Microwave assisted organocatalytic synthesis of 5-hydroxymethyl furfural in a monophasic green solvent system

Article abstract of DOI:10.1039/c4ra03137g

Monophasic microwave assisted dehydration of fructose to 5-hydroxymethyl furfural (HMF) catalyzed by p-toluene sulphonic acid (PTSA) was studied in non-aqueous organic solvents. Of the three monophasic systems studied (isopropyl alcohol, N,N-dimethyl formamide and dimethyl sulfoxide), isopropyl alcohol, a preferred green solvent gave the product in highest yield. Use of PTSA as proton source for microwave (2.45 GHz) assisted dehydration of fructose in isopropyl alcohol resulted in >98% fructose conversion with >90% HMF yield in 90 s of reaction time. The use of inexpensive and mild acid catalyst PTSA for HMF synthesis with an ecofriendly solvent IPA offers ease of catalyst handling and solvent recovery. This journal is the Partner Organisations 2014.

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ARTICLE TYPE
Microwave assisted organocatalytic synthesis of 5-hydroxymethyl
furfural in a monophasic green solvent system
a
a,b
Hitesh Pawar and Arvind Lali*
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Monophasic microwave assisted dehydration of fructose to 5ꢀhydroxymethyl furfural (HMF) catalyzed by
pꢀ toluene sulphonic acid (PTSA) was studied in nonꢀaqueous organic solvents. Of the three monophasic
systems studied (isopropyl alcohol, N, Nꢀdimethyl formamide and dimethyl sulfoxide), isopropyl alcohol,
a preferred green solvent gave the product in highest yield. Use of PTSA as proton source for microwave
1
0
(2.45 GHz) assisted dehydration of fructose in isopropyl alcohol resulted in >98% fructose conversion
with >90% HMF yield in 90s of reaction time. The use of inexpensive and mild acid catalyst PTSA for
HMF synthesis with an ecofriendly solvent IPA offers ease of catalyst handling and solvent recovery.
Introduction
obtained 82% yield in 1h under refluxing conditions. They also
studied use of H SO , H PO , HCOOH, CH COOH, and B(OH)
3
2
4
3
4
3
1
2
2
3
3
4
4
5
0
5
0
5
0
5
Depletion of fossil fuel resources along with significant increase
in carbon emissions have necessitated increased focus on
development of processes for production of bioꢀbased chemicals
and chemical intermediates. Further, sustainability issues, in
addition to associated accident and pollution hazards on account
of extreme conditions employed in inefficient synthetic
procedures, have created a need to move synthetic chemistry
towards intensified rapid and highly selective reaction systems.
Thus, attempts are being made to develop reaction schemes that
are based on nonꢀfossil resources and involve miniꢀreactors with
large throughputs and which are less polluting and consume less
energy. Among the existing advanced tools of organic synthesis,
microwave reactors provide one of the options for selective and
5
5
6
6
7
7
8
0
5
0
5
0
5
0
as catalyst with 68% to trace yields. Intensification of the acid
catalyzed dehydration of fructose has been attempted by many
researchers through use of microwaves with different acid
catalysts. Lewis acid catalyst, AlCl ·6H O under microwave
3
2
heating at 160°C gave 61% yield of HMF within 10min in
[21]
aqueous tetrahydofuran
. Typically, the reactions involving
aqueous solutions seem to suffer from rehydration reactions of
HMF to several unwanted products during the workꢀup of the
[22]
reaction mixture aimed at product isolation. De et al.
used
AlCl as catalyst for fructose dehydration in monophasic system
3
of DMSO, and biphasic system of water and methyl isobutyl
ketone. Microwave assisted reaction at 100ꢀ140°C was observed
to provide the best HMF yield of 71.3 % in 5min in water and
[
1]ꢀ [6]
rapid and high throughput processes
.
MIBK.
Nonꢀfood lignocellulosic biomass (agriculture, marine and
forest) and their coꢀproducts provide the most promising
alternative renewable feedstock for production of carbon bearing
[23]
Bi et al.
reported the advantage of using an inorganic salt
like NH Cl in isopropyl alcohol over use of mineral acid catalysts
4
in terms of lower corrosiveness. The reaction was however much
slower and a yield of 68% was obtained in 12h. Microwave
assisted heating was then successfully attempted for enhancing
reaction rates and the reaction time of 12h could be reduced to
[
7]ꢀ[9]
fuel, energy and chemical products
. Of the possible biomass
based platform chemicals, 5ꢀhydroxymethyl furfural (HMF) has
been listed as one of the more versatile and potential
intermediates for production of fuels, bulk chemicals,
10min with 92% fructose conversion giving a 37% yield to HMF.
[
10], [11]
pharmaceuticals, polymers, fine chemicals etc.
. Several
[24]
Riisager and Hansen
have also reported microwave assisted
reports have been published over the last three decades on
designing of effective routes for synthesis of 5ꢀhydroxymethyl
synthesis of HMF catalyzed by aqueous HCl with reaction time
ranging from 1s to 60s at 200°C. Fructose conversion of 52% was
possible with a HMF selectivity of 63% in only 1s while 95%
conversion could be possible with a much reduced yield of 53%
in 60s.
[
12]
furfural
.
Procedures reported for the synthesis of HMF from
carbohydrate moieties like glucose, fructose and others have
consisted of simple acid catalyzed dehydration reaction using
organic acids like oxalic acid, levulinic acid, and acetic acid;
On account of handling and corrosion issues with mineral
acids, and relative ineffectiveness of organic acids like acetic and
oxalic acids, several workers have attempted use of pꢀtoluene
sulphonic acid (PTSA) as catalyst for synthesis of HMF in
different solvent systems such as water, polyethylene glycol,
[
13]
[14]
[15]
[16]
mineral acids like H SO , HCl , H PO
4
ionic liquids
,
2
4
3
[
17]
[18]
heteropoly acids ; and Lewis acid like AlCl
,lanthanide
3
[
19]
[20]
chlorides . Lai and Zhang
studied conversion of fructose to
HMF in alcoholic solvents with aqueous HCl as catalyst and
[25]
[26]
ionic liquids and supercritical solvent . Ilgen et al.
studied
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fructose dehydration in presence of PTSA in choline chloride at
solvents for synthesis. It was found that of the tested solvents,
IPA, DMF and DMSO were remarkable in terms of yield and
conversion (Fig.1). The percentage yield of HMF in DMF,
[
27]
1
00°C with 67% of HMF yield. Asghari et al.
reported use of
[
28]
PTSA in supercritical water at 240°C while Moreau et al.
reported use of PTSA for HMF synthesis in presence of the 40 DMSO and IPA obtained was 90%, 88% and 85%, respectively
5
0
5
0
imidazolium ionic liquid and DMSO at 80°C with a yield of 68 %
in 32h.
with more than 94% fructose conversion. As DMF gave highest
yield out of all the tested solvents, and IPA gave highest yield
among the tested alcoholic solvents, these two solvents were
selected for further study.
In the present study, we report a green and efficient
microwave assisted dehydration of fructose in nonꢀaqueous
solvents in presence of pꢀtoluene sulphonic acid (PTSA) as
catalyst (Scheme 1). Nonꢀaqueous solvents were used in order to
facilitate the dehydration reaction and also for subsequent work
up of the reaction mixture by utilization of minimum energy for
solvent separation. Monophasic solvents with small but finite
45
Lower yields of about 60% of HMF in IPA (than obtained in
this work) has been previously reported and attributed to
formation of stable fructofuranose intermediate under the acidic
1
1
2
[
29]
conditions
. Although the use of lower alcohols for HMF
synthesis in combination with aq. HCl has been reported with
solubility for fructose were selected. Thus, isopropyl alcohol 50 formation of etherification products, IPA was considered a better
[
20]
(IPA), nꢀbutanol, tertꢀbutanol (TBA), isoamyl alcohol (IAA), nꢀ
butyl alcohol (NBA), N, Nꢀdimethyl formamide (DMF) and
dimethyl sulfoxide (DMSO) were used. Microwave (MW)
assisted heating was selected for its proven advantages of short
candidate for higher selectivity due to its bulkiness . Use of
the mineral acid as catalyst reported in these works makes the
process system corrosive, tedious and nonꢀecofriendly. In the
present study an attempt was therefore made to employ an
reaction time and higher selectivity. Thus, the complete reaction 55 inexpensive and mild acid catalyst PTSA in combination with
protocol with respect to reaction time, temperature and PTSA
concentration was optimized to obtain high yield of HMF with
high conversion of fructose.
IPA to provide ease of handling and reduced adverse
environmental impact. Further, the present process gave HMF in
higher yield (>85%) in MW assisted conditions in short reaction
times (maximum 120s). The high yields obtained can be said to
be due suppression of both etherification reactions and formation
of unstable fructofuranose intermediates in presence of PTSA and
IPA under MW radiation. Thus, a combination of MW, PTSA
and IPA was observed to favor formation of unstable
intermediates that selectively convert into HMF. The plausible
mechanism under MW heating in presence of PTSA can be given
as in Scheme 2 i.e. via formation of fructofuranose intermediates.
On the other hand, higher alcohols also gave HMF yields lower
than IPA: TBA (39%); NBA (47%); and IAA (17%) even though
the conversion was more than 88% in all three cases.
60
65
Scheme 1 Microwave assisted formation of HMF in presence of PTSA
25
Scheme 2 Plausible mechanism of MW assisted PTSA catalyzed fructose
dehydration reaction
70 Fig. 1 Effect of different solvents on yield, conversion and
selectivity. Reaction condition: PTSA (0.1 g/ml for alcohols and
Results and Discussion
0
.2 g/ml for DMF and DMSO) temperature 120ºC, time 120s.
Effect of solvent on HMF yield, conversion and selectivity
30
Effect of catalyst concentration
Dehydration of fructose to HMF was attempted in different low
and high boiling monophasic organic solvents. High boiling
solvents were selected from the group of previously most studied
solvents for fructose dehydration viz. DMF and DMSO. The low
boiling solvents were selected from the group of higher alcohols
75
PTSA was selected as the organocatalyst for fructose dehydration
for its ease of handling and low corrosiveness compared to
previously reported mineral acids. The effect of PTSA
concentration on fructose dehydration was studied through runs
35
namely IPA, NBA, TBA, and IAA which are considered as green 80 made with varying concentrations (0ꢀ0.2 g/ml) of PTSA in IPA
2
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and DMF as reaction media. The choice of solvent was seen to
have a significant effect on HMF yield and fructose conversion.
Results, shown in Fig. 2, indicated that IPA was a better solvent
system in terms of both yield and conversion despite DMF having
a better solubility for fructose.
It was found that there was no fructose conversion and
decomposition in absence of catalyst. On increasing PTSA
concentration in DMF beyond 0.03 g/ml, HMF yield increased
gradually up to 0.10 g/ml and there was negligible effect from
0.10ꢀ0.16 g/ml. However, the yield increased remarkably from
Table.1 Comparison of present system with previously reported
systems using PTSA as catalyst
%
Yield
Reaction Productivity
Entry Solvent
Ref.
time
kg/L/h
5
This
work
1
2
IPA
90
67
90s
25.20
a
c
ChCl
30m
0.62
(26)
Super
critical
water
3
65
120s
0.29
(27)
1
1
2
2
3
3
4
0
5
0
5
0
5
0
0
.16 to 0.20 g/ml. While in case of IPA, yield of HMF showed
b
similar trend the requirement of PTSA was 50% less in IPA as
compared to DMF for >98% conversion which can be attributed
IL and
DMSO
4
68
32h
0.001
(28)
[
30]
a
b
c
to the formation of a stable complex between PTSA and DMF
.
Choline chloride, IL ionic liquid, kg/kg of ChCl/h.
Besides, the existence of DMF in two resonance forms of amide
structures can be said to favor hydrogen bonding with the acidic
part of PTSA thereby possibly resulting in lower availability of
PTSA as a proton source for fructose dehydration. Optimal PTSA
concentrations were found to be 0.10 g/ml and 0.20 g/ml in IPA
and DMF, respectively for obtaining maximum of HMF yield and
fructose conversion. Hence, these PTSA concentrations were
Effect of reaction time
50
As shown in Fig. 3, there was a significant effect of reaction time
on fructose conversion and HMF yield in both solvent systems
i.e. DMF and IPA. A higher yield of HMF (91%) was obtained
only in 90s when IPA was employed, whereas DMF took 120s to
used for further study in the two solvents. It may be noted that 55 give similar yield. It can be seen that while reaction is faster in
while the concentrations of PTSA used were higher than typical
catalytic amounts, its low cost and good performance coupled
with possible recovery and reuse makes PTSA an acceptable
process option.
DMF, the selectivity shown is higher in IPA at yields greater than
about 65%. A decrease in HMF yield was seen in both systems at
longer reaction time of 150s although conversions were >99% in
both solvents. Long reaction times have been reported to favor
Recovery and reuse of PTSA was attempted by evaporating 60 formation of side products due to decomposition of HMF to
the solvent from the reaction mixture followed by mixing with
humins, levulinic acid, formic acid and other condensation
[
22],[24].
[11],[31]
water and separating the organic layer for HMF recovery
products.
. Product yield decreased in IPA and DMF at
The water wash layer containing PTSA and water soluble side
products was polished on a hydrophobic adsorbent column and
then evaporated to obtain PTSA for reuse. However, after the 65 brown. It was found that while there was increased formation of
reaction times beyond 90s and 120s, respectively. This was
visibly apparent by change in color of the reaction mass to dark
evaporation of water a viscous brown mass was obtained from
which it was difficult to isolate the PTSA. While better scheme
for recovery and reusability of PTSA can be developed the
present process nevertheless proves attractive as it avoids use of
stringent reaction conditions e.g. supercritical water and higher
temperature ionic liquid and long reaction times. The present
system is seen to offer better productivity from these view points
under relatively less severe conditions (Table 1).
side products with increased reaction time there was no formation
of levulinic acid in the process under conditions used.
120
100
80
1
20
00
60
%
%
%
%
Conversion in DMF
Yield in DMF
4
0
0
0
1
Conversion in IPA
Yield in IPA
2
8
6
4
2
0
0
0
0
0
0
50
100
Reaction time (s)
150
200
% Conversion in DMF
Yield in DMF
% Conversion in IPA
Yield in IPA
7
0
%
Fig. 3 Effect of reaction time in DMF and IPA on conversion and
yield. Reaction conditions: fructose (2.77 mmoles), IPA 8ml,
PTSA 0.10 g/ml and 0.2 g/ml for IPA and DMSO respectively,
temperature 120ºC.
%
0
.00
0.05
0.10
0.15
0.20
0.25
75
Catalyst concentration (g/ml)
Effect of reaction temperature
Fig. 2 Effect of PTSA concentration on conversion and yield in
IPA and DMF. Reaction conditions: fructose (2.77 mmoles), IPA
8ml, temperature 120°C, time 120s.
MW system (Biotage) operating at 2.45GHz frequency was used
for the reaction. The reaction temperature in the system was
4
5
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adjusted by giving temperature set point to MW system which
uses appropriate power for quick heating of the reaction mass to
the desired temperature measured by an IR temperature sensor.
selectivity. The yield and selectivity decreased at fructose
concentrations above 0.125 g/ml and below 0.0625 g/ml. There
was negligible effect of fructose concentration from 0.0625 to
Thus reaction temperature was varied to study the effect on the 50 0.125 g/ml which gave almost same HMF yield (91 % and 90%,
reaction progress. Temperatures were tested in the range of 90 to respectively).
30°C while maintaining the desired substrate and catalyst
5
0
5
0
5
1
120
concentrations. A reaction temperature of 120°C gave ~90% yield
to HMF at 100% fructose conversion in both IPA and DMF. The
reaction temperature above and below 120°C in both solvents
resulted in a decrease in HMF yield. The lowest yield between
100
80
60
40
20
0
1
1
2
2
3
0ꢀ40% and conversion between 85ꢀ90% was observed at 90°C.
At higher temperatures even though the conversion was complete
the yield to HMF suffered significantly (Fig. 5). The optimum
temperature thus was found to be 120°C for the reaction system.
It was generally noted that higher temperatures (>120 °C) and
longer reaction times (>120s) resulted in a loss of yield
expectedly on account of byꢀproduct formation and/or
decomposition of HMF (Fig.3 and Fig.4). Sequential conversion
of fructose to HMF and its subsequent conversion to other
products can be expected to be controlled by intensified short
duration reaction on MW system. It was therefore decided to
% Conversion
% Yield
%
Selectivity
0
0.05
0.1
0.15
0.2
0.25
0.3
Concentration of fructose (g/ml)
Fig. 5 Effect of fructose concentration on conversion yield and
selectivity in IPA. Reaction conditions: Fructose (2.77mmoles),
deploy the microwave system in the work. A comparison between 55 PTSA (0.1 g/ml) temperature 120ºC, time 90s.
the progress of the reaction in MW assisted system with that
Effect of water content
using a conventionally heated system was also done and is
described later below.
Water has high solubility for sugars and it is a green solvent too.
Thus, use of water or aqueous reaction media provides an
excellent platform but is unfriendly to dehydration reactions and
aqueous acidic conditions may lead to formation of byꢀproducts
1
20
00
6
6
7
7
0
5
0
5
1
[
22]
.
On the other hand, use of strictly anhydrous solvents poses
8
6
4
2
0
0
0
0
0
practical problems especially in large scale production systems
especially when the solvents used have tendency to carry water
traces. Thus, in order to evaluate the role of water content for
microwave assisted fructose dehydration in presence of acid
catalyst PTSA and IPA as reaction medium, fructose dehydration
was examined with different concentration of water in IPA. The
concentration of externally added water in reaction was varied in
the range 4ꢀ10% v/v and fructose dehydration was examined
under otherwise optimized reaction conditions. Fig 7 indicates the
observed influence of water content in reaction medium on HMF
yield and fructose conversion.
%
%
%
%
Conversion in IPA
Conversion in DMF
Yield in DMF
Yield in IPA
80
90
100
110
120
130
140
Temperature (°C)
Both HMF yield and fructose conversion are seen to be
strongly affected by water presence, with maximum being
obtained with IPA containing moisture in equilibrium with
atmospheric air (0.3%). Indeed presence of water is known to
lead to formation of side products (Scheme 1) during fructose
Fig. 4 Effect of reaction temperature in DMF and IPA on
conversion and yield. Reaction conditions: fructose (2.77
mmoles), IPA 8ml, PTSA 0.10 g/ml and 0.2 g/ml for IPA and
DMSO, respectively, Reaction time: IPA system 90s; DMF
system 120s.
30
[
24]
dehydration as reported in earlier reports
.
35
Effect of fructose concentration
80
Fructose concentration has remarkable effect on percentage yield
and selectivity in the PTSA catalyzed dehydration under MW
assisted heating (Fig.5). As mentioned in Scheme 1 during
fructose dehydration, side reactions can lead to decrease in yield
and selectivity. Varying initial concentration (0.032ꢀ0.25 g/ml) of
fructose was used to illustrate the of role substrate concentration
for selective fructose dehydration. There was negligible effect of
fructose concentration on conversion, which was more than 90%
for all concentrations tested. However, it was found that fructose
concentration has remarkable effect on HMF yield and
4
0
45
4
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1
20
00
Fructose (99%) and 5ꢀhydroxymethyl furfural (99%) standards
for HPLC analysis were purchased from SigmaꢀAldrich (St.
Louis, MO) and used without any purification. MW assisted
reactions were performed in 20 mL microwave safe glass
pressure vials on a Biotage Initiator 2.5 microwave reactor
system operating at a frequency 2.45GHz, with maximum power
of 600W.
1
80
60
40
20
0
3
5
HPLC analysis
%
%
Conversion
Yield
40
HPLC analysis was performed on an Agilent 1200 series HPLC
system equipped with an RI detector and using BioꢀRad aminex
HPXꢀ87H, 300mm×7.8mm ion exclusion column. The mobile
phase used for analyses was 5mM H SO in deionised water as
0
2
4
6
8
10
12
%
Water in IPA
2
4
45
eluent at 60 °C and 0.6 mL/min. Liquid samples were suitably
diluted before analysis with deionised water and filtered through
a 0.2µm PTFE filter. All values are obtained by tabulating mean
of three experiments.
Fig. 6 Influence of initial water content on yield and conversion.
Comparison of microwave assisted versus conventionally
heated systems
5
The concentrations of fructose and HMF were quantified from
HPLC analysis through use of standards obtained from SIGMA.
Fructose conversion (mole %), HMF yield (mole %), and
selectivity (mole %) is determined as,
In order to bring out the significant role microwaves played in
intensifying the reaction, synthesis of HMF was carried out using
conventional heating under otherwise similar optimized process
parameters. It was found that whereas MW assisted reaction
resulted in 90% yield of HMF in 90s, conventionally heated
reaction could give a maximum of 66% yield in 2h at the same
temperature of 120°C (Fig. 7). Use of MW for large scale
synthesis suffers from scalability issues and high investment in
equipment, and therefore MW assisted reactions can possibly be
scaled up only when reaction times are very short resulting in
compact less expensive reactor systems. MW assisted heating
may be recommended for HMF synthesis for increase in
productivity with high yield and selectivity when reaction times
are as short as those seen in the present study.
5
0
1
1
2
0
5
0
FructoseꢀConc.
ꢀ
ꢀ
Fructoseꢀconversion = ꢁ1 −
ꢀꢂ × 100ꢀ%
InitialꢀFructoseꢀconc.
ꢀ
HMFꢀꢀConc.
HMFꢀYield = ꢁꢀ
ꢂ × 100ꢀ%
InitialꢀfructoseꢀConc.ꢀꢀ
55
HMFꢀyield
HMFꢀSelectivityꢀ = ꢁꢀ
ꢀꢂ × 100ꢀ%
Fructoseꢀconversion
General reaction and workup procedure
Fructose dehydration using microwave heating
60
1
20
00
140
%
%
Conversion
Selectivity
% Yield
Reaction time
In a 20 mL microwave tube Fructose (5.5mmole) was suspended
in solvent (16mL). Desired amount of PTSA (as monohydrate)
was added and then tube was purged with nitrogen before sealing.
65 The reaction mixture was stirred for 2min at room temperature
before subjecting to microwave heating. Biotage initiator 2.5 was
preꢀprogrammed to heat the vial contents to 120 ºC within 5s,
maintained for specified time and then cooled rapidly to 50 °C by
purging nitrogen and then removed from the microwave cavity to
1
1
8
6
4
2
0
20
00
0
1
8
6
4
2
0
0
0
0
0
0
0
7
7
8
0
5
0
cool further to room temperature. Samples of about 50 mg were
withdrawn from the reaction mass and appropriately diluted for
injection into HPLC.
0
For the sake of product isolation and characterization, the
reaction mixture was subjected to vacuum distillation (IPA run
samples) and the appropriate amount of water was added to the
residue and repeatedly extracted with ethyl acetate. The combined
organic layer was dried with anhydrous sodium sulfate and
filtered. The pale yellow colour ethyl acetate layer was subjected
to vacuum distillation to remove solvent giving faint yellow to
brown colour oil of HMF. Alternatively, for isolation of PTSA,
aqueous layer was polished on a hydrophobic (nonꢀionic styrene)
adsorbent column (5cm X 1cm) for removal of water soluble side
products, and then evaporated under vacuum resulting viscous
brown mass.
Conventional
MW
Fig. 7 Comparison of conventional and microwave assisted
heating reactions in IPA
Experimental
2
5
Materials and Experimental methods
The substrate fructose (98% purity), chemical reagents (pꢀtoluene
sulphonic acid) and solvents used were of commercially pure
grade obtained from local suppliers and were used as such.
3
0
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Fructose dehydration using conventional heating
Acknowledgements
The authors are grateful for financial support from the
Department of Biotechnology (DBT), Ministry of Science and
Technology India.
The fructose dehydration was carried out in 20 ml sealed glass
tube by heating oil bath. Fructose (5.5 mmoles), solvent (16 mL)
and desired amount of PTSA was suspended in tube and purged
with nitrogen before sealing. The reaction mixture was stirred for
60
5
Notes and references
2
min at room temperature and then, heated at 120 ºC for 2h. After
completion of reaction, samples were analyzed by HPLC. The
reaction work up was carried in a similar manner as described for
MW assisted synthesis.
a
DBTꢀICT Centre for Energy Biosciences, Institute of Chemical
Technology, Matunga, Mumbai 400 019, India
Fax: 91 22 3361 1020; Tel: 91 22 3361 2302;
Eꢀmail:arvindmlali@gmail.com
10
6
7
7
8
5
0
5
0
HMF characterization
b
Department of Chemical Engineering, Institute of Chemical
An NMR spectrum of the obtained product in DMSOꢀd6 was
1
Technology, Matunga, Mumbai 400 019, India
Fax: 91 22 3361 1020; Tel: 91 22 3361 2302;
Eꢀmail:arvindmlali@gmail.com
15
obtained on a Bruker Advance 300 spectrometer ( H: 300.1 MHz,
at 300°K). The spectrum was referenced against the NMR
obtained internal standard and chemical shifts are reported in
ppm. The functional group characterization was done on a
Shimadzu IR Prestigeꢀ21 instrument equipped with ATRꢀFTIR.
The mass of obtained HMF was confirmed by GCꢀMS on Agilent
†
Electronic Supplementary Information (ESI) available: Product
purification procedure, HPLC analysis chromatograms of reaction mass
and final products. Product charachterization data FTIR, GCꢀMS, QꢀTOF
20
25
30
7
890A GC coupled with 7975C inert XL EI/CT MSD triple axis
1
LCꢀMS MS, H NMR. See DOI: 10.1039/b000000x/.
detector. High resolution mass was confirmed on Agilent QꢀTOF
LCꢀMS 6520 coupled with Agilent 1200 HPLC.
1
2
3
4
K. D. Raner, C. R. Straws and R. W. Trainor, J. Org. Chem.,
995, 60, 2456ꢀ2460.
1
Characterization of the obtained HMF was as:
U. Kunz and T. Turek, Beilstein J. Org Chem., 2009, 5, DOI:
10.3762/bjoc.5.70.
1
H NMR: δH (300 MHz; DMSOꢀd6) 4.51, (d, 2H, CH ), 5.5, (s
2
1
1
H, OH), 6.5 (s 2H, Hꢀfuran ring), 7.4 (s 2H, Hꢀfuran ring), 9.5 (s
H, CHO).
V. Polshettiwar and R. S. Varma, Aqueous Microwave Assisted
Chemistry:Synthesis and Catalysis, RSC., Cambridge, 2010.
M. Nuchter, U. Muller, B. Ondruschka, A. Tied and W.
Lautenschlager, Chem.Eng.,Technol, 2003, 26, 1207ꢀ1216.
B. L. Hayes, Aldrichimica Acta., 2004, 37, 66ꢀ76.
P. Lidstrom, J. Tierney, B. Wathey and J. Westman, Tetrahedron.,
2001, 57, 9225ꢀ9283.
ꢀ
1
FTIR νmax /cm 1656.85 (CO), 3373.50 (OH), 2924.09 (CH),
850.79 (CH).
2
85
+
GCꢀMS: m/z 125.9 (M ), 108.9, 96.0, 69.0, 41.1.
5
6
QꢀTOF LCMSꢀMS: m/z 127.03792 (M+1), 109.02747, 81.03398,
5
3.03852.
7
8
9
T. Wang, M. W. Noltea and B. H. Shanks, Green chem., DOI:
10.1039/c3gc41365a.
3
5
Conclusions
90
C. Somerville, H. Youngs, C. Taylor, S. C. Davis and S. P.Long,
Science., 2010, 329, 790–791.
The sustainability of a reaction system for synthesis of 5ꢀHMF is
to be seen from many angles. While higher yield is always
desirable, the reaction times, temperatures, overall energy
consumption, and ease of downstream processing all play
important part in making a process truly friendly. The proposed
system uses reaction times of 120s, temperatures of about 120°C,
and uses low bp low latent heat solvents for achieving acceptable
conversions and yields. This is the first report on microwave
E. Taarning, C. M. Osmundsen, X. B. Yang, B. Voss, S. I. Andersen
and C. H. Christensen, Energy Environ. Sci., 2011, 4, 793–804.
95
10 X. Tong, Y. Ma and Y. Li, Appl Catal A:Gen., 2010, 385, 1–13.
40
45
50
55
1
1 R.V. Putten, J. C. V Waal, E. D. Jong, C. B. Rasrendra, H.J. Heeres
and J.G. D. Vries, Chem. Rev., 2013, 113, 1499−1597.
1
2 C. Zhou, X. Xia, C. Lin, D. Tonga and J. Beltramini, Chem. Soc. Rev.,
2
011, 40, 5588ꢀ5617.
assisted monophasic dehydration of fructose that uses
a
1
1
1
00 13. M. Bicker, J. Hirth and H. Vogel Green Chemistry, 2003, 5, 280–284.
combination of IPA as reaction medium and PTSA as catalyst in
a way capable of giving high throughputs in terms of kg/L/h in
absence of multiple liquid or solid phases. Reaction conditions
were optimized for selection of solvent, catalyst concentrations,
temperature and time of reaction to provide maximum yield. A
cursory comparison was also made with conventionally heated
reaction system and the specific role of microwave assisted
heating was demonstrated.
The new developed process gave 90% HMF yield in 90s
using IPA, a green solvent. The use of IPA was also seen to
facilitate solvent separation and recovery by simple distillation
with lower energy consumption on account of lower bp and lower
heat of vapourization.
1
1
4
J. Lewkowski, Arkivoc., 2001, 2, 17ꢀ54.
5. J. N. Chheda, Y. RománꢀLeshkov and J. A. Dumesic Green Chem.,
007, 9, 342–350.
2
1
1
6. M. E. Zakrzewska, E. BogelꢀŁukasik, and R. BogelꢀŁukasik Chem.
Rev., 2011, 111 , 397–417
05
7. Q. Zhao, L. Wang, S. Zhao, X. Wang, S. Wang Fuel., 2011, 90 2289ꢀ
2
293.
1
1
8 B. F. M. Kuster, Starch starke., 1990, 42, 314ꢀ321.
9
T. Wang , J Yomaira, P. Torres, J. Elliot, Combs, J. A. Dumesic, B.
10
H. Shanks. Top Catal., 2012, 55,657–662.
2
2
0
1
L. Lai, and Y. Zhang, ChemSusChem., 2011, 12, 1745ꢀ1748.
Y. Yang, C. Hu and M. M.AbuꢀOmar, Green chem., 2012, 14, 509ꢀ
6
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 7 of 8
RSC Advances
View Article Online
DOI: 10.1039/C4RA03137G
5
13.
S. De , S. Dutta and B. Saha, Green Chem., 2011, 13, 2859ꢀ2868.
3 J. Liu , Y. Tang , K.Wu, C. Bi and Q. Cui, Carbohyd Res., 2012, 350,
0–24.
24 T. S. Hansen, J. M. Woodely and A. Riisagar, Carbohyd. Res., 2009,
44, 2568–2572.
2
2
2
2
5
3
2
2
2
2
5
6
7
A. A. Rosatella, S. P. Simeonov, R. F. M. Fradea and C. A. M.
Afonso, Green Chem., 2011, 13, 754ꢀ793.
F. Ilgen, D. Ott, D. Kralisch, C. Reil, A. Palmbergera and B. Konig,
Green Chem., 2009, 11, 1948–1954.
1
1
2
0
5
0
F. S. Asghari and H. Yoshida, Ind. Eng. Chem. Res., 2006, 45, 2163–
2
173.
8 C. LansalotꢀMatras and C. Moreau, Catal. Commun., 2003, 4, 517–
20.
5
29 Z. Huang, W. Pan, H. Zhou, F. Qin, H. Xu, and W. Shen,
ChemSusChem ., 2013, 6, 1063 – 1069
3
0
J. M. Alia, H.G. M. Edwards and B. M. Kiernan, J. Raman
Spectrosc., 2004, 35, 111–118.
3
1 F. S. Asghari and H. Yoshida, Ind. Eng. Chem. Res., 2007, 46, 7703ꢀ
7710.
2
5
3
0
3
5
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 7

RSC Advances
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DOI: 10.1039/C4RA03137G
Graphical abstract
Microwave assisted organocatalytic synthesis of 5-hydroxymethyl
furfural in a monophasic green solvent system
a
a,b
Hitesh Pawar and Arvind Lali*
a
DBT-ICT Centre for Energy Biosciences, Institute of Chemical
Technology, Matunga, Mumbai 400 019, India
Fax: 91 22 3361 1020; Tel: 91 22 3361 2302;
E-mail:arvindmlali@gmail.com