Green and convenient protocols for the efficient reduction of nitriles and nitro compounds to corresponding amines with NaBH4 in water catalyzed by magnetically retrievable CuFe2O4 nanoparticles

Article abstract of DOI:10.1007/s11164-019-03794-4

Abstract: In this study, firstly, CuFe₂O₄ nanoparticles were prepared by a simple operation. The structure of the mentioned nanoparticles was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-optical emission spectrometry, vibrating sample magnetometer and also Brunauer–Emmett–Teller and Barrett–Joyner–Halenda analyses. The prepared magnetically copper ferrite nanocomposite was successfully applied as a simple, cost-effective, practicable, and recoverable catalyst on the green, highly efficient, fast, base-free, and ligand-free reduction of nitriles and also on the affordable and eco-friendly reduction of nitro compounds with the broad substrate scope to the corresponding amines with NaBH₄ in water at reflux in high to excellent yields. Graphical abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s11164-019-03794-4

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-019-03794-4
Green and convenient protocols for the eꢀcient reduction
of nitriles and nitro compounds to corresponding amines
with NaBH in water catalyzed by magnetically retrievable
4
CuFe O nanoparticles
2
4
1
1
Behzad Zeynizadeh · Farkhondeh Mohammad Aminzadeh ·
Hossein Mousavi1
Received: 8 November 2018 / Accepted: 2 March 2019
©
Springer Nature B.V. 2019
Abstract
In this study, frstly, CuFe O nanoparticles were prepared by a simple operation.
2
4
The structure oꢀ the mentioned nanoparticles was characterized by Fourier trans-
ꢀ
orm inꢀrared spectroscopy, X-ray diꢁraction, scanning electron microscopy, trans-
mission electron microscopy, energy-dispersive X-ray spectroscopy, inductively
coupled plasma-optical emission spectrometry, vibrating sample magnetometer and
also Brunauer–Emmett–Teller and Barrett–Joyner–Halenda analyses. The prepared
magnetically copper ꢀerrite nanocomposite was successꢀully applied as a simple,
cost-eꢁective, practicable, and recoverable catalyst on the green, highly eꢂcient,
ꢀ
ast, base-ꢀree, and ligand-ꢀree reduction oꢀ nitriles and also on the aꢁordable and
eco-ꢀriendly reduction oꢀ nitro compounds with the broad substrate scope to the cor-
responding amines with NaBH in water at reꢃux in high to excellent yields.
4
Graphical abstract
Keywords CuFe O · Nanocatalyst · Reduction oꢀ nitrile and nitro · Amine ·
2
4
NaBH · Water · Green chemistry
4
*
Hossein Mousavi
Hossein.Mousavi@Gmail.Com
1
1
Department oꢀ Organic Chemistry, Faculty oꢀ Chemistry, Urmia University, Urmia, Iran
Vol.:(012
1
3456789)
3

B. Zeynizadeh et al.
Introduction
Amines are widely present in natural products, dyes, agrochemicals, photo-
graphic and rubber materials, biologically active compounds and pharmacophores
(
Scheme 1) [1–6]. They are also ꢀrequently used in organic synthesis (especially in
the heterocyclic compounds synthesis) as starting material [7–14], catalyst [15–20]
and also reaction solvent [21–23]. Among the numerous employed procedures ꢀor
the synthesis oꢀ amines, reduction oꢀ nitriles is an attractive and straightꢀorward
method ꢀor the preparation oꢀ primary amines. In this area, some reducing systems
such as LiAlH [24], NaBH /CoCl [25–27], NaBH /NiCl (Ni B) [28], NaBH /
4
4
2
4
4
2
2
4
4
InCl [29], NaBH /I [30], LiBH /i-Pr NBH [31], LiBH NMe [32], KBH /
3
4
3
2
2
2
2
3
2
2
Raney Ni [33], BH ·SMe [34], (MeO) BH/Ni B or Co B [35], Et SiH /B(C F )
2
2
2
2
6 5 3
[
36], PhSiH /ReIO (PPh ) [37], PhSiH /n-Bu NF [38], TMDS/Ti(OiPr) [39],
3 2 3 2 3 4 4
HCO K/Raney Ni/DBU-based ionic liquids [40], SmI /Et N/H O [41], electrolysis
2
2
2
3
2
with Raney Ni cathode [42], H /PtO /HOAc [43], H /Raney Ni/NaOAc [44], H /
2
2
2
2
Rh–Al O [45], H /Ni–SiO or Ni–SiO –Al O [46], H /RuCl (PPh ) [47, 48], H /
2
3
2
2
2
2
3
2
2
3 3
[
Ru(cod)methyallyl ]/PPh [47], H /[Ru(cod)methylallyl ]/DPPF [49], H /Fe-Pincer
2 3 2 2 2
complex [50], H /[Ru(cod)methylallyl ]/tridentate phosphine-type ligands [51], H /
2
2
2
(
0)
Ru-alkylidene catalysts [52], NaBH /Fe O @PAMAM/Ni -b-PEG [53], NaBH /
4
3
4
4
4
(II)
(0)
MWCNTs/Fe O @PCA/Pt
[54], NaBH /amorphous nickel powder (Ni )/
3
4
Scheme 1 Examples oꢀ some useꢀul chemical structure bearing amine ꢀunctional groups
1
3

Green and convenient protocols for the eꢀcient reduction…
NaOH [55], H /bench-stable cobalt/NaHBET [56], H N·BH /G-Cu Ni [57],
2
3
3
3
36 64
H /[Ru(cod)(2-methylallyl) ]/SlMesBF [58], NaBH /NiNPs@Fe O –SiO -P4VP
2
2
4
4
3
4
2
[
(
59], i-PrOH/B @CeO /aqueous NH [60], H /Pd-5% Au/Al O /AcOH [61], H /
12 2 3 2 2 3 2
Cp*Ru) (μ -H)(μ-H) (μ-CO) [62], H /[Ru(cod)Cl ]/NH OH [63], (EtO) MeSiH/
3
3
2
2
2
4
2
Fe(OAc) /phenanthroline ligand [64], H /Pd(PhCN) Cl /BQC/H O/HMS [65],
2
2
2
2
2
NaBH /CuNP/WS-1 [66], TMDS/Cu(OTꢀ) [67], NaBH /COF-supported Co/
4
2
4
Co(OH) NPs [68], NH BH /Pd–Cu /Fe O [69], NH BH /G-Ni Pd [70]
2
3
3
0.5
3
4
3
3
30
70
HCO H–N(CH CH ) /FS-NH –RhCu@mSiO [71], H /Pd-NPs [72] and also H /
2
2
3 3
2
2
2
2
nitrogen-doped mesoporous carbon supported nickel nanoparticles (MC/Ni) [73]
have been reported ꢀor the titled transꢀormation. Along with disadvantages such as
long reaction times, use oꢀ toxic solvent and so on, one oꢀ the important and main
problems oꢀ the reduction oꢀ nitriles (especially, when LiAlH or NaBH used as
4
4
reducing agent) is mixture production oꢀ primary, secondary and tertiary amines.
Thereꢀore, the design oꢀ convenient chemoselective protocols ꢀor the reduction oꢀ
nitriles to corresponding primary amines is very valuable.
On the other hand, another manner ꢀor the preparation oꢀ amines is a reduction
oꢀ nitro compounds. This manner has been paid a lot oꢀ attention compared with
the reduction oꢀ nitriles, and there are many reports about this method in the lit-
erature. Nevertheless, most oꢀ the methods to prepare amine ꢀrom the reduction oꢀ
nitro compounds are not suitable ꢀrom the green chemistry protocols and industrial
chemistry disciplines point oꢀ view. So, the development oꢀ new green protocols ꢀor
the reduction oꢀ the nitro ꢀunctional group is necessary.
With increasing environmental concerns, the development oꢀ chemical reactions
based on green chemistry protocols has a pivotal position in the organic synthetic
community. In this regard, the use oꢀ water as an inexpensive, non-toxic, non-ꢃam-
mable, readily available and also eco-ꢀriendly solvent is an excellent choice in the
organic synthesis [74–79].
Nowadays, the synthesis and applications oꢀ magnetic nanoparticles (MNPs)
because oꢀ their nanosize dimensions and huge surꢀace areas as well as high cata-
lytic activities have been receiving much attention in various sciences, especially in
the feld oꢀ catalytic systems [80, 81]. They can be easily separated ꢀrom the reaction
mixture on the basis oꢀ the magnetic property which leads to avoiding time-con-
suming separation steps. In this context, synthesis oꢀ the magnetically ꢀunctionalized
nanocomposites is also a subject oꢀ interest and has usually taken place based on
the synthesis oꢀ a magnetic core ꢀollowed by modifcation with various materials.
The literature survey shows that CuFe O MNPs with inverse spinel structure has
2
4
been used in pigments [82] and gas sensing [83, 84]. It is worthwhile to note that
CuFe O MNPs can be a very suitable option ꢀor use as a catalyst in various organic
2
4
transꢀormations because the mentioned nanocomposite has great advances due to
physiochemical properties oꢀ Cu species, eco-ꢀriendly nature, moisture insensitivity,
high stability up to 1000 °C, ꢀantastic magnetic susceptibility ꢀor easy separation
and reusability as well as high reactivity.
By taking into consideration all the points mentioned, and also in the continu-
ation oꢀ our research program on the design and use oꢀ new and eꢂcient cata-
lytic systems ꢀor the development oꢀ useꢀul synthetic protocols [85–88], we wish
to report valuable catalytic applications oꢀ CuFe O nanoparticles as a reusable
2
4
1
3

B. Zeynizadeh et al.
and cost-eꢁective catalyst ꢀor the green and eꢂcient reduction oꢀ nitriles and also
nitro compounds to corresponding amines with NaBH as a mild reducing agent
4
in water at reꢃux (Scheme 2).
Experimental
Reagents, samples, and apparatus
All reagents and substrates were purchased ꢀrom Merck, Fluka, and Sigma-
Aldrich chemical companies and used without ꢀurther purifcation. Inꢀrared spec-
tra were recorded on a Nexus 670 Thermo Nicolet Fourier Transꢀorm Inꢀrared
Spectrometer and measured as KBr discs. X-ray diꢁraction (XRD) measurements
were made on a Bruker D8-Advance diꢁractometer with graphite-monochroma-
tized Cu Kα radiation (λ = 1.54,056 Å) at room temperature. Scanning electron
microscopy (SEM) images were determined on an LEO 1430 VP scanning elec-
tron microscope. Transmission electron microscope (TEM) images were recorded
with a Philips CM30 at the electron energy oꢀ 300 keV. The amounts oꢀ Cu, Fe,
and O were measured by inductively coupled plasma-optical emission spectrom-
etry (ICP-OES, Varian 730-ES). Magnetic properties oꢀ the samples were deter-
mined using a vibration sample magnetometer (VSM; model MDKFT) under
magnetic felds up to 20 kOe. The N adsorption–desorption isotherm was tested
2
on BELSORP-mini II, BEL Japan Inc. The specifc surꢀace area oꢀ the sample
was measured by the Brunauer–Emmett–Teller (BET) technique and also the pore
volume and pore size distribution have resulted ꢀrom the desorption profle oꢀ the
isotherm using the Barrett–Joyner–Halenda (BJH) method. Melting points were
1
13
determined on an Electrothermal 9200 apparatus. H NMR and C NMR spectra
were recorded on a Bruker Avance 300 MHz spectrometer at 300 and 75 MHz,
respectively. Chemical shiꢀts were measured in CDCl as a solvent relative to
3
tetramethylsilane (TMS) as the internal standard. Thin-layer chromatography
(
TLC) was applied ꢀor the purity determination oꢀ substrates, products and reac-
tion monitoring over silica gel 60 F aluminum sheet.
2
54
Scheme 2 Green reduction oꢀ nitriles and nitro compounds to corresponding amines with NaBH cata-
4
lyzed by CuFe O MNPs
2
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Preparation of CuFe O MNPs
2
4
CuFe O nanoparticles were prepared according to the literature [83]. Firstly,
2
4
Cu(OAc) ·H O, Fe(NO ) ·9H O, NaOH, and NaCl were mixed in a molar ratio
2
2
3 3
2
1
:2:8:2 and ground together in a simple agate mortar and pestle ꢀor about 50 min. The
reaction started readily during the mixing process, which was accompanied by the
release oꢀ heat. As the reaction proceeded, the mixture became mushy and underwent
gradual changes in color ꢀrom blue (3 min) to fnally brown (10 min). The outcome
mixture was washed with deionized water several times. Aꢀter removal oꢀ sodium
chloride by washing, the powders were dried at 80 °C ꢀor 2 h. Then the powders were
calcinated at 300, 500, 600, 700, 800, 900 °C ꢀor 2 h to obtain CuFe O MNPs.
2
4
General procedure for the reduction of nitriles to primary amines
As a representative example, in a round-bottom ꢃask (15 mL) equipped with a
magnetic stirrer, benzonitrile (1 mmol, 0.103 g) was dissolved in H O (2 mL).
2
Aꢀterward, CuFe O (0.2 mmol, 0.048 g) was added and the mixture was stirred.
2
4
Then, NaBH (2 mmol, 0.076 g) was also added, and the resulting mixture con-
4
tinued to stir at reꢃux ꢀor 5 min. Upon completion oꢀ the reaction (monitored by
TLC), the mixture was cooled to room temperature, and the catalyst was separated
by an external magnet. The reaction mixture was extracted with ethyl acetate
(
EtOAc) (2 × 4 mL). The organic layers were combined together and dried over
anhydrous sodium sulꢀate (Na SO ). The solvent was evaporated under reduced
2
4
pressure. The pure colorless liquid benzylamine was obtained in 95% yield.
General procedure for the reduction of nitro compounds to amines
For example, in a round-bottom ꢃask (15 mL) equipped with a magnetic stirrer, a
mixture oꢀ nitrobenzene (1 mmol, 0.123 g) in H O (2 mL) was prepared. CuFe O
2
2
4
(
0.2 mmol, 0.048 g) was then added, and the mixture was stirred. At the next
step, NaBH (2 mmol, 0.076 g.) was added, and the resulting mixture continued
4
to stir at reꢃux ꢀor 50 min. Aꢀter completion oꢀ the reaction (monitored by TLC),
the mixture was cooled to room temperature, and the mentioned nanocatalyst was
separated by an external magnet. The reaction mixture was extracted with EtOAc
(
2 × 4 mL) and then dried over anhydrous Na SO . The solvent was evaporated
2 4
under reduced pressure to aꢁord the pure liquid aniline in 95% yield.
Results and discussion
Synthesis and characterization of CuFe O MNPs
2
4
The study was started by the synthesis oꢀ magnetic CuFe O nanoparti-
2
4
cles through the solid-state mechanochemical grinding oꢀ Cu(OAc) ·H O,
2
2
1
3

B. Zeynizadeh et al.
Fe(NO ) ·9H O, NaOH, and NaCl in a molar ratio 1:2:8:2 at room temperature
3
3
2
according to the literature [83]. The process is very eꢂcient and economic. The
prepared CuFe O MNPs was then well characterized by Fourier transꢀorm inꢀra-
2
4
red (FT-IR) spectroscopy, X-ray diꢁraction (XRD), scanning electron microscopy
(
SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX)
spectroscopy, inductively coupled plasma-optical emission spectrometry (ICP-
OES), vibrating sample magnetometer (VSM) and also BET-BJH analyses.
As shown in Fig. 1, in the FT-IR spectrum oꢀ CuFe O , two main absorption
2
4
−1
bands at 586.8 and 405.8 cm are attributed to stretching vibrations oꢀ Cu‒O bonds
in tetrahedral and octahedral sites oꢀ cubic spinel ꢀerrite. It is very important to note
that the stretching absorption band oꢀ Cu‒O in tetrahedral sites, because oꢀ the short
bond length oꢀ Cu‒O, that appeared at a higher wave number in comparison to octa-
hedral sites.
The recorded XRD spectrum ꢀor the CuFe O MNPs (Fig. 2) shows that all the
2
4
peaks in the spectrum matched well with the standard one oꢀ copper ꢀerrite in Joint
Committee on Powder Diꢁraction Standards (JCPDS) card no. 34-0425. The peaks
that appeared at 2θ=18.9°, 31.02°, 36.62°, 38.38°, 44.92°, 55.62°, 58.48°, and
6
2.19° were indexed to (111), (220), (311), (222), (400), (422), (511), and (440)
crystal planes oꢀ spinel ꢀerrite, respectively. The average crystal size obtained by the
Debye–Scherrer equation using intensive peak (311) was ꢀound to be 9 nm. In addi-
tion, the pattern represents that the nanomagnetic CuFe O has a cubic unit cell with
2
4
inverse spinel crystals.
The morphology and size distribution oꢀ CuFe O was also determined using
2
4
scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
Figures 3 and 4, respectively, represent the SEM and TEM images oꢀ the prepared
sample. According to these images, an irregular morphology was observed ꢀor the
nanocomposite. Also, based on the mentioned images the particles oꢀ CuFe O are
2
4
in the nanometric range.
Fig. 1 FT-IR spectrum oꢀ CuFe O MNPs
2
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Fig. 2 XRD spectrum oꢀ CuFe O MNPs
2
4
Fig. 3 SEM images oꢀ CuFe O MNPs
2
4
1
3

B. Zeynizadeh et al.
Fig. 4 TEM images oꢀ CuFe O MNPs
2
4
The elemental (Cu, Fe, and O) composition oꢀ CuFe O was determined by
2
4
energy dispersive X-ray spectroscopy (EDX). Figure 5 shows that all the titled ele-
ments are present in the nanocomposite. Through the inductively coupled plasma-
optical emission spectrometry (ICP-OES), the amounts oꢀ Cu, Fe, and O in CuFe O
2
4
MNPs were determined 22.52%, 46.71%, and 30.77%, respectively.
The magnetic property oꢀ CuFe O NPs was also investigated at room temper-
2
4
ature by vibrating sample magnetometer (VSM) analysis. The obtained saturation
−1
magnetization value (Ms=38 emu g ) and the shape oꢀ the illustrated pattern show
that the prepared sample has a ꢀerromagnetic characteristic ꢀor a good magnetic sep-
aration (Fig. 6).
N adsorption–desorption isotherms are used as a macroscopic average measure-
2
ment ꢀor exploring the surꢀace area, pore diameter, and pore volume oꢀ the material.
The N adsorption–desorption isotherm ꢀor ꢀerromagnetic CuFe O NPs is illus-
2
2
4
trated in Fig. 7. The specifc surꢀace area and pore volume value oꢀ the synthesized
2
−1
3
−1
copper ꢀerrite are 5.46 m g and 0.0077 cm g respectively (determined by the
1
3

Green and convenient protocols for the eꢀcient reduction…
Fig. 5 EDX spectrum oꢀ CuFe O MNPs
2
4
Fig. 6 VSM spectrum oꢀ CuFe O MNPs
2
4
1
3

B. Zeynizadeh et al.
Fig. 7 N adsorption–desorption isotherm ꢀor CuFe O MNPs
2
2
4
Brunauer–Emmett–Teller (BET) equation). As shown in Fig. 7, and based on the
IUPAC classifcation, it can be realized that the typical type III isotherm at low rela-
tive pressure ꢀor the synthesized CuFe O is obtained. This isotherm is specifc to
2
4
micropores material. On the other hand, the distribution oꢀ pore size on the Bar-
rett–Joyner–Halenda (BJH) analysis (1.88 nm) is also evident.
Reduction of nitriles to primary amines
During the past decades, sodium borohydride as a mild reducing agent has played a
prominent role in the reduction oꢀ various ꢀunctional groups in organic synthesis. In
spite oꢀ the great capabilities oꢀ this reducing agent, reduction oꢀ cyano group (nitrile)
with the alone NaBH does not take place under ordinary conditions. Thereꢀore, aꢀter
4
synthesis and characterization oꢀ CuFe O MNPs, the catalytic activity oꢀ the pre-
2
4
pared MNPs was studied on the reduction oꢀ benzonitrile (PhCN) to benzylamine
with NaBH under diꢁerent conditions including changing solvents, temperature and
4
also using the diꢁerent molar equivalents oꢀ reactant and catalyst. Table 1 presents
a summary oꢀ the results oꢀ these investigations. Entries 1–5 oꢀ Table 1 show that
reduction oꢀ PhCN with NaBH in the presence oꢀ CuFe O in the protic and aprotic
4
2
4
solvents such as MeOH, EtOH, EtOAc, tetrahydroꢀuran (THF) and also CH CN
3
did not take place even under drastic conditions. Interestingly, using H O as a sole
2
solvent dramatically accelerated the rate oꢀ the reduction process (Table 1, entries
6
–8). These observations revealed that H O was the best solvent oꢀ choice and using
2
a molar equivalent oꢀ 1:0.2:2 ꢀor PhCN, CuFe O , and NaBH respectively, was the
2
4
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 1 Optimization experiments ꢀor the reduction oꢀ benzonitrile to benzylamine with NaBH cata-
4
lyzed by CuFe O MNPs
2
4
Entrya
NaBH
CuFe O
Solvent
Condition
Time (min)
Conversion (%)
4
2
4
(
mmol)
(mmol)
1
2
3
4
5
6
7
8
0
3
3
3
2
2
2
2
2
2
2
2
1
1
1
1
MeOH
EtOH
EtOAc
THF
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
80 °C
r.t.
120
120
120
120
120
5
5
7
90
90
90
0
0
0
0
0
100
100
100
10
60
65
1
CH CN
3
0.5
0.2
0.2
0.2
0.1
0.1
H O
2
H O
2
H O
2
H O
2
1
0
H O
80 °C
Reꢃux
2
1
1
H O
2
aAll reactions were carried out with 1 mmol oꢀ benzonitrile in 2 mL oꢀ solvent
optimum ꢀor complete reduction oꢀ PhCN. Finally, benzylamine was obtained in 95%
isolated yield within 5 min at reꢃux (Table 1, entry 8).
The scope and generality oꢀ this new synthetic protocol were ꢀurther studied
with the examination oꢀ several aromatic nitriles at the optimized reaction con-
ditions (Table 2). The obtained results exhibited that all reactions were carried
out successꢀully in H O within 3–25 min to aꢁord benzylic primary amines in
2
high to excellent yields. On the basis oꢀ the obtained results, it is observed that
aromatic nitriles with electron-donating or electron withdrawing groups have
no general trend on the reactivity were ꢀound. Moreover, the results oꢀ the cur-
rent study indicated that the chemoselective reduction oꢀ nitriles in the presence
oꢀ nitro ꢀunctional group was achieved successꢀully through the reduction oꢀ
3
-nitrobenzonitrile to 3-nitrobenzylamine in 92% yield under the optimized reac-
tion conditions (Table 2, entry 10). But, by increasing the amount oꢀ CuFe O
2
4
ꢀ
rom 0.2 mmol to 1 mmol, both oꢀ the ꢀunctional groups were reduced (Table 2,
entry 11). Molecules containing the carbonyl groups did not show any selectivity,
and both ꢀunctional groups were reduced. This ꢀact was shown by the reduction
oꢀ 4-ꢀormylbenzonitrile to its corresponding product (Table 2, entries 12–13).
Further examinations showed that reduction oꢀ dicyanobenzenes (Table 2, entry
1
4–16) required higher molar equivalents oꢀ NaBH and CuFe O MNPs (4:0.5).
4
2
4
It is notable that ꢀor the reduction oꢀ some compounds, NaBH should be added
4
portion-wise at about 5 min interval into the mixture oꢀ reaction. The obtained
1
3

B. Zeynizadeh et al.
Table 2 Chemoselective reduction oꢀ nitriles to primary amines with NaBH4 catalyzed by CuFe O4
2
MNPs in water
f
Entrya
Substrate
Product
Molar
ratio
Time Yield TONe TOF
b
(%)c
–
1
(min)
(h )
1
1:0.2:2
1:0.2:2
1:0.2:2
1:0.2:2
1:0.2:2
1:0.2:2
1:0.2:2
1:0.2:2
5
95
4.75
4.45
4.6
56.999
2
3
4
5
6
7
8
13
15
5
89
92
83
88
78
80
85
20.538
18.4
4.15
4.4
49.799
37.714
78
7
3
3.9
5
4
47.999
50.999
5
4.25
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 2 (continued)
9
1:0.2:2
1:0.2:2
1:1:2
10
10
20
45s
12
13
25
15
90
92
92
87
90
88
85
80
4.5
4.6
27
27.6
1
0d
1
1d
0.92
8.7
2.76
1
2
1:0.1:0.5
1:0.2:2
1:0.5:4
1:0.5:4
1:0.5:4
69.600
22.5
1
1
1
1
3d
4d
5d
6d
4.5
1.76
1.7
8.123
4.080
6.4
1.6
1
3

B. Zeynizadeh et al.
Table 2 (continued)
a
All reactions were carried out in 2 mL oꢀ H O
2
b
Substrate:CuFe O :NaBH
2
4
4
c
d
e
ꢀ
Yields reꢀer to isolated pure products
NaBH was added portion-wisely
4
TON (turnover number)=[(mol oꢀ product ꢀormed)/(mol oꢀ catalyst used)]
TOF (turnover ꢀrequency)=[(mol oꢀ product ꢀormed)/(mol oꢀ catalyst used)×(time)]
results are in presented in Table 2. Also, a plausible reaction mechanism ꢀor the
green and convenient reduction oꢀ aromatic nitriles to corresponding primary
amines is depicted in Scheme 3.
Scheme 3 Plausible mechanism ꢀor the reduction oꢀ nitriles to corresponding primary amines with
NaBH catalyzed by CuFe O MNPs
4
2
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 3 Comparison oꢀ the redution oꢀ benzonitrile to benzylamine catalyzed by CuFe O with other
2
4
reported strategies
Entry Reaction conditions
Time
Yield (%) Reꢀerences
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
NaBH /CuFe O /H O/Reꢃux
5 min
5 min
4 h
24 h
1 h
24 h
6 h
24 h
1 h
95
82
75
91
95
95
98
71
99
94
*
4
2
4
2
NaBH /NiCl /EtOH/r.t.
[28]
[29]
[37]
[38]
[39]
[47]
[48]
[49]
[53]
[54]
[55]
[58]
[63]
[66]
[67]
[70]
[71]
[72]
[73]
4
2
NaBH /InCl /THF/25 °C
4
3
PhSiH /ReIO (PPh ) /Toluene/Reꢃux
3
2
3 2
PhSiH /n-Bu NF/Toluene/r.t.
3
4
TMDS/Ti(OiPr) /Methylcyclohexanone/60 °C
4
H /[Ru(cod)methylallyl ]/PPh /t-BuOK/Toluene/80 °C
2
2
3
H /[RuCl (PPh ) ]/t-BuOK/Toluene/80 °C
2
2
3 3
H /[Ru(cod)methylallyl ]/DPPF/t-BuOK/Toluene/80 °C
2
2
(
0)
0
1
2
3
4
5
6
7
8
9
0
NaBH /Fe O @PAMAM/Ni -b-PEG/H O/95 °C
1 h
4
3
4
2
(
II)
NaBH /MWCNTs/Fe O @PCA/Pt /H O/95 °C
30 min 96
4 h
4
3
4
2
(
0)
NaBH /amorphous nickel powder (Ni )/MeOH/30–40 °C
89
99
90
100
94
4
H /[Ru(cod)(2-methylallyl) ]/SlMesBF /t-BuOK/Toluene/80 °C 1 h
2
2
4
H /[RuCl (PPh ) ]/NH OH/100 °C
24 h
1 h
24 h
2
2
3 3
4
NaBH /CuNP/WS-1/H O/95 °C
4
2
TMDS/Cu(OTꢀ)/1,2,3-TMP/100 °C
NH BH /G-Ni Pd /H O:CH OH (3:7)/r.t.
10 min 99
3
3
30
70
2
3
HCO H–N(CH CH ) /FS-NH –RhCu@MSiO /40 °C
3 h
3 h
6 h
99
99
99
2
2
3 3
2
2
H /Pd-NPs/H O (pH=1.0)/r.t.
2
2
H /MC supported nickel nanoparticles/NH ·H O/
2
3
2
CH OH/100 °C
3
*
This work
It is worthwhile to note that suitability and useꢀulness oꢀ the current green strat-
egy ꢀor the reduction oꢀ nitriles were then highlighted by the comparison oꢀ the
obtained results ꢀor reduction oꢀ benzonitrile with current protocol and oꢀ those
reported ꢀor other catalytic systems (Table 3). The results exhibited that ꢀrom the
viewpoints oꢀ easy availability and preparation oꢀ the catalyst, the reaction times,
and needed quantities oꢀ the catalyst, the yield oꢀ the desired product, eꢂciency as
well as the recoverability and reusability oꢀ the catalyst, and so on, the current proto-
col shows more eꢂciency.
Reduction of nitro compounds in the presence of CuFe O MNPs
2
4
To get started, the reduction oꢀ nitrobenzene (PhNO ) as a model compound with
2
sodium borohydride was investigated in the absence and presence oꢀ CuFe O MNPs
2
4
1
3

B. Zeynizadeh et al.
Table 4 Optimization experiments ꢀor the reduction oꢀ nitrobenzene to aniline with NaBH catalyzed by
4
CuFe O MNPs
2
4
Entrya
NaBH
CuFe O
Solvent
Condition
Time (min)
Conversion (%)
4
2
4
(
mmol)
(mmol)
1
2
3
4
5
6
7
8
9
2
3
3
2
2
2
2
2
2
‒
1
1
1
H O
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
Reꢃux
120
120
120
120
120
50
45
23
10
30
0
0
50
80
100
100
100
100
2
MeOH
EtOH
THF
1
CH CN
3
0.2
0.5
0.7
1
H O
2
H O
2
H O
2
H O
2
aAll reactions were carried out with 1 mmol oꢀ nitrobenzene in 2 mL oꢀ solvent
under diꢁerent reaction conditions including the use oꢀ diꢁerent amounts oꢀ men-
tioned nanocomposite and NaBH as well as solvent changing. The results oꢀ these
4
investigations are summarized in Table 4. These results showed that H O was the
2
best solvent to progress the reaction perꢀectly, and using the molar equivalent oꢀ
CuFe O :NaBH (0.2:2) was the requirement to complete reduction oꢀ nitrobenzene
2
4
4
to aniline within 50 min at reꢃux (Table 4, entry 6). More examination resulted in
that using higher quantities oꢀ copper ꢀerrite MNPs progressed the reaction in a short
time (Table 4, entries 7–9). However, the reaction condition mentioned in entry 6 oꢀ
Table 4 was selected as the minimum requirements ꢀor completing the titled reaction.
Furthermore, the progress oꢀ the reduction oꢀ nitrobenzene to aniline with NaBH
4
as a reducing agent in the presence oꢀ CuFe O MNPs was also studied and con-
2
4
frmed by UV–Vis analysis using the optimized reaction conditions (mentioned in
Table 4, entry 6). As shown in Fig. 8, during the reduction reaction, nitrobenzene
which is indicated by the red curve (λ =268 nm) was ꢀully converted to aniline
max
(
λ
=233 nm) which is intimated by the blue curve.
max
It should also be mention that the reduction oꢀ nitrobenzene to aniline could
be considered as pseudo-frst-order kinetics because the concentration oꢀ NaBH
4
was in excess. Notably, the pseudo-frst-order kinetics equation can be defned as
ln(C /C )=−k t, where C and C are the initial and instantaneous concentration oꢀ
t
0
app
0
t
nitrobenzene, respectively. As well as the t and k stand ꢀor the apparent reaction
app
time and rate constant in turn. Thus, the reaction apparent rate constant (k ) can be
app
simply calculated with the slope oꢀ ln(C /C ) versus reaction time. In this study, the
t
0
−2
−1
k
ꢀor nitrobenzene reduction was 8.32×10 min (Fig. 9).
app
In order to investigate the eꢁects oꢀ the NaBH amount on the reaction rate,
4
the concentration oꢀ nitrobenzene and CuFe O was kept constant and various
2
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Fig. 8 UV–Vis analysis oꢀ nitrobenzene reduction under optimized reaction conditions
Fig. 9 Relationship between ln(C /C ) and reaction time ꢀor the reduction oꢀ nitrobenzene
t
0
1
3

B. Zeynizadeh et al.
Fig. 10 Eꢁect oꢀ the concentration oꢀ NaBH on the reaction rate
4
Table 5 Eꢁect oꢀ the concentration oꢀ NaBH on the reaction rate
4
Entry
NaBH (mmol)
Time (min)
kapp (min)
4
1
2
3
4
2
50
45
33
25
0.0832
0.0995
0.1541
0.2227
2.3
2.6
3
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 6 Eꢁect oꢀ the concentration oꢀ CuFe O on the reaction rate
2
4
Entry
CuFe O (mmol)
Time (min)
kapp (min)
2
4
1
2
3
4
0.2
0.5
0.7
1
50
40
23
10
0.083
0.1325
0.2306
0.5346
Fig. 11 Eꢁect oꢀ the concentration oꢀ CuFe O on the reaction rate
2
4
1
3

B. Zeynizadeh et al.
Table 7 Reduction oꢀ nitro compounds to amines with NaBH in water at reꢃux catalyzed by CuFe O
4
4
2
MNPs
Entrya
Substrate
Product
Molar
b
Time
(min)
Yield TONe
(%)
TOFf
(h )
c
–1
ratio
1
1
:0.2:2
:1:2
50
10
4.75
0.95
5.700
5.69
1
2
95
1
1
:0.2:2
:1:2
70
10
4.55
0.91
3.899
5.45
91
1
1
:0.2:2
:1:2
55
20
4.65
0.93
5.072
2.790
3
4
93
1
1
:0.2:3
:1:3
80
30
4.5
0.9
3.375
1.8
90
5d
1:0.2:3
:1:3
60
20
4.75
0.95
4.75
2.850
95
1
6d
1:0.2:2
:1:2
50
20
4.9
0.98
5.880
2.940
98
1
1
1
:0.2:2
:1:2
70
30
4.9
0.98
4.199
1.96
7
98
8d
1:0.2:3
:1:3
40
25
4.15
0.83
6.224
1.991
83
1
9d
1:0.2:3
:1:3
50
30
4.4
0.88
5.280
1.76
88
1
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 7 (continued)
0d
1:0.2:3
:1:3
55
30
4.5
0.9
4.909
1.8
1
90
92
91
1
1
1
:0.2:3
:1:3
10
4
4.6
0.92
27.599
13.79
1
1
2
3
4
1
1:0.1:0.5
2
9.1
273.000
1
1
:0.2:3
:1:3
15
5
4.5
0.9
18
10.800
1
1
90
94
92
1:0.1:0.5
1:0.2:3
2
9.4
282.000
5d
55
15
4.6
0.92
5.018
3.68
1
1
:1:3
1
6
1:0.1:0.5
1
93
9.3
557.999
7d
1:0.2:2
20
10
4.55
0.91
13.650
5.459
1
91
96
1
:1:2
1
8
1:0.1:0.5
45s
9.6
768
1
3

B. Zeynizadeh et al.
Table 7 (continued)
9d
1:0.2:3
:1:3
45
20
4.4
0.88
5.866
2.640
1
88
92
1
2
0
1:0.2:2
3
4.6
92
1d
1:0.2:2.5
40
25
4.5
0.9
6.749
2.159
2
90
95
1:1:2.5
2d
1:0.2:3
:1:3
50
30
4.75
0.95
5.700
1.9
2
2
1
3d
1:0.2:2
:1:2
15
5
4.45
0.89
17.8
10.680
89
93
1
1
1
:0.2:2
:1:2
20
15
4.65
0.93
13.950
3.72
2
4
1
1
:0.2:2
:1:2
25
20
4.6
0.92
11.039
2.760
2
5
6
92
92
1
1
:0.2:2
:1:2
42
25
4.6
0.92
6.571
2.207
2
2
1
1
:0.2:2
:1:2
35
5
4.3
0.86
7.371
10.320
7
8
86
90
1
1
:0.2:2
:1:2
40
10
4.5
0.9
6.749
5.399
2
1
3

Green and convenient protocols for the eꢀcient reduction…
Table 7 (continued)
a
All reactions were carried out in reꢃuxing H O (2 mL)
2
b
Substrate:CuFe O :NaBH
2
4
4
c
d
e
ꢀ
Yields reꢀer to isolated pure products
NaBH was added portion-wisely
4
TON (turnover number)=[(mol oꢀ product ꢀormed)/(mol oꢀ catalyst used)]
TOF (turnover ꢀrequency)=[(mol oꢀ product ꢀormed)/(mol oꢀ catalyst used)×(time)]
amounts oꢀ NaBH as a reducing agent (2, 2.3, 2.6, and 3 mmol) were added to
4
the reaction vessel. According to the UV–visible spectra (Fig. 10), the reaction
was completed at 50, 45, 33 and 25 min, respectively. Also, Table 5 shows k ꢀor
app
these reactions. Based on the obtained results, we observed that with increasing
the concentration oꢀ NaBH , the amount oꢀ the k increased. Notably, although
4
app
the increase in the amount oꢀ NaBH increases, the speed oꢀ the reduction reac-
4
tion, based on the green chemistry protocols, especially economic eꢂciency, we
selected 2 mmol oꢀ the NaBH as an optimal amount oꢀ reducing agent ꢀor the
4
mentioned reaction.
The eꢁect oꢀ various CuFe O amounts on the reaction rate was also stud-
2
4
ied. All the other reaction parameters during the mentioned reaction were kept
constant. Based on the results obtained ꢀrom Table 6 and Fig. 11, it can be seen
−
1
that the k increased ꢀrom 0.08 to 0.2 min as increasing the concentration oꢀ
app
CuFe O ꢀrom 0.2 to 1 mmol. Notably, the results clearly showed that the depend-
2
4
ence oꢀ the reaction rate on various CuFe O amounts is much higher than NaBH
2
4
4
various value.
Aꢀter kinetic studies, the capability oꢀ this synthetic protocol was studied ꢀurther
with the reduction oꢀ various aromatic nitro compounds under optimized reaction
conditions (Table 4, entry 6). The summarized results in Table 7 show that reduc-
tion oꢀ nitroarenes possessing electron-releasing or withdrawing groups was carried
out successꢀully with 2–3 molar equivalents oꢀ NaBH in the presence oꢀ 20 mol%
4
oꢀ CuFe O MNPs. All reactions were carried out within 10–80 min in reꢃuxing
2
4
H O to aꢁord amines in high to excellent yields. It is noteworthy that in the case
2
oꢀ nitroarenes having ꢀormyl and keto groups, the protocol shows the perꢀect selec-
tivity between nitro and carbonyl ꢀunctionalities. With higher quantities oꢀ NaBH
4
(
3 molar equivalents) and 20 mol% oꢀ CuFe O MNPs, both oꢀ nitro and carbonyl
2
4
moieties were reduced with the same reactivity (Table 7, entries 11, 13, 15, 17 and
1
1
9), whereas, using low amounts oꢀ reducing agent (0.5–2 molar equivalents) and
0–20 mol% oꢀ CuFe O MNPs, the carbonyl moiety was reduced selectively lead-
2
4
ing to the nitro group remaining intact (Table 7, entries 12, 14, 16, 18 and 20). We
also ꢀound that the reducing capability oꢀ NaBH in the presence oꢀ copper ꢀerrite
4
nanocomposite was not suꢂcient to reduce acetamide, carboxylic acid, and halogen
ꢀ
unctionalities. So under the examined reaction conditions, these moieties remained
intact (Table 7, entries, 21, 23, 24 and 25).
The capability oꢀ the current reduction protocol towards the reduction oꢀ ali-
phatic nitro compounds was also examined by reduction oꢀ 1-nitrohexane and
1
3

B. Zeynizadeh et al.
Scheme 4 Plausible mechanism ꢀor the reduction oꢀ nitro compounds to corresponding amines with
NaBH catalyzed by CuFe O MNPs
4
2
4
1
3

Green and convenient protocols for the eꢀcient reduction…
Fig. 12 Reusability oꢀ CuFe O MNPs in the reduction oꢀ benzonitrile to benzylamine
2
4
Fig. 13 Reusability oꢀ CuFe O MNPs in the reduction oꢀ nitrobenzene to aniline
2
4
2
-nitroheptane with 2 molar equivalents oꢀ NaBH and 20 mol% oꢀ CuFe O MNPs
4
2
4
in reꢃuxing H O. The results showed that as aromatic nitro compounds, this proto-
2
col was also eꢂcient, and the corresponding aliphatic amines were obtained suc-
cessꢀully in 86–90% yields within 35–40 min (Table 7, entries 27 and 28).
The quantity eꢁect oꢀ copper ꢀerrite MNPs on reducing capability and selectivity
oꢀ NaBH was ꢀurther studied by examining all reduction reactions oꢀ aromatic and
4
aliphatic nitro compounds with NaBH in the presence oꢀ one molar equivalent oꢀ
4
CuFe O MNPs in reꢃuxing H O (Table 7). The results represent that, although the
2
4
2
progress oꢀ reduction reactions was carried out in shorter reaction times, however,
using the ꢀurther amounts oꢀ nanocatalyst did not aꢁect any selectivity derived with
low amounts oꢀ the mentioned nanocomposite.
Also, we depicted a plausible mechanism ꢀor the reduction oꢀ nitro compounds
to corresponding amines with NaBH in water catalyzed by CuFe O MNPs
4
2
4
(
Scheme 4).
1
3

B. Zeynizadeh et al.
Fig. 14 Recyclability plot ꢀor the reduction oꢀ nitrobenzene to aniline
Recycling CuFe O MNPs
2
4
In continuation, the reusability oꢀ the copper ꢀerrite nanocomposite was studied in
the reduction oꢀ benzonitrile and also nitrobenzene to corresponding benzylamine
and aniline at the optimized reaction conditions, respectively. In both mentioned
reactions, aꢀter completion oꢀ the reaction, CuFe O was isolated ꢀrom the reaction
2
4
mixture by applying an external magnetic feld. The catalyst was then washed with
acetone and then dried in an oven at 120 °C. The vessel oꢀ the reaction was again
charged with ꢀresh desired substrate, the recycled CuFe O , and NaBH in water at
2
4
4
reꢃux ꢀor a second time. The examination resulted in that the nanocatalyst CuFe O
2
4
was recycled and reused ꢀor six consecutive cycles without loss oꢀ its catalytic activ-
ity (Figs. 12, 13).
It is worthwhile to note that in the case oꢀ reduction oꢀ nitrobenzene to aniline,
the eꢁect oꢀ recyclability catalyst concentration was investigated. In this regard,
UV–Vis studies were carried out in an investigation oꢀ the reaction rate promo-
tion at each recycling time. According to Fig. 14, CuFe O has the high ability to
2
4
produce 100% reduction oꢀ nitrobenzene to aniline aꢀter six cycles. But increasing
1
3

Green and convenient protocols for the eꢀcient reduction…
reaction time per cycle was observed. This increase in the reaction time can be due
to a decrease in the amount oꢀ CuFe O during its separation step at each test run.
2
4
Conclusions
In summary, we have developed green, inexpensive and eꢂcient protocols ꢀor the
convenient reduction oꢀ nitriles and nitro compounds using NaBH as a mild reduc-
4
ing agent in water at reꢃux catalyzed by magnetic CuFe O NPs. Notably, CuFe O
2
4
2
4
MNPs was prepared via the simple operation and characterized by FT-IR, XRD,
SEM, TEM, EDX, ICP-OES, VSM and also BET and BJH analyses. Also, the cata-
lyst is recoverable and reused at least six cycles without losing its catalytic activity
on both mentioned reduction reactions.
Acknowledgements We are thankꢀul to the research council oꢀ Urmia University ꢀor the partial support
oꢀ this work.
Compliance with ethical standards
Conꢁict of interest The authors declare that they have no conꢃict oꢀ interest.
References
1
2
.
.
T. Senthamarai, K. Murugesan, K. Natte, N.V. Kalevaru, H. Neumann, P.C.J. Kamer, R.V.
Jagadeesh, ChemCatChem 10, 1235 (2018)
I.B. Seiple, S. Su, I.S. Young, C.A. Lewis, J. Yamaguchi, P.S. Baran, Angew. Chem. Int. Ed. 49,
1
095 (2010)
3
4
.
.
A. Gomm, E. O’Reilly, Curr. Opin. Chem. Biol. 43, 106 (2018)
R.S. Kokane, V.R. Acham, A.B. Kulal, E. Kemnitz, M.K. Dongare, S.B. Umbarkar, ChemistrySe-
lect 2, 10618 (2017)
5
6
7
8
9
.
.
.
.
.
M. Rimaz, H. Mousavi, M. Behnam, B. Khalili, Curr. Chem. Lett. 5, 145 (2016)
M. Rimaz, B. Khalili, G. Khatyal, H. Mousavi, F. Aali, Aust. J. Chem. 70, 1274 (2017)
R. Madhavachary, T. Zarganes-Tłuścik, A. Dömling, ACS Comb. Sci. 20, 192 (2018)
R. Bansal, P.K. Soni, A.K. Halve, J. Heterocycl. Chem. 55, 1308 (2018)
Y. Selim, M.H.M.A. El-Azim, J. Heterocycl. Chem. 55, 1403 (2018)
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
0. R. Saini, S.R. Malladi, N. Dharavath, J. Heterocycl. Chem. 55, 1579 (2018)
1. A. Ghorbani-Choghamarani, Z. Taherinia, Aust. J. Chem. 70, 1127 (2017)
2. H. Kandemir, I.F. Sengul, N. Kumar, D.S. Black, Aust. J. Chem. 70, 1196 (2017)
3. G. Khanna, P. Saluja, J.M. Khurana, Aust. J. Chem. 70, 1285 (2017)
4. B. Xu, J. Su, J. Wang, G.-C. Zhou, Aust. J. Chem. 69, 770 (2016)
5. Y. Kuninobu, Y. Nishina, M. Shouho, K. Takai, Angew. Chem. 118, 2832 (2006)
6. M. Rimaz, H. Mousavi, M. Behnam, L. Sarvari, B. Khalili, Curr. Chem. Lett. 6, 55 (2017)
7. A. Saeed, P.A. Channar, J. Heterocycl. Chem. 54, 780 (2017)
8. M. Rimaz, H. Mousavi, L. Nikpey, B. Khalili, Res. Chem. Intermed. 43, 3925 (2017)
9. S.H. Mccooey, S.J. Connon, Org. Lett. 9, 599 (2007)
0. J. Ou-Yang, Y. Zhao, H. Jiang, L. Meng, X. Li, X. Jia, Aust. J. Chem. 68, 1599 (2015)
1. M. Rimaz, H. Mousavi, Turk. J. Chem. 37, 252 (2013)
2. A. Komaromi, G.L. Tolnai, Z. Novak, Tetrahedron Lett. 49, 7294 (2008)
3. S. Uppuluri, S.E. Keinath, D.A. Tomalia, P.R. Dvornic, Macromolecules 31, 4498 (1998)
4. L.H. Amundsen, L.S. Nelson, J. Am. Chem. Soc. 73, 242 (1951)
1
3

B. Zeynizadeh et al.
2
2
2
2
2
5. T. Satoh, S. Suzuki, Y. Suzuki, Y. Miyaji, Z. Imai, Tetrahedron Lett. 10, 4555 (1969)
6. S.W. Heinzman, B. Ganem, J. Am. Chem. Soc. 104, 6801 (1982)
7. J.O. Osby, S.W. Heinzman, B. Ganem, J. Am. Chem. Soc. 108, 67 (1986)
8. J.M. Khurana, G. Kukreja, Synth. Commun. 32, 1265 (2002)
9. J.Z. Saavedra, A. Resendez, A. Rovira, S. Eagon, D. Haddenham, B. Singaram, J. Org. Chem. 77,
2
21 (2012)
3
3
3
0. A.S. Bhanu Prasad, J.V. Bhaskar Kanth, M. Periasamy, Tetrahedron 48, 4623 (1992)
1. D. Haddenham, L. Pasumansky, J. DeSoto, S. Eagon, B. Singaram, J. Org. Chem. 74, 1646 (2009)
2. S. Thomas, C.J. Collins, J.R. Cuzens, D. Spieciarich, C.T. Goralski, B. Singaram, J. Org. Chem. 66,
1
999 (2001)
3
3
3
3
3
3
3
3. B. Wu, J. Zhang, M. Yang, Y. Yue, L.-J. Ma, X.-Q. Yu, Arkivoc xii, 95 (2008)
4. H.C. Brown, Y.M. Choi, S. Narasimhan, Synthesis 605 (1981)
5. A. Nose, T. Kudo, Chem. Pharm. Bull. 38, 1720 (1990)
6. N. Gandhamsetty, J. Jeong, J. Park, S. Park, S. Chang, J. Org. Chem. 80, 7281 (2015)
7. I. Cabrita, A.C. Fernandes, Tetrahedron 67, 8183 (2011)
8. C. Bornschein, S. Werkmeister, K. Jungea, M. Beller, New J. Chem. 37, 2061 (2013)
9. S. Laval, W. Dayoub, A. Favre-Reguillon, M. Berthod, P. Demonchaux, G. Mignani, M. Lemaire,
Tetrahedron Lett. 50, 7005 (2009)
4
4
4
4
4
4
4
4
4
4
5
0. X. Chen, S. Zhou, C. Qian, Arkivoc viii, 128 (2012)
1. M. Szostak, B. Sautier, M. Spain, D.J. Procter, Org. Lett. 16, 1092 (2014)
2. A. Muthukumaran, V. Krishnan, Bull. Electrochem. 7, 410 (1991)
3. W.H. Carothers, G.A. Jones, J. Am. Chem. Soc. 47, 3051 (1925)
4. F.E. Gould, G.S. Johnson, A.F. Ferris, J. Org. Chem. 25, 1658 (1960)
5. M. Freiꢀelder, J. Am. Chem. Soc. 82, 2386 (1960)
6. S. Takamizawa, N. Wakasa, T. Fuchikami, Synlett 10, 1623 (2001)
7. S. Enthaler, K. Junge, D. Addis, G. Erre, M. Beller, ChemSusChem 1, 1006 (2008)
8. S. Das, S. Zhou, D. Addis, S. Enthaler, K. Junge, M. Beller, Top. Catal. 53, 979 (2010)
9. S. Enthaler, D. Addis, K. Junge, G. Erre, M. Beller, Chem. Eur. J. 14, 9491 (2008)
0. C. Bornschein, S. Werkmeister, B. Wendt, H. Jiao, E. Alberico, W. Baumann, H. Junge, K. Junge,
M. Beller, Nat. Commun. 5, 4111 (2014)
5
5
1. R. Adam, C.B. Bheeter, R. Jackstell, M. Beller, ChemCatChem 8, 1329 (2016)
2. X. Miao, J. Bidange, P.H. Dixneuꢀ, C. Fischmeister, C. Bruneau, J.-L. Dubois, J.-L. Couturier,
ChemCatChem 4, 1911 (2012)
5
5
3. S.J. Tabatabaei Rezaei, A. Mashhadi Malekzadeh, S. Poulaei, A. Ramazani, H. Khorramabadi,
Appl. Organomet. Chem. 32, e3975 (2018)
4. S.J. Tabatabaei Rezaei, H. Khorramabadi, A. Hesami, A. Ramazani, V. Amani, R. Ahmadi, Ind.
Eng. Chem. Res. 56, 12256 (2017)
5
5
5
5
5
6
5. S. Liu, Y. Yang, X. Zhen, J. Li, H. He, J. Feng, A. Whiting, Org. Biomol. Chem. 10, 663 (2012)
6. K. Tokmic, B.J. Jackson, A. Salazar, T.J. Woods, A.R. Fout, J. Am. Chem. Soc. 139, 13554 (2017)
7. C. Yu, J. Fu, M. Muzzio, T. Shen, D. Su, J. Zhu, S. Sun, Chem. Mater. 29, 1413 (2017)
8. D. Addis, S. Enthaler, K. Junge, B. Wendt, M. Beller, Tetrahedron Lett. 50, 3654 (2009)
9. M.R. Nabid, Y. Bide, M. Niknezhad, ChemCatChem 6, 538 (2014)
0. R. Ferraccioli, D. Borovika, A.-E. Surkus, C. Kreyenschlte, C. Topꢀ, M. Beller, Catal. Sci. Technol.
8
, 499 (2018)
6
1. M. Yoshimura, A. Komatsu, M. Niimura, Y. Takagi, T. Takahashi, S. Ueda, T. Ichikawa, Y. Kob-
ayashi, H. Okami, T. Hattori, Y. Sawama, Y. Monguchin, H. Sajik, Adv. Synth. Catal. 360, 1726
(
2018)
6
2. T. Takao, S. Horikoshi, T. Kawashima, S. Asano, Y. Takahashi, A. Sawano, H. Suzuki, Organome-
tallics 37, 1598 (2018)
6
6
6
6
3. A.N. Ajjou, A. Robichaud, Appl. Organomet. Chem. 32, e4481 (2018)
4. S. Das, B. Wendt, K. Möller, K. Junge, M. Beller, Angew. Chem. 124, 1694 (2012)
5. A.N. Ajjou, A. Robichaud, Appl. Organomet. Chem. 32, e4547 (2018)
6. A. Zamani, A. Poursattar Marjani, A. Nikoo, M. Heidarpour, A. Dehghan, Inorg. Nano-Metal
Chem. 8, 1 (2019)
6
6
7. M. Sutter, L. Pehlivan, R. Laꢀon, W. Dayoub, Y. Raoul, E. Métay, M. Lemaire, Green Chem. 15,
3
020 (2013)
8. D. Mullangi, D. Chakraborty, A. Pradeep, V. Koshti, C.P. Vinod, S. Panja, S. Nair, R. Vaidhyana-
than, Small 14, 1801233 (2018)
1
3

Green and convenient protocols for the eꢀcient reduction…
6
7
7
9. L. Liu, Y. Liu, Y. Ai, J. Li, J. Zhou, Z. Fan, H. Bao, R. Jiang, Z. Hu, J. Wang, K. Jing, Y. Wang, Q.
Liang, H. Sun, Science 8, 61 (2018)
0. H. Göksu, S.F. Ho, Ö. Metin, K. Korkmaz, A.M. Garcia, M.S. Gültekin, S. Sun, ACS Catal. 4, 1777
(
2018)
1. L. Liu, J. Li, Y. Ai, Y. Liu, J. Xiong, H. Wang, Y. Qiao, W. Liu, S. Tan, S. Feng, K. Wang, H. Sun,
Q. Liang, Green Chem. (2019). https://doi.org/10.1039/C8GC03595D
7
7
2. Y. Liu, S. He, Z. Quan, H. Cai, Y. Zhao, B. Wang, Green Chem. 21, 830 (2019)
3. Y. Zhang, H. Yang, Q. Chi, Z. Zhang, ChemSusChem (2019). https://doi.org/10.1002/cssc.20180
2
459
7
7
7
7
7
7
8
8
8
4. N. Futtahi, M. Ayoubi, A. Ramazani, Tetrahedron 74, 4351 (2018)
5. H.Y. Lü, S.-H. Yang, J. Deng, Z.-H. Zhang, Aust. J. Chem. 63, 1290 (2010)
6. M. Rimaz, J. Khalaꢀy, P. Najaf-Moghaddam, Aust. J. Chem. 63, 1396 (2010)
7. M. Rimaz, J. Khalaꢀy, H. Mousavi, S. Bohlooli, B. Khalili, J. Heterocycl. Chem. 54, 3174 (2017)
8. M. Rimaz, J. Khalaꢀy, H. Mousavi, Res. Chem. Intermed. 42, 8185 (2016)
9. M. Rimaz, H. Mousavi, B. Khalili, F. Aali, J. Chin. Chem. Soc. 65, 1389 (2018)
0. L.M. Rossi, N.J.S. Costa, F.P. Silva, R. Wojcieszak, Green Chem. 16, 2933 (2014)
1. D. Wang, D. Astruc, Chem. Soc. Rev. 46, 816 (2017)
2. A.F. Costa, P.M. Pimentel, F.M. Aquino, D.M.A. Melo, M.A.F. Melo, I.M.G. Santos, Mater. Lett.
1
12, 58 (2013)
8
8
8
8
8
8
3. Z. Sun, L. Liu, D.Z. Jia, W. Pan, Sens. Actuators B Chem. 125, 144 (2007)
4. E.R. Kumar, S.P. Reddy, G.S. Devi, S. Sathiyaraj, J. Magn. Magn. Mat. 398, 281 (2016)
5. H. Mousavi, B. Zeynizadeh, R. Younesi, M. Esmati, Aust. J. Chem. 71, 595 (2018)
6. B. Zeynizadeh, R. Younesi, H. Mousavi, Res. Chem. Intermed. 44, 7331 (2018)
7. B. Zeynizadeh, F. Sepehraddin, J. Organomet. Chem. 856, 70 (2018)
8. B. Zeynizadeh, H. Mousavi, S. Zarrin, J. Chin. Chem. Soc. (2019). https://doi.org/10.1002/
jccs.201800325
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