Chitosan supported ionic liquid: A recyclable wet and dry catalyst for the direct conversion of aldehydes into nitriles and amides under mild conditions

Article abstract of DOI:10.1039/c3ra43440k

A green and highly efficient chitosan supported magnetic ionic liquid (CSMIL) was synthesized with chitosan (the most abundant biopolymer in nature and a cheap industrial waste product), methyl imidazole and anhydrous/hydrous FeCl₃. The heterogeneous catalyst thus obtained was used for the direct conversion of aldehydes to the corresponding nitriles in the presence of NH₂OH·HCl/dry-CSMIL/MeSO₂Cl and amides with NH ₂OH·HCl/wet-CSMIL/MeSO₂Cl. A highlight of our approach is the easy separation of the catalyst from the reaction medium and thus the recyclability of the catalyst. This simple method can be applied to obtain a wide range of aromatic, heterocyclic, and aliphatic nitriles and amides.

Full text of DOI:10.1039/c3ra43440k

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: S. Mohammadi
and A. Khalafi-Nezhad, RSC Adv., 2014, DOI: 10.1039/C3RA43440K.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Page 1 of 7
RSC Advances
View Article Online
Chitosan supported magnetic ionic liquid (CSMIL) as an efficient catalyst for the direct conversion of
DOI: 10.1039/C3RA43440K
aldehydes to nitriles and amides
NH2OH.HCl, MsCl, dry-CSMIL
(A)
R
C
N
OH
HO
O
O
NH
n
RCHO
N
N
FeCl4
O
(B)
R
C
NH2
NH2OH.HCl, MsCl, wet-CSMIL

Evaluation OJnlyo. Cureartend waithlAsNposea.PmDF. Ceopyright 2002-2021 Aspose Pty Ltd.
RSC Advances
Page 2 of 7
Dynamic Article Links ►
View Article Online
DOI: 10.1039/C3RA43440K
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Chitosan Supported Ionic Liquid: A Recyclable Wet and Dry Catalyst
for Direct Conversion of Aldehydes into Nitriles and Amides under mild
conditions
5
Ali Khalafi-Nezhad a* and Somayeh Mohammadi a
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
A green and highly efficient chitosan supported magnetic ionic liquid (CSMIL) was synthesized with
chitosan (the most abundant biopolymers in nature and cheap industrial waste), ethyl methyl imidazole
10 and anhydrouse/hydrouse FeCl3. The heterogeneous catalyst thus obtained used for the direct conversion
of aldehydes to the corresponding nitriles in the presence of NH2OH. HCl /dryꢀCSMIL / MeSO2Cl and
amides with NH2OH. HCl /wetꢀCSMIL / MeSO2Cl. A highlight of our approach is easy separation of
catalyst from the reaction medium and so on recyclability of the catalyst. This simple method is
applicable to access a wide range of aromatic, heterocyclic, and aliphatic aldehydes.
15
attractive utilizations.6,7
1. Introduction
The unique and tunable physical and chemical properties of ionic
In the recent years, development of pollution prevention research
has been broad due to growing environmental concerns. In this
respect, heterogeneous catalysis is generally preferred to
20 homogeneous catalysis mainly because of the easy recovering
and possible recycling of the catalyst, simple experimental
procedures, mild reaction conditions and minimization of
chemical wastes as compared to the liquid phase counterparts.
Very recently, natural materials, in particular biopolymers for
25 catalytic applications are attracting increasing interest as
liquids (IL) make this class of molecules as particularly a green
solvent suitable for a range of organic reactions, and providing
50 possibilities such as control of product distribution,8 enhanced
9
10
11
rates and/or reactivity, ease of product recovery, catalyst
immobilization, 12 and recycling. 13,14
In this work, we reveal a new biopolymer supported ionic liquid
based on dry FeCl3 and FeCl3.3H2O to produce both wet and dry
55 heterogeneous catalyst.
The nitrile moiety is an important constituent in different natural
products, and considerable precursor for the synthesis of amines,
amides, ketones, carboxylic acids and esters. There are diverse
methods for the synthesis of nitrile groups from different organic
60 functional groups.15 Among these, the direct conversion of
aldehydes into corresponding nitriles has been shown to be an
attractive and important strategy for the preparation of nitriles in
organic transformations.16 Until now, several methods have been
reported for the conversion of aldehydes to nitriles via
65 dehydration of aldoximes such as using Pd(OAc)2/PPh3,17 Nꢀ(pꢀ
1
environmentally benign polymeric supports for catalysts.
Carbohydrates are one of the most diverse and important classes
of biomolecules in nature. These renewable polymers largely
used in some applications such as adhesives, absorbents,
30 lubricants, soil conditioners, drug delivery, textiles and high
strength structural materials. 2
Among biopolymers, chitosan (CS), is the second abundant
polysaccharide next to cellulose in nature and is estimated to be
produced annually almost as much as cellulose and can be found
35 in industrial waste.3 chitosan is a potential excellent material used
as support for catalytic applications in heterogeneous molecular
catalysis due to its hydrophilicity, chemical reactivity, unique
threeꢀdimensional structure, presence of hydroxyl and amino
groups, excellent chelating property, and mechanical
40 properties.4,5 Morever, chitosan is environmental friendly
because it can be degraded by soil and water microorganisms.
There has been much scientific and industrial interest in utilizing
chitin and chitosan for different applications such as
pharmaceutical, waste water treatment, cosmetics, drug delivery,
45 heavy metal chelation, heterogeneous catalysts and many other
toluenesulfonyl)
imidazole
(TsIm),18
[RuCl2(pꢀ
cymene)]2/molecular sieves,19 2ꢀchloroꢀ1ꢀmethyl pyridinium
iodide,20 triethyl amine/SO2,21 PPh3/CCl4,22 acetic anhydride,23
Vilsmeier reagent,24 Burgess reagent,25 cyanuric chloride,26 diꢀ2ꢀ
70 pyridylsulfite,27 AlI3,28 TiCl3(OTf),29 AlCl3. 6H2O/KI,30
chlorosulfonic acid,31 and S,Sꢀdimethyl dithiocarbonate.32
Although all of these methods are valuable, most of them have
one or more of the following drawbacks: less readily available
reagents, harsh reaction conditions, low yields, refluxing for a
75 prolonged period of time, tedious workup of the reaction mixture,
use of expensive metals and toxic oxidants. Hence, it is of great
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Page 3 of 7
RSC Advances
View Article Online
DOI: 10.1039/C3RA43440K
practical importance to develop a more efficient and also
condition was undertaken to increase the yield of the product
environmentally benign method that avoids all of these 50 using different amounts of CSMIL. The yield was increased to
drawbacks for the conversion of aldoximes into nitriles.
96% using 15 mg of CSMIL under solventꢀfree conditions.
Morever, We screened a variety of solvents and examined their
effect on reaction time and yield (Table 1). Use of DMF, DMSO,
MeCN (Table 1, entries 5ꢀ7) led to moderate yields of 4ꢀ
Herein, as part of our ongoing study on the application of this
new green catalyst in organic synthesis,33 we would like to
present the direct oxidative conversion of aldehydes into the
5
corresponding nitriles and amides by treatment with hydroxyl 55 nitrobenzonitrile; whereas, the reaction proceeded in the absence
amine hydrochloride and mesyl chloride under solvent free
condition at 70 ºC in the presence of dry and wet chitosan
10 supported magnetic ionic liquid (CSMIL) (Scheme 1).
of solvent and the best yields of the nitrile was attained.
Therefore, solventꢀfree (entry 8) was found to be the most
appropriate condition and was used for all subsequent reactions.
Additionally, we also evaluated the effect of temperature on the
60 progress of the model reaction (entries 8 and 9). The best result
was obtained at 70 ºC. Further increases in temperature caused no
distinguishable improvement in the progress of the reaction that
is because of the gelification of chitosan in the structure of
catalyst at high temperature.
65
N
N
i)
15
Scheme 1. Direct conversion of aldehydes into the corresponding nitriles
Cl
N
N
(method A), and amides (method B) in the presence of CSMIL
Cl
OH NH2
Result and discussion
OH NH2
ii)
20 Catalyst preparation
OH
OH NH2
NH2
Dry and wet catalyst was prepared and characterized based on the
following procedure (Scheme 2) (see the supporting information).
FeCl3.3H2O
FeCl3
25 Optimization of reaction
wet-CSMIL
dry-CSMIL
OH
In our initial studies, effect of different catalyst on the outcome of
the reaction was considered. For this reason, the conversion of p-
bromobenzaldehyde to the p-bromobenzonitril, as standard
30 model, was considered. The reaction was performed using
mixture containing 1 mmol of pꢀbromobenzaldehyde, 1.2 mmol
of hydroxylamine hydrochloride, 1.2 mmol of mesyl chloride,
and different amounts of catalysts (Table 1). It was confirmed by
the results that no product is obtained when the reaction is carried
35 out without catalyst (Table 1, entry 1). When FeCl3 was used as a
solid catalyst, the reaction time and the yield of product were
unsatisfied (Table 1, entries 2–7). By using a typical IL such as
butyl methyl imidazolium chloride [BMIm][Cl] as solvent system
for FeCl3 as a catalyst, 70% yields of the product was obtained
40 after 12h, respectively (Table 1, entry 8). In comparison with
[BMIm][Cl], butyl methyl imidazolium tetrachloro ferrate
[BMIm]FeCl4 as solventꢀcatalyst increased the yield up to 75% in
a shorter reaction time (Table 1, entry 9). But unfortunatly, the
separation and reuse of the [BMIm]FeCl4 from the product
45 wasn’t so perfect. Therefore, with the new catalyst at hand, we
have decided to use of chitosan supported magnetic ionic liquid
(CSMIL) as a heterogeneous catalyst. The use of 8 mg of CSMIL
afforded 84% of the desired nitrile. Optimization of the reaction
O
HO
O
HN
N
N
n
FeCl4
CSMIL
70
Scheme 2. Preparation of chitosan supported magnetic ionic liquid
(CSMIL); i) 1,2ꢀ dichloro ethane, acetone, 25 °C, ii) chitosan,
isopropanol, 25 °C
75
Table 1. Effect of solvent on the conversion of 4ꢀnitrobenzaldehyde into
4ꢀnitrobenzonitrile a
2
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]