Catalytic epoxidation of β-pinene with aqueous hydrogen peroxide

Article abstract of DOI:10.1134/S1070363217080059

Epoxidation of β-pinene with 35–38% aqueous hydrogen peroxide in a new catalytic system containing manganese sulfate, salicylic acid, sodium bicarbonate and polar solvent (DMF, acetonitrile, methanol) is described. The method of quantitavive determination of β-pinene and its epoxide is developed.

Full text of DOI:10.1134/S1070363217080059

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 8, pp. 1675–1679. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © V.V. Fomenko, О.V. Bakhvalov, V.F. Kollegov, N.F. Salakhutdinov, 2017, published in Zhurnal Obshchei Khimii, 2017, Vol. 87,
No. 8, pp. 1260–1265.
Catalytic Epoxidation of β-Pinene
with Aqueous Hydrogen Peroxide
V. V. Fomenko*, О. V. Bakhvalov, V. F. Kollegov, and N. F. Salakhutdinov
N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences,
pr. Akademika Lavrent’eva, 9, Novosibirsk, 630090 Russia
*е-mail: fomenko@nioch.nsc.ru
Received May 5, 2017
Abstract—Epoxidation of β-pinene with 35–38% aqueous hydrogen peroxide in a new catalytic system
containing manganese sulfate, salicylic acid, sodium bicarbonate and polar solvent (DMF, acetonitrile,
methanol) is described. The method of quantitavive determination of β-pinene and its epoxide is developed.
Keywords: epoxidation, β-pinene, epoxide of β-pinene, aqueous hydrogen peroxide
DOI: 10.1134/S1070363217080059
Epoxidation of terpenes is one of most important
methods of their utilization for the preparation of
various functionalized compounds. β-Pinene 1 belongs
to difficultly epoxidized olefins [1], but its epoxide 2 is
very reactive. Epoxide 2 can be used for preparation of
intermediate compounds for the synthesis of various
fragrance compounds and pharmaceuticals [2, 3], as
well as of low-calories sweeteners [4]. Another promis-
ing way of the use of epoxide 2 is its isomerization to
perill alcohol, which was shown to be capable of
suppressing the growth of tumors [5, 6].
double bond with the formation of spiroepoxides (as in
the case of β-pinene 1) are rare.
Experimental and computational methods have
shown diverse reactivity of β-pinene 1 in oxidation
reactions, in which up to nine major products can be
formed [8]. The difficulties in carrying out epoxidation
in selective manner were also mentioned [9–11]. We
believe that in order to increase the selectivity of trans-
formations it is necessary to use an active catalytic
system and to perform the reaction in an alkaline
medium to prevent possible acid-catalyzed rearrange-
ments with the opening of both the pinane and epoxide
rings. Besides, taking into account the practical value
of β-pinene epoxide 2, it is desirable to use simple,
commercially available, and nontoxic reagents. The
analysis of the literature [7] revealed that in epoxida-
tion in water-containing reaction medium pretty good
results were obtained with the mixture of NaHCO3 and
manganese salts. It is also desirable that polar organic
solvent was mixable with water, that would allow to
avoid the use of surface active compounds for phase-
transfer of β-pinene 1.
Epoxidation of a series of terpenes was described in
detail in our review [7]; here we only note that, as an
oxidant, organic peracids or tert-butylhydroperoxide
are used. In view of relatively high cost and danger, in
recent time, growing attention is drawn to oxidation
with 35–38% aqueous hydrogen peroxide. This
oxidant is readily available, ecologically safe, prac-
tically wasteless, and the number of publications on its
use for epoxidation of olefins has grown sharply in the
last decade. Noteworthy is a clear trend: the lower is
the reactivity of the olefin the fewer is the number of
publications in which it is mentioned. Thus, while
epoxidation of cyclohexene and cyclooctene is widely
discussed in the literature, there are much less pub-
lications on epoxidation of terminal olefins, and even
less, on the spatially hindered α-pinene. For the latter,
a low reactivity is usually mentioned, low conversion
of the terpene, and low yield of the epoxide; the
examples of successful epoxidation of the exocyclic
We have investigated methanol, DMF, acetonitrile
as solvents and found that the addition of salicylic acid
to the catalytic system substantially accelerates the
process and allows to reach the desirable result
(Scheme 1).
For unbiased estimation of the results of investiga-
tion, a reliable quantitative analytical method was
1675

1676
FOMENKO et al.
tially exceeded the content of epoxide 2. Careful
Scheme 1.
purification of injector and changing the column did
not change the situation. This allowed an assumption
that thermal isomerization occurred and, indeed, for
different temperatures of injector and temperature
regime of the column oven we obtained different
compositions of the mixtures. Obviously, such a
method of quantitative analysis of epoxide 2 cannot be
considered as acceptable.
9
7
8
H2O2
5
6
4
2
NaHCO3, MnSO4
salicylic acid
3
1
10
MeCN, DMF or MeOH
O
2
1
required both for the starting β-pinene 1 and for the
formed epoxide 2. Most widely used for analysis of the
epoxide concentration in mixtures is the method of
determining the epoxide number. We have examined
this method for the analysis of the β-pinene epoxide 2
content. For this, we have synthesized an authentic
sample of the β-pinene epoxide [12], and the reaction
mixtures obtained in the course of working out the
method of epoxidation of β-pinene 1 with aqueous
hydrogen peroxide. It turned out that on the same
example this method gave a dispersion of 15–20%. An
attempt to increase the accuracy of determination of
epoxide 2 content by a themperature control of the
reaction vessel, variation of the rate of stirring and the
rate of addition of hydrochloric acid to epoxide 2 was
unsuccessful. Apparently, this was connected with
extremely high lability of β-pinene epoxide 2 in acidic
media. The method of determination of the epoxide
number was elaborated for non-hindered epoxides, like
1,2-epoxide of dipentene or short-chain epoxides used
in the synthesis of epoxide resins rather than for spiro-
epoxides, as in the case of epoxide 2. A high reactivity
of epoxide 2 may result in simultaneous occurring of
competitive reactions of hydrohalogena-tion and acid-
catalyzed rearrangements, leading to alcohols and
aldehydes, which do not react with hydrochloric acid.
Evidently, the predominance of a specific mechanism
crucially depends on local concentration of hydro-
chloric acid and does not allow making hydrochlorina-
tion of β-pinene epoxide 2 well reproducible.
Quantitative analysis of β-pinene 1 and epoxide 2
by HPLC on capped inverse-phase sorbents, in spite of
the absence of isomerization, is hampered by small
extinction coefficients of the compounds. Moreover, to
reduce the error of determination, it is necessary to use
large specimens, of several grams, since compounds 1
and 2 are rather volatile and in preparation of samples
for HPLC a part of the sample is evaporated. It is also
important that one of the products of isomerization of
β-pinene epoxide 2, peril alcohol, on the one hand, has
retention time close to that of epoxide 2 and in its
presence the chromatographic peaks cannot be pro-
perly integrated, and, on the other hand, the spectral
characteristics of the two compounds are similar and
multiwave detection not always allows for reliable
discrimination between them. Therefore, in some cases
HPLC analysis may give methodological error, which
is difficult to detect. Based on the above, we came to
the conclusion that it is very difficult to elaborate
reliable quantitative HPLC method for determination
of β-pinene epoxide 2 content.
NMR method is a direct physical method of
investigation. We have detected a number of non-
overlapping signals in the 1H NMR spectra of β-pinene
1 and its epoxide 2: methyl groups at 0.7–1.4 ppm, AB-
doublet of methylene group protons of epoxide 2 at
2.68 ppm, olefin protons of β-pinene 1 at 4.5 ppm. The
methyl groups signals have small width, so, they are
attractive for quantitative NMR method of analysis.
However, for reaction mixtures, in this field wide
signals of admixtures can appear, which reduce the
accuracy of determination of the olefin/epoxide ratio.
Still, it is worth mentioning, that in the absence of
extraneous signals, the integration of the methyl
groups signals is the best method for quality control of
β-pinene epoxide 2 and the determination of traces of
β-pinene 1 with high accuracy.
In the review on epoxidation of terpenes [7] it was
mentioned that the GC method is widely used for the
analysis of epoxides; it was employed also in later
works [9–11, 13]. Good analytical results were
obtained for unstrained epoxides. We performed the
analysis of epoxide 2 using the method of chromato-
mass spectrometry. To our surprise, in pure authentic
sample of β-pinene epoxide 2 a large amount of admix-
1
tures was found, which were not detected in H NMR
Based on the above, we proposed to use for
determination of relative amount of β-pinene epoxide 2
and β-pinene 1 the signals of the methylene group
spectra, namely: mirtenol, mirtenal, mirtanal, peril
alcohol, etc., the total amount of admixtures substan-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

CATALYTIC EPOXIDATION OF β-PINENE
1677
protons in epoxide 2 at 2.68 ppm, and the protons at
the double bond in β-pinene 1 at 4.5 ppm. It should be
mentioned that for quantitative analysis using NMR
method careful tuning of the spectrometer and
correction of the base line, as well as the pulse decay
time for complete relaxation of nuclei (in our case, 10 s)
are necessary. The 1 : 2 ratio was calculated from the
ratio of integral intensities of the signal of β-pinene 1
at 4.5 ppm (2Н) and the low-field signal of one of
protons of the ОСН2 group of epoxide 2 (1Н).
petroleum ether, NefRas solvent, or hexane, the extract
was concentrated and β-pinene epoxide 2 was isolated
by vacuum distillation. The structure of the obtained
1
compounds was determined by the analysis of Н and
13С NMR spectra, including 2D{1Н–1Н} and J-modula-
tion spectra, as well as by comparing the spectra with
those described earlier in the literature [12].
The novelty of the proposed method for preparation
of β-pinene epoxide 2 consist in that the formation of
the oxirane ring in a difficultly epoxidized compound
is achieved by the use of simple, cheap, commercially
available, and nontoxic reagents, as well as by the use
of catalytic system, which was not earlier described for
epoxidation of pinenes.
After determination of molar ratio β-pinene/β-
pinene epoxide by the method of NMR spectroscopy,
the content of β-pinene 1 and β-pinene epoxide 2 in the
mixture was quantitatively determined by the GC
method using internal standard. To exclude possible
artefacts described for the analysis of epoxide 2 by the
GC-MS method (vide supra), we recorded chromato-
grams at different temperatures of the injector and
column. It turned out that in the temperature interval
150–280°С no isomerization of β-pinene 1 or its other
transformations occur. The choice of the internal
standard for calibration was made taking into account
the necessity of its high purity, availability and, most
important, its retention time, which must be close to
that of β-pinene 1, but the peaks must be well resolved.
As standards, naphthalene, undecane and mesitylene
(1,3,5-trimethylbenzene) were chosen. The most
successful, in our opinion, is mesitylene (also because
The reaction conditions were optimized and it was
found that the optimal order of mixing of the reagents
was preparation of the cooled solution of hydrogen
peroxide with NaHCO3 and its gradual addition to the
suspension of MnSO4 in the solution of β-pinene 1 and
salicylic acid. If salicylic acid is added to the solution
of hydrogen peroxide or it is excluded from the
reaction mixture, the conversion and the yield sharply
drop. As catalysts, MnCl2 and Mn(OAc)2 were also
tested, but it turned out that they catalyze the reaction
of epoxidation much less effectively; apparently, the
increase in the solubility of the manganese salt is not a
necessary condition for the catalysis. The vigorous
stirring and keeping of optimal temperature of the
reaction mixture are very important. At temperatures
below 15°С the rate of the reaction sharply decreased
and the conversion is reduced, while above 25°С the
formation of side products becomes tangible. Note a
small induction period at the beginning of the reaction
that requires precautions in addition of hydrogen
peroxide, since its excess can lead to overheating of
the reaction mixture and the formation of side
products. In the optimized conditions of epoxidation
the yields of β-pinene epoxide 2 in DMF, acetonitrile,
and methanol are equal to 66, 76, and 22%, respec-
tively. A low yield for the reaction in methanol is due
to a low conversion, but since methanol is a very cheap
solvent, its industrial use may be justified. Taking into
account the practical importance of the results, we
have also investigated the possibility of recuperation of
solvents from the reaction mixtures.
1
it is suitable as an internal quantitative standard in H
NMR spectra due to its singlet signals non-overlapping
with any other signals). For mesitylene, the correction
coefficient of the detector sensitivity with respect to β-
pinene 1 was determined to be 1.15. The solutions of
compounds for GC were prepared in toluene. It should
be noted that the combined use of the NMR and GC
methods for analysis of the experimental mixtures
allows
a more reliable detection of abnormal
proceeding of the epoxidation.
The proposed method is characterized by high
accuracy (the absolute error of determination of the
content of β-pinene epoxide 2 did not exceed 5%) and
reproducibility. Using this method of analysis, we
carried out epoxidation of β-pinene 1 with 35–38%
aqueous hydrogen peroxide by gradual interaction of
β-pinene 1 in a polar solvent (dimethylformamide,
acetonitrile, methanol) with aqueous hydrogen per-
oxide in the presence of catalytic system consisting of
manganese sulfate, sodium bicarbonate, and salicylic
acid. β-Pinene epoxide 2 and unreacted β-pinene 1
were extracted from the reaction mixture with
Therefore, we have worked out quantitative tandem
NMR–GC method for determination of content of
β-pinene 1 and its epoxide 2 and, using this method,
performed the synthesis of β-pinene epoxide 2. The
optimal way is to carry out the reaction in acetonitrile
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

1678
FOMENKO et al.
medium, with sodium bicarbonate, manganese sulfate,
and salicylic acid by oxidation with 35–38% aqueous
hydrogen peroxide at 18–22°С. Without recuperation
of β-pinene 1 the yield of β-pinene epoxide 2 is 76%.
meter and fitting for supply of liquid was charged at
vigorous stirring with 3.03 g (21.8 mmol) of (−)-β-
pinene 1, 38.5 mL of DMF containing 0.3% of water,
0.066 g (0.44 mmol) of dry MnSO4 and 0.12 g
(0.87 mmol) of salicylic acid. To the reactor, the
cooled mixture of 28.5 mL of 0.4 M solution of
NaHCO3 and 17.0 mL of 38% hydrogen peroxide was
uniformly fed during 2.5 h, keeping the temperature
within 18–22°С, the mixture was stirred for another
15 min, then treated several times with hexane, the
extract was washed with water, dried, the solvent was
removed in a water-jet pump vacuum (~20 mmHg) at a
temperature not exceeding 25°С. Yield 2.52 g (66%).
From the 1H NMR and GC analysis, the crude product
contained 80% of β-pinene epoxide 2. The distilled
solvent containing 0.2% of β-pinene 1 and 0.2% of
epoxide 2, was used for extraction in the next cycle of
the synthesis of epoxide 2.
EXPERIMENTAL
1Н and 13С NMR spectra were registered on a
Bruker DRX-500 spectrometer with working fre-
quency 500.13 (1Н) and 125.76 MHz (13С) for
solutions in CDCl3, using the signals of chloroform as
an internal standard (δH 7.24, δС 76.90 ppm). High-
resolution mass spectra were registered on a DFS
Thermo Scientific mass-spectrometer in the range 0–
500 Da, ionization by electron impact of 70 eV in the
regime of direct admission of the sample. GC analysis
was performed on a 7820A chromatograph (Agilent
Tech., USA) with flame ionization detector and
capillary column HP-5 (0.25 mm × 30 m × 0.25 μm),
gas-carrier helium, flow rate 2 mL/min. Chromato-
mass spectrometry analysis was performed on a Agilent
7890A instrument with quadruple mass detector
Agilent 5975C, quartz column HP-5MS (0.25 mm ×
30 m × 0.25 μm) and HP-5973N chromate-mass spec-
trometer (Agilent Technologies) with HP-5MS column.
Synthesis of β-pinene epoxide 2 in aqueous
acetonitrile. The described above reactor was charged
with 3.04 g (21.9 mmol) of (−)-β-pinene 1, 39 mL of
acetonitrile, 0.067 g (0.44 mmol) of dry MnSO4 and
0.12 g (0.88 mmol) of salicylic acid. In the course of
3 h the cooled mixture of 29 mL of 0.4 M. solution of
NaHCO3 and 19 mL of 35% hydrogen peroxide was
uniformly fed keeping the temperature within 18–22°С,
the mixture was stirred for another 15 min, then
separated. The upper layer was extracted with hexane
distilled in the previous syntheses. The extract was
washed with water and dried, the solvent was removed
in a water-jet pump vacuum (~20 mmHg) at a tem-
perature not exceeding 25°С. Yield 2.11 g (66%),
taking into account the conversion of 74%. From the
NMR and GC data, the content of epoxide 2 was 95%.
The extraction of the starting and the target compounds
from the bottom layer by the same scheme gave
additionally 0.17 g of crude epoxide 2, containing 59%
of the target product, which increases the yield to 76%,
and with taking into account the conversion, to 87%.
Quantitative GC analysis was performed on a HP
5890 Series chromatograph equipped with a katharo-
meter and a capillary column HP-5 of 30 m long,
0.53 mm inner diameter and 2.65 μm thickness of
stationary phase (block copolymer of dimethylpoly-
siloxane and phenylpolysiloxane). Temperature of
injector 300°С, of detector, 280°С, initial temperature
of column 40°С (2 min), heating with the rate 5 deg/min
to 50°С, 10 deg/min to 70°С, 20 deg/min to 280°С, iso-
therm at 280°С, total time of analysis 26.5 min. Gas-
carrier helium, flow rate 5 mL/min, split ratio 10.
In this work we used commercial reagents: (−)-β-
pinene (99%, Aldrich); toluene, acetonitrile, DMF,
methanol, naphthalene, undecane, mesitylene of pure
for analysis grade; hexane of pure grade; manganese
sulfate, acetate and chloride, sodium bicarbonate,
salicylic acid of pure for analysis grade. All solvents
were purified by standard procedures.
Regeneration of DMF and preparation of β-
pinene epoxide 2 using regenerated DMF. 76 g of
the residue after separation of extract from the reaction
mixture from the experiment in DMF was clarified by
centrifugation, from the centrifugate water was
distilled off in a vacuum, the residue was clarified
again by centrifugation to obtain 31 g of liquid which
was used as a solvent for epoxidation of β-pinene 1.
Standard sample of β-pinene epoxide 2 of 99%
1
purity was obtained by the known procedure [12]. Н
NMR spectrum of compound 2 coincided with the
1
earlier published [14]. Н NMR spectrum (CDCl3, δ,
ppm: 0.90 s (3H, С8H3), 1.24 s (3H, С9H3), 2.68 AB
doublet (2H, С10H2, J = 6.0 Hz).
In the reactor described above the epoxidation was
carried out using the charges and conditions of the
experiment in DMF applying as organic solvent the
Synthesis of β-pinene epoxide 2 in aqueous
DMF. Glass reactor with mechanical stirrer, thermo-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

CATALYTIC EPOXIDATION OF β-PINENE
1679
mixture of 20 mL of pure and 20 mL of regenerated
DMF. Hexane was used as an extraction agent. 2.44 g
of slightly colored crude epoxide was obtained
containing, from the H NMR and GC analysis, 40%
of β-pinene epoxide 2, yield 35%.
epoxide 2, 0.9 g of pinene fraction, 6.4 g of epoxide
fraction containing 95% of β-pinene epoxide 2, 3% of
(−)-β-pinene 1 and unidentified products, 0.5 g of a
mixture containing no less than 50% of β-pinene
epoxide 2, and 0.2 g of stillage was obtained. 1H NMR
spectrum of the epoxide fraction corresponds to the
spectrum of β-pinene epoxide 2. The yield of the
product after distillation 95%. The yield to the taken
(−)-β-pinene 1, 56%, taking into account the con-
version, 73%.
1
Regeneration of acetonitrile and preparation of
β-pinene epoxide 2 using regenerated acetonitrile.
68 g of the residue after separation of extract from the
bottom layer from the experiment in acetonitrile was
clarified by centrifugation, the obtained solution (65 g)
was distilled at atmospheric pressure. First fraction
(19 g, bp 75–77°С) is the azeotropic mixture of
acetonitrile and water. Second fraction (36 g) is water.
Stillage (6 g) is brown viscous liquid.
REFERENCES
1. Woitiski, C.B., Kozlov, Yu.N., Mandelli, D., Nizo-
va, G.V., Schuchardt, U., and Shul’pin, G.B., J. Mol.
Catal. A: Chem., 2004, vol. 222, p. 103. doi 10.1016/
j.molcata.2004.08.003
2. De Villa, A.L.P., De Vos, D.E., De Montes, C.C., and
Jacobs, P.A., Tetrahedron Lett., 1998, vol. 39, no. 46,
p. 8521. doi 10.1016/S0040-4039(98)01853-X
3. Fdil, N., Romane, A., Allaoud, S., Karim, A., Castanet, Y.,
and Mortreux, A., J. Mol. Catal. A: Chem., 1996,
vol. 108, p. 15. doi 10.1016/1381-1169(95)00284-7
4. Li, Q.H., Yin, D.L., Xiao, Y., and Duan, C.S., Yingyong-
huaxue (Chinese J. Appl. Chem.), 2000, vol. 5, p. 17.
doi 10.3969/j.issn.1000-0518.2000.05.019
5. De Oliveira, B.H. and Strapasson, R.A., Braz. Arch.
Biol. Technol., 2000, vol. 43, p. 11. doi 10.1590/S1516-
89132000000100002
6. Rajesh, D., Stenzel, R.A., and Howard, S.P., J. Biol.
Chem., 2003, vol. 278, p. 35968. doi 10.1074/
jbc.M303280200
The epoxidation in acetonitrile using the mixture of
19.5 mL of acetonitrile and 19.5 mL of the obtained
axeotropic mixture as an organic solvent, was carried
out as described above. After treatment of the reaction
mixture, from the upper layer was isolated 1.59 g and
from the bottom layer, 0.56 g of the crude product.
1
From the H NMR and GC analysis, the content of
β-pinene epoxide 2 in the product from the upper layer
was 94%, from the bottom layer, 59%. Total yield of
β-pinene epoxide 2 was 59%.
Synthesis of β-pinene epoxide 2 in aqueous
methanol. Under the conditions similar to those for
epoxidation in DMF, from 1.88 (13.7 mmol) of (−)-β-
pinene 1, 1.37 g of the crude product was obtained
containing, from the 1H NMR and GC analysis, 30% of
β-pinene epoxide 2. Yield 22%.
7. Bakhvalov, O.V., Fomenko, V.V., and Salakhutdinov, N.F.,
Khim. v Inter. Ust. Razv., 2008, vol. 16, p. 633.
8. Neuenschwander, U., Meier, E., and Hermans, I., Chem.
Sus. Chem., 2011, vol. 4, p. 1613. doi 10.1002/
cssc.201100266
9. Schröder, K., Junge, K., Spannenberg, A., and Beller, M.,
Catal. Today, 2010, vol. 157, p. 364. doi 10.1016/
j.cattod.2010.04.034
10. Da Silva, M.J., Vieira, L.M.M., Oliveira, A.A., and
Ribeiro, M.C., Monatsh. Chem., 2013, vol. 144, p. 321.
doi 10.1007/s00706-012-0875-5
11. Coelho, J.V., Oliveira, L.C.A., Moura, F.C.C., De
Souza, P.P., Silva, C.A., Batistac, K.B., and Da Silva, M.J.,
App. Catal. A: Gen., 2012, vol. 419, p. 215. doi
10.1016/j.apcata.2012.01.032
12. Tatarova, L.E., Korchagina, D.V., Volcho, K.P.,
Salakhutdinov, N.F., and Barkhash, V.A., Russ. J. Org.
Chem., 2003, vol. 39, p. 1076. doi 10.1023/
B:RUJO.0000010173.38389.06
13. Schröder, K., Enthaler, S., Join, B., Junge, K., and
Bellera, M., Adv. Synth. Catal., 2010, vol. 352, p. 1771.
doi 10.1002/adsc.201000091
Vacuum distillation of crude epoxide. A mixture
of crude epoxides synthesized in the above experi-
ments was distilled with a Vigreux column at 5 mm
Hg with a cooled trap. The original mixture contained
12% of (−)-β-pinene 1 and 83% β-pinene epoxide 2.
The fraction of (−)-β-pinene 1 (fraction 1) was distilled
off at the temperature up to 45°С, the fraction of β-
pinene epoxide 2, at the temperature up to 118°С (in
the still) and 60–40°С (in vapor). From 8.8 g of the
original mixture 0.7 g of fraction 1 was obtained
(mainly in the trap), 6.3 g of the target product,
containing 96% of β-pinene epoxide 2, 2% of β-pinene
1
and unidentified compounds, and 0.5 g of stillage. H
NMR spectrum of the target product corresponds to the
spectrum of β-pinene epoxide 2. The yield after
distillation 86%. Total yield with respect to (−)-β-
pinene 1 was 57%.
14. Nikitina, L.E., Dieva, S.A., Plemenkov, V.V., Lodoch-
nikova, O.A., Gubaidullin, A.T., Kataeva, O.N., and
Litvinov, I.A., Russ. J. Gen. Chem., 2001, vol. 71,
p. 1161. doi 10.1023/A:1013251021230
After separation of the combined mixture (9.5 g),
prepared in the experiments similar to those above and
containing 7% of (−)-β-pinene 1 and 65% of β-pinene
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017