N-heterocyclic carbenes: V. synthesis of imidazolium salts from lupane series

Article abstract of DOI:10.1134/S1070428012050120

By the reaction of N-alkyl- and N-arylimidazoles with 30-bromo-3,28- diacetoxylup-20(29)-ene a series was synthesized of unsymmetrically substituted chiral imidazolium bromides with a lupane fragment.

Full text of DOI:10.1134/S1070428012050120

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 5, pp. 699−704. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.A. Glushkov, M.A. Zhiguleva, O.A. Maiorova, A.A. Gorbunov, 2012, published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48,
No. 5, pp. 701−706.
N-Heterocyclic Carbenes: V.* Synthesis of Imidazolium Salts
from Lupane Series
V. A. Glushkova, M. A. Zhigulevab, O. A. Maiorovaa, and A. A. Gorbunova
aInstitute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, 614013 Russia
e-mail: glusha55@gmail.com
bPerm State National Research University, Perm, 614990 Russia
Received July 27, 2011
Abstract—By the reaction of N-alkyl- and N-arylimidazoles with 30-bromo-3,28-diacetoxylup-20(29)-ene a series
was synthesized of unsymmetrically substituted chiral imidazolium bromides with a lupane fragment.
DOI: 10.1134/S1070428012050120
for the study of their biological action, whereas imidazole-
substituted triterpenes are yet poorly understood; as one
example 1-[3,12-dioxo-2-cyanooleana-1,9(11)-dien-28-
oyl]-4-ethynylimidazole may be cited, a new antiphlo-
gistic and cytoprotective agent −[13].
The use of N-heterocyclic carbenes as ligands in Pd-
catalyzed cross-coupling reactions after the pioneering
research of Herrmann [2] became an everyday practice of
the organic synthesis [3]. The development of this field of
chemistry occurs along the following main directions: the
application of preliminary prepared stable N-heterocyclic
palladium(II) complexes (“well-defined catalysts”) as
precursors of active catalysts [4], synthesis of chiral
imidazolium salts for enantioselective conversions [5],
employing mixed phosphano-carbene catalysts [6], the
use of so-called “abnormal” carbenes [7], the involvement
into the reaction of inactive chloroarenes [8], application
of sterically hindered ligands to raise the yield of cross-
coupled products [9]. In the latter case the interest was
not yet directed to the possibility to use imidazolium
salts underlain by di- and triterpene matrices. However
we recently demonstrated the possibility to synthesize
imidazolium salts from methyl dehydroabietate and suc-
cessfully used them as N-heterocyclic carbene ligands in
Suzuki–Miyaura reaction [10]. The aim of this study was
the preparation of imidazolium salts from triterpenes,
namely, from betulin 3,28-diacetate and testing their
possible application as N-heterocyclic carbene ligands
in cross-coupling reactions.
Compounds IIIa–IIIj were obtained from
1-alkyl(aryl)-1H-imidazoles and 30-bromo-3,28-diace-
toxylup-20(29)-ene (II) in boiling acetonitrile (see the
scheme).
Synthesized salts IIIa–IIIj were purified by column
chromatography on silica gel and were isolated as hy-
drates or solvates with ethanol of diverse composition in
27–98% yields (previously the inclusion of water into the
crystal lattice was observed in a number of imidazolium
salts based on diterpenes [1]). Compounds IIIa–IIIj are
light-yellow crystalline or glassy substances soluble in
acetone, toluene, chloroform, ethyl acetate, poorly soluble
in hexane. Their structure was confirmed by IR, 1H and
13C NMR spectra (see EXPERIMENTAL). The IR spectra
of compounds IIIa–IIIj contain the bands of two acetoxy
groups at 1727–1734 cm–1 showing the stability of the
ester function under the reaction conditions. All samples
contain a broadened band at 3340 cm–1 corresponding to
OH groups of water and (or) of ethanol solvate, whose
presence is also confirmed by the date of 1H NMR spectra
(a triplet at δ 1.17–1.25 and a quartet at δ 3.65–3.73 ppm,
J 6.9–7.2 Hz).
Some 30-dialkylamino [11] and 30-hydroxylamino
lupane derivatives [12] have been described synthesized
______________
*For Communication IV, see [1].
For the estimation of the possibility to use new ligands
699

GLUSHKOV et al.
700
Scheme.
Br
R
N
29
N+
_
30
Δ
Br
OAc
+
N
N
MeCN
R
OAc
_
Ia–Ij
Iа Ii
28
1
AcO
3
AcO
_
IIIa–IIIj
IIIа IIIi
II
R = H (a), Me (b), Vin (c), i-Pr (d), t-Bu (e), Bn (f), Ph (g), 2-MeC6H4 (h), 2,6-Me2C6H3 (i), 2,4,6-Me3C6H2 (j).
in cross-coupling reaction we chose Heck model reaction
[14] between iodobenzene and butyl acrylate in the pres-
ence of 2 mol% Pd(II) acetate, 3 mol% of NHC-ligand,
3 equiv of triethylamine as a base and pentadecane as an
internal reference. The application of complexes NHC–
Pd(II) in Heck reaction is described in numerous papers
[15]. It is generally agreed now that the catalytically
active are mono-coordinated Pd(0) species generated
in the reaction mixture at the thermal decay of the first
formed bicoordinated complexes [16], therefore we have
taken the ratio Pd–ligand equal to 1:1.5. The reaction was
carried out for 1.5 h in DMF at 90°C (the formation of
palladium black was observed to the end of experiments).
The composition of the mixture was analyzed by GC-MS
method. The quantitative evaluation of the mixtures com-
position was performed by comparison with calibration
curves measured on arbitrary prepared mixtures of pure
iodobenzene and butyl cinnamate. The conversion was
estimated by the amount of the remaining iodobenzene,
the yield, by the quantity of the formed butyl cinnamate.
The experiments showed that in the above conditions for
NHC-ligands IIIa, IIIb, IIId–IIIj in the model reaction
the conversion attained 95–97%, the yields of butyl cin-
namate 54–88%. Ligand IIIc containing a vinyl group in
the imidazole ring inhibited Heck reaction: conversion
was 6%, no product of cross-coupling was detected.
and 1-mesityl-1H-imidazole were synthesized by method
[17]. Melting points were measured on an instrument
OptiMelt Automated Melting Point System (Stanford
Research Systems). As the melting point was considered
the threshold melting temperature at a heating rate 1 deg/
min. TLC was performed on Sorbfil plates, eluent chloro-
form–ethanol, 5:1 v/v, development under UV irradiation
or by treatment with 5% H
2SO4 followed by heating to
120–150°C. The column chromatography was carried out
on Silica gel 60 (0.035–0.070 mm, 220–440 mesh, Alfa
Aesar, eluent chloroform–ethyl acetate, 10 : 1, adding
2% of ethanol to the end of chromatographing. IR spectra
were registered on a spectrophotometer Bruker IFS 66ps
from mulls in mineral oil or a thin film prepared from a
chloroform solution. 1H and 13C NMR spectra were re-
corded from solutions in CDCl3 on a spectrometer Varian
Mercury+300 at 300 and 75 MHz respectively, internal
1
reference for H NMR spectra HMDS (δH 0.055 ppm),
for 13C NMR spectra the solvent signal served as internal
reference (CHCl3, δC 77.0 ppm). The optical rotation was
measured on a polarimeter Perkin Elmer 341 in chloro-
form stabilized with 0.5% of ethanol, and it is reported in
the units 10–1 deg g–1 cm2. The elemental analysis was
carried out in the Institute of Technical Chemistry, Ural
Division, Russian Academy of Sciences on an analyzer
Leco CHNS 9321P.
Synthesis of imidazolium salts of lupane series.
General procedure. A solution of 599 mg (1 mmol) of
30-bromo-3,28-diacetoxylup-20(29)-ene [18] and 1 mmol
of an appropriate imidazole in 30 ml of acetonitrile was
boiled for 6–8 h, evaporated, the residue was subjected
to column chromatography.
EXPERIMENTAL
Imidazole, N-methylimidazole, N-benzylimidazole,
N-vinylimidazole, and N-phenylimidazole were pur-
chased fromAlfaAesar (Lancaster); 1-(2-methylphenyl)-
1H-imidazole, 1-(2,6-dimethylphenyl)-1H-imidazole,
3-[3,28-Diacetoxylup-20(29)-en-30-yl]-1H-imid-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 5 2012

N-HETEROCYCLIC CARBENES: V.
701
azol-3-olium bromide·C2H5OH (IIIa). Yield 27%.
Light-yellow crystals, mp 144.3°C, Rf 0.73, [α]D25 +1.0
(c 0.5, CHCl3). ANDQ IR spectrum, cm–1 (from thin
film): 3427 br.w (OH), 2941, 2871, 1730, 1651 w, 1560 w,
1456, 1372, 1246, 1155 w, 1031, 979, 907, 755. 1H NMR
spectrum, δ, ppm (multiplets of groups CH and CH2 of
lupane framework are not shown): 0.84 s (6H, 2Me),
0.97 s (3H, Me), 1.02 s (3H, Me), 1.23 t (3H, CH3CH2O,
J 7.2 Hz), 1.39 s (3H, Me), 2.03 s (3H, MeC=O), 2.06 s
(3H, MeC=O), 2.27 m (1H, H19), 3.69 q (2H, CH3CH2O,
J 7.2 Hz), 3.75 d (1H, H28, J 10.8 Hz), 4.23 d (1H, H28,
J 10.8 Hz), 4.46 m (1H, H3), 4.71 s (1H, H29), 4.94 d
(1H, H30, J 15.0 Hz), 5.04 d (1H, H30, J 15.0 Hz), 5.14 s
(1H, H29), 6.87 s (1HHt), 7.13 s (1H, NH), 7.49 s (1HHt),
10.46 s (1H, NCH=N). 13C NMR spectrum, δ, ppm: 14.60,
15.87, 16.01, 16.34, 17.98, 20.74, 20.88, 21.18, 23.51,
26.75, 27.16, 27.79, 29.49, 31.35, 33.95, 34.08, 36.89,
37.15, 37.63, 38.26, 40.74, 42.53, 43.47, 46.28, 50.03,
51.31, 54.17, 55.19, 57.98, 62.02, 80.72, 112.39, 122.25,
128.81, 148.18, 170.89 (C=O), 171.34 (C=O). Found,
%: C 65.33; H 8.65; N 3.72. C37H57BrN2O4·C2H5OH.
Calculated, %: C 65.07; H 8.82; N 3.89.
s (3H, Me), 0.96 s (3H, Me), 1.01 s (3H, Me), 1.23 t
(3H, CH3CH2O, J 6.9 Hz), 1.38 s (3H, Me), 2.03 s (3H,
MeC=O), 2.05 s (3H, MeC=O), 2.29 m (1H, H19), 3.73 q
(2H, CH3CH2O, J 6.9 Hz), 3.75 d (1H, H28, J 10.8 Hz),
4.38 d (1H, H28, J 10.8 Hz), 4.45 m (1H, H3), 4.82 s
(1H, H29), 5.02 d (1H, H30, J 15.0 Hz), 5.10 d (1H, H30,
J 15.0 Hz), 5.16 s (1H, H29), 5.45 d.d (HCC=, Jca 9.0,
Jcb 3.3 Hz), 5.96 d.d (HbC=, Jba 15.6, Jbc 3.3 Hz), 7.29 s
(1HHt), 7.47 (HaC=, Jab 15.6, Jac 9.0 Hz), 7.70 s (1HHt),
11.14 s (1H, NCH=N). 13C NMR spectrum, δ, ppm :
14.52, 15.79, 15.95, 16.27, 17.90, 20.67, 20.86, 21.13,
23.43, 26.67, 27.11, 27.72, 29.41, 31.26, 33.85, 34.01,
36.81, 37.12, 37.54, 38.17, 40.65, 42.45, 43.16, 46.17,
49.88, 49.93, 54.24, 55.10, 62.04, 80.69, 109.95, 113.00,
119.57, 122.82, 128.11, 136.13, 147.67, 171.86 (C=O),
171.33 (C=O). Found, %: C 63.62; H 7.93; N 4.09.
C39H59BrN2O4·C2H5OH·H2O. Calculated, %: C 64.16;
H 8.61; N 3.74.
3-[(3,28-Diacetoxylup-20(29)-en-30-yl]-1-isopro-
pyl-1H-imidazol-3-olium bromide·C2H5OH·2H2O
(IIId). Yield 84%. Light-yellow glassy substance, mp
164.9°C, Rf 0.38, [α]D21 –1.2 (c 0.5, CHCl3). IR spectrum,
cm–1 (from thin film): 3409 br.w (OH), 2943, 2873,
1729, 1649 w, 1557, 1457, 1372, 1247, 1150, 1031, 978.
1H NMR spectrum, δ, ppm (multiplets of groups CH and
CH2 of lupane framework are not shown): 0.82 s (3H,
Me), 0.83 s (3H, Me), 0.96 s (3H, Me), 1.02 s (3H, Me),
1.23 t (6H, 2CH3CH2O, J 6.9 Hz), 1.38 s (3H, Me), 1.65
d (6H, Me2CH, J 6.6 Hz), 2.03 s (3H, MeC=O), 2.05 s
(3H, MeC=O), 2.30 m (1H, H19), 3.71 q (4H, 2CH3CH2O,
J 6.9 Hz), 3.76 d (1H, H28, J 11.1 Hz), 4.23 d (1H, H28,
J 11.1 Hz), 4.45 m (1H, H3), 4.77 s (1H, H29), 4.91 m (1H,
Me2CH, J 6.6 Hz), 5.01 d (1H, H30, J 15.9 Hz), 5.09 d
(1H, H30, J 15.9 Hz), 5.14 s (1H, H29), 7.16 m (1HHt),
7.29 m (1HHt), 10.91 s (1H, NCH=N). 13C NMR spec-
trum, δ, ppm: 14.49, 15.74, 15.88, 16.22, 17.85, 20.63,
20.79, 21.07, 22.91, 22.94, 23.38, 26.62, 27.00, 27.67,
29.35, 31.16, 33.81, 33.95, 36.75, 36.99, 37.49, 38.12,
40.60, 42.39, 43.16, 46.12, 49.83, 53.21, 53.93, 55.05,
61.94, 80.61, 112.62, 120.22, 122.29, 136.22, 148.00,
170.77 (C=O), 171.24 (C=O). Found, %: C 62.40; H 8.20;
N 3.48. C40H63BrN2O4·C2H5OH·2H2O. Calculated, %:
C 62.90; H 9.01; N 3.58.
3-[3,28-Diacetoxylup-20(29)-en-30-yl]-1-methyl-
1H-imidazol-3-olium bromide·1/2C2H5OH (IIIb).
Yield 79%. Light-yellow crystals, mp 141.3°C, Rf 0.24,
[α]D21 +2.6 (c 0.5, CHCl3). IR spectrum, cm–1 (mull in
mineral oil): 3405 br (OH), 1729, 1563, 1244, 1029, 896,
723. 1H NMR spectrum, δ, ppm (multiplets of groups CH
and CH2 of lupane framework are not shown): 0.83 s (3H,
Me), 0.84 s (3H, Me), 0.96 s (3H, Me), 1.01 s (3H, Me),
1.23 t (1.5H, 1/2CH3CH2O, J 6.9 Hz), 1.38 s (3H, Me),
2.03 s (3H, MeC=O), 2.06 s (3H, MeC=O), 2.26 m (1H,
1
H19), 3.71 q (1H, /2CH3CH2O, J 6.9 Hz), 3.79 d (1H,
H28, J 11.1 Hz), 4.13 s (3H, NMe), 4.23 d (1H, H28, J 11.1
Hz), 4.45 m (1H, H3), 4.77 s (1H, H29), 4.92 d (1H, H30,
J 15.6 Hz), 5.02 d (1H, H30, J 15.6 Hz), 5.15 s (1H, H29),
7.15 s (1HHt), 7.27 s (1H, NH), 7.49 s (1HHt), 10.66 s
(1H, NCH=N). Found, %: C 67.22; H 8.27; N 4.50.
C38H59BrN2O4 ·1/2C2H5OH. Calculated, %: C 65.90; H
8.79; N 3.94.
[3,28-Diacetoxylup-20(29)-en-30-yl]-1-vinyl-3-
1H-imidazol-3-olium bromide·C2H5OH·H2O (IIIc).
Yield 45%. Light-yellow crystals, mp 148.9°C, Rf 0.38,
[α]D25 +4.8 (c 0.5, CHCl3). IR spectrum, cm–1 (from thin
film): 3421 br (OH), 2943, 2872, 1728, 1653 w, 1556,
1455, 1372, 1248, 1168, 1031, 977, 912, 755. 1H NMR
spectrum, δ, ppm (multiplets of groups CH and CH2 of
lupane framework are not shown): 0.82 s (3H, Me), 0.83
1-tert-Butyl-3-[3,28-diacetoxylup-20(29)-en-30-yl]-
1H-imidazol-3-olium bromide·C2H5OH·2H2O (IIIe).
Yield 88%. Light-yellow crystals, mp 147.7°C, Rf 0.46,
[α]D21 –0.6 (c 0.5, CHCl3). IR spectrum, cm–1 (from thin
film): 3402 br.w (OH), 2943, 1730, 1652 w, 1554, 1459,
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GLUSHKOV et al.
702
2872, 1729, 1598, 1555, 1499, 1456, 1370, 1247, 1030,
978. H NMR spectrum, δ, ppm (multiplets of groups
1374, 1245, 1134, 1030, 979. 1H NMR spectrum, δ, ppm
(multiplets of groups CH and CH2 of lupane framework
are not shown): 0.82 s (3H, Me), 0.83 s (3H, Me), 0.96 s
(3H, Me), 1.02 s (3H, Me), 1.25 t (3H, CH3CH2O,
J 6.9 Hz), 1.38 s (3H, Me), 1.75 s (9H, Me3C), 2.03 s (3H,
MeC=O), 2.05 s (3H, MeC=O), 2.32 m (1H, H19), 3.71 q
(2H, CH3CH2O, J 6.9 Hz), 3.77 d (1H, H28, J 11.1 Hz),
4.23 d (1H, H28, J 11.1 Hz), 4.45 m (1H, H3), 4.77 s (1H,
H29), 5.12 s (1H, H29), 5.13 d (1H, H30, J 15.9 Hz), 5.20 d
(1H, H30, J 15.9 Hz), 7.18 t (1H, HHt, J 1.8 Hz), 7.34 t (1H,
HHt, J 1.8 Hz), 10.91 s (1H, NCH=N). 13C NMR spectrum,
δ, ppm: 14.49, 15.72, 15.85, 16.19, 17.83, 20.63, 20.74,
21.03, 23.35, 26.60, 26.92, 27.65, 29.33, 29.88, 30.28,
31.09, 33.79, 33.91, 36.73, 36.99, 37.46, 38.11, 40.58,
42.37, 43.24, 46.11, 49.71, 49.82, 53.78, 55.03, 60.35,
61.91, 80.57, 112.42, 119.68, 122.31, 136.08, 148.11,
170.67 (C=O), 171.14 (C=O). Found, %: C 63.82; H 8.25;
N 3.97. C41H65BrN2O4·C2H5OH·2H2O. Calculated, %:
C 63.61; H 9.31; N 3.45.
1
CH and CH2 of lupane framework are not shown): 0.82 s
(3H, Me), 0.83 s (3H, Me), 0.96 s (3H, Me), 1.01 s (3H,
Me), 1.23 t (3H, CH3CH2O, J 7.2 Hz), 1.38 s (3H, Me),
2.03 s (3H, MeC=O), 2.06 s (3H, MeC=O), 2.35 m (1H,
H19), 3.70 q (2H, CH3CH2O, J 7.2 Hz), 3.74 d (1H, H28,
J 10.2 Hz), 4.25 d (1H, H28, J 10.2 Hz), 4.45 m (1H,
H3), 4.86 s (1H, H29), 5.17 s (1H, H29), 5.20 d (1H, H30,
J 14.7 Hz), 5.35 d (1H, H30, J 14.7 Hz), 6.79 m (1HHt),
7.20 m (1HHt), 7.56 m (3H, Ph), 7.82 m (2H, Ph), 10.50 s
(1H, NCH=N). Found, %: C 65.58; H 7.66; N 3.87.
C43H61BrN2O4·C2H5OH·1.5H2O. Calculated, %: C 65.67;
H 8.57; N 3.40.
3-[3,28-Diacetoxylup-20(29)-en-30-yl]-1-(2-
methylphenyl)-1H-imidazol-3-olium bromide, mono-
hydrate (IIIh). Yield 97%. Light-yellow crystals, mp
148.2°C, Rf 0.47, [α]D21 +3.7 (c 0.5, CHCl3). IR spectrum,
cm–1 (from thin film): 3402, 2944, 2872, 1730, 1553 1494,
1455, 1370 1246, 1030, 978. 1H NMR spectrum, δ, ppm
(multiplets of groups CH and CH2 of lupane framework
are not shown): 0.83 s (9H, 3 Me), 0.98 s (3H, Me), 1.02
s (3H, Me), 2.03 s (3H, MeC=O), 2.05 s (3H, MeC=O),
2.32 s (3H, MeAr), 2.95 br.s (1H, OH), 3.78 d (1H, H28,
J 10.8 Hz), 4.25 d (1H, H28, J 10.8 Hz), 4.45 m (1H, H3),
4.86 s (1H, H29), 5.16 s (1H, H29), 5.30 d (1H, H30, J 15.6
Hz), 5.42 d (1H, H30, J 15.6 Hz), 7.37–7.48 m (6H, 2HHt
+ 4Harom), 10.60 s (1H, NCH=N). 13C NMR spectrum,
δ, ppm: 14.63, 15.86, 15.99, 16.31, 17.75, 17.96, 20.75,
20.85, 21.13, 23.48, 26.76, 27.15, 27.77, 29.48, 31.44,
33.93, 34.05, 36.87, 37.16, 37.60, 38.24, 40.73, 42.52,
43.29, 46.27, 49.97, 54.51, 55.15, 62.05, 80.72, 112.55,
122.97, 126.32, 127.64, 130.95, 131.89, 133.05, 133.58,
137.94, 148.48, 170.85 (C=O), 171.25 (C=O). Found, %:
C 67.15; H 8.00; N 4.03. C44H63BrN2O4·H2O. Calculated,
%: C 67.15; H 8.38; N 3.58.
1-Benzyl-3-[3,28-diacetoxylup-20(29)-en-30-yl]-
1H-imidazol-3-olium bromide·C2H5OH·H2O (IIIf).
Yield 98%. Light-yellow crystals, mp 171.1°C, Rf 0.42,
[α]D21 +1.1 (c 0.5, CHCl3). IR spectrum, cm–1 (from thin
film): 3401 br.w (OH), 2943, 2872, 1727, 1559, 1454,
1369, 1248, 1153, 1030, 978. 1H NMR spectrum, δ, ppm
(multiplets of groups CH and CH2 of lupane framework
are not shown): 0.82 s (3H, Me), 0.83 s (3H, Me), 0.94 s
(3H, Me), 1.01 s (3H, Me), 1.23 t (3H, CH3CH2O,
J 6.9 Hz), 1.38 s (3H, Me), 2.03 s (3H, MeC=O), 2.06 s
(3H, MeC=O), 2.26 m (1H, H19), 3.71 q (2H, CH3CH2O,
J 6.9 Hz), 3.72 d (1H, H28, J 11.4 Hz), 4.24 d (1H, H28,
J 11.4 Hz), 4.45 m (1H, H3), 4.77 s (1H, H29), 4.92 d
(1H, H30, J 16.2 Hz), 4.99 d (1H, H30, J 16.2 Hz), 5.13
s (1H, H29), 5.61 s (2H, CH2Ph), 7.12 m (1HHt), 7.20 t
(1HHt), 7.40 m (3H, Ph), 7.47 m (2H, Ph), 10.81 s (1H,
NCH=N). 13C NMR spectrum, δ, ppm: 14.70, 15.75,
15.88, 16.22, 17.85, 20.59, 20.78, 21.06, 23.39, 26.62,
27.05, 27.68, 29.39, 31.21, 33.83, 33.94, 36.75, 36.97,
37.49, 38.13, 40.59, 42.37, 43.03, 46.10, 49.85, 53.06,
54.18, 55.04, 61.95, 80.61, 112.80, 122.09, 122.31,
128.75, 129.14, 133.07, 137.10, 147.80, 170.76 (C=O),
170.21 (C=O). Found, %: C 64.49; H 7.60; N 3.77.
C44H63BrN2O4·C2H5OH·2H2O. Calculated, %: C 65.04;
H 8.49; N 3.37.
3-[3,28-Diacetoxylup-20(29)-en-30-yl]-1-
(2,6-dimethylphenyl)-1H-imidazol-3-olium
bromide·C2H5OH (IIIi). Yield 56%. Light-yellow crys-
tals, mp 156.5°C, Rf 0.37, [α]D25 +6.6 (c 0.5, CHCl3). IR
spectrum, cm–1 (mull in mineral oil): 3381 br (OH), 1734,
1
1550 w, 1239, 1102 w, 1029, 977, 781, 747. H NMR
spectrum, δ, ppm (multiplets of groups CH and CH2
of lupane framework are not shown): 0.77 s (3H, Me),
0.78 s (3H, Me), 0.94 s (3H, Me), 0.97 s (3H, Me), 1.17 t
(3H, CH3CH2O, J 6.9 Hz), 1.33 s (3H, Me), 1.96 s (3H,
MeC=O), 2.00 s (3H, MeC=O), 2.09 s (3H, MeAr), 2.11 s
(3H, MeAr), 2.33 m (1H, H19), 3.65 q (2H, CH3CH2O,
3-[3,28-Diacetoxylup-20(29)-en-30-yl]-1-phenyl-
1H-imidazol-3-olium bromide·C2H5OH·1.5H2O (IIIg).
Yield 47%. Light-yellow crystals, mp 155.8°C, Rf 0.45, IR
spectrum, cm–1 (from thin film): 3412 br.w (OH), 2944,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 5 2012

N-HETEROCYCLIC CARBENES: V.
703
J 6.9 Hz), 3.72 d (1H, H28, J 10.8 Hz), 4.19 d (1H, H28,
J 10.8 Hz), 4.40 m (1H, H3), 4.73 s (1H, H29), 5.08 s
(1H, H29), 5.29 d (1H, H30, J 15.0 Hz), 5.40 d (1H, H30,
J 15.0 Hz), 7.08–7.47 m (5H, 2HHt + 3Harom), 10.48 s
(1H, NCH=N). 13C NMR spectrum, δ, ppm: 14.65, 15.97,
16.30, 17.21, 17.59, 17.66, 17.95, 20.74, 20.84, 21.12,
23.47, 26.76, 27.16, 27.76, 29.48, 31.47, 33.90, 34.06,
36.86, 37.17, 37.58, 38.21, 40.71, 42.52, 43.31, 46.26,
49.93, 54.38, 55.14, 61.99, 80.71, 111.96, 122.92, 123.46,
128.28, 129.09, 130.91, 132.95, 134.54, 135.38, 138.34,
148.79, 170.82 (C=O), 171.22 (C=O). Found, %: C 67.93;
H 7.92; N 3.95. C45H65BrN2O4·C2H5OH. Calculated, %:
C 68.51; H 8.69; N 3.40.
target program “Research and Development in priority
directions of the scientific and technical complex of Rus-
sia for 2007–2013,” State contract no. 11.519.11.2033.
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ACKNOWLEDGMENTS
The authors express their gratitude to Senior Research-
er V.I. Karmanov for registering IR spectra, to Researcher
E.V. Baigacheva for performing the elemental analyses.
The study was carried out under the financial support
of the Russian Foundation for Basic Research (grant
no. 09-03-00841-a), of Presidium of the Russian Acad-
emy of Sciences (program no. 09-P-3-1016) and Federal
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