Electrochemically induced synthesis of quinazolinonesviacathode hydration ofo-aminobenzonitriles in aqueous solutions

Article abstract of DOI:10.1039/d0ob02286a

An efficient and practical electrochemically catalyzed transition metal-free process for the synthesis of substituted quinazolinones from simple and readily availableo-aminobenzonitriles and aldehydes in water has been accomplished. I₂/base and water play an unprecedented and vital role in the reaction. By electrochemically catalysed hydrolysis ofo-aminobenzonitriles, the synthesis of quinazolinones with benzaldehyde was first proposed. The synthetic utility of this method was demonstrated by gram-scale operation, as well as the preparation of bioactiveN-(2,5-dichlorophenyl)-6-(2,2,2-trifluoroethoxy) pteridin-4-amine, which enables straightforward, practical and environmentally benign quinazolinone formation.

Full text of DOI:10.1039/d0ob02286a

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Electrochemically induced synthesis of
quinazolinones via cathode hydration of
o-aminobenzonitriles in aqueous solutions†
Cite this: Org. Biomol. Chem., 2021,
19, 998
Received 17th November 2020,
Accepted 22nd December 2020
Li Yang,a Huiqing Hou,b Lan Li,a Jin Wang,b Sunying Zhou,b Mei Wub and
a,b
DOI: 10.1039/d0ob02286a
Fang Ke
*
rsc.li/obc
An efficient and practical electrochemically catalyzed transition of o-aminoarylamides with a CO source and aryl halides
metal-free process for the synthesis of substituted quinazolinones (Scheme 2 path b).7 In addition, the coupling reactions of tran-
from simple and readily available o-aminobenzonitriles and alde- sition-metal-catalyzed o-haloarylamides with a nitrogen source
hydes in water has been accomplished. I2/base and water play an of amides or aldehydes as well as other annulation reactions
unprecedented and vital role in the reaction. By electrochemically have also received much attention recently (Scheme 2, path c).8
catalysed hydrolysis of o-aminobenzonitriles, the synthesis of qui- Similarly, the reactions of alcohols with o-animoarylamides are
nazolinones with benzaldehyde was first proposed. The synthetic also described (Scheme 2, path d).9 Recently, Huang and co-
utility of this method was demonstrated by gram-scale operation, workers have reported a series of synthesis strategies of
as well as the preparation of bioactive N-(2,5-dichlorophenyl)-6- N-heterocyclic compounds from benzyl ethers and o-amino-
(2,2,2-trifluoroethoxy) pteridin-4-amine, which enables straight- benzamides9d or alcohols and o-substituted anilines by electro-
forward, practical and environmentally benign quinazolinone chemical
oxidative
cyclization.10
Although
various
formation.
N-heterocyclic compounds, especially quinazolinones and
derivatives, can be obtained by the above methods, many still
have inherent drawbacks that are difficult to overcome. The
disadvantages of most methods include the use of volatile
organic solvents, harsh reaction conditions, toxic catalysts
(KMnO4, DDQ, MnO2, etc.), difficulty in product isolation, and
low product yields.11 Furthermore, some require transition
metal catalysts/ligands that can lead to metal residue contami-
nants in the products and limit their applications in drug syn-
thesis and can lead to the production of large amounts of
waste.1b,c,12 Therefore, developing direct, efficient, atom-econ-
omical and transition metal- and waste-free methods that can
employ greener substrates is still of great importance in the
field.
Quinazolinones are significant structural motifs due to their
widespread occurrence in natural products and synthetic phar-
maceuticals.1 In particular, they are used as privileged
scaffolds in drug discovery and are well known for their broad
range of biological activities such as anti-malarial, anti-hyper-
tensive, diuretic, anti-inflammatory, anticonvulsant and anti-
cancer activities.2 In recent years, numerous quinazolinone
embedded natural products have been identified.3 The cyto-
toxic alkaloid luotonin A and its derivatives infused with a qui-
nazolinone moiety are clinically proven as anti-cancer agents
(Scheme 1).4 Based on the wide range of applications of quina-
zolinones and their analogues, many pathways for the syn-
thesis of this similar structured compound have been
described.5
On the other hand, there is a large number of o-aryl benza-
mides on the market that are typically obtained from the
The most classical and general protocols for the synthesis
of quinazolinones are still performed through condensation
between o-aminobenzamides and aldehydes followed by the
oxidation of the resulting aminal intermediates (Scheme 2
path a).6 Other strategies include the carbonylative annulation
aCollege of Chemistry & Chemical Engineering, Yibin University, Yibin, Sichuan,
China
bFujian Medical University, Fuzhou, Fujian, China
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
d0ob02286a
Scheme 1 Selected examples of biologically active quinazolinone
derivatives.
998 | Org. Biomol. Chem., 2021, 19, 998–1003
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I2 with a low dose.21 For example, recently, the Chang group
has developed a one-pot I2-mediated annulation reaction of
substrates containing diamino groups and aldehydes via oxi-
dative C–N bond formation.21a Thus, the present method rep-
resents substantial improvements over the earlier reported
methods from the green and sustainable chemistry point of
view.
We started the research by investigating the model reaction
of o-aminobenzonitrile (1a) and benzaldehyde (2a) (Table 1).
Various parameters, such as the nature of the bases, the type
of solvents, reaction time and so on, were screened in order to
optimise the reaction conditions. The reaction was initially
carried out in a mixture of acetonitrile and water with different
oxidants using NaOH (2 mmol) as the base and Pt as the elec-
trode under an 80 mA current (Table 1, entries 1–3). The
results showed that, with the change of the oxidant action, the
Scheme 2 General methods for the synthesis of quinazolinones.
hydrolysis of o-aryl benzonitriles. However, the direct synthesis yield of product 3aa could be decreased accordingly, with I2
of quinazolinones from o-aryl benzonitrile has been rarely giving the highest yield of 3aa (Table 1, entry 1). The nature of
reported.13 Hence, the construction of the quinazolinone skel- the base used for the reaction was found to have much influ-
eton has aroused much interest employing o-aminobenzoni- ence on the yield (Table 1, entries 4 and 5). Further evaluation
triles as the starting substrates, and several catalytic methods of solvents revealed that water as the solvent was the best and
have been reported.14–16 Recently, Li16 has described
[Cp*IrCl2]2-catalyzed one-pot two-step sequential selective addition, when the time of reaction was halved, the yield of
hydration/condensation/acceptorless dehydrogenation of 3aa was reduced to 73% (Table 1, entry 8). The increase in
a
environment friendly choice (Table 1, entries 6 and 7). In
o-aminobenzonitriles and aldehydes to quinazolinones. time did not have much effect on the product (Table 1, entry
However, excess amounts of n-butylaldoxime and aldehydes 9). Subsequently, the investigation of different electrodes
were required. We were therefore inspired to develop a more showed that platinum plate electrodes were the best choice for
direct and environmentally friendly method for the prepa- both anode and cathode (Table 1, entries 10 and 11). Lower
ration of quinazolinones from o-aryl benzonitrile.
reaction yields were obtained when the current was halved or
From the perspective of green chemistry, electrochemically in its absence (Table 1, entries 12 and 13). It is worth noting
induced catalysis has gained significant interest in organic that changing the constant current has a significant impact on
synthesis due to its environment-friendliness, mild conditions, the reaction.
and low-energy consumption.17 Due to the atom economy of
electrochemical catalysis, we applied electrochemistry to the
synthesis of quinazolinones from o-aminobenzonitriles as
starting materials. We are pleased that the attempt at the elec-
trocatalysis of o-aminobenzonitrile and benzaldehyde has
yielded a satisfactory combination.
Table 1 Optimization of the reaction conditionsa
Moreover, owing to the increasing environmental concerns,
water as reaction medium is generally considered as a cheap,
safe, and environmentally benign alternative to non-natural
solvents.18 From both synthetic and environmental points of
views, the development of efficient homogeneous catalytic
systems for the acceptorless hydration of nitriles to the corres-
ponding primary amides to nitrogen-containing heterocycles
in water is apparently highly desirable.
As part of our ongoing research program toward the devel-
opment of economically sustainable green synthetic method-
ologies,19 herein, we demonstrate that I2/base could be used as
an efficient catalytic system for one-pot novel electrochemically
induced tandem reaction leading to quinazolinones from
o-aminobenzonitriles as starting materials. Iodine has been
shown to be more low-cost and more in line with the concept
of green chemistry than several metal catalysts.20 Recently,
some strategies have shown good activity with a heterogeneous
catalyst for the synthesis of quinazolinones in the presence of
Entry
Variations from the standard conditions
Yieldb (%)
1
2
3
4
None
CuI instead of I2
KI instead of I2
90
23
68
75
72
86
79
73
90
54
77
67
Trace
KOH instead of NaOH
Cs2CO3 instead of NaOH
DMSO/H2O (1/2) instead of H2O 3 mL
THF/H2O (1/2) instead of H2O 3 mL
6 h instead of 12 h
24 h instead of 12 h
C (−) instead of Pt (−)
C (+) instead of Pt (+)
40 mA instead of 80 mA
No electric current
5
6c
7d
8
9
10
11
12
13
a Standard conditions: 1a (0.7 mmol), 2a (0.5 mmol), I2 (0.2 mmol),
NaOH (2 mmol), undivided cell, Pt anode (1 cm × 1 cm), Pt cathode
(1 cm × 1 cm), constant current (80 mA), H2O (3 mL), r.t., 12 h.
b Isolated yield. c DMSO/H2O (1/2) = 3 mL. d THF/H2O (1/2) = 3 mL.
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Having the optimized reaction conditions in hand, we eval-
To explore the generality of this protocol, different o-amino-
uated the substrate scope of the reaction. Various benzal- benzonitrile derivatives were tested, and the results are sum-
dehydes (2a) were used as substrates to react with o-aminoben- marized in Table 2. Alkyl-substituted and halogenated amino-
zonitriles (1a), and the results are summarized. The results benzamides gave the corresponding quinazolinones with mod-
listed in Table 2 demonstrate that several of the benzaldehydes erate to high yields (Table 2, 3am–3ax). Similarly, electron-
tested underwent smooth transformation to afford the corres- donating group-substituted o-aminobenzonitriles showed rela-
ponding quinazolinones in high yields. In general, aldehydes tively higher catalytic activity compared with electron-with-
bearing electron-donating groups on the benzene ring were drawing group substituted ones. As shown in Table 2, the
more reactive than those with electron-withdrawing groups benzonitriles 1a with electron-donating substituents such as
(Table 2, 3aa–3al). This may be related to the fact that the pres- –OMe and –Me reacted with benzaldehyde smoothly to convert
ence of electron-donor groups makes the intermediate more the corresponding quinazolinones in 88% and 86% yields,
stable. Benzaldehydes bearing electronically activating substi- respectively (Table 2, 3am and 3av). Under the action of
tuents such as –OMe, –OH and –Me could be coupled with halogen electron-withdrawing groups such as –Cl and –Br,
o-aminobenzonitriles to give excellent yields of 91%, 88% and yields of 78% and 81% were obtained, respectively (Table 2,
90%, respectively (Table 2, 3ad, 3af and 3ai). Halogen-substi- 3ap and 3aq). In addition, the strong electron-withdrawing
tuted (–F, –Cl, and –Br) benzaldehydes (Table 2, 3ab–3ae) were group –NO2 caused a large decrease in the yield of 79% and
well tolerated. Moreover, thiophene-2-formaldehyde (Table 2, 76% (Table 2, 3ao and 3ar). Gratifyingly, pteridine compounds
3ak) and pyridine-3-formaldehyde (Table 2, 3al) were also suit- were also proven compatible with this method, providing 3aw
able for the construction of quinazolines in 72% and 75% and 3ax in decent yields.
yields, respectively. Furthermore, inert aliphatic aldehydes
We then scaled up the reaction, and the scalability of this
such as benzene acetaldehyde and hexanal were converted amination of benzaldehyde and o-aminobenzonitrile was eval-
with reasonably good yields of 81% and 69%, respectively uated by performing a gram-scale synthesis of 2-phenylquina-
(Table 2, 3aj and 3ay).
zolin-4(3H)-one. O-Aminobenzonitriles (7 mmol) and benzal-
dehydes (5 mmol) smoothly furnished the desired products in
81% yield (0.90 g).
To shed light on the reaction mechanism, some preliminary
mechanistic studies were carried out. Control reactions were
then performed to probe the reaction mechanism and the role
of current in the reaction. Firstly, o-aminobenzonitrile 1a effec-
tively afforded o-aminobenzamide 4a by hydration in the pres-
ence of NaOH (Scheme 3a). In the absence of current, the
amount of 4a produced by nitrile hydrolysis would decrease
(Scheme 3b). In order to confirm the involvement of current in
the reaction, we removed the current from the reaction system.
The amount of either 1a and 2a generated or the amount of
3aa generated by the direct reaction of 5aa decreased dramati-
cally (Scheme 3c and d). Subsequently, 5aa under the 80 mA
circuit conditions provided the expected product 3aa
(Scheme 3e). This suggested that the condensation of 1a and
2a or 5aa can readily take place to give the product 3aa, but
current is the key to obtain high yield. Under the protection of
nitrogen, the yield of product 3aa did not change greatly, indi-
cating that oxygen did not play a big role in this reaction
(Scheme 3f). The intermediate 6aa was oxidized under the
standard reaction conditions to afford the desired product 3aa
after 12 h which supported the involvement of dihydroquina-
zolinone in the proposed mechanistic cycle (Scheme 3g).
The reaction was then examined by cyclic voltammetry (CV)
(Fig. 1). Using a glass electrode as the working electrode, plati-
num wire as the opposite electrode, and a SCE as the reference
electrode, the scanning rate is 0.1 V s−1. An oxidation peak was
observed for the reaction of a mixture of 1a and NaOH at Ep =
+1.23 V, in the region of 0.0–2.0 V. In addition, a mixture of 1a,
2a and NaOH showed an oxidation peak at Ep = +1.23 V with a
slight increase of current (Fig. 1, curve b). These results indi-
cate that 1a reacts easily with 2a when it interacts with NaOH.
Table 2 Substrate scopea,b
a Standard conditions: 1a (0.7 mmol), 2a (0.5 mmol), I2 (0.2 mmol),
NaOH (2 mmol), undivided cell, Pt anode (1 cm × 1 cm), Pt cathode
(1 cm × 1 cm), constant current (80 mA), H2O (3 mL), r.t., 12 h.
b Isolated yield.
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Scheme 3 Control reactions.
Fig. 1 Cyclic voltammetry experiments were performed at room temp-
erature in a standard three electrode system.
It is noteworthy that the oxidation potential of the mixture of
1a, 2a and NaOH decreased from 1.23 V to 1.18 V in the pres-
ence of iodine (Fig. 2, curves b and c). It turns out that iodine
promotes further reactions of 1a, 2a, and NaOH.
On the basis of the above results and control experiments, a
plausible mechanism is proposed in Scheme 4. Firstly, o-ami-
nobenzonitriles A converted into B on the cathode via
hydration and NaOH.21 Then, B can readily react with C to
yield the imine D, which is converted to E in the presence of
the base, and then E oxidizes and dehydrogenates to afford the
desired product F, and iodide ions, under the action of the
anode along with the regeneration of iodine anions, to com-
plete the catalytic I− cycle.22a,23,24
Fig. 2 In vitro inhibitory data of target compounds against A549,
HCT-116 and SGC-7901 cell lines.
A pteridine compound is a kind of widely existing aromatic
compound, similar to quinazoline, which acts as an inhibitor
of tyrosine kinase and shows good specificity and inhibitory and the results are shown in Fig. 2. D3 inhibited human non-
activity on tumour cells. Secondly, the introduction of fluorine- small-cell Lung Carcinoma Cells A549, human colon cancer
containing substituents into drugs has been shown to increase cells HCT-116 and human gastric cancer cells SGC-7901
the anti-tumoural activity. Based on this, we applied this (which were all obtained from the Cell Bank of the Chinese
electrocatalytic system to the synthesis of Gefitinib analogues. Academy of Sciences) to different degrees. As shown in Fig. 2,
N-(2,5-Dichlorophenyl)-6-(2,2,2-trifluoroethoxy)pteridin-4-
amine (D3) was synthesized from 3-amino-6-(2,2,2-trifluor- HCT-116 cell lines with IC50 values ranging from 33.48 μmol
oethoxy)pyrazine-2-carbonitrile in
total yield of 60% L−1 to 154.8 μmol L−1, and the IC50 values of D3 in A549 and
(Scheme 5). The compounds were then used in MTT assay, SGC-7901 cell lines were less than those of gefitinib.
the results showed that D3 displayed inhibitory effects against
a
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number 12ZB166), National Natural Science Foundation of
China (grant number 21401163) and Fujian Provincial
Foundation (No. FJNMP-201902, 2019R1012-1).
Notes and references
1 (a) G. Bonola, P. Da Re, M. J. Magistretti, E. Massarani and
I. Setnikar, J. Med. Chem., 1968, 11, 1136–1139;
(b) S. M. A. H. Siddiki, K. Kon, A. S. Touchy and
K. Shimizu, Catal. Sci. Technol., 2014, 4, 1716–1719;
(c) D. V. Hase, R. V. Jayaram, K. Thirumalai and
M. Swaminathan, ChemistrySelect, 2019, 4, 3440–3445.
2 (a) M. Bakavoli, A. Shiri, Z. Ebrahimmpour and
M. Rahimizadeh, Chin. Chem. Lett., 2008, 19, 1403–1406;
(b) K. M. Khan, S. M. Saad, N. N. Shaikh, S. Hussain,
M. I. Fakhri, S. Perveen and M. I. Choudhary, Bioorg. Med.
Chem., 2014, 22, 3449–3454; (c) G. C. Pariyar, B. Mitra,
S. Mukherjee and P. Ghosh, ChemistrySelect, 2020, 5, 104–
108; (d) S. Das, S. Sinha, D. Samanta, R. Mondal and
G. Chakraborty, J. Org. Chem., 2019, 84, 10160–10171.
3 (a) N. Montazeri, K. Pourshamsian, S. Yosefiyan and
S. S. Momeni, J. Chem. Sci., 2012, 124, 883–887; (b) S. Maiti,
J. Kim, J.-H. Park, D. Nam, J. B. Lee, Y.-J. Kim, J.-M. Kee,
J. K. Seo, K. Myung, J.-U. Rohde, W. Choe, O.-H. Kwon and
S. Hong, J. Org. Chem., 2019, 84, 6737–6751; (c) F. Xie,
Q.-H. Chen, R. Xie, H.-F. Jiang and M. Zhang, ACS Catal.,
2018, 8, 5869–5874; (d) A. Cagir, S. H. Jones, R. Gao,
B. M. Eisenhauer and S. M. Hecht, J. Am. Chem. Soc., 2003,
125, 13628–13629.
Scheme 4 Mechanistic pathway.
Scheme 5 Synthesis
of
N-(2,5-dichlorophenyl)-6-(2,2,2-trifluor-
oethoxy)pteridin-4-amine (D3).
Conclusions
4 J. D. Palem, G. R. Alugubelli, R. Bantu, L. Nagarapu,
S. Polepalli, S. N. Jain, R. Bathini and V. Manga, Bioorg.
Med. Chem., 2016, 26, 3014–3018.
In summary, our team has developed a method for the one-pot
synthesis of quinazolinones by the electrocatalytic hydrolysis
of o-aminobenzonitrile and benzaldehyde for the first time.
Water not only promoted the hydrolysis of nitrile but also was
the solvent of the reaction system. Iodine-mediated non-metal
catalytic reaction has the advantages of high efficiency and low
energy consumption. A variety of substituted quinoline and
quinazolin-4(3H)-ones were synthesized using a low dose of
iodine as the catalyst from a variety of cheap and readily avail-
able starting precursors. Since a wide range of substrates can
be used to prepare substituted quinazolinones without con-
tamination by transition metal residues, this method may be
of potential application in pharmaceutical synthesis. Further
application of the electrochemical synthesis strategy in organic
synthesis is underway in our laboratory.
5 (a) F. Xie, Q. Chen, R. Xie, H. Jiang and M. Zhang, ACS
Catal., 2018, 8, 5869–5874; (b) J. Chen, K. Natte,
A. Spannenberg, H. Neumann, P. Langer, M. Beller and
X.-F. Wu, Angew. Chem., 2014, 126, 7709–7713; (c) X. Liu,
H. Fu, Y. Jiang and Y. Zhao, Angew. Chem., Int. Ed., 2009,
48, 348–351; (d) J. An, Y. Wang, Z. Zhang, Z. Zhao, J. Zhang
and F. Wang, Angew. Chem., Int. Ed., 2018, 57, 12308–
12312.
6 (a) R. J. Abdel-jalil, W. Voelter and M. Saeed, Tetrahedron
Lett., 2004, 45, 3475–3476; (b) D. Zhan, T. Li, H. Wei,
W. Weng, K. Ghandi and Q. Zeng, RSC Adv., 2013, 3, 9325–
9329; (c) S. R. Vemula, D. Kumar and G. R. Cook,
Tetrahedron Lett., 2018, 59, 3801–3805.
7 (a) S. You, B. Huang, T. Yan and M. Cai, J. Organomet.
Chem., 2018, 875, 35–45; (b) X. Jiang, T. Tang, J.-M. Wang,
Z. Chen, Y.-M. Zhu and S.-J. Ji, J. Org. Chem., 2014, 79,
5082–8057; (c) H. Li, L. He, H. Neumann, M. Beller and
X.-F. Wu, Green Chem., 2014, 16, 1336–1343.
Conflicts of interest
There are no conflicts to declare.
8 (a) L.-X. Wang, J.-F. Xiang and Y.-L. Tang, Eur. J. Org.
Chem., 2014, 2682–2685; (b) S. Guo, Y. Li, L. Tao, W. Zhang
and X. Fan, RSC Adv., 2014, 4, 59289–59296; (c) M. A. Iqbal,
L. Lu, H. Mehmood, D. M. Khan and R. Hua, ACS Omega,
2019, 4, 8207–8213; (d) N. Yan, C. You and M. Cai,
Acknowledgements
This work was partially supported by the Scientific Research
Project of Sichuan Province Education Department (grant
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J. Organomet. Chem., 2019, 897, 161–169; (e) F.-C. Jia,
Z.-W. Zhou, C. Xu, Q. Cai, D.-K. Li and A.-X. Wu, Org. Lett.,
2015, 17, 4236–4239; (f) K. Upadhyaya, R. K. Thakur,
S. K. Shukal and R. P. Tripathi, J. Org. Chem., 2016, 81,
5046–5055.
9 (a) J.-J. Zhong, W.-P. To, Y. Liu, W. Lu and C.-M. Che, Chem.
Sci., 2019, 10, 4883–4889; (b) L. Cao, H. Huo, H. Zeng,
Y. Yu, D. Lu and Y. Gong, Adv. Synth. Catal., 2018, 360,
4764–4773; (c) Z. Zhang, M. Wang, C. Zhang, Z. Zhang,
Z.-H. Wang, C. Zheng, B. Sun, Z.-H. Chen, S.-L. You and
T.-S. Mei, Angew. Chem., Int. Ed., 2020, 59, 15254–15259;
(c) D.-Z. Lin, Y.-L. Lai and J.-M. Huang, ChemElectroChem,
2019, 6, 4188–4193; (d) J. P. Barham and B. Konig, Angew.
Chem., Int. Ed., 2020, 59, 11732–11747; (e) H. Ding, K. Xu
and C.-C. Zeng, J. Catal., 2020, 381, 38–43; (f) K. Liu,
C. Song and A. Lei, Org. Biomol. Chem., 2018, 16, 2375–
2378; (g) A. M. F. Phillips and A. J. L. Pombeiro, Org.
Biomol. Chem., 2020, 18, 7026–7055.
J. Lu and F. Wang, Chem. Commun., 2015, 51, 9205–9207; 18 (a) S. Peng, D. Hu, J.-L. Hu, Y.-W. Lin, S.-S. Tang,
(d) D.-Z. Lin, Y.-L. Lai and J.-M. Huang, ChemElectroChem,
2019, 6, 4188–4193.
10 Y.-L. Lai, J.-S. Ye and J.-M. Huang, Chem. – Eur. J., 2016, 22,
5425–5429.
H.-S. Tang, J.-Y. He and W.-M. He, Adv. Synth. Catal., 2019,
361, 5721–5726; (b) L.-Y. Xie, S. Peng, F. Liu, Y.-F. Liu,
M. Sun, Z.-L. Tang, S. Jiang, Z. Cao and W.-M. He, ACS
Sustainable Chem. Eng., 2019, 7, 7193–7199.
11 (a) R. Cheng, T. Guo, D. Zhang-Negrerie, Y. Du and K. Zhao, 19 (a) F. Ke, Y. Xu, S. Zhu, X. Lin, C. Lin, S. Zhou and H. Su,
Synthesis, 2013, 45, 2298–3006; (b) A. Khorramabadi-Zad,
A. R. Oveisi and S. Daliran, RSC Adv., 2016, 2, 1136–1142;
(c) Y.-H. Shang, L.-Y. Fan, X.-X. Li and M.-X. Liu, Chin. Chem.
Lett., 2015, 26, 1355–1358; (d) B.-Q. Hu, J. Cui, L.-X. Wang,
Green Chem., 2019, 21, 4329–4333; (b) F. Ke, P. Zhang,
C. Lin, X. Lin, J. Xu and X. Zhou, Org. Biomol. Chem., 2018,
16, 8090–8094; (c) F. Ke, P. Zhang, Y. Xu, X. Lin, J. Lin,
C. Lin and J. Xu, Synlett, 2018, 29, 2722–2726.
Y.-L. Tang and L. Yang, RSC Adv., 2016, 6, 43950–43953; 20 (a) J. Sun, Y. Dong, L. Cao, X. Wang, S. Wang and Y. Hu,
(e) Y. Mitobe, S. Ito, T. Mizutani, T. Nagase, N. Sato and
S. Tokita, Bioorg. Med. Chem. Lett., 2009, 19, 4075–4078;
J. Org. Chem., 2004, 69, 8932–8934; (b) M. Breugst and
D. V. R. Heiden, Chem. – Eur. J., 2018, 24, 9187–9199.
(f) Y. Zheng, M. Bian, X.-Q. Deng, S.-B. Wang and 21 (a) X. Tian, L. Song, E. Li, Q. Wang, W. Yu and J. Chang,
Z.-S. Quan, Arch. Pharm. Chem. Life, 2013, 246, 119–126.
12 S. R. Vemula, D. Kumar and G. R. Cook, ACS Catal., 2016,
6, 5295–5301.
13 (a) Y. Hu, S. Li, H. Li, Y. Li, J. Li, C. Duanmu and B. Li, Org.
Chem. Front., 2019, 6, 2744–2748; (b) Q. Wang, M. Lv,
J. Liu, Y. Li, H. Cao, X. Zhang and Q. Xu, ChemSusChem,
RSC Adv., 2015, 5, 62194–62201; (b) X. Tuo, S. Chen,
P. Jiang, P. Mi, X. Wang and G.-J. Deng, RSC Adv., 2020, 10,
8348–8351; (c) M. Sharif, J. Opalach, P. Langer, M. Beller
and X.-F. Wu, RSC Adv., 2014, 4, 8–17; (d) J. Gonzalez-
Garcia, L. Drouin, C. E. Banks, B. Sljukic and
R. G. Compton, Ultrason. Sonochem., 2007, 14, 113–116.
2019, 12, 3043–3048; (c) W. Zhao, P. Liu and F. Li, 22 (a) Y. Hu, S. Li, H. Li, Y. Li, J. Lin, C. Duanmu and B. Li,
ChemCatChem, 2016, 8, 1523–1530.
14 Y. Hu, S. Li, H. Li, Y. Li, J. Li, C. Duanmu and B. Li, Org.
Chem. Front., 2019, 6, 2744–2748.
Org. Chem. Front., 2019, 6, 2744–2748; (b) Q. Wang, M. Lv,
J. Liu, Y. Lo, H. Cao, X. Zhang and Q. Xu, ChemSusChem,
2019, 12, 3043–3048.
15 X.-F. Wu, S. Oschatz, A. Block, A. Spannenbery and 23 M. Kumar, Richa, S. Sharma, V. Bhatt and N. Kumar, Adv.
P. Langer, Org. Biomol. Chem., 2014, 12, 1865–1870. Synth. Catal., 2015, 357, 2862–2868.
16 W. Zhao, P. Liu and F. Li, ChemCatChem, 2016, 8, 1523– 24 (a) Y. Li, C.-C. Sun and C.-C. Zeng, J. Electroanal. Chem.,
1530.
2020, 861, 113941–113947; (b) P. Qian, Z. Zha and Z. Wang,
ChemElectroChem, 2020, 7, 2527–2544; (c) K. Klyokawa and
S. Minakata, Synlett, 2020, 31, 845–855.
17 (a) Y. Wu, H. Ding, M. Zhao, Z.-H. Ni and J. P. Cao, Green
Chem., 2020, 22, 4906–4911; (b) P.-S. Gao, X.-J. Weng,
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