Preparation of ionic liquid-based vilsmier reagent from novel multi-purpose dimethyl formamide-like ionic liquid and its application

Article abstract of DOI:10.1002/cjoc.201280028

In continuation of research to explore the applied potential of DMF-like ionic liquid, the ionic liquid version of N,N-dimethyliminiumchloride (Vilsmier reagent) has been synthesized from DMF-like ionic liquid and tested effectively for its capacity to achieve more useful organic transformations. The results show that DMF-like ionic liquid is world's first task specific ionic liquid which has catalyzed numerous diverse type of reaction and is multipurpose in its application. Thus a new term for this DMF-like ionic liquid has been coined that is DMF-like "multipurpose" ionic liquid. Copyright

Full text of DOI:10.1002/cjoc.201280028

FULL PAPER
DOI: 10.1002/cjoc.201280028
Preparation of Ionic Liquid-based Vilsmier Reagent from Novel
Multi-purpose Dimethyl Formamide-like Ionic Liquid and
Its Application
Hullio, Ahmed Ali*
Mastoi, G. M.
Dr. M. A Kazi Institute of Chemistry, University of Sindh Jamshoro-76080, Pakistan
In continuation of research to explore the applied potential of DMF-like ionic liquid, the ionic liquid version of
N,N-dimethyliminiumchloride (Vilsmier reagent) has been synthesized from DMF-like ionic liquid and tested effec-
tively for its capacity to achieve more useful organic transformations. The results show that DMF-like ionic liquid is
world’s first task specific ionic liquid which has catalyzed numerous diverse type of reaction and is multipurpose in
its application. Thus a new term for this DMF-like ionic liquid has been coined that is DMF-like “multipurpose”
ionic liquid.
Keywords novel concept, multipurpose DMF-like ionic liquid, ionic liquid-based vilsmier reagent, vilsmier re-
agent-catalysed reactions, TCT/DMF complex
Introduction
used as an activator of some organic or organo-metallic
reagents. Extensive literature survey reveals that there
are certain reactions which produce different results
when carried out without DMF,[10] such as conversion
of alkyl halides into alcohols via DMF-catalyzed for-
myloxylation reaction with silver salt,[11] DMF-con-
trolled chemoselective synthesis of pyrido[2,3-d]-
pyrimidine derivatives,[12] DMF-catalyzed transforma-
tion of 2-chloroethyl amides into 2-substituted-2-oxazo-
lines,[13] synthesis of 1,2-disubstituted-3,4-dihydronaph-
thalenes by DMF catalyzed cycloaddition of vinylarenes
with alkynes,[14] preparation of 1,1-dioxo-7-substituted
cephems using acid chloride obtained from DMF-cata-
lyzed reaction of correspon-ding acid with oxalyl chlo-
ride,[15] DMF-trial-kylamine catalyzed dialkylation of
diethyl 3,4-dihydroxy-2,5-thiophene dicarboxylate with
alkyl-dibromides,[16] and DMF-facilitated O-alkylation
of ethylene glycols and carboxylic acid to give diethers
and esters respectively.[17] Apart from promoting some
reactions, DMF also activates certain organic reagents
and such reagents are used as coupled with DMF. For
example Sasmita et al.[18] reported NaIO4-DMF as a
novel reagent for direct oxidation of variety of organic
halides into corresponding carbonyl compounds. Ab-
hishek et al[19] reported an efficient procedure for con-
version of a variety of alcohols into the corresponding
chlorides using pivaloyl chloride/DMF complex. Savita
et al.[20] reported a direct and efficient one-pot proce-
dure for the preparation of esters from fatty acids and
hindered alcohols using SOCl2-DMF as dehydrating
agent. 2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride,
Task specific ionic liquid is the special class of ionic
liquids in which a specific functional group is attached
to imidazole ring through carbon chain of two to six
carbon atoms. There are many organic molecules called
organocatalysts which catalyze certain organic reactions.
After the discovery of ionic liquids, some suitable func-
tional groups were attached to ionic liquid moieties. The
main object was to merge organocatalysis with ionic
liquids to make organocatalysts more efficient and re-
cyclable. Such ionic liquids infact catalyze a particular
organic reaction and act as a type of organocatalyst.
Task specific ionic liquids are designed and synthesized
for performing a given reaction under ionic liquid con-
ditions. A large amount of research work has been pub-
lished on this topic and at this stage and thus this is no
more a new concept. Many of the ordinary organo-
catalyzed reactions have been performed under ionic
liquids conditions with extra advantages.[1] Such as
Beckmann rearrangement,[2] Brönsted acidic reactions,[3]
quinuclidine-catalyzed Morita-Baylis-Hillman reac-
tions,[4] asymmetric Michael addition reactions,[5] Swern
oxidation,[6] Claisen-Schmidt reaction,[7] Mannich reac-
tion,[8] ionic liquid-supported NHPI complex.[9]
Dimethylformamide (DMF) is one of the key solvent
used in organic reactions. However there are many reac-
tions which particularly require and depend on DMF.
As a solvent, it promotes the reactions involving
charged intermediates or polar transition states by its
aprotic polar nature. In addition to this, DMF has been
*
E-mail: ahmedalihullio@yahoo.com; Fax: ＋92-22-2771372
Received April 25, 2011; accepted September 26, 2011.
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Hullio & Mastoi
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some useful transformations.[35] In addition to those re-
ported applications of DMF-like task specific ionic liq-
uid to accomplish various organic transformations, some
more quite diverse set of applications are being reported
here. The wide scope of application of this DMF-like
task specific ionic liquid is unprecedented for any task
specific ionic liquids reported so far. Normally each task
specific ionic liquid is reported with application of one
specific reaction that is why such ionic liquids are
task-specific and never beyond the reactions for which
they are designed. However increasing number of ap-
plications of DMF-like ionic suggest that it is no more
“task specific” rather it is “multipurpose” in its applica-
tions and numerous different tasks which it has accom-
plished. Thus we recommend the new term for this ionic
liquid that is “multipurpose” DMF-like ionic liquid
(MDIL) and it is world’s first functional ionic liquid
which is “multipurpose” in its applications. We reported
the synthesis of DMF-like ionic liquid with structure
containing N-methyl and N-formyl functionality as
shown in Figure 1. It was a reasonable ionic liquid
without any inherited drawbacks like viscosity.
TCT) is also an organic reagent mostly used as TCT/
DMF complex to accomplish large number of organic
transformations.[21] DMF infact activates the TCT ena-
bling it to give more efficient results. For instance, it has
been shown that TCT can promote efficiently the car-
boxylic acid activation,[22] Swern oxidation,[23] Friedel-
Crafts acylation,[24] Beckman rearrangement,[25] and
glycosyl chlorination.[26] Giacomelli has used complex
TCT/DMF to achieve a number of chemical transforma-
tions like direct conversion alcohol into corresponding
alkyl chlorides,[27] Beckmann rearrangement of different
oximes,[28] and selective protection of primary alcohols
by a formyl residue.[29] These citations prove that TCT/
DMF complex is a very powerful organic reagent.
Keeping in view the synthetic potential of the
N,N-dimethylchloromethyleneiminium chloride (Vils-
mier reagent), we decided to develop the ionic liquid
version of Vilsmier reagent and checked few Vilsmier
reagent dependent reactions. The idea consists of re-
placing the ordinary DMF with multipurpose DMF-like
ionic liquid and treating it with TCT for converting it
into ionic liquid-based Vilsmier reagent. A Vilmier re-
agent is highly reactive and moist sensitive electrophilic
specie and is prone to facile hydrolysis. Thus it is often
prepared in situ and subsequently used under inert at-
mosphere. Therefore we conceived the idea of preparing
the hydrophobic Vilsmier reagent from hydrophobic
multipurpose DMF-like ionic liquid with triflimide an-
ion. This success will lead to an easy and convenient
preparation and handling of water sensitive Vilsmier
reagent without need of cumbersome inert atmosphere.
Both hydrophobic nature and extra stability of polar
Vilsmier reagent under ionic liquid solvation effects will
result in efficient performance of Vilsmier reagent
forming quantitative amounts of products in lesser time.
Therefore the idea of developing the ionic liquid version
of TCT/DMF complex as TCT/DMF-like ionic liquid
seems to be promising. After synthesizing the required
DMF-like ionic liquid, we will test some of the Vilsmier
reagent catalyzed reactions. Such reactions include di-
rect one pot N-alkylations of phthalimide,[30] direct
conversion of alcohols into corresponding alkyl chlo-
rides and bromides,[31] Beckmann rearrangement of va-
riety of ketoximes to the corresponding amides,[32]
Lossen rearrangement of hydroxamic acids into the
corresponding isocyanates.[33] These are synthetically
powerful reactions and much research work has already
been reported about them. However most important
draw backs associated with these methodologies have
been ignored so far i.e., use of toxic chemicals, poor
yields, prolonged reaction duration, tedious work up. In
order to circumvent all these draw backs in one go,
there is one option left which is to try them under ionic
liquid conditions.
+
N
N
H
O
N
-
N(Tf)2
Figure 1 The conceived structure of proposed DMF-like task
specific ionic liquid.
Since this ionic liquid is useful and appropriate for
more than one reaction, we have coined a new term for
this that is multipurpose functional ionic liquid
(MPFIL).
Results and Discussions
Synthesis of DMF-like task specific ionic liquid
After the selection of structure for proposed MPFIL,
a reterosynthesis was carried out to develop a facile
synthetic scheme. As many synthetic routes could be
foreseen, we achieved successful synthesis of required
multipurpose functional ionic liquid by the strategy as
shown in Scheme 1.
The synthesis started with N-methylation of amino-
ethanol (1a) achieved by reductive amination with para-
formaldehyde to give N-methyl aminoethanol (1b)
through protocol reported by Sukanta et al.[36] The
N-methyl amino alcohol (1b) was converted to corre-
sponding chloro derivative (1c) by triphenyl phosphine
and tricholoroisocynuric acid.[37] At this stage N-for-
maylation was prefered over conversion of chloride (1c)
into iodide because in that stage formamide would also
facilitate the halide substitution. The N-formylation was
achived by heating the secondry amine (1c) with
ammonium formate to get the qauantitative yields of
N-choloroethyl-N-methyl formamide (1d) as reported
Hullio et al. gave the concept of designing synthesis
and application of DMF-like task specific ionic liquid[34]
and reported some of its applications in accomplishing
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Preparation of Ionic Liquid-based Vilsmier Reagent and Its Application
Scheme 1 Synthetic scheme of the proposed DMF-like task
Scheme 2 The mechanism illustrating the activation of the TCT
specific ionic liquid
by DMF
(CH2O)n/ZnCl2
H3C
CH3
+
N
NH2
NH
HO
HO
CH3
NaBH4, CH2Cl2
1a
Cl
O
1b
-
CH3
N
Cl
CHO2NH4
Trichloroisocynuric acid
Anhyd. CH3CN
N
N
N
N
H
NH
+
Cl
CH3
CH3
Anhyd. CH3CN
Cl
N
Cl
Cl
N
Cl
O
1c
2c
2a
2b
CH3
CH3
-
1-Methyl imidazole
DMF
O
NaI
H
N
N
H
H3C
I
+
N
Cl
CH3
Cl
Acetone
N
N
O
O
+
1e
1d
Cl
N
Cl
2d
2e
CH3
CH3
AgN(Tf)2
CH3CN
H
N
N
H
+N
N
+N
N
H3C
Scheme 3 The mechanism showing the activation of the TCT
H3C
-
O
O
I
N(Tf)2
1f
by DMF-like ionic liquid
1g
Cl
CH3
by Reddy et al.[38] The substitution of chloro group was
achieved through ordinary method of heating the 1d
with sodium iodide in dry acetone to get iodo derivative
(1e). The N-alkylation of imidazole was achieved by
using the methodology developed by Dupont et al.[39]
Finally the anionic metathesis of iodide salt (1f) with
triflimide was better achieved through the procedure
used by Xun.[40] Thus the successful synthesis of desired
multipurpose DMF-like ionic liquid (1g) was achieved.
N
N
N
+
N
N
H
H
+
N
N
-
Cl
Cl
N
Cl
Cl
O
N(Tf)2
3a
3b
-
O
CH3
N
+
N
N
+
+
N
-
Cl
N(Tf)2
3d
3c
The reactions testified
According to the reported procedures of all of these
four reactions, every scheme adopted the same method-
ology i.e., initially the one equivalent mole of TCT was
treated with 2.5 mol equivalents of the DMF to form the
reactive complex (2d) (Scheme 2). Remaining desired
compounds were added in required sequence. All these
reactions were conducted almost under identical ex-
perimental conditions mostly including stirring at room
temperature other at higher temperature under inert at-
mosphere. After the completion of the reactions as
shown by TLC, the reactions were quenched with water
followed by routine workup, specially the triazine
by-products were removed by aqueous workup.
Partial tabular data reproduced here show that the
products were obtained in quantitative yields. However
some of the common drawbacks associated with these
procedures were the prolonged reaction durations, for-
mation of side products and tedious and laborious
workup that followed. Use of large number of additional
chemicals like solvents during workup rendered the
procedures costly, accompanied with the generation of
toxic waste which often posed environmental issues.
The use of ionic liquid version of DMF has helped
circumvent a number of such drawbacks associated with
normal procedures and this multipurpose DMF-like
ionic liquid is proved to be instrumental in further im-
provement of the performance and efficiency of the
TCT. The number of additional advantages discovered
Since Vilsmier reagent can be synthesized from
DMF with 2,4,6-trichloro-1,3,5-triazine (TCT, cyanuric
chloride) thus it is obtained from TCT/DMF complex.
Many reactions pertaining to both synthesis and func-
tional group transformations have been achieved
through TCT/DMF complex. We are reporting the re-
sults of some of such reactions checked in multipurpose
DMF-like ionic liquid (MDIL). Before we start dis-
cussing the results obtained, let us see how TCT/DMF
complex works. Infact dimethyl formamide (DMF) re-
acts with 2,4,6-trichloro-1,3,5-triazine (TCT) to produce
N,N-dimethyl chloro methyleneiminium (2d) as a cata-
lyst promoting all of these useful transformations
(Scheme 2). It is Vilsmier-type electrophilic species that
reacts with different nucleophilic centres of various
molecules to cause required reactions.
In correspondence with above observation, we pro-
pose the ionic liquid version of 2d a dicationic highly
polar intermediate acting in ionic liquid (3c) (Scheme 3).
The TCT reacts with multipurpose DMF-like ionic liq-
uid (MDIL) in exactly same way as with ordinary DMF
to form a corresponding reactive intermediate (3c) and
all reactions reported here proceed through this di-
cationic intermediate (3c).
Therefore the results obtained may be consistent
with the mechanism depicted in Scheme 3. All four
proposed chemical transformations achieved are sum-
marized in Scheme 4.
Chin. J. Chem. 2012, 30, 1647—1657
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Hullio & Mastoi
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Scheme 4 Summary of test reactions performed through DMF-like ionic liquid
O
N:K
O
CH3
R
OH
R
OH
R
+
N
H
+
N
N
R
O
O
H3C
-
Cl
N(Tf)2
OH
Cl
HO NH
R'
O
R
R-XH
N
O
R
R'
OH
R
R'
N
X
H
R
NH
O
R'
Table 1 Comparison of N-alkylations of potassium phthalim-
ides in both reported and new methodology
accompanying the use of DMF-like multipurpose ionic
liquid include clean synthesis by minimizing the use of
chemicals, rapid and quick formation of the products
thus reduced reaction times and saving both the time
and energy, and easy recovery of the products in each
case enabling to save the labor. This observation can be
rationalized with the fact that all the reactions involved
polar transition states and charged reactive intermedi-
ates and the ionic liquid being highly polar in nature
was able to stabilize them. The DMF-like ionic liquid
has been recycled and reused with TCT without any
significant loss of the efficiency. This novel methodol-
ogy enjoys all green chemistry aspects as additional ad-
vantages, like other similar cases. Almost all of the reac-
tions being tested here proceed via highly polar reactive
intermediates which are stabilized by highly polar nature
of the reaction conditions arising from the ionic nature
of the ionic liquids used as catalyst as well assolvent.
These factors overall lead to improved procedure and
performance of the reactions conducted under ionic liq-
uids conditions.
Timea/ Yielda/ Timeb/ Yieldb/
Entry
1
Product
h
%
h
%
O
N
O
3.0
93
2.0
95
O
N
O
2
3
2.5
3.5
96
83
1.35
2.5
96
88
OMe
O
N
O
O
N
4
5
6
5.0
5.0
5.5
Nil
69
76
61
4.25
4.0
75
82
73
78
O
O
Direct N-alkylation of phthalimide with alcohols
Mokhtari et al.[30] reported the successful use of
TCT/DMF mixed reagent for one-pot direct N-alky-
lation of phthalimide by alcohols as alkylating agents
(Scheme 5). According to the author the reaction pro-
ceeded via (alcoxymethylene)dimethyl ammonium
chloride intermediate formed by reaction of 2,4,6-tri-
chloro-1,3,5-triazine and dimethyl formamide. The dif-
ferent kinds of N-alkyl phthalimides obtained were re-
ported in good-to-excellent yields (Table 1).
N
O
O
N
O
4.30
O
N
O
7
Nil 3.40
a
b
Scheme 5 TCT/DMF complex promoted direct N-alkylation of
phthalimide with alcohols
Time and yield (GC analysis) under reported conditions; time
and yield (GC analysis) under ionic liquid conditions.
O
O
TCT-DMF
-
65 ℃. Under similar conditions, potassium phthalimide
was alkylated with a wide variety of primary and sec-
ondary alcohols. The results obtained are reproduced in
Table 1. When similar reactions with same mole ratio
were performed in TCT/MPFIL complex in DMF-like
ionic liquid with acetonitrile co-solvent, some new no-
table findings were seen. Same yields of the product
N K+
N R
O
+
OH
R
DMF/CH2Cl2, 65 oC
O
The one mole equivalent of benzyl alcohol with
large excess of potassium phthalimide in the presence of
TCT/DMF complex produced N-benzylphthalimide at
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Preparation of Ionic Liquid-based Vilsmier Reagent and Its Application
were obtained, time duration reduced to almost one half
of the reported time under normal conditions. The reac-
tivity pattern was found to be similar i.e., aromatic ring
with electron donating groups furnished better yields.
However the time duration of the reaction was found to
be reduced. The interesting hydrophobic and lipophobic
nature of our ionic liquid made the workup quite simpli-
fied i.e., the used triazine byproduct was simply ex-
tracted with water and required organic product was
formed as separate layer. The data is compared in Table
1. As in case of reported normal conditions, the
DMF-like ionic liquid exhibited the same trend of reac-
tivity i.e., the primary benzylic alcohols were effectively
converted into corresponding alkylphthalimides in ex-
cellent yields. On the other hand, the yields of the
N-alkylphthalimides from the secondary alcohols were
lower than primary ones. However, contrary to the re-
ported procedure the tertiary alcohols gave successful
alkylation of phthalimide along with some chloroalkyl
byproducts. Reason for this observation can be attrib-
uted to the highly polar nature of the reaction media
where life of tertiary carbocation is increased suffi-
ciently to allow the phthalimide to attack.
Table 2 Comparison of aliphatic alcohols into the correspond-
ing alkyl halides in both reported and new methodology
Entry
Product
Timea/min Yielda/% Timeb/min Yieldb/%
15
60
96
98
15
45
96
98
Cl
Cl
2
3
Ph
240
98
150
15
98
Cl
Cl
4
5
6
7
8
15
15
15
15
15
98
97
99
97
97
98
97
99
88
81
Cl
15
15
An efficient route to alkyl chlorides from alcohols
Cl
Giacomelli et al.[31] used TCT/DMF complex for ef-
ficient conversion of different alcohols and β-amino
alcohols to the corresponding alkylchlorides. The pro-
cedure involved preparation of TCT/DMF complex and
then treating it with 1 mole equivalent of alcohol in di-
chloromethane at 25 ℃ (Scheme 6).
Br
I
15
15
15
15
Scheme 6 TCT/DMF complex promoted direct conversion of
alcohol into alkyl chloride
Cl
N
Cl
Cl
H
O
CH3
CH3
N
N
9
15
15
98
92
98
93
OH
Cl
OH
Cl
CH2Cl2, r.t.
10
Ph
Cl
Under this methodology a variety of alcohols with
structural diversity were converted to the corresponding
alkylchlorides requiring the reaction time from 10—15
min to 4 h. The procedure was also found efficacious
for special cases of sterically hindered alcohols and
diols. The sterically bulkier alcohols, such as borneol
and neopentyl alcohol took longer time. The diols gave
monochloro product using 1 mole equivalent of the diol,
and the conversion to dichloride was complete only us-
ing its 0.5 mol equivalent. The results obtained in case
of TCT/MPFIL in DMF-like ionic liquid with acetoni-
trile co-solvent furnished comparable yields (Table 2).
Although variation in yields obtained in both conditions
was not much significant except in few cases, neverthe-
less few procedural advantages of new method made it
superior to the reported one. These include rapid com-
pletion of the reaction, the easy recovery of product and
minimal use of organic solvents and recycling of
a Time and yield (GC analysis) under reported conditions; b time
and yield (GC analysis) under ionic liquid conditions.
ionic liquid. Apart from achieving the alkyl bromides
from alcohol by adding sodium bromide, as in case of
reported method, we obtained significant amount of
alkyl iodides under the new protocol by using sodium
iodide in large excess unlike reported procedure.
Tetrahydropyranylation of phenols and alcohols
Akhlaghinia[32] tested the ability of 2,4,6-trichloro-
[1,3,5]triazine without DMF for the protection of hy-
droxyl groups with 3,4-dihydro-2H-pyran and reported
the successful tetrahydropyranylation of primary, sec-
ondary and tertiary alcohols and phenols (Scheme 7).
The benzyl alcohol was converted into benzyl tetra-
hydropyranyl ether after 20 min in quantitative yield
using 1∶1∶1 mole ratio of alcohol, pyrane, and
Chin. J. Chem. 2012, 30, 1647—1657
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FULL PAPER
Scheme 7 TCT promoted direct conversion pyranylations of
Scheme 8 TCT/DMF complex promoted conversion of ketoxi-
alcohol and phenols
mes into corresponding amides
Cl
Cl
N
N
N
N
/DMF
R
R
R NH
Cl
N
Cl
Cl
N
Cl
N
+
OH
R
O
O
CH3CN
DMF, r.t.
R'
R'
R'
O
RO
O
OH
R: primary, secondary, tertary, alkyl, phenyl
what-soever were formed, and only one of the two pos-
sible amides was isolated (Table 4). The trend in tabular
data shows that electron-donating groups especially at
ortho-para positions on the aromatic ring seem to re-
duce the reaction rate. Usually, an aryl group has greater
migratory aptitude as compared to that of an alkyl group.
However, in the case of both tert-butyl phenyl ketone
oxime and the oxime of 3,3-dimethylbutan-2-one the
rearrangement gives rise to migration of the tert-butyl
group. Under new protocol, the results obtained with the
oximes of cyclic ketones proved to be much more effi-
cient, convenient and simple to obtain the commercially
useful lactams. Especially the conversion of the cyclo-
hexanone oxime is rapid under the conditions reported
and pure ε-caprolactam is recovered in a quantitative
yield.
triazine. As shown in Table 3, this method is very suit-
able for the protection of various types of alcohols and
phenols. This method exhibited the selectivity for pri-
mary alcohols in presence of secondary and tertiary al-
cohols. On performing the same reactions with similar
mole ratios in our novel multipurpose functional ionic
liquid (MFIL), some of the superior procedural advan-
tages were found. Almost same level of yields were
achieved with reduced reaction time. All types of ali-
phatic alcohols and aromatic alcohols underwent suc-
cessful pyranylations. As in case of other reactions
tested under this methodology, easy recovery of product
and clean synthesis were achieved. In all schemes only
selected compounds were tested depending upon the
requirement for illustrating the effectiveness of the pro-
posed methodology. The comparison of tabular data
suggests that the new method is proved to be much
more efficient than the one reported.
Aldoximes apparently show different reaction trend,
forming corresponding nitriles rapidly and quantita-
tively under the same conditions (Scheme 9).
We performed Beckmann rearrangement according
to both the reported procedure as well as new method-
ology and results are shown in Table 5. The differences
in outcomes of both methodologies are self explanatory.
Under the new protocol 1 mole equivalent of different
oximes were added to TCT/MFIL. The reaction was
stirred at room temperature until all reactants were
found to have been consumed as indicated by TLC.
Theevaluation and comparison of the data in Table 5,
reveals the superiority of the new methodology over the
one with which it is being compared. For every entry,
Beckmann rearrangement of different oximes to
amides and nitriles
Giacomelli et al.[27] used TCT/DMF complex to
achieve quantitative conversion of ketoximes into the
corresponding amides and aldoximes to nitriles (Scheme
8).
This reaction was also selected for its scope in new
multipurpose functional ionic liquid and it was found to
be superior to the reported one from many aspects. The
reaction duration was narrowed, no side products
Table 3 Comparison of preparation of THP ethers in both reported and new methodology
Entry
1
Product
Timea
Yield/%a
Timeb
Yield/%b
93
8 h
90
5 h
OTHF
OTHF
2
3
4
5
44 h
97
96
90
68
32 h
30 min
16 h
95
95
90
73
OTHF
35 min
O
OTHF
N
28 h
34 h
OH
26 h
a Time and yield (GC analysis) under reported condition; b time and yield (GC analysis) under ionic liquid conditions.
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Preparation of Ionic Liquid-based Vilsmier Reagent and Its Application
Scheme 9 TCT/DMF complex promoted conversion of aldoxi-
mes into corresponding nitriles
min. Two equivalents of EtOH were then added at 0 ℃
and the reaction mixture was refluxed overnight to af-
ford carbamate in 87% yield. With other nucleophiles
including alcohols, thiols, and amines the corresponding
carbamates, thiocarbamate, and ureas, respectively,
were obtained in good to excellent yields (73%—99%).
The execution of this last test reaction under our new
procedure produced the same trend and observations as
evident from the Table 6. The better performance of the
novel strategy in this case verifies the multipurpose na-
ture of the proposed ionic liquid. The every hydroxamic
acid and N-methylmorpholine was treated with TCT/
MFIL complex dissolved in acetonitrile in reported
mole ratio and stirred at room temperature under nitro-
gen for required time. The reaction mixture was stirred
at higher temperature after addition of suitable nucleo-
phile like alcohol, amine or thiol. The results obtained
were much better as shown in Table 6 due to the same
reasons as described earlier.
Cl
N
N
/DMF
R
H
R
H
Cl
N
Cl
O
N
R
N
DMF, r.t., 4 h
OH
100%
enhanced yields in lesser time duration is quite vivid.
The compatibility of new methodology with structural
diversity is amply evident from the starting substances.
The essential reason for the better yields and lesser time
duration lies in highly polar nature of the reactions con-
ditions arising from the ionic nature of the ionic liquids
used as catalyst as well as solvent. All of these reactions
involve polar intermediates and charged species formed
in almost every cases reported here, which are highly
stabilized by powerful polar solvation by the ionic liq-
uids. This stability results in higher yields coupled with
lower reaction time.
Experimental Section
The Lossen rearrangement
Hamona et al.[34] reported a TCT-promoted Lossen
rearrangement of hydroxamic acids to form isocyanates
which were subsequently in situ trapped with different
nucleophiles (R2XH) to form carbamates and thiocar-
bamates in a one-pot procedure (Scheme 10).
As a model reaction, the phenylcarbamic acid ethyl
ester was prepared directly from benzohydroxamic acid.
According to the reported procedure, the best results
were obtained by using 0.4 equiv. of TCT in the pres-
ence of an excess of N-methylmorpholine (2 equiv.) in
dichloroethane under stirring the mixture at 0 ℃ for 90
General
All the reagents and solvents were pure and of ana-
lytical grade chemicals purchased from Aldrich and
were used without further purification. Melting/boiling
points were determined with a Buchi 510 melting point
apparatus (Flawi/SG, Switzerland) and are uncorrected.
Electron impact (EIMS) mass spectra were determined
with a Finniggan MAT-312 (Bremen, Germany), Vrain
MAT-112 (Bremen, Germany) double focusing mass
spectrometer connected to a PDP 11/34 (DEC) com-
1
puter system. The H NMR spectra were recorded in
Table 4 Comparison of conversion of ketoximes into amides in both reported and new methodology
Entry
1
Oxime
Amide
Timea/h
Yielda/%
Timeb/h
Yieldb/%
100
Ph
Ph NH
N
OH
O
6
100
3
Me
Me
N OH
HO
NH
HO
2
3
6
80
80
2.5
8
80
80
O
Me
Me
O2N
O2N
N OH
Me
NH
12
O
Me
H
O
N
N
OH
4
5
3
100
83
2
100
83
H
O
N
N
OH
12
7.5
a Time and yield (GC analysis) under reported conditions; b time and yield (GC analysis) under ionic liquid conditions.
Chin. J. Chem. 2012, 30, 1647—1657
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
1653

Hullio & Mastoi
Table 5 Comparison of conversion of aldoximes to corresponding nitriles in both reported and new procedure
FULL PAPER
Entry
1
Oxime
Nitrile
Timea/h
Yielda/%
Timeb/h
Yieldb/%
N
4
85
2.0
88
N
H
OH
HO
Cl
HO
Cl
N
N
2
3
4
5
6
5
89
92
94
96
2.5
2.5
2.5
3.0
94
92
94
96
N
H
OH
N
H
OH
OH
OH
5.5
N
N
N
H
H
OH
6
N
OH
a Time and yield (GC analysis) under reported conditions; b time and yield (GC analysis) under ionic liquid conditions.
Table 6 Comparison of hydroxamic acids rearrangement to isocyanates and its further reaction in both reported and new methodology
Entry
1
R1CONHOH
R2XH
R1NHCOXR2
Yielda/%
87
Yieldb/%
94
O
H
OH
N
O
N
H
OH
O
O
O
O
O
O
H
OH
OH
OH
OH
OH
N
O
2
3
4
5
6
84
81
73
99
88
92
88
85
99
94
N
H
OH
O
H
N
O
N
H
OH
O
H
SH
N
S
N
H
O
O
O
H
N
H
N
NH2
N
H
H
N
O
NH2
N
H
a Yield (GC analysis) under reported conditions; b yield (GC analysis) under ionic liquid conditions.
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Chin. J. Chem. 2012, 30, 1647—1657

Preparation of Ionic Liquid-based Vilsmier Reagent and Its Application
Scheme 10 TCT/DMF complex promoted Lossen rearrange-
ment of hydroxamic acids and in situ capturing isocyanates with
different nucleophiles
mL×4) diethylether. The organic layers were combined,
concentrated and dired over Na2SO4. The product was
further purified with flash chromatography to give 44.51
g (70%) 2-chloro, N-methyl ethylamine as cololess
liquid with b.p. 109—111 ℃.
Cl
Spectral data: 1H NMR (DCCl3, 400 MHz) δ: 2.54 (d,
N
N
O
O
Cl
N
Cl
4J3,2＝0.63 Hz, 3H, H-2), 2.72 (d, 3J4,3＝6 Hz, 2H, H-3),
R2
OH
R'
3
R'
N
N
X
(1) NMM, DCE, 0 oC
2.96 (s-broad, 1H, H-1), 3.50 (t, J4,3＝6 Hz, 2H, H-4);
H
H
13CNMR (CDCl3, 300 MHz) δ: (34.93, CH3) (42.34,
CH2) (57.55, CH2); HRMS (ESI) calcd for C3H8ClN
(M＋) 93.555, found 93.550.
(2) R2XH, 0 oC to reflux
X = O, S, NH
CD3OD and CDCl3 with Bruker AM 300 and 400 spec-
trometers (Rheinstetten-Forchheim, Germany) operating
at 300 an 400 MHz, respectively. The purity of the
products was checked on TLC plates (Merck, Darmstadt,
Germany), coated with silica gel PF254 and the spots
were characterized with UV light at 254 and 366 nm
and by spraying with ninhydrin and iodine tank.
N-(2-Chloroethyl)-N-methyl formamide (1d) To
a solution of N-methyl-2-chloroethyl amine (44.51 g,
0.48 mol) in dry acetonitrile (500 mL) was added anhy-
drous ammonium formate (45.36 g, 0.72 mol) and the
resulting mixture was heated at 95 ℃ (bath tempera-
ture) for 15 h. Acetonitrile was removed under reduced
pressure. The residue was diluted with ethyl acetate
(200 mL) and washed with distilled water (50 mL×4).
The organic layer was concentrated and dried over an-
hydrous Na2SO4 and then further purified by flash chro-
matography to yield (51.84 g, 90%) colorless liquid
formamide.
Synthesis scheme of DMF-like ionic liquid
N-Methyl 2-aminoethanol (1b) In 200 mL round
bottom flask, a mixture of amino ethanol (30 g, 0.491
mol), zinc chloride (133.85 g, 0.982 mol), paraformal-
dehyde (29.49 g, 0.982 mol), in dichloromethane (150
mL) was stirred at room temperature for 1 h under dry
atmosphere. Sodium borohydride (37.14 g, 0.982 mol)
was then added and resulting mixture was stirred for 18
h. The progress of the reaction was monitored by TLC
using ninhydrin reagent. The reaction mixture was then
quenched by addition of aqueous ammonia (200 mL, 2
Spectral data: 1H NMR (DCCl3, 400 MHz) δ: 3.22 (s,
3
3
3H), 3.58 (t, J6,5＝6.68 Hz, 2H, H-6), 3.92 (t, J6,5＝
6.68 Hz, 4J5,2a＝0.63 Hz, 4J5,4＝0.63 Hz, 2H, H-5), 8.02
(s, 1H, H-2a); 13C NMR (CDCl3, 300 MHz) δ: 31.99
(CH3), 44.62 (CH2), 59.58 (CH2), 165.06 (CHO).
HRMS (ESI) calcd for C4H8ClNO (M＋) 121.565, found
121.568.
－
1
mol•L ), stirred for 10 min and the organic layer was
separated. The aqueous part was extracted with di-
chloromethane (25 mL×1), the combined organic ex-
tracts were concentrated in vacuo after drying over an-
hydrous Na2CO3. The crude product was purified by the
flash chromatography over neutral alumina using hex-
ane∶diethyl ether (3∶1) as the eluent to yield 51 g
(72%) of pure N-methylaminoethanol as a colorless liq-
uid product; b.p. 150—155 ℃.
N-(2-Iodoethyl)-N-methyl formamide (2e) A so-
lution of N-(2-chloroethyl)-N-methyl formamide (iii)
(51.84 g, 0.24 mol) in 25 mL of anhydrous acetone was
added dropwise to a stirred solution of NaI (37.5 g, 0.25
mol) in 250 mL of anhydrous acetone over a period of
45 min at room temperature. The stirring was continued
for 20 h. The precipitate formed was collected by filtra-
tion and washed with 100 mL of acetone. The combined
filtrate was evaporated and residue was distilled to give
colourless oil. And it was further purified by flash chro-
matography to give 66.34 g, 73% yield.
Spectral data: 1H NMR (DCCl3, 400 MHz) δ: 2.35 (d,
3
4J3,5＝0.63 Hz, 3H, H-5), 2.60 (dd, 2H, J2,3＝5.5 Hz,
4J3,5＝0.63 Hz, H-3), 3.54 (t, J2,3＝5.5 Hz, 2H, H-2),
3
Spectral data: 1H NMR (DCCl3, 400 MHz) δ: 3.24 (s,
3.64 (s-broad, 1H, H-1); 13C NMR (300 MHz, CDCl3) δ:
(36.05, CH3), (54.30, CH2), (60.30, CH2); MSEI m/z
(%): 75 (M＋＋40), 74 (49), 73 (10), 44 (100), 31 (15);
HRMS (ESI) calcd for C3H9NO (M＋) 75.110, found
75.108.
3
3H, H-4), 3.60 (t, J6,5＝7.77 Hz, 2H, H-6), 4.00 (t,
4
4
3J6,5＝7.77 Hz, J5,4＝0.63 Hz, J5,2a＝0.63 Hz, 2H,
H-5), 7.79 (s, 1H, H-2a); 13C NMR (CDCl3, 300 MHz) δ:
－0.60 (CH2), 32.59 (CH3), 56.10 (CH2), 164.39 (CHO);
HRMS (ESI) calcd for C4H8INO (M＋) 213.017, found
213.016.
N-(2-Chloroethyl)-N-methyl amine (1c)
Ph3P
(267.5 g, 1.02 mol) was disolved in 200 mL anhydrous
acetonnitrile in a 300 mL round-bottom flask. Then 83.7
g (0.36 mol) of tricholoroisocynuric acid was added
slowly over about 30 min. The reaction mixture was
stirred and heated at 60 ℃. Then N-methylamino-
ethanol (51 g, 0.68 mol) was added to the mixture, and
the reaction was stirred for 3 h. On completion of the
reaction 10 mL water was added to quench the reaction.
Most of the acetonitrile was removed by rotary
evaporator and residue was extracted with 100 mL (25
1-[2-(Formylamino)ethyl]-3-methyl-1H-imidazol-
3-ium iodide (2f) Freshly distilled N-methyl imida-
zole (19.7 g, 0.24 mol) and 66.34 g (0.31 mol) of
N-(2-iodoethyl)-N-methyl formamide (2e), were added
to 100 mL of acetonitrile (CH3CN) and brought to re-
flux with stirring under nitrogen at 80 ℃ for 24 h. Af-
ter completion of reaction as evident from TLC analysis
the reaction mixture was cooled to room temperature. A
solid compound was collected during cooling process.
The acetonitrile was removed by rotary evaporator un-
Chin. J. Chem. 2012, 30, 1647—1657
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www.cjc.wiley-vch.de
1655

Hullio & Mastoi
FULL PAPER
der vacuo. The resulting white solid was washed with
ethyl acetate, dried under reduced pressure at 30 ℃ for
6 h to afford imidazolium iodide (2f) (46.56 g, 89%).
compounds are available.
Recycling efficiency
1
The proposed ionic liquid system was tested for its
recycling potential with different type of reactions. Each
cycle was tested with fresh DMF-like ionic liquid and
recycling was found to be fairly consistent for four
times. The results found are shown in (Table 7).
Spectral data: H NMR (CD3OD, 400 MHz) δ: 3.16
3
4
(s, 3H, H-11), 3.92 (t, J6,7＝6.63 Hz, J2,6＝0.6 Hz,
5J4,6＝0.3 Hz, J5,6＝0.4 Hz, 2H, H-6), 4.19 (t, J6,7＝
4
3
4
4
6.63 Hz, J7,9a＝0.63 Hz, J7,11＝0.63 Hz, 2H, H-7),
7.40 (s, 1H, H-5), 7.70 (s, 1H, H-4), 7.98 (s, 1H, H-2),
7.75 (s, 1H, H-9a); 13CNMR (CDCl3, 300 MHz) δ:
32.26 (CH3), 37.20, 46.97 (CH2), 51.27 (CH2), 116.41
(CH), 123.30 (CH), 140.28 (CH), 161.49 (CHO);
HRMS (ESI) calcd for C8H14N3O (M＋) 168.216, found
168.219.
Table 7 Recycling efficiency of the DMF-like ionic liquid
No. of recycles
Product yielda/%
Product yieldb/%
Product yieldc/%
Product yieldd/%
1
95
2
3
4
93
97
92
98
92
95
91
97
89
94
90
95
98
1-[2-(Formylamino)ethyl]-3-methyl-1H-imidazol-
3-ium triflimide (2g) To a solution of 1-[2-(formyl-
95
100
amino)-ethyl]-3-methyl-1H-imidazol-3-ium
iodide
(46.56 g, 0.16 mol) in dry acetonitrile (20 mL) was
added silver triflimide (62.08 g, 0.16 mol). The mixture
was stirred for 2 h in the dark under nitrogen. The mix-
ture was filtered to remove the light yellow salt and the
filtrate was evaporated by rotary evaporation under
vacuum and dried in vacuo to generate the product 2g as
a clear liquid with a very light brown color (67 g, 100%
yield).
The recycling studies were performed with N-benzylation of
phthalimidea, benzyl alcohol to benzyl chlorideb, pyranation of
4-methoxy benzyl alcoholc, acetophenone oxime to phenyl
acetamided. Yielda-d (GC analysis) of products.
Conclusions
A stable and hydrophobic ionic liquid based Vilsmier
reagent has been prepared from multipurpose DMF-like
ionic liquids. It has been shown to be more stable and
efficient organocatalyst as compared to Vilsmier reagent
prepared from ordinary DMF for some useful organic
transformations. The successful execution of all these
reaction proves that our DMF-like ionic liquid is a mul-
tipurpose ionic liquid.
1
Spectral data: H NMR (400 MHz, CD3OD) δ: 3.16
(s, 3H, H-12), 3.75 (s, 3H, H-11), 3.82 (t, 4J2,6＝0.6 Hz,
4
3
5J4,6＝0.3 Hz, J5,6＝0.4 Hz, J6,7＝6.63 Hz, 2H, H-6),
4.08 (t, 3J6,7＝6.63 Hz, 4J7,9a＝0.63 Hz, 4J7,12＝0.63 Hz,
2H, H-7), 7.75 (s, 1H, H-9a), 8.40 (s, 1H, H-5), 8.65 (s,
1H, H-4), 8.47 (s, 1H, H-2); 13CNMR (CDCl3, 300 MHz)
δ: (32.26, CH3) (37.20, CH3) (46.97, CH2) (51.27, CH2)
(116.41, CH) (123.30, CH) (140.28, CH) (161.49,
CHO), (108.84, 116.71, 124.59, 132.46, CF3); HRMS
(ESI) calcd for C8H14N3O (M＋) 168.216, found 168.218
Acknowledgment
The authors thankfully acknowledge the Higher
Education Commission (HEC) of Pakistan for financial
support and H.E.J International Centre for Chemical and
Biological Research, Karachi for provision of spectro-
scopic facilities.
General reported procedure for testing of reactions
in multi-purpose functional ionic liquid (MPFIL)
For each run of test reactions, the activated complex
of TCT-MDIL was prepared by mixing the Tri-
chloro-1,3,5-triazine (0.183 g, 1.0 mmol) and ionic liq-
uid (1.06 g, 2.5 mmol) by stirring both at 25 ℃ in 10
mL acetonitrile as co-solvent to reduce the viscosity.
After preparation of Vilsmier reagent, each of reaction
was tested by running the required number of test. For
each test of a given type of reaction, required mole ratio
of the reactants were introduced in the activated com-
plex in acetonitrile. The resulting reaction mixture was
stirred at required temperatures until the TLC showed
the completion of reaction. After completion of reac-
tions the consumed cyanuric chloride was extracted
with water and product was extracted with diethyl ether,
organic layer was concentrated and dried with Na2SO4.
After evaporation of the solvent the product was further
purified by flash column chromatography using ethyl
acetate/n-hexane (1/10) as the eluent. The products were
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