Synthesis of new chiral ionic liquids from α-hydroxycarboxylic acids

Article abstract of DOI:10.1016/j.tetasy.2011.01.024

New functionalized optically active N-methylimidazolium ionic liquids with an asymmetric center at the β-position to the imdazole ring were synthesized as bromide salts from optically active α-hydroxycarboxylic acids. The bromide anions were exchanged by carboxylate anions with Amberlite IRA 400 ionic exchange resin.

Full text of DOI:10.1016/j.tetasy.2011.01.024

Tetrahedron: Asymmetry 22 (2011) 294–299
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Synthesis of new chiral ionic liquids from a-hydroxycarboxylic acids
⇑
Marcin Poterała, Jan Plenkiewicz
Chemistry Faculty, Warsaw University of Technology, ul. Noakowskiego 3, 00-664 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
New functionalized optically active N-methylimidazolium ionic liquids with an asymmetric center at the
b-position to the imdazole ring were synthesized as bromide salts from optically active a-hydroxycarb-
oxylic acids. The bromide anions were exchanged by carboxylate anions with Amberlite IRA 400 ionic
exchange resin.
Received 14 December 2010
Accepted 26 January 2011
Available online 1 March 2011
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
the b-position to the positively charged imidazole ring. For that
reason we needed several optically active
a-hydroxy carboxylic
Ionic liquids are organic or inorganic salts with melting points
below 100 °C.1 They possess special and unique properties, such
as high polarity, very low vapor pressure, high thermal and chem-
ical stability, high ionic conductivity, and good transparence in
ultraviolet and visible lights. These properties make them useful
agents of various applicability as mild, non-aggressive solvents of
choice in synthetic chemistry, electrochemistry,2 biotransforma-
tion,3 spectrometry,4 etc. It was found also that chiral ionic liquids
can be used as chiral solvents or catalysts5 in asymmetric synthesis
or as chiral differentiating solvents for spectroscopic investiga-
tions. These findings have greatly increased interest in ionic liquid
synthesis and investigation over the last decade. For example,
Sanzhong et al.6 obtained optically active ionic liquids based on
acids. One of the easiest and cost effective ways to produce enan-
tiomerically pure compounds is the use of natural substrates from
the so-called ‘chiral pool’. In the case of
mercially available natural -amino acids seemed to be the most
convenient substrates. Optically active ionic liquids based on nat-
ural -amino acids with the amino group attached to the stereo-
a-hydroxy acids, the com-
L
-a
L
-a
genic carbon have been described by several authors; a review
detailing their design, synthesis, properties, and applications has
recently been published.8 Herein,
a-hydroxycarboxylic acids pre-
pared from L-a-amino acids (Scheme 1) have been used instead
of amino acids. Their synthesis consists of diazotization of the cor-
responding amino acids with sodium nitrite in a 0.5 M sulfuric acid
solution.9 The procedure is very simple and seems to be general
L-proline and used them as catalysts in the asymmetric Michael
although the yields of a-hydroxy acids were sometimes unsatisfac-
addition of cyclohexanone to nitroolefins. The reactions proceeded
with high yields and good enantiomeric excesses. Vo-Thanh and
co-workers7 reported good stereochemical results for the Baylis–
Hillman reaction carried out in an ephedrinium-based chiral ionic
liquid. Although not all experiments give satisfactory results, they
allow the authors to obtain new important information and in-
crease our knowledge on the possible future applications of chiral
ionic liquids. Herein we report the results of our investigations on
synthesis of the optically active N-methylimidazolium ionic liquids
tory. For example, (S)-2-hydroxy-4-methylpentanoic acid 2c and
(2S,3S)-2-hydroxy-3-methylpentanoic acid 2d were obtained in
65–73% yields, while the yield of (S)-2-hydroxy-3-methylbutyric
acid 2b was only 25%, which is too far below the level acceptable
in a multistep synthesis. In order to overcome this problem, we
decided to use the procedure described by Miller and Kolasa.10
Thus, the diazotization of
acetic acid solution to yield the corresponding
acids, which without purification were treated with thionyl chlo-
ride and methanol. The resulting pure methyl esters of -hydroxy
L-
a-amino acids was carried out in an
a-acetoxycarboxylic
prepared from
a-hydroxycarboxylic acids, which are easily accessi-
a
ble from natural
L
-
a
-amino acids.
acids 3b–f were obtained in yields ranging from 86% to 95%. Sub-
sequent reduction of the esters with lithium aluminium hydride
in an anhydrous diethyl ether solution gave rise to the formation
of chiral diols 4a–f with satisfactory yields (45–86%). Their further
conversion into the corresponding O-acetyl-b-bromohydrins was
accomplished by treatment with a 45% hydrogen bromide solution
in glacial acetic acid. 1-Bromo-2-acetoxy-2-substituted ethanes
5a–d,f, which were obtained in high yields as the main products
of these reactions, were accompanied by small amounts of the 2-
bromo-1-acetoxy isomers formed in 6–8% yields. In the case of diol
4e, the 2-bromo-2-phenylethyl acetate was obtained as the sole
2. Results and discussion
The main goal of our investigation was the synthesis of several
optically active methylimidazolium ionic liquids with an
a
-hydro-
xy or
a-acetoxy group bonded to the asymmetric carbon atom at
⇑
Corresponding author. Tel.: +48 22 2347570; fax: +48 22 6282741.
E-mail address: plenki@ch.pw.edu.pl (J. Plenkiewicz).
0957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2011.01.024

M. Poterała, J. Plenkiewicz / Tetrahedron: Asymmetry 22 (2011) 294–299
295
NH2
OH
NaNO2, H2SO4
0 o
SOCl2, MeOH
O
O
R1
R1
-30 o
C
C
OH
OH
1c,d
2c,d,e*
NH2
OH
OAc
OH
HBr, CH3CO2H
LiAlH4, Et2O
SOCl2, MeOH
-30 oC
NaNO2, CH3CO2H
16 oC
O
O
O
OH
R1
R1
R1
R1
oC
0
oC
0
OH
OR2
OH
2b,f
4a-f
1b,f
3a**,b-f
N
N
OAc
R1
OH
N-Methylimidazole
CH3CN, 75-80 o
OAc
Br
HBr, H2O
RT
N
N
N
N
or
or
or
R1
Br
OAc
N
N
R1
R1
Br
R1
Br
R1
C
OAc
OH
Br
Br
7a-d,f
5e
6e
7e
5a-d,f
6a-d,f
a: R1= CH3-
R2= CH3- for 3b-f or CH3CH2- for 3a
comercial (S)-ethyl lactate was used
** comercial (S)-mandelic acid was used
b: R1= (CH3)2CH-
*
c: R1= (CH3)2CHCH2-
d: R1= (S)-CH3CH2CH(CH3)-
e: R1= C6H5-
f : R1= C6H5CH2-
Scheme 1. Synthesis of chiral ionic liquids from a-hydroxycarboxylic acids.
product and we did not observe the formation of the appropriate
secondary bromoalcohol ester. After purification, the acetylated
b-bromohydrins 5a–f were used for the alkylation of N-methylim-
idazole leading to the appropriate optically active N-methylimida-
zolium bromides 6a–f. The alkylation reactions were carried out in
anhydrous acetonitrile at 75–80 °C for three days. The salts ob-
tained 6a–f were then hydrolyzed at room temperature with dilute
hydrobromic acid to give the corresponding ionic liquids 7a–f in
high yields. Both compounds 6a–f and 7a–f were purified by treat-
ment with charcoal followed by repeated extractions of the unre-
acted substrates with diethyl ether until the salts started to
precipitate. In some cases, evaporation of the last trace amounts
of the substrates under reduced pressure (1 mmHg at 50–55 °C)
was required to initiate the precipitation. The final purifications
of the prepared bromides 6a–f and 7a–f consisted of recrystalliza-
tion from a mixture of toluene and acetonitrile or chromatography
where charcoal was used as the stationary phase. The yields and
properties of the prepared chiral ionic liquids 6a–f and 7a–f are
presented in Table 1.
possesses three substituents 6b,d,e were the obtained chiral ionic
liquids in liquid form. All of the prepared salts 6a–f and 7a–f were
characterized by spectroscopy. The structure of 3-(2-acetoxy-3-
phenylpropyl)-1-mehyl-1H-imidazol-3-ium bromide 6f was con-
firmed by X-ray crystallography (Fig. 1). The results of this study
show that N-methylimidazole alkylation reaction takes place with-
out racemization.
Table 1
The yields and properties of the prepared chiral ionic liquids 6a–f and 7a–f
R–
Compound 6
Compound 7
Yield (%)
mp (°C)
Yield (%)
mp (°C)
Figure 1. An ORTEP plot of (S)-3-(2-acetoxy-3-phenylpropyl)-1-mehyl-1H-imida-
zol-3-ium bromide. The following crystal structure has been deposited at the
Cambridge Crystallographic Data Centre and allocated the deposition number CCDC
801240.
a
b
c
d
e
f
CH3–
50
39
48
40
52
61
112–113
Liquid
132–133
Liquid
Liquid
217–218
96
89
85
90
87
97
65–78
Liquid
Liquid
Liquid
Liquid
Liquid
(CH3)2CH–
(CH3)2CH2CH–
(S)-CH3CH (CH3)CH–
Ph–
At room temperature bromides 6a,c,f, and 7a are solids. Their
possible use as solvents, catalysts or reagents in organic synthesis,
or as chiral auxiliaries in spectroscopic investigations is therefore
rather unlikely. In order to solve this problem we decided to ex-
change the bromide anions with carboxylates (acetate, trifluoro-
acetate) with use of Amberlite IRA 400. The commercial OH form
of the resin after exchange into the appropriate carboxylate form
was used for the preparation of various new optically active
PhCH2–
Most of the bromides of the imidazolium salts with a free hy-
droxy group 7b–f are liquids at room temperature and only com-
pound 7a solidified. For the corresponding acetates we observed
that the structure of the R group substantially influences the melt-
ing point. Only if the carbon atom connected to CH–OAc fragment

296
M. Poterała, J. Plenkiewicz / Tetrahedron: Asymmetry 22 (2011) 294–299
organic salts. In this way we prepared new optically active organic
salts, which were liquid at room temperature. For example, after
conversion of the very high melting bromide 6f into the acetate
8 or trifluoroacetate 9 the colorless liquids of high viscosity were
obtained (Fig. 2).
0.96 (d, 6H, J = 6.8 Hz), 1.60–1.65 (m, 2H), 1.84–1.96 (m, 1H),
4.27–4.31 (dd, 1H, J = 6.6 Hz, J = 7.8 Hz); 13C NMR (CDCl3) d ppm:
21.3, 23.2, 24.4, 43.2, 68.9, 180.5 (consistent with lit.13); IR nujol,
m
cmꢂ1): 3420, 1700, 1260, 1130, 1070, 900, 887.
Compound 2d: Yield 65%; mp 45–47 °C; ½a D24
¼ þ20:8 (c 1.02,
ꢁ
CHCl3); lit.14
½
a 2D0
ꢁ
¼ þ21:9 (c 1.0, CHCl3); 1H NMR (CDCl3) d ppm:
0.93 (t, 3H, J = 7.6 Hz), 1.03 (d, 3H, J = 6.8 Hz), 1.24–1.34 (m, 1H),
1.38–1.48 (m, 1H), 1.84–1.94 (m, 1H), 4.19 (d, 1H, J = 3, 6 Hz) and
13C NMR (CDCl3) d ppm: 11.7, 15.3, 23.6, 38.9, 74.6, 179.6 (consis-
O
O
F3C
O
O
tent with lit.15); IR nujol,
1040, 1010, 890.
m
cmꢂ1): 3460, 1715, 1240, 1120, 1110,
N
N
N
N
OAc
OAc
9
8
4.4. Preparation of optically active (S)-a-hydroxycarboxylic acid
methyl esters 3b–f
Figure 2. The structures of (S)-3-(2-acetoxy-3-phenylpropyl)-1-mehyl-1H-imida-
zol-3-ium acetate 8 and trifluoroacetate 9.
To a stirred solution at ꢂ30 °C of 0.1 mol of the appropriate
a-
acetoxy or -hydroxy acid in 200 mL of dry methanol, 8.1 mL
a
3. Conclusion
(13.05 g, 0.11 mol) of thionyl chloride were added slowly. The
solution was stirred at ꢂ30 °C for further 15 min, and then left
for 48 h at room temperature. Then, the solvent was evaporated
under reduced pressure. The mixture was alkalized to pH 9 with
an NaHCO3 solution, extracted with ethyl ether (5 ꢀ 50 mL), and
dried over MgSO4. After the solvent was evaporated, the resulting
A general and efficient method for the preparation of new type
of optically active ionic liquids based on a-hydroxycarboxylic acids
has been presented. We have modified Fukamoto’s method11 of an-
ion exchange in ionic liquids by ion exchange chromatography and
obtained good results and can be used for base sensitive ionic
liquids.
crude methyl ester of the
a-hydroxycarboxylic acid was purified
by distillation under reduced pressure or by crystallization from
petroleum ether–toluene mixture.
Compound 3b: Yield 95%; bp 61–62 °C, p = 15 mmHg;
4. Experimental
4.1. General
½
a 2D1
ꢁ
¼ þ21:7 (c 1.18, CHCl3); lit.16
½
a 2D4
ꢁ
¼ þ18:4 (c 1.20, CHCl3);
1H NMR (CDCl3) d ppm: 0.85 (d, 3H, J = 6.8 Hz), 1.01 (d, 3H,
J = 6.8 Hz), 2.06 (sept of d, 1H, J = 6.8 Hz, J = 3.6 Hz), 2.72 (br s,
1H), 3.78 (s, 3H), 4.04 (d, 1H, J = 3.6 Hz) and 13C NMR (CDCl3) d
ppm: 16.0, 18.7, 32.1, 52.4, 75.0, 175.4 (consistent with lit.17); IR(-
1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were re-
corded on a Varian Mercury 400 MHz spectrometer. IR spectra
were taken on a Carl Zeiss Specord M80 instrument. Optical rota-
tions were measured with a PolAAr 32 polarimeter. MS spectra
were recorded on a Micro-mass Q-ToF Premier instrument. The
reactions were monitored by TLC on Merck silica gel 60 (230–
400 mesh) plates and by GC with Agilent Technologies 6890N
instrument.
neat,
m
cmꢂ1): 3490, 2960, 2870, 1730, 1640, 1460, 1430, 1380,
1360, 1250, 1205, 1170, 1130, 1065, 1025, 990, 940, 885, 845,
820, 760.
Compound 3c: Yield 89%; bp 69–70 °C, p = 8 mmHg; ½a D21
¼ þ4:1
ꢁ
(c 2.20, CHCl3); lit.17
½
a 2D0
ꢁ
¼ þ3:9 (c 1.00, CHCl3), 1H NMR (CDCl3) d
ppm: 0.93 (d, 3H, J = 6.4 Hz), 0.94 (d, 3H, J = 6.4 Hz), 1.48–1.60 (m,
2H), 1.81–1.95 (m, 1H), 2.68 (d, 1H, J = 6.0 Hz), 3.77 (s, 3H), 4.20
(dt, 1H, J = 7.6 Hz, J = 6.0 Hz) and 13C NMR (CDCl3) d ppm: 21.5,
23.2, 24.4, 43.5, 52.4, 69.0, 176.3 (consistent with lit.17); IR (neat,
4.2. Preparation of the chiral a-acetoxycarboxylic acids 2b,f
m
cmꢂ1): 3460, 2960, 2870, 1730, 1465, 1435, 1360, 1265, 1210,
Sodium nitrate (13.8 g, 0.2 mol) was added portionwise to a
cooled (16 °C) and vigorously stirred mixture of the appropriate
amino acid (0.1 mol) in 300 ml of glacial acetic acid. Next, the reac-
tion mixture was stirred for 1 h at room temperature, and then the
acetic acid was evaporated on a rotary evaporator. Water (50 mL)
was added, and the product was extracted with ethyl ether. The or-
ganic layer was washed with water, dried over MgSO4, and evapo-
1135, 1080, 1010, 965, 845, 820.
Compound 3d: Yield 93%; bp 82–83 °C, p = 17 mmHg;
½
a 2D4
ꢁ
¼ þ26:9 (c 2.10, CHCl3); lit.9
½
a 2D5
ꢁ
¼ þ25:5 (c 2.00, CHCl3);
1H NMR (CDCl3) d ppm: 0.89 (t, 3H, J = 7.4 Hz), 0.97 (d, 3H,
J = 6.8 Hz), 1.19–1.30 (m, 1H), 1.31–1.42 (m, 1H), 1.76–1.86 (m,
1H), 2.7 (d, 1H, J = 6.4 Hz), 3.78 (s, 3H), 4.09 (dd, 1H, J = 6.4 Hz,
J = 4.1 Hz); 13C NMR (CDCl3) d ppm: 11.7, 15.4, 23.7, 39.1, 52.3,
rated to yield the appropriate a-acetoxycarboxylic acid, which was
used for further reactions without purification.
74.8, 175.4; IR (neat,
m
cmꢂ1): 3497, 2966, 2880, 1736, 1648,
1459, 1380, 1269, 1218, 1140, 1074, 1044, 1014.
Compound 3e: Yield 94%; mp = 53–55 °C; ½a D26
¼ þ177:4 (c 1.02,
ꢁ
4.3. Preparation of (S)-2-hydroxy-4-methylpentanoic acid 2c
and (2S,3S)-2-hydroxy-3-methylpentanoic acid 2d
CHCl3); lit.18
½
a 2D2
ꢁ
¼ þ174:0 (c 1.00, CHCl3); 1H NMR (CDCl3) d ppm:
3.50 (d, 1H, J = 5.6 Hz), 3.76 (s, 3H), 5.18 (d, 1H, J = 5.6 Hz), 7.32–
7.44 (m, 5H); 13C NMR (CDCl3) d ppm: 53.0, 72.8, 126.6, 128.5,
To a stirred and cooled to 0 °C, solution of L-leucine or L-iso-leu-
128.6, 138.2, 174.1 (consistent with lit.19); IR (nujol,
3430, 1740, 1050, 1065.
m
cmꢂ1):
cine (24.92 g, 0.189 mol) in 1.25 M H2SO4 (125 mL), a solution of
sodium nitrite (19.73 g, 0.286 mol) in H2O (100 mL) was added
dropwise. Next the mixture was stirred at 0 °C for 2 h and then
at room temperature for 15 h. After this time, the contents of the
flask were extracted with ethyl ether (6 ꢀ 75 mL). The organic
layer was dried over MgSO4 and diethyl ether evaporated to yield
Compound 3f: Yield 86%; mp = 44–45 °C; ½a D26
¼ ꢂ6:9 (c 2.03,
ꢁ
CHCl3); lit.20
½
a 2D4
ꢁ
¼ ꢂ5:4 (c 2.00, CHCl3); 1H NMR (CDCl3) d ppm:
2.70 (d, 1H, J = 6.4 Hz), 2.97 (dd, 1H, J = 14 Hz, J = 6.8 Hz), 3.13
(dd, 1H, J = 13.8 Hz, J = 4.4 Hz), 3.78 (s, 3H), 4.46 (ddd, 1H,
J = 6.8 Hz, J = 6.4 Hz, J = 4.4 Hz), 7.20–7.33 (m, 5H) and 13C NMR
(CDCl3) d ppm: 40.5, 52.5, 71.2, 126.9, 128.4, 129.4, 136.3, 174.5
the appropriate crude
a-hydroxycarboxylic acid 2c or 2d, which
was purified by recrystallization from hexane–ethyl ether mixture.
Compound 2c: Yield 73%; mp 73–75 °C; ½a D22
ꢁ
¼ ꢂ12:6 (c 0.44,
(consistent with lit.17); IR (nujol,
1730, 1100.
m
cmꢂ1): 3540–3100, 1750,
H2O); lit.12
½
a 2D2
ꢁ
¼ ꢂ12:7 (c 1.00, H2O); 1H NMR (CDCl3) d ppm:

M. Poterała, J. Plenkiewicz / Tetrahedron: Asymmetry 22 (2011) 294–299
297
4.5. Preparation of optically active diols 4a–f
To an ice-cooled solution of the appropriate
active diol 4a–f with stirring and ice-cooling. The solution was stir-
red at 0 °C for 5 min, and next at room temperature for 45 min.
Next, water (100 mL) was added, and the mixture was alkalized
to pH 8 with solid Na2CO3. The solution was immediately extracted
with ethyl ether (5 ꢀ 60 mL), and the combined extracts were
dried over anhydrous Na2SO4. The ether was evaporated, and the
product was distilled under reduced pressure or purified by silica
gel column chromatography with gradient AcOEt–hexane 9:1.
Compound 5a: Yield 87%; bp 57–58 °C p = 11 mmHg;
a-hydroxycarboxy-
lic acid methyl ester 3a–f (20 mmol) in anhydrous ethyl ether
(360 mL), LiAlH4 (0.759 g, 20 mmol) was slowly added. The result-
ing mixture was stirred at 0 °C for 1 h and then at room tempera-
ture for 3 h. The content of the flask was again cooled to 0 °C, and
after the addition of a THF/H2O (1:1) mixture (4 mL) was stirred
overnight at room temperature. The precipitate formed was fil-
tered off, and dissolved in 18% hydrochloric acid solution. The
resulting solution was extracted with ethyl acetate (6 ꢀ 40 mL)
and the combined organic layers were washed with saturated
Na2CO3 solution, dried over anhydrous Na2SO4, and evaporated
to dryness. The product was purified by distillation or recrystalliza-
tion from ethyl ether–hexane mixture.
½
a 2D5
ꢁ
¼ ꢂ13:5 (c 2.26, CHCl3); lit.27
½
a 2D0
ꢁ
¼ þ14:2 (c 6.00, CHCl3)
for enantiomer (R); 1H NMR (CDCl3,)
d
ppm: 1.35 (d, 3H,
J = 6.4 Hz), 2.08 (s, 3H), 3.40–3.48 (m, 2H), 5.04–5.11 (m, 1H),
13C NMR (CDCl3) d ppm: 18.6, 21.1, 35.2, 69.2, 170.3; IR (neat,
m
cmꢂ1): 2986, 2938, 2879, 1740, 1452, 1424, 1372, 1330, 1244,
1131, 1032, 956, 914, 668, 604, 513.
Compound 4a: Yield 86%; bp 91–92 °C, p = 14 mmHg;
Compound 5b: Yield 90%; bp 67–68 °C, p = 4 mmHg; ½a D25
¼ 18:2
ꢁ
½
a 2D2
ꢁ
¼ þ26:9 (c 2.26, CHCl3); lit.21
½
a 2D0
ꢁ
¼ þ28:0 (c 2.31, CHCl3);
(c 2.06, CHCl3), 1H NMR (CDCl3) d ppm: 0.92 (d, 3H, J = 6.8 Hz), 0.93
(d, 3H, J = 6.8 Hz), 2.0–2.09 (m, 1H), 2.10 (s, 3H) 3.45 (dd, 1H,
J = 10.8 Hz, J = 6.4 Hz), 3.52 (dd, 1H, J = 10.8 Hz, J = 4.2 Hz), 4.79–
4.84 (m, 1H); 13C NMR (CDCl3) d ppm: 17.5, 18.4, 20.9, 30.3, 32.8,
1H NMR (CDCl3) d ppm: 1.12 (d, 3H, J = 6.0 Hz), 3.32–3.38 (m,
1H), 3.55–3.60 (m, 1H), 3.79 (br s, 2H), 3.83–3.90 (m, 1H) and
13C NMR (CDCl3) d ppm: 18.7, 67.9, 68.3 (consistent with lit.22);
IR (neat,
m
cmꢂ1): 3340, 2970, 2925, 2870, 2320, 1650, 1455,
76.8, 170.6; IR (neat, m
cmꢂ1): 2966, 2874, 1740, 1465, 1428,
1370, 1130, 1040, 985, 915, 832.
1370, 1243, 1226, 1033, 1016, 982.
Compound 4b: Yield 45%, bp 81–82 °C, p = 5 mmHg; ½a D26
ꢁ
¼ þ9:2
Compound 5c: Yield 89%; bp 79–80 °C, p = 2 mmHg;
(c 0.92, CHCl3), lit.23
½
a 2D5
ꢁ
¼ þ15:2 (c 0.9, CHCl3); 1H NMR (CDCl3) d
½
a 2D6
ꢁ
¼ ꢂ29:6 (c 2.17, CHCl3), 1H NMR (CDCl3) d ppm: 0.91 (d, 3H,
ppm: 0.88 (d, 3H, J = 7.2 Hz), 0.93 (d, 3H, J = 6.8 Hz), 1.66 (octet, 1H,
J = 6.8 Hz), 3.35–3.39 (m, 1H), 3.46 (dd, 1H, J = 11.2 Hz, J = 8.0 Hz),
3.60 (br s, 2H), 3.65 (dd, 1H, J = 11.2 Hz, J = 2.4 Hz) and 13C NMR
(CDCl3) d ppm: 18.2, 18.7, 30.8, 64.8, 77.2 (consistent with lit.23);
J = 6.2 Hz), 0.93 (d, 3H, J = 6.2 Hz), 1.42–1.50 (m, 1H), 1.54–1.67
(m, 2H), 2.08 (s, 3H), 3.40 (dd, 1H, J = 10.8 Hz, J = 5.2 Hz), 3.50
(dd, 1H, J = 10.8 Hz, J = 4.4 Hz), 5.08 (m, 1H); 13C NMR (CDCl3) d
ppm: 21.0, 22.1, 22.9, 24.5, 34.8, 41.5, 70.8, 170.4; IR (neat,
m
IR (neat,
m
cmꢂ1): 3360, 2960, 2865, 1645, 1610, 1462, 1380,
cmꢂ1): 2960, 2863, 1735, 1460, 1430, 1365, 1235, 1220, 1134,
1020, 942, 920, 850, 795, 750.
1360, 1125, 1060, 1010, 870.
Compound 4c: Yield 76%; bp 68–69 °C, p = 0.1 mmHg;
Compound 5d: Yield 69%; bp 72–73 °C, p = 2 mmHg;
½
a 2D8
ꢁ
¼ ꢂ29:2 (c 1.88, EtOH); lit.24
½
a 2D3
ꢁ
¼ ꢂ24:4 (c 1.84, EtOH);
½
a 2D4
ꢁ
¼ ꢂ20:6 (c 2.14, CHCl3), 1H NMR (CDCl3) d ppm: 0.88 (d, 3H,
1H NMR (CDCl3) d ppm: 0.89 (d, 3H, J = 8.8 Hz), 0.91 (d, 3H,
J = 7.2 Hz), 1.13 (ddd, 1H, J = 13.8 Hz, J = 8.8 Hz, J = 4.6 Hz), 1.34
(ddd, 1H, J = 13.8 Hz, J = 8.6 Hz, J = 5.6 Hz), 1.68–1.82 (m, 1H),
3.35 (dd, 1H, J = 11.2 Hz, J = 8 Hz), 3.57(dd, 1H, J = 11.2 Hz,
J = 2.4 Hz), 3.64 (br s, 1H), 3.71–3.78 (m, 2H); 13C NMR (CDCl3) d
J = 7.2 Hz), 0.88 (t, 3H, J = 7.4 Hz), 1.08–1.19 (m, 1H), 1.43–1.54
(m, 1H), 1.76–1.86 (m, 1H), 2.08 (s, 3H), 3.45 (dd, 1H, J = 11.2 Hz,
J = 6.4 Hz), 3.54 (dd, 1H, J = 11.2 Hz, J = 3.6 Hz), 4.85 (m, 1H);
13C NMR (CDCl3) d ppm: 11.1, 14.3, 20.9, 24.5, 32.9, 36.7, 75.9,
170.4; IR (neat,
m
cmꢂ1) 2968, 2937, 2879, 1744, 1464, 1429,
ppm: 22.0, 23.3, 24.4, 41.9, 67.1, 70.4; IR (neat,
m
cmꢂ1): 3350,
1372, 1243, 1144, 1100, 1024, 935, 603
2950, 2864, 1645, 1460, 1378, 1360, 1165, 1138, 1060, 1020,
940, 912, 872, 835.
Compound 5e: Yield 92%; ½a D24
¼ ꢂ92:3 (c 2.85, CH3COCH3);
ꢁ
1H NMR (CDCl3) d ppm: 2.04 (s, 3H), 4.51 (dd, 1H, J = 11.6 Hz,
J = 6.8 Hz), 4.61 (dd, 1H, J = 7.6 Hz, J = 11.6 Hz), 5.12 (dd, 1H,
J = 7.6 Hz, J = 6.8 Hz), 7.31–7.43 (m, 5H); 13C NMR (CDCl3) d ppm:
Compound 4d: Yield 82%; bp 60–61 °C, p = 0.06 mmHg; ½a D28
¼ ꢂ4:9
ꢁ
(c 1.22, MeOH); 1H NMR (CDCl3) d ppm: 0.86 (d, 3H, J = 6.8 Hz), 0.90 (t,
3H, J = 7.2 Hz), 1.10–1.23 (m, 1H), 1.42–1.5 (m, 1H), 1.51–1.63 (m, 1H),
2.90 (br s, 2H), 3.46–3.52 (m, 2H), 3.66–3.71 (m, 1H) and 13C NMR
20.7, 49.8, 67.4, 127.7, 128.8, 128.9, 138.0, 170.3; IR (neat,
m
cmꢂ1):
1745, 1490, 1450, 1375, 1360, 1220, 1060, 1030, 905, 755, 690.
(CDCl3) d ppm: 11.2, 14.6, 25.0, 37.6, 64.6, 75.9; IR (neat,
m
cmꢂ1):
Compound 5f: Yield 86%; ½a D26
ꢁ
¼ ꢂ1:2 (c 2.07, CHCl3); 1H NMR
3370, 2960, 2863, 1455, 1370, 1130, 1065, 910, 855.
(CDCl3) d ppm: 2.07 (s, 3H), 3.02 (d, 2H, J = 6.8 Hz), 3.38 (dd, 1H,
J = 11.0 Hz, J = 6.8 Hz), 3.50 (dd, 1H, J = 11.0 Hz, J = 4.8 Hz), 5.19
(m, 1H), 7.24–7.34 (m, 5H); 13C NMR (CDCl3) d ppm: 20.9, 33.4,
Compound 4e: Yield 84%; mp = 61–63 °C; ½a D28
¼ þ40:0 (c 1.00,
ꢁ
EtOH); lit.25
½
a 2D0
ꢁ
¼ þ38:6 (c 1.00, EtOH); 1H NMR (CDCl3) d ppm:
3.41(br s, 1H), 3.61 (dd, 1H, J = 11.4 Hz, J = 8.6 Hz), 3.68 (dd, 1H,
J = 11.4 Hz, J = 3.2 Hz), 3.78 (br s, 1H), 4.76 (dd, 1H, J = 8.4 Hz,
J = 3.2 Hz), 7.26–7.35 (m, 5H); 13C NMR (CDCl3) d ppm: 68.0, 74.7,
38.4, 72.9, 126.9, 128.6, 129.4, 136.0, 170.1; IR (neat, m
cmꢂ1):
3025, 2924, 1740, 1490, 1450, 1420, 1368, 1230, 1070, 1024,
932, 743, 695.
126.0, 127.9, 128.5, 140.4 (consistent with lit.26); IR (nujol,
cmꢂ1): 3360, 3220, 1080, 1060, 1040, 1015, 900, 885, 740, 690.
m
4.7. Preparation of chiral acetoxy ionic liquids 6a–f
Compound 4f: Yield 82%; mp = 49–51 °C; ½a D27
¼ ꢂ31:0 (c 1.01,
ꢁ
EtOH); lit.23
½
a 2D4
ꢁ
¼ ꢂ33:5 (c 0.90, EtOH); 1H NMR (CDCl3) d ppm:
At first, N-methylimidazole (0.05 mol) was added to a solution
of the appropriate J-acetyl bromohydrins 5a–f (0.05 mol) in anhy-
drous acetonitrile (15 mL) and stirred in the dark for three days at
75–80 °C. Then, a charcoal (0.3 g) was added to the flask and stirred
at room temperature for a further 12 h. Next, the charcoal was fil-
tered off and the filtrate was evaporated to dryness. The residue
was washed a few times with diethyl ether and the remaining trace
amounts of the solvents were removed from the product under re-
duced pressure (0.05 mmHg) at 70–75 °C. The crude products 6a–f
were recrystallized from a mixture of acetonitrile and toluene or
purified by charcoal gradient chromatography with an ethyl ace-
tate–acetonitrile mixture (4:1, 2:1).
2.15 (br s, 2H), 2.71–2.82 (m, 2H), 3.53 (dd, 1H, J = 11.2 Hz,
J = 7.2 Hz), 3.69 (dd, 1H, J = 11.2 Hz, J = 3.2 Hz), 3.95 (m, 1H),
7.21–7.38 (m, 5H) and 13C NMR (CDCl3) d ppm: 39.8, 66.0, 73.0,
126.6, 128.6, 129.3, 137.7 (consistent with lit.23); IR (nujol,
cmꢂ1): 3270, 1085, 1065, 1035, 890.
m
4.6. Preparation of the optically active Jꢂacetyl bromohydrins
5a–f
A 45% solution of hydrogen bromide in acetic acid (33.0 g,
23.2 mL) was added dropwise over 10 min to 60.3 mmol optically

298
M. Poterała, J. Plenkiewicz / Tetrahedron: Asymmetry 22 (2011) 294–299
Compound 6a: Yield 50%; mp 112–113 °C, ½a D2
ꢁ
¼ þ1:3 (c 1.56,
4.8. Preparation of chiral hydroxyl ionic liquids 7a–f
CHCl3); 1H NMR (CDCl3) d: 1.31 (d, 3H, J = 6.4 Hz), 2.06 (s, 3H),
4.10 (s, 3H), 4.46 (dd, 1H, J = 14.4 Hz, J = 7.6 Hz), 4.74 (dd, 1H,
J = 14.4 Hz, J = 2.8 Hz,), 5.23 (m, 1H), 7.56 (s, 1H), 7.58 (s, 1H),
10.30 (br s, 1H); 13C NMR (CDCl3) d 17.03, 21.22, 36.78, 53.36,
68.76, 123.11, 123.34, 137.88, 169.90; MS [M+]calcd = 183.1134,
MS [M+]found = 183.4950, MS [2M++Brꢂ]calcd = 445.1450, MS
[2M++Brꢂ]found = 445.0612, MS [M++2Brꢂ]calcd = 342.9480, MS
[M++2Brꢂ]found = 343.1134, MS [2M++3Brꢂ]calcd = 604.9797, MS
[2M++3Brꢂ]found = 605.0938.
To a stirred solution of the appropriate imidazolium bromides
6a–f (1.5 mmol) in 4 mL of distilled water a catalytic amount of
55% hydrobromic acid was added dropwise to achieve pH 1. The
mixture was stirred at room temperature for four days and ex-
tracted with ethyl ether (5 ꢀ 2 mL). The aqueous layer was evapo-
rated to dryness and the crude product was purified by
chromatography. The column was packed with charcoal and the
product was eluted with an ethyl acetate–acetonitrile (9:1, 6:1,
3:1) mixture. The solvent was evaporated yielding the appropriate
chiral imidazolium bromides 7a–f.
Compound 6b: Yield 39%; oil; ½a D25
¼ þ11:5 (c 2.78, MeOH);
ꢁ
1H NMR (CDCl3) d: 0.91 (d, 3H, J = 6.8 Hz), 0.95 (d, 3H, J = 6.4 Hz),
1.85–1.96 (m, 1H), 2.02 (s, 3H), 4.04 (s, 3H), 4.32 (dd, 1H,
J = 14.4 Hz, J = 8.8 Hz), 4.74 (dd, 1H, J = 14.4 Hz, J = 2.8 Hz,), 5.00
(ddd, 1H, J = 8.8 Hz, J = 7.2 Hz, J = 2.8 Hz), 7.49 (s, 1H), 7.60 (s,
1H), 10.176 (br s, 1H); 13C NMR (CDCl3) d 17.3, 18.5, 20.8, 29.8,
36.6, 51.0, 75.9, 122.7, 123.5, 137.6, 170.2; MS [M+]calcd = 211.1447,
MS [M+]found = 211.5478, MS [2M++Brꢂ]calcd = 501.2076, MS
[2M++Brꢂ]found = 501.1274, MS [M++2Brꢂ]calcd = 370.9793, MS
[M++2Brꢂ]found = 371.1193, MS [2M++3Brꢂ]calcd = 661.0423, MS
[2M++3Brꢂ]found = 661.1789.
Compound 7a: Yield 92%; mp 65–78 °C, ½a D26
¼ þ20:1 (c 1.96,
ꢁ
MeOH); 1H NMR (D2O) d: 1.25 (d, 3H, J = 6.8 Hz), d 3.93 (s, 3H), 4.11
(dd, 1H, J = 14.0 Hz, J = 8.0 Hz), 4.14–4.24 (m, 1H), 4.33 (dd, 1H,
J = 14.0 Hz, J = 3.2 Hz), 7.48 (s, 1H), 7.52 (s, 1H), 8.76 (s, 1H);13C NMR
(D2O) d: 19.6, 36.4, 56.3, 66.5, 123.6, 124.1, 137.1; MS:
[M+]calcd = 141.1028, [M+]found = 141.0870, [2M++Brꢂ]calcd = 361.1239,
[2M++Brꢂ]found = 361.1461, [M++2Brꢂ]calcd = 300.9374, [M++2Brꢂ]found
301.0727, [2M++3Brꢂ]calcd = 520.9585, [2M++3Brꢂ]found = 521.2169.
=
Compound 7b: Yield 89%; oil; ½a D22
¼ þ10:0 (c 1.00, MeOH);
ꢁ
Compound 6c: Yield 48%; mp 132–133 °C; ½a D27
ꢁ
¼ ꢂ14:5 (c 1.52,
1H NMR (CDCl3) d: 0.98 (d, 3H, J = 6.8 Hz), 1.00 (d, 3H, J = 5.6 Hz),
1.79 (m, 1H), 3.65–3.75 (m, 1H), 4.04 (s, 3H), 4.29 (dd, 1H,
J = 13.6 Hz, J = 9.0 Hz), 4.36 (dd, 1H, J = 13.6 Hz J = 2.8 Hz), 4.70
(br s, 1H), 7.38 (s, 1H), 7.45 (s, 1H), 9.66 (br s, 1H); 13C NMR (CDCl3)
d: 18.1, 18.9, 31.9, 36.8, 53.8, 74.1, 122.8, 122.9, 137.6; MS:
CHCl3); 1H NMR (CDCl3) d: 0.81 (t, 6H, J = 6.8 Hz), 1.35–1.39 (m,
2H), 1.49–1.59 (m, 1H), 2.00 (s, 3H), 4.02 (s, 3H), 4.34 (dd, 1H,
J = 14.4 Hz, J = 7.2 Hz), 4.63 (dd, 1H, J = 14.4 Hz, J = 2.8 Hz), 5.18–
5.23 (m, 1H), 7.50 (s, 1H), 7.62 (s, 1H), 10.17 (br s, 1H); 13C NMR
(CDCl3) d: 20.9, 21.5, 22.8, 24.1, 36.5, 39.6, 52.8, 69.8, 122.9,
[M+]calcd = 169.1341,
[M+]found = 169.1032,
[2M++Brꢂ]calcd
=
123.4,
137.5,
170.1;
MS
MS
[M+]calcd = 225.1603,
MS
MS
! 417.1865, [2M++Brꢂ]found = 417.1732, [M++2Brꢂ]calcd = 328.9687,
[M++2Brꢂ]found = 329.2371, [2M++3Brꢂ]calcd = 577.0211, [2M++3Brꢂ]found
= 577.2922.
[M+]found = 225.4733,
[2M++Brꢂ]calcd = 529.2389,
[2M++Brꢂ]found = 529.1922, MS [M++2Brꢂ]calcd = 384.9949, MS
[M++2Brꢂ]found = 385.1609, MS [2M++3Brꢂ]calcd = 689.0736, MS
[2M++3Brꢂ]found = 689.1173.
Compound 7c: Yield 85%; oil; ½a D23
¼ ꢂ0:8 (c 1.20, MeOH);
ꢁ
1H NMR (CDCl3) d: 0.89 (d, 3H, J = 6.0 Hz), 0.91 (d, 3H, J = 6.0 Hz),
1.23 (ddd, 1H, J = 4.0 Hz, J = 9.2 Hz, J = 13.6 Hz), 1.47 (ddd, 1H,
J = 5.2 Hz, J = 9.2 Hz, J = 13.6 Hz), 1.77–1.91 (m, 1H), 4.03 (s, 3H),
4.05–4.11 (m, 1H), 4.24 (dd, 1H, J = 13.8 Hz, J = 8.2 Hz), 4.37 (dd,
1H, J = 13.8 Hz, J = 2.8 Hz), 4.73 (d, 1H, J = 6.4 Hz), 7.39 (s, 1H,
J = 1.6 Hz), 7.45 (s, 1H, J = 1.6 Hz), 9.87 (br s, 1H); 13C NMR (CDCl3)
d: 21.8, 23.3, 24.3, 36.7, 42.8, 55.8, 67.3, 122.8, 123.1, 137.4;
Compound 6d: Yield 40%; oil; ½a D25
¼ þ10:4 (c 1.35, MeOH);
ꢁ
1H NMR (CDCl3) d: 0.87 (t, 3H, J = 7.2 Hz), 0.98 (d, 3H, J = 6.8 Hz),
1.12–1.23 (m, 1H), 1.44–1.55 (m, 1H), 1.65–1.75 (m, 1H), 2.04 (s,
3H), 4.06 (s, 3H), 4.37 (dd, 1H, J = 14.4 Hz, J = 9.2 Hz), 4.73 (dd,
1H, J = 14.4 Hz, J = 2.6 Hz), 5.05 (ddd, 1H, J = 9.2 Hz, J = 6.4 Hz,
J = 2.6 Hz), 7.47 (s, 1H), 7.58 (s, 1H), 10.15 (br s, 1H); 13C NMR
(CDCl3) d: 11.1, 14.6, 20.9, 24.5, 36.3, 36.8, 50.9, 75.4, 122.7,
MS: [M+]calcd = 183.1497, [M+]found = 183.1244, [2M++Brꢂ]calcd
=
123.4,
137.9,
170.3;
MS
MS
[M+]calcd = 225.1603,
MS
MS
445.2178, [2M++Brꢂ]found = 445.2238, [M++2Brꢂ]calcd = 342.9844,
[M++2Brꢂ]found = 343.2159, [2M++3Brꢂ]calcd = 605.0524, [2M++3Brꢂ]found
= 605.1972.
[M+]found = 225.5788,
[2M++Brꢂ]calcd = 529.2389,
[2M++Brꢂ]found = 529.2013, MS [M++2Brꢂ]calcd = 384.9949, MS
[M++2Brꢂ]found = 385.0316, MS [2M++3Brꢂ]calcd = 689.0736, MS
[2M++3Brꢂ]found = 689.1250.
Compound 7d: Yield 90%; oil, ½a D22
¼ þ6:2 (c 1.62, MeOH);
ꢁ
1H NMR (CDCl3) d: 0.85 (t, 3H, J = 7.2 Hz), 0.92 (d, 3H, J = 6.8 Hz),
1.12–1.23 (m, 1H), 1.49–1.65 (m, 2H), 3.71 (m, 1H), 4.00 (s, 3H),
4.26 (dd, 1H, J = 13.8 Hz, J = 9.0 Hz), 4.36 (dd, 1H, J = 13.8 Hz,
J = 2.6 Hz), 4.72 (br s, 1H), 7.44 (s, 1H), 7.50 (s, 1H), 9.60 (br s,
1H); 13C NMR (CDCl3) d: 11.2, 14.9, 24.9, 36.8, 38.4, 53.5, 73.1,
122.9, 123.0, 137.4; MS: [M+]calcd = 183.1497, [M+]found = 183.3011,
[2M++Brꢂ]calcd = 445.2178, [2M++Brꢂ]found = 445.3624, [M++2Brꢂ]calcd
= 342.9844, [M++2Brꢂ]found = 343.1743, [2M++3Brꢂ]calcd = 605.0524,
[2M++3Brꢂ]found = 605.2692.
Compound 6e: Yield 57%; oil, ½a D23
¼ þ1:7 (c 1.50, CHCl3);
ꢁ
1H NMR (CDCl3) d: 2.02 (s, 3H), 4.07 (s, 3H), 4.71 (dd, 1H,
J = 12.6 Hz, J = 3.8 Hz), 4.89 (dd, 1H, J = 12.6 Hz, J = 9.0 Hz), 6.16
(dd, 1H, J = 9.0 Hz, J = 3.8 Hz), 7.32–7.35 (m, 3H), 7.45–7.49 (m,
3H), 7.63 (s, 1H), 10.52 (br s, 1H); 13C NMR (CDCl3) d: 20.8, 36.7,
62.3, 63.8, 121.1, 123.8, 127.5, 129.4, 129.9, 133.2, 137.2, 170.1;
MS
[M+]calcd = 245.1290,
MS
[M+]found = 245.5692,
MS
[2M++Brꢂ]calcd = 569.1763, MS [2M++Brꢂ]found = 569.0481, MS
[M++2Brꢂ]calcd = 404.9636, MS [M++2Brꢂ]found = 405.1051, MS
[2M++3Brꢂ]calcd = 729.0110, MS [2M++3Brꢂ]found = 729.6425.
Compound 7e: Yield 87%; ½a D23
ꢁ
¼ þ1:7 (c 1.16, MeOH); 1H NMR
(CDCl3) d: 3.99 (s, 3H), 4.13 (dd, 1H, J = 12.6 Hz, J = 3.8 Hz), 4.35
(dd, 1H, J = 12.6 Hz, J = 9.4 Hz), 5.27 (br s, 1H), 5.84 (dd, 1H,
J = 9.4 Hz, J = 3.8 Hz), 7.26–7.35 (m, 6H), 7.41 (s, 1H), 9.86 (br s,
1H); 13C NMR (CDCl3) d: 36.7, 62.7, 65.9, 121.6, 123.1, 127.6,
Compound 6f: Yield 61%; mp = 217–218 °C; ½a D24
¼ þ7:2 (c 1.52
ꢁ
CHCl3); H NMR (CDCl3) d 2.01 (s, 3H), 2.95 (dd, 1H, J = 14.0 Hz,
J = 7.6 Hz), 3.09 (dd, 1H, J = 14.0 Hz, J = 5.6 Hz), 4.07 (s, 3H), 4.42
(dd, 1H, J = 14.4 Hz, J = 8.0 Hz), 4.83 (dd, 1H, J = 14.4 Hz,
J = 2.8 Hz), 5.42 (m, 1H), 7.21–7.33 (m, 7H), 10.50 (br s, 1H);
13C NMR (CDCl3) d 21.0, 36.9, 37.7, 52.3, 72.5, 122.4, 123.0, 127.2,
128.7, 129.4, 135.2, 138.6, 170.1; MS [M+]calcd = 259.1447, MS
129.3, 129.5, 134.3, 136.8; MS: [M+]calcd = 203.1184, [M+]found
=
203.0830, [2M++Brꢂ]calcd = 485.1552, [2M++Brꢂ]found = 485.1305,
[M++2Brꢂ]calcd = 362.9531, [M++2Brꢂ]found = 363.0988, [2M++3Brꢂ]calcd
= 644.9898, [2M++3Brꢂ]found = 645.1596.
[M+]found = 259.4767,
MS
[2M++Brꢂ]calcd = 597.2076,
MS
Compound 7f: Yield 91%; ½a D21
ꢁ
¼ ꢂ5:4 (c 1.56, MeOH); 1H NMR d:
[2M++Brꢂ]found = 597.0545, MS [M++2Brꢂ]calcd = 418.9793, MS
[M++2Brꢂ]found = 418.8192, MS [2M++3Brꢂ]calcd = 757.0423, MS
[2M++3Brꢂ]found = 757.0931.
2.85 (dd, 1H, J = 13.8 Hz, J = 5.6 Hz), 2.94 (dd, 1H, J = 13.8 Hz,
J = 7.0 Hz), 3.86 (s, 3H), 4.19–4.34 (m, 3H), 4.97 (d, 1H, J = 6.0 Hz),
7.16–7.30 (m, 7H), 9.46 (br s, 1H); 13C NMR (CDCl3) d: 36.7, 40.6,

M. Poterała, J. Plenkiewicz / Tetrahedron: Asymmetry 22 (2011) 294–299
299
54.8, 70.3, 122.6, 122.9, 126.7, 128.6, 129.5, 137.3, 137.5; MS:
References
[M+]calcd = 217.1341,
[M+]found = 217.1015,
[2M++Brꢂ]calcd
=
513.1865, [2M++Brꢂ]found = 513.1896, [M++2Brꢂ]calcd = 376.9687,
[M++2Brꢂ]found = 376.9989, [2M++3Brꢂ]calcd = 673.0211, [2M++3Brꢂ]found
= 673.2875.
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Compound 8: Yield 93%;oil;
½
a 2D1
ꢁ
¼ ꢂ0:2 (c 2.26, MeOH);
1H NMR (CDCl3) d: 1.79 (s, 3H), 1.81 (s, 3H), 2.67–2.75 (m, 2H),
3.81 (s, 3H), 4.25 (dd, 1H, J = 8.4 Hz, J = 14.4 Hz), 4.55 (dd, 1H,
J = 2.6 Hz, J = 14.4 Hz), 5.24–5.26 (m, 1H), 7.09–7.19 (m, 5H), 7.22
(s, 1H), 7.33 (s, 1H), 9.60 (br s, 1H); 13C NMR (CDCl3) d 20.5, 24.5,
36.1, 37.3, 51.8, 72.5, 122.6, 123.4, 126.8, 128.4, 129.3, 135.8,
138.2, 170.1, 177.7; MS: [M+]calcd = 259.1447, [Mꢂ+]found = 259.4771,
[2M++CH3CO2ꢂ
]
]
calcd = 577.3026, [2M++CH3CO2ꢂ
]
]
found = 577.5361,
found = 377.2963,
ꢂ
[M++2CH3CO2
calcd = 377.1713, [M++2CH3CO2
[2M++3CH3CO2ꢂ
]
calcd = 695.3292,
found = 695.6149.
ꢂ
[2M++3CH3CO2
]
Compound 9: Yield 90%; oil; ½a D21
ꢁ
¼ ꢂ2:7 (c 1.64, MeOH);
1H NMR (CDCl3) d: 1.88 (s, 3H), 2.79 (dd, 1H, J = 7.8 Hz,
J = 14.2 Hz), 2.93 (dd, 1H, J = 5.2 Hz, J = 14.2 Hz), 3.86 (s, 3H), 4.28
(dd, 1H, J = 8.0 Hz, J = 14.4 Hz), 4.55 (dd, 1H, J = 2.8 Hz,
J = 14.4 Hz), 7.11–7.23 (m, 5H), 7.32 (s, 1H), 7.34 (s, 1H), 9.77 (br
s, 1H); 13C NMR (CDCl3) d 20.4, 36.0, 37.3, 51.9, 72.2, 117.2 (q,
1C, J = 292 Hz), 122.8, 123.3, 126.9, 128.5, 129.1, 135.3, 138.2,
160.8 (q, 1C, J = 32.4 Hz), 169.9; 19F NMR (376 MHz, CDCl3)
ꢂ75.013,
MS:
[M+]calcd = 259.1447,
[M+]found = 259.8910,
[2M++CF3CO2ꢂ
[M++2CF3CO2
[2M++3CF3CO2
]
]
calcd = 631.2743,
calcd = 485.1147,
]
[2M++CF3CO2ꢂ
]
]
found = 631.2682,
found = 484.9580,
ꢂ
ꢂ
[M++2CF3CO2
calcd = 857.2444, [2M++3CF3CO2
]
found = 857.0281.
ꢂ
ꢂ
Acknowledgment
We are grateful to Dean of the Chemistry Faculty for a financial
support of the work.