Bronsted acidic ionic liquids of aza-crown ether complex cations: Preparation and applications in organic reactions

Article abstract of DOI:10.1039/c4ra03061c

A series of novel Bronsted acidic ionic liquids composed of an aza-crown ether chelated potassium cation and various anions, were designed, synthesized and characterised by FTIR, NMR and mass spectrometry, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. These new Bronsted acidic ionic liquids of aza-crown ether complex cations (aCBAILs) were applied as catalysts to the Biginelli reaction, Mannich reaction and synthesis of bis-(4-hydroxycoumarin-3-yl)methanes. These organic reactions were achieved in good yields under mild reaction conditions. Moreover, these new IL catalysts can be recycled several times. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra03061c

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Brønsted acidic ionic liquids of aza-crown ether
complex cations: preparation and applications in
organic reactions†
Cite this: RSC Adv., 2014, 4, 34325
*
Chen Cheng and Huanwang Jing
A series of novel Brønsted acidic ionic liquids composed of an aza-crown ether chelated potassium cation
and various anions, were designed, synthesized and characterised by FTIR, NMR and mass spectrometry,
thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. These new Brønsted
acidic ionic liquids of aza-crown ether complex cations (aCBAILs) were applied as catalysts to the
Biginelli reaction, Mannich reaction and synthesis of bis-(4-hydroxycoumarin-3-yl)methanes. These
organic reactions were achieved in good yields under mild reaction conditions. Moreover, these new IL
catalysts can be recycled several times.
Received 5th April 2014
Accepted 24th July 2014
DOI: 10.1039/c4ra03061c
www.rsc.org/advances
acid was successfully introduced into the aza-crown ether to
produce the desired Brønsted acidic ionic liquids of aza-crown
Introduction
ether complex cations (Scheme 1) that can be applied to several
organic reactions.
In recent decades, ionic liquids (ILs) have attracted great
interest, and been applied successfully to a variety of
organic reactions, due to their environmentally benign
features, such as lower vapour pressure, remarkable solu-
bility, recyclability, and excellent thermal and chemical
stability.1–4 Currently, many task-specic ionic liquids were
designed and fabricated according to the requests of different
reactions.5–11 Since Cole rst reported a new approach for
esterication using acidic Brønsted functionalized ILs as
solvent and catalyst,12 the introduction of acidic Brønsted
functional groups, especially –SO3H, into cations of the ILs,
has obviously enhanced the acidity and water solubility of the
ILs.13,14 This also gives great promise for using ILs as green
catalysts with good catalytic activities in many organic
reactions.15
Scheme 1 Structure of Brønsted acidic ionic liquids of aza-crown
ether complex cations.
Although many ionic liquids have been developed, their
cations are mostly limited to quaternary ammonium, N,N0-dia-
lkylimidazolium and N-alkylpyridinium cations etc. Differing
from these traditional ionic liquids, we discovered a novel type
of ionic liquid containing crown ether complex cations and
various anions, which could greatly extend the IL family.16
These new ILs were used in various organic reactions, such as
the Michael addition, Henry reaction, Heck reaction, oxidation
reaction of aromatic alcohols, and asymmetric addition of CO2
and epoxides.16,17 To functionalize these ILs, an alkanesulfonic
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and
Chemical Engineering, Lanzhou University, 222 South Tianshui Road, Lanzhou,
Gansu730000, P.R. China. E-mail: hwjing@lzu.edu.cn; Fax: +86 0931-8912582; Tel:
+86 0931-8912585
† Electronic
supplementary
information
ESI
available.
See
DOI:
Scheme 2 Synthetic route to Brønsted acidic ionic liquids of aza-
10.1039/c4ra03061c
crown ether complex cations.
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Table 1 The properties of Brønsted acidic ionic liquids of aza-crown
ether complex cations
In this paper, 1-butyl-1-aza-[18-C-6KSO3H]X2 compounds
were utilized successfully in the Biginelli and Mannich reac-
tions. Moreover, biscoumarins32,33 were also synthesized using
these ILs as catalysts.
a
Entry
Catalyst/anion
m.p./ꢀC
Td /ꢀC
1
2
3
4
5
1/Br
2/BF4
3/PF6
4/HSO4
5/CF3CO2
2
12
ꢁ4
ꢁ1
8
207
260
261
201
197
Results and discussion
Understanding the weak electrostatic interactions among the
cations and anions decrease the melting point of the ILs and
enhance the basicity and nucleophilicity of the anions,16 we
attempted to develop a new type of Brønsted acidic ionic liquids
via a protocol of functionalization of aza-crown ether cation.
Fortunately, ve ionic liquids of aza-crown ether complex
cations functionalized by alkanesulfonic acid were successfully
synthesized (Scheme 2). Firstly, a zwitterionic-type aza-crown
ether was prepared by using a direct sulfonation reaction of
butyl-aza-crown ether and 1,3-propanesulfone in dichloro-
ethane; then equimolar of the functionalized aza-crown ether,
potassium salt and relevant acid were mixed together in water at
room temperature leading to the pure Brønsted acidic aza-
crown ether complex cation ionic liquid in quantity.
a
Decomposition temperatures (Td) were determined by TG-DTA heating
at 10 ꢀC minꢁ1 under nitrogen.
The Biginelli reaction is a useful multicomponent reaction
for the synthesis of dihydropyrimidinones (DHPMs) that have
displayed good bioactivities and pharmaceutical activities.18
Many catalysts for the Biginelli reaction have been docu-
mented19–21 including some functionalized ionic liquids.22,23
Herein, 1-butyl-1-aza-[18-C-6KSO3H][BF4]2 was used in the
Biginelli reaction as an efficient IL catalyst, and recycled at least
ve times without evident loss of catalytic activity.
The Mannich reaction is a widely applicable approach to
b-amino carbonyl compounds catalysed by Lewis acids,24,25
Brønsted acids,26,27 heteropolyacids,28 and organic acids etc.29,30
The products are a type of synthetic intermediate in the manu-
facture of various pharmaceuticals and natural products.31
All of the aCBAILs made up of dication and dianion are very
viscous, yellow and colloidal complexes. They are very soluble in
water, readily soluble in polar solvents such as methanol,
ethanol, and acetone, insoluble in nonpolar solvents such as
Table 2 Biginelli reaction catalysed by different catalystsa
Entry
Catalyst
Amount (mol %)
Yieldb (%)
1
2
3
4
5
6
7
8
None
0
7
7
7
7
7
5
6
8
10
7
7
7
7
7
7
Trace
46
92
87
Trace
53
71
86
90
88
1/1-butyl-1-aza-[18-C-6KSO3H][Br]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
3/1-butyl-1-aza-[18-C-6KSO3H][PF6]2
4/1-butyl-1-aza-[18-C-6KSO3H][HSO4]2
5/1-butyl-1-aza-[18-C-6KSO3H][TFA]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
1-butyl-1-aza-[18-C-6SO3H][BF4]c
NaHSO4
KHSO4
NH4HSO4
CH3SO3H
p-TsOH
[Hbim]BF4
GlyNO3
[Bmim]MeSO4
9
10
11
12
13
14
15
16
17
18
19
86
Trace
Trace
Trace
58
75
60
40
1
97d
92e
90f
a
b
c
Reaction conditions: aldehyde 1.0 mmol, ethyl acetoacetate 3.0 mmol, urea 1.5 mmol, ethanol 2 mL, reux, 5 hours. Isolated yield. The IL
d
catalyst without adding KBF4. See ref. 39. e See ref. 42. f See ref. 44.
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Table 3 Recycling of 1-butyl-1-aza-[18-C-6KSO3H][BF4]2 in Biginelli
alkanes, ethers and aromatic hydrocarbons. The new ioꢀnic
liquids show melting points lower than 25 degree (ꢁ4–12 C)
and good thermodynamic stabilities up to 197–261 ꢀC measured
by TG-DTA (Table 1).
reactiona
Entry
Yieldb (%)
Acidic Brønsted ionic liquids are of great value because they
possess simultaneously the advantages of liquid acids and solid
acids, such as uniform acid site, stability in water, easy sepa-
ration and reusability.34 Additionally, they have also excellent
catalytic activity owing to their plentiful hydrogen bonds with
substrates, which can accelerate the product formation by
lowering the activation barrier.35 Similarly, our new Brønsted
acidic ionic liquids of aza-crown ether complex cations can
provide both hydrogen bond donors and hydrogen bond
acceptors. The alkanesulfonic acid attached to aza-crown ether
complex cation directly activated aldehyde carbonyl via
hydrogen bond to undergo nucleophilic addition.36,37 So our
new ionic liquids catalysts can increase effectively the electro-
philicity of the carbonyl that is easy to perform the nucleophilic
addition.
1
2
3
4
5
92
90
90
89
85
a
Reaction conditions: aldehyde 1.0 mmol, ethyl acetoacetate 3.0 mmol,
urea 1.5 mmol, catalyst 2 0.07 mmol, ethanol 2 mL, reux, 5 hours.
b
Isolated yield.
thiourea (Table 4, entries 14–16) can also be used to yield corre-
sponding products in the presence of new IL.
Mannich reaction
Mannich reaction is one of the most important carbon–carbon
bond formations in organic synthesis45 and can be realized in
ionic liquids.46–48 With these new aCBAILs in hand, we try to
used it as catalyst in Mannich reaction of benzaldehyde, aniline
and acetophenone. Fortunately, this three-component reaction
can be performed at room temperature (Table 5). 1-Butyl-1-aza-
[18-C-6KSO3H][TFA]2 demonstrated good catalytic activity in
ethanol (83%) (Table 5, entry 5). Furthermore, various
substituted benzaldehydes and anilines were reacted with ace-
tophenone to generate the corresponding products (Table 6).
Biginelli reaction
The synthesis of 3,4-dihydropyrimidinones was rstly reported
by Biginelli in 1893, involving a one-pot condensation reaction
under strongly acidic conditions.38 Since then, several modi-
cations have been developed for the classical Biginelli
approach.39–44 Searching for a more efficient and recyclable IL
catalyst, the Biginelli reaction of benzaldehyde, ethyl acetoace-
tate, and urea in ethanol was investigated in the presence of a
aza-crown ether cation IL. Aer screening various aCBAILs, they
can promote this reaction except 1-butyl-1-aza-[18-C-6KSO3H]
[HSO4]2 (Table 2, entries 2–6) It can be seen that the reaction
was difficult to take place in the absence of IL catalyst (Table 2,
entry 1). The best IL catalyst of 1-butyl-1-aza-[18-C-6KSO3H]
[BF4]2 (2) gave the highest yield (92%) of DHPM (Table 2, entry
3). The concentration of catalyst 2 also affected the yield of
product (Table 2, entries 7–10). Compared with the most
traditional ILs that must initiated this reaction with large
amount of catalyst under extra ultrasound (Table 2, entry 17) or
Table 4 Biginelli reaction of various substrates catalysed by 1-aza-
[18-C-6KSO3H][BF4]2
a
microwave (Table 2, entry 18) assistance, our new aCBAIL Entry
R1
R2
X
Yieldb (%)
catalysts have signicant advantages of less amount of catalyst
1
2-CH3OC6H4
3-CH3OC6H4
4-CH3OC6H4
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
4-ClC6H4
4-HOC6H4
4-CH3C6H4
2,5-(CH3O)2C6H3
Ph
4-CH3OC6H4
4-NO2C6H4
Ph
4-CH3OC6H4
4-NO2C6H4
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
OCH2CH3
CH3
CH3
CH3
OCH2CH3
OCH2CH3
OCH2CH3
O
O
O
O
O
O
O
O
O
O
O
O
O
S
37
79
82
48
77
84
86
71
83
74
80
81
77
56
51
47
usage under very mild reaction conditions.
2
Compared with traditional acid catalysts, easy recycling is an
3
4
5
6
7
8
9
10
11
12
13
14
15
16
attractive property of this type of acidic ionic liquids. Conse-
quently, we investigated the recovery and reuse of best catalyst
of 1-butyl-1-aza-[18-C-6KSO3H][BF4]2 in the multicomponent
reaction of benzaldehyde, ethyl acetoacetate, and urea. As
shown in Table 3, the catalyst can be reused at least four times
without signicant loss of activity.
To extend the scope of this reaction, a variety of substituted
aldehydes were investigated under the optimal conditions. The
results are listed in Table 4. It can be seen that the aromatic
aldehydes with both the electron-withdrawing and the electron-
donating groups can generate the target products readily (Table 4,
entries 1–10). Aromatic aldehydes with ortho-substituted
groups led to lower reaction yield due to the steric effect (Table 4,
entry 1, 4). The acetylacetone (Table 4, entry 11–13) and
S
S
a
Reaction conditions: aCBAIL catalyst 2 0.07 mmol, aldehyde 1.0 mmol,
dicarbonyl compound 3.0 mmol, urea or thiourea 1.5 mmol, ethanol 2
mL, reux, 5 hours. b Isolate yield.
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Table 5 Mannich reaction catalysed by different catalystsa
Entry
Catalyst
Amount (mol %)
Yieldb (%)
1
2
3
4
5
7
8
9
1/1-butyl-1-aza-[18-C-6KSO3H][Br]2
2/1-butyl-1-aza-[18-C-6KSO3H][BF4]2
3/1-butyl-1-aza-[18-C-6KSO3H][PF6]2
4/1-butyl-1-aza-[18-C-6KSO3H][HSO4]2
5/1-butyl-1-aza-[18-C-6KSO3H][TFA]2
1-butyl-1-aza-[18-C-6SO3H][TFA]c
KHSO4
CH3SO3H
p-TsOH
[Hmim]TFA
[DDPA]HSO4
10
10
10
10
10
10
10
10
10
16
10
57
27
48
trace
83
82
Trace
31
10
11
12
77
85d
87e
a
b
Reaction conditions: benzaldehyde 1.0 mmol, aniline 1.0 mmol, acetophenone 1.0 mmol, ethanol 2 mL, room temperature, 5 hours. Isolated
yield. c The IL catalyst without adding CF3COOK. d See ref. 46. e See ref. 48.
aluminum trichloride etc. This reaction was carried out through
the nucleophilic addition of 4-hydroxycoumarin to benzaldehyde
followed by dehydration to form bis-(4-hydroxycoumarin-3-yl)-
methanes in the presence of aCBAIL. 1-Butyl-1-aza-[18-
C-6KSO3H][TFA]2 showed the best activity to produce the target
product up to 98% yield (Table 7, entry 5). It is clear to see that
the mixed solvent of water-alcohol (1 : 1, v/v) exhibited more
positive effect than water or alcohol (Table 7, entry 5 vs. 6,7).
Under the optimized reaction condition, various substrates
Synthesis of bis-(4-hydroxycoumarin-3-yl)methanes
In the literatures,49–51 the synthesis of biscoumarin derivatives
was commonly approached via a condensation reaction of
coumarin and aldehyde catalysed by acidic catalysts, such as
sulfuric acid, triuoroacetic acid, phosphorus pentoxide, and
Table 6 Mannich reaction of various substrates catalysed by 1-aza-
a
[18-C-6KSO3H][TFA]2
Table 7 Synthesis of bis-(4-hydroxycoumarin-3-yl)methanes cata-
a
lysed by 1-aza-[18-C-6KSO3H][TFA]2
Entry
R1
R2
Yieldb (%)
Entry Cat.
R
Yieldb (%) Entry Cat.
R
Yield (%)
94
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
H
4-Cl
4-Cl
4-CH3
4-CH3
83
64
71
81
80
65
77
84
82
87
86
4-NO2
4-OH
4-OCH3
4-CH3
3-NO2
3-OCH3
H
4-OCH3
H
4-OCH3
1
2
3
4
5
6
7
8
1
2
3
4
5
5
5
5
Ph 72
Ph 86
Ph 89
Ph 82
Ph 98
Ph 72c
Ph 83d
Ph 95e
9
10
11
12
13
14
15
16
17
5
5
5
5
5
5
5
5
5
3-NO2C6H5
3-CH3OC6H5 91
4-CH3OC6H5 96
4-ClC6H5
87
91
97
92
4-CH3C6H5
4-OHC6H5
4-NO2C6H5
Ph-CH]CH 94
2,4-NO2C6H4 77
9
10
11
a
Reaction conditions: benzaldehyde 1.0 mmol, 4-hydroxycoumarin 2.0
a
Reaction conditions: aldehyde 1.0 mmol, aniline 1.0 mmol, ketone 1.0 mmol, aCBAIL catalyst 5 0.05 mmol, EtOH 1 mL and H2O 1 mL, reux,
mmol, aCBAIL catalyst 5 0.10 mmol, ethanol 2 mL, room temperature, 5 30 min. b Isolate yield. c Ethanol 2 mL as solvent. d Deionized water 2
hours. b Isolated yield.
mL as solvent. e See ref. 43.
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(Table 7, entry 9–17) possessing the electron-donating group or containing zwitterion product (9.5 mmol) that was stirred for 24
electron-withdrawing group can give the target products in h at room temperature. The desired aCBAIL was obtained as a
excellent yields.
yellow viscous product aer removing the water and stored in a
desiccator (95%).
Experimental section
Materials and methods
General procedure for the Biginelli reaction
A mixture of aldehyde (1 mmol), ethyl acetoacetate (3 mmol),
urea (1.5 mmol) and aCBAIL catalyst (0.07 mmol) was heated to
reux in ethanol (2 mL) for a proper time. Aer completion of
the reaction monitored by TLC, the mixture was poured into ice
water (10 mL). The resulting solid precipitate was ltered,
washed with cooled ethanol, dried in vacuo, and characterised
by 1H NMR spectra that were consistent with the literature
reports.39
All reagents were obtained from commercial resources and used
without further purication. 1H and 13C NMR spectra were
recorded respectively on Varian 300 spectrometer and Varian
400 spectrometer using TMS as the internal standard. Multi-
plicity is indicated by the following: s (singlet); d (doublet);
t (triplet); q (quartet); m (multiplet); br (broad). Thermogravi-
metric differential thermal analysis (TG-DTA) was carried out on
a STA 449-C (Netzsch, Germany). Elemental analyses were
carried out on Carioel elemental analyzer. Infrared spectra were
collected on a Nicolet NEXUS 670 FT-IR spectrometer using a
KBr pallet.
To reuse the aCBAIL, the above ltrate was extracted with ether
(3 ꢂ 10 mL) to remove the organic impurities. The treated water
solution was then evaporated under vacuum to reproduce IL.
General procedure for the Mannich reaction
Synthesis of 1-butyl-1-aza-18-crown-6
A round-bottom ask charged with aCBAIL (0.1 mmol) in 2 mL
of ethanol was added aldehyde (1 mmol), aniline (1 mmol) and
ketone (1 mmol). The mixture was stirred for a proper time at
room temperature to precipitate a crude product that was
collected by ltration and recrystallized from ethanol–acetone
(1 : 1, v/v) to afford pure Mannich base.
NaH (40 mmol, 80%) and dried THF (100 mL) were added to a
500 mL round-bottom ask and cooled down to around ꢁ5–0 ꢀC
in an ice-salt bath. N-butyldiethanolamine (10 mmol) were
dissolved in 100 mL dried THF and added dropwise to the ask.
The ice-bath was removed and the mixture was heated to reux
ꢀ
for 2 h. The ask was cooled again to 0 C in the ice-bath and
added dropwise the THF 100 mL dissolved tetraethylene glycol
ditosylate (10 mmol). Then the mixture was stirred for 48 h
under reuxing. Aer completion of this reaction, it was
quenched with 100 mL water. Most of THF was removed by
rotary evaporator and the mixture was extracted with dichloro-
methane (3 ꢂ 30 mL) subsequently. The combined organic layer
was washed with water (3 ꢂ 50 mL) and dried by anhydrous
MgSO4. Aer evaporating the volatiles under vacuum, a yellow
oily product was collected in 65% yield (Scheme 3).52–54
General procedure for synthesis of bis-(4-hydroxycoumarin-3-
yl)methanes
A mixture of benzaldehyde (1 mmol), 4-hydroxycoumarin (2
mmol) and aCBAIL (0.05 mmol) in EtOH (1 mL) and H2O (1 mL)
was stirred under reux condition for an appropriate time. Aer
completion of the reaction monitored by TLC, the mixture was
cooled down to room temperature. The solid product was
collected by ltration, washed with water and cool ethanol.
Characterisation of catalysts
Preparation of Brønsted acidic ionic liquids of aza-crown
The NMR, IR and mass spectra, and the elemental analysis
results of aza-crown ether complex cation ionic liquids are
described as follows:
ether complex cations
aza-crown ether (11 mmol) and 1,3-propanesultone (10 mmol)
were dissolved in 1,2-dichloroethane (15 mL) and allowed to stir
1-Butyl-1-aza-[18-C-6KSO3H][Br]2. 1H NMR (300 MHz, D2O)
d ¼ 0.93 (t, J ¼ 6.9 Hz, 3H), 1.36 (m, 2H), 1.69 (m, 2H), 2.16 (m,
2H), 2.93 (m, 2H), 3.39–3.68 (m, 24H), 3.90 (m, 4H) ppm; 13C
NMR (100 MHz, D2O) d ¼ 12.53, 17.24, 18.61, 22.78, 46.84,
57.75, 58.07, 58.92, 59.64, 63.14, 63.38, 68.21, 68.69, 69.08,
69.08, 69.11, 69.12, 69.38, 69.89 ppm. IR (cmꢁ1) 3426.3 (m),
2911.4 (m), 2876.5 (m), 1718.4 (w), 1650.8 (w), 1469.3 (m), 1353.4
(m), 1249.8 (s), 1115.9 (vs.), 1037.0 (s), 950.6 (m), 840.6 (w), 732.6
(w), 602.3 (m), 522.7 (m). Elemental analysis, calcd for C19H40-
Br2KNO8S (%): C 35.57, H 6.28, N 2.18; found: C 35.21, H 6.24, N
1.83.
ꢀ
under Ar at 40 C for 4 h. Aer completion of the reaction, the
solvent was evaporated under reduced pressure, the residue was
washed with hexane (3 ꢂ 10 mL) and dissolved in deionized
water (20 mL). The excess of aza-crown ether can be extracted
with CH2Cl2 (3 ꢂ 20 mL). Aer removing the water, a yellow
viscous zwitterion product e was obtained in 95% yield. Then
the equimolar potassium salt (9.5 mmol) and corresponding
acid (9.5 mmol) were added to the water solution (20 mL)
1-Butyl-1-aza-[18-C-6KSO3H][BF4]2. 1H NMR (300 MHz, D2O)
d ¼ 0.95 (t, J ¼ 7.5 Hz, 3H), 1.38 (m, 2H), 1.70 (m, 2H), 2.17 (m,
2H), 2.95 (m, 2H), 3.40–3.71 (m, 24H), 3.92 (m, 4H) ppm; 13C
NMR (100 MHz, D2O) d ¼ 12.58, 17.35, 18.81, 22.92, 46.95,
57.69, 59.03, 59.21, 59.66, 63.38, 63.57, 68.95, 69.22, 69.28,
Scheme 3 Synthesis of 1-butyl-1-aza-18-crown-6.
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69.35, 69.42, 69.48, 69.62, 69.65 ppm. IR (cmꢁ1) 3432.2 (m),
2924.3 (m), 2878.0 (m), 1718.7 (w), 1635.1 (w), 1465.2 (m), 1355.0
(m), 1295.5 (m), 1216.6 (m), 1119.0 (vs.), 1040.0 (s), 947.8 (m),
839.1 (w), 733.4 (w), 601.7 (w), 526.4 (m). Elemental analysis
calcd for C19H40B2F8KNO8S (%): C 34.82, H 6.15, N 2.14; found:
C 34.52, H 6.38, N 2.01.
Acknowledgements
This work was nancially supported by the National Natural
Science Foundation of China (NSFC 21173106).
1-Butyl-1-aza-[18-C-6KSO3H][PF6]2. 1H NMR (300 MHz, D2O)
d ¼ 0.89 (t, J ¼ 7.2 Hz, 3H), 1.31 (m, 2H), 1.64 (m, 2H), 2.11 (m,
2H), 2.87 (m, 2H), 3.33–3.64 (m, 24H), 3.85 (m, 4H) ppm; 13C
NMR (100 MHz, D2O) d ¼ 12.63, 17.47, 18.86, 23.03, 47.10,
58.27, 59.07, 59.25, 59.68, 63.61, 63.70, 69.28, 69.32, 69.36,
69.38, 69.45, 69.48, 69.54, 69.68 ppm. IR (cmꢁ1) 3433.4 (m),
2921.7 (m), 2881.4 (m), 1717.3 (w), 1637.4 (w), 1469.2 (w), 1353.9
(w), 1248.2 (m), 1219.1 (m), 1114.2 (vs.), 1035.4 (s), 845.3 (m),
743.0 (m), 604.6 (w), 556.3 (w), 525.3 (w), 485.2 (m). Elemental
analysis calcd for C19H40F12KNO8P2S (%): C 29.57, H 5.23, N
1.82; found: C 29.32, H 5.41, N 1.57.
Notes and references
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D2O) d ¼ 0.92 (t, J ¼ 7.2 Hz, 3H), 1.35 (m, 2H), 1.67 (m, 2H), 2.15
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(m, 2H), 2.92 (m, 2H), 3.38–3.69 (m, 24H), 3.92 (m, 4H) ppm; 13
C
NMR (100 MHz, D2O) d ¼ 12.58, 17.29, 18.67, 22.85, 46.92,
57.51, 58.06, 59.06, 59.78, 63.22, 63.42, 68.76, 69.10, 69.13,
69.16, 69.24, 69.26, 69.39, 69.46 ppm. IR (cmꢁ1) 3438.8 (m),
2920.1 (m), 2877.5 (m), 1722.3 (w), 1637.8 (w), 1468.1 (m), 1352.4
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