Tetrahedron Letters
Application of glucose derived magnetic solid acid for etherification
of 5-HMF to 5-EMF, dehydration of sorbitol to isosorbide, and
esterification of fatty acids
⇑
Raju S. Thombal, Vrushali H. Jadhav
Division of Organic Chemistry, National Chemical Laboratory (CSIR-NCL), Pune 411008, India
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study, the catalytic activity of Glu-Fe O -SO H was evaluated for three acid catalyzed reactions:
3
4
3
Received 14 June 2016
Revised 12 August 2016
Accepted 19 August 2016
Available online 21 August 2016
etherification of 5-hydroxymethylfurfural (5-HMF) to 5-ethoxymethylfurfural (5-EMF) in ethanol, dehy-
dration of sorbitol to isosorbide, and esterification of fatty acids with good yields and selectivity.
Moreover, the catalyst can be easily separated from the reaction with an external magnetic force and
reused at least five times without a significant decrease in catalytic activity.
Ó 2016 Elsevier Ltd. All rights reserved.
Keywords:
Dehydration
Etherification
Esterification
Magnetic
The recent developments in the efficiency of the conversion of
biomass into chemical materials have been of growing interest in
sustainable chemistry. Synthesis of renewable fuels and value
added chemicals from biomass generally require acidic materials.
into automobile fuel systems, which can cause premature wear.
Hence, production of EMF directly from HMF by etherification with
ethanol has drawn increasing attention recently. Isosorbide,7
,8
a
material useful for polymer synthesis such as polycarbonates or
polyesters, is important for the preparation of chemical feedstocks
from biomass. Isosorbide is used for treating glaucoma, brain
hypertension, and Ménière’s disease while isosorbide nitrates are
medicines for angina pectoris. Though numbers of methodologies
2 4
Homogeneous acid catalysts, e.g., mineral acids such as H SO ,
1
HCl have been used to catalyze such reactions. Homogeneous cat-
alysts have several disadvantages, i.e., they are corrosive, expen-
sive, forms large amount of waste by-products, and difficult to
separate from the reaction medium. Hence heterogeneous cata-
lysts have gained a lot of importance these days as they are greener
and recyclable. Further compared to conventional heterogeneous
solid acid catalyst, magnetic solid acids can be easily separated
in the presence of external magnetic field particularly in viscous
9
–13
are reported for synthesis of isosorbide from sorbitol,
still there
is a need to develop an green and efficient procedure. Biodiesel is
an environmentally friendly fuel since it is biodegradable, sustain-
1
4
able, and non-toxic. Biodiesel is a mixture of long chain fatty acid
methyl esters (FAME) produced from free fatty acids, vegetable oil,
animal oil, or waste oil via esterification, and/or trans-esterification
or solid reaction mixtures.2
-Ethoxymethylfurfural (EMF),3 has gained increasing impor-
–6
with alcohols using acid or base. Base catalysts are generally not
15
5
tance as a promising biofuel, since physical and chemical proper-
ties of this ether (liquid form at room temperature, high cetane
number, good oxidation stability) make it a very interesting bio-
fuel. Also, the energy density of EMF is 29% greater than that of
ethanol and very close to that of diesel. Previously 5-EMF was syn-
thesized from 5-CMF which in turn was obtained from 5-HMF.
While this process gives high yields of EMF, there are concerns
about HCl recyclability and the introduction of unreacted halides
favoured as they react with fatty acids to form soaps and decrease
the yield of biodiesel products. Highly reactive homogeneous
Brønsted acid catalysts are efficient for this process, but they suffer
from serious contamination and corrosion problems that require
the implementation of good separation and purification steps.
Hence there is a need to develop ideal heterogeneous catalysts that
are cheap, not easily leachable, capable to efficiently catalyze the
reaction with high yields and selectivity, easily separable, and
5
1
6–18
reusable.
Glu-Fe
Herein, we studied our recently synthesized
1
9
3
O
4
-SO
3
H
catalyst and showed its application for etherifi-
⇑
cation of 5-HMF to 5-EMF, dehydration of sorbitol to isosorbide,
and esterification of fatty acids.
040-4039/Ó 2016 Elsevier Ltd. All rights reserved.
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