Ionic liquids: Anion effect on the reaction of O,O-diethyl O-(2,4-dinitrophenyl) phosphate triester with piperidine

Article abstract of DOI:10.1039/c4nj02121e

The reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester (1) with piperidine in ionic liquids and four conventional organic solvents (COS) were subjected to kinetic and product studies. Analytical techniques (UV-vis and NMR) identified two pathways: nucleophilic attack at the phosphoryl center and at the C-1 aromatic carbon. The nucleophilic rate constants (kTN) for these parallel reactions were separated into two terms: kPN and kArN for the corresponding electrophilic centers. Both the rate and the selectivities of the reactions are strongly dependent on the nature of the ionic liquid used, and a good correlation with the solvent acceptor capacity to form hydrogen bonds (β) was observed. Remarkably, an exclusive attack at the phosphoryl center was found using [Bmim]DCA, [Bmpyrr]DCA and [Bmpy]DCA as the reaction solvents. In contrast, with [Bmim]PF₆ as the reaction solvent, attack at the C-1 aromatic was the main path (94%). These results suggest that ionic liquids can be considered to be designer solvents because by an appropriate choice of the anion it is possible to steer the selectivity of this reaction. This journal is

Full text of DOI:10.1039/c4nj02121e

NJC
View Article Online
View Journal
PAPER
Ionic liquids: anion effect on the reaction
of O,O-diethyl O-(2,4-dinitrophenyl) phosphate
triester with piperidine†
Cite this:DOI: 10.1039/c4nj02121e
Paulina Pavez,‡*a Daniela Millan,a Cristian Cocq,a Jose G. Santosa and Faruk Nomeb
´
´
The reactions of O,O-diethyl 2,4-dinitrophenylphosphate triester (1) with piperidine in ionic liquids and
four conventional organic solvents (COS) were subjected to kinetic and product studies. Analytical
techniques (UV-vis and NMR) identified two pathways: nucleophilic attack at the phosphoryl center and at
the C-1 aromatic carbon. The nucleophilic rate constants (kTN) for these parallel reactions were separated
into two terms: kNP and kANr for the corresponding electrophilic centers. Both the rate and the selectivities
of the reactions are strongly dependent on the nature of the ionic liquid used, and a good correlation with
the solvent acceptor capacity to form hydrogen bonds (b) was observed. Remarkably, an exclusive attack
at the phosphoryl center was found using [Bmim]DCA, [Bmpyrr]DCA and [Bmpy]DCA as the reaction
solvents. In contrast, with [Bmim]PF6 as the reaction solvent, attack at the C-1 aromatic was the main path
(94%). These results suggest that ionic liquids can be considered to be designer solvents because by an
appropriate choice of the anion it is possible to steer the selectivity of this reaction.
Received (in Porto Alegre, Brazil)
24th November 2014,
Accepted 22nd December 2014
DOI: 10.1039/c4nj02121e
www.rsc.org/njc
(from X-ray diffraction to molecular dynamic modeling) have
been used.11
1. Introduction
Ionic liquids (ILs), which are typically composed of organic
The multiple cation/anion combinations available for the
cations and inorganic anions, have been considered a new class synthesis of ILs can lead to dramatic changes in the physico-
of solvents for many organic reactions. They have attracted chemical properties of these solvents. This potential has led to
considerable attention due to their remarkable properties: ionic liquids being described as ‘‘designer solvents’’. This suggests
negligible vapor pressure, non-flammable and non-corrosive, that for every chemical reaction of interest, it is possible to
and can dissolve a significant number of organic species.1 The design a solvent to improve the reaction times and avoid
current literature describes the successful use of ILs as reaction undesired products.1c,12 Of particular interest is a study of the
media in Friedel–Crafts,2 Diels–Alder,3 chlorination,4 enzyme reactions between toluene and nitric acid, where three completely
catalysis,5 polymerization,6 oxidation7 and hydrogenation reactions.8 different products were obtained by using three different ionic
Among the main advantages reported on the use of ILs as solvents, liquids.13 The reactions of pyrrole and other nitrogen heterocycles
great improvements in yield, control of product distribution, with various alkyl halides have been found to favor C-alkylation,14
enhanced rate, ease of product recovery, catalyst immobilization, and in the rearrangement of heterocycles derived from oxadiazole,
and the possibility of recycling can be mentioned.1c Nevertheless, D’anna et al. reported a large increase in reactivity in going from
their application is sometimes limited by uncertainty on how ILs conventional solvents to ILs.15 Finally, Kim et al. reported enhanced
affect the reaction outcome.9 To understand solute-solvent inter- reactivity and improved selectivity in both the fluorination of
actions in these organic salts, solvent parameter such as a, b, p*,10 2-(3-methanesulfonyloxypropyl)naphthalene in ([bmim][BF4])16
and physico-chemical investigations of their complex structures and the hydroxylation of 2-(3-bromopropyl)naphthalene.17 Thus,
ILs play crucial roles, such as increasing the rates, reducing the
formation of unwanted products and promoting mechanistic
a
´
´
Facultad de Quımica, Pontificia Universidad Catolica de Chile, Casilla 306,
Santiago 6094411, Chile. E-mail: ppavezg@uc.cl; Fax: +56-02-26864744;
Tel: +56-02-23541743
changes, as those observed in the aminolysis of some esters,
carboxylic acids and phenyl-substituted ethanes. In these cases,
the stabilization of the reaction intermediate has been proposed
to be responsible for the change in mechanism.18
In addition, it is well known that phosphate esters containing
both alkyl and aryl substituents can exhibit three reaction path-
ways for nucleophilic attack: (i) that at the phosphorus center,
b
´
´
INCT-Catalise, Departamento de Quımica, Universidade Federal de Santa Catarina,
´
Florianopolis, SC, 88040-970, Brasil
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c4nj02121e
´
´
‡ Present address: Facultad de Quımica, Pontificia Universidad Catolica de Chile,
˜
Av. Vicuna Mackenna 4860, Santiago 6094411, Chile.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
Scheme 1 Schematic representation of the reaction studied and the anions and cations of the ionic liquids used.
SN2(P),19 (ii) that at the aromatic moiety, SNAr,20 and (iii) that at UV-vis spectrophotometry and the product analyses by UV–vis
the aliphatic carbon, SN2(C).21 Recently, we have demonstrated and 31P NMR.
that the reaction of paraoxon with piperidine in ILs occurs
via three simultaneous reaction paths,22 whereas the same
2. Results and discussion
2.1 Rates and selectivity
reaction in aqueous solution proceeds with exclusive phosphoryl
attack.19c
Bearing in mind these precedents, our particular interest is
focused on the possibility that ILs may substantially alter the
reactivity in parallel nucleophilic substitution reactions of phosphate
esters, yielding more than one reaction product. To improve
our understanding of the effect of ILs as solvents on rate and
product distribution, we examined the reaction of O,O-diethyl
2,4-dinitrophenyl phosphate triester (1) with piperidine in
twelve ionic liquids, as shown in Scheme 1.
The combination of different cations and anions, shown in
Scheme 1, provides ILs with different structures and diverse
chemical properties, such as hydrogen bonding and hydrogen
acidity abilities, which may be important for rationalizing the
solvent–substrate interactions in these types of reactions. To
compare the results in ILs, we carried out the same reaction in
Rate constants for the reaction of 1 with piperidine using ILs
and common solvents were determined spectrophotometrically.
The rate law for all the reactions studied is given by eqn (1),
where P and S represent one of the products and substrate 1,
respectively. First-order rate constants (kobsd) were obtained in
the presence of total piperidine excess and are shown in Tables
S1 and S2 in ESI.† The plots of kobsd against nucleophile
concentration were linear, according to eqn (2), where kTN is the
nucleophilic rate coefficient.
d½Pꢀ
¼ kobsd½Sꢀ
(1)
dt
kobsd ¼ k0 þ kTN½NHꢀ
(2)
solvents, such as acetonitrile, DMSO and water, under the same All these plots showed a slightly negative intercept when the
experimental conditions, following the kinetic experiments by solvent was an ionic liquid. This behavior was reported before
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
Table 1 Second-order rate constants (kTN) for the reaction of 1 with
piperidine in ILs and other solvents, at 25 1C
produced as a result of amine attack at the phosphoryl moiety.
Conversely, in the other solvents a band near 380 nm was found,
suggesting a more complex kinetic behavior.
Solvent
kTN b/Mꢁ1 sꢁ1
Fig. 1 shows the 31P NMR spectra obtained for the reaction of 1
with piperidine in [Bmim]BF4. The figure shows the disappearance
of the signal at ꢁ7.68 ppm, due to 1, and the simultaneous
appearance of two signals, one at 8.89 and the other at 0.19 ppm,
corresponding to O,O-diethyl piperidinophosphate diester (2a)
and O,O-diethyl phosphate acid (2b), respectively, in agreement
with Scheme 2. The signals at 0.19 and 8.89 were assigned by
comparison with authentic samples of the products obtained
by the reactions of piperidine and NaOH with O,O-diethyl
chlorophosphate in the same IL, respectively, as shown in Fig. S1
and S2, in ESI.†
H2O
0.66
0.30
1.82
6.87
4.42
1.81
7.80
4.36
1.24
1.45
3.28
2.95
4.50
7.55
4.35
EtOH : H2O (50%/v)a
ACN
DMSO
[Bmim]BF4
[Bmim]PF6
[Bmim]DCA
[Bmim]OTf
[Bmim]NTf2
[Bmpyrr]NTf2
[Em2pAm]NTf2
[B2mim]NTf2
[B2mim]BF4
[Bmpyrr]DCA
[Bmpyrr]OTf
The 31P-NMR spectra recorded at the end of the reaction of 1
with piperidine in all the ionic solvents studied and also in
other common solvents are shown in Figures S3–S14 in ESI.†
The results show similar behavior in most of the solvents
a
b
Ref. 24. Second-order rate constants were reproducible within ꢂ5%.
for ILs derived from imidazole,23 and was attributed to an acid– studied and that the nucleophilic attack towards the phos-
base interaction between the acidic imidazolium ion and the phoryl center competes with the attack at the C-1 aromatic
amine. The values of kTN for the reaction of 1 with piperidine in carbon, as shown in Scheme 2. Nevertheless, in those ILs that
various solvents are shown in Table 1.
share a common DCA anion, only the signal at 8.89 ppm in the
The data in Table 1 show that the kTN values in ILs are larger 31P NMR spectra was observed (see Fig. S15–S17, in ESI†). This
than those found in aqueous solutions, but similar to or lower is in accordance with the exclusive formation of O,O-diethyl
than those found in DMSO. This result is not surprising piperidinophosphate diester (2a); this result is consistent with
because the polarity and structure of DMSO lead to a consider- the UV-vis spectral analysis, which indicates the formation of
able organization in the liquid state, the same as in ILs.25 2,4-dinitrophenoxide (3a).
Product studies using UV-vis spectrophotometry show that for the
Integration of the 31P NMR signals of the products formed
reactions of ILs based on the DCA anion, the reaction is slightly from piperidine attack on 1 allowed the calculation of the
faster and the final spectra correspond to 2,4-dinitrophenoxide product distribution in the different reaction media. The results
Fig. 1 31P-NMR spectra obtained for the reaction of 1 (0.4 M) with piperidine (neat) at 25 1C in [Bmim]BF4 as solvent. (A) Initial time and (B) the end of the
reaction.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
Scheme 2 Nucleophilic attack of piperidine (RNH) on 1 in ILs, DMSO, ACN and aqueous solutions, by two reactions paths: (a) attack at phosphorus; and
(b) attack at the aromatic C-1.
Fig. 2 Nucleophilic attack of piperidine on 1 compared for ILs and other solvents. The dark gray areas represent the SN2(P) pathway, with attack of
piperidine at the phosphorus atom, and the light gray areas represent the SNAr pathway, with attack at the C-1 aromatic carbon.
are summarized in Table S3 in ESI.† Fig. 2 shows this behavior These results suggest that ionic liquids can be considered as
schematically.
designer solvents for these reactions because by the appropriate
The results agree with previous reports showing that slight choice of the anion it is possible to control the selectivity of this
modifications in the ILs’ cation or anion nature can induce reaction.
selectivity changes for some reactions.10c,26 In most of the ILs
For the parallel reaction shown in Scheme 2, the second-order
employed, the SN2(Ar) pathway (light gray contribution in rate constants kTN are the sum of the individual rate constants
Fig. 2) is the most important (70–97%), and the results are kTN = kNP + kNAr where kNP and kANr are the rate constants for nucleophilic
consistent with those obtained in the degradation of paraoxon attack at P and at the aromatic C-1, respectively. Using the products
in ILs, where SNAr reactions are favored when ILs are used as distribution shown in Table S3 in the ESI† and the data in Table 1,
solvents.22 However, an important effect of the solvent on the values of the individual second order rate constants kNP and kANr were
selectivity of an amine attack is apparent, which changes from calculated and are given in Table 2.
100% attack on the phosphoryl group with [Bmim]DCA,
Examining the values in Table 2, we can clearly observe the
[Bmpyrr]DCA and [Bmpy]DCA as solvents, to 94% of attack at importance of the anion in the rate constant by comparing ILs
the aromatic C-1 in the substrate when [Bmim]PF6 is the solvent. with a common cation [Bmim], where the kPN increases 78 times,
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
increasing from 0.10 to 7.8 when NTf2 is replaced by DCA.
Nevertheless, when comparing ILs that share a common NTf2
anion, little difference was found: the kPN values increase from
0.1 to 0.46 when [Bmim] is substituted by [Em2pAm], suggesting
that the cation has only a minor effect on the rate. These results
are in accordance with those of Harper et al. for an SN2 process
(Menschutkin reaction), where the change of the IL cation does
not affect the outcome of the reaction.9,27 Nevertheless, this
finding cannot be generalized because of the different inter-
actions of the IL with the starting materials and various species
along the reaction coordinate.
It is interesting to note that the couples [Bmim]NTf2-[Bmpyrr]-
NTf2, [Bmpyrr]OTf-[Bmin]OTf and [B2mim]BF4-[Bmim]BF4 (see
Fig. S18, in ESI†) present similar values of kANr, suggesting that
the C-1 aromatic attack is mostly affected by the anion, and the
change of the cation practically does not affect the reaction rate.
Similarly, the effect of the acidity loss due to the blockage of
Fig. 3 Correlation between log kPN and the solvent hydrogen bond acceptor
the 2-position of the imidazolium ring28 shows modest changes in capacity (b) for a series of ionic liquids.
kANr, which may be analyzed by comparing [Bmim]NTf2 with
[B2mim]NTf2 (or comparing [Bmim]BF4 with [B2mim]BF4).
kNp
kpN þ kANr
À
Á
parameters: fNp
¼
. A treatment based on a multi-
Hughes–Ingold theory predicts that an increase in solvent
dielectric constant (polarity) would enhance the kPN and kNAr
values. Our results reveal that this is not the case because we
found a poor correlation of the rate constant kPN and kNAr with the
polarity parameter ET(30) (not shown). To rationalize how the
individual rate constants depend on the nature of the ILs, we tried
to correlate them by using Kamlet–Taft parameters (Table S4, in
ESI†). We found a good correlation between log kPN and the hydro-
gen bond acceptor capacity of the solvent (b), as shown in Fig. 3
(log kPN = ꢁ1.68(0.12) + 3.79(0.29)b; R = 0.95). The introduction of a,
p* or both parameters in the fit does not give a better correlation
(see Table S5 in ESI†). Conversely, log kANr does not correlate well
with the solvent parameter b, a result that is reasonable because
reactions at the phosphorus and aromatic centers proceed with
different mechanisms.
parameter regression with respect to Kamlet–Taft solvent
descriptors (a, b and p*) failed when the data from conven-
tional solvents were analyzed together with those from ILs.
Nonetheless, a good correlation with the b parameter was
obtained; a plot of log ( f pN) vs. b of the ionic liquids is shown
in Fig. 4. (log ( f pN) = ꢁ1.62(0.02) + 2.29(0.01)b; R = 0.96).
It is noteworthy that the kinetic parameter log kPN presents a
linear correlation with b (Fig. 3), while the plot of log kANr vs. b is
not linear (Fig. S17, ESI†). This different behavior can be related
to the different structures of the intermediates in their corres-
ponding mechanisms. Moreover, the semilog plot of selectivity
(obtained either from the kinetic or from the product distribu-
tion) against b is linear, showing a dependence even though
log kANr vs. b is not linear. This can be explained because the
By using the data from Table 2, the selectivity of the reaction
in each solvent was calculated. The selectivity of the amine
attack on the phosphoryl group ( f pN) is defined by the kinetic
Table 2 Second-order rate constants for the reactions at the phosphoryl
center (kPN) and at the C-1 aromatic carbon (kANr
)
Solvent
kPN b/Mꢁ1 sꢁ1
kANr b/Mꢁ1 sꢁ1
H2O
0.17
0.09
0.27
3.37
0.88
0.11
7.80
1.35
0.10
0.17
0.46
0.30
0.68
7.55
1.09
0.49
0.21
1.55
3.50
3.54
1.70
0
3.01
1.14
1.28
2.82
2.65
3.82
0
EtOH : H2O (50% v/v)a
ACN
DMSO
[Bmim]BF4
[Bmim]PF6
[Bmim]DCA
[Bmim]OTf
[Bmim]NTf2
[Bmpyrr]NTf2
[Em2pAm]NTf2
[B2mim]NTf2
[B2mim]BF4
[Bmpyrr]DCA
[Bmpyrr]OTf
3.26
Fig. 4 Correlation between log(f Np
acceptor capacity (b) for a series of ionic liquids.
) and the solvent hydrogen bond
a
b
Ref. 24. Second-order rate constants were reproducible within ꢂ5%.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.

View Article Online
Paper
NJC
selectivity can be obtained from the kinetics results; however, (kobsd) were found for all reactions. Each sample was made in
the selectivity is a thermodynamic property. triplicate. These were obtained by means of the kinetic software
In this work, we have demonstrated that the reaction is of the spectrophotometer, at the wavelength where the greatest
selective to the phosphoryl group in ILs that share the DCA absorbance change was observed. The nucleophilic rate con-
anion, and the attack at the C-1 aromatic increases as the anion stants (log kTN) were obtained as the slope of linear plots of
basicity decreases at the point of 94% in [Bmim]PF6; probably kobsd vs. free nucleophile concentration. The separation of kTN into
the design of an IL in which the reaction will be selective to the kPN (the nucleophilic rate constant for the phosphoryl center) and
aromatic attack must contain an anion less basic than PF6.
kANr (the nucleophilic rate constant for the C-1 aromatic carbon) was
It is noteworthy that DMSO has the greatest b value (0.760), performed considering the quantitative product analysis (see
higher than any of the ILs used, though attack on the phosphoryl below) and the fact that for parallel reactions kTN = kNP + kNAr.
moiety is not 100%. The results suggest that the hydrogen bond
4.3 Product studies
acceptor capacity b of the ILs is not the only parameter to be
considered and also the structural organization of these solvents29
should be taken into account. However, there are a lot of studies on
how ionic liquids affect reaction outcomes such as reaction rate
and selectivity (see ref. 30 and references therein).
To determine the products of the studied reactions, 31P-NMR
spectra were obtained on an AM-400 instrument in all the
solvents used in this study (ILs and COS).
At the end of the reactions of 1 with piperidine in the ILs
sharing the DCA anion, the 31P NMR spectra showed only
one signal at 8.89 ppm attributed to O,O-diethyl piperidine
phosphate, in comparison with that of the product of the
reaction of O,O-diethyl chlorophosphate with piperidine. More-
over, the UV-vis spectra at the end of the reactions correspond to
2,4-dinitrophenoxide in comparison with an authentic sample.
For the reactions of 1 with piperidine in other solvents, the
31P NMR spectra show 2 signals that correspond to O,O-diethylamine
phosphate and to O,O-diethyl phosphoric acid, in comparison with
authentic samples prepared using O,O-diethyl chlorophosphate. The
31P NMR signals for the products for the reactions are summarized
in Fig. S1–S21 in ESI.† It is noteworthy that the ratio of products was
independent of the concentration of 1 and piperidine.
3. Conclusions
The reaction of 1 with piperidine in ILs that share the anion
DCA is specifically at the phosphoryl group, while in [Bmim]PF6
as solvent, the attack at the C-1 aromatic is the main path of the
reaction (94%). These results suggest that ionic liquids can be
considered to be designer solvents because by an appropriate
choice of the anion it is possible to control the selectivity of this
reaction.
Good correlations of rate and selectivity with solvent acceptor
capacity to form hydrogen bonds (b) are observed for these
reactions. In both cases the anion is the most important factor,
while the effect of the cation is relatively modest.
4.4 Selectivity
The selectivity of the amine attack at the phosphoryl group
( f pN), that is a thermodynamic property, is defined by the
4. Experimental section
4.1 Materials
kNp
À
Á
kinetic parameters summarized in Table 2: fNp
¼
kpN þ kANr
All ionic liquids, piperidine and O,O-diethyl chlorophosphate
were purchased from Aldrich. All ionic liquids were dried
before use in a vacuum oven at 70 1C for at least 2 h, and
stored in a dryer under nitrogen and over calcium chloride.
Water contents determined by Karl–Fischer titration were
or by using the amounts of obtained products summarized in
À
Á
%SN2ðPÞ
Table S3 (ESI†) fNp
¼
:
%SN2ðPÞ þ %SNðArÞ
o200 ppm. Substrate
1 was prepared as described in
Acknowledgements
literature.31
This work was supported by project ICM-P10-003-F CILIS,
´
granted by ‘‘Fondo de Innovacion para la Competitividad’’ from
4.2 Kinetic measurements
´
Ministerio de Economıa, Fomento y Turismo, Chile, and FON-
These were performed spectrophotometrically (diode array) in
the range of 300–500 nm, by following the appearance of
products after at least four half- lives, by means of a Hewlett-
Packard 8453 instrument. The reactions were carried out in
water, acetonitrile, dimethyl sulfoxide and in twelve different
ILs. At least a 10-fold excess of total amine over the substrate
was employed. In a typical spectrophotometric measurement, a
quartz cuvette (light-path 0.2 cm) containing 500 mL of ionic
liquid was thermostated at 25 1C during 10 minutes. Then, a
solution of 1 (50 mL, 2 ꢃ 10ꢁ3 M in ACN) and concentrated
amine (10 mL) were added. The spectra were recorded at
different reaction times and pseudo-first-order rate coefficients
DECYT, grant 1130065.
References
1 (a) M. A. Ab Rani, A. Brandt, L. Crowhurst, A. Dolan,
N. H. Hassan, J. P. Hallett, P. A. Hunt, M. Lui, H. Niedermeyer,
J. M. Perez-Arlandis, M. Schrems, T. Q. To, T. Welton and
R. Wilding, Phys. Chem. Chem. Phys., 2011, 13, 21653;
(b) T. Welton, Green Chem., 2011, 13, 225; (c) J. P. Hallett and
T. Welton, Chem. Rev., 2011, 111, 3508; (d) E. J. Amigues,
C. Hardacre, G. Keane, M. E. Migaud, S. E. Norman and
New J. Chem.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015

View Article Online
NJC
Paper
W. R. Pitner, Green Chem., 2009, 11, 1391; (e) C. Hardacre, 14 Y. R. Jorapur, C. H. Lee and D. Y. Chi, Org. Lett., 2005, 7, 1231.
H. Huang, S. L. James, M. E. Migaud, S. E. Norman and 15 F. D’anna, V. Frenna, R. Noto, V. Pace and D. Spinelli, J. Org.
W. R. Pitner, Chem. Commun., 2011, 47, 5846; ( f ) M. P. Singh,
R. K. Singh and S. Chandra, Prog. Mater. Sci., 2014, 64, 73.
2 (a) M. J. Earle, U. Hakala, C. Hardacre, J. Karkkainen,
Chem., 2006, 71, 9637.
16 D. W. Kim, C. E. Song and D. Y. Chi, J. Am. Chem. Soc., 2002,
124, 10278.
B. J. McAuley, D. W. Rooney, K. R. Seddon, J. M. Thompson 17 D. W. Kim, D. J. Hong, J. W. Seo, H. S. Kim, H. K. Kim,
and K. Wahala, Chem. Commun., 2005, 903; (b) M. J. Earle, C. E. Song and D. Y. Chi, J. Org. Chem., 2004, 69, 3186.
U. Hakala, B. J. McAuley, M. Nieuwenhuyzen, A. Ramani and 18 (a) F. D’Anna, V. Frenna, V. Pace and R. Noto, Tetrahedron, 2006,
K. R. Seddon, Chem. Commun., 2004, 1368.
3 (a) S. Doherty, P. Goodrich, C. Hardacre, H. K. Luo,
62, 1690; (b) L. Crowhurst, N. L. Lancaster, J. M. P. Arlandis and
T. Welton, J. Am. Chem. Soc., 2004, 126, 11549.
D. W. Rooney, K. R. Seddon and P. Styring, Green Chem., 19 (a) A. J. Kirby, J. R. Mora and F. Nome, Biochim. Biophys.
2004, 6, 63; (b) J. Dupont, R. F. de Souza and P. A. Z. Suarez,
Chem. Rev., 2002, 102, 3667.
4 S. A. Forsyth, H. Q. N. Gunaratne, C. Hardacre, A. McKeown,
D. W. Rooney and K. R. Seddon, J. Mol. Catal. A: Chem.,
2005, 231, 61.
5 R. A. Sheldon, R. M. Lau, M. J. Sorgedrager, F. van Rantwijk
and K. R. Seddon, Green Chem., 2002, 4, 147.
6 A. J. Carmichael, D. M. Haddleton, S. A. F. Bon and
K. R. Seddon, Chem. Commun., 2000, 1237.
7 K. R. Seddon and A. Stark, Green Chem., 2002, 4, 119.
8 P. J. Dyson, D. J. Ellis, D. G. Parker and T. Welton, Chem.
Commun., 1999, 25.
Acta, Proteins Proteomics, 2013, 1834, 454; (b) J. R. Mora,
A. J. Kirby and F. Nome, J. Org. Chem., 2012, 77, 7061;
(c) I. Onyido, K. Swierczek, J. Purcell and A. C. Hengge, J. Am.
Chem. Soc., 2005, 127, 7703; (d) E. A. Castro, D. Ugarte,
M. F. Rojas, P. Pavez and J. G. Santos, Int. J. Chem. Kinet.,
2011, 43, 708.
20 (a) E. S. Orth, P. L. F. da Silva, R. S. Mello, C. A. Bunton,
H. M. S. Milagre, M. N. Eberlin, H. D. Fiedler and F. Nome,
J. Org. Chem., 2009, 74, 5011; (b) J. B. Domingos, E. Longhinotti,
T. A. S. Brandao, L. S. Santos, M. N. Eberlin, C. A. Bunton and
F. Nome, J. Org. Chem., 2004, 69, 7898; (c) M. Medeiros,
E. S. Orth, A. M. Manfredi, P. Pavez, G. A. Micke, A. J. Kirby
and F. Nome, J. Org. Chem., 2012, 77, 10907.
9 (a) E. E. L. Tanner, R. R. Hawker, H. M. Yau, A. K. Croft and
J. B. Harper, Org. Biomol. Chem., 2013, 11, 7516; (b) H. M. Yau, 21 N. M. Rougier, R. V. Vico, R. H. de Rossi and E. I. Bujan,
S. T. Keaveney, B. J. Butler, E. E. L. Tanner, M. S. Guerry, J. Org. Chem., 2010, 75, 3427.
S. R. D. George, M. H. Dunn, A. K. Croft and J. B. Harper, Pure 22 P. Pavez, D. Millan, J. I. Morales, E. A. Castro, C. Lopez and
Appl. Chem., 2013, 85, 1979. J. G. Santos, J. Org. Chem., 2013, 78, 9670.
10 (a) R. Bini, C. Chiappe, C. S. Pomelli and B. Parisi, J. Org. 23 F. D’Anna, V. Frenna, R. Noto, V. Pace and D. Spinelli, J. Org.
Chem., 2009, 74, 8522; (b) C. Chiappe, C. S. Pomelli and Chem., 2005, 70, 2828.
S. Rajamani, J. Phys. Chem. B, 2011, 115, 9653; (c) F. D’anna, 24 R. Aguayo, F. Arias, A. Canete, C. Zuniga, E. A. Castro,
S. La Marca, P. Lo Meo and R. Noto, Chem. – Eur. J., 2009, P. Pavez and J. G. Santos, Int. J. Chem. Kinet., 2013, 45, 202.
15, 7896; (d) T. P. Wells, J. P. Hallett, C. K. Williams and 25 W. S. MacGregor, Ann. N. Y. Acad. Sci., 1967, 141, 3.
T. Welton, J. Org. Chem., 2008, 73, 5585.
26 (a) F. D’Anna, S. Marullo, P. Vitale and R. Noto, Chem-
PhysChem, 2012, 13, 1877; (b) D. Millan, M. Rojas, P. Pavez,
M. Isaacs, C. Diaz and J. G. Santos, New J. Chem., 2013,
37, 3281.
11 (a) J. Dupont, Acc. Chem. Res., 2011, 44, 1223; (b) J. Dupont and
P. Suarez, Phys. Chem. Chem. Phys., 2006, 8, 2441; (c) M. Zanatta,
A. Girard, N. Simon, G. Ebeling, H. Stassen, P. Livotto, F. Santos
and J. Dupont, Angew. Chem., 2014, 53, 12817; (d) K. Shimizu, 27 (a) E. E. L. Tanner, H. M. Yau, R. R. Hawker, A. K. Croft and
C. E. S. Bernardes and J. N. C. Lopes, Pure Appl. Chem., 2014,
86, 119; (e) V. Gangamallaiah and G. B. Dutt, J. Phys. Chem. B,
2013, 117, 9973; ( f ) P. Morgado, K. Shimizu, J. M. S. Esperanca,
J. B. Harper, Org. Biomol. Chem., 2013, 11, 6170; (b) S. T.
Keaveney, K. S. S. McHale, R. S. Haines and J. B. Harper,
Org. Biomol. Chem., 2014, 12, 7092.
P. M. Reis, L. P. N. Rebelo, J. N. C. Lopes and E. J. M. Filipe, 28 (a) M. H. Abraham, Chem. Soc. Rev., 1993, 22, 73; (b) J. L.
J. Phys. Chem. Lett., 2013, 4, 2758.
12 M. Freemantle, Introduction to Ionic Liquids, The Royal
Society of Chemistry, Cambridge, UK, 2010, ch. 5, p. 41.
Anderson, J. Ding, T. Welton and D. W. Armstrong, J. Am.
Chem. Soc., 2002, 124, 14247.
29 J. Dupont, J. Braz. Chem. Soc., 2004, 15, 341.
13 M. J. Earle, S. P. Katdare and K. R. Seddon, Org. Lett., 2004, 30 B. Butler and J. Harper, New J. Chem., 2015, 39, 213.
6, 707. 31 S. A. Ba-Saif and A. Williams, J. Org. Chem., 1988, 53, 2204.
This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
New J. Chem.