Spinel Structured Copper Ferrite Nano Catalyst with Magnetic Recyclability for Oxidative Decarboxylation of Phenyl Acetic Acids

Article abstract of DOI:10.1007/s10562-020-03131-0

Abstract: A simple, efficient and environmentally benign method has been discussed for the synthesis of aldehydes and ketones by the oxidative decarboxylation of phenylacetic acid under ligand free condition using simple, efficient, preparatively easy, magnetically recoverable and low cost spinel CuFe₂O₄ nanoparticles. The catalyst was characterised using powder-XRD, FTIR, FE-SEM, EDX, VSM and HRTEM. The recyclability was examined and the results showed that the catalyst remained almost equally active up to five consecutive cycles. Graphic Abstract: Spinel Structured Copper Ferrite is a very efficient nano catalyst for Oxidative decarboxylation of Phenyl acetic acids and can be reused up to five cycles without significant loss in catalytic activity.[Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-020-03131-0

Catalysis Letters
https://doi.org/10.1007/s10562-020-03131-0
Spinel Structured Copper Ferrite Nano Catalyst with Magnetic
Recyclability for Oxidative Decarboxylation of Phenyl Acetic Acids
Taskia Rahman1 · Geetika Borah1 · Pradip K. Gogoi1
Received: 11 November 2019 / Accepted: 31 January 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
A simple, efcient and environmentally benign method has been discussed for the synthesis of aldehydes and ketones by
the oxidative decarboxylation of phenylacetic acid under ligand free condition using simple, efcient, preparatively easy,
magnetically recoverable and low cost spinel CuFe2O4 nanoparticles. The catalyst was characterised using powder-XRD,
FTIR, FE-SEM, EDX, VSM and HRTEM. The recyclability was examined and the results showed that the catalyst remained
almost equally active up to fve consecutive cycles.
Graphic Abstract
Spinel Structured Copper Ferrite is a very efcient nano catalyst for Oxidative decarboxylation of Phenyl acetic acids and
can be reused up to fve cycles without signifcant loss in catalytic activity.
O
OH
R
O
R
Keywords Heterogeneous catalysis · Oxidative decarboxylation · Phenyl acetic acid · Magnetic nanoparticles
1 Introduction
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-020-03131-0) contains
supplementary material, which is available to authorized users.
In contemporary time, the transition metal catalyzed C–C
bond cleavage has been emerged as one of the most signif-
cant reaction in organic chemistry. The selective cleavage
of the C–C bond is a remarkable challenge for synthetic
Extended author information available on the last page of the article
Vol.:(0123456789)
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T. Rahman et al.
chemists and biologists as well due to the inert nature of
C–C σ-bonds. In a multistep reaction sequence decarboxy-
lation of organic acids is one of the most important reac-
tions in organic synthesis. Among all types of the reactions,
functional group introduction at sp3-hybridized carbon by
decarboxylation is rare and remains a major challenge com-
pared to sp2-hybridized carbon which is mostly explored
in the literature [1–5]. Researchers are attracted towards
transition-metal-catalyzed decarboxylation reactions due
to readily accessible starting materials, operational sim-
plicity, and clean byproduct. In the past few years Liu and
his co-workers developed several Pd-catalyzed decarboxy-
lations using diferent types of aliphatic carboxylate salts
[6–8], however the direct transition-metal-catalyzed decar-
boxylation of sp3-hybridized carboxylic acids with the for-
mation of a new C=O bond in the adjacent carbon using
molecular oxygen as the oxidant is rare [9, 10]. But, Pd-
catalyzed methods sufer from various disadvantages like Pd
is expensive, air or moisture sensitive, and phosphines are
mostly required for the success of the reactions. Thus, much
attention has been paid towards designing more promising,
greener, efcient, environmentally benign and economically
feasible protocol for the aforementioned transformation is
still in search. In the present decade remarkable progress has
been made with copper catalyzed reactions and strikingly
very few reports have been published in the feld of oxida-
tive decarboxylation reactions namely, Song and co-workers
developed the ability of cupric salts for oxidative decar-
boxylation at sp3-hybridized carbon to aford aldehydes,
ketones [1] and amides [11] at high temperatures in pres-
ence of oxygen as oxidant. Recently, Pahari et al. [12] have
demonstrated aerobic oxidative decarboxylation of pheny-
lacetic acids by cellulose-supported Ag-Ag2S nanoparticles.
Thus, development of a recyclable and recoverable metal
catalytic system capable of carrying out decarboxylation
at sp3-carbon centres under ligand and base free condition
seems important. The development of economically feasi-
ble, eco-friendly and easily retrievable catalytic system has
become a topic of apex priority in industrial and academic
domains. In recent years researchers are interested towards
metal oxide nanoparticles and mixed oxide spinel nano-
particles have received increased attention because of their
wide range of applications in ultra-high magnetic data stor-
age, magnetic resonance imaging, sorbents, drug delivery,
catalysts, bio sensing, nano-electronic materials, electron-
ics industry (electrodes and superconductors), etc. [13–17].
The mixed metal oxide spinels showed comparatively bet-
ter catalytic activity in diferent transformations, viz. CO
oxidation [18, 19], hydrocarbon combustion [20] and redox
reactions of organic compounds [21]. Strikingly, magnetic
spinel nanoparticles have gained wide attention in the pre-
sent decade because of its signifcant advantages such as
remarkable catalytic activity, easy preparation, operational
simplicity, environmentally benign, and recoverability with
an external magnetic feld [22–24]. To prevent the loss of
catalyst and enhances reusability, magnetic separation is
an attractive choice to fltration or centrifugation and also
promising material for various felds such as biomedicine,
biotechnology and materials science. These distinct advan-
tages of magnetic metal oxide nanoparticles in addition to
continuation of our research interest in transition-metal-
catalyzed organic reactions [25, 26] triggered us to develop
magnetically recoverable copper ferrite spinel nanoparticles
for the oxidative decarboxylation reaction of phenylacetic
acid derivatives to aldehydes and ketone.
2 Experimental
2.1 Preparation of Copper Ferrite Nanoparticles
2.5 mmol of Cu(NO3)2·3H2O and 5.0 mmol of
Fe(NO3)3·9H2O was dissolved in 10 mL of distilled water
at 90 °C, followed by addition of 4 M NaOH solution drop
wise to the mixture under vigorous magnetic stirring for 2 h.
The resulting solution was centrifuged and washed several
times with distilled water and acetone, followed by drying
at 110 °C in an oven [22].
3 Results and Discussion
The position and relative intensities of all peaks confrm
well with standard XRD (Fig. 1) pattern of CuFe2O4. The
sharp difraction peaks indicated crystalline nature of
the CuFe2O4 spinel calcined at 500 °C. The difraction
Fig. 1 XRD pattern of CuFe2O4
1 3

Spinel Structured Copper Ferrite Nano Catalyst with Magnetic Recyclability for Oxidative…
15
10
5
0
-20000 -10000
0
10000
20000
-5
-10
-15
Applied field (Oe)
Fig. 2 Magnetic hysteresis loop of CuFe2O4
peaks of CuFe2O4 with 2θ values at 30.1°, 35.6°, 38.7°,
42.8°, 47.3°, 57.1°, 62.95°, 71.2° corresponds to the crys-
tal planes (111), (311), (200), (200), (331), (511), (440),
(620) planes, respectively and could be indexed to face
centred cubic structure (JCPDS card number 34-0425).
The crystallite size, calculated from XRD data based on
the plane (111) at the 2θ value of 30.1° and using the
Scherrer equation was found to be in 16 nm. The room
temperature magnetic hysteresis curve (Magnetization
and Field) of the sample shown in Fig. 2 was studied by
a vibrating sample magnetometer. It exhibited a charac-
teristic pattern of ferromagnetic component. As the driv-
ing magnetic feld was dropped to zero the CuFe2O4 nano
composite has still 1.2684 emu/g remanence value with
coercivity value 260.56 Oe. The saturation magnetization
was found to be 10.795 emu/g. This behaviour of the syn-
thesized material unambiguously supports the presence of
ferromagnetic component.
Fig. 3 FTIR spectra of fresh and reused CuFe2O4
(Fig. 5) confrmed the presence of oxygen, iron and copper
element with iron-copper ratio as approximately 2:1.
To check catalytic activity of spinel CuFe2O4 we began
our investigations taking phenylacetic acid as a model sub-
strate (Table 1). It was observed that the reaction did not
show detectable product formation even after prolonged
time in H2O both at room temperature (Table 1, entry 1)
and elevated temperature (Table 1, entry 2). While the reac-
tion was conducted in DMSO with 15 mol% catalyst at
120 °C for 12 h, the desired product was formed in 76% yield
(Table 1, entry 4). On the other hand, in DMF the conversion
was found to be 68% (Table 1, entry 7). Moreover, a blank
reaction without catalyst showed non formation of product
(Table 1, entry 9). Following the optimized reaction condi-
tions, a number of diferent phenylacetic acid derivatives
were studied. Phenylacetic acids bearing electron-donating
groups on the aromatic rings gave the desired products in
good to excellent yields (Table 2, entries-1, 7 and 11). Phe-
nylacetic acids possessing electron-withdrawing groups
(Table 2, entries-2–6 and 8–10) on the aromatic ring also
reacted smoothly, and produced good to excellent yields of
the desired aldehydes. The position of the substituents on the
aromatic rings afected the product yield. Ortho-substitution
usually giving lower yields of the aldehydes compared to
meta- and para-substitution, which might be due to steric
hindrance. Moreover, we have performed the reaction with
benzoic acid and 4-amino benzoic acid but there is no prod-
uct formation.
The FTIR spectrum of fresh catalyst (Fig. 3) shows a
broad, medium intensity well-defned band at 580 cm−1
which suggests intrinsic stretching vibrations of the Fe–O
bonds at the tetrahedral site and the weak peak at 451 cm−1
attributes to the Cu–O stretching vibration. The recycled
catalyst exhibited quite similar bands in this region. Notably,
observation of two absorption bands below 600 cm−1 is a
universal feature of cubic spinel structure of ferrite materi-
als. The bands at 1602 cm−1and 3431 cm−1(broad) could be
attributed to the γ O–H and υ O–H of water molecules and O–H
groups, respectively [27, 28].
The TEM image (Fig. 4a) showed non homogeneous par-
ticle shape. The selected area electron difraction (SAED)
pattern exhibited sharp difraction that indicated crystalline
nature of the structure. The particle size distribution cal-
culated from TEM image (Fig. 4b) showed narrow sized
dispersion in the range of 2–18 nm. From TEM histogram,
the average particle size of the nanoparticles was found to be
11 nm. The EDX analysis of spinel CuFe2O4 nanoparticles
3.1 Catalyst reusability
The reusability of heterogeneous catalysts becomes a sig-
nificant factor owing to strict economic and ecological
1 3

T. Rahman et al.
Fig. 4 a TEM image of fresh
CuFe2O4 with SAED pattern
(inset) b Particle size distribu-
tion histogram of CuFe2O4
Table 1 Screening of reaction conditions
OH
catalyst
O
O
solvent, temp.
Entry Solvent
Catalyst Oxidant Temp (°C) Yield (%)a
(mol%)
1
2
3
4
5
6
7
8
9
10
11
12
13
H2O
H2O
H2O
DMSO
CH3CN
H2O: CH3CN 15
DMF
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
10
20
15
15
20
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
Air
r.t
–
–
–
76
–
100
100
120
82
100
120
120
120
r.t
–
Fig. 5 SEM-EDX of CuFe2O4
15
15
–
15
15
15
12
68
76
–
Air
Air
Air
Air
Air
–
demands for sustainability. Therefore, we have studied the
possibility of recyclability of the catalyst. For this pur-
pose the reaction of 4-(trifluoromethyl) phenyl acetic acid
under optimized reaction conditions was selected (Fig S3,
ESI). After completion of the reaction the catalyst was
isolated from the reaction mixture by an external mag-
net, washed with diethyl ether and allowed to dry. After
drying it was reused directly for the next run. The results
indicated that the catalyst remained almost equally active
up to five consecutive cycles.
70
140
120
41
76
63
Phenyl acetic acid (1 mmol), Solvent (2–5 mL) catalyst (10–
20 mol%), time (12 h)
aIsolated yield, Bold indicates optimised condition
4 Conclusion
In summary, magnetically separable spinel CuFe2O4 nano-
catalyst has been prepared by co-precipitation method and
extensively characterized. The particle size distribution
calculated from TEM image showed narrow sized disper-
sion with an average particle size of 11 nm. The prepared
catalyst was found to be very efective for oxidative decar-
boxylation of phenylacetic acids to corresponding alde-
hydes and ketones. The easy magnetic separation of the
3.2 Proposed reaction mechanism of oxidative
decarboxylation
From the Scheme 1, it may be proposed that the pheny-
lacetic acid was decarboxylated to give an active copper
species with concomitant oxidation into corresponding
aldehyde via the peroxy cuprate [1, 29].
1 3

Spinel Structured Copper Ferrite Nano Catalyst with Magnetic Recyclability for Oxidative…
Table 2 Substrate scope for oxidative decarboxylation reaction catalysed by spinel CuFe2O4
OH
CuFe2O4
DMSO, 120oC
O
O
R
R
Entry
Substrate
Product
Time (h)
Yield (%) a
OH
1
12
76
O
O
O
OH
2
3
12
72
68
O
Cl
Cl
OH
14
O
O
OH
OH
Cl
OH
Cl
4
5
6
10
12
10
81
72
89
O
O
OH
O
O
Br
Br
OH
O
F
F
F
F
O
F
F
OH
OH
OH
7
8
10
10
12
10
82
81
60
91
O
O
O
O
O
O
O
Br
Br
9
O
O2N
O2N
COOH
O
10
O
O
OH
O
O
12
11
73
O
O
Reaction Conditions: Aryl acetic acid (1 mmol), catalyst (15 mol%), DMSO (2 mL), Temp (120°C)
aIsolated yield
catalyst from the reaction mixture eliminates the process
of fltration and could be reused up to ffth consecutive
cycle without remarkable loss in catalytic activity which
is an additional green attribute of this reaction.
1 3

T. Rahman et al.
Proposed reaction mechanism of oxidative decarboxylation
OH
CuFe2O4
air
Cu
OOCu
O
O
R
R
R
R
CO2
CuOH
Scheme 1 Proposed reaction mechanism of oxidative decarboxylation
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Sci 324:877
Acknowledgements The authors acknowledge the analytical services
provided by STIC Kochi, SAIF NEHU Shillong, CIF IIT Guwahati,
CSIC Dibrugarh University. The authors are also grateful to UGC,
New Delhi, India for the fnancial support under the scheme SAP-
DRS-I (2016-2021) and the Department of Science and Technology
for fnancial assistance under the DST-FIST program.
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38:1655
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65:277
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Afliations
Taskia Rahman1 · Geetika Borah1 · Pradip K. Gogoi1
1
* Geetika Borah
Department of Chemistry, Dibrugarh University, Dibrugarh,
geetikachem@yahoo.co.in
Assam, India
* Pradip K. Gogoi
dr.pradip54@gmail.com
Taskia Rahman
rahmantaskia@gmail.com
1 3