Chiral ionic liquids based on abietane

Article abstract of DOI:10.1134/S1070428009030099

A number of chiral ionic liquids were synthesized by reaction of 12-chloromethylabieta-8,11,13-trien-18-oic acid methyl ester with N-alkylimidazoles.

Full text of DOI:10.1134/S1070428009030099

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ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 3, pp. 404–407. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © V.A. Glushkov, M.S. Kotelev, K.S. Rudovskii, O.A. Maiorova, A.V. Tarantin, A.G. Tolstikov, 2009, published in Zhurnal
Organicheskoi Khimii, 2009, Vol. 45, No. 3, pp. 416–418.
Chiral Ionic Liquids Based on Abietane
V. A. Glushkova, M. S. Kotelevb, K. S. Rudovskiib, O. A. Maiorovab,
A. V. Tarantina, and A. G. Tolstikova
a Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences,
ul. Akad. Koroleva 3, Perm, 614990 Russia
e-mail: glusha@nm.ru
b Perm State University, Perm, Russia
Received June 3, 2008
Abstract—A number of chiral ionic liquids were synthesized by reaction of 12-chloromethylabieta-8,11,13-
trien-18-oic acid methyl ester with N-alkylimidazoles.
DOI: 10.1134/S1070428009030099
Ionic liquids are increasingly used in organic syn-
thesis and catalysis [1–3]. Among these, N,N′-disubsti-
tuted imidazolium salts have been studied most thor-
oughly [4]. Imidazolium salts containing chiral func-
tional groups are used for generation of N-heterocyclic
carbenes as catalysts and reagents in asymmetric
syntheses [5–7]. Chiral imidazole derivatives having
pinane fragments have been reported [8, 9]. Pernak
et al. [10] recently synthesized optically active ionic
liquids on the basis of menthol [10]. However, ionic
liquids based on di- and triterpenes remain so far
unknown.
(1R,4aR,4bR,10aR)-3-chloromethyl-7-isopropyl-1,4a-
dimethyl-1,2,3,4,4a,4b,5,6,10,10a-decahydrophenan-
threne-1-carboxylate]. As a result, we isolated imid-
azolium salts IIIa–IIIe (Scheme 1), whose structure
was confirmed by elemental analysis and IR and
1H NMR spectroscopy.
The IR spectra of IIIa–IIIe contained strong ab-
sorption bands at 1720–1724 cm–1, corresponding to
stretching vibrations of the ester carbonyl group, and
broad bands with their maxima at 3384–3412 cm–1.
The latter did not disappear even after drying under
reduced pressure (5 mm, 80°C, 1 h), indicating the
presence of crystallization water. Nevertheless, the
elemental compositions of compounds IIIa, IIIc, and
IIIe were consistent with the assumed structure; only
the data for imidazolium salts IIIb and IIId having
methyl and isopropyl groups, respectively, on the
nitrogen atom indicated that these compounds were
The goal of the present work was to synthesize new
chiral imidazolium salts (ionic liquids) on the basis of
abietane. For this purpose, we examined reactions of
imidazole (Ia) and N-alkylimidazoles Ib–Ie (R = Me,
CH2=CH, i-Pr, t-Bu) with 12-chloromethylabieta-
8,11,13-trien-18-oic acid methyl ester [II, methyl
Scheme 1.
4'
5'
N
R
Cl
N
Me
Me
2'
3
2
4
Me
Me
Me
Me
Cl–
5
8
+
N
N
1
R
6
4b
8a
10
7
9
H
H
Me
Me
COOMe
COOMe
II
Ia–Ie
IIIa–IIIe
R = H (a), Me (b), CH2=CH (c), i-Pr (d), t-Bu (e).
404

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CHIRAL IONIC LIQUIDS BASED ON ABIETANE
405
isolated as hydrate (IIIb) and hemihydrate (IIId) (see
Experimental).
by heating at 120–130°C. The elemental compositions
were determined on a Leco CHNS analyzer.
The 1H NMR spectra of IIIa–IIIe contained signals
from diastereotopic protons in the NCH2 group as two
doublets at δ 5.5–5.6 ppm with a coupling constant of
14–15 Hz, which is typical of geminal protons. The
2-H proton in the imidazole ring resonated at δ 9.64–
11.11 ppm. Compound IIIa displayed two signals from
2-H at δ 8.56 and 10.25 ppm with an intensity ratio of
1:1, indicating the presence of two tautomers. Signals
from the 4-H and 5-H protons in the imidazole ring of
compounds IIIa, IIIb, IIId, and IIIe were located in
the regions δ 6.98–7.03 and 7.27–7.38 ppm, while the
corresponding signals of IIIc were displaced down-
field (δ 7.82 and 8.31 ppm), presumably due to effect
of the N-vinyl group. Signals from protons in the aro-
matic ring of the hydrogenated phenanthrene fragment
appeared at δ 7.14–7.31 (4-H) and 6.88–7.03 ppm
(1-H). The NMe group in IIIb gave rise to a signal at
δ 4.12 ppm; its relatively downfield position is consist-
ent with the presence of positive charge on the corre-
sponding nitrogen atom. Presumably, analogous quat-
ernization of the imidazole nitrogen atom is typical of
compounds IIIc–IIIe. The optical rotations of chiral
imidazolium salts IIIa–IIIe smoothly decrease in the
R series H > CH2=CH > Me > t-Bu > i-Pr.
Imidazole and 1-methyl-1H-imidazole were com-
mercial products (from Lancaster). 1-Isopropyl- and
1-tert-butyl-1H-imidazoles were synthesized according
to the procedure described in [12]. Dehydroabietic
(abieta-8,11,13-trien-18-oic) acid was prepared by
desulfurization of 12-sulfodehydroabietic acid as re-
ported in [13]; the subsequent methylation with methyl
iodide in acetone in the presence of potassium carbo-
nate gave dehydroabietic acid methyl ester [14] which
was subjected to chloromethylation according to the
procedure described in [15]. Yield of 12-chloromethyl-
abieta-8,11,13-trien-18-oic acid methyl ester (II) 45%,
mp 117–119°C (from methanol). 1H NMR spectrum, δ,
ppm (abietane atom numbering is assumed): 1.15 d
(3H, CH3, J = 6 Hz), 1.17 d (3H, CH3, J = 6 Hz), 1.18 s
(6H, CH3), 1.37–1.83 m (7H, 1α-H, 2-H, 3-H, 6-H),
2.15 m (1H, 1β-H), 2.24 m (1H, 5-H), 2.81 m (2H,
7-H), 3.15 m (1H, 13-CH), 3.66 s (3H, OCH3), 4.56 s
(2H, CH2Cl), 6.90 s (1H, 14-H), 7.08 s (1H, 11-H).
Compounds IIIa–IIIe (general procedure). A mix-
ture of 10 mmol of compound II and 11 mmol of
imidazole IIIa–IIIe in 50 ml of benzene was heated
for 8–12 h under reflux until a solid separated. The
colorless product was filtered off, washed with ben-
zene, and dried under reduced pressure. In the syn-
thesis of compounds IIId and IIIe, the solvent was
distilled off, the precipitate was ground with diethyl
ether, and the liquid phase was separated by decanting
(this procedure was repeated three times). The undis-
solved imidazolium salt was filtered off and dried
under reduced pressure.
Formalistically, compounds IIIa–IIIe are ionic
liquids. Only imidazolium salt IIId has an anomalous-
ly low melting point (82–88°C), so that it could be
used as chiral solvent. In any case, all compounds
IIIa–IIIe attract interest as novel ligands for the
synthesis of metal complexes based on N-heterocyclic
carbenes.
1-[(4bS,8R)-2-Isopropyl-8-methoxycarbonyl-
4b,8-dimethyl-4b,5,6,7,8,8a,9,10-octahydrophenan-
thren-3-ylmethyl]-1H-imidazol-3-ium chloride (Ia).
Yield 54%, mp 214–217°C, [α]D24 = +58.4° (c = 1.07,
CHCl3). IR spectrum, ν, cm–1: 3404 br (NH), 1720
(C=O), 1580 (C=C), 1562 (C=N), 1504 (C=C), 1248,
EXPERIMENTAL
The IR spectra were measured on a Specord M80
spectrometer from samples dispersed in mineral oil.
The H NMR spectra were recorded on a Varian
1
Mercury Plus instrument at 300 MHz using CDCl3 or
DMSO-d6 (compound IIIc) as solvent and hexa-
methyldisiloxane as internal reference. Signals in the
1H NMR spectra were assigned taking into account the
data of [11]. The optical rotations (deg cm2 g–1) were
measured on a Perkin–Elmer 341 polarimeter in
chloroform of analytical grade, stabilized by addition
of 0.6–1% of ethanol. TLC analysis was performed on
Sorbfil plates using hexane–ethyl acetate as eluent
(10:1); spots were visualized by treatment with a 10%
solution of phosphomolybdic acid in ethanol, followed
1
1176, 1132, 1114, 1048, 958, 896. H NMR spectrum,
δ, ppm: 1.05 d (3H, CH3, J = 6.6 Hz), 1.08 d (3H, CH3,
J = 6.6 Hz), 1.15 s (3H, CH3), 1.25 s (3H, CH3),
1.42 m (2H, 5α-H, 6α-H), 1.60–1.83 m (5H, 6β-H,
7-H, 9-H), 2.15 m (1H, 5β-H), 2.24 m (1H, 8b-H),
2.88 m (3H, 10-H, 2-CH), 3.66 s (3H, OCH3), 5.52 m
(2H, NCH2), 6.98 s (1H, 1-H), 7.03 s (1H, 4′-H or
5′-H), 7.14 s (1H, 4-H), 7.31 s (1H, 5′-H or 4′-H),
8.57 s and 10.25 s (0.5H each, 2′-H); the HN+ signal
was not observed due to fast exchange. Found, %:
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 3 2009

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GLUSHKOV et al.
406
C 69.76; H 8.14; N 6.17. C25H35ClN2O2. Calculated,
%: C 69.67; H 8.18; N 6.50.
(1H, 6α-H), 1.61 d (6H, 3-CHMe2, J = 6.6 Hz), 1.69–
1.88 m (5H, 6β-H, 7-H, 9-H), 2.17 m (1H, 5β-H),
2.28 m (1H, 8b-H), 2.88 m (2H, 10-H), 3.00 m (1H,
2-CH), 3.66 s (3H, OCH3), 4.93 sept (1H, 3-CH),
5.51 d and 5.60 d (1H, NCH2, J = 14.7 Hz), 6.87 s
(1H, 1-H), 6.99 s (1H, 4′-H or 5′-H), 7.15 s (1H, 4-H),
7.38 s (1H, 5′-H or 4′-H), 11.01 br.s (1H, 2′-H). Found,
%: C 67.95; H 8.75; N 6.04. C26H40ClN2O2·0.5H2O.
Calculated, %: C 68.02; H 8.78; N 6.18.
1-[(4bS,8R)-2-Izopropyl-8-methoxycarbonyl-
4b,8-dimethyl-4b,5,6,7,8,8a,9,10-octahydrophenan-
thren-3-ylmethyl]-3-methyl-1H-imidazol-3-ium
chloride hydrate (Ib). Yield 62%, mp 233–234°C,
[α]D24 = +49.5° (c = 0.3, CHCl3). IR spectrum, ν, cm–1:
3384 br (OH), 1720 (C=O), 1576, 1504, 1250, 1178,
1132, 1114, 1048, 992, 958, 876. 1H NMR spectrum, δ,
ppm: 1.07 d (3H, CH3, J = 7 Hz), 1.12 d (3H, CH3, J =
7 Hz), 1.18 s (3H, CH3), 1.26 s (3H, CH3), 1.42 m (2H,
5α-H, 6α-H), 1.63–1.85 m (5H, 6β-H, 7-H, 9-H),
2.15 m (1H, 5β-H), 2.27 m (1H, 8b-H), 2.88 m (2H,
10-H), 2.94 m (1H, 2-CH), 3.66 s (3H, OCH3), 4.12 s
(3H, 3-CH3), 5.47 d and 5.53 d (1H each, NCH2, J =
14 Hz), 6.86 s (1H, 1-H), 6.99 s (1H, 4′-H or 5′-H),
7.15 s (1H, 4-H), 7.29 s (1H, 5′-H or 4′-H), 10.73 s
(1H, 2′-H). Found, %: C 67.13; H 8.30; N 5.86.
C26H37ClN2O2·H2O. Calculated, %: C 67.43; H 8.48;
N 6.05.
3-tert-Butyl-1-{[(4bS,8R)-2-isopropyl-4b,8-di-
methyl-8-(methoxycarbonyl)-4b,5,6,7,8,8a,9,10-octa-
hydrophenanthren-3-ylmethyl]-1H-imidazol-3-ium
chloride (Ie). Yield 44%, mp 219–221°C. [α]D21
=
+48.5° (c = 1, CHCl3). IR spectrum, ν, cm–1: 3384
(OH), 1724 (C=O), 1652 (C=N), 1548 (C=C), 1294,
1248, 1202, 1134, 1116, 1096, 1044, 966, 908.
1H NMR spectrum (CDCl3), δ, ppm: 1.07 d (3H, CH3,
J = 6 Hz), 1.09 d (3H, CH3, J = 6 Hz), 1.18 s (3H,
CH3), 1.26 s (3H, CH3), 1.41 m (2H, 5α-H, 6α-H),
1.73 s (9H, t-Bu), 1.63–1.88 m (5H, 6β-H, 7-H, 9-H),
2.17 m (1H, 5β-H), 2.27 m (1H, 8b-H), 2.87 m (2H,
10-H), 3.07 m (1H, 2-CH), 3.66 s (3H, OCH3), 5.62 d
and 5.69 d (1H each, NCH2, J = 15 Hz), 6.87 s (1H,
1-H), 6.99 s (1H, 4′-H or 5′-H), 7.17 s (1H, 4-H),
7.38 s (1H, 5′-H or 4′-H), 11.11 br.s (1H, 2′-H). Found,
%: C 70.08; H 8.85; N 6.01. C27H42ClN2O2. Calculat-
ed, %: C 71.50; H 8.90; N 5.75.
1-[(4bS,8R)-2-Isopropyl-8-methoxycarbonyl-
4b,8-dimethyl-4b,5,6,7,8,8a,9,10-octahydrophenan-
thren-3-ylmethyl]-3-vinyl-1H-imidazol-3-ium
chloride (Ic). Yield 55%, mp 183–186°C, [α]D24
=
+53.4° (c = 1.07, CDCl3). IR spectrum, ν, cm–1: 3412
br (OH), 1722 (C=O), 1658 (C=C), 1568 (C=N), 1548,
1506 (C=C), 1250, 1176, 1134, 1112, 1046, 964.
1H NMR spectrum (DMSO-d6), δ, ppm: 1.02 d (3H,
CH3, J = 6.6 Hz), 1.07 d (3H, CH3, J = 6.6 Hz), 1.15 s
(3H, CH3), 1.20 s (3H, CH3), 1.32 m (2H, 5α-H,
6α-H), 1.57–1.82 m (5H, 6β-H, 7-H, 9-H), 2.03 m (1H,
8b-H), 2.33 m (1H, 5β-H), 2.81 m (2H, 10-H), 3.07 m
(1H, 2-CH), 3.66 s (3H, OCH3), 5.40 d.d (1H,
CH2=CH, J = 8.7, J 2.1 Hz), 5.45 d and 5.52 d (1H
each, NCH2, J = 14.4 Hz), 6.03 d.d (1H, =CH2, J =
15.6, 2.1 Hz), 7.03 s (1H, 1-H), 7.31 s (1H, 4-H),
7.38 d.d (1H, =CH2, J = 15.6, 8.7 Hz), 7.82 s and
8.31 s (1H each, 4′-H, 5′-H), 9.64 s (1H, 2′-H). Found,
%: C 69.24; H 8.34; N 5.87. C25H35ClN2O2. Calculat-
ed, %: C 69.67; H 8.19; N 6.65.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 07-03-96033-ural). The authors thank V.I. Karma-
nov for recording the IR spectra.
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