Direct transformation of 5-hydroxymethylfurfural to the building blocks 2,5-dihydroxymethylfurfural (DHMF) and 5-hydroxymethyl furanoic acid (HMFA) via Cannizzaro reaction

Article abstract of DOI:10.1039/c3gc40930a

An efficient, simple, scalable and atom efficient method for the synthesis of 2,5-dihydroxymethylfuran (DHMF) and 5-hydroxymethylfuranoic acid, as sodium salt (HMFA), in 80% yield from 5-hydroxymethylfurfural (HMF) in water using NaOH (0.9 eq.) via a Cannizzaro reaction is described. Both the building blocks DHMF and HMFA were successfully isolated merely using selective crystallisation.

Full text of DOI:10.1039/c3gc40930a

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Direct transformation of 5-hydroxymethylfurfural to
the building blocks 2,5-dihydroxymethylfurfural
(DHMF) and 5-hydroxymethyl furanoic acid (HMFA) via
Cannizzaro reaction†
Cite this: DOI: 10.1039/c3gc40930a
Sowmiah Subbiah,a,b Svilen P. Simeonov,b José M. S. S. Esperança,a
Luís Paulo N. Rebeloa and Carlos A. M. Afonso*b
Received 19th May 2013,
Accepted 5th August 2013
An efficient, simple, scalable and atom efficient method for the synthesis of 2,5-dihydroxymethylfuran
(DHMF) and 5-hydroxymethylfuranoic acid, as sodium salt (HMFA), in 80% yield from 5-hydroxymethyl-
furfural (HMF) in water using NaOH (0.9 eq.) via a Cannizzaro reaction is described. Both the building
blocks DHMF and HMFA were successfully isolated merely using selective crystallisation.
DOI: 10.1039/c3gc40930a
www.rsc.org/greenchem
1. Introduction
The economics of biomass production have improved over the
years, as the growing concern about the depletion of tra-
ditional energy resources has made biomass seem a more
attractive alternative both as an energy source and for the
chemical industry. 5-Hydroxymethylfurfural (HMF), the so-
called ‘sleeping giant’,1 is a new biomass-derived platform
chemical and it has great industrial potential as it is one of
the new building blocks readily accessible from renewable
resources.2 The most versatile intermediate chemicals of great
industrial potential that can be generated from HMF in simple
large-scale transformations are as follows: 5-hydroxymethylfur-
anoic acid (HMFA), 2,5-furandicarboxylic acid, 2,5-dihydroxy-
methyl furan (DHMF), and 2,5-furandicarboxaldehyde (Fig. 1).
HMF possesses two functionalities attached to a furan ring
that help to convert several value-added compounds useful in
a wide variety of chemical manufacturing applications and
industrial products.2,3
Fig. 1 Intermediates with great industrial potential produced from 5-HMF.
2,5-dihydroxymethyl tetrahydrofuran can be used like alkane
diol in the preparation of polyesters. DHMF is used as a six-
carbon monomer in a broad range of applications such as
resins, polymers and artificial fibers.4,5 5-Hydroxymethylfura-
noic acid (HMFA) serves not only as a novel component in
various polyesters6 but also as a precursor to 2,5-furandi-
carboxylic acid (FDCA) with many potential applications in the
polymer field. 2,5-Furandicarboxylic acid can potentially
replace terephthalic, isophthalic, and adipic acids that have
been used to date in the manufacture of polyamides, poly-
esters, and polyurethanes.7,8 It has also been used as an inter-
mediate in the synthesis of drugs9 and crown ethers.10
Moreover, HMF has been used for the production of special
phenolic resins11 and numerous other polymerizable furanic
monomers with promising properties have been prepared.7
Due to the potential industrial importance of HMF, the
synthetic and related interest in the chemical conversions of
HMF remains undiminished. Several studies regarding DHMF
For example, 2,5-furancarboxaldehyde is a starting material
for the preparation of Schiff bases, and 2,5-diaminomethyl furan
is able to replace hexamethylenediamine in the preparation of
polyamides. 2,5-Dihydroxymethylfuran (DHMF) is used in the
manufacture of polyurethane foams3 and the fully saturated
aInstituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa,
Av. da Republica, 2780-157 Oeiras, Portugal
biMed. UL, Faculdade de Farmacia da Universidade de Lisboa, Av. Prof. Gama Pinto,
1649-003, Lisboa, Portugal. E-mail: carlosafonso@ff.ul.pt; Fax: +351 21 7946476
†Electronic supplementary information (ESI) available: Experimental proce-
dures, spectral data, additional results, photographs of the isolation procedures
and copies of 1H and 13C NMR spectra. See DOI: 10.1039/c3gc40930a
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refrigerator. After evaporation of the mother liquor, DHMF
(0.4 g, 27% yield) was isolated.
Isolated DHMF: 87% yield, 98% purity.
Isolated HMFA salt: 83% yield, 95% purity.
The diol DHMF can be further purified by washing with
ether–hexane to remove any remaining non-polar impurities.
Several batch experiments were successfully performed at
different quantities of HMF with this purification process
under different conditions (Table 5).
Scheme 1
synthesis have been carried out based on the catalytic
reduction of HMF: its hydrogenation in the presence of nickel,
copper, platinum, palladium or ruthenium catalysts, for
instance.12 Under noncatalytic conditions, the reductions with
sodium borohydride have also been reported.10,13 Research
into the conversion of HMF to HMFA has mainly focused on
catalytic oxidation.14 Using heterogeneous oxidation systems,
good to excellent results have been reported.15 Very recently,
oxidative studies of HMF to provide potential derivatives like
HMFA, 2,5-furandicarboxaldehyde, and 2,5-furandicarboxylic
acid are being explored.16
3. Results and discussion
Our aim was to optimize the synthesis and purification of
DHMF and HMFA via the Cannizzaro reaction with HMF.
Initially, we started a screening with different bases to ascer-
tain the reactivity of HMF (Table 1 and Scheme 1).
The reaction with NaH base in dry THF occurred quickly,
within 4 hours (89%, entry 1), while for the NaOH base in
water, it took longer (81%, entry 2). With potassium tert-but-
oxide in acetonitrile, the reaction produced 33% overall yield in
12 hours. Other bases such as Ba(OH)2, Ca(OH)2 or K2CO3 did
not provide the Cannizzaro product (entries 4–6) or for Li2CO3
gave low yield (7%, entry 3). Since promising results were
obtained with NaH and NaOH, we then tried to analyse the
importance of the hydroxyl group in HMF for the Cannizzaro
reaction. We performed a reaction with HMF, TBDMS (tert-
butyldimethylsilyl) protected HMF and furfural for the study
with different solvents and bases (Table 2 and Scheme 2).
While performing the reaction at higher temperatures,
40 °C and 60 °C, with NaOH, the reaction for HMF produced
lower yields (62% and 22%) (Table 2, entries 4 and 5) which is
probably due to competitive known decomposition of HMF
under basic conditions.3f,g With TBDMS-protected HMF, the
reaction of NaOH with H2O underwent hydrolysis leading to
Cannizzaro products (29%) (Table 2, entry 7), while the same
with NaH yielded corresponding Cannizzaro products in 37%
yield for 12 h at 0 °C (Table 2, entry 8). The reaction with
A Cannizzaro reaction is the base-induced disproportio-
nation reaction of an aldehyde lacking a hydrogen atom at an
α-position to the carbonyl group. One molecule of the alde-
hyde acts as a hydride donor while the other functions as an
acceptor, resulting in a carboxylic acid salt and an alcohol
product, respectively. The Cannizzaro reaction is of limited use
as it produces an equimolar mixture of both products, when
only one of them is the interesting/target molecule. However,
when applied to HMF, the Cannizzaro reaction would be one
of the most efficient routes for the simultaneous production of
DHMF and HMFA both of which are equally important poten-
tial derivatives of HMF and circumvents the need of an oxidant
(for HMFA) or a reductor (for DHMF). Another advantage of
the Cannizzaro reaction over the standard reduction or oxi-
dation conditions for HMF is the relative affordability and lack
of toxicity of hydroxide ions. Herein we report an efficient,
operationally simple, and eco-friendly Cannizzaro reaction of
HMF (Scheme 1). Very little research, only two studies, on the
Cannizzaro reaction of HMF is available (1910 and 1919), both
of which employed an aqueous alkali solution.17 To the best of
our knowledge, only very recently has the formation of DHMF
and HMFA from HMF in an ionic liquid been reported.18
Table 1 Screening with various basesa
Yieldb (%)
2. Experimental
2.1. General procedure for the Cannizzaro reaction of HMF
and product isolation
Entry
Base
Solvent
Time (h)
DHMF
HMFA
1
2
3
4
5
6
7
NaH
Dry THF
Water
Water
Water
Water
Water
CH3CN
4
36
12
12
12
12
12
90
82
7
NR
NR
NR
31
89
81
7
NR
NR
NR
34
3 g of HMF (24 mmol)2c was dissolved in water (30 ml) and
then cooled to 0 °C. After the addition of 0.87 g (22 mmol) of
NaOH at 0 °C, the resulting mixture was stirred at room temp-
erature in a closed vessel for about 18 h and the reaction com-
pletion was next confirmed by TLC. After evaporating the water
from the reaction mixture, ethyl acetate (2 × 50 ml) was added
NaOH
Li2CO3
Ba(OH)2
Ca(OH)2
K2CO3
KOtBu
a General conditions: 100 mg of HMF (0.8 mmol) was dissolved in the
to the solid to separate the DHMF diol (0.85 g, 60%). Carboxy- corresponding solvent (4 ml) at 0 °C, the base (0.88 mmol) was added
in a closed vial and stirred at room temperature and the reaction
late salt HMFA was isolated by recrystallization with ethanol
(approx. 2 ml)–ethyl acetate (100 ml) yielding an HMFA salt
was monitored by TLC. b Yield determined by proton NMR using
1 equivalent of sodium acetate (NaOAc, 0.8 mmol) as an internal
(1.4 g, 83% yield) as a hygroscopic solid which was stored in a standard. NR represents ‘no reaction’ was observed by NMR.
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Table 2 Screening with specific conditionsa
Yieldb (%)
Entry
Substrate
Base
Solvent
Temp (°C)
Time (h)
DHMF
HMFA
1
2
3
4
5
6
7
8
9
HMF
HMF
HMF
HMF
NaH
THF
0 to RT
RT
0 to RT
40
4
18
22
24
24
12
12
12
12
12
90
86
71
62
23
NR
39c
37
68
88
89
87
69
60
21
NR
20c
36
71
83
NaOH
NaOH
NaOH
NaOH
NaOH
NaOH
NaH
Water
MeOH
Water
Water
MeOH
Water
THF
HMF
60
TBDMSMF
TBDMSMF
TBDMSMF
Furfurald
Furfurald
0 to RT
0 to RT
0 to RT
0 to RT
0 to RT
NaH
NaOH
THF
Water
10
a General conditions: to the aldehyde (0.8 mmol; 0.4 mmol for entries 2 and 3) with the corresponding solvent (4 ml), 1.1 equivalent base was
added in a closed vial at the specified temperature and the reaction was monitored by TLC. b Yield determined by proton NMR using
1 equivalent of NaOAc (0.8 mmol) as an internal standard. In particular, for reactions with 50 mg HMF, 0.2 equiv. NaOAc (0.16 mmol) in entry 2
and 0.05 equiv. NaOAc (0.04 mmol) in entry 3 were used. c The hydrolysis of TBDMS produced HMF followed by its Cannizzaro products.
d Isolated yields of hydroxymethylfuran and furanoic acid. RT, room temperature; NR, no reaction.
With the best conditions in hand, we explored the simple
purification methods for obtaining both HMFA and DHMF
individually without the need for column chromatography or
acid–base separation techniques, since they led to significant
losses of Cannizzaro products. Our simpler process is based
on the recrystallization technique, in which we obtained more
Scheme 2
than 60% of 97% pure DHMF before recrystallization. Follow-
ing the process, we achieved 98% pure recrystallized product
HMFA (82%)19 and around 27% diol was easily purified from
furfural proceeded well, producing corresponding Cannizzaro
the mother liquor by washing with ether–hexane (total yield of
DHMF = 85%, Table 3, results in brackets). In order to mini-
mize the production of NaOH waste, we explored the reaction
at different equivalences of NaOH (Table 4). We observed a
significant drop in yield using stoichiometric amounts of
NaOH (0.5 equivalent, 32%, entry 1), 10% (43%, entry 3) or
20% excess (52%, entry 6). Using 10% excess of NaOH, longer
reaction time (72 h vs. 48 h) resulted in higher overall yield
(70% vs. 43%, entry 4 vs. entry 3). In line with the results
described before (Table 2), the use of higher temperature
(45 °C vs. rt) did not improve the reaction performance (40%
vs. 43%, entry 5 vs. entry 3). In addition, the increase of the
reaction scale (500 mg vs. 50 mg) provoked an erosion of the
overall yield (17% vs. 31%, entry 2 and 60% vs. 70%, entry 4)
which was not observed when NaOH was used in higher excess.
products with both NaH and NaOH bases in good yields, 70%
and 86%, respectively (Table 2, entries 9 and 10).
From these studies, the best conditions were obtained
using NaH and NaOH. To analyse the specific conditions, we
compared the obtained results of NaH and NaOH at 0 °C and
room temperature conditions by also varying the substrate–
solvent concentration at these temperatures.
As Table 3 illustrates, using a more concentrated reaction
medium (2 ml vs. 20 ml) reduced the NaH reaction efficiency
from 0 °C to room temperature (90% vs. 68%) whereas with
NaOH, a slight improvement was obtained (82% vs. 87%). The
best conditions were using NaOH at room temperature in H2O
for 18 hours to give 86% yield of DHMF and 87% yield of
HMFA salt; these conditions avoided the need for the organic
solvent THF.
Table 3 Screening for specific conditions for HMFa
NaH
NaOH
Conditions
0 °C to RT
RT
0 °C to RT
RT
Concentration
Time (h)
100 mg in 20 ml THF
1 h (0 °C) to 3 h (RT)
90
89
50 mg in 2 ml THF
3
69
66
100 mg in 20 ml H2O
1 h (0 °C) to 35 h (RT)
82(82)
50 mg in 2 ml H2O
18
86
87
Yieldb (%): DHMF
HMFA
81(85)
a General conditions: to 100 mg of HMF (0.8 mmol) with the corresponding solvent at 0 °C, the base (0.88 mmol) was added in a closed vial and
stirred at room temperature; the reaction was monitored by TLC. b Yield determined by proton NMR using 1 equivalent of NaOAc (0.8 mmol) as
an internal standard. In particular, for reactions with 50 mg HMF at room temperature, 0.2 equiv. of NaOAc (0.16 mmol) was used. In brackets
are provided the observed isolated yields.
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Table 4 Screening of NaOH quantitya
DHMF and HMFA by crystallization rather than an acid base
extraction. A scalable, simply purified, high yield reaction
would make the present process even more useful and
attractive.
Yieldb (%)
DHMF
Entry
NaOH (equiv.)
Time (h)/Temp (°C)
HMFA
1
2
3
4
5
6
7
8
0.5
0.5
0.55
0.55
0.55
0.6
38/rt
18/45
48/rt
72/rt
48/45
48/rt
48/rt
18/rt
28
35
30 (15)c
46
32 (20)c
40
Acknowledgements
71 (61)c
38c
53
80
86
69 (60)c
42c
51
81
87
This research work was supported by grants Pest-OE/SAU/
UI4013/2011,
PEst-OE/EQB/LA0004/2011,
PTDC/QUI-QUI/
0.9
1.1
119823/2010 and Ph.D. fellowship SFRH/BD/74088/2010 from
the Fundacão para a Ciência e Tecnologia (FCT).
a General conditions: to 50 mg of HMF (0.4 mmol) in water (2 ml) at
0 °C, NaOH (varying equivalents) was added in a closed vial and after
1 h was stirred at a specific temperature; the reaction was monitored
by TLC. b Yield determined by proton NMR using 0.05 equivalent of
NaOAc (0.04 mmol) as an internal standard. After reaction, the water
was evaporated and the mixture was washed with diethylether and
dried before preparing the NMR sample to remove any unreacted
HMF. c Observed yields (in brackets) using 500 mg of HMF.
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Table 5 Cannizzaro reaction of HMF and product isolationa
Yieldb (%)
Entry HMF scale Water (ml)/concentration (M) DHMF HMFA
1
2
3
4
5
6
0.1 g
0.1 g
1 g
3 g
3 g
20 ml/40 mM
4 ml/0.2 M
60 ml/0.13 M
120 ml/0.2 M
30 ml/0.8 M
200 ml/0.5 M
82
88
90
85
87
85
85
84
85
83
83
82
12 g
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eq.) was added in a closed vial and after 1 h was stirred at room
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yield.
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of 80% and 86% respectively (entries 7 and 8).
Besides the use of an excess of NaOH that implies less
green chemistry credits due to the need of more base and the
generation of more waste, we selected 0.9 equivalent of NaOH
as the most appropriate compromise for the following studies
of reaction and product isolation at a higher reaction scale
(Table 5). As can be seen, the transformation can be efficiently
performed under different concentrations (40 mM to 0.8 M)
and scales to up to 12 g (95 mmol) of HMF, providing isolated
85% yield of DHMF and 82% of HMFA salt (entry 6). Those
conditions correspond to an E-factor of 0.3 since the reaction
medium (water) and the solvent of crystallization can be
reused by distillation.
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