Synthesis of alkyl methyl ethers and alkyl methyl carbonates by reaction of alcohols with dimethyl carbonate in the presence of tungsten and cobalt complexes

Article abstract of DOI:10.1134/S1070428014060050

Alkyl methyl ethers and alkyl methyl carbonates were synthesized by reaction of alcohols with dimethyl carbonate in the presence of tungsten and cobalt carbonyls. Optimal reactant and catalyst ratios, as well as reaction conditions, were found for selective formation of alkyl methyl ethers or alkyl methyl carbonates.

Full text of DOI:10.1134/S1070428014060050

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 6, pp. 790–795. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © R.I. Khusnutdinov, N.A. Shchadneva, Yu.Yu. Mayakova, 2014, published in Zhurnal Organicheskoi Khimii, 2014, Vol. 50, No. 6,
pp. 808–813.
Synthesis of Alkyl Methyl Ethers and Alkyl Methyl Carbonates
by Reaction of Alcohols with Dimethyl Carbonate in the Presence
of Tungsten and Cobalt Complexes
R. I. Khusnutdinov, N. A. Shchadneva, and Yu. Yu. Mayakova
Institute of Petrochemistry and Catalysis, Russian Academy of Sciences,
pr. Oktyabrya 141, Ufa, 450075 Bashkortostan, Russia
e-mail: ink@anrb.ru
Received July 24, 2013
Abstract—Alkyl methyl ethers and alkyl methyl carbonates were synthesized by reaction of alcohols with
dimethyl carbonate in the presence of tungsten and cobalt carbonyls. Optimal reactant and catalyst ratios, as
well as reaction conditions, were found for selective formation of alkyl methyl ethers or alkyl methyl carbonates.
DOI: 10.1134/S1070428014060050
Dialkyl and diaryl carbonates are stable organic
compounds that are widely used as ultrapure solvents,
extractants for precious metals, and components of
light-sensitive compositions for the preparation of
lithographic plates. They are also intermediate prod-
ucts in the synthesis of drugs (phenobarbital, cephalo-
sporin, penicillin, β-lactam, etc.), herbicides, fungi-
cides, polyurethanes, ureas, and heat-resistant rubber,
components of antifreezes, etc. [1, 2].
sulfate, but this disadvantage is compensated by lower
toxicity [3].
Dimethyl carbonate is used as an efficient methylat-
ing agent for alcohols. The reaction is catalyzed by
basic aluminum oxide at 200°C. When aluminum
oxide, as well as MgO, K2CO3, or KF/Al2O3, is used as
catalyst, the reaction involves exclusively the carbonyl
carbon atom, dimethyl carbonate undergoes transester-
ification, and the only products are alkyl methyl and
dialkyl carbonates. A stoichiometric amount of catalyst
with respect to alcohol is necessary for successful
reaction [4–6].
Taking into account the importance and perspec-
tiveness of nontrivial and environmentally balanced
methanol-free methods for the preparation of alkyl
methyl ethers and alkyl methyl carbonates, we set
ourselves the goal of developing transition metal
complex catalysts to accelerate methylation of primary,
secondary, and tertiary alcohols with dimethyl car-
bonate, as well as transesterification of the latter.
Dimethyl carbonate is the simplest carbonic acid
ester which is an environmentally safe synthetic equiv-
alent of phosgene, dimethyl sulfate, and methyl halides
due to its lower toxicity as compared to other car-
boxylating or alkylating agents. Dimethyl carbonate is
not converted into inorganic salts since the leaving
group in its reactions is methyl hydrogen carbonate
which decomposes into methanol and carbon dioxide.
The reactivity of dimethyl carbonate is lower than the
reactivity of commonly used methylating agents such
as methyl halides MeX (X = I, Br, Cl) and dimethyl
Scheme 1.
W(CO)6
ROMe
+ CO2 + MeOH
97–99%
180°C, 1 h
VIIIa–XIVa
ROH
+
(MeO)2C=O
Co2(CO)8
95–98%
I–VII
ROC(O)OMe
+
ROC(O)R + MeOH
VIIIb–XIVb 20 : 1 VIIIc–XIVc
I, VIIIa–VIIIc, R = Et; II, IXa–IXc, R = Pr; III, Xa–Xc, R = Bu; IV, XIa–XIc, R = C5H11; V, XIIa–XIIc, R = Me2CH(CH2)2;
VI, XIIIa–XIIIc, R = C6H13; VII, XIVa–XIVc, R = C8H17.
790

SYNTHESIS OF ALKYL METHYL ETHERS AND ALKYL METHYL CARBONATES
791
Scheme 2.
O
W(CO)6
~100%
O
O
XVIb
+
CH2OH
180°C, 1 h
XVIc
+
(MeO)2C=O
O
Co2(CO)8
90%
XV
O
OMe
XVIb
Scheme 3.
180°C, 1 h
100%
O
OMe
O
W(CO)6
+
(MeO)2C=O
XVIIIb
CH2OH
180°C, 3 h
100%
XVII
+
XVIIIb
OMe
XVIIIa
2 : 1
Among the examined Fe, Ni, Co, Cr, V, Mn, Mo,
and W salts and coordination compounds, tungsten and
cobalt carbonyls W(CO)6 and Co2(CO)8 showed an ap-
preciable catalytic activity in the reaction of dimethyl
carbonate with alcohols. The reaction of dimethyl car-
bonate with primary alcohols I–VII in the presence of
W(CO)6 at a W(CO)6–ROH–Me2CO3 molar ratio of
3 :100:400 (180°C, 1 h) gave alkyl methyl ethers
VIIIa–XIVa with high selectivity and high yield (95–
98%). Dimethyl carbonate was taken in excess, for it
acted simultaneously as reactant and solvent. The
length of the alkyl radical in the alcohol molecule does
not affect the yield of VIIIa–XIVa to an appreciable
extent. When W(CO)6 was replaced by Co2(CO)8, the
reaction direction changed toward formation of the
corresponding alkyl methyl carbonates VIIIb–XIVb.
Apart from ethers VIIIb–XIVb, the reaction mixtures
contained small amounts (2–5%) of dialkyl carbonates
VIIIc–XIVc (Scheme 1).
Primary alcohols containing bulky substituents
reacted with dimethyl carbonate along different path-
ways. No benzyl methyl ether was formed in the reac-
tion of benzyl alcohol XV with Me2CO3 in the pres-
ence of W(CO)6, and the reaction mixture contained
equimolar amounts of benzyl methyl carbonate (XVIb)
and dibenzyl carbonate (XVIc), the conversion of XV
being complete. The reaction of XV with Me2CO3
catalyzed by Co2(CO)8 gave 90% of benzyl methyl
carbonate (XVIb) (Scheme 2).
Adamantan-1-ylmethanol (XVII) reacted with di-
methyl carbonate in the presence of W(CO)6 under the
optimal conditions (180°C, 1 h) to produce adamantan-
1-ylmethyl methyl carbonate (XVIIIb) in quantitative
yield. Increase of the reaction time to 3 h (180°C) led
to the formation of adamantan-1-ylmethyl methyl ether
(XVIIIa) and adamantan-1-ylmethyl methyl carbonate
(XVIIIb) at a ratio of 2:1 (Scheme 3). The reaction
Scheme 4.
W(CO)6
180°C, 1 h
OH
OMe
+
(MeO)2C=O
(MeO)2C=O
Me
OH
Me
98%
Me
Me
XIX
XXa
W(CO)6
180°C, 1 h
OMe
+
96%
XXI
XXIIa
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KHUSNUTDINOV et al.
792
Reactions of alcohols with dimethyl carbonate in the presence of metal complexesa
Product composition, %
ROCO2Me
Conversion
of alcohol, %
Alcohol
Ethanol
Catalyst
ROMe
ROCO2R
Co2(CO)8
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
Co2(CO)8
W(CO)6
098
097
099
094
098
100
100
090
100
092
099
098
099
090
100
100
100
–
–
100
100
–
–
–
Propan-1-ol
Butan-1-ol
100
–
–
Butan-1-ol
095
–
05
–
Pentan-1-ol
Pentan-1-ol
3-Methylbutan-1-ol
3-Methylbutan-1-ol
Hexan-1-ol
Hexan-1-ol
Octan-1-ol
100
–
098
–
02
–
100
–
096
005
100
003
100
050
100
100
030
100
04
–
095
–
–
097
–
–
Octan-1-ol
–
PhCH2OH
–
50
–
PhCH2OH
–
AdCH2OH
–
–
b
AdCH2OH
W(CO)6
070
–
–
AdCH2OH
Co2(CO)8
–
a
Ratio catalyst–alcohol–Me2CO3 3:100:400; 180°C, 1 h.
180°C, 3 h.
b
catalyzed by Co2(CO)8 quantitatively afforded ester
XVIIIb. The yields of alkyl methyl ethers and alkyl
methyl carbonates in the reactions of primary alcohols
with dimethyl carbonate, catalyzed by W(CO)6 and
Co2(CO)8, are given in table.
Cyclohexanol (XXI) reacted with dimethyl carbonate
in the presence of Co2(CO)8 to give cyclohexyl methyl
carbonate (XXIIb). Under analogous conditions,
isopropyl alcohol (XXIII) and 1-cyclopropylethanol
(XXIV) were converted into methyl carbonates XXVb
and XXVIb, respectively (Scheme 5).
Alkyl methyl ethers XXa and XXIIa were obtained
in high yields in the reactions of secondary alcohols
XIX and XXI, respectively, with dimethyl carbonate
in the presence of W(CO)6 (180°C, 1 h; Scheme 4).
The reaction of tert-butyl alcohol (XXVII) with
dimethyl carbonate catalyzed by both W(CO)6 and
Co2(CO)8 afforded tert-butyl methyl ether (XXVIIIa)
Scheme 5.
Co2(CO)8
180°C, 1 h
OH
OC(O)OMe
+
(MeO)2C=O
(MeO)2C=O
(MeO)2C=O
88%
XXI
XXIIb
Co2(CO)8
180°C, 1 h
OH
OC(O)OMe
+
+
97%
Me
Me
Me
Me
XXIII
XXVb
Co2(CO)8
180°C, 1 h
OH
OC(O)OMe
Me
98%
Me
XXIV
XXVIb
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SYNTHESIS OF ALKYL METHYL ETHERS AND ALKYL METHYL CARBONATES
793
Scheme 6.
[W] or [Co]
180°C, 1 h
t-BuOH
+
(MeO)2C=O
(MeO)2C=O
t-BuOMe
100%
XXVII
XXVIIIa
Co2(CO)8
180°C, 1 h
Me
Me
OH
OMe
+
100%
XXIX
XXXa
Scheme 7.
W(CO)6
~100%
OMe
XXXIIa
180°C, 1 h
+
(MeO)2C=O
OH
O
Co2(CO)8
~100%
XXXI
XXXIIa
+
O
OMe
1:1.5
XXXIIb
Scheme 8.
O
O
[W] or [Co]
180°C, 1 h
+
(MeO)2C=O
+ MeOH + CO2
95%
HO
MeO
XXXIVa
XXXIII
[W(CO)6]
180°C, 1 h
OH
OMe
+
(MeO)2C=O
95%
XXXV
XXXVIa
in quantitative yield. 1,1-Dicyclopropylethanol
(XXIX) reacted with Me2CO3 in the presence of
Co2(CO)8, yielding methyl ether XXXa as the only
product (Scheme 6).
In summary, tungsten and cobalt carbonyls catalyze
methylation of primary, secondary, and tertiary alco-
hols and phenol with dimethyl carbonate, as well as
partial or complete transesterification of dimethyl car-
bonate with these alcohols. The structure of the isolat-
ed compounds was confirmed by spectral methods, as
well as by comparing their properties with those of
authentic samples and with published data [7–9].
The reaction of adamantan-1-ol (XXXI) with di-
methyl carbonate and W(CO)6 as catalyst (180°C, 1 h)
led to the formation of 1-methoxyadamantane
(XXXIIa), whereas in the presence of Co2(CO)8
a mixture of 1-methoxyadamantane (XXXIIa) and
1-adamantyl methyl carbonate (XXXIIb) at a ratio of
1:1.5 was obtained, the conversion of XXXI being
complete (Scheme 7). 5-Hydroxyadamantan-2-one
(XXXIII) under analogous conditions, in the presence
of both W(CO)6 and Co2(CO)8, was converted into
5-methoxyadamantan-2-one (XXXIVa) in high yield.
No carbonates were detected in the reaction mixture.
Phenol reacted with dimethyl carbonate (180°C, 1 h) in
the presence of W(CO)6 to give anisole, while it failed
to react in the presence of Co2(CO)8 (Scheme 8).
EXPERIMENTAL
The 13C NMR spectra were recorded on a Bruker
Avance-400 spectrometer at 100.62 MHz using CDCl3
as solvent. The mass spectra were obtained on
a Shimadzu GCMS-QP2010Plus instrument (SPB-5
capillary column, 30 m×0.25 mm; carrier gas helium;
oven temperature programming from 40 to 300°C at
a rate of 8 deg/min; injector temperature 280°C; ion
source temperature 200°C; electron impact, 70 eV).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 6 2014

KHUSNUTDINOV et al.
794
The elemental compositions were determined on
a Carlo Erba 1106 analyzer.
13.95 (C6), 22.59 (C5), 25.40 (C3), 28.59 (C2), 31.61
(C4), 54.41 (OCH3), 67.97 (C1), 155.41 (C=O). Found,
%: C 59.93; H 9.98. C8H16O3. Calculated, %: C 59.97;
H 10.07.
The progress of reactions and the purity of products
were monitored by gas–liquid chromatography on
Shimadzu GC-9A and GC-2014 instruments (2-m×
3-mm column packed with 5% of SE-30 on Chromaton
N-AW-HMDS; oven temperature programming from
50 to 270°C at a rate of 8 deg/min; carrier gas helium,
flow rate 47 mL/min).
Methyl octyl carbonate (XIVb). Yield 98%,
bp 92–93°C (7 mm). 13C NMR spectrum, δC, ppm:
14.15 (C8), 22.52 (C7), 25.60 (C3), 29.07 (C2), 29.22
(C4), 29.35 (C5), 31.75 (C6), 54.61 (OCH3), 68.08 (C1),
155.81 (C=O). Found, %: C 63.74; H 10.67. C10H20O3.
Calculated, %: C 63.80; H 10.71.
General procedure for the reaction of alcohols
with dimethyl carbonate. A 17-mL stainless-steel
high-pressure micro reactor was charged with 3 mmol
of W(CO)6 or Co2(CO)8, 100 mmol of the correspond-
ing alcohol, and 400 mmol of dimethyl carbonate. The
reactor was tightly closed, and the mixture was heated
for 1 h at 180°C. When the reaction was complete, the
reactor was cooled to room temperature and opened,
and the mixture was filtered through a layer of alumi-
num oxide. Unreacted dimethyl carbonate was distilled
off, and the residue was distilled under atmospheric or
reduced pressure or recrystallized from ethanol.
Benzyl methyl carbonate (XVIb). Yield 90%,
bp 89–90°C (5 mm). 13C NMR spectrum, δC, ppm:
54.83 (OCH3), 69.71 (CH2O), 127.51 (C2, C6), 128.31
(C4), 128.54 (C3, C5), 135.35 (C1), 155.78 (C=O).
Found, %: C 64.99; H 6.02. C9H10O3. Calculated, %:
C 65.05; H 6.07.
13
Dibenzyl carbonate (XVIc). Yield 50%. C NMR
spectrum, δC, ppm: 69.61 (CH2O), 127.81 (C2, C6),
128.43 (C4), 128.57 (C3, C5), 135.21 (C1), 155.71
(C=O). Found, %: C 74.28; H 5.79. C15H14O3. Calcu-
lated, %: C 74.36; H 5.82.
Methyl ethyl carbonate (VIIIb). Yield 98%,
bp 90–91°C. 13C NMR spectrum, δC, ppm: 14.84
(CH3), 55.44 (OCH3), 64.50 (CH2O), 155.42 (C=O).
Found, %: C 46.08; H 7.72. C4H8O3. Calculated %:
C 46.15; H 7.75.
(Adamantan-1-yl)methyl methyl carbonate
(XVIIIb). Yield ~100%, mp 119–120°C (from EtOH).
13C NMR spectrum, δC, ppm: 27.90 (C3, C5, C7), 36.82
(C1), 36.92 (C4, C6, C9), 39.06 (C2, C8, C10), 54.60
(OCH3), 77.72 (CH2O), 156.36 (C=O). Found, %:
C 69.89; H 10.02. C14H24O3. Calculated, %: C 69.96;
H 10.07.
Methyl propyl carbonate (IXb). Yield 97%,
bp 113.5–114°C. 13C NMR spectrum, δC, ppm: 10.17
(CH3), 21.43 (CH2), 55.20 (OCH3), 70.72 (CH2O),
155.20 (C=O). Found, %: C 50.78; H 8.51. C5H10O3.
Calculated, %: C 50.84; H 8.53.
Cyclohexyl methyl carbonate (XXIIb). Yield
88%, bp 80–80.5°C (2 mm). 13C NMR spectrum, δC,
ppm: 23.91 (C3, C5), 26.69 (C4), 31.24 (C2, C6), 54.12
(OCH3), 75.98 (C1), 154.90 (C=O). Found, %: C 60.69;
H 8.87. C8H14O3. Calculated, %: C 60.75; H 8.86.
Butyl methyl carbonate (Xb). Yield 95%, bp 132–
132.5°C. 13C NMR spectrum, δC, ppm: 14.02 (C4),
19.23 (C3), 30.97 (C2), 55.04 (OCH3), 155.72 (C=O).
Found, %: C 54.48; H 9.07. C6H12O3. Calculated, %:
C 54.53; H 9.15.
Methyl 1-methylethyl carbonate (XXVb). Yield
13
97%, bp 106–106.5°C. C NMR spectrum, δC, ppm:
21.73 (CH3), 54.37 (OCH3), 71.92 (CH), 155.26 (C=O).
Found, %: C 50.78; H 8.49. C5H10O3. Calculated, %:
C 50.84; H 8.53.
Methyl pentyl carbonate (XIb). Yield 98%,
13
bp 70.5–71°C (28 mm). C NMR spectrum, δC, ppm:
14.10 (C5), 21.85 (C4), 30.43 (C3), 29.22 (C2), 55.04
(OCH3), 67.76 (C1), 155.77 (C=O). Found, %: C 57.48;
H 9.61. C7H14O3. Calculated, %: C 57.51; H 9.65.
1-(Cyclopropyl)ethyl methyl carbonate (XXVIb).
Yield 98%, bp 65.5–66°C (20 mm). 13C NMR spec-
trum, δC, ppm: 2.36 (C2, cyclopropyl), 3.61 (C3, cyclo-
propyl), 18.94 (CH3), 19.44 (C1, cyclopropyl), 54.39
(OCH3), 79.56 (CHO), 155.44 (C=O). Found, %:
C 58.28; H 8.35. C7H12O3. Calculated, %: C 58.32;
H 8.39.
Methyl 3-methylbutyl carbonate (XIIb). Yield
96%, bp 66.4–67.2°C (30 mm). 13C NMR spectrum,
δC, ppm: 23.31 (C4, 3-CH3), 25.08 (C3), 38.85 (C2),
55.04 (OCH3), 65.62 (C1), 155.77 (C=O). Found, %:
C 57.45; H 9.59. C7H14O3. Calculated, %: C 57.51;
H 9.65.
1,1-Dicyclopropyl-1-methoxyethane (XXXa).
Yield ~100%, bp 67–67.5°C (10 mm). 13C NMR spec-
trum, δC, ppm: 0.07 (C2, cyclopropyl), 0.10 (C2′, cyclo-
propyl), 4.27 (C3′, cyclopropyl), 5.34 (C3, cyclo-
Hexyl methyl carbonate (XIIIb). Yield 92%,
bp 75–76°C (14 mm). 13C NMR spectrum, δC, ppm:
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SYNTHESIS OF ALKYL METHYL ETHERS AND ALKYL METHYL CARBONATES
795
propyl), 17.83 (C1, C1′, cyclopropyl), 20.48 (CH3),
REFERENCES
54.51 (OCH3), 75.10 (C–O). Found, %: C 77.02;
H 11.45. C9H16O. Calculated, %: C 77.09; H 11.50.
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Adamantan-1-yl methyl carbonate (XXXIIb).
Yield 60%, sublimes at 120–121°C (10 mm). 13C NMR
spectrum, δC, ppm: 31.53 (C3, C5, C7), 36.28 (C4, C6,
C9), 40.74 (C2, C8, C10), 54.49 (OCH3), 81.25 (C1),
153.34 (C=O). Found, %: C 68.49; H 8.56. C12H18O3.
Calculated, %: C 68.54; H 8.63.
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1-Methoxyadamantan-4-one (XXXIVa). Yield
95%, sublimes at 95–96°C (5 mm). 13C NMR spec-
trum, δC, ppm: 30.29 (C7), 38.27 (C8, C10), 40.36 (C6),
42.58 (C4, C9), 48.30 (C1, C3), 48.46 (OCH3), 69.76
(C5), 216.55 (C2). Found, %: C 73.15; H 8.90.
C11H16O2. Calculated, %: C 73.30; H 8.95.
Anisole (XXXVIa). Yield 95%, bp 153.6–154°C.
13C NMR spectrum, δC, ppm: 54.92 (OCH3), 113.80
(C2, C6), 120.65 (C4), 129.45 (C3, C5), 159.68 (C1).
Found, %: C 77.58; H 7.35. C7H8O. Calculated, %:
C 77.75; H 7.46.
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