Isomerization of methyl (9Z)-12-Oxooctadec-9-enoate

Article abstract of DOI:10.1023/A:1012493010923

Methyl (9Z)-12-oxooctadec-9-enoate isomerizes stereoselectively in 86% yield into methyl (10E)-12-octadec-10-enoate in the presence of a complex H₂O₂-BF₃-Et₂O.

Full text of DOI:10.1023/A:1012493010923

Russian Journal of Organic Chemistry, Vol. 37, No. 6, 2001, pp. 781 783. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 6, 2001,
pp. 829 831.
Original Russian Text Copyright
2001 by Davletbakova, Baibulatova, Dokichev, Yunusova, Yunusov.
Isomerization of Methyl (9Z)-12-Oxooctadec-9-enoate
A. M. Davletbakova, N. Z. Baibulatova, V. A. Dokichev, S. G. Yunusova, and M. S. Yunusov
Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences, Ufa, Bashkortostan, 450054 Russia
Received July 19, 2000
Abstract Methyl (9Z)-12-oxooctadec-9-enoate isomerizes stereoselectively in 86% yield into methyl
(10E)-12-octadec-10-enoate in the presence of a complex H2O2 BF3 Et2O.
The interest to chemical transformations of
ricinoleic [(9Z), (12R)-12-hydroxyoctadec-9-enoic)
acid has grown recently [1, 2]. Its derivatives possess
antiviral, antiphlogistic, and antiallergic properties
[3, 4]. It was shown formerly that the reaction of
methyl (9Z)-12-oxooctadec-9-enoate (I) with peroxy-
acids resulted in epoxydation of the C=C bond [1,
3, 5].
C=C bond from C9 to C10 occurred its selective cis-
trans isomerization as showed the coupling constant
of the vicinal protons attached to the C10= C 11 bond
of enone II ( 16 Hz). Under similar conditions in the
presence of only boron trifluoride etherate the keto-
ester I yielded just 58% of ester II.
The structure of compound II was confirmed by a
known isomerization procedure for ketoester I iso-
merization [7]: refluxing of ether I in ethanol in the
presence of oxalic acid under argon atmosphere.
In the present study during preparation of new
derivatives of ricinoleic acid by oxydation of methyl
(9Z)-12-oxooctadec-9-enoate (I) according to Bayer
Williger procedure we found that the compound
suffered a stereoselective isomerization. Treating of
ethereal solution of enone I with the reagent for
ketone oxidation, a complex of 90% hydrogen per-
oxide and boron trifluoride etherate [6] [molar ratio
ketone I H2O2 BF3 Et20 1: 1: 2], afforded methyl
(10E)-12-octadec-10-enoate (II) in 86% yield. In the
reaction under study alongside the displacement of the
A detailed investigation of ketoester I oxidation
with a 5-foid excess of monoperoxyphthalic or meta-
chloroperoxybenzoic acids revealed that alongside
methyl 12-oxo-9,10-epoxyoctadecanoate III formed
also ketoester II. The yields of compounds III and
II amount respectively to 79 and 14% or 75 and
17%. No products resulting from oxidation of ketone
I along Bayer Williger reaction was detected.
Reagent
Yield of compound II Yield of compound III
90% H2O2, BF3 Et2O
BF3 Et2O
H2C2O4
2-(HO2C)C6H4CO3H
3-ClC6H4CO3H
86
58
41
14
17
79
75
1070-4280/01/3706-0781$25.00 2001 MAIK Nauka/Interperiodica

782
DAVLETBAKOVA et al.
Note that ketoester II stored in air readily under-
described above was obtained 0.17 g (58%) of ketone
II.
goes autooxidation by air oxygen affording methyl
(10E)-9-hydroperoxy-12-oxodec-10-enoate (IV) in
22% yield.
(b) In the presence of oxalic acid. A solution of
0.5 g (1.55 mmol) of ketone I and 0.05 g (0.55 mmol)
of anhydrous oxalic acid in 20 ml of 95% ethanol was
heated under argon for 2 h, then cooled to 20 C, and
the solvent was evaporated in vacuo. The residue was
diluted with 8 ml of Et2O and treated with saturated
solution of Na2CO3 (3 5 ml)the reaction product
was extracted with Et2O, and extract was drid on
MgSO4. The solvent was evaporated in vacuo. We
obtained 0.21 g (41%) of ketone II.
EXPERIMENTAL
1H and 13C NMR spectra were recorded on Bruker
AM-300 spectrometer in CDCl3. IR spectra were
measured on Specord M-80 instrument from samples
as thin films. Mass spectra were taken on spectro-
meter MKh-1300, injection source temperature
100 C, electron ionization energy 70 and 12 eV. The
reaction products were analysed by GLC on Chrom-5
chromatograph, flame-ionization detector, column
1200 5 mm packed with 5% SE-30 on Inerton NAW
DMCS carrier (0.125 0.165 ), carrier gas helium.
Oxidation of ketone I with peroxyacids. (a) To a
solution of 0.46 g (1.5 mmol) of ketone I in 2 ml of
Et2O at 0 C under argon while stirring was added
dropwise a solution of 1.37 g (7.5 mmol) of mono-
peroxyphthalic acid in 7 ml of Et2O, the mixture was
maintained at 0 C for 4 5 h and left standing over-
night at room temperature. The reaction mixture was
filtered, washed with saturated solutions of Na2SO3
(3 5 ml) and Na2CO3 (3 5 ml), and dried with
MgSO4. The solvent was evaporated in vacuo. The
residue was subjected to column chromatography on
silica gel (L 100/250, eluent petroleum ether Et2O,
15: 1). We separated 0.04 g (14%) of ketone II and
0.22 g (79%) of epoxide III.
Methyl (9Z)-12-oxooctadec-9-enoate (I) was pre-
pared by oxidation of methyl (9Z),(12R)-12-hydroxy-
octadec-9-enoate with the Collins reagent [3].
Oxidation of ketone I with H2O2 BF3 Et2O
complex. To a solution of 0.85 g (2.74 mmol) of
ketone I in 0.24 ml of Et2O was added dropwise
under argon at stirring while cooling to 0 C 0.11 g
(2.88 mmol) of 90% H2O2 solution and 0.77 g
(5.48 mmol) of BF3 Et20. The reaction mixture was
maintained at 0 C for 2.5 h, then diluted with 5 ml
of Et2O, washed with saturated solutions of Na2SO3
(3 3 ml) and K2CO3 (3 3 ml), and dried with
MgSO4.
(b) In a similar way 0.5 g (1.6 mmol) of ketone I
dissolved in 2 ml of CH2Cl2 was oxidized with a solu-
tion of 1.4 g (8.1 mmol) of meta-chloroperoxy-
benzoic acid in 7 ml of CH2Cl2. Yield of ketone II
0.07 g (17%), of epoxide III 0.29 g (75%). IR and
1H NMR spectra are consistent with the published
data [1, 3, 5]. 13C NMR spectrum ( C, ppm): 14.06
(C18), 22.51 (C17), 23.58 (C3), 24.91 (C15), 26.43
(C8), 28.00 (C14), 28.84 (C4), 29.04 (C5), 29.17
(C6), 29.29 (C7), 31.61 (C16), 34.06 (C2), 41.63
(C13), 43.36 (C11), 51.51 (CO2_CH3), 52.37 (C10),
56.36 (C9), 174.29 (C1), 208.52 (C12). Mass
spectrum, m/z: 326 [M]+ .
The solvent was removed in vacuo, and the residue
was subjected to column chromatography on silica
gel (L 100/250, eluent petroleum ether Et2O, 20: 1).
Ketone II was separated in 0.73 g amount (86%). IR
1
spectrum (cm ): 1000 (trans-C=C), 1190 (C=O),
1650 (trans-C=C), 1690 (C=O), 3030 (trans-C=C),
1
1745 (CO2). H NMR spectrum ( , ppm, J, Hz): 0.80
t (3H, C18H3, 6.5), 1.13 1.42 m (16H, CH2), 1.45
1.61 m (4H, C3H2, C14H2), 2.12 q (2H, C9H2, 7.2),
2.22 t (2 H, C2H2, 7.6), 2.45 t (2H, C13H2, 7.6),
3.60 s (3H, CO2CH3), 6.02 d (1H, C11H, 16.2), 6.25
d.t (1H, C10H, 15.9 and 6.9). 13C NMR spectrum
Methyl (10E)-9-hydroperoxy-12-oxooctadec-10-
enoate (IV). 4 g (1.3 mmol) of ketone II was stored
in air at room temperature for 1 month. The resulting
mixture was subjected to column chromatography on
silica gel (L 100/250, eluent petroleum ether Et2O,
15: 1). We separated 0.09 g (22%) of hydroperoxide
(
C, ppm): 14.06 (C18), 22.54 (C17), 24.33 (C3),
24.91 (C15), 28.11 (C14), 29.01 (C4), 29.12 (C5, C6,
C7), 29.72 (C8), 31.66 (C16), 32.44 (C9), 34.08
(C2), 40.13 (C13), 51.48 (OCH3), 130.36 (C11),
147.34 (C10), 173.33 (C1), 201.12 (C12). Mass
spectrum, m/z: 310 [M]+ .
1
IV. IR spectrum (cm ): 855 (C O O H), 1050
(trans-C=C), 1190 (CO2), 1645 (trans-C=C),
1690 (C=O), 1745 (CO2), 3030 (trans-C=C), 3425
1
(C O O H). H NMR spectrum ( , ppm, J, Hz): 0.83
Isomerization of ketone I. (a) In the presence of
BF3 Et20. From 0.3 g (0.97 mmol) of ketone I and
0.275 g (1.94 mmol) of BF3 Et20 along procedure
t (3H, C18H3, 6.6), 1.15 1.41 m (16H, CH2), 1.42
1.65 m (4H, C3H2, C14H2), 2.23 t (2H, C2H2, 7.5),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 6 2001

ISOMERIZATION OF METHYL (9Z)-12-OXOOCTADEC-9-ENOATE
2.52 t (2H, C13H2, 7.4), 3.6 s (3H, CO2CH3), 3.7 m
783
no. 5, pp. 601 607.
(1H, OH), 4.43 m (1H, C9H), 6.22 d (1H, C11H,
16.2), 6.70 d.d (1H, C10H, 15.9 and 6.6). 13C NMR
spectrum ( C, ppm): 13.96 (C18), 22.44 (C17), 23.72
(C3), 24.45 (C7), 24.72 (C14), 27.42 (C15), 28.81
(C4, C6), 29.18 (C5), 31.43 (C16), 33.98 (C2), 35.20
(C8), 40.35 (C13), 51.39 (OCH3), 84.58 (C9), 130.72
(S11), 144.57 (S10), 174.29 (S1), 200.50 (S12).
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pp. 34 40.
3. Zabolotskii, D.A. and Myagkova, G.I., Bioorg. khi-
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1975, vol. 14, no. 23, pp. 5021 5023.
5. Lie Ken Jie, M.S.F. and Zheng, Y.F., Synthesis, 1988,
no. 6, pp. 467 468.
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