Spirulina (Arthrospira) platensis Supported Ionic Liquid as a Catalyst for the Synthesis of 3-Aryl-2-oxazolidinones from Carbon Dioxide, Epoxide, Anilines

Article abstract of DOI:10.1007/s10562-017-2217-z

Abstract: This study investigates the potential application of the (Ammonio)butane-1-sulfonate modified Spirulina (Arthrospira) platensis biomasses in the synthesis of 3-aryl-2-oxazolidinones from CO₂, ethylene oxide, and anilines. High catalytic activity and ease of recovery from the reaction mixture using filtration and several reuse times without significant losses in performance are additional eco-friendly attributes of this catalytic system. The effects of the structure of ionic liquid on the catalytic performance were investigated and the various reaction conditions were optimized. This observation was exploited in the direct and selective chemical fixation of CO₂, affording high degrees of CO₂ capture and conversion. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-017-2217-z

Catal Lett
DOI 10.1007/s10562-017-2217-z
Spirulina (Arthrospira) platensis Supported Ionic Liquid
as a Catalyst for the Synthesis of 3-Aryl-2-oxazolidinones
from Carbon Dioxide, Epoxide, Anilines
Seyed Mohsen Sadeghzadeh1 · Rahele Zhiani1,2 · Shokufe Emrani1,2
Received: 16 August 2017 / Accepted: 1 October 2017
© Springer Science+Business Media, LLC 2017
Abstract This study investigates the potential application
of the (Ammonio)butane-1-sulfonate modified Spirulina
(Arthrospira) platensis biomasses in the synthesis of 3-aryl-
2-oxazolidinones from CO2, ethylene oxide, and anilines.
High catalytic activity and ease of recovery from the reac-
tion mixture using filtration and several reuse times without
significant losses in performance are additional eco-friendly
attributes of this catalytic system. The effects of the structure
of ionic liquid on the catalytic performance were investi-
gated and the various reaction conditions were optimized.
This observation was exploited in the direct and selective
chemical fixation of CO2, affording high degrees of CO2
capture and conversion.
Graphical Abstract
Keywords Heterogeneous catalyst · One-pot synthesis ·
Green chemistry · Carbon dioxide
1 Introduction
CO2 is an easily accessible renewable carbon source, which
has the advantages of being nontoxic, abundant, and afford-
able. CO2 has been identified as a major contributor to these
emissions. One of the most important processes is incorpo-
ration of CO2 into epoxides to give five-membered cyclic
carbonates [1], which are widely used as starting compounds
for polycarbonate derivatives [2, 3] aprotic polar solvents [4],
electrolytes [5, 6], and lithium ion batteries. Nevertheless,
the formation of cyclic carbonates form oxiranes and carbon
* Seyed Mohsen Sadeghzadeh
seyedmohsen.sadeghzadeh@yahoo.com
1
Department of Chemistry, Faculty of Sciences, Neyshabur
Branch, Islamic Azad University, P.O. Box 97175-615,
Neyshabur, Iran
2
Young Researchers and Elite Club, Neyshabur Branch,
Islamic Azad University, P.O. Box 97175-613, Neyshabur,
Iran
Vol.:(0123456789)
1 3

S. M. Sadeghzadeh et al.
dioxide is an old reaction [7] and a number of inorganic and
organic compounds including amines, phosphanes, organo-
tin halides [8], transition metal complexes [9–12] mainly
salen complexes [13–15], organocatalysts [16], ionic liquid
[17, 18] and polymer grafted ionic liquid [19] are known to
catalyze this transformation. In this context, catalysis has
a crucial role, which is motivating a lot of research under
this topic [20–24]. Algae are naturally abundant and found
in all kinds of aquatic environment. Among algae species,
Spirulina platensis is a photosynthetic, filamentous, spiral-
shaped, multicellular, and bluegreen microalgae. Spirulina
filaments, may be easily separated from their medium, have
high digestibility, a mild flavor, and contain up to 70% excel-
lent quality protein [25]. Spirulina species are usually grown
in open systems, such as raceway ponds and in closed pho-
tobioreactors [26] for mass cultures. ILs are regarded as one
of the most attractive alternative for the CO2 cycloaddition
reaction and CO2 capture due to their unique properties and
high CO2 solubility. Most of the reported IL catalysts suf-
fer from necessary existence of toxic metal, the need of the
organic solvent, loss of cocatalyst during the recycling, and
inexhaustive separation from the products.
Scheme 1 Synthesis of 3-aryl-2-oxazolidinones in the presence of S.
platensis/IL
capillaries using an Electrothermal 9100 apparatus are
uncorrected. FTIR spectra was recorded on a VERTEX
70 spectrometer (Bruker) in the transmission mode in
spectroscopic grade KBr pellets for all the powders. NMR
spectra was recorded in CDCl3 on a Bruker Avance DRX-
400 MHz instrument spectrometer using TMS as internal
standard. The purity determination of the products and
reaction monitoring was accomplished by TLC on silica
gel polygram SILG/UV 254 plates.
3-Aryl-2-oxazolidinones are significant heterocyclic com-
pounds that have attracted attention due to their bioactivity.
The conventional conversions to 3-aryl-2-oxazolidinones are
through the reaction of phosgene with 2-alkamine [27] and
the reaction of isocyanate with epoxide [28–31]. The alter-
native synthetic conversions through the reaction of CO2
and aziridines are also reported [32–37]. Recently, Scientists
developed new approach for the one-pot conversion of CO2,
ethylene oxide (EO), and amines to 3-aryl-2-oxazolidinones
[38–42]. In light of the above-mentioned chemistry, the
development of new and efficient approaches for the syn-
thesis of these compounds, from simple, readily available
starting materials is desirable. Engaged in the development
of greener and sustainable pathways for organic transfor-
mations, nanomaterial, and nano-catalysis, here we report a
facile approach to prepare new catalyst for first time which
catalyzed the synthesis 3-aryl-2-oxazolidinones in aqueous
media. In this study, S. platensis biomass surface was modi-
fied with 4-(ammonio)butane-1-sulfonate (ABS), and used
for the synthesis 3-aryl-2-oxazolidinones from CO2, ethylene
oxide, and amines and then can be easily separated from the
reaction mixture to reuse (Scheme 1).
2.2 General Procedure for the Preparation of S.
platensis/IL
Spirulina platensis biomass was dried in a vacuum oven at
40 °C until constant weight, then ground and sieved into
fractions. The epichlorohydrin activated biomass (100 mg)
was added to water: ethanol mixture (10:10 v/v, 100 mL)
containing 1,4-butanesultone (2.5 g), and the reaction was
carried out at room temperature for 2.0 h. After the sol-
vent was removed, the resulting mixture was filtered, after
which the filtrate was dried under vacuum at 50 °C.
2.3 General Procedures for Preparation
of 3-aryl-2-Oxazolidinone
In a 100 ml stainless-steel reactor, an appropriate CO2
(1.0 MPa), aniline (1.0 mmol), and ethylene oxide
(10 mmol) were added to a catalyst (1 mg) at room tem-
perature. Then, the temperature was raised to 100 °C with
the addition of CO2 from a reservoir tank to maintain a
constant pressure (2.0 MPa). The remaining CO2 was
removed slowly. After reaction, the catalyst was separated
by filtration under vacuum and reused for further recycling
experiment. The crude product mixture was dried over
anhydrous sodium sulphate, and then subjected to column
chromatography using a 6:1 petroleum ether/EtOAc eluent
system on silica gel to give cyclic carbonate as a colorless
liquid.
2 Experimental
2.1 Materials and Methods
Chemical materials were purchased from Fluka and Merck
in high purity. Melting points were determined in open
1 3

Spirulina (Arthrospira) platensis Supported Ionic Liquid as a Catalyst for the Synthesis…
2.4 Spectral Data of Synthesized Compounds
2.4.1 3‑Phenyl‑2‑oxazolidinone (Compound 1a)
1H NMR δ = 7.57–7.54 (m, 2H), 7.38–7.35 (m, 2H),
7.10–7.08 (m, 1H), 4.51–4.48 (m, 2H), 4.05–3.99 (m, 2H)
ppm; 13C NMR δ=155.6, 138.2, 128.9, 124.3, 118.6, 61.5,
Scheme 2 Schematic illustration of the synthesis for S. platensis/IL
45.1 ppm.
2.4.2 3‑(4‑Chlorophenyl)oxazolidin‑2‑one (Compound 1b)
1H NMR δ = 7.50–7.46 (m, 2H), 7.36–7.34 (m, 2H),
4.49–4.46 (m, 2H), 4.03–3.99 (m, 2H) ppm; 13C NMR
δ=155.3, 136.9, 129.5, 129.1, 119.4, 61.2, 45.3 ppm.
2.4.3 3‑(4‑Bromophenyl)oxazolidin‑2‑one (Compound 1c)
1H NMR δ = 7.50–7.43 (m, 4H), 4.48–4.42 (m, 2H),
4.04– 4.00 (m, 2H) ppm; 13C NMR δ=155.3, 137.6, 132.2,
120.0, 116.9, 61.3, 45.2 ppm.
2.4.4 3‑p‑Tolyloxazolidin‑2‑one (Compound 1d)
1H NMR δ = 7.41 (d, J = 8.4 Hz, 2H), 7.15 (d, J = 8.4 Hz,
2H), 4.45–4.39 (m, 2H), 4.01–3.97 (m, 2H), 2.29 (s, 3H)
ppm; 13C NMR δ=155.6, 135.7, 133.5, 129.4, 118.2, 61.4,
45.1, 21.0 ppm.
Fig. 1 FTIR spectra of a S. platensis, and b S. platensis/IL
which features with easy accessibility of active sites and
high catalytic activity, was synthesized by a simple, cost-
effective procedure.
2.4.5 3‑(4‑Methoxyphenyl)oxazolidin‑2‑one (Compound
The FT-IR spectra of S. platensis and S. platensis/IL are
presented in Fig. 1. The peaks at 3394, 2925, 1663, 1353,
1031, and 578 cm− 1 are observed in the spectrum of the
native algal biomass (Fig. 1a). The band at 1118 cm−1 can
be assigned to the stretching vibrations of S=O bonds. Two
peaks at 1656 and 1502 cm−1 for N-H bending vibrations in
the ammonium groups (Fig. 1b).
1e)
1H NMR δ = 7.42 (d, J = 9.2 Hz, 2H), 6.89 (d, J = 9.2 Hz,
2H), 4.45 (t, J=8.0 Hz, 2H), 3.99 (t, J=8.0 Hz, 2H), 3.76
(s, 3H) ppm; 13C NMR δ=156.4, 155.7, 131.7, 120.5, 114.3,
61.4, 55.7, 45.9 ppm.
To investigate the change of S. platensis biomass surface
charge before and after the surface modification protocols,
the zeta potentials as a function of solution pH (i.e. between
2.0 and 12.0) were measured. The modification protocols
are schematically presented in Fig. 2. To investigate the
change of S. platensis biomass surface charge before and
after the surface modification protocols, the zeta potentials
as a function of solution pH were measured using native,
and 4-(ammonio)butane-1-sulfonate (ABS)-modified algal
biomasses. As observed in this figure, the zeta potential
values for native and modified algal biomass decrease with
increasing solution pH. The zero zeta potential point value
for native algal biomass was found to be at pH 4.0; on the
other hand, the zero potential values for ABS-modified algal
biomass was observed at pH 10. The positive charge density
on the 4-(ammonio)butane-1-sulfonate modified biomass
surface significantly decreased with increasing medium pH
2.4.6 3‑(4‑Ethoxyphenyl)oxazolidin‑2‑one (Compound 1f)
1H NMR δ = 7.43–7.39 (m, 2H), 6.91–6.87 (m, 2H),
4.47–4.43 (m, 2H), 4.06–4.01 (m, 4H), 1.39 (t, J=7.0 Hz,
3H) ppm; 13C NMR δ=156.0, 155.8, 131.3, 120.4, 114.9,
63.7, 61.6, 45.8, 15.0 ppm.
3 Results and Discussion
The synthesis of S. platensis/IL nanocatalysts involved
several steps (Scheme 2). The structure of S. platensis has
many –NH2 groups on the surfaces; thus, it was expected
that the S. platensis could be easily functionalized with
1,4-butanesultone to form S. platensis/IL. S. platensis/IL,
1 3

S. M. Sadeghzadeh et al.
Table 1 Synthesis of 3-aryl-2-oxazolidinone by S. platensis/IL in
different solvents
Entry
Solvent
Time (h)
Yield (%)a
1
2
EtOH
H2O
2
2
–
–
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
CH3CN
DMF
CH2Cl2
EtOAc
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1.5
1
0.5
39
25
33
36
38
49
–
35
39
–
–
–
51
98
98
86
50
THF
Toluene
n-Hexane
CHCl3
DMSO
MeOH
Dioxane
i-PrOH
anisole
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Fig. 2 pH versus zeta potential plots for the native, and S. platensis/
IL
due to the deprotonation of the amine groups on the ligand
molecules. The charge density in this pH range changed
from −29.9 to 8.7 mV for native algal biomass. On the other
hand, for 4-(ammonio)butane-1-sulfonate modified algal
preparation, it changed from −17.9 to 33.1 mV.
To optimize the reaction conditions, the aniline, carbon
dioxide and epoxide was used for the sythesis 3-aryl-2-ox-
azolidinone in the presence of S. platensis/IL as a catalyst
was chosen as a model system. The effect of various param-
eters such as solvent, and time (Table 1) were examined on
the model reaction. To investigate the effect of solvents for
the sythesis 3-aryl-2-oxazolidinone, different solvents have
been used (Table 1, Entries 1–15) and the obtained results
reveal that when the polar protic solvents, such as methanol,
isopropanol, ethanol, and water are used, the expected prod-
uct is not formed. However, the yield of the crosscoupling
product was relatively average in polar aprotic solvents, such
as DMF, EtOAc, and DMSO. In this study, it was found that
conventional heating under solvent free condition is more
efficient than using solvents (Table 1, Entries 16). When
the reaction was conducted in less polar solvents, such as
anisole or toluene, average yields of carbonylative cross-
coupling product were isolated. However, the carbonylative
cross-coupling product was obtained in low yield in polar
solvents. In this study, it was found that conventional heat-
ing under solvent free is more efficient than using solvents
(Table 1, Entries 16). Under the optimal conditions, the reac-
tion progress for the shortest time necessary in the presence
of 1 mg of of S. platensis/IL was monitored by GC, that
excellent yields of synthesis of 3-aryl-2-oxazolidinone can
be achieved in 1.5 h (Table 1, Entries 17).
Reaction conditions: appropriate CO2 (1.0 MPa), aniline (1.0 mmol),
ethylene oxide (10 mmol), S. platensis/IL (1 mg), solvent (10 mL),
and CO2 1.5 MPa, at 100 °C
aIsolated yields
3-aryl-2-oxazolidinone yield increased up to 98% at 100 °C
under 2.0 MPa CO2 pressure over 1.5 h. Whereas further
increase in the temperature resulted in a slight decrease in
the product yield due to formation of a small amount of by-
products, such as the propylene oxide isomerization. There-
fore, the optimal temperature for the coupling reaction of
CO2, aniline, and ethylene oxide are 100 °C.
As shown in Fig. 4, the CO2 pressure also has a signifi-
cant effect on the coupling reaction. The reaction rate was
accelerated quickly in the range 0.8–1.0 MPa. However,
100
90
80
70
60
50
40
30
20
10
0
To optimize reaction conditions for the S. platensis/IL
catalyst system, the effects of various reaction param-
eters were investigated. The influence of temperature on
this reaction is exhibited in Fig. 3. It is obvious that the
20
40
60
80
100
120
Temperature oC
Fig. 3 Effect of temperature on yield of 3-aryl-2-oxazolidinone
1 3

Spirulina (Arthrospira) platensis Supported Ionic Liquid as a Catalyst for the Synthesis…
100
yields. Therefore, the CO2 pressure of 1.0 MPa was con-
90
80
70
60
50
40
30
20
10
0
sidered as suitable condition.
In order to study the efficiency and general applicability
of the catalyst S. platensis/IL, the synthesis of 3-aryl-2-ox-
azolidinone with various anilines under optimized reaction
conditions was studied and the results were listed in Table 2.
It can be seen that this catalyst was efficient for all reactions
proceeded smoothly providing appreciable yield of desired
product.
A plausible mechanism for the catalytic synthesis of
3-aryl-2-oxazolidinone is shown in Scheme 3. Initially, the
catalyst activates aniline. Subsequent nucleophilic attack on
ethylene oxide to give the intermediate (A). On the other
hand, the catalyst activates ethylene oxide, which attack on
carbon dioxide to give the intermediate (B). Intermediate
(A) reacts with intermediate (B) to give intermediate (C).
Finally, ring closure gives the 3-aryl-2-oxazolidinone.
Moreover, the more important investigations about the
recovery and reuse of the S. platensis/IL catalyst were per-
formed (Fig. 5). The activity of S. platensis/IL was moni-
tored by the yield of this cycloaddition reaction under the
optimal conditions. In every run, the catalyst was separated
from the reaction mixture, and directly reused for subse-
quent reaction under the optimized reaction conditions.
From Fig. 5, it can be seen clearly that the catalyst could be
reused for four times at least and no significant drop in the
yield of 3-aryl-2-oxazolidinone, indicating high stability of
S. platensis/IL.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
CO2 Pressure (MPa)
Fig. 4 Effect of CO2 pressure on the synthesis of 3-aryl-2-oxazolid-
inone
Table 2 Synthesis of 3-aryl-2-oxazolidinone derivatives catalyzed by
S. platensis/IL
Entry
R
Product
Yield (%)a
1
2
3
4
5
6
H
Cl
Br
Me
MeO
EtO
3a
3b
3c
3d
3e
3f
98
95
93
95
91
94
Reaction condition: aniline derivatives (1.0 mmol), and ethylene
oxide (10 mmol), S. platensis/IL (1 mg), CO2 1 Mpa, 1.5 h and at
100 °C
aYield refers to isolated product
4 Conclusions
the yield decreased when the pressure reached 1.6 MPa.
Based on these report, it can be inferred that increas-
ing reaction pressure was propitious to produce 3-aryl-
2-oxazolidinone when the reaction pressure was less than
1.6 MPa. Too high pressures would reduce the propylene
oxide concentration to give low 3-aryl-2-oxazolidinone
In summary, we have successfully developed a novel, sim-
ple, environmentally benign and highly active catalyst sys-
tem of S. platensis/IL for the synthesis of 3-aryl-2-oxazo-
lidinone under solvent-free condition. The structure of S.
platensis has many –NH2 groups on the surfaces; thus, it
O
+
S
+
H2
H2
O
O
Intermediate (A)
N
O
-O
+
N
H2
N
O
S
O-
H
N
O
S
O-
OH
H
N
O
O
O
H
O
S
O-
O
O
O
+
H
H2
N
N
OH
O
O
O
Intermediate (B)
N
O
+
H2
Intermediate (C)
+
H2
N
N
O
O
S
O-
S
O
O-
O-
O
O
O
C
O
O
O
Scheme 3 Reaction mechanism
1 3

S. M. Sadeghzadeh et al.
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