Convergent Paired Electrochemical Synthesis of Azoxy and Azo Compounds: An Insight into the Reaction Mechanism

Article abstract of DOI:10.1021/acs.orglett.1c02304

A convergent paired electrochemical method was developed for the synthesis of azoxy and azo compounds starting from the corresponding nitroarenes. We propose a unique mechanism for electrosynthesis of azoxy and azo compounds. We find that both anodic and cathodic reactions are responsible for the synthesis of these compounds. The synthesis of azoxy and azo derivatives have been successfully performed in an undivided cell, using carbon rod electrodes, by constant current electrolysis at room temperature.

Full text of DOI:10.1021/acs.orglett.1c02304

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Letter
Convergent Paired Electrochemical Synthesis of Azoxy and Azo
Compounds: An Insight into the Reaction Mechanism
Ali Sadatnabi, Niloofar Mohamadighader, and Davood Nematollahi*
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ABSTRACT: A convergent paired electrochemical method was developed for the synthesis of azoxy and azo compounds starting
from the corresponding nitroarenes. We propose a unique mechanism for electrosynthesis of azoxy and azo compounds. We find
that both anodic and cathodic reactions are responsible for the synthesis of these compounds. The synthesis of azoxy and azo
derivatives have been successfully performed in an undivided cell, using carbon rod electrodes, by constant current electrolysis at
room temperature.
compounds at the cathode surface. However, the above-
everal strategies for the synthesis of azoxy and azo
Scompounds including the use of traditional oxidants/ mentioned methods have some disadvantages such as tedious
procedures, toxic/expensive solvents and reagents, and the use
of unconventional electrodes. A most important point that is
not addressed in these papers is the role of the anodic reaction
in the formation of azoxy compounds. Contrary to published
data, we have found that both anodic and cathodic reactions
are involved in the formation of azoxy compounds (convergent
paired electrochemical synthesis). Some useful data on paired
electrochemical processes are reported in the literature.32 In
this strategy, the overall energy consumption is 50% less than
that for conventional methods.33
Cyclic voltammograms (CVs) of the studied halonitroben-
zenes are shown in Figure 1. CVs of p-bromonitrobenzene
(1a) have been recorded in two potential ranges (Figure 1 part
I).
reductants, the use of heavy metals, and electrochemical
methods have been reported. In the first strategy, the synthesis
of the mentioned compounds is performed through oxidation
of amines or reduction of nitro compounds by various oxidants
or reductants, such as H2O2,1−8 I2/DABCO,9 tertiary butyl
hydroperoxide,10 tetrabutylammonium peroxymonosulfate11
(Supporting Information (SI), page S7), and sodium
borohydride.12−14 Although these methods are efficient, there
are some important drawbacks including the use of aromatic
amines as starting toxic materials,15 costly terms, and toxic and
expensive reagents and solvents. The second strategy is the
reduction of nitro compounds using heavy metals. Accordingly,
various methods have been reported using samarium metal,16
thallium metal,17 zinc/NH4Cl,18 copper(I) salts,19 palladium
nanoclusters,20 Ni-TiO2,21 gold nanoparticles,22 Rh nanocryst-
als,23 iridium and rhodium,24 Ni/graphene nanocomposites,25
Ni@C-CeO2,26 Au@zirconium-phosphonate nanoparticles,27
Fe and N codoped mesoporous carbon,28 and photo-
reduction.29 These methods are valuable, and the problem of
using aromatic amines has been solved. However, these
methods still have disadvantages such as heavy metal pollution,
toxic and expensive reagents, tedious preparation of starting
materials/workup, and safety problems. In the third strategy,
the synthesis of azoxy and azo compounds is performed by
electrochemical methods.30,31 In these papers, the strategy for
the synthesis of azoxy compounds involves reduction of nitro
When the potential was scanned from −0.2 V to +0.4 V vs
Ag/AgCl, 1a does not show any oxidation or reduction peak
(curve a). But, upon scanning the electrode potential from
−0.2 V to −0.72 V (curve b), the voltammograms consist of an
irreversible cathodic peak (C0) which corresponds to a four-
Received: July 9, 2021
https://doi.org/10.1021/acs.orglett.1c02304
© XXXX American Chemical Society
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A

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dimerization reaction occurs between two phenylhydroxyl-
amine radicals (3•).34,35
Controlled potential coulometry (CPC) of 1a and 2a (o-
bromonitrobenzene) was carried out followed by voltammetric
analysis of the electrolyzed solutions (Figure 2) to identify the
products and to determine the number of electrons transferred.
Figure 1. CVs of 1.0 mM of halonitrobenzenes at GC electrode, in
aqueous solution containing phosphate buffer (c = 0.2 M, pH = 3.0)/
acetonitrile (50/50 v/v). Scan rate: 100 mV/s at room temperature.
Inset I, IV): Differential pulse voltammograms of N-(4-
bromophenyl)hydroxylamine and N-(2-bromophenyl)hydroxylamine
obtained from 1a and o-bromonitrobenzene (2a) under the same
conditions. For DPV: step potential, 50 mV; modulation amplitude,
25 mV; modulation time, 0.05 s; interval time, 0.5 s.
electron reduction of the nitro group to hydroxylamine group
and a reversible redox couple corresponding to the redox
activity of the phenylhydroxylamine/phenylhydroxylamine
radical (3/3• and 4/4•) (Scheme 1).
Figure 2. Part I: CVs of 0.5 mmol 1a during CPC in an undivided cell
at −1.10 V versus Ag/AgCl. Inset: variation of IpC0 versus consumed
charge. Part II: CVs of 1a during CPC after scanning the potential
from −0.20 to +0.70 V. Voltammograms are taken after consumption
of (a) 0, (b) 50, (c) 100, (d) 150, and (e) 200 C. Parts III and IV are
CVs of 2a during CPC under similar conditions with 1a at −0.90 V
after consumption of (a) 0, (b) 75, (c) 150, (d) 225, and (e) 300 C.
Other conditions are similar to those in Figure 1.
Scheme 1. Reduction/Oxidation Pathway of Simple Nitro
Aromatic Compounds
Parts I and III show the effect of charge passed on the
cathodic peak C0 of 1a and 2a, respectively. As can be seen,
IpC0 of 1a gradually decreases with the progress of coulometry
and disappears with the consumption of 4e− per molecule of
1a (Figure 2, part I, inset). This number of electrons confirms
the reduction of the nitro group to hydroxylamine. However,
under the same conditions, the number of transferred electrons
for the reduction of 2a was calculated to be 6e− (Figure 2, part
III, inset). In addition, during the electrolysis of 2a, a new
cathodic peak (C−1) appears. These results show that the
presence of substituent groups at different positions causes the
molecule to have different electrochemical behaviors. The
reason for the consumption of 6 electrons in the reduction of
2a is stated later. Furthermore, parts II and IV of this figure
show the formation and increase of the anodic and cathodic
peaks A1 and C1 with the progress of coulometry.
The synthesis of desired products was carried out by
constant-current electrolysis of nitroarenes. The suggested
mechanism for the synthesis of azoxy compounds (5) is shown
in Scheme 2. As can be seen, the cathodically generated N-(4-
halophenyl)hydroxylamine (3) is oxidized at the anode to
produce N-(4-halophenyl)hydroxylamine radical (3•). The
radical coupling reaction of 3• afforded the corresponding
The pathway leading to the oxidation of cathodically
generated phenylhydroxylamine (A1/C1) is given in Scheme
1. It should be noted that the single-electron transfer oxidation
of the cathodically generated N-(4-bromophenyl)hydroxyl-
amine (3a) has been examined using the half-peak width (W1/2
= 3.52RT/nF) of the differential pulse voltammogram of this
compound (Figure 1, part I, inset).34
The effect of potential scan rate on CVs of 3a has been
studied, to obtain more data on the mechanism of formation of
azoxy compounds (SI, page S13). The study shows that the
peak current ratio (IpC1/IpA1) is scan rate dependent and
becomes larger at faster scan rates. This finding confirms the
presence of a following chemical reaction after the electron
transfer step.
The effect of 1a concentration on the voltammetric behavior
of this compound is also studied (SI, page S13). It shows that
IpC1/IpA1 is concentration-dependent and becomes smaller with
increasing 1a concentration. This suggests that under the
conditions that we have performed these experiments, a
B
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Scheme 2. Electrochemical Reaction Mechanism for the
Synthesis of Azoxy and Azo Compounds
azoxy compound. It should be noted that, in addition to 3, the
oxidation of water at the anode causes the balance of electrons.
The reaction mechanism for the synthesis of azo compounds
(6) is similar to that of azoxy compounds, except that the
azoxy compound in the next step is reduced at the cathode and
converted to the azo compound by removing a water molecule
(Scheme 2). According to the Scheme 2, two molecules of
ortho-halonitrobenzene and 10 electrons are needed to
synthesize each molecule of the azo compound. Therefore,
in this case, theoretically 5 electrons are consumed per ortho-
halonitrobenzene molecule. However, in the experiments we
performed in an undivided cell, due to the occurrence of
phenomena such as the back reaction, the number of electrons
was 6 for each ortho-halonitrobenzene molecule. The reduction
of the ortho-azoxy compounds may be related to the higher
solubility of these compounds compared to para-azoxy
compounds (SI, pages S16 and S18). In addition, the observed
cathodic peak C−1 in Figure 2, part III, is due to the reduction
of the ortho-azoxy compound to the ortho-azo compound.
In order to prove the proposed mechanism, the synthesis of
azoxy (or azo) compounds was also examined under exactly
the same conditions in a divided cell (Figure 3). The results
clearly show that no trace of the formation of the azoxy (or
azo) compound was observed when a divided cell is used. In
other words, the participation of the anodic process in product
formation is essential.
To improve the synthetic efficiency, the synthesis of azoxy
and azo compounds was also studied under constant current
conditions. The effect of current density on the yield of 5a was
initially investigated (SI, page S14). These experiments were
performed under the following conditions: charge consumed,
4.0 F; 1a amount, 1.0 mmol; solvent, water (0.2 M phosphate
buffer, pH = 3.0)/acetonitrile (50/50 v/v) mixture. The results
show that the optimum value for the current density is 1.2
mA/cm2 (Iapp = 40 mA). In this current density, the yield of
79% was obtained for the synthesis of 5a. Insufficient applied
potentials for the formation of N-(4-bromophenyl) hydroxyl-
amine at low current densities can be the reason for the low
yield under these conditions. On the other hand, the over-
reduction of 1a at the cathode, overoxidation of N-(4-
bromophenyl)hydroxylamine at the anode, and reduction
and/or oxidation of 5a (or solvent) are the main factors in
decreasing the product yield at higher current densities.
The effect of charge consumed on the yield of 5a was also
investigated (SI, page S14). These experiments were
performed under an optimum current density of 1.2 mA/
Figure 3. Constant current electrolysis of 2a (0.5 mmol) in undivided
(above) and divided (below) cells in acetonitrile/water (containing
0.2 M phosphate buffer, pH = 3.0) mixture (50/50 v/v), at room
temperature. Japp = 1.2 mA/cm2 (Iapp = 40 mA).
cm2. The results show that the optimum value for the charge
consumed is 4.0 F which is the theoretical amount of electricity
necessary for the reduction of 1.0 mmol of 1a (Scheme 2). It
seems that the reduction and/or oxidation of 5a are the main
factors in decreasing the product yield at higher charge
consumed. The effect of solution pH (in the range 2−6) on
the yield of 5a under optimum conditions was also studied.
Our results show that the highest yield and purity of products
were obtained at pH 3.0. Similar optimizations were also
performed for the synthesis of 6a. These experiments were
performed on 2a and yielded similar results to those obtained
for 5a. The only significant difference was in the amount of
electricity consumed. In this case, the optimal amount of
electricity needed for the synthesis of 6a was 6.0 F (slightly
more than the theoretical value of 5.0 F). Under these
conditions, the yield of 64% was obtained for the synthesis of
6a (SI, page S9).
The effect of anode and cathode materials was also studied
on the yield of 5a. The results of this series of experiments are
shown in Table 1. As can be seen, the maximum yield of 79%
was obtained, when carbon is used for both the anode and
cathode.
Table 1. Dependence of 5a Yield on Electrode Material
entry
cathode
Carbon
Carbon
Carbon
Stainless Steel
Zn
Fe
Cu
anode
Carbon
Stainless Steel
Cu
Carbon
Carbon
Carbon
Carbon
yield [%]
79
31
1
2
3
4
5
6
7
no reaction
62
38
57
50
C
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The products and the yields of 5 and 6 compounds are
summarized in Table 2. These data show that we were able to
develop an efficient method to synthesize azoxy and azo
derivatives in a one-pot reaction with a 50−86% overall yield.
nitroarenes is electrolyzed under optimal conditions. The azo
formation shown in entries 9−12 is probably due to the
solubility of the azoxy intermediate (as it happens for ortho-
bromo derivatives) as well as the more intense adsorption of
their dependent species (SI, page S19). It also should be noted
that our efforts to synthesize azo or azoxy compounds were
unsuccessful, when nitroarenes have the group COOH or
CHO, which is possibly due to the participation of COOH and
CHO groups in the reduction process in competition with the
nitro group and/or due to participation in the oxidation
process in competition with the hydroxylamine group.
Table 2. Scope of the Azoxy and Azo Derivatives Synthesis
This method consumes less energy than other methods due
to its paired strategy and also does not require catalysts,
hazardous chemicals, and challenging workups. According to
these characteristics, it can be concluded that the proposed
method is greener than other published methods.
In this work, we discovered for the first time that the anodic
oxidation of cathodically generated phenylhydroxylamine is
necessary for the synthesis of titled compounds. Accordingly,
we propose a convergent paired electrochemical mechanism in
which the −NO2 group of nitroarenes is reduced to the
hydroxylamine group at the cathode surface and the cathodi-
cally generated phenylhydroxylamine compound is oxidized at
the anode surface to its free radical and dimerization of radicals
yields the corresponding azoxy compounds.
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c02304.
Some explanations about the optimizations, effect of pH
(Pourbaix diagram), experimental details and spectral
data for all compounds (PDF)
AUTHOR INFORMATION
Corresponding Author
■
Davood Nematollahi − Faculty of Chemistry, Bu-Ali-Sina
University, Hamedan, Iran; orcid.org/0000-0001-9638-
224X; Email: nemat@basu.ac.ir
Authors
Ali Sadatnabi − Faculty of Chemistry, Bu-Ali-Sina University,
Hamedan, Iran
Niloofar Mohamadighader − Faculty of Chemistry, Bu-Ali-
Sina University, Hamedan, Iran
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c02304
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors wish to acknowledge Iran National Science
Foundation (INSF) for financial support of this work. The
authors also acknowledge the Bu-Ali Sina University Research
Council.
In addition to the products shown in entries 1−3 and 6−8,
entries 4, 5, 9, and 10 are examples that show the method
tolerates a variety of functional groups such as Cl, Br, I, CN,
CH3CO, and CH3. In addition, entries 11 and 12 show that the
proposed method can easily produce diverse products such as
6f and 6g through the coupling of two different nitrobenzenes
and prove that the method also tolerates the combinations of
different nitroarenes. In these cases, a solution containing both
REFERENCES
■
(1) Ke, L.; Zhu, G.; Qian, H.; Xiang, G.; Chen, Q.; Chen, Z.
Catalytic selective oxidative coupling of secondary N-alkylanilines: an
approach to azoxyarene. Org. Lett. 2019, 21, 4008−4013.
D
https://doi.org/10.1021/acs.orglett.1c02304
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
(2) Voutyritsa, E.; Theodorou, A.; Kokotou, M. G.; Kokotos, C. G.
Organocatalytic oxidation of substituted anilines to azoxybenzenes
and nitro compounds: mechanistic studies excluding the involvement
of a dioxirane intermediate. Green Chem. 2017, 19, 1291−1298.
(3) Singh, B.; Mandelli, D.; Pescarmona, P. P. Efficient and selective
oxidation of aromatic amines to azoxy derivatives over aluminium and
gallium oxide catalysts with nanorod morphology. ChemCatChem
2020, 12, 593−601.
of nitroarenes to azoxy compounds over Ni-TiO2 catalyst. Mol. Catal.
2020, 490, 110943.
(22) Liu, X.; Ye, S.; Li, H. Q.; Liu, Y. M.; Cao, Y.; Fan, K. N. Mild,
selective and switchable transfer reduction of nitroarenes catalyzed by
supported gold nanoparticles. Catal. Sci. Technol. 2013, 3, 3200−
3206.
(23) Dai, X.; Wei, Q.; Duong, T.; Sun, Y. Selective transfer coupling
of nitrobenzene to azoxybenzene on Rh nanoparticle catalyst
promoted by photoexcited hot electrons. ChemNanoMat 2019, 5,
1000−1007.
(24) Zhang, Z. P.; Wang, X. Y.; Yuan, K.; Zhu, W.; Zhang, T.; Wang,
Y. H.; Ke, J.; Zheng, X. Y.; Yan, C. H.; Zhang, Y. W. Free-standing
iridium and rhodium-based hierarchically-coiled ultrathin nanosheets
for highly selective reduction of nitrobenzene to azoxybenzene under
ambient conditions. Nanoscale 2016, 8, 15744−15752.
(25) Pahalagedara, M. N.; Pahalagedara, L. R.; He, J.; Miao, R.;
Gottlieb, B.; Rathnayake, D.; Suib, S. L. Room temperature selective
reduction of nitrobenzene to azoxybenzene over magnetically
separable urchin-like Ni/graphene nanocomposites. J. Catal. 2016,
336, 41−48.
(26) Liu, L.; Concepción, P.; Corma, A. Modulating the catalytic
behavior of non-noble metal nanoparticles by inter-particle interaction
for chemoselective hydrogenation of nitroarenes into corresponding
azoxy or azo compounds. J. Catal. 2019, 369, 312−323.
(27) Ferlin, F.; Cappelletti, M.; Vivani, R.; Pica, M.; Piermatti, O.;
Vaccaro, L. Au@ zirconium-phosphonate nanoparticles as an effective
catalytic system for the chemoselective and switchable reduction of
nitroarenes. Green Chem. 2019, 21, 614−626.
(4) Barak, G.; Sasson, Y. Effect of phase-transfer catalysis on the
selectivity of hydrogen peroxide oxidation of aniline. J. Org. Chem.
1989, 54, 3484−3486.
(5) Wan, Y. S. S.; Yeung, K. L.; Gavriilidis, A. TS-1 oxidation of
aniline to azoxybenzene in a microstructured reactor. Appl. Catal., A
2005, 281, 285−293.
(6) Neimann, K.; Neumann, R. A new non-metal heterogeneous
catalyst for the activation of hydrogen peroxide: a perfluorinated
ketone attached to silica for oxidation of aromatic amines and alkenes.
Chem. Commun. 2001, 487−488.
(7) Sakaue, S.; Tsubakino, T.; Nishiyama, Y.; Ishii, Y. Oxidation of
aromatic amines with hydrogen peroxide catalyzed by cetylpyridinium
heteropolyoxometalates. J. Org. Chem. 1993, 58, 3633−3638.
(8) Bamoharram, F. F.; Heravi, M. M.; Roshani, M.; Akbarpour, M.
Catalytic performance of Preyssler heteropolyacid as a green and
recyclable catalyst in oxidation of primary aromatic amines. J. Mol.
Catal. A: Chem. 2006, 255, 193−198.
(9) Yu, X.; Ding, W.; Ge, P.; Wang, S.; Wang, J. Oxidative coupling
of aromatic amines and nitrosoarenes: iodine-mediated formation of
unsymmetrical aromatic azoxy compounds. Adv. Synth. Catal. 2018,
360, 3150−3156.
(10) Waghmode, S. B.; Sabne, S. M.; Sivasanker, S. Liquid phase
oxidation of amines to azoxy compounds over ETS-10 molecular
sieves. Green Chem. 2001, 3, 285−288.
(28) Wang, J.; Yu, X.; Shi, C.; Lin, D.; Li, J.; Jin, H.; Chen, X.; Wang,
S. Iron and nitrogen co-doped mesoporous carbon-based heteroge-
neous catalysts for selective reduction of nitroarenes. Adv. Synth.
Catal. 2019, 361, 3525−3531.
(11) Rezaeifard, A.; Jafarpour, M.; Naseri, M. A.; Shariati, R. A rapid
and easy method for the synthesis of azoxy arenes using
tetrabutylammonium peroxymonosulfate. Dyes Pigm. 2008, 76,
840−843.
(12) Ohe, K.; Uemura, S.; Sugita, N.; Masuda, H.; Taga, T. Sodium
arenetellurolate-catalyzed selective conversion of nitro aromatics to
aromatic azoxy or azo compounds and its application for facile
preparation of 3, 3′-and 4, 4’-bis [beta(aryltelluro) vinyl] azobenzenes
from (3-and 4-nitrophenyl) acetylenes. J. Org. Chem. 1989, 54, 4169−
4174.
(13) Ren, P.; Pan, S.; Dong, T.; Wu, S. Catalytic reduction of
nitroarenes to azoxybenzenes with sodium borohydride in the
presence of bismuth. Synth. Commun. 1996, 26, 3903−3908.
(14) Belattar, N.; Benayache, S.; Benayache, F. Diphenyl diselenide−
catalyzed reductive coupling of nitroarenes to aromatic azo and azoxy
compounds with sodium borohydride in alkaline ethanol. Curr. Org.
Synth. 2018, 15, 1182−1190.
(15) Goljani, H.; Tavakkoli, Z.; Sadatnabi, A.; Masoudi-Khoram, M.;
Nematollahi, D. A new electrochemical strategy for the synthesis of a
new type of sulfonamide derivatives. Sci. Rep. 2020, 10, 1−10.
(16) Hou, Z.; Fujiwara, Y.; Taniguchi, H. Lanthanides in organic
synthesis. Samarium metal promoted selective formation of azoxy
compounds. J. Org. Chem. 1988, 53, 3118−3120.
(17) McKillop, A.; Raphael, R. A.; Taylor, E. C. Thallium in organic
synthesis. XI. Preparation of azoxy compounds. J. Org. Chem. 1970,
35, 1670−1672.
(18) Khan, F. A.; Sudheer, C. Oxygen as moderator in the zinc-
mediated reduction of aromatic nitro to azoxy compounds.
Tetrahedron Lett. 2009, 50, 3394−3396.
(29) Dai, Y.; Li, C.; Shen, Y.; Lim, T.; Xu, J.; Li, Y.;
Niemantsverdriet, H.; Besenbacher, F.; Lock, N.; Su, R. Light-tuned
selective photosynthesis of azo- and azoxy-aromatics using graphitic
C3N4. Nat. Commun. 2018, 9, 60−66.
(30) Silvester, D. S.; Wain, A. J.; Aldous, L.; Hardacre, C.; Compton,
R. G. Electrochemical reduction of nitrobenzene and 4-nitrophenol in
the room temperature ionic liquid [C4dmim][N (Tf) 2]. J.
Electroanal. Chem. 2006, 596, 131−140.
(31) Wirtanen, T.; Rodrigo, E.; Waldvogel, S. R. Recent advances in
the electrochemical reduction of substrates involving N@O bonds.
Adv. Synth. Catal. 2020, 362, 2088−2101.
(32) (a) Ibanez, J. G.; Frontana-Uribe, B. A.; Vasquez-Medrano, R.
Paired electrochemical processes: overview, systematization, selection
criteria, design strategies, and projection. J. Mex. Chem. Soc. 2017, 60,
247−260. (b) Ansari, A.; Nematollahi, D. Convergent paired
electrocatalytic degradation of p-dinitrobenzene by Ti/SnO2-Sb/β-
PbO2 anode. A new insight into the electrochemical degradation
mechanism. Appl. Catal., B 2020, 261, 118226.
(33) (a) Jamshidi, M.; Nematollahi, D.; Taheri, F.; Alizadeh, H.
Paired electrochemical method for synthesis of new phenyl-
carbonimidoyl dicyanide dyes. ACS Sustainable Chem. Eng. 2019, 7,
1956−1962. (b) Momeni, S.; Nematollahi, D. New insights into the
electrochemical behavior of acid orange 7: Convergent paired
electrochemical synthesis of new aminonaphthol derivatives. Sci.
Rep. 2017, 7, 1−10.
(34) Bard, A. J.; Faulkner, L. R. Electrochemical Methods:
Fundamentals and Applications, 2nd ed.; Wiley: New York, 2001; p
291, p 498.
(35) (a) Salehzadeh, H.; Nematollahi, D.; Rafiee, M. Electro-
chemical dimerization of 4-methylesculetin: Synthesis and kinetic
study of a highly-oxygenated dimer. J. Electroanal. Chem. 2011, 650,
226−232. (b) Nematollahi, D.; Shayani-Jam, H.; Alimoradi, M.;
Niroomand, S. Electrochemical oxidation of acetaminophen in
aqueous solutions: Kinetic evaluation of hydrolysis, hydroxylation
and dimerization processes. Electrochim. Acta 2009, 54, 7407−7415.
(c) Nematollahi, D.; Zohdijamil, Z.; Salehzadeh, H. An efficient
electrochemical method for the synthesis of N, N, N′, N′-tetraalkyl-4,
(19) Chen, Z.; Qiu, Y.; Wu, X.; Ni, Y.; Shen, L.; Wu, J.; Jiang, S.
Highly selective reduction of nitrobenzenes to azoxybenzenes with a
copper catalyst. Tetrahedron Lett. 2018, 59, 1382−1384.
(20) Yan, Z.; Xie, X.; Song, Q.; Ma, F.; Sui, X.; Huo, Z.; Ma, M.
Tandem selective reduction of nitroarenes catalyzed by palladium
nanoclusters. Green Chem. 2020, 22, 1301−1307.
(21) Shukla, A.; Singha, R. K.; Sasaki, T.; Adak, S.; Bhandari, S.;
Prasad, V.; Bordoloi, A.; Bal, R. Room temperature selective reduction
E
https://doi.org/10.1021/acs.orglett.1c02304
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
4′-azodianiline. J. Electroanal. Chem. 2014, 720, 156−161. (d) Beigi-
nejad, H.; Nematollahi, D. Electrochemical oxidation of 2,5-diethoxy-
4-morpholinoaniline in aqueous solutions. Electrochim. Acta 2013,
114, 242−250.
F
https://doi.org/10.1021/acs.orglett.1c02304
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