Selective Photoinduced Reduction of Nitroarenes to N-Arylhydroxylamines

Article abstract of DOI:10.1021/acs.orglett.0c01367

We report the selective photoinduced reduction of nitroarenes to N-arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields. The potential of this protocol reflects on the selective and straightforward conversion of two general antibiotics, azomycin and chloramphenicol, to the bioactive hydroxylamine species.

Full text of DOI:10.1021/acs.orglett.0c01367

pubs.acs.org/OrgLett
Letter
Selective Photoinduced Reduction of Nitroarenes to
N‑Arylhydroxylamines
Michael G. Kallitsakis,* Dimitris I. Ioannou, Michael A. Terzidis, George E. Kostakis,
and Ioannis N. Lykakis*
Cite This: https://dx.doi.org/10.1021/acs.orglett.0c01367
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: We report the selective photoinduced reduction of nitroarenes to
N-arylhydroxylamines. The present methodology facilitates this transformation in
the absence of catalyst or additives and uses only light and methylhydrazine. This
noncatalytic photoinduced transformation proceeds with a broad scope, excellent
functional-group tolerance, and high yields. The potential of this protocol reflects
on the selective and straightforward conversion of two general antibiotics,
azomycin and chloramphenicol, to the bioactive hydroxylamine species.
photochemical synthesis of N-AHA from nitroarenes remains
a significant challenge.
N-Arylhydroxylamines (N-AHA) are versatile organic mole-
cules with useful applications as valuable intermediates in the
synthesis of biologically active molecules, inhibitors of
polymerization, and precursors for the synthesis of other
organic fragments.1 The selective reduction of nitroarenes is
the most convenient protocol to obtain these attractive organic
scaffolds; this transformation is promoted by zinc dust in either
aqueous NH4Cl, aluminum−amalgam, or even enzymatic
biocatalysts.1 However, these reagents are used in stoichio-
metric amounts, a significant drawback; thus, alternative
methodologies have been developed. These alternative
protocols involve heterogeneous catalytic systems (with Pt,
Ru, Ni, Pd, Rh, Ir) and either molecular hydrogen1,2 or
hydrogen donor molecules including borohydrides1,3a,b or
hydrazine hydrate1,3c−e (Scheme 1). The former protocol
requires high pressures and temperatures, while the latter
promotes this selective transformation under milder reaction
conditions but the use of additives is necessary.
Light is the most abundant renewable energy source, and
therefore, photochemistry has emerged as an efficient, green,
eco-friendly approach to promote chemical transformations,
especially organic reductive processes.4 In this direction, the
photoinduced reduction of nitroarenes has been achieved via
photocatalytic hydrogenation or transfer hydrogenation
processes.5 To date, metal-based protocols, including tran-
sition-metal nanoparticles or complexes supported on active
surfaces, promote the transformation of nitroarenes to the
corresponding arylamines6,7 or the corresponding azoxy- and
azo-compounds (Scheme 1A).8 Therefore, the selective
Given the importance of N-AHA in organic chemistry and
inspired from metal-based9,10 or photochemical11 method-
ologies developed in our laboratory that facilitate the synthesis
of interesting organic scaffolds,10 we reasoned that it should be
possible to develop a direct photoinduced reduction of
nitroarenes to N-AHA with the use of methylhydrazine as
hydrogen donor molecule (Scheme 1B). To the best of our
knowledge, only specific examples with limited applicability on
the photochemical reduction of 4-nitropyridine-1-oxide12a and
para-X-substituted rich nitroarenes (X = H, Me, MeO)12b−d
into the corresponding hydroxylamines in acidic alcoholic
solvents have been reported.
In order to evaluate the photochemical reduction conditions,
we used 4-nitrotoluene 1 as a probe molecule with different
catalysts, hydrazine, or methyl hydrazine and MeOH or MeCN
as solvents (Table S1). Inspired by metal-based selective
reduction protocols of nitroarenes developed in our
laboratory,9 we initially studied the phototransformation of 1
in the presence of Cu(II) salts or complexes.10a In these cases,
a mixture of the corresponding N-(p-tolyl)hydroxylamine 1a,
toluidine 1b, and azoxy arene 1c was obtained (Table S1,
Received: April 20, 2020
https://dx.doi.org/10.1021/acs.orglett.0c01367
© XXXX American Chemical Society
Org. Lett. XXXX, XXX, XXX−XXX
A

Organic Letters
pubs.acs.org/OrgLett
Letter
Scheme 1. Photo- and Thermal-Catalytic Reductive
Processes of Nitroarenes
Table 1. Hydrazine Evaluation in the Photoinduced
Reduction of 1
b
relative yields (%)
a
A/A
hydrazines
1
1a
1b
1c
1
2
3
4
MeNHNH2
PhNHNH2
Μe2NNH2
PhNHNHPh
4-NO2PhNHNH2
TsNHNH2
NH2NH2·H2O
MeNHNH2
H2 bubbling
>99
68
32
32
5
100
100
100
63
5
6
7
8
9
23
95
48
5
29
c
100
100
100
100
100
26
10
11
12
13
14
15
16
17
18
19
d
e
f
MeNHNH2
MeNHNH2
MeNHNH2
MeNHNH2 (3 mol-excess)
MeNHNH2 (4 mol-excess)
MeNHNH2 (10 mol-excess)
MeNHNH2(15 min)
MeNHNH2(30 min)
MeNHNH2(300 min)
65
85
95
55
84
9
15
5
45
16
entries 1 and 2), while under thermal conditions we observed
that no reaction takes place (Table S1, entry 3). Similar results
were also observed in the reactions with Co(II) salts and
complexes, as catalysts, in MeOH or MeCN (Table S1, entries
4−6) and 9,10-dicyanoanthracene, and rose bengal, as
conventional photosensitizers (Table S1, entries 7 and 8).
The reaction in the absence of any catalyst but in the presence
of hydrazine hydrate (Table S1, entries 9 and 10) yields a
mixture of products, with amine 1b as the major product.
Surprisingly, when we incorporated methylhydrazine in the
absence of any catalyst, 1a was selectively formed in
quantitative yield, and the product could be isolated by a
simple filtration over a short pad of silica, thus omitting
chromatographic purification (Table 1, entry 1). To gain better
insight and rationalize this unexpected result, we performed a
set of reactions. We found that phenylhydrazine also promotes
the selective formation of hydroxylamine 1a, but at a lower
isolated yield (Table 1, entry 2); 1,1-dimethylhydrazine
performs poorly (Table 1, entry 3), whereas the use of 1,2-
diphenylhydrazine, 4-nitrophenylhydrazine, p-toluenesulfonyl-
hydrazine, or hydrazine hydrate suppresses the formation of 1a
(Table 1, entries 4−7). The addition of water (20 μL, 0.2% v/
v) with methylhydrazine did not affect the transformation of 1
to 1a (Table 1, entry 8), whereas under H2 atmosphere
(balloon) no photochemical conversion of 1 was accomplished
(Table 1, entry 9). Further control experiments revealed that
the reaction does not proceed in the absence of methylhy-
drazine or light (Scheme S1) with the use of a cutoff filter at
420 nm or upon white LED irradiation (Table 1, entries 10−
13). Moreover, a smaller amount of methylhydrazine (3 or 4
molar excess) or a shorter reaction time (15 or 30 min) leads
to the formation of 1a in moderate yield (Table 1, entries 14−
17). On the contrary, the use of methylhydrazine, in 10 molar
excess, or prolonged reactions afforded 1a in quantitative yields
100
a
Conditions: 1 (0.2 mmol), hydrazine source (1 mmol), MeCN (1
b
mL), 60 min. Relative yields of products measured by the
appropriate proton signals from the H NMR of the crude reaction
1
c
mixture. 20 μL(0.2% v/v) of H2O was added in the reaction mixture.
d
In the absence of light at 28 and 70 °C for 1 h, respectively.
e
f
Irradiation with a cutoff filter at 420 nm, t = 1 h. Irradiation using
white LED, 11 W, for 24 h.
(Table 1, entries 18 and 19). The last set of reactions included
the use of other various hydrogen donor molecules, i.e.,
hydrosilanes, boranes, ammonium formate, or formic acid and
isopropyl alcohol, which did not facilitate the selective
reduction (Table S2).
Interestingly, the reaction, except acetonitrile, takes place in
a variety of solvents including ethanol, isopropyl alcohol,
dimethyl carbonate, tetrahydrofuran, 1,2-dichloroethane, and
toluene (Table S3, entries 1−8). The reaction in ethyl acetate
showed lower selectivity (Table S3, entry 9) with significant
amounts of toluidine 1b and azoxyarene 1c. No reaction
occurs in water (Table S3, entry 10), but the use of a solvent
mixture H2O/CH3CN (1:1) promotes the reduction as well as
the formation of 1b (Table S3, entry 11).13
After establishing the optimum conditions, we assessed the
scope of the protocol toward various nitroarenes and focused
on different variations. Remarkably, this photoinduced
protocol shows a broad functional group tolerance, and a
series of nitroarenes (1−22) yielded the desired corresponding
N-AHA (1a−22a) in excellent isolated yields (Scheme 2). The
chemoselective reduction of the nitro group, in the presence of
other reducible functional groups, is a very challenging task;
however, this protocol leads to the selective and sole reduction
B
https://dx.doi.org/10.1021/acs.orglett.0c01367
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
biologically interesting molecules. Thus, aiming to expand the
scope of this protocol in pharmaceutical relevant molecules, we
attempted a direct photoinduced reduction of two antibiotics:
azomycin (23) and chloramphenicol (24).15 The hydroxyl-
amine and/or nitroso derivatives of 23 were found to exhibit
high potential for the treatment of latent tuberculosis (i.e.,
imidazole derivatives are also designed to intercalate with
intracellular nucleophiles including DNA) and treatment of
several bacterial infections. At the same time, the correspond-
ing derivatives of 24 were used as an eye ointment to treat
conjunctivitis.15a To the best of our knowledge, the already
known protocols that yield 23a and 24a involve metal-based,
electrochemical, and biosynthetic processes16 with significant
drawbacks such as low yields, difficulty in handling and
separation of the mixture of several unstable products. Notably,
the present simple methodology provides easy, clean, and
straightforward access to the corresponding N-AHA 23a and
24a in high isolated yields 96% and 90%, respectively, within
90 min (Scheme 3).
Scheme 2. Photoinduced Synthesis of Various N-AHA
Using Methylhydrazine
Scheme 3. Application of the Present Methodology to the
Selective Photo-reduction of the Antibiotics Azomycin 23
and Chloramphenicol 24
Regarding the mechanism of this photochemical trans-
formation, it is essential to note that the addition of an
equimolar amount of 9,10-dicyanoanthracene (9,10-DCA, 0.2
mmol) retards the reaction process (1a in 45% and 1c in
22%); however, the presence of 0.2 mmol of 1,3,5-
trimethoxybenzene (TMB) does not affect the reaction
conversion (1a in 90%) significantly (Scheme S3). In the
same context, the addition of the radical inhibitor TEMPO in
an equimolar amount did not suppress the reaction, which
suggests that a free radical pathway is not predominate in this
photochemical transformation (Scheme S3). These results
support a possible proton-coupled electron transfer (PCET)
process between the excited form of the nitroarene and the
methylhydrazine; however, a hydrogen atom transfer (HAT)
cannot be excluded.17
No formation of the N-AHA 5a was observed during the
photochemical reaction of the corresponding azoxy- (5c), azo-
(5e), and hydrazobenzene (5d) under the same conditions and
in the absence or in the presence of 0.2 mmol of H2O as
additive (Scheme S4). This result supports the presence of a
direct route of the reduction process.
of the nitro group to the corresponding hydroxylamine in the
presence of carboxyl, cyano, and carbonyl groups (10a−14a).
Interestingly, under the present protocol, no reductive
dehalogenated process occurs,14 and the corresponding
halogenated aromatic N-AHA 15a−18a species are formed
in excellent yields. To further identify the limitations of the
present light-driven procedure, heterocyclic substrates such as
6-nitrophthalide (21) and 6-nitro-1H-indazole (22) were
reduced, giving quantitatively the corresponding hydroxyl-
amines 21a and 22a, respectively. On the other hand, no
reduction was observed with 1-nitrohexane even after 120 min
of irradiation, a result that supports the necessity of an
aromatic ring to facilitate this transformation. A lab-scale
reaction was also performed using 1 (1 mmol) and
MeNHNH2 (5 mmol) in 3 mL of CH3CN, and the
corresponding N-AHA 1a was isolated after 2 h irradiation
time in 87% yield.
In addition, the photoinduced reaction between 5 and
methylhydrazine was monitored by UV−Vis spectroscopy
(Figure S1); the formation of the corresponding N-AHA 5a
was observed as the only product.
Of note is that the reaction of nitrosobenzene 5f with 5, 3, 2,
or even 1 equiv of methylhydrazine at 28 °C in CD3CN yields,
Given the simplicity of the present protocol, when compared
with already known methodologies,2,3 we reasoned that the
approach would be applicable for the synthesis of a series of
C
https://dx.doi.org/10.1021/acs.orglett.0c01367
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
̇
within 15 min, 5a in >85% yield (Table S9), proven by direct
1H NMR monitoring. This result supports the, possible, in situ
formation of a nitrosoarene intermediate, which is transformed
into the corresponding hydroxylamine in the presence of
methylhydrazine through a nonphotochemical pathway,
although an electrochemical reductive pathway18 can also
take part during the photoreaction.
radicals. Then the PhNO2H, through a second PCET or HAT
process with methylhydrazine, is transformed to N-phenyl-
dihydroxylamine (PhN(OH)2) and subsequently to the
nitrosobenzene intermediate, after the loss of a water molecule,
which can be directly reduced to the desired N-phenyl-
hydroxylamine (PhNHOH) through a nonphotochemical
process (Scheme 4).19,20 Although this is a plausible
mechanistic pathway, theoretical calculations and electro-
chemical studies are in progress to support this hypothesis.
In conclusion, we present an efficient methodology that
selectively reduces nitroarenes to the corresponding N-AHA.
The cooperation of nitroarenes and methylhydrazine orches-
trates a light-driven, in situ generation of nitrosoarenes which
yields N-AHA in a fast and clean manner. The protocol has a
broad scope, excellent functional group tolerance, absence of
byproducts, while other reducible functional groups remain
intact. The present photoinduced reduction methodology is
simple and applies to the bioactive molecules azomycin and
chloramphenicol, giving rise to a plausible approach for a series
of pro-drug molecules, thus opening new research avenues
with high synthetic and biological impact.
It is well-known that hydrazine hydrate produces harmless
side products such as nitrogen and water under photo-
irradiation.19 Thus, for examining the possibility of decom-
position, we performed a set of photoreductions using
methylhydrazine and phenylhydrazine, accordingly. In the
former, a significant amount of methane was measured using a
gas chromatography−thermal conductivity detector (GC−
TCD) (Scheme S5); however, in the presence of phenyl-
1
hydrazine, a significant amount of benzene was verified by H
NMR spectroscopy during the photochemical reduction of 1
into 1a (Scheme S6). Moreover, the corresponding hydrazone
of formaldehyde, a decomposition product of methylhydrazine,
1
was identified in the reaction mixture by H NMR spectros-
copy (Figure S2).19a These results indicate the presence of a
radical degradation process of the methylhydrazine in the
presence or absence of the nitroarene,17,20 and support further
the necessity of methylhydrazine molar excess based on
nitroarene amount.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c01367.
■
sı
Based on these experimental data, we envisage a plausible
mechanistic pathway shown in Scheme 4. The first step
General procedures, mechanistic studies, and NMR
spectra (PDF)
Scheme 4. Plausible Mechanism for the Photoinduced
Synthesis of N-Phenylhydroxylamine from Nitrobenzene
AUTHOR INFORMATION
Corresponding Authors
■
Michael G. Kallitsakis − Department of Chemistry, Aristotle
University of Thessaloniki, Thessaloniki 54124, Greece;
Email: kallitsos29@gmail.com
Ioannis N. Lykakis − Department of Chemistry, Aristotle
University of Thessaloniki, Thessaloniki 54124, Greece;
orcid.org/0000-0001-8165-5604; Email: lykakis@
chem.auth.gr
Authors
Dimitris I. Ioannou − Department of Chemistry, Aristotle
University of Thessaloniki, Thessaloniki 54124, Greece
Michael A. Terzidis − Department of Nutritional Sciences &
Dietetics, International Hellenic University, 57400 Thessaloniki,
Greece
George E. Kostakis − Department of Chemistry, School of Life
Sciences, University of Sussex, Brighton BN1 9QJ, U.K.;
orcid.org/0000-0002-4316-4369
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c01367
Notes
The authors declare no competing financial interest.
involves the excitation of nitrobenzene (PhNO2*), followed by
a PCET or HAT pathway, between PhNO2* and methylhy-
−
ACKNOWLEDGMENTS
̇
̇
drazine, to give PhNO2H and PhNO2 radicals in an
equilibrium form. Preliminarily kinetic studies performed in
■
M.G.K. acknowledges the State Scholarships Foundation
(ΙΚΥ) for financial support through the Operational Program
“Human Resources Development, Education and Lifelong
Learning” in the context of the project “Reinforcement of
Postdoctoral Researchers -2nd Cycle” (MIS-5033021). The
authors acknowledge financial support from the Hellenic
1
CD3CN and monitored directly by H NMR, showed a faster
reduction for the electron-withdrawing substituted nitroarene
(4-MeOOC, 10) against the electron-donating substituted
nitroarenes (4-Me, 1 and 4-MeO, 6) (Figures S3−S5). This
result may support the formation of the above-proposed
D
https://dx.doi.org/10.1021/acs.orglett.0c01367
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
6, 54−65. (d) Fountoulaki, S.; Daikopoulou, V.; Gkizis, P. L.;
Tamiolakis, I.; Armatas, G. S.; Lykakis, I. N. ACS Catal. 2014, 4,
3504−3511. (e) Gkizis, P. L.; Stratakis, M.; Lykakis, I. N. Catal.
Commun. 2013, 36, 48−51.
(10) (a) Kallitsakis, M.; Loukopoulos, E.; Abdul-Sada, A.; Tizzard,
G. J.; Coles, S. J.; Kostakis, G. E.; Lykakis, I. N. Adv. Synth. Catal.
2017, 359, 138−145. (b) Andreou, D.; Kallitsakis, M. G.;
Loukopoulos, E.; Gabriel, C.; Kostakis, G. E.; Lykakis, I. N. J. Org.
Chem. 2018, 83, 2104−2113.
(11) (a) Tzirakis, M. D.; Lykakis, I. N.; Orfanopoulos, M. Chem. Soc.
Rev. 2009, 38, 2609−2621. (b) Symeonidis, T. S.; Athanasoulis, A.;
Ishii, R.; Uozumi, Y.; Yamada, Y. M. A.; Lykakis, I. N.
ChemPhotoChem. 2017, 1, 479−484.
Foundation for Research and Innovation (HFRI) and the
General Secretariat for Research and Technology (GSRT)
under Grant Agreement No. [776] “PhotoDaLu” (KA97507).
We thank Prof. K. S. Triantafyllidis (Department of Chemistry,
AUTH) for performing the GC−TCD experiments. We thank
Dr. C. Gabriel (HERACLES Research Center, KEDEK,
Laboratory of Environmental Engineering (EnvE-Lab),
Department of Chemical Engineering, AUTH, Greece) for
performing and analyzing the HRMS experiments. I.N.L.
acknowledges the Empirikeion Foundation for financial
support of the photoapparatus.
(12) (a) Kaneko, C.; Yamada, S.; Yokoe, I.; Hata, N.; Ubukata, Y.
Tetrahedron Lett. 1966, 7, 4729−4733. (b) Hashimoto, S.; Sunamoto,
J.; Fujii, H.; Kano, K. Bull. Chem. Soc. Jpn. 1968, 41, 1249−1251.
(c) Hashimoto, S.; Kano, K. Tetrahedron Lett. 1970, 11, 3509−3512.
(d) Hashimoto, S.; Kano, K. Bull. Chem. Soc. Jpn. 1972, 45, 549−553.
(13) A further set of experiments with electron-withdrawing and
electron-donating substituted nitroarenes was performed in MeOH
and MeCN, and the results are summarized in Tables S4−S8.
(14) (a) Marin, M.; Miranda, M. A.; Marin, M. L. Catal. Sci. Technol.
2017, 7, 4852−4858. (b) Sakamoto, H.; Imai, J.; Shiraishi, Y.; Tanaka,
S.; Ichikawa, S.; Hirai, T. ACS Catal. 2017, 7, 5194−5201.
(15) (a) Kumar, P. Pharmacology and Therapeutics for Dentistry, 7th
ed.; Elsevier, 2017, 457−487. (b) Qu, Y.; Spain, J. C. Environ.
Microbiol. 2011, 13, 1010−1017. (c) Singh, R.; Manjunatha, U.;
Boshoff, H. I.; Ha, Y. H.; Niyomrattanakit, P.; Ledwidge, R.; Dowd,
C. S.; Lee, I. Y.; Kim, P.; Zhang, L.; Kang, S.; Keller, T. H.; Jiricek, J.;
Barry, C. E., 3rd Science 2008, 322, 1392−1395.
(16) (a) McClelland, R. A.; Panicucci, R.; Rauth, A. M. J. Am. Chem.
Soc. 1987, 109, 4308. (b) Corbett, M. D.; Chipko, B. R. Antimicrob.
Agents Chemother. 1978, 13, 193−198. (c) Lu, H.; Chanco, E.; Zhao,
H. Tetrahedron 2012, 68, 7651−7654. (d) Jakubec, P.; Urbanova, V.;
Medrikova, Z.; Zboril, R. Chem. - Eur. J. 2016, 22, 14279−14284.
(17) Selected reports on the photochemistry of nitroarenes:
(a) Wubbels, G. G.; Snyder, E. J.; Coughlin, E. B. J. Am. Chem. Soc.
REFERENCES
■
(1) The Chemistry of Hydroxylamines, Oximes and Hydroxamic Acids;
Rappoport, Z., Liebman, J. F.; John Wiley & Sons, Ltd., 2009.
(2) (a) Boymans, E. H.; Witte, P. T.; Vogt, D. Catal. Sci. Technol.
2015, 5, 176−183. (b) Rong, Z.; Du, W.; Wang, Y.; Lu, L. Chem.
Commun. 2010, 46, 1559−1561. (c) Takenaka, Y.; Kiyosu, T.; Choi,
J.-C.; Sakakura, T.; Yasuda, H. Green Chem. 2009, 11, 1385−1390.
(3) (a) Doherty, S.; Knight, J. G.; Backhouse, T.; Summers, R. J.;
Abood, E.; Simpson, W.; Paget, W.; Bourne, R. A.; Chamberlain, T.
W.; Stones, R.; Lovelock, K. R. J.; Seymour, J. M.; Isaacs, M. A.;
Hardacre, C.; Daly, Η.; Rees, N. H. ACS Catal. 2019, 9, 4777−4791.
(b) Prakash, P.; De Masi, D.; Geertsen, V.; Miserque, F.; Li, H.;
Namboothiri, I. N. N.; Gravel, E.; Doris, E. Chemistry Select 2017, 2,
5891−5894. (c) Jawale, D. V.; Gravel, E.; Boudet, C.; Shah, N.;
Geertsen, V.; Li, H.; Namboothiri, I. N. Ν.; Doris, E. Chem. Commun.
2015, 51, 1739−1742. (d) Hojczyk, K. N.; Feng, P.; Zhan, C.; Ngai,
M.-Y. Angew. Chem., Int. Ed. 2014, 53, 14559−14563. (e) Shil, A. K.;
Das, P. Green Chem. 2013, 15, 3421−3428.
(4) (a) Kou, J.; Lu, C.; Wang, J.; Chen, Y.; Xu, Z.; Varma, R. S.
Chem. Rev. 2017, 117, 1445−1514. (b) Capaldo, L.; Ravelli, D. Eur. J.
Org. Chem. 2017, 2017, 2056−2071. (c) Friedmann, D.; Hakki, A.;
Kim, H.; Choi, W.; Bahnemann, D. Green Chem. 2016, 18, 5391−
5411.
(5) (a) Nabid, M. R.; Nazaru, N.; Asadi, S.; Heravi, M. M.; Sedghi,
R. Curr. Org. Chem. 2016, 20, 696−734. (b) Kadam, H. K.; Tilve, S.
G. RSC Adv. 2015, 5, 83391−83407.
(6) Recent photocatalytic hydrogenation processes: (a) Hao, C.-H.;
Guo, X.-N.; Sankar, M.; Yang, H.; Ma, B.; Zhang, Y.; Tong, X.; Jin, G.;
Guo, X.-Y. ACS Appl. Mater. Interfaces 2018, 10, 23029−23036.
(b) Yu, Z.; Chen, Z.; Chen, Y.; Peng, Q.; Lin, R.; Wang, Y.; Shen, R.;
Cao, X.; Zhuang, Z.; Li, Y. Nano Res. 2018, 11, 3730−3738.
(7) Recent photocatalytic transfer hydrogenation processes:
(a) Amanchi, S. R.; Kumar, K. V. A.; Lakshminarayana, B.;
Satyanarayana, G.; Subrahmanyam, C. New J. Chem. 2019, 43,
748−754. (b) Todorov, A. R.; Aikonen, S.; Muuronen, M.; Helaja, J.
Org. Lett. 2019, 21, 3764−3768. (c) Piggott, E. K.; Hope, T. O.;
Crabbe, B. W.; Jalbert, P.-M.; Orlova, G.; Hallett-Tapley, G. L. Catal.
Sci. Technol. 2017, 7, 5758−5765. (d) Xiao, Q.; Sarina, S.; Waclawik,
E. R.; Jia, J.; Chang, J.; Riches, J. D.; Wu, H.; Zheng, Z.; Zhu, H. ACS
Catal. 2016, 6, 1744−1753. (e) Tsutsumi, K.; Uchikawa, F.; Sakai, K.;
Tabata, K. ACS Catal. 2016, 6, 4394−4398. (f) Yang, X.-Y.; Chen, B.;
Zheng, L.-Q.; Wu, L.-Z.; Tung, C.-H. Green Chem. 2014, 16, 1082−
1086.
̈
1988, 110, 2543−2548. (b) Dopp, D.; Topics, D. Top. Curr. Chem.
1975, 55, 49−85. (c) Frolov, A. N.; Kuznetsova, N. A.; Eltsov, A. V.
Russ. Chem. Rev. 1976, 45, 1024−1034. (d) Cu, A.; Testa, A. C. J. Am.
Chem. Soc. 1974, 96, 1963−1965. (e) Barltrop, J. A.; Bunce, N. J.;
Thomson, A. J. Chem. Soc. C 1968, 1467−1474. (f) Hurley, R.; Testa,
A. C. J. Am. Chem. Soc. 1966, 88, 4330−4332.
(18) (a) Steudel, E.; Posdorfer, J.; Schindler, R. N. Electrochim. Acta
1995, 40, 1587−1594. (b) Huang, Y.; Lessard, J. Electroanalysis 2016,
28, 2716−2727.
(19) Selected reports on the photochemical decomposition of
hydrazine: (a) Lambert, C. E.; Shank, R. C. Carcinogenesis 1988, 9,
65−70. (d) Hawkins, W. G.; Houston, P. L. J. Phys. Chem. 1982, 86,
704−709. (g) Arvis, M.; Devillers, C.; Gillois, M.; Curtat, M. J. Phys.
Chem. 1974, 78, 1356−1360. (h) Stief, L. J.; DeCarlo, V. J. J. Chem.
Phys. 1966, 44, 4638−4639.
(20) King, D. M.; Bard, A. J. J. Am. Chem. Soc. 1965, 87, 419−423.
(8) (a) Chen, G.-J.; Xin, W.-L.; Wang, J.-S.; Cheng, J.-Y.; Dong, Y.-
B. Chem. Commun. 2019, 55, 3586−3589. (b) Mondal, B.; Mukherjee,
P. S. J. Am. Chem. Soc. 2018, 140, 12592−12601. (c) Xu, Y.; Chen, Y.;
Fu, W.-F. ACS Omega 2018, 3, 1904−1911. (d) Chaiseeda, K.;
Nishimura, S.; Ebitani, K. ACS Omega 2017, 2, 7066−7070. (e) Guo,
X.; Hao, C.; Jin, G.; Zhu, H.-Y.; Guo, X.-Y. Angew. Chem., Int. Ed.
2014, 53, 1973−1977. (f) Zhu, H.; Ke, X.; Yang, X.; Sarina, S.; Liu, H.
Angew. Chem., Int. Ed. 2010, 49, 9657−9661.
(9) (a) Iordanidou, D.; Zarganes-Tzitzikas, T.; Neochoritis, C. G.;
̈
Domling, A.; Lykakis, I. N. ACS Omega 2018, 3, 16005−16013.
(b) Papadas, I. T.; Fountoulaki, S.; Lykakis, I. N.; Armatas, G. S.
Chem. - Eur. J. 2016, 22, 4600−4607. (c) Andreou, D.; Iordanidou,
D.; Tamiolakis, I.; Armatas, G. S.; Lykakis, I. N. Nanomaterials 2016,
E
https://dx.doi.org/10.1021/acs.orglett.0c01367
Org. Lett. XXXX, XXX, XXX−XXX