A novel method for synthesis of benzyl alkyl ethers using Vanadium-based metal complex catalysts

Article abstract of DOI:10.1134/S0965544112040044

A novel method has been developed for the synthesis of benzyl alkyl ethers in 25-85% yields via the reaction of toluene with alcohols in a CCl₄ medium catalyzed by Et₃N-activated VO(acac)₂.

Full text of DOI:10.1134/S0965544112040044

ISSN 0965ꢀ5441, Petroleum Chemistry, 2012, Vol. 52, No. 4, pp. 261–266. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © R.I. Khusnutdinov, A.R. Bayguzina, L.I. Gallyamova, U.M. Dzhemilev, 2012, published in Neftekhimiya, 2012, Vol. 52, No. 4, pp. 292–298.
A Novel Method for Synthesis of Benzyl Alkyl Ethers Using
VanadiumꢀBased Metal Complex Catalysts
R. I. Khusnutdinov, A. R. Bayguzina, L. I. Gallyamova, and U. M. Dzhemilev
Institute of Petroleum Chemistry and Catalysis, Russian Academy of Sciences, pr. Oktyabrya 141, Ufa, 450075 Russia
eꢀmail: ink@anrb.ru
Received January 16, 2012
Abstract—A novel method has been developed for the synthesis of benzyl alkyl ethers in 25–85% yields via
the reaction of toluene with alcohols in a CCl medium catalyzed by Et Nꢀactivated VO(acac) .
4
3
2
DOI: 10.1134/S0965544112040044
Benzyl alkyl ethers find wide application in perꢀ ming mode, from 50 to 270°C at a rate of 8оC/min;
fumery and food industry as fragrances and food addiꢀ carrier gas, helium (47 mL/min)).
tives. Typically they are prepared by the Williamson
reaction between alkali metal alkoxides and benzyl
The reactants were commercially available methaꢀ
nol, ethanol, propanolꢀ1, propanolꢀ2, butanolꢀ1,
pentanolꢀ1, hexanolꢀ1, heptanolꢀ1, octanolꢀ1, undeꢀ
canolꢀ1, cyclopentanol, cyclohexanol, benzyl alcohol,
toluene, ССl , CHCl , СHBr , CBrCl3, formamide,
bromide [1] or Ag O [2]. The synthesis of ethers from
2
substrates that are unstable in an alkaline medium is
performed with benzyl trifluoroacetimidate, which
allows the reaction to be carried out in an acidic
medium [3].
4
3
3
pyridine, and acetonitrile, which were distilled prior to
use. The catalysts V O , VO , V O , VO(acac) , VCl ,
2
5
2
2
3
2
3
and VCl4 were dried in a vacuum desiccator; СBr4,
,2'ꢀbipyridyl, 4,4'ꢀbipyridyl, and triphenylphosphine
Acros) were recrystallized from benzene and ethanol
prior to use.
The reactions were carried out in a glass ampoule
= 10 mL) placed in a stainless steel microautoclave
= 17 mL) with continuous stirring and controlled
When 2ꢀbenzyloxyꢀ1ꢀmethylpyridinium triflate is
used as a benzylating agent, the successful synthesis of
benzyl alkyl ethers can be accomplished in a neutral
medium [4]; they can be also prepared from silyl
ethers and aromatic aldehydes in the presence of triꢀ
ethylsilane and catalytic amounts of FeCl3 [5]. Sirkeꢀ
cioglu et al. [6] reported the synthesis of benzyl alkyl
ethers by the Cu(acac)2ꢀcatalyzed reaction of benzyl
chloride with structurally different alcohols.
2
(
(
(
V
V
heating.
The goal of the present work was to develop a novel General Procedure for Synthesis of Benzyl Alkyl Ethers
efficient synthetic method for benzyl alkyl ethers by
the reaction of toluene with alcohols in a CCl4
medium under the action of metal complex catalysts.
(1, 6–18)
An ampoule was charged under argon with 0.0058 g
(
0.022 mmol) of VO(acac) , 0.01 mL (0.077 mmol) of
2
Et N, 0.2 mL (2.08 mmol) of CCl4, and 8.7 mmol
3
(
0.28 g of СН OH, 0.4 g of С Н OH, 0.52 g of nꢀ
3 2 5
EXPERIMENTAL
С Н OH, 0.52 g of isoꢀС Н OH, 0.64 g of nꢀС Н OH,
3
7
3 7 4 9
0
.77 g of
nꢀС Н OH, 0.89 g of nꢀС Н OH, 1.01 g of nꢀ
5 11 6 13
NMR spectra were recorded on a Bruker Avanceꢀ
С Н OH, 1.13 g of
nꢀС Н OH, 1.5 g of nꢀС Н OH,
4
00 (400.13 and 100.62 MHz, respectively) spectromꢀ
7
15
8 17 11 23
0.94 g of PhCH OH, 0.75 g of cycloꢀC H OH, or 0.87 g
eter in CDCl3; the chemical shifts ( ) are given in ppm
δ
2 5 9
of cyclo
n
ꢀC H OH) (or 34.7 mmol (2.6 g) in the case of
6 11
relative to TMS. Mass spectra were recorded on a Shiꢀ
madzu GCMSꢀQP2010Plus gas chromatograph/mass
ꢀ
С Н OH).
4
9
spectrometer (SPBꢀ5 capillary column, 30 m
×
The sealed ampoule was heated in the autoclave at
о
0
.25 mm; carrier gas, helium; temperature programꢀ 175 С for 14 h in the case of СН OH, С Н OH
,
3
2
5
o
o
–1
ming from 40°C to 300 C at a rate of 8 C min ; evapꢀ
orator temperature, 280 ; ion source temperature.
00
graphic analysis was performed on a Shimadzu GCꢀ the case of cyclo
A instrument (column dimensions of 2 m mm; vigorous stirring. After the reaction completion, the
n
ꢀ
ꢀ
С Н OH
,
iso
ꢀ
С Н OH
,
n
ꢀ
С Н OH
, nꢀС Н OH
,
3
7
3
7
4
9
5 11
°C
n
С Н OH
,
nꢀ
С Н OH
,
nꢀ
С Н OH, or
n
ꢀ
6
13
7
15
8
17
2
°C; ionization energy—70 eV). The chromatoꢀ С Н OH; 20 h in the case of PhCH OH; and 10 h in
11 23 2
ꢀ
C H OH or cycloꢀC H OH with
5 9 6 11
9
×
3
о
stationary phase, silicone SEꢀ30 (5%) supported on autoclave was cooled to 20 С, the reaction mixture
Chromaton NꢀAWꢀHMDS, temperature programꢀ was neutralized with a 10% Na CO3 aqueous solution
2
261

262
KHUSNUTDINOV et al.
(
stirring for 1h), the organic layer was extracted with
Benzyl heptyl ether, 12. Yield 25%, bp 99–100°C/2
δ
13
chloroform, and the extract was filtered through a pad torr. C NMR (CDCl3,
, ppm): 138.78 (Cꢀ1), 128.34
of silica gel (2 g). The unreacted toluene, light ethers, (Cꢀ3, Cꢀ5), 127.60 (Cꢀ2, Cꢀ6), 127.45 (Cꢀ4); 72.88
and chloroform were removed on a rotor evaporator. (Cꢀ7), 70.55 (Cꢀ8), 31.88 (Cꢀ9), 29.84 (Cꢀ10), 29.21
1
The residue was analyzed by GLC using decane as an (Cꢀ11), 26.22 (Cꢀ12), 22.66 (Cꢀ13), 14.11 (Cꢀ14). H
internal standard.
NMR (CDCl3,
δ
, ppm): 0.94 t (3H, 3JHH = 6.8 Hz,
СН ), 1.25–1.80 m (10H, СH (СH ) СH ), 3.52
t
3
2
2 5
3
To obtain chromatographically pure samples, to
determine the yield, and to identify the resulting benꢀ
zyl alkyl ethers, the experiments were performed with
a tenfold greater charge.
3
(
7
2H, JHH = 6.8 Hz, OСН CH ), 4.55 s (2Н, СH O),
.20–7.45 (5H, Ar, CH). Found (%): C, 81.63; H,
2 2 2
1
0.86; O, 7.53. Calculated for C H O (%): C, 81.50;
14
22
H, 10.75; O, 7.76.
An ampoule (50 mL) was charged under argon with
Benzyl octyl ether, 13. Yield 69%, bp 88–90°C/0.5
0
.058 g (0.022 mmol) of VO(acac) , 0.1 mL (0.077 mmol)
13
2
torr. C NMR (CDCl ,
(
7
1
(
6
3
δ
, ppm): 138.79 (Cꢀ1), 128.40
3
of Et N, 2 mL (2.08 mmol) of CCl , 8.7 mmol (2.8 g
3
4
Cꢀ3, Cꢀ5), 127.7 (Cꢀ2, Cꢀ6), 127.59 (Cꢀ4); 72.88 (Cꢀ
of СН OH, 4 g of С Н OH, 5.2 g of nꢀС Н OH, 5.2 g
3
2
5
3 7
), 70.54 (Cꢀ8), 31.91 (Cꢀ9), 30.00 (Cꢀ10), 29.86 (Cꢀ
1), 29.52 (Cꢀ12), 28.73 (Cꢀ13), 25.08 (Cꢀ14), 14.00
of iso
ꢀС Н OH, 6.4 g of nꢀС Н OH, 7.7 g of nꢀ
3 7 4 9
С Н OH, 8.9 g of
n
ꢀ
С Н OH, 10.1 g of
nꢀ
С Н OH,
1
3
5
11
6
13
7
15
Cꢀ15). H NMR (CDCl , , ppm): 0.94 t (3H, JHH =
δ
3
1
1.3 g of
nꢀС Н OH, 15 g of nꢀС Н OH, 9.4 g of
8 17 11 23
.8 Hz, СН ), 1.35–1.80 m (12H, СH (СH ) СH ),
3
2
2 6
s
3
(2Н,
PhCH OH, 7.5 g of cyclo
ꢀ
C H OH, or 8.7 g of cyclo
ꢀ
3
2
5
9
.52 t (2H, JHH = 6.4 Hz, OСН CH ), 4.55
2
2
C H OH) (or 34.7 mmol (26 g) in the case of
nꢀ
6
11
СH O), 7.20–7.50 m (5H, Ar, CH). Found (%): C,
2
С Н OH). The sealed ampoule was placed in the
4
9
8
1.52; H, 10.88; O, 7.60. Calculated for C H O (%):
15 24
autoclave (
V = 100 mL), the autoclave was tightly
C, 81.76; H, 10.98; O, 7.26.
о
sealed and heated at 175 С for 14 h in the case of
Benzyl undecyl ether, 14. Yield 61%, bp 105–
СН OH, С Н OH
,
,
n
,
ꢀ
n
С Н OH,
С Н OH
iso
ꢀ
ꢀ
С Н OH,
С Н OH
n
n
ꢀ
ꢀ
3
С Н OH
2
ꢀ
5
С Н OH
3
ꢀ
7
3
7
13
1
07°C/0.2 torr. C NMR (CDCl , , ppm): 138.72
δ
n
,
n
,
3
4
9
5
11
6
13
7
15
(
(
(
Cꢀ1), 128.31 (Cꢀ3, Cꢀ5), 127.60 (Cꢀ2, Cꢀ6), 127.44
Cꢀ4); 72.84 (Cꢀ7), 70.54 (Cꢀ8), 31.93 (Cꢀ9), 29.78
Cꢀ10), 29.60 (Cꢀ11), 29.50 (Cꢀ12), 29.48 (Cꢀ13),
С Н OH, or
nꢀС Н OH; 20 h in the case of
8
17
11 23
PhCH OH; and 10 h in the case of cycloꢀC H OH or
2
5 9
cycloꢀC H OH, respectively) under continuous stirꢀ
6 11
2
9.35 (Cꢀ14), 28.91 (Cꢀ15), 28.61 (Cꢀ16), 22.69 (Cꢀ
ring. After completion of the reaction, the autoclave
1
о
17), 14.10 (Cꢀ18). H NMR (CDCl ,
δ
, ppm): 0.94
was cooled to 20 С, the ampoule was unsealed, the
3
(
3H, t, 3JHH = 7.2 Hz, СН ), 1.35–1.80 m (18H,
СH (СH ) СH ), 3.64 t (2H, JHH = 6.8 Hz,
reaction mixture was neutralized with 10% Na CO3
3
2
3
aqueous solution (stirring with a magnetic stirrer for 1
h), the organic layer was extracted with chloroform,
and the extract was filtered through a pad of silica gel
2
OСН CH ), 4.52
2 6
3
s (2Н, СH O), 7.20–7.50 m (5H,
2
2
2
Ar, CH). Found (%): C, 82.54; H, 11.45; O, 6.01. Calꢀ
culated for C H O (%): C, 82.38; H, 11.52; O, 6.10.
(
20 g). The unreacted toluene, light ethers, and chloꢀ
18 30
roform were preliminary evaporated on a rotor evapoꢀ
rator. Benzyl chloride, higher dialkyl ethers, and benꢀ 117°C/10 torr. C NMR (CDCl ,
, ppm): 138.29
zyl alkyl ethers were isolated by vacuum distillation.
Benzyl cyclopentyl ether, 17. Yield 69%, bp 116–
13
δ
3
(Cꢀ1), 128.42 (Cꢀ3, Cꢀ5), 127.80 (Cꢀ2, Cꢀ6), 127.35
Cꢀ4); 80.90 (Cꢀ8), 70.71 (Cꢀ7), 32.32 (Cꢀ9, Cꢀ12),
(
2
1
The structure of the resulting benzyl alkyl ethers
was confirmed by the spectral data and by comparing
with the known samples and reference data:
1
3.61 (Cꢀ10, Cꢀ11). H NMR (CDCl ,
δ
, ppm): 1.2–
3
.8 m (8H, CH ), 3.95–4.08 m (1H, CH), 4.59 s (2H,
2
CH ), 7.10–7.60 m (5H, Ar, CH). Found (%): C,
2
benzyl methyl ether, 1 (yield 85%) [7], benzyl ethyl 81.79; H, 9.23; O, 8.98. Calculated for C H O (%):
12
16
ether, 6 (yield 26%), benzyl propyl ether, 7 (yield 27%) C, 81.77; H, 9.15; O, 9.08.
8], benzyl 2ꢀpropyl ether, 8 (yield 32%) [9], benzyl
butyl ether, 9 (yield 34%) [7], benzyl amyl ether, 10
yield 24%) [10], dibenzyl ether, 15 (yield 62%) [11–
[
(
RESULTS AND DISCUSSION
1
2], benzyl cyclohexyl ether, 18 (yield 64%) [13].
Preliminary experiments showed that benzyl
Benzyl hexyl ether, 11. Yield 52%, bp 106– methyl ether , a valuable fragrance with a fruit smell
1
13
1
07°C/6 torr. C NMR (CDCl3,
δ
, ppm): 138.74 of ilangꢀilang and green hyacinth flowers, can be synꢀ
(
(
(
Cꢀ1), 128.34 (Cꢀ3, Cꢀ5), 127.59 (Cꢀ2, Cꢀ6), 127.45 thesized by reacting toluene with methanol in a ССl4
Cꢀ4); 72.90 (Cꢀ7), 70.54 (Cꢀ8), 29.91 (Cꢀ9), 28.78 medium in the presence of the following vanadium
1
Cꢀ10), 25.87 (Cꢀ11), 22.78 (Cꢀ12), 14.14 (Cꢀ13). H compounds: V O , VO , V O , VCl , VCl4, or VO(acac)2
,
2
5
2
2
3
3
3
NMR (CDCl3,
СН ), 1.35
(
δ
, ppm): 1.04 (3H, t, JHH = 7.2 Hz, of which VO(acac)2 is the best (the reaction is too senꢀ
(8H, СH (СH ) СH ), 3.57 sitive to the moisture content). As ligands, the followꢀ
(2Н, СH O), ing compounds were also tested: formamide, pyridine,
⎯
1.80
m
t
3
2
2 4
3
3
2H, JHH = 6.4 Hz, OСН CH ), 4.54
s
2
2
2
7
.30–7.50 m (5H, Ar, CH). Found (%): C, 81.41; H, 2,2'ꢀbipyridyl, 4,4'ꢀbipyridyl, acetonitrile, and tripheꢀ
1
0.37; O, 8.22. Calculated for C H O (%): C, 81.20; nylphosphine, which are inferior in activity to triethyꢀ
13
20
H, 10.48; O, 8.32.
lamine (see table).
PETROLEUM CHEMISTRY Vol. 52
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2012

A NOVEL METHOD FOR SYNTHESIS OF BENZYL ALKYL ETHERS
263
Effect of the catalyst nature, ligand nature, and reaction time on the toluene conversion and product yields in the reaction
of toluene with CCl and MeOH (175
°
C)
4
Yields of products, %
Run
no.
Toluene
conversion,%
Catalyst
Ligand
Time, h
1
2
3
4
5
6
7
8
V2O3
–
4
''
''
''
''
''
''
''
15
16
4
0.4
1
2.8
12
0.4
19
0.3
2
0.5
1
3
8
VO2
–
0
0
V2O5
–
0.3
0
2.4
4
0.3
1
0.5
1
0.1
2
VCl3
–
27
20
40
0
VCl4
–
–
0
10
32
0
6.5
3
1.5
1
2
0
VO(acac)2
4
0
0
''
''
HCONH2
0
0
0
0
0
2,2'ꢀ
bipyridyl
9
1
4
3
0
0
1
9
''
4,4'ꢀ
bipyridyl
''
10
0.5
6
6
1
3
0.5
1
3
1
3
10
11
12
13
14
15
16
17
18
19
20
''
CH CN
''
47
100
12
31
39
4
1
2
3
''
PPh3
''
26
12
11
10
''
pyridine
''
2
4
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
''
Et N
''
47
2
42
29
35
42
48
49
52
61
80
85
2
1
3
VO(acac)2
''
''
''
''
''
''
''
''
''
1.5
2
4
6
7
9
32
0.6
1
2
0.4
0.5
1
''
''
''
''
''
''
''
''
39
2.5
2
47
2
55
5
1
1
57
6.5
1
0.5
1
65
10
2
10
74
10
10
10
2
1
2
1
2
12
14
95
3
2
2
100
3
2
*
2ꢀmethyldiphenylmethane, 3ꢀmethyldiphenylmethane, 4ꢀmethyldiphenylmethane (5 : 1 : 5).
Among the tested halogenated methanes: ССl4, (8%), benzaldehyde (8%), and diarylmethanes in the
CHCl , СHBr , CBr , and CBrCl3, the reaction proꢀ ratio of 2ꢀmethyldiphenylmethane : 3ꢀmethyldipheꢀ
3
3
4
ceeds best of all with carbon tetrachloride. Chloroꢀ nylmethane : 4ꢀmethyldiphenylmethane = 5 : 1 : 5
form and bromoform appeared to be inactive in this (4%) [14, 15], as well as CHBr3, MeOMe, HCO Me
,
2
reaction, and the use of CBr4 or CBrCl3 made the proꢀ and MeBr. The analogous reaction with CBrCl3 led to
cess nonselective despite a high conversion of the reacꢀ the formation of a more complex product mixture
о
tant toluene (47% and 59% for 4 h at 175 С, respecꢀ consisting of benzyl methyl ether (12%), benzyl broꢀ
tively). Thus, the reaction of toluene with CBr4 and mide (3%), benzyl chloride (2%), benzaldehyde
MeOH in the presence of the VO(acac) –Et N cataꢀ (11%), methyl benzoate (20%), benzyl alcohol (6%),
2
3
lytic system affords benzyl methyl ether (4%), benzyl and diarylmethanes in the 2ꢀmethyldiphenylmethane :
bromide (3%), methyl benzoate (20%), benzyl alcohol 3ꢀmethyldiphenylmethane 4ꢀmethyldiphenylꢀ
:
PETROLEUM CHEMISTRY Vol. 52
No. 4
2012

264
KHUSNUTDINOV et al.
methane ratio of 3 : 1 : 3 (5%), as well as CHBrCl2,
The greatest yield of benzyl methyl ether 1 (85%
over 14 h) is achieved using triethylamineꢀactivated
CHBr Cl, CHBr , C Cl , C Cl6, MeOMe, HCO Me
,
2
3
2
4
2
2
MeBr, and MeCl.
VO(acac)2 as a catalyst.
VO(acac)2⎯Et N
3
PhMe + MeOH + CCl4
BnOMe + BnCl + PhCHO + BnOH
175°C, 14 h
–Me O
2
1
2
3%
3
10%
4
2%
8
5%
VO(acac) : Et N : toluene : MeOH : CCl = 1 : 5 : 100 : 400 : 100.
2
3
4
Scheme 1.
Along with compounds 1–4, the reaction mixꢀ hyde dimethyl acetal, methyl formate, which are
ture also contained the following byproducts: formed by the following scheme according to pubꢀ
chloroform, HCl, water, dimethyl ether, formaldeꢀ lished data [16, 17]:
+
H , MeOH
VO(acac)2
CH (OMe)
2
2
MeOH + CCl4
MeOH
CH O
2
–HCl
–CHCl3
MeOCl
5
HCO Me.
2
Scheme 2.
A key byproduct affecting the reaction course is tetrachloride by the action of VO(acac)2 to give benzyl
methyl hypochlorite, which was also detected in our chloride, which undergoes methanolysis at the final
experiments (iodometric titration, concentration of stage.
0
.03–0.05 mg/mL). Taking into account the formaꢀ
tion of methyl hypochlorite, we first assumed the reacꢀ
tion scheme suggesting toluene oxidation with MeOCl
to the final product.
[V]
+
CH OH, [V]
3
PhMe + CCl4
BnCl
2
BnOMe.
–
CHCl3
–HCl
1
Scheme 4.
VO(acac)2
MeOH + CCl4
MeOCl + CHCl3
VO(acac)2
This assumption is supported by the results of
experiments with an authentic sample of benzyl chloꢀ
PhMe + MeOCl
BnOMe.
1
75
°
C, 6 h
–HCl
1
ride
with a quantitative yield under the reaction condiꢀ
and chloroform tions; when the reaction is run with an admixture of
have been found in reaction mixture, the most likely carbon tetrachloride ([VO(acac) ] : [BnCl] :
scheme of the formation of ether
seems to involve [MeOH] : [CCl ] = 1 : 100 : 400 : 100), the yield of
2, which transforms into benzyl methyl ether 1
Scheme 3.
However, since benzyl chloride
2
2
1
4
two steps, toluene is initially chlorinated with carbon benzyl methyl ether makes 91%.
BnOMe 100%
175°C, 6 h
conv. 100%
VO(acac) –Et N
1
2
3
BnCl + MeOH
2
CCl4
BnOMe 91%.
1
75°C, 6 h
conv. 91%
1
Scheme 5.
Benzaldehyde
3 detected in a small amount (10%) result from the benzyl alcohol oxidation mediated by
in the reaction mixture (Table 1, run 22) is likely to CCl4 according to the following scheme:
PETROLEUM CHEMISTRY Vol. 52
No. 4
2012

A NOVEL METHOD FOR SYNTHESIS OF BENZYL ALKYL ETHERS
265
HCl
2MeOH
H O + (Me) O
2 2
CCl4
H O
2
CCl4
[V]
PhMe
BnCl
2
BnCl
BnOCl –
PhCHO.
HCl
4
5
3
Scheme 6.
We performed a kinetic study of the reaction of tolꢀ undecanolꢀ1 enter this reaction. The yields of the corꢀ
uene with CCl4 and methanol in the presence of the responding ethers 6–14 are 25–69%. It is noteworthy
VO(acac) –Et N catalytic system. As can be seen from that as the length of the alkyl radical in the alcohol
2
3
the data presented, the amount of benzyl chloride in molecule increases, the yield of benzyl alkyl ether
the reaction products does not exceed 3% for a reacꢀ increases, a fact that can be explained by the ease of
tion time of 1.5–14 h (see table).
formation of homoethers from lower alcohols and
The reaction is common in character for the alcoꢀ their active oxidation with CCl4 into the correspondꢀ
hol series: ethanol, propanolꢀ1, propanolꢀ2, butanolꢀ ing aldehydes and esters, which are detected indeed in
1
, pentanolꢀ1, hexanolꢀ1, heptanolꢀ1, octanolꢀ1, and small amounts in the reaction mixture.
VO(acac) –Et N
2
3
PhMe + ROH + CCl4
BnOR.
1–14
175°C, 14 h
–ROR
R = C H
(6) 26%
(7) 27%
(8) 32%
2
5
7
7
n
i
ꢀC H
3
ꢀC H
3
n
ꢀC H
(
9) 34%
4
9
n
n
n
n
ꢀC H
(10) 24%
(11) 52%
(12) 25%
(13) 69%
(14) 61%
5
11
ꢀC H
6
13
15
17
23
ꢀC H
7
ꢀC H
8
n
ꢀC H
11
Scheme 7.
Benzyl butyl ether
most valuable in the series of benzyl alkyl ethers. It is yield of 67% at a toluene conversion of 69%.
allowed for use in many countries as a flavor for food
When benzyl chloride is used instead of toluene as
products: drinks, desserts, baked goods, ice cream, a reactant (at the catalyst to reactants ratio
and ice. Therefore, we carried out an additional study of [VO(acac) ] : [Et ] : [benzyl chloride] : [
С Н OH] = 1 : 5 : 100 : 400) at 175 , the reaction
time reduces to 5 h, but the yield of benzyl butyl ether
9, which has a fruit smell is the toluene transforms into benzyl butyl ether 9 with a
N
3
nꢀ
2
°
С
to find the conditions that would facilitate increasing
the yield of benzyl butyl ether. In particular, the reacꢀ
tion selectivity for benzyl butyl ether can be enhanced
4
9
9
makes ~100% despite this fact.
The above reaction with toluene is characteristic of
by increasing the concentration of
nꢀС Н OH, with
4 9
benzyl alcohol. The main product of the reaction is
dibenzyl ether 15 (53%). At the same time, a marked
the reaction time being reduced to 10 h.
о
Under the optimal conditions: 175 С, 10 h, and a amount of the alcohol is oxidized to benzaldehyde
3
catalyst to reactants ratio of [VO(acac) ] : [Et N] : [tolꢀ (11%) and undergoes substitution chlorination to
2
3
uene] : [СCl4] : [nꢀС Н OH] = 1 : 5 : 100 : 100 : 1600, convert into benzyl chloride 2 (30%).
4 9
VO(acac) –Et N
3
2
BhOH + PhOH + CCl4
Bn O + BnCl + PhCHO
2
175°C, 20 h
toluene
conversion 100%
15
2
3
VO(acac) : Et N : toluene : BnOH : CCl = 1 : 5 : 100 : 400 : 100 [4.2 : 2.5 : 1]
2
3
4
VO(acac) : Et N : toluene : BnOH : CCl = 1 : 5 : 100 : 800 : 100 [20 : 10 : 1]
2
3
4
Scheme 8.
PETROLEUM CHEMISTRY Vol. 52
No. 4
2012

266
KHUSNUTDINOV et al.
As the benzyl alcohol concentration increased relꢀ
The analogous reaction of toluene with cyclopenꢀ
ative to that of toluene ([VO(acac) ] : [Et N] : [toluꢀ tanol and cyclohexanol led to the production of benzyl
2
3
ene] : [СCl4] : [BnOH] = 1 : 5 : 100 : 100 : 800) the cyclopentyl 17 and benzyl cyclohexyl 18 ethers in 64
yield of dibenzyl ether 15 reached 62%, and the toluꢀ and 69 % yields, respectively.
ene conversion was complete.
CCl , VO(acac) , Et N
4
2
3
PhMe + (CH2)n
Bn
O
(CH )
2 n
OH
175°C, 10 h
n = 2, 3
n
n
= 2 (17) 69%
= 2 (17) 64%
VO(acac) : Et N : toluene : ROH : CCl = 1 : 5 : 100 : 400–1600 : 100
2
3
4
Scheme 9.
Thus, the reaction under study offers a simple route
for the synthesis of benzyl alkyl ethers from available
reagents: toluene, CCl4, and alcohols.
7. S. A. Voitkevich, 865 Fragrances for Perfumery and
Household Chemistry (Pishchevaya promyshlennost’,
Moscow, 1994) [in Russian].
8
. W. J. Monacelli and G. F. Hennion, J. Am. Chem. Soc.
, 1722 (1941).
63
ACKNOWLEDGMENTS
9
. W. T. Olson, H. F. Hipsher, C. M. Buess, I. A. Goodꢀ
man, I. Hart, J. H. Lamneck, L. C. Gibbons, J. Am.
Chem. Soc. 69, 2451 (1947).
This work was supported by the Russian Foundaꢀ
tion for Basic Research and the Government of
Republic of Bashkortostan, RFBR project Povolzh’e
1
1
1
0. F. C. Whitmore and D. P. Langlois, J. Am. Chem. Soc.
, 1518 (1933).
1. S. Kim, K. Chung, and S. Yang, J. Org. Chem. 52, 3917
1987).
2. The Aldrich Catalog/Handbook of Fine Chemicals; (Aldꢀ
rich, Milwaukee, 2007 2008).
5
5
1
2ꢀ03ꢀ97019.
(
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2012