Transformations of several monoterpenoids in the presence of aldehydes in supercritical solvents

Article abstract of DOI:10.1134/S0036024413030023

The reactivity of verbenol epoxide and isopulegol in supercritical solvents in the presence of aromatic aldehydes was studied using a flow type reactor and a heterogeneous catalyst (Al₂O₃) or no catalyst. The intramolecular transformations or interactions of reagents with the solvent prevailed in all cases; the yield of the products of intermolecular reactions of terpenoids with aldehydes was up to 1%. The aldehydes did not interact with verbenol epoxide but produced a considerable effect on the distribution of its isomerization products.

Full text of DOI:10.1134/S0036024413030023

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2013, Vol. 87, No. 3, pp. 382–387. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.I. Anikeev, V.P. Sivcev, I.V. Il’ina, D.V. Korchagina, O.B. Statsenko, K.P. Volcho, N.F. Salakhutdinov, 2013, published in Zhurnal Fizicheskoi Khimii,
2013, Vol. 87, No. 3, pp. 403–408.
CHEMICAL KINETICS
AND CATALYSIS
Transformations of Several Monoterpenoids
in the Presence of Aldehydes in Supercritical Solvents
V. I. Anikeeva, V. P. Sivcevb, I. V. Il’inac, D. V. Korchaginac,
O. B. Statsenkoc, K. P. Volchoc, and N. F. Salakhutdinovc
aBoreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
bNovosibirsk State University, Novosibirsk, Russia
cVorozhtsov Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
eꢀmail: anik@catalysis.ru
Received February 3, 2012
Abstract—The reactivity of verbenol epoxide and isopulegol in supercritical solvents in the presence of aroꢀ
matic aldehydes was studied using a flow type reactor and a heterogeneous catalyst (Al2O3) or no catalyst. The
intramolecular transformations or interactions of reagents with the solvent prevailed in all cases; the yield of
the products of intermolecular reactions of terpenoids with aldehydes was up to 1%. The aldehydes did not
interact with verbenol epoxide but produced a considerable effect on the distribution of its isomerization
products.
Keywords: supercritical solvent, terpenoids, verbenol epoxide, isopulegol, aldehydes, alumina.
DOI: 10.1134/S0036024413030023
INTRODUCTION
with frameworks of various types [9–14]. The goal of
this study, therefore, was to investigate the possibility
of reactions of monoterpenoids with aldehydes in SCF
in a flow type reactor.
Due to their unique properties, supercritical fluids
(SCFs) are attractive solvents for performing many
chemical reactions and serve as a basis for new techꢀ
nologies. For example, using a supercritical fluid as a
reaction medium leads to a substantial increase in the
rate of the thermal isomerization of monoterpenes [1]
and produces a considerable effect on the route of the
intramolecular transformations of labile monoterpeꢀ
EXPERIMENTAL
The reagents used for this study included benzaldeꢀ
hyde (11),
3,4,5ꢀtrimethoxybenzaldehyde (14), (–)ꢀisopulegol
) (Aldrich), Al2O3 (Macherey–Nagel, pH 0.5
50–200 m, free surface according to BET
~130 m2/g). Verbenol epoxide (
) was synthesized
pꢀfluorobenzaldehyde (4), vaniline (9),
noids: ꢀpinene [2], verbenone [3], and verbenol [4]
α
(
2
7
,
epoxides. Recently, it was shown that using a combiꢀ
nation of an SCF and a heterogeneous catalyst allowed
various transformations of natural organic comꢀ
pounds: isomerization [5], Meerwein–Ponndorf–
Verley reduction [5, 6], oxidation with air oxygen [7],
and intramolecular cyclization of citronellal
ulegol [8]:
μ
3
from (–)ꢀverbenone (Aldrich) by the procedures of
[10, 15]. The experimental studies of reactions in a
supercritical solvent were performed on a laboratory
unit described in detail in [2, 8] using a tube reactor
with a length of 6 m and an inner diameter of 1.75 mm
(reactor volume 14.4 cm3) or a similar tube reactor
1 to isopꢀ
2
containing 22.1 cm3 (20.6 g) of granulated Al2O3
.
The reaction mixture was fed to the reactor in two
flows. The first flow (supercritical СО2) was introꢀ
duced with a syringe pump through a heat exchanger,
where it was heated to the reaction temperature, to a
mixer situated at the inlet of the reactor. The second
flow (1% solution of reagents for each component in a
corresponding organic solvent) was supplied to the
same mixer with a piston pump.
scꢀCO /hexane, 160°C
2
CHO
Al O
2
3
OH
(1)
(2)
Scheme 1.
The possibility of intermolecular reactions of terpeꢀ
noids with aldehydes in SCFs, however, remained
The reaction mixture was cooled at the outlet of the
completely uninvestigated; under the normal condiꢀ reactor and forwarded to analysis. The composition of
tions they lead to various heterocyclic compounds the liquid reaction products was analyzed by chroꢀ
382

TRANSFORMATIONS OF SEVERAL MONOTERPENOIDS
383
matoꢀmass spectrometry on an Agilent 7890A chroꢀ (2R,7R,8aR)ꢀ4,7ꢀdimethylꢀ2ꢀ(3,4,5ꢀtrimethoxypheꢀ
matograph with an Agilent 5975C quadrupole mass nyl)ꢀ3,5,6,7,8,8aꢀhexahydroꢀ2
analyzer as a detector. For analysis we used an HPꢀ (0.109 g, 5%).
5MS quartz column (5%ꢀdiphenyl–95%ꢀdimethylsiꢀ
H
ꢀchromene
(17)
Compound 15a. 1H NMR spectrum,
δ
, ppm: 0.93 d
2J
J8а, 7а
12.8, J8а, 7е = 3.0 Hz); 1.04 dddd (Н7а 2J
7а, 8а = 12.8 ,
J7а, 8е = 3.2 Hz); 1.13 ddd (Н10а
(
С18Н3
,
=
=
J18,9 = 6.6 Hz); 0.93 dddd (Н8а
,
=
=
=
loxane copolymer, length 30 m, inner diameter
0.25 mm, and film thickness of the stationary phase
0.25 m). Scanning at m/z = 29–500. The qualitative
J8а, 9а
J7а, 6а
,
μ
J
,
2J = 12.5, J10а, 9а = 12.5, J10а, 1а = 11.0 Hz); 1.29 s
analysis was performed by comparing the retention
times of components and their total mass spectra with
the corresponding data for pure substances if they were
available or with the data of NIST 2.0 and Wiley 7
databases. The composition of the mixtures was calcuꢀ
lated from the peak areas in the chromatograms withꢀ
out using any correcting coefficients.
(
С17Н3); 1.31 ddd (Н6а
J6а, 7е = 3.0 Hz); 1.40–1.51 m (Н9а); 1.73 dm (Н8е
2J = 12.8 Hz); 1.76 dd (Н4а 2J = 12.8, J4а, 3а
11.7 Hz); 1.89 dd (Н4е 2J = 12.8, J4е, 3а = 2.0 Hz);
1.94 dddd (Н7е 2J = 12.8, J7е, 6а
3.0 Hz); 2.01 dddd (Н10е 2J = 12.5, J10е, 1а
, J6а, 7а = 12.8, J6а, 1а = 10.0,
,
=
,
,
,
=
J7е, 8а
=
=
J7е, 8е
J10е, 9а
=
=
,
The contact time (
calculated as the ratio of the catalyst volume in the J1а, 6а = 10.0, J1а, 10е = 4.2 Hz); 3.79 s (С20Н3); 3.84 s
reactor Vc (cm3) (reactor volume without a catalyst) to С19Н3); 4.35 dd (Н3а
J3а, 4а = 11.7, J3а, 4е = 2.0 Hz);
the total consumption of the mixture at the inlet of the 6.56 s (Н12, Н16). 13С NMR spectrum,
, ppm: 77.45 d
reactor ~ 4.5 min.
(cm3/s); for a flow of 5 mL/min, С1); 76.65 d (С3); 49.86 t (С4); 70.82 s (С5); 51.94 d
The transformations were performed at temperatures (С6), 22.96 (С7); 34.29 t (С8), 31.38 (С9); 41.41 t
= 60–245 and pressures
= 145–230 atm. The (С10); 137.73 s (С11); 103.17 d (С12, С16); 153.10 s
temperature and pressure that provide the supercritiꢀ (С13, С15); 137.31 s (С14); 21.28 q (С17); 22.08 q (С18)
τ
) of the reaction mixture was 4.2, J10е, 8е = 1.5 Hz); 3.25 ddd (Н1а
,
J1а, 10а = 11.0,
(
,
δ
Q
τ
(
t
d
T
°C
Р
;
cal conditions of the reaction mixture were chosen on 55.98 q (С19, С21); 60.64 q (C20). Found
the basis of thermodynamic calculations and phase 350.2084. С20Н30О5. Calcd. 350.2088
diagram construction.
[M]
+
М
.
Compound 15b. The NMR spectral data for isomer
1
13
The H and C NMR spectra were recorded on a 15b were obtained from the spectra recorded for the
Bruker DRXꢀ500 spectrometer (operating frequencies 1.0 : 0.25 mixture of 15a and 15b. The signals of several
500.13 MHz for H and 125.76 MHz for 13C) for protons that overlap the signals of the main isomer,
1
CDCl3 solutions of the substances. The chloroform therefore, were not isolated in the 1H NMR spectrum
1
solvent was used as an internal standard (δH = 7.24, of 15b. H NMR spectrum,
δ
, ppm: 0.92 d (С18Н3
,
,
δС = 76.90 ppm). The structure of the obtained comꢀ J18,9 = 6.6 Hz); 0.88–0.98 m (Н8а); 1.03–1.23 m (Н7а
pounds was determined by analyzing the H NMR Н10а
spectra using the 1Н–1Н double resonance spectra and (H4a, 2
by analyzing the 13C NMR spectra recorded in a 1.78–1.83 m (Н7е); 1.80 dd (Н4е
ꢀmodulation mode (JMOD) with offꢀresonance proꢀ 2.3 Hz); 1.96–2.02 m (Н10е); 3.54 ddd (Н1а
,
Н6а); 1.21 s (С17Н3); 1.39–1.51 m (Н9а); 1.66 dd
1
J
= 13.7, J4а, 3а = 11.7 Hz); 1.69–1.73 m (Н8е);
,
2J = 13.7, J4е, 3а
J1а, 10а
=
=
J
,
ton suppression and 13С–1Н twoꢀdimensional correlaꢀ 11.0, J1а, 6а = 9.5, J1а, 10е = 4.2 Hz); 3.77 s (С20Н3);
tion spectra on direct constants (C–H COSY, 1JС, Н
160 Hz). The highꢀresolution mass spectra were 2.3 Hz); 6.57 s (Н12, Н16). 13С NMR spectrum,
recorded on a DFS Thermo Scientific spectrometer in ppm: 75.53 d (С1); 74.79 d (С3); 48.02 t (С4); 69.38 s
a magnetic scanning mode at
= 15–500 with elecꢀ (С5); 49.31 d (С6); 22.40 t (С7); 34.32 t (С8); 31.16 d
tron impact ionization (70 eV) during the direct introꢀ (С9); 41.19 t (С10); 138.48 s (С11); 102.97 d (С12, С16)
=
3.82 s (C19H3, C21H3); 4.69 dd (H3a, J3а, 4а = 11.7, J3а, 4е
=
δ
,
m/z
;
duction of the sample.
Interaction of (–)ꢀisopulegol (2) with 3,4,5ꢀtriꢀ
methoxybenzaldehyde (14) in the presence of clay Kꢀ10.
153.01 s (С13, С15); 137.00 s (С14); 28.11 q (С17), 22.11
к (С18), 60.58 q (С20); 55.91 q (С19, С21).
Compound 16. The NMR spectra of compounds 16
3,4,5ꢀTrimethoxybenzaldehyde (14) (0.99 g) and and 17 were recorded for their mixture in a ratio of
1
isopulegol (
clay Kꢀ10 (4.0 g) preliminarily calcinated at 105
3 h in СН2Cl2 (60 mL). The mixture was stirred for 1 h J8а, 9а = 12.0, J8а, 7е = 3.5 Hz); 1.21 ddd (Н10а
at room temperature. Then EtOAc (15 mL) was added. J10а, 9а = 12.5, J10а, 1а = 11.0 Hz); 1.26 dddd (Н7а
2
) (1.27 g) were added to a suspension of 1.0 : 0.8. H NMR spectrum,
δ
, ppm: 0.94 d (С18Н3
,
°C
for J18,9 = 6.6 Hz); 1.00 dddd (Н8а
,
2J
=
J8а, 7а = 13.5,
,
,
2J
=
=
2J
The catalyst was filtered off, the solvent distilled off, J7а, 8а = 13.5, J7а, 6а = 12.0, J7а, 8е = 3.5 Hz); 1.43–
and the residue separated on a silica gel column (9 g) 1.53 m (Н9а); 1.74 dm (Н8е, 2J = 13.0 Hz); 1.79–
(60–200
roform gradient from 0 to 100% as an eluent). This J7е, 8а
gave ,4a ,7 ,8a
)ꢀ4,7ꢀdimethylꢀ2ꢀ(3,4,5ꢀtriꢀ (H4a, 2J = 13.2, J4а, 3а = 11.4 Hz); 2.45 dd (Н4е
methoxyphenyl)octahydroꢀ2 J1а, 10а = 11.0,
ꢀchromenꢀ4ꢀol 15a,b 13.2, J4е, 3а = 2.4 Hz); 3.09 ddd (Н1а
(0.483 g, 22%) (a mixture of 4 ꢀ(15a) and 4
ꢀ(15b)ꢀ J1а, 6а = 10.0, J1а, 10е = 4.0 Hz); 3.79 s (С20Н3); 3.85 s
isomers in a ratio of 3.4 : 1); (2 ,4a ,7 ,8a
)ꢀ7ꢀ (C19H3, C21H3); 4.30 dd (H3a, J4а, 3а = 11.4, J3а, 4е
methylꢀ4ꢀmethyleneꢀ2ꢀ(3,4,5ꢀtrimethoxyphenyl)octaꢀ 2.4 Hz); 4.66 m and 4.78 m (2H17, all
< 1.5 Hz);
hydroꢀ2 , ppm: 81.89 d
ꢀchromene (16) 0.166 g, 8%); and 6.58 s (Н12, Н16). 13С NMR spectrum,
μ
m, Macherey–Nagel) (hexane with a chloꢀ 1.86 m (Н6а); 1.88 dddd (Н7е 2J = 13.0, J7е, 6а
, =
=
J7е, 8е = 3.2 Hz); 1.97–2.03 m (Н10е); 2.34 dd
2J
(2
R
R
R
R
,
=
H
S
,
R
R
S
R
R
=
J
H
δ
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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384
ANIKEEV et al.
Table 1. Transformations of verbenol epoxide
3
in the presence of aldehydes 4 and 9
Content of mixture components, %
Converꢀ
3
No.
Aldehyde
T,
°
C
Р, atm
other
products
sion of
5
6
7
8, 10
1 [4]
–
197
220
260
175
220
220
220
220
170
100
70.5
99.0
55.0
92.8
100
100
100
30.5
23.3
2.8
–
43.4
2
3
4
5
6
7
8
4
26.4 (37.4) 11.6 (16.5) 3.8 (5.4)
37.3 14.8 4.3
0
0
0
28.7 (40.7)
42.6
9
11.0 (20.0) 12.6 (22.9) 1.4 (2.5)
17.4 (18.7) 22.7 (24.5) 3.0 (3.2)
30.0 (54.5)
0.9 (1.0) 48.9 (52.7)
180
200
230
26.0
28.4
31.6
22.3
21.3
22.5
4.5
5.0
5.6
0.9
0.4
0
46.3
44.9
40.3
Note: The contents of the mixture components (GLC–MS data) are given without regard for the contents of aldehydes 4 or 9. The ratio of
the mixture/CO flows = 1/4. According to [4], the reaction was performed in the absence of an aldehyde. The selectivity is indicated
2
in parentheses.
(
С1); 44.30 t (С4); 148.02 s (С55); 46.30 d (С6); 25.95 t
The axial orientation of Н1, Н3, and H9 in all comꢀ
pounds under study and of H6 in 15a
15b, and 16 follows
from the vicinal constants of their spinꢀspin coupling
with the neighboring hydrogen atoms (all 10 Hz).
(С7); 34.01 t (С8); 31.33 d (С9); 41.33 t (С10); 138.01 s
(С11); 103.01 d (С12, С16); 153.05 s (С13, С15); 137.08 s
,
(С14); 105.57 t (С17); 22.10 q (С18); 55.93 q (С19, С21)
;
J
≥
60.58 q (C20). Found
332.1982
[M
]+ 332.1983. С20Н28О4. Calcd.
М
.
RESULTS AND DISCUSSION
1
Compound 17. H NMR spectrum,
0.94 m (Н8а); 0.93 d (С18Н3
J18,9 = 6.6 Hz); 1.06 ddd
J10а, 1а = 12.0 Hz); 1.55–1.65 m
Н9а); 1.63–1.72 m (Н7а Н8е); 1.67 br.s. (С17Н3);
2J = 12.0 Hz);
δ
, ppm: 0.85–
For the first stage of transformations, as a solvent
we used a CO2–isopropanol mixture, which was sucꢀ
cessfully used for isomerization of monoterpenoid
epoxides [2–4]. Using supercritical CO2 as a compoꢀ
nent of a complex solvent allows one to considerably
lower the critical temperature of the mixture, thus
avoiding undesirable secondary thermal transformaꢀ
tions of the reaction products.
,
(
(
Н10а 2J
, = J10а, 9а =
,
1.97–2.04 m (Н4е), 2.11 dm (Н10е
,
2.29–2.35 m (H4a), 2.68–2.74 m (Н7е); 3.79 s (С20Н3);
3.84 s (C19H3, C21H3); 4.11 br.d. (Н1а
J1а, 10а = 12.0 Hz);
4.44 dd (H3a, J3а, 4а = 10.8, J3а, 4е = 3.0 Hz); 6.59 s (Н12,
,
Н16). 13С NMR spectrum, , ppm: 76.29 d (С1);
δ
As a test reaction, we chose the interaction of verꢀ
75.23 d (С3); 39.23 t (С4); 121.76 s (С5); 131.29 s (С6)
26.34 t (С7); 34.90 t (С8); 30.82 d (С9); 42.61 t (С10)
138.50 s (С11); 102.98 d (С12, С16); 153.03 s (С13, С15)
;
;
;
benol epoxide
(Scheme 2) in the absence of a catalyst, leading to
isomerization products 5–7 and compound (the
product of the addition of aldehyde to epoxide
3 with pꢀfluorobenzaldehyde 4
8
137.22 s (С14); 18.02 q (С17); 21.88 q (С18); 55.91 q
(С19, С21); 60.58 q (C20).
4
3
[11]) in the presence of montmorillonite clay Kꢀ10:
CHO
R1
R2
OH
OH
R1
O
O
(4, 9)
R2
+
+
+
OH
O
CHO
OH
O
OH
HO
(3)
(5)
(6)
(7)
(
8
,
10
)
4,
8: R1 = F, R2 = H
9,
10: R1 = OH, R2 = OMe
Scheme 2.
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TRANSFORMATIONS OF SEVERAL MONOTERPENOIDS
385
Table 2. The content of mixture components (%) accordꢀ
ing to GLC–MS data recorded during the transformation
of a mixture of isopulegol and aldehyde 14
Earlier [4], we showed that in a complex supercritꢀ
ical solvent containing СО2 and isopropanol, verbenol
2
epoxide
isomerization products in which compounds
identified; at 197°С the conversion of was quantitaꢀ
tive (Table 1). The addition of aldehyde to the reacꢀ
tion mixture did not lead to the formation of intermoꢀ
lecular product , but affected the distribution of
products and the conversion of , which was only 70%
at 220 . The presence of aldehyde led to increased
selectivity in respect of the products with a cyclopenꢀ
tane framework and and to a decreased content of
diol in the reaction mixture. When the reaction temꢀ
perature was raised to 260 , the conversion of
3
was transformed into a complex mixture of
5–7
were
No.
T,
°
C
2
14
16
18
19
20
21
3
4
1
2
200 43.5 20.2 <0.5 6.8 26.6
245 40.3 <0.5 2.6
0
0
8
0
0
46.3 8.1
3
Note: The ratio of mixture/CO flows (mL/min) was 3/5; the presꢀ
2
°
С
4
sure p = 145 atm.
5
7
6
formed into isomerization products under these conꢀ
ditions in the presence of Al2O3 [5], the substrates
should be the compounds that are more stable under
the reaction conditions in order to reduce the contriꢀ
bution from the competitive intramolecular processes.
°
С
3
increased to nearly quantitative, but did not affect the
selectivity of transformations. Although the unidentiꢀ
fied products amounted to more than 40%, each of
these products was up to 5%, and there were no comꢀ
pounds corresponding to the products of interaction
As is known [12], the interaction of isopulegol
2 with
of
3
and
4
in the molecular mass and retention time.
was present in all reaction
benzaldehyde 11 in the presence of Sc(OTf)3 leads to
Unchanged aldehyde
4
the formation of intermolecular product 12
:
mixtures; its content was independent of the condiꢀ
tions of transformation.
CHO
The introduction of two electron donor substituꢀ
ents in the aromatic ring on passing to vanilin 9 should
increase the reactivity of aldehyde in the nucleophilic
addition, thus increasing the probability of intermoꢀ
O
(11)
Sc(OTf)3
2
lecular transformations. Earlier, the interaction of
3
and in the presence of clay Kꢀ10 was reported in [14].
Product 10 formed in this reaction was recently found
9
OH
(12)
to have high analgesic activity [16]. The conversion of
verbenol epoxide
compound 10 was found in the reaction mixture
3 at 175°С was only 55%, and no
Scheme 3.
(Table 1). At the same time, when the reaction temꢀ
Since isopulegol
under the reaction conditions [8], we decided to study
led to the reaction of compounds
and 11 in the presence of
2 remains stable at least at 160°С
perature was raised to 220
time, the intermolecular product 10 (1%). Interestꢀ
ingly, the replacement of aldehyde by vanilin
a change in the ratio of the products of isomerization
of epoxide in favor of diol
°С, we recorded, for the first
4
9
2
Al2O3 in a complex supercritical solvent. It appeared,
however, that benzaldehyde 11 was unstable under
these conditions and was converted into benzyl alcoꢀ
hol 13, probably by the Cannizzaro reaction (disproꢀ
portionation of aldehyde into alcohol and acid). Sigꢀ
nificant amounts of benzyl alcohol 13 were recorded
3
6.
Unexpected results were obtained when we studied
the effect of pressure on the product ratio: at elevated
pressures, the content of 10 decreased, or this product
was absent altogether (nos. 5–8, Table 1). The percent
of unidentified products decreased, and that of comꢀ
already at 60°С; at 150°С the percent of 13 in the
pounds with a cyclopentane framework
increased.
5 and 7
reaction mixture exceeded that of aldehyde 11. The
products of the reaction of
mixture were not found.
2 and 11 in the reaction
Although we managed to find the conditions that
led to the product of the reaction of terpenoid with
aldehyde under the supercritical conditions without
3
9
The introduction of donor substituents in the aroꢀ
matic aldehydes drastically decreases their activity in
Cannizzaro reactions. Our next step, therefore, was the
replacement of benzaldehyde 11 by 3,4,5ꢀtrimethoxyꢀ
any catalyst, the intramolecular transformations still
prevailed.
Recently, we found [8] that citronellal
1 underwent
an effective cyclization to isopulegol in a complex
2
benzaldehyde 14. Since the reaction of isopulegol
with aldehyde 14 was not studied previously, we perꢀ
formed a reaction of with 14 in the presence of montꢀ
17
2
supercritical solvent including CO2 and hexane in the
presence of Al2O3. Therefore, it became promising to
study the possibility of intermolecular reactions under
2
these conditions. Because epoxides are quickly transꢀ morillonite clay Kꢀ10 and isolated products 15
– :
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386
ANIKEEV et al.
21
OMe
OMe
20
OMe
15
14
OMe
OMe
16
CHO
OMe
13
18
19
1
3
O
O
10
7
11
OMe
9
12
6
4
8
OMe
5
+
MeO
H
17
OH
15b) 22%
(14)
K10
(
15
а
,
(
16) 8%
OH
OMe
OMe
OMe
(2)
O
(17)
5%
Scheme 4.
Compounds 15–17 were not described in the literaꢀ Using an alcohol solvent certainly makes the reducꢀ
ture; their structure was determined by NMR and
highꢀresolution mass spectrometry.
Because of the low solubility of 3,4,5ꢀtrimethoxyꢀ
benzaldehyde 14 in hexane and other nonpolar and
tion of 14 to 18 possible under these conditions (the
Meerwein–Ponndorf–Verley reaction [5, 6]). Howꢀ
ever, the content of 18 in the reaction mixture was
below 7% even at 200°C because of the low reactivity
lowꢀpolar solvents, we used methanol as a solvent. of 14 in this reaction (Table 2):
OH
MeO
OMe
OMe
scꢀCO /MeOH
2
+
+
14
Al O
2
3
OMe
OMe
OMe
MeO
MeO
MeO
OMe
18
OMe
OMe
20
(
)
(
19)
(
)
Scheme 5.
At the same time, a new route of the transformation of
aldehyde 14, leading to the formation of acylal 19, was
revealed. Although the reaction mixture contained
scꢀCO /MeOH, 245°C
2
2
1
substantial amounts of both isopulegol 2 and aldehyde
Al O
2
3
OH
14, percent of the intermolecular products of their
interaction was insignificant, the main identified
(21)
intermolecular product being 16
.
Scheme 6.
At 245 aldehyde 14 and acylal 19 completely
°
C
vanished from the reaction mixture; the main product
formed from aldehyde was 1,2,3ꢀtrimethoxyꢀ5ꢀ
(methoxymethyl)benzene 20. Isopulegol 2 also proved
unstable at this temperature and was converted into
citronellol 21, evidently through the opening to citꢀ
The content of 16 formed by the interaction of
14 was insignificant (up to 0.5%).
2 with
Thus we have studied the reactivity of isopulegol
and verbenol epoxide in supercritical fluids in the
presence of aldehydes (benzaldehyde, ꢀfluorobenzalꢀ
2
3
p
ronellal
1 followed by its reduction by the Meerwein–
dehyde, vanilin, and 3,4,5ꢀtrimethoxybenzaldehyde)
Ponndorf–Verley reaction:
using a catalyst (Al2O3) or not. The intramolecular
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TRANSFORMATIONS OF SEVERAL MONOTERPENOIDS
387
6. I. V. Il’ina, V. P. Sivcev, K. P. Volcho, et al., J. Supercrit.
transformations or solvent–reagent reactions were
predominant in all instances; the content of the prodꢀ
ucts of the intermolecular reactions of terpenoids with
aldehydes was up to 1%. Though aldehydes did not
Fluids 61, 115 (2012).
7. V. I. Anikeev, I. V. Il’ina, K. P. Volcho, and N. F. Salaꢀ
khutdinov, Russ. J. Phys. Chem. A 86, 190 (2012).
interact with verbenol epoxide 3, they produced a subꢀ
stantial effect on the distribution of the products of its
isomerization.
8. V. I. Anikeev, I. V. Il’ina, K. P. Volcho, and N. F. Salaꢀ
khutdinov, Russ. J. Phys. Chem. A 86, 1917 (2012).
9. N. F. Salakhutdinov, K. P. Volcho, I. V. Il’ina, et al., Tetꢀ
rahedron 54, 15619 (1998).
10. I. V. Il’ina and K. P. Volcho, et al., Helv. Chim. Acta 90
,
ACKNOWLEDGMENTS
353 (2007).
This work was financially supported by the Russian
Foundation for Basic Research (project no. 11ꢀ08ꢀ
00171ꢀa).
11. I. V. Il’ina, D. V. Korchagina, K. P. Volcho, and
N. F. Salakhutdinov, Russ. J. Org. Chem. 46, 998
(2010).
12. J. S. Yadav, S. B. V. Reddy, A. V. Ganesh, and
G. G. K. S. Narayana Kumar, Tetrahedron Lett. 51
2963 (2010).
,
REFERENCES
1. V. I. Anikeev, Flavour Fragr. J 25, 443 (2010).
2. V. I. Anikeev, I. V. Il’ina, K. P. Volcho, et al., J. Superꢀ
crit. Fluids 52, 71 (2010).
3. V. I. Anikeev, I. V. Il’ina, K. P. Volcho, et al., Russ. J.
13. U. C. Pipas Saha, S. B. Reddy, and K. S. Anil, Org.
Lett. 12, 1824 (2010).
14. I. V. Il’ina, K. P. Volcho, O. S. Mikhalchenko, et al.,
Helv. Chim. Acta 94, 502 (2011).
Phys. Chem. A 84, 1112 (2010).
15. I. V. Il’ina, K. P. Volcho, D. V. Korchagina, et al., Helv.
4. K. P. Volcho, I. V. Il’ina, N. F. Salakhutdinov, and
Chim. Acta 89, 507 (2006).
V. I. Anikeev, Arkivoc 8, 134 (2011).
5. I. V. Il’ina, S. Yu. Kurbakova, K. P. Volcho, et al., 16. T. G. Tolstikova, A. V. Pavlova, E. A. Morozova, et al.,
J. Saudi Chem. Soc. 15, 313 (2011).
RF Patent No. 2430100, Byull. No. 27 (2011).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 3 2013