Decarboxylation of tetrafluorophthalic acid in NH3-enriched high temperature liquid water

Article abstract of DOI:10.1016/j.apcata.2016.01.034

2,3,4,5-Tetrafluorobenzoic acid is an important pharmaceutical intermediate. A green technology for the decarboxylation of tetrafluorophthalic acid to 2,3,4,5-tetrafluorobenzoic acid in NH₃-enriched high temperature liquid water (HTLW) was developed. Tetrafluorophthalic acid could undergo the decarboxylation with the catalysis of NH₃ to 2,3,4,5-tetrafluorobenzoic acid in HTLW. A conversion of 98.1% and selectivity of 96.5% were achieved at 453.15 K for 1.5 h with an ammonia concentration of 13.4 mmol/L. The effects of ammonia concentration, initial concentration of reactant and reaction temperature were then investigated and correlated using a derivated equation. The results indicated that adequate addition of ammonia could adjust the pH of the reaction medium into 2.2-2.4, where the dominant form of the decarboxylation is the monovalent anion. Moreover, the kinetic data at different temperatures were fitted by a first-order equation, and the rate constants at each temperature and an activation energy of 190 kJ/mol were obtained.

Full text of DOI:10.1016/j.apcata.2016.01.034

Applied Catalysis A: General 515 (2016) 10–15
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Decarboxylation of tetrafluorophthalic acid in NH3-enriched high
temperature liquid water
Jie Fua, Jing Moa, Jing Zhangb, Xiuyang Lua,∗
a Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou
310027, China
b Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
2,3,4,5-Tetrafluorobenzoic acid is an important pharmaceutical intermediate. A green technology for
the decarboxylation of tetrafluorophthalic acid to 2,3,4,5-tetrafluorobenzoic acid in NH3-enriched high
temperature liquid water (HTLW) was developed. Tetrafluorophthalic acid could undergo the decarboxy-
lation with the catalysis of NH3 to 2,3,4,5-tetrafluorobenzoic acid in HTLW. A conversion of 98.1% and
selectivity of 96.5% were achieved at 453.15 K for 1.5 h with an ammonia concentration of 13.4 mmol/L.
The effects of ammonia concentration, initial concentration of reactant and reaction temperature were
then investigated and correlated using a derivated equation. The results indicated that adequate addi-
tion of ammonia could adjust the pH of the reaction medium into 2.2–2.4, where the dominant form of
the decarboxylation is the monovalent anion. Moreover, the kinetic data at different temperatures were
fitted by a first-order equation, and the rate constants at each temperature and an activation energy of
190 kJ/mol were obtained.
Received 21 September 2015
Received in revised form 10 January 2016
Accepted 24 January 2016
Available online 28 January 2016
Keywords:
NH3-enriched
High temperature liquid water
Decarboxylation
2,3,4,5-Tetrafluorobenzoic acid
Kinetics
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
boxylation of aromatic carboxylic acids. High temperature liquid
water (HTLW) is one of commonly environmentally benign medi-
2,3,4,5-tetrafluorobenzoic acid is an important organic fluoride,
primarily used for preparation of antibacterial agents of fluoro-
quinolone [1,2], such as lomefloxacin, sparfloxacin, levofloxacin,
rufloxacin, etc. [3–5]. The antibacterial agents have many advan-
tages including broad antimicrobial spectrum, strong and fast
antimicrobial effects and few side-effects [6,7]. In global market
of total antibacterial agents, quinolone ranked at third place fol-
lowed by cephalosporin class and penicillin drugs. Additionally, the
2,3,4,5-tetrafluorobenzoic acid can be also used in preparation of
conductive materials, organooxotin clusters and so on [8,9].
In the preparation of 2,3,4,5-tetrafluorobenzoic acid through
decarboxylation, high boiling organic amine, such as tri-n-
butylamine, was commonly used as solvent [10]. Transition metals,
such as Cu [11], Ag [12] and Pd [13], were often employed as the
catalyst for the decarboxylation of aromatic carboxylic acids. In lit-
erature, the protodecarboxylation was not affected by the copper
source, but significantly facilitated by the presence of bipyridine
ligands at the copper and the use of aromatic amines as solvent
[14,15], indicating the medium plays an important role in the decar-
ums [16], which has a low dielectric constant thereby increasing
its solubility for some organic compounds. In addition, the use of
HTLW also eliminates the consumption of organic solvents and
acid/base solution. However, problems associated with using the
HTLW include necessity for high reaction temperatures because of
low reaction rates and abundance of byproducts because of poor
selectivity [17].
Given the capability of ammonia in enhancing reaction rates and
its recyclability by post-reaction heating, herein we proposed using
a solvent system by adding the ammonia to the HTLW to accelerate
the decarboxylation rate of tetrafluorophthalic acid. The decar-
boxylation of carboxylic acids is subject to general base catalysis
[18]. The behavior of tetrafluorophthalic acid decarboxylation was
studied. The effects of ammonia concentration, initial concentra-
tion of reactant and reaction temperature were then investigated.
The kinetic data at different temperatures were fitted by a first-
order equation, and the rate constants at each temperature and
an activation energy were obtained. Eventually, the effects of
ammonia concentration, initial concentration of reactant and tem-
perature on the decarboxylation of tetrafluorophthalic acid were
described quantitatively using an equation.
∗
Corresponding author.
E-mail address: luxiuyang@zju.edu.cn (X. Lu).
http://dx.doi.org/10.1016/j.apcata.2016.01.034
0926-860X/© 2016 Elsevier B.V. All rights reserved.

J. Fu et al. / Applied Catalysis A: General 515 (2016) 10–15
11
2. Experimental
(a)
2.1. Materials
Tetrafluorophthalic acid (≥98.5%) was purchased from Shanghai
Kaisai Chemical Co. Ltd. 2,3,4,5-tetrafluorobenzoic acid (≥99.0%)
was purchased from Shanghai Kangtuo Chemical Co. Ltd. Ammonia
solution and ethanol (analytical reagent grade) were obtained from
Hangzhou Chemical Reagent Co, Ltd. All chemicals were used as
received. Deionized water was made in the laboratory.
2.2. Reactors
A batch reactor made of 316L stainless steel tubing with a
volume of about 13.5 mL was used for the decarboxylation of
tetrafluorophthalic acid. The reactor was composed of three parts:
tube, stopper, and cap. The tube had an internal diameter of 12 mm,
which was sealed by a stopper with a diameter of 13.8 mm. A cap
was used to fix the tube and stopper. The reactor was heated by a
steel box furnace which is capable of heating 12 reactors simulta-
neously. The furnace had a temperature deviation within 2 K.
(b)
2.3. Experimental procedure
A certain amount of tetrafluorophthalic acid and 8 mL of ammo-
nia solution with a certain concentration were added to the reactor.
After being sealed, the reactor was put into the furnace, which
had been preheated to the reaction temperature. We obtained the
heating curve at the temperature of 453.15 K before our experi-
ments. The heating curve showed the temperature of the liquid
phase could get stable within 20 min and the temperature inside
was 2 K lower than outside, so the temperature of furnace was set
2 K higher than the reaction temperature. After the reaction, the
reactor was removed from the furnace and quenched in water. The
sample was then collected from the quenched reactor.
2.4. Sampling and analysis
Fig. 1. Effect of ammonia concentration on the decarboxylation of tetrafluoroph-
thalic acid at 453.15 K. The concentrations of tetrafluorophthalic acid are 10, 20, 30
and 40 mmol/L, respectively.
The post-reaction solution was discharged into a 50 mL volu-
metric flask. The reactor was then washed for three times with
ethanol which was subsequently added to the flask as well. The
liquid in the flask was analyzed by HPLC (Agilent1100) with a UV
detector at 215 nm. The HPLC column was phenomenex Gemini
C18 (250 mm × 4.6 mm, 5 ␮m). The mobile phase was 0.05 mol/L
of NaH2PO4 (pH 3.5 adjusted by H3PO4): methanol at a volume
ratio of 40:60. The mobile phase was prepared as follows: NaH2PO4
was dissolved in deionized water at a concentration of 0.05 mol/L,
and then the pH value of this solution was adjusted to 3.5 using
dilute phosphoric acid and pH indicator. The solution of NaH2PO4
was mixed with methanol at a volume ratio of 40:60 as the mobile
phase. The column temperature was 308.15 K. The injection vol-
ume was 2 ␮L. Peaks were identified by matching their retention
time with those of standard solutions of pure compounds.
detected. The concentration of ammonia appeared to have a signifi-
cant effect on the decarboxylation of tetrafluorophthalic acid. With
the increase of ammonia loading, the conversion of tetrafluoroph-
thalic acid firstly increased and then significantly decreased. The
selectivities to 2,3,4,5-tetrafluorobenzoic acid were mostly higher
than 90%. It indicates that an adequate amount of ammonia can sig-
nificantly improve the rate of decarboxylation. The role of ammonia
for the decarboxylation will be discussed later.
3.2. Effect of reactant initial concentration on decarboxylation of
tetrafluorophthalic acid
Fig. 2 shows the effect of initial concentration on the decarboxy-
lation of tetrafluorophthalic acid. The reactions were performed
using 13.4 mmol/L ammonia solution, which was the optimized
ammonia concentration based on Fig. 1. Four concentrations of
tetrafluorophthalic acid (10, 20, 30 and 40 mmol/L) were used and
the reaction temperature was 443.15 K. The conversion rate of
tetrafluorophthalic acid slowed with the increase of reactant ini-
tial concentration. It suggests that the ammonia concentration of
13.4 mmol/L was not suitable for high reactant concentration and
the reaction was not sufficiently accelerated. As shown in Fig. 2b,
the selectivity to 2,3,4,5-tetrafluorobenzoic acid at different reac-
tant concentrations was maintained no less than 90%.
3. Result and discussion
3.1. Effect of concentration of ammonia on decarboxylation of
tetrafluorophthalic acid
Fig. 1 shows the effect of ammonia concentration on the decar-
boxylation of tetrafluorophthalic acid. The standard deviations in
Fig. 1 were determined from three replicate experiments. The reac-
tions were performed at tetrafluorophthalic acid concentrations
of 10, 20, 30 and 40 mmol/L under 453.15 K for 1 h. The results
showed that 2,3,4,5-tetrafluorobenzoic acid was the only product

12
J. Fu et al. / Applied Catalysis A: General 515 (2016) 10–15
(a)
(a) 100
90
100
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
423.15K cal
433.15K cal
443.15K cal
10mmol/L
453.15K ca
423.15K
433.15K
443.15K
453.15K
l
20mmol/L
30mmol/L
40mmol/L
0
2
4
6
8
10
12
0.0
0.5
1.0
1.5
2.0
2.5
3.0
time/h
time/h
(b)
(b)
100
100
90
90
80
423.15K
433.15K
443.15K
453.15K
80
10mmol/L
20mmol/L
30mmol/L
40mmol/L
70
70
60
0
2
4
6
8
10
12
60
0.0
0.5
1.0
1.5
2.0
2.5
3.0
time/h
time/h
Fig. 3. Effect of temperature on the decarboxylation of tetrafluorophthalic acid. The
reaction temperatures are 423.15, 433.15, 443.15 and 453.15 K, respectively.
Fig. 2. Effect of initial reactant concentration on the decarboxylation of tetrafluo-
rophthalic acid at 443.15 K. The concentrations of tetrafluorophthalic acid are 10,
20, 30 and 40 mmol/L, respectively.
F
F
F
-
-
COOH
COOH
F
F
COO
COO
F
F
F
F
3.3. Effect of temperature on decarboxylation of
tetrafluorophthalic acid
-H+
-H+
-
COOH
COO
Fig. 3 shows the effect of temperature on the decarboxylation
of tetrafluorophthalic acid. The reactions were carried out at tem-
peratures of 423.15, 433.15, 443.15, and 453.15 K with an ammonia
concentration of 13.4 mmol/L and an initial reactant concentration
of 20 mmol/L. High reaction temperature significantly accelerated
the decarboxylation rate of tetrafluorophthalic acid. Nearly com-
plete conversion occurred after about 90 min at 453.15 K. The
conversion at 423.15 K, however, was only about 65% after 12 h
reaction.
F
F
F
0
1
2
Scheme 1. Dissociation process for tetrafluorophthalic acid.
in the rate constants as determined by the parameter estima-
tion software. The rate constants at each temperature were fitted
by the Arrhenius equation. The Arrhenius parameters, as deter-
mined from unweighted linear regression of ln k vs. 1000/T, are
Ea = 190 11 kJ mol−1, and A = 1022.5 1.3 h−1
.
3.4. Kinetics on decarboxylation of tetrafluorophthalic acid
3.5. Mechanism on decarboxylation of tetrafluorophthalic acid
Our previous work indicated that the decarboxylation of
pentafluorobenzoic and quinolinic acid exhibited a first order
kinetics [16]. Thus, we fitted the data of conversion of tetraflu-
orophthalic acid versus reaction time at each temperature by
Origin (Version 7). The calculated decarboxylation rate constants
were determined as 0.0959 0.0024, 0.378 0.007, 1.39 0.06,
3.28 0.14 h−1 at 423.15, 433.15, 443.15, and 453.15 K, respec-
tively. The curves in Fig. 3 show that the yield profiles calculated by
the first-order model well represented the experimental data at all
temperatures. The uncertainties shown are the standard deviations
Fig. 1 shows a significant effect of the ammonia concentra-
tion in solution on the decarboxylation of tetrafluorophthalic acid.
Additionally, Fig. 2 shows that the initial concentration of reactant
remarkably impacted the reaction in the presence of ammonia. As
commonly known, the dissociation process for dibasic acid under-
goes step by step as shown in Scheme 1. The distribution fraction
of the three forms in an aqueous phase strongly depends on its
pH value which is dictated by the concentration of acidic reac-
tant and the amount of added ammonia into solution. For better

J. Fu et al. / Applied Catalysis A: General 515 (2016) 10–15
13
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
caculated value
experimental value
δ
1
0
1
2
3
4
5
6
7
8
9
10
pH of the solution
Fig. 5. Experimental and calculated decarboxylation rate constant at 453.15 K and
Fig. 4. Decarboxylation rate constant (at 453.15 K) and distribution fraction of vari-
ous species from tetrafluorophthalic acid at different pH value. ␦0 is the distribution
distribution fraction of different forms from tetrafluorophthalic acid at different pH
−
value. ␦1 is the distribution fraction of HC8O4F4
.
fraction of H2C8O4F4. ␦1 is the distribution fraction of HC8O4F4−. ␦2 is the distribu-
2−
tion fraction of C8O4F4
.
Then the following equation can be obtained by combining Eqs. (1)
and (2).
Table 1
Rate constant for the decarboxylation of tetrafluorophthalic acid at different pH
value.
1.6054Ka1 10−pH
k(T = 443.15K) =
+ 0.3357
(3)
(10−pH
)
2 + 10−pHKa + Ka Ka
Initial concentration of reactant/mmol/L
pH
k/h−1
1
1
2
10
20
30
40
2.558
1.94
1.706
1.56
1.3743 0.0281
1.2766 0.0467
0.9897 0.0350
0.7908 0.0325
According to the data in Fig. 3, we used a first-order rate equation
to fit conversion versus time at each temperature (in Section 3.4).
The result shows that the conversion rate of tetrafluorophthalic
acid fits a first-order equation, based on which rate constants and
apparent activation energy for the decarboxylation were obtained.
The Arrhenius equation for the decarboxylation rate constant (k(T))
can be expressed as
understanding of the chemistry and mechanism for the decarboxy-
lation reaction in the ammonia-enriched aqueous phase, the pH
value of the reaction solution was measured and correlated with
the rate constants of the decarboxylation reaction. As shown in
Fig. 4, the rate constant of the decarboxylation reaction increased
significantly with the increase of pH value.
ꢀ
ꢁ
k(T) = k(T = 443.15K)e E
(4)
1
1
T
a
R
−
443.15
Taken together, the effects of the ammonia concentration, initial
concentration of reactant and temperature on the decarboxyla-
tion of tetrafluorophthalic acid can be expressed as the following
equation
In order to estimate the distribution fraction of the three forms
in the aqueous phase, the dissociation constants of tetrafluo-
rophthalic acid were determined by potentiometric titration [19]
at room temperature using an ionic background of 0.1 mol/L
of KNO3. The values were obtained as pKa1 = 1.88 0.15 and
pKa2 = 3.16 0.02. The relationship between distribution fraction
for the three forms and pH value of the solution are shown in Fig. 4.
By comparing the rate constant of the decarboxylation with the dis-
tribution fraction of the monovalent anion form, it was suggested
that the rate constant increased significantly with the increase of
the amount of monovalent anion form. These observations and
results indicated that the decarboxylation rate of tetrafluoroph-
thalic acid was determined by the amount of monovalent anion
form. The distribution fraction of the monovalent anion form over
pH value of the solution was calculated using the following equa-
tion.
ꢂ
ꢃ
ꢀ
ꢁ
1.6054Ka1 10−pH
+ 0.3357 e E
(5)
1
1
a
R
−
443.15
T
k(T) =
(10−pH
)
2 + 10−pHKa + Ka Ka
1
1
2
The rate constant of decarboxylation at 453.15 K was calculated
by Eq. (5), and the results are shown in Fig. 5. Meanwhile, the distri-
bution fraction of the monovalent anion form and the rate constants
for decarboxylation obtained from experiments at 453.15 K are also
shown in Fig. 5. These results suggested that the decarboxylation
rate constants varied significantly with the distribution fraction
of the monovalent anion form and the experimental data were
directionally similar to the calculated values. The profile of calcu-
lated rate constant using the model approximately matches the
experimental data. Generally, the experimental rate constant was
lower than the calculated value, which might be derived from the
differing dissociation constant for the tetrafluorophthalic acid at
different temperatures and errors in estimating the experimental
values using only one data set.
The mechanism for the decarboxylation of tetrafluorophthalic
acid is proposed in Scheme 2, during which the ammonia plays
a role in the proton transfer for the decarboxylation [10]. As pH
value of the solution increases with the addition of ammonia, the
protonated form losses protons and was subsequently converted
to other forms. The decarboxylation can be remarkably promoted
at an adequate pH range from 2.2–2.4, when the dominant form in
the aqueous phase is the monovalent anion.
[HC8O4F−]
Ka1 10−pH
2 + 10−pHKa + Ka Ka
4
ı1
=
=
(1)
c
(10−pH
)
1
1
2
where ␦1 is the distribution fraction of the monovalent anion form
(HC8O4F4−), c is the total concentration of tetrafluorophthalic acid
and [HC8O4F4−] is the concentration of the monovalent anion form.
As such, an assumption was made that the rate constant of the
decarboxylation was linearly relevant to the amount of monovalent
anion form in the reaction medium. The linear equation fitted by
the data in Table 1 can be expressed as
k(T = 443.15K) = 0.3357 + 1.6054ı1
(2)

14
J. Fu et al. / Applied Catalysis A: General 515 (2016) 10–15
F
F
F
F
-
F
F
COOH
COOH
F
F
COO
+
+
NH4
NH3·H2O
+
COOH
F
F
F
-
OOC
F
F
F
F
+
+
NH4
+
CO2
NH3·H2O
HOOC
HOOC
F
Scheme 2. Mechanism for the decarboxylation of tetrafluorophthalic acid.
In addition, the conversion variations of 2,3,4,5-tetrafluorobenzoic
acid and 2,4,5-trifluorobenzoic acid were different from that of
tetrafluorophthalic acid. With the increase of ammonia loading,
the decarboxylation conversions of 2,3,4,5-tetrafluorobenzoic acid
and 2,4,5-trifluorobenzoic acid first increased and then kept sta-
ble, not similar with the variation trend of tetrafluorophthalic acid
conversion. It attributed to that 2,3,4,5-tetrafluorobenzoic acid and
2,4,5-trifluorobenzoic acid are monocarboxylic acid but tetrafluo-
rophthalic acid is dicarboxylic acid.
100
100
90
90
80
80
70
70
60
60
50
50
40
40
Through the preceding study and discussion, the variation of
conversion is closely related to the distribution fraction of the
monovalent anion form of multi-fluorobenzoic acids over pH value
of the solution. Different monocarboxylic acids have different pKa
value, so they have different distribution fractions of the mono-
valent anion which can explain why different carboxylic acids
have different optimal ammonia concentrations. When reaction
substrate is dicarboxylic acid, as commonly known, the ease of
the decarboxylation reactions depended upon the type of the
substitution of the aromatic compound, fully ionized specie of
tetrafluorophthalic acid is not favorable for the decarboxylation. As
a result, the conversion of tetrafluorophthalic acid firstly increased
and then significantly decreased with the increase of ammonia
loading.
30
30
2,3,4,5-tetrafluorobenzoic acid (513.15K)
2,4,5- trifluorobenzoic acid (523.15K)
20
20
10
10
0
0
0
0
10
10
20
20
30
30
40
40
50
50
60
60
70
70
ammonia concentration/mmol/L
Fig. 6. Effect of ammonia concentration on the decarboxylation of 2,3,4,5-
tetrafluorobenzoic acid (513.15 K, 1.5 h) and 2,4,5-trifluorobenzoic acid (523.15 K,
3 h).
3.6. Decarboxylation of multi-fluorobenzoic acids
The decarboxylation of 2,3,4,5-tetrafluorobenzoic acid and
2,4,5-trifluorobenzoic acid in NH3-HTLW were investigated,
and the results are shown in Fig. 6. The concentration of
2,3,4,5-tetrafluorobenzoic acid or 2,4,5-trifluorobenzoic acid was
30 mmol/L. 2,3,4,5-tetrafluorobenzoic acid was reacted in NH3-
HTLW at 513.15 K for 1.5 h, and 2,4,5-trifluorobenzoic acid
was reacted in NH3-HTLW at 523.15 for 3 h. The standard
4. Conclusion
A green technology for the decarboxylation of tetrafluoroph-
thalic acid to 2,3,4,5-tetrafluorobenzene in NH3-enriched high
temperature liquid water (HTLW) was developed. The decarboxy-
lation of tetrafluorophthalic acid exhibited the first-order kinetics,
and the activation energy was determined to be 190 kJ mol−1. The
addition of adequate amount of ammonia to the HTLW could sig-
nificantly enhance the reaction rates and had no side effect on the
selectivity to 2,3,4,5-tetrafluorobenzoic acid. The effects of ammo-
nia concentration, initial reactant concentration and temperature
on the decarboxylation of tetrafluorophthalic acid were correlated
using an equation. The results indicated that adequate addition of
ammonia could adjust the pH of the reaction medium into 2.2–2.4,
where the dominant form of the decarboxylation is the monova-
deviations in Fig.
6 were determined from three replicate
experiments. Similar phenomenons were observed that the con-
centration of ammonia significantly impacted the decarboxylation
of 2,3,4,5-tetrafluorobenzoic acid or 2,4,5-trifluorobenzoic acid.
Without the addition of ammonia, the conversions of 2,3,4,5-
tetrafluorobenzoic acid and 2,4,5-trifluorobenzoic acid were 29.2%
and 12.1%, respectively. When 13.4 mmol/L of ammonia was
added, the conversions of 2,3,4,5-tetrafluorobenzoic acid and 2,4,5-
trifluorobenzoic acid increased to 93.6% and 44.9%, respectively.

J. Fu et al. / Applied Catalysis A: General 515 (2016) 10–15
15
lent anion. The pH values of the aqueous solution could impact the
conversion of carboxylic acids by influencing their distribution frac-
tions of the monovalent anion. Overall, ammonia plays a significant
role in the proton transfer during the decarboxylation.
[5] B.K. Srivastava, M. Solanki, B. Mishra, R. Soni, S. Jayadev, D. Valani, M. Jain, P.R.
Patel, Bioorg. Med. Chem. Lett. 17 (2007) 1924–1929.
[6] J.M. Blondeau, Clin. Ther. 21 (1999) 3–40.
[7] M. Li, D.B. Wei, Y.G. Du, J. Environ. Sci. (China) 26 (2014) 1837–1842.
[8] C. Ma, J. Sun, R. Zhang, J. Coord. Chem. 61 (2008) 211–219.
[9] L.-L. Qiu, J.-S. Sun, J.-K. Li, R.-F. Zhang, Acta. Crystallogr. Sect. E. Struct. Rep.
Online 63 (2007) m2035–m2036.
[10] B. Gierczyk, G. Wojciechowski, B. Brzezinski, E. Grech, G. Schroeder, J. Phys.
Org. Chem. 14 (2001) 691–696.
Acknowledgements
[11] G. Cahiez, A. Moyeux, O. Gager, M. Poizat, Adv. Synth. Catal. 355 (2013)
790–796.
[12] P. Lu, C. Sanchez, J. Cornella, L. Larrosa, Org. Lett. 11 (2009) 5710–5713.
[13] J.S. Dickstein, C.A. Mulrooney, E.M. O’Brien, B.J. Morgan, M.C. Kozlowski, Org.
Lett. 9 (2007) 2441–2444.
This work was supported by the National Natural Science Foun-
dation of China (No. 21476204, 21306165, 21436007), Zhejiang
Provincial Natural Science Foundation of China (No. LZ14B060002).
[14] L.J. Gooßen, W.R. Thiel, N. Rodríguez, C. Linder, B. Melzer, Adv. Synth. Catal.
349 (2007) 2241–2246.
References
[15] R.W. Berninger, T. Cohen, J.T. Word, J. Org Chem. 43 (1978) 837–848.
[16] J. Fu, P.E. Savage, X.Y. Lu, Ind. Eng. Chem. Res. 48 (2009) 10467–10471.
[17] X.Y. Lu, Z. Li, F. Gao, Ind. Eng. Chem. Res. 45 (2006) 4145–4149.
[18] G.W. Howe, M. Bielecki, R. Kluger, J. Am. Chem. Soc. 134 (2012) 20621–20623.
[19] H.A. Dondas, Y. Nural, H. Sarı, H. Atabey, S. Belveren, M. Gemili, Int. J. Anal.
Chem. 2014 (2014) 1–6.
[1] H. Li, J. Liu, X.S. Chen, T.T. Ren, J. Mol. Liq. 166 (2012) 67–69.
[2] Y. Todo, H. Takagi, F. Iino, K. Hayashi, M. Takata, H. Kuroda, K. Momonoi, H.
Narita, Chem. Pharm. Bull. 42 (1994) 2629–2632.
[3] M.V. de Almeida, M.F. Saraiva, M.V. de Souza, C.F. da Costa, F.R. Vicente, M.C.
Lourenco, Bioorg. Med. Chem. Lett. 17 (2007) 5661–5664.
[4] Q.R. Qi, J. Pan, X.Q. Guo, L.L. Weng, Y.F. Liang, Bioorg. Med. Chem. Lett. 22
(2012) 7688–7692.