Synthesis of 2,5-dihydro-3-furans using nano-CoAl2O4

Article abstract of DOI:10.1007/s11164-021-04463-1

Nano-CoAl₂O₄ has been used as an efficient catalyst for the preparation of 5-oxo-2,5-dihydro-3 furancarboxylates by multi-component reactions of phenylglyoxal, dimethyl acetylenedicarboxylate and primary amines. The best results were

Full text of DOI:10.1007/s11164-021-04463-1

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-021-04463-1
Synthesis of 2,5‑dihydro‑3‑furans using nano‑CoAl2O4
Seyyed Mohammad Ebrahimi1 · Ali Kareem Abbas2 ·
Hossein Shahbazi‑Alavi3 · Javad Safaei‑Ghomi1
Received: 18 January 2021 / Accepted: 5 April 2021
© The Author(s), under exclusive licence to Springer Nature B.V. 2021
Abstract
Nano-CoAl2O4 has been used as an efcient catalyst for the preparation of 5-oxo-
2,5-dihydro-3 furancarboxylates by multi-component reactions of phenylglyoxal,
dimethyl acetylenedicarboxylate and primary amines. The best results were obtained
in the presence of 4 mg of nano-CoAl2O4 in CH2Cl2 at room temperature. The struc-
1
tures of the products were deduced from their H NMR, 13C NMR, FT-IR and ele-
mental analyses. Experimental simplicity, wide range of products, great yields in
concise times, the retrievable of the nanocatalyst and low catalyst loading are some
of the substantial features of this method.
Graphic abstract
O
O
O
CO2Me
CO2Me
O
H
nano-CoAl2O4
CH2Cl2
R1NH2
+
+
MeO2C
R1
O
N
H
3
2
1
4a-4h
Keywords Phenylglyoxal · Nanocatalyst · One-pot · Furancarboxylate
*
Hossein Shahbazi-Alavi
hosseinshahbazi99@yahoo.com
1
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan 51167,
Islamic Republic of Iran
2
3
College of Applied Medical Sciences, University of Kerbala, Kerbala, Iraq
Young Researchers and Elite Club, Kashan Branch, Islamic Azad University, Kashan,
Islamic Republic of Iran
Vol.:(0123456789)
1 3

S. M. Ebrahimi et al.
Introduction
Furans show anti-oxidation [1], antibacterial, [2], antimalarial [3], anticancer [4],
anti-AIDS [5], anti-infammatory [6] and anti-diabetic [7] activities. The detection
efective procedure for the synthesis of furans is a serious challenge. The prepara-
tion of furans has been studied using catalysts including K[Al(SO4)2]0.12H2O [8],
N-methyl 2-pyrrolidonium hydrogen sulfate [9], formic acid [10], SnCl2·2H2O [11],
β-cyclodextrin [12], tetra-n-butylammonium bisulfate [13], Al(HSO4)3 [14], HY
Zeolite [15] and Vitamin B12 [16]. Each of these catalysts may have its own advan-
tages but also sufer from such apparent drawbacks as high times [12–14], compli-
cated work-up [12], low efciency [12, 16], or unwanted reaction conditions [11,
15]. Despite the use of these procedures, there remains a need for further new meth-
ods for the preparation of furans. Cobalt(II) compounds have been used extensively
as a heterogeneous catalyst in many reactions, containing synthesis of hexahydro-
quinolines [17], soot combustion with NOx/O2 [18], Fischer–Tropsch synthesis [19]
combination CO2 reforming [20] and annulation of styrenes with α-bromoacetic
acids [21]. Cobalt(II) aluminate has many advantages containing good selectivity
with high stability, reusability and easy recyclability [22, 23]. Recently, nanopar-
ticles as catalyst have appeared as an alternative way for the progression of many
organic reactions [24–26]. Herein, we report the use of nano-CoAl2O4 as an efcient
catalyst for the preparation of furans by multi-component reactions of phenylgly-
oxal, dimethyl acetylenedicarboxylate and primary amines (Scheme 1).
Experimental section
Materials and characterization
Reagent grade chemicals were purchased from Sigma-Aldrich and Merck and were
used without further purifcation. All melting points were determined in a capillary
tube on Boetius melting point microscope. NMR spectra were obtained on Bruker
400 MHz spectrometer with CDCl3 as solvent using tetramethylsilane (TMS) as an
internal standard, the chemical shift values are in δ. FT-IR spectrum was recorded on
Magna-IR, spectrometer 550 Nicolet in KBr pellets in the range of 400–4000 cm−1.
The elemental analysis (C, H, N) was obtained from a Carlo ERBA Model EA 1108
O
O
O
CO2Me
CO2Me
O
H
nano-CoAl2O4
CH2Cl2
R1NH2
+
+
MeO2C
R1
O
N
H
3
2
1
4a-4h
Scheme 1 Synthesis of furans catalyzed by nano-CoAl2O4
1 3

Synthesis of 2,5-dihydro-3-furans using nano-CoAl2O4
analyzer. Powder X-ray difraction (XRD) was carried out on a Philips difractom-
eter of X’pert Company with mono-chromatized Cu Kα radiation (λ=1.5406 Å).
The SEM images were prepared by MIRA3- TESCAN. The energy-dispersive X-ray
spectroscopy (EDS) measurement was carried out with the SAMX analyzer. Surface
area was carried out using nitrogen adsorption measurement (Micrometrics ASAP-
2000). DLS was performed using a Malvern apparatus.
Synthesis of nano‑CoAl2O4
CoAl2O4 was synthesized using sol–gel technique by citric acid. At frst, a deter-
mined amount of Al(NO3)3·9H2O (0.10 mol) and Co(NO3)2·6H2O (0.05 mol) was
solved in deionized water (100 mL). Afterward, an appropriate amount of citric acid
was added (molar ratio of citric acid to metal ions was 2–1). Subsequently, the solu-
tion was stirred for 60 min and heated at 80 °C until a gel was created. The gel was
dried in oven at 110 °C and fred at 500 °C with a heating rate of 10 K/min for 5 h
in air.
General procedure for the preparation of furans (4a–h)
A mixture of amine (1 mmol) dimethyl acetylenedicarboxylate (1 mmol), phenylgly-
oxal (1 mmol) and nano-CoAl2O4 (4 mg) was stirred in dichloromethane (10 mL) at
room temperature. After completion, as indicated by TLC (EtOAc-petroleum ether,
2:8), the nanocatalyst was separated from the mixture using fltration. The solvent
was evaporated under vacuum and the product (Yellow oil) was washed with ethanol
to give pure product. The characterization data of the compounds are given below.
Methyl 2‑benzoyl‑4‑[(2‑methoxybenzyl)
amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate (4a)
Yellow oil, FT-IR (KBr): 3402, 3052, 3004, 1771, 1705, 1675, 1604, 1476,
1
1122 cm−1; H NMR δ 8.04–6.92 (m, 9H, ArH), 6.25 (s, 1H, CH), 5.02–4.95 (m,
2H, CH2), 3.87, 3.56 (2 s, 6H, 2MeO), 2.20 (s, 1H, NH). 13C NMR δ 192.4, 164.5,
164.4, 157.3, 136.4, 135.2, 129.5, 129.4, 128.4, 128.1, 127.4, 126.7, 124.3, 110.6,
105.3, 76.1, 56.9, 52.5, 42.8. Anal. Calcd. for C21H19NO6: C 66.13, H 5.02, N 3.67.
Found: C 66.16, H 4.95, N 3.71.
Methyl 2‑benzoyl‑4‑[(4‑methoxybenzyl)
amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate (4b)
Yellow oil, FT-IR (KBr): 3302, 3105, 3006, 1752, 1702, 1675, 1602, 1478, 1468,
1379, 1102 cm−1; 1H NMR δ 8.09–6.92 (m, 9H, ArH), 6.42 (s, 1H, CH), 4.92–4.80
(m, 2H, CH2), 3.84, 3.52 (2 s, 6H, 2MeO), 2.69 (s, 1H, NH), 13C NMR δ 192.6,
169.1, 162.4, 159.2, 156.4, 155.2, 154.1, 153.2, 135.2, 135.1, 107.2, 105.4, 76.1,
60.2, 57.4, 44.6. Anal. Calcd. for C21H19NO6: C, 66.13; H, 5.02; N, 3.67;. Found: C,
66.17; H, 5.08; N, 3.74.
1 3

S. M. Ebrahimi et al.
Methyl 2‑benzoyl‑4‑[(4‑methylbenzyl)amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate
(4c)
Yellow oil, FT-IR (KBr): 3455, 3054, 3005, 1738, 1704, 1605, 1473,1468,
1
1105 cm−1; H NMR δ 8.06–7.10 (m, 9H, ArH), 6.25 (s, 1H, CH), 4.82–4.92 (m,
2H, CH2), 3.65 (s, 3H, OCH3), 2.95 (s, 1H, NH), 2.28 (s, 3H, CH3). 13C NMR δ
192.8, 168.2, 164.7, 138.2, 137.5, 136.7, 130.2, 129.8, 128.4, 127.8, 127.5, 127.4,
105.6, 76.1, 50.2, 48.6, 22.4. Anal. Calcd. for C21H19NO5: C 69.03, H 5.24, N 3.83.
Found: C 69.09, H 5.20, N 3.89.
Methyl 2‑benzoyl‑4‑(benzylamino)‑ 5‑oxo‑2,5 dihydro‑3‑furancarboxylate (4d)
Yellow oil, FT-IR (KBr): 3455, 3058, 3004, 1752, 1706, 1608, 1477, 1155 cm−1;
1HNMR δ 8.35–7.12 (m, 10H, arom), 6.19 (s, 1H, CH), 4.94–4.90 (m, 2H, CH2),
3.57 (s, 3H, OCH3), 2.60 (s, 1H, NH). 13C NMR δ 193.9, 169.8, 166.2, 138.2, 137.9,
137.6, 135.2, 129.8, 128.6, 128.5, 128.4, 128.3, 105.4, 76.1, 50.2, 46.9. Anal. Calcd.
for C20H17NO5: C 68.37, H 4.88, N 3.99. Found: C 68.30, H 4.80, N 4.03.
Methyl‑2‑benzoyl‑4‑[(4‑fuorobenzyl)amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate
(4e)
Yellow oil, FT-IR (KBr): 3405, 3075, 3008, 1772, 1754, 1708, 1606, 1478,
1
1155 cm−1; H NMR δ 8.19–6.50 (m, 9H, arom), 6.84 (s, 1H, CH), 4.90–4.82 (m,
2H, CH2), 3.51 (s, 3H, OCH3), 2.62 (s, 1H, NH). 13C NMR δ 192.3, 169.8, 167.2,
139.8, 138.2, 138.1, 132.2, 131.4, 129.4, 129.2, 125.6, 118.4, 104.8, 76.2, 51.4,
47.4. Anal. Calcd. for C20H16FNO5: C 65.04, H 4.37, N 3.79. Found: C 65.01, H
4.31, N 3.82.
Methyl 2‑benzoyl‑5‑oxo‑4‑(propylamino)‑2,5 dihydro‑3‑furancarboxylate (4f)
Yellow oil, yield: FT-IR (KBr): 3352, 3055, 3004, 2972, 1776, 1702, 1652, 1474,
1
1122 cm−1; H NMR δ 8.15–7.25 (m, 5H, ArH), 6.32 (s, 1H, CH), 3.74 (t, J=7.0,
2H, CH2), 3.62 (s, 3H, OCH3), 2.42 (s, 1H, NH), 1.66–1.60 (m, 2H, CH2), 0.92
(t, J=7.0, 3H, CH3). 13C NMR δ 193.4, 168.2, 165.4, 135.4, 129.8, 129.4, 128.8,
126.5, 105.8, 76.2, 53.5, 51.2, 24.2, 12.8. Anal. Calcd. for C16H17NO5: C 63.36, H
5.65, N 4.62. Found: C 63.30, H 5.69, N 4.56.
Methyl‑2‑benzoyl‑4‑[((furan‑2‑yl)methane)
amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate (4g)
Yellow oil, FT-IR (KBr): 3408, 3070, 3002, 1770, 1754, 1703, 1604, 1475,
1
1152 cm−1; H NMR δ 8.29–7.02 (m, 8H, ArH), 6.24 (s, 1H, CH), 4.98–4.90 (m,
2H, CH2), 3.52 (s, 3H, OCH3), 2.40 (s, 1H, NH). 13C NMR δ 192.5, 168.9, 163.2,
151.4, 142.6, 138.4, 137.8, 136.5, 129.8, 129.6, 128.5, 112.6, 110.5, 76.2, 51.2,
40.4. Anal. Calcd. for C18H15NO6: C 63.34, H 4.43, N 4.10, Found: C 63.28, H 4.38,
N 4.02.
1 3

Synthesis of 2,5-dihydro-3-furans using nano-CoAl2O4
Methyl‑2‑benzoyl‑4‑[(3,4‑dichlorobenzyl)
amino]‑5‑oxo‑2,5‑dihydro‑3‑furancarboxylate (4h)
Yellow oil, FT-IR (KBr): 3505, 3045, 3014, 1754, 1708, 1612, 1479, 1158 cm−1;
1HNMR δ 8.35–7.12 (m, 8H, ArH), 6.25 (s, 1H, CH), 4.94–4.90 (m, 2H, CH2), 3.57
(s, 3H, OCH3), 2.90 (s, 1H, NH). 13C NMR δ 192.1, 168.4, 165.7, 141.2, 139.4,
138.2, 137.8, 137.2, 136.1, 135.4, 131.2, 131.0, 129.6, 128.1, 107.6, 76.1, 52.4,
45.7. Anal. Calcd. for C20H15Cl2NO5: C, 57.16; H, 3.60; N, 3.33;. Found: C, 57.10;
H, 3.52; N, 3.28.
Results and discussion
XRD of nano-CoAl2O4 is presented in Fig. 1. This shape displays excellent phase
purity of nano-CoAl2O4 that has a complete agreement with the recorded XRD for
nano-CoAl2O4 (spinel-type structure, JCPDS 44-0160) [18]. Average crystalline
size of the nano-CoAl2O4 using Scherrer’s formula was computed to be 15–25 nm.
The BET surface area of the nano-CoAl2O4 catalyst was obtained 75 m2/g.
The size and morphology of nano-CoAl2O4 was considered using SEM (scanning
electron microscope) image (Fig. 2). The results display particles with diameters in
the size of nanometers. The size distribution of nano-CoAl2O4 was determined using
DLS measurements, (Fig. 3) that is centered at a value of 37.5 nm. The elemental
composition of nano-CoAl2O4 was investigated by EDS (Energy-Dispersive X-ray
Spectroscopy) (Fig. 4) that showed the cobalt, aluminium and oxygen in the nano-
CoAl2O4 structure.
At frst, to fnd the optimum conditions, the one-pot reaction of 2-methoxyben-
zylamine, dimethyl acetylenedicarboxylate and phenylglyoxal in the presence of
the diverse catalysts and solvents was selected as model reaction for the prepara-
tion of 5-oxo-2,5-dihydro-3-furancarboxylates. Several reactions were scrutinized
using various solvents such as EtOH, CH3CN, DMF, CHCl3 and CH2Cl2. In this
reaction, the use of aprotic solvents favors the reaction mechanism. The model
reaction was carried out in the presence of various catalysts such as Et3N (base),
p-TSA (acid), ZrO2, InCl3, Co3O4, nano-CuI, nano-ZnO and nano-CoAl2O4.
Fig. 1 XRD of nano-CoAl2O4
1 3

S. M. Ebrahimi et al.
Fig. 2 SEM image of CoAl2O4 nanoparticle
Fig. 3 DLS of nano-CoAl2O4
When the reaction was carried out using nano-CuI, Co3O4 and nano-CoAl2O4
as the catalyst, the product could be obtained in moderate to good yield and
short times. As expected, the increased surface area due to small particle size
increased reactivity of catalyst. The best results were gained in dichloromethane,
and we found that the reaction gave convincing results in the presence of nano-
CoAl2O4 (4 mg) at room temperature (Table 1). In the cases that the yield was not
1 3

Synthesis of 2,5-dihydro-3-furans using nano-CoAl2O4
Fig. 4 EDS of nano-CoAl2O4
Table1 Optimization of reaction conditionsa
Entry
Solvent
Catalyst (amount)
Time (min)
Yieldb (%)
1
2
3
4
5
6
7
8
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH3CN
CHCl3
DMF
–
300
300
300
300
300
150
200
200
50
50
50
90
60
11
43
26
15
31
62
52
39
85
93
93
50
82
60
38
Et3N (10 mol%)
ZrO2(6 mol%)
p-TSA (10 mol%)
InCl3 (7 mol%)
Co3O4 (5 mol%)
Nano-CuI (5 mg, 4 mol%)
Nano-ZnO (7 mg, 5 mol%)
Nano-CoAl2O4 (2 mg, 1 mol%)
Nano-CoAl2O4 (4 mg, 2 mol%)
Nano-CoAl2O4 (6 mg, 3 mol%)
Nano-CoAl2O4 (6 mg, 3 mol%)
Nano-CoAl2O4 (6 mg, 3 mol%)
Nano-CoAl2O4 (6 mg, 3 mol%)
Nano-CoAl2O4 (6 mg, 3 mol%)
9
10
11
12
13
14
15
90
140
EtOH
aReaction conditions: 2-methoxybenzylamine (1 mmol) dimethyl acetylenedicarboxylate (1 mmol), phe-
nylglyoxal (1 mmol)
bIsolated yield
satisfactory (Entry 1, 3, 4, 5 and 8), it was observed the presence of by-products
and the recovering of the starting materials. After that, the obtained optimal con-
ditions were applied to perform the reaction of diferent primary amines in the
presence of nano-CoAl2O4 as catalyst, in order to aford the corresponding prod-
ucts in high to excellent yields (Table 2).
1 3

S. M. Ebrahimi et al.
a
Table 2 Synthesis of 5-oxo-2,5-dihydro-3-furancarboxylates using nano-CoAl2O4
Entry
Primary amine
Product
Time (min)
Yield b
%
O
O
O
NH2
MeO2C
OCH3
OCH3
NH
50
93
1
3a
4a
O
NH2
O
O
MeO2C
2
NH
50
60
70
91
OCH3
OCH3
3b
4b
O
NH2
O
O
MeO2C
NH
89
88
3
4
CH3
CH3
3c
4c
O
NH2
O
O
MeO2
C
NH
3d
4d
O
NH2
O
O
MeO2C
NH
70
83
5
F
3e
F
4e
4f
O
O
O
CH3CH2CH2NH2
MeO2C
70
70
82
86
NH
CH2CH2CH3
6
7
3f
O
O
O
O
MeO2C
NH2
NH
O
3g
4g
O
Cl
H2
N
O
O
Cl
MeO2C
NH
8
3h
Cl
Cl
70
84
4h
1 3

Synthesis of 2,5-dihydro-3-furans using nano-CoAl2O4
Table 2 (continued)
aReaction conditions: primary amines (1 mmol) dimethyl acetylenedicarboxylate (1 mmol), phenylgly-
oxal (1 mmol)
bIsolated yield
The reusability of nanocatalyst was studied for the model reaction, and it was
found that product yields lessened only to a very small extent on each reuse (run 1,
93%; run 2, 93%; run 3, 92%; run 4, 92%; run 5, 91%, run 6, 91%). After comple-
tion of the reaction (as determined by TLC), CH2Cl2 was added. The nano-CoAl2O4
was insoluble in CH2Cl2, and it could therefore be obtained by simple fltration. The
catalyst was washed four times with ethanol and dried at room temperature for 15 h
prior to re-use.
Scheme 2 shows a plausible mechanism for this reaction in the presence of nano-
CoAl2O4. At frst, the nucleophilic attack by the amine on dimethyl acetylenedicar-
boxylate generates the aminobutendioate I as an electron-rich enaminone. Subse-
quent nucleophilic attack of aminobutendioate I to the aldehyde carbonyl group of
the phenylglyoxal would yield iminium–oxoanion intermediate II, which can be tau-
tomerized to intermediate III. γ-Lactonization of intermediate III would produce
the 5-oxo-2,5-dihydro-3-furancarboxylates.
O
H
H
N+ R1
O
O
MeO2C
H
H
CO2Me
CO2Me
N
R1
MeO2C
-
R1NH2
+
CO2Me
H
O
H
CO2Me
I
II
O
O
H
O
N
R1
MeO2C
O
-MeOH
MeO2C
N
R1
CO2Me
H
H
HO
=
nano-CoAl2O4
III
Scheme 2 Proposed reaction pathway for the synthesis of 4a–h
1 3

S. M. Ebrahimi et al.
Conclusions
In conclusion, our procedure uses nano-CoAl2O4 at room temperature in dichlorometh-
ane for the synthesis of 5-oxo-2,5-dihydro-3-furancarboxylates. The structures of the
products were deduced from their 1H NMR, 13C NMR, FT-IR and elemental analyses.
The salient features of this protocol are: great yields in concise times, retrievability of
the nanocatalyst, little nanocatalyst loading and easy separation of products.
Supporting information
The copies of the H NMR spectra of products are given in the Supporting Information
available online.
Supplementary information The online version contains supplementary material available at https://doi.org/
10.1007/s11164-021-04463-1.
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