Fixing CO2 into β-oxopropylcarbamates in neat condition by ionic gelation/Ag(i) supported on dendritic fibrous nanosilica

Article abstract of DOI:10.1039/c9ra02680k

In this research, a novel approach to produce a novel nanocatalyst, AgBr supported on an ionic gelation (IG)-based nanomaterial, was developed through the aqueous coprecipitation approach for the dendritic fibrous nanosilica (DFNS) production and the wet

Full text of DOI:10.1039/c9ra02680k

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Fixing CO into b-oxopropylcarbamates in neat
2
condition by ionic gelation/Ag(I) supported on
Cite this: RSC Adv., 2019, 9, 16955
dendritic fibrous nanosilica†
Liping Chang,* Rahele Zhiani and Seyed Mohsen Sadeghzadeh *b
a
b
In this research, a novel approach to produce a novel nanocatalyst, AgBr supported on an ionic gelation
(IG)-based nanomaterial, was developed through the aqueous coprecipitation approach for the dendritic
fibrous nanosilica (DFNS) production and the wet impregnation method for IG coating, taking into
account TPP as the cross-linking agent. In addition, DFNS/IG@Ag(I) had heterogeneous features that
contributed to the quick improvement of the catalyst by filtration separation. The catalytic activity of
DFNS/IG@Ag(I) was examined to synthesize b-oxopropylcarbamates through a multicomponent coupling
Received 10th April 2019
Accepted 12th May 2019
2
of CO , amines and propargyl alcohols in moderate conditions. The DFNS/IG@Ag(I) NPs were completely
investigated by taking advantage of TG, TEM, FESEM and FT-IR spectroscopy analyses. The DFNS/
IG@Ag(I) nanocatalyst indicated high stability in the reaction for five cycles without considerable loss of
some properties like activity, which could be because of the high loading of IG on the catalyst surface.
DOI: 10.1039/c9ra02680k
rsc.li/rsc-advances
greatly facilitate the making of C–N and C–C bonds in organic
production. These properties of CO may be ascribed to its kinetic
2
Introduction
Algae exist in abundance in most kinds of aquatic environments. inertness and great stability in terms of thermodynamic proper-
Among the different kinds of algae, spirulina is a type of blue- ties. Recently, a signicant approach has been obtained in this
green, photosynthetic, multicellular, lamentous, as well as subject, which is the use of CO to produce different organic
2
spiral-shaped microalgae. Spirulina laments, easily separated compounds such as amides, esters, alcohols, carbonates and
from their medium, has 70% great quality protein, a good avor, carboxylic acids as well as carbamates. This has been favored by
and great digestibility. Spirulina contains reactive functional different efficient catalytic approaches. Considerable progress has
groups like amino and hydroxyl, which are toxic, sensitive to pH, been made, and several approaches have been developed in the
2
and biocompatible, and can be added to metals. Ionic gelation is case of the reaction of CO to produce products such as cyclic
one of the important approaches utilized to produce chitosan carbonates and urethanes as well as salicylic acid. One of these
1,2
nanoparticles. The interpolation of NPs within a network composites, namely, carbamates, is an important and diverse
comprising of amino and hydroxyl groups by utilizing a poly- composite. Thus, utilizing carbon dioxide to develop an eco-
3–7
anionic cross-linker like tripolyphosphate or TPP facilitates the friendly approach that efficiently yields carbamates is attrac-
8–39
interplay of the NPs with the cationic spirulina through electro- tive. Among them, carbamates like b-oxopropylcarbamates have
static interactions; at the same time, spirulina gures strong been vastly utilized in agronomy, organic production, and phar-
interactions with NPs due to its good chelating capability with maceutics. Most recently, b-oxopropylcarbamates were produced
metal ions. The advantage of a physical cross-linking factor or from CO
2
, secondary amines and propargylic alcohols. In addition,
40,41
42
43,44
45–50
TPP over a chemical cross-linker (like glutaraldehyde) is the different catalysts such as ruthenium,
Fe, Cu,
bicyclic guanidine have been explored in the multicomponent
In recent years, many studies have focused on the chemical reaction. Cu and Ag have been illustrated to be the most impres-
xation of CO
due to its attributes such as low toxicity, cost effi- sive catalysts for this reaction. Silver compounds have been shown
Ag,
and
51
prohibition of the toxicity of reagents.

2
ciency, non-ammability, ubiquity and reproducibility, which to be great transition metal catalysts with particular selectivity and
they have considerable benets over other catalysts.
Multicomponent reactions (MCRs) are one-pot reactions
School of Continuing Education of Xinxiang University, Xinxiang, Henan, 453000, P. employing more than two starting materials, for example, 3, 4,
a
R. China. E-mail: xinxiangxueyuan@aliyun.com
b
.
, 7 reactants, where most of the atoms of the starting mate-
New Materials Technology and Processing Research Center, Department of Chemistry,
52
rials are incorporated in the nal product. Several descriptive
tags are regularly attached to MCRs: they are atom economic,
that is, the majority, if not all, of the atoms of the starting
materials are incorporated in the product; they are efficient,
Islamic Azad University, Neyshabur Branch, Neyshabur, Iran. E-mail: seyedmohsen.
sadeghzadeh@gmail.com
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c9ra02680k
1
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that is, they efficiently yield the product since the product is great catalytic performances are ascribed to the usage of the
formed in one-step instead of multiple sequential steps; they green ionic gelation that might act as a dual activator to both
are convergent, that is, several starting materials combine in the substrates and CO (can be observed Scheme 1).
2
one reaction to form the product; they exhibit a very high bond-
forming-index (BFI), that is, several non-hydrogen atom bonds
are formed in one synthetic transformation. Therefore, MCRs
Experimental section
53
are oen a useful alternative to sequential multistep synthesis. Materials and methods
5
4
Many basic MCRs are name reactions, for example, Ugi,
Passerini, van Leusen, Strecker, Hantzsch, and Biginelli,
High purity chemicals were procured from Fluka and Merck. An
Electrothermal 9100 apparatus was utilized for the determination
of uncorrected melting points in open capillaries. A VERTEC 70
spectrometer (Bruker) in transmission mode was used for the
determination of FTIR spectra. Samples were pulverized and
pelletized with spectroscopic grade KBr. The determination of
the size and structure of the nanoparticles was done via a trans-
mission electron microscope (TEM) (Phillips CM10) operated at
55
56
57
58
59
or one of their many variations. For example, in the Ugi reac-
tion, the primary scaffold is mostly dictated by the type of the
acid component (and to a less degree by the amine component),
for example, carboxylic acid, carbonic acid, thiocarboxylic
60
3 2 2
acids, HN , H O, H S, HNCO, HNCS, and phenol, which is one
of the few recent innovations regarding primary scaffold
61
diversity in Ugi reactions, leading to a-acylaminocarbox-
amides, carbamates, a-acylaminothiocarbonamides, tetrazoles,
a-aminoamides, a-aminothioamides, hydantoins, thio-
100 kV. The crystallographic structures of the nanoparticles were
determined using powder X-ray diffraction (Bruker D8 Advance
model) with Cu Ka radiation. Thermal gravimetric analysis (TGA)
62
hydantoins and a-aminoarylamides, respectively. Addition-
ally, since MCRs are oen highly compatible with a range of
unprotected orthogonal functional groups, on a second level,
the scaffold diversity of MCR can be greatly enhanced by the
introduction of orthogonal functional groups into the primary
MCR product and allowing them to react in subsequent trans-
formations, e.g. ring forming reaction. This two layered strategy
has been extremely fruitful in the past, leading to a great
manifold of scaffolds that are now routinely used in combina-
(
NETZSCH STA449F3) was performed under a nitrogen atmo-
ꢀ
ꢁ1
1
13
sphere with a heating rate of 10 C min . H and C NMR
spectra were determined with a BRUKER DRX-300 AVANCE
spectrometer and a BRUKER DRX-400 AVANCE spectrometer.
The NMR spectra recorded for both elements were at 300.13 and
7
5.46 MHz, and 400.22 and 100.63 MHz, respectively. A Heraeus
CHN-O-Rapid analyzer was used to perform elemental analyses
for carbon, hydrogen and nitrogen. Thin layer chromatography
(TLC) was conducted on silica gel polygram SILG/UV 254 plates
63
torial and medicinal chemistry for drug discovery purposes.
for the determination of product purity and monitoring the
reaction. A Shimadzu GCMS-QP5050 Mass Spectrometer was
used to record the mass spectra.
Recently, silica nanoparticles with a brous morphology
have been widely studied by scholars aer the invention of the
dendritic brous nanosilica (DFNS). The dendritic brous
nanosilica with a shrinkage morphology has been tested in
solution to enhance the surface of the nanocatalyst compared to
the surface of the usual cubic pore or hexagonal structured
ordinary silica. In addition, dendritic brous nanosilica has the
proper potential to be a support substance in drug delivery,
isomerization and other applications. Moreover, varying the
mesoporosity properties is one of the approaches utilized to
solve the diffusion limitation difficulty; most catalysts, which
General procedure for the preparation of DFNS
2
.5 g of tetraethyl orthosilicate was dissolved in a solution of 30 mL
of cyclohexane and 1.5 mL of 1-pentanol. A stirred solution of 1 g of
cetylpyridinium bromide and 0.6 g of urea in 30 mL of water was
then added. The resulting mixture was continually stirred for
4
5 min at room temperature and then placed in a Teon-sealed
ꢀ
hydrothermal reactor and heated to 120 C for 5 h. The silica
formed was isolated by centrifugation, then washed with a mixture
of deionized water and acetone, and dried in a drying oven. This
6
4,65
are utilized to simplify isomerisation, have this issue.
dendritic brous nanosilica has indicated great potential in
The
ꢀ
66
material was then calcined at 500 C for 6 h in air.
various utilizations such as Suzuki coupling,
metathesis,
propane
67,68
69
propane metathesis for CO2 adsorbent,
cumene hydrocracking, as well as alkane hydrogenolysis.
70
General procedure for the preparation of DFNS/IG NPs
Great surface area, high stability in the case of thermal behavior
and high pore sizes of the dendritic brous nanosilica facilitate
the high availability of a bulky mass of reactants at the energetic
sites, which accordingly enhances the reaction rate and product
formation. Moreover, some big pores on the external surfaces
and small pores all over the structure are also benecial as they
act as carriers for genes and drugs. Herein, we have reported an
ionic gelation related (DFNS/IG@Ag(I) NPs) catalytic apparatus,
on which AgBr was supported, for the one-pot production of b-
oxopropylcarbamates via the three-component reaction of
Dendritic brous nanosilica (50 mg) was diffused in an acetic
acid solution using ultrasonication for 60 seconds. Spirulina
(
125 mg) was dissolved in a similar acetic acid solution and
ꢀ
stirred at the temperature of 25 C for 1 h. TPP solution (10.0
mL) was injected dropwise into the chitosan solution by
propargylic alcohols, amines and CO
2
at moderate conditions.
Exclusively, this catalytic apparatus could be quickly recycled 5
Scheme 1 Synthesis of b-oxopropylcarbamates in the presence of
times with the lowermost catalyst loading ever reported. These DFNS/IG@Ag(I) NPs.
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utilizing a syringe pump at the volumetric ow rate of 1 dried in vacuum to obtain the crude yield, which was puried by
ꢁ
1
mL min . Aer the complete addition of TPP, the mixture was column chromatography using silica gel and petroleum ether/
stirred mechanically at 1000 rpm speed for 1 h. The formed ethyl acetate (100 : 1–20 : 1). For the recycling procedure, the
product was gathered by ltration and then washed by using catalyst was separated using ltration, washed with alcohol and
water at pH ¼ 7, and dried in vacuum at the temperature of dried with a pump.
ꢀ
2
5 C for 24 h.
Results and discussion
General procedure for the catalytic synthesis of b-
oxopropylcarbamates
The dendritic brous nanosilica was produced using
AgBr (0.05 mmol), DFNS/IG NPs (10.0 mg), propargylic alcohols a simple approach and then functionalized using the ionic
5.0 mmol) and secondary amines (5 mmol) were mixed in gelation (IG) of TPP and spirulina. The produced DFNS/IG
(
a Schlenk tube equipped with a stir bar. Aer that, the appa- NPs were then characterized using various methods like TG
ratus was cleaned with carbon dioxide for more than two times, analysis, TEM, BET, FESEM, and FT-IR spectroscopy. The
ꢀ
and the blend was stirred at the temperature of 50 C and morphology as well as the structure of the dendritic brous
pressure of 15 bar with carbon dioxide for the desired time. nanosilica and DFNS/IG NPs were well marked using TEM
When the reaction was complete, the mixture was partitioned and FESEM analysis. The SEM image of the dendritic brous
by diethyl ether (3–15 mL). The upper layers were gathered and nanosilica nanoparticles indicates dandelion-like structures
Fig. 1 (a) FESEM images of DFNS NPs; (b) TEM images of DFNS NPs; (c) FESEM images of DFNS/IG NPs; (d) TEM images of DFNS/IG NPs.
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with diameters of around 300 nm and a wrinkled radial
The analysis of nitrogen physisorption indicated that the
structure (as can be seen in Fig. 1a). In addition, this ber BET specic surface area of the dendritic brous nanosilica and
2
ꢁ1
(
with a thickness of around 8.5 nm) originated from the DFNS/IG NPs was around 678 and 209 m g , respectively. The
center of the considered spheres and extended in all radial reduction in the surface area of DFNS/IG in comparison with
dimensions (can be seen in Fig. 1b). Moreover, the excessive the dendritic brous nanosilica could be because of the sup-
extension of the wrinkled radial structures resulted in cone- porting IG on the dendritic brous nanosilica. In addition, the
shaped open pores. The images obtained from FESEM and decrease in the surface area in the case of DFNS/IG NPs was
TEM illustrate that the whole sphere was completely solid clearly due to the poor bicontinuous concentric IG morphology
and consisted of bers. In addition, this structure of open of the nanocatalyst. As can be seen in Fig. 2, the nitrogen
hierarchical channels and bers were convenient for mass adsorption–desorption isotherms of the dendritic brous
transfer in the case of reactants and enhanced the availability nanosilica based catalysts indicated a type IV isotherm with an
of active sites. The FESEM and TEM images of DFNS/IG NPs H1-type hysteresis loop, proposing the presence of mesopores.
indicated that aer correction, the morphology of the The corresponding pore sizes predicted from the desorption
dendritic brous nanosilica did not vary (can be observed in series of the nitrogen isotherm using the BJH procedure dis-
Fig. 1c and d). TGA of DFNS/IG NPs was also performed at played a narrow pore size distribution that peaked at about
ꢀ
ꢀ
temperatures ranging from 25 C to 800 C for investigating 9 nm (as can be seen Table 1). The excellent mesopore size of
the thermal stability, as shown in Fig. S1.† The weight loss at dendritic brous nanosilica with great capacity may aid the
ꢀ
2
39 C was because of the removal of solvents existing on the loading of TPP and spirulina, which have comparatively high
surface of the dendritic brous nanosilica. The obtained molecular sizes.
weight loss for DFNS/IG NPs was 38 percent by weight. These
FT-IR spectroscopy was used to specify the surface
results indicated the great graing ability of the organic enhancement of the obtained catalyst (as seen in Fig. S2†). The
materials on dendritic brous nanosilica.
FT-IR spectrum indicated peaks in the frequency range of about
Fig. 2 Adsorption–desorption isotherms of the (a) DFNS NPs and (b) DFNS/IG NPs; (c) BJH pore size distributions of the DFNS NPs and (d) DFNS/
IG NPs.
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Table 1 Structural parameters of DFNS and DFNS/IG NPs
4
foundation, different Ag salts such as AgI, AgBr, and AgBF ,
which could be used together with DFNS/IG NPs for the
coupling reaction to occur and obtain moderate to great
product yields, were successively examined (Table 2, entries 4–
13). In comparison, AgBr exhibited the best catalytic efficiency.
2
ꢁ1
3
ꢁ1
Catalysts
S
BET (m g
)
V
a
(cm g
)
D
BJH (nm)
DFNS
DFNS/IG
679
210
3.3
1.4
9
6
2
mol% of AgBr in the presence of DFNS/IG NPs could efficiently
catalyze the considered reaction (Table 2, entry 5).
In a related research to improve the reaction situation, it was
determined that solvent-free situations were rather impressive
than those utilizing solvents, considering the reaction time as
well as the yield of products (Table 3). The vital role of
temperature in the preparation of b-oxopropylcarbamate was
examined. It was obvious that the reaction procedure was
sensitive to the reaction temperature. For minimizing the
ꢁ
1
3
400–3300 cm
corresponding to the oxygen–hydrogen
stretching vibration. This demonstrated the presence of
carbohydrates and amino acids. The peaks in the frequency
range of 3500–3300 cm for the nitrogen–hydrogen stretching
vibrations conrmed the presence of amines in proteins as well
as lipids. The bands at 2972 and 2896 cm were considered to
belong to the carbon–hydrogen stretching of the aliphatic
moieties. The peak at 1720 cm was because of the stretching
of the carbonyl group in the esters and amino acids. The con-
forming peak at 1642 cm corresponding to the nitrogen–
hydrogen bending vibration indicated the presence of the
carbonyl b-unsaturated ketone amide. The peak existing at
ꢁ
1
ꢁ1
reaction activation energy, the reactions were performed at
ꢁ
1
ꢀ
5
0 C by taking advantage of the great efficiency of DFNS/IG
ꢀ
NPs. Temperatures higher than 50 C did not lead to changes
in the reaction efficiency. In addition, Table 3 shows the inu-
ence of time on the production of b-oxopropylcarbamate. Aer 5
hours, the yield of b-oxopropylcarbamate product increased up
to 98%, while further extension in time did not lead to increase
in the product yield. Therefore, the appropriate time for the
production of b-oxopropylcarbamate was 5 hours. Another
inuential parameter, which might be considered for this
reaction, is the amount of DFNS/IG NPs for efficient catalysis to
synthesise b-oxopropylcarbamate. The average efficiency of
product formation was found by the addition of 3.0 mg of the
catalyst to the reaction. The best yield was obtained when the
reaction was performed in the presence of 5 mg of DFNS/IG
NPs. It is signicant that the reaction was not enhanced on
using higher amounts of DFNS/IG NPs.
ꢁ
1
ꢁ
1
1411 cm
conrmed the presence of methylene bending
ꢁ
1
ꢁ1
vibration. The bands at 1342 cm and 1278 cm indicated
carbon–oxygen stretching and oxygen–hydrogen bending
vibrations of the oxygen of alcohol, respectively. On function-
alization with tripolyphosphate, the intensity of the peak at
048 cm enhanced and a new peak appeared at 882 cm ,
which was related to the phosphate and phosphoramide
groups, and this proposed a reaction occurring between
ꢁ
1
ꢁ1
1
5
ꢁ
+
–
P3O
and –NH . The main variation in the IR spectra was
3
the presence of another peak in the TPP bead spectrum at
10
ꢁ1
1
150 cm , probably due to the –P]O stretching vibration,
determining the presence of phosphate groups.
The reaction of CO , 2-methylbut-3-yn-2-ol, and pyrrolidine
was chosen as the base reaction to test the optimal catalytic
system. Data shown in Table 2 indicates that the reaction could
not be performed without catalysts at mild conditions. More-
over, no product was obtained in the presence of AgBr or DFNS/
IG NPs alone (as seen in Table 2, entries 2–3). On this
In addition, to enhance the production of b-oxopro-
pylcarbamate, carbon dioxide pressure was studied. The
optimal pressure of CO2 yielding the best production of
DFNS/IG NPs would be specic, whereas the kinetics of the
mass transfer reactions might change due to diffusion and
2
2
reaction between CO , 2-methylbut-3-yn-2-ol, and pyrroli-
dine. The inuence of pressure was experimentally deter-
mined in the range from 0.5 to 3.5 MPa. The operation of
DFNS/IG NPs enhanced strongly when the carbon dioxide
pressure increased from 0.5 to 1.5 MPa, aer which it
sustainable in the pressure range of 1.5–3.5 MPa as shown in
Fig. 3. These contrary facts determined the requirement for
an optimum pressure of around 1.5 bar for the best produc-
tion of b-oxopropylcarbamate.
Since the conditions of the reaction were improved, we
then tested the substrate range by examining the reactivity of
aryl or alkyl substituents with different secondary amines.
The reaction of pyrrolidine with various terminal propargylic
alcohols, directing the alkyl substituents in the propargylic
position, occurred at the same condition and produced the
corresponding carbamates with great yields (as observed in
Table 4, entries 1–4). Commonly, tertiary alcohols were more
active compared to primary alcohols and secondary alcohols,
and simultaneously, indicated distinct reactivity with various
substituent groups. The propargylic carbonate intermediate
was quickly produced via the reaction of tertiary alcohols and
a
Table 2 Optimization of the Ag(I)-catalyzed reaction
b
Entry
Catalytic system
Yield (%)
1
2
3
4
5
6
7
8
9
—
AgBr
—
AgCl
AgBr
AgI
AgOAC
Ag
Ag
AgNO
AgBF
Ag WO
AgPF
—
—
—
—
—
89
98
53
29
46
54
61
28
19
53
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
DFNS/IG
2
O
2
CO
3
1
1
1
1
0
1
2
3
3
4
2
4
6
a
Reaction conditions: [Ag] (0.05 mmol), DFNS/IG NPs (5 mg), 2-
(1.5 MPa),
methylbut-3-yn-2-ol (5 mmol), pyrrolidine (5 mmol), CO
2
ꢀ
b
5
0 C, 5 h. GC yields [%].
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Table 3 The effects of solvent, amount of catalyst, time, and temperature on the synthesis of b-oxopropylcarbamate
ꢀ
a
Entry
Solvent
Temperature ( C)
Catalyst (mg)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
DMF
DMSO
Dioxane
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
60
50
40
30
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
7
5
3
1
7
7
7
7
7
7
7
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
5
4
3
6
6
6
6
33
51
62
31
52
65
39
54
77
22
16
23
15
15
39
31
20
98
98
98
73
61
98
68
41
98
98
81
76
CH
CH
3
CN
Cl
2
2
EtOAc
THF
Toluene
CHCl
n-Hexane
Benzene
3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
CCl
Cyclohexane
4
2
H O
EtOH
i-PrOH
MeOH
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
a
GC yields [%].
carbon dioxide by the support of proper catalysts. Propargylic lower reactivity was found possibly due to the steric
alcohols with cycloalkyl substitutions had lower reactivity (as hindrance of methyl or cyclohexyl in amines during the
observed in Table 4, entries 5 and 6), and the reason would be nucleophilic attack to a-methylene carbonate.
the inuence of steric hindrance on the carbonate interme-
Based on the above yields, a proper mechanism for DFNS/
diate formation. In addition, other propargylic alcohols with IG@AgBr was determined and has been shown in Scheme 2.
unsaturated groups such as phenyl substitution showed At rst, spirulina and TPP simultaneously enable the –OH of
a good yield of products aer the addition of a certain the 2-methylbut-3-yn-2-ol and increase the nucleophilicity of
amount of co-catalyst. Moreover, the secondary amines pre- the –OH to the carbon dioxide, which is trapped and acti-
sented good reactivity. However, for the entries 15, slightly vated by the synergistic effects of TPP and spirulina. Next, the
species of Ag activated a triple bond to provide the connec-
tion between the charged oxygen and the carbon in the triple
bond, causing the formation of the ve-membered ring.
Moreover, the catalyst was expelled by the ve-membered
ring, and the main free intermediate was formed. Finally,
the amine attacked the carbonyl group in the intermediate,
followed by the tautomerism of enol to ketone as well as the
7
1–73
production of the corresponding b-oxopropylcarbamates.
It can be noted that the heterogeneous quality of DFNS/IG
NPs enables its comfortable recovery from the reaction
environment. The activity of the recycled DFNS/IG NP cata-
lysts under suitable conditions was investigated. Aer the
completion of the reaction, the catalyst was isolated using

ltration, washed with alcohol and dried with a pump. The
synthesized DFNS/IG NPs were recovered for ve consecutive
cycles without experiencing any signicant loss in the
Fig.
2
3 The effect of CO pressure on the synthesis of b-
oxopropylcarbamate.
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a
2
Table 4 Scope of the reaction of propargylic alcohols, secondary amines and CO
b
Entry
Amine
Alcohol
Product
Yield (%)
1
98
92
2
3
4
5
6
7
8
79
53
68
84
90
94
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Table 4 (Contd.)
b
Entry
Amine
Alcohol
Product
Yield (%)
9
93
91
68
93
88
81
1
1
1
1
1
0
1
2
3
4
1
5
51
a
ꢀ
b
Reaction conditions: [Ag] (0.05 mmol), DFNS/IG NPs (5 mg), 2-methylbut-3-yn-2-ol (5 mmol), pyrrolidine (5 mmol), CO (1.5 MPa), 50, C, 5 h. GC
2
yields [%].
catalytic activity (as seen in Fig. 4). The sustainability of this ascribed to the cellulose bers that were mighty enough to
catalyst was because of the stability of the catalyst structure. effectively conduct the reaction by preventing IG compres-
The notable capability of the DFNS/IG morphology may be sion and abandoning IG during the process of reaction.
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Scheme 2 Proposed catalytic mechanism of the DFNS/IG@AgBr system.
NPs have considerable features like enhanced catalytic perfor-
mance, excellent porosity, and high chemical stability for the
production of b-oxopropylcarbamates via the three-component
coupling reaction of CO , propargylic alcohols and amines.
2
Moreover, the rst order dependency of the reaction was
determined by catalyst loading, and based on the obtained
results, a likely mechanistic route was found. In addition, we
investigated the reusability of the DFNS/IG NPs, and the best
results propose it to be an inexpensive catalyst to produce
quinazolines.
Conflicts of interest
There are no conicts to declare.
Fig.
4 The reusability of the catalyst in the synthesis of b-
oxopropylcarbamates.
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