz, CDCl3) d: 16 D. Niu, T. Wang, B. P. Woods and T. R. Hoye, Org. Lett., 2014,
7.16 (d, J ¼ 2.4 Hz, 1H), 7.02 (d, J ¼ 2.4 Hz, 1H), 5.24 (s, 1H), 2.26
16(1), 254–257.
(s, 3H); 13C NMR (150 MHz, CDCl3) d: 148.4, 129.6, 127.3, 125.8, 17 J. S. Grossert and G. K. Chip, Tetrahedron Lett., 1970, 11(30),
124.7, 119.8, 16.3. 2611.
2,4-Dichloro-6-t-butylphenol. 1H-NMR (600 MHz, CDCl3) d: 18 K. M. Brummond and K. D. Gesenberg, Tetrahedron Lett.,
7.20 (d, J ¼ 2.4 Hz, 1H), 7.15 (d, J ¼ 2.4 Hz, 1H), 5.80 (s, 1H), 1.38 1999, 40(12), 2231–2234.
(s, 9H); 13C NMR (150 MHz, CDCl3) d: 148.5, 138.9, 126.2, 125.9, 19 J. R. L. Smith, L. C. Mckeer and J. M. Taylor, J. Chem. Soc.,
124.7, 121.1, 35.5, 29.1. Perkin Trans. 2, 1988, 10, 1533–1537.
2,4-Dichloro-3,5-dimethylphenol. 1H-NMR (600 MHz, CDCl3) 20 B. S. Moon, Y. C. Han, H. Y. Koh and D. Y. Chi, Bull. Korean
d: 6.80 (s, 1H), 5.48 (s, 1H), 2.46 (s, 3H), 2.32 (s, 3H); 13C NMR
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(150 MHz, CDCl3) d: 149.5, 136.0, 134.2, 126.5, 118.5, 115.1, 21 G. Majetich, R. Hicks and S. Reister, J. Org. Chem., 1997,
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1
20.8, 18.3.
62(13), 4321–4326.
2,4-Dichloroanisole. 1H NMR (600 MHz, CDCl3) d: 7.34 (d, J ¼ 22 R. Prebil, K. K. Laali and S. Stavber, Org. Lett., 2013, 15(9),
2.4 Hz, 1H), 7.19 (dd, J ¼ 2.4, 9.0 Hz, 1H), 6.82 (d, J ¼ 9.0 Hz,
2108–2111.
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