Methylation of phenol and its derivatives with dimethyl carbonate in the presence of Mn2(CO)10, W(CO)6, and Co2(CO)8

Article abstract of DOI:10.1134/S1070428015030070

Aryl methyl ethers were synthesized by reactions of phenol, substituted phenols, and α- and β-naphthols with dimethyl carbonate in the presence of manganese, tungsten, and cobalt carbonyls. Optimal reactant and catalyst ratios and reaction conditions were found to ensure selective formation of aryl methyl ethers.

Full text of DOI:10.1134/S1070428015030070

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 3, pp. 330–334. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © R.I. Khusnutdinov, N.A. Shchadneva, Yu.Yu. Mayakova, 2015, published in Zhurnal Organicheskoi Khimii, 2015, Vol. 51, No. 3,
pp. 348–352.
Methylation of Phenol and Its Derivatives with Dimethyl
Carbonate in the Presence of Mn2(CO)10, W(CO)6, and Co2(CO)8
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 June 26, 2014
Abstract—Aryl methyl ethers were synthesized by reactions of phenol, substituted phenols, and α- and
β-naphthols with dimethyl carbonate in the presence of manganese, tungsten, and cobalt carbonyls. Optimal
reactant and catalyst ratios and reaction conditions were found to ensure selective formation of aryl methyl
ethers.
DOI: 10.1134/S1070428015030070
Aryl methyl ethers constitute an important class of
chemical compounds that are widely used as solvents
and reactants for the preparation of dyes, agro-
chemicals, antioxidants, and polymer stabilizers [1, 2].
The simplest aryl methyl ether, methoxybenzene
(anisole), is a large-scale product which is obtained by
alkylation of phenol with methanol in the presence of
γ-Al2O3. Anisole can also be synthesized by meth-
ylation of phenol with dimethyl sulfate or methyl
halides in the presence of an equimolar amount of
a base [3, 4]. Bomben et al. [5] demonstrated the
possibility for methylation of phenol with a “green
reagent,” dimethyl carbonate. The reaction was carried
out at 90°C (50 h) in the presence of 1.2 equiv of po-
tassium carbonate, and the yield of anisole was 30%.
Alkylation of phenol and its derivatives with dimethyl
carbonate in the presence of metal complex catalysts
was not studied previously.
quantitative formation of anisole in 1 h at 180°C. We
examined the effect of substituents in the substrate
on the conversion and yield of the corresponding
methyl ether. The reactions of o-, m-, and p-cresols 1–3
with dimethyl carbonate in the presence of Mn2(CO)10
at a Mn2(CO)10–cresol–Me2CO3 molar ratio of
3:100:300 (180°C, 1 h) gave methyl ethers 4–6 in 30,
81, and 95% yield, respectively; in addition, metha-
nol and carbon dioxide were formed (Scheme 1).
The yields of 4–6 in the presence of W(CO)6, other
conditions being equal, were 4, 5, and 22%, respec-
tively. In all cases, excess dimethyl carbonate was used
since it acted simultaneously as reagent and solvent.
No transesterification of dimethyl carbonate was
observed.
The results of the reactions of dimethyl carbonate
with phenol derivatives containing two and more
substituents in the benzene ring in the presence of
Mn2(CO)10, W(CO)6, and Co2(CO)8 under the optimal
We have recently found that tungsten and cobalt
carbonyls W(CO)6 and Co2(CO)8 catalyze alkylation of
primary, secondary, and tertiary alcohols with dimethyl
carbonate [6]. The present study was aimed at ex-
tending the scope of this reaction and examining its
general and specific features.
Scheme 1.
OH
OMe
Mn2(CO)10
180°C, 1 h
R1
R2
R1
R2
O
+
–MeOH, –CO2
Tungsten hexacarbonyl catalyzed methylation of
phenol with dimethyl carbonate with formation of
anisole, whereas no reaction occurred in the presence
of Co2(CO)8 [6]. Manganese carbonyl Mn2(CO)10
showed an appreciable catalytic activity in the alkyla-
tion of phenol with dimethyl carbonate; it ensured
MeO
OMe
R3
1–3
R3
4–6
1, 4, R1 = Me, R2 = R3 = H; 2, 5, R1 = R3 = H, R2 = Me;
3, 6, R1 = R2 = H, R3 = Me.
330

METHYLATION OF PHENOL AND ITS DERIVATIVES
331
Alkylation of substituted phenols with dimethyl carbonate in
the presence of metal carbonylsa
conditions are given in table. It is seen that substituted
phenols react with dimethyl carbonate to produce the
corresponding methyl ethers with high selectivity. The
substrate conversion is largely determined by the metal
nature in the catalyst. The most efficient catalyst is
Mn2(CO)10. The nature of substituents in the substrate
does not affect the conversion and yield of methyl
ether to an appreciable extent. 3,4-Dichlorophenol,
3-aminophenol, methyl and 3-hydroxybenzoate reacted
with dimethyl carbonate to afford 3,4-dichloro-1-me-
thoxybenzene, 3-methoxyaniline, and methyl 3-me-
thoxybenzoate in 85, 99, and 99% yield, respectively.
The number of substituents in the phenol molecule
insignificantly affects the yield (see the data for
2,3,4,5,6-pentamethylphenol).
Yield of methyl
Substrate
Catalyst
ether, %
98
30
04
81
05
95
22
99
70
99
56
99
99
99
99
46
72
99
98
99
99
20
90
99
50
02
85
99
99
Phenol
Mn2(CO)10
Mn2(CO)10
W(CO)6
o-Cresol
o-Cresol
m-Cresol
m-Cresol
p-Cresol
p-Cresol
Mn2(CO)10
W(CO)6
Mn2(CO)10
W(CO)6
2,3-Dimethylphenol
2,3-Dimethylphenol
3,4-Dimethylphenol
3,4-Dimethylphenol
3,5-Dimethylphenol
3,5-Dimethylphenol
3,5-Dimethylphenol
2,6-Dimethylphenol
2,6-Dimethylphenol
2,6-Dimethylphenol
2,3,5-Trimethylphenol
2,3,5-Trimethylphenol
2,3,5-Trimethylphenol
2,3,6-Trimethylphenol
2,3,6-Trimethylphenol
2,3,6-Trimethylphenol
Mn2(CO)10
W(CO)6
On the other hand, the position of substituent with
respect to the hydroxy group is significant. In the reac-
tion of 2-propylphenol with dimethyl carbonate, the
substrate conversion was as low as 50%, whereas
2-chlorophenol failed to react with dimethyl carbonate.
Mn2(CO)10
W(CO)6
Mn2(CO)10
W(CO)6
β-Naphthol (7) reacted with dimethyl carbonate in
the presence of Mn2(CO)10, W(CO)6, and Co2(CO)8
(180°C, 1 h) to give 2-methoxynaphthalene (8) in
quantitative yield (Scheme 2).
Co2(CO)8
Mn2(CO)10
W(CO)6
Co2(CO)8
Mn2(CO)10
W(CO)6
Scheme 2.
OH
O
+
MeO
OMe
Co2(CO)8
Mn2(CO)10
W(CO)6
7
[Mn], [W], or [Co]
180°C, 1 h
OMe
+ CO2 + MeOH
Co2(CO)8
99%
2,3,4,5,6-Pentamethylphenol Mn2(CO)10
8
2-Propylphenol
Mn2(CO)10
Mn2(CO)10
Mn2(CO)10
Mn2(CO)10
Mn2(CO)10
The reaction of α-naphthol (9) with (MeO)2CO
catalyzed by Mn2(CO)10 and W(CO)6 was accom-
panied by partial isomerization of 9 into β-naphthol
(7), and the products were isomeric methyl natphthyl
ethers 8 and 10. The conversion of 9 in the presence
of Co2(CO)8 was considerably lower (42%), but no
isomerization was observed (Scheme 3).
2-Chlorophenol
3,4-Dichlorophenol
3-Aminophenol
Methyl 3-hydroxybenzoate
a
Ratio catalyst–phenol–(MeO)2CO 3:100:300, 180°C, 1 h.
In the reaction with a dihydric phenol, resorcinol
(11), we obtained a mixture of exhaustive and partial
methylation products 12a and 12b (Scheme 4). Hydro-
quinone (13) reacted with dimethyl carbonate in
a similar way. Neither resorcinol (11) nor hydro-
quinone (13) reacted with dimethyl carbonate in the
presence of cobalt carbonyl. Unlike 11 and 13,
pyrocatechol failed to react with dimethyl carbonate,
regardless of the catalyst (whether manganese,
tungsten, or cobalt carbonyl was used), presumably
because of chelation of the metal atom in the catalyst.
The structure of the isolated compounds was de-
termined by spectral methods, as well as by comparing
their properties with those of authentic samples and
published data [7–10].
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KHUSNUTDINOV et al.
332
Scheme 3.
OMe
Mn2(CO)10
~100%
+
8
OH
10, 89%
11%
O
W(CO)6
90%
180°C, 1 h
+
7
+
8
+
10
MeO
OMe
21%
8%
71%
9
Co(CO)8
42%
10
Scheme 4.
OMe
OMe
Mn2(CO)10
+
OH
97%
O
OMe
OH
180°C, 1 h
+
12a
8 : 1
12b
MeO
OMe
W(CO)6
65%
OH
12a + 12b
11
8 : 1
OMe
OMe
Mn2(CO)10
~100%
+
OH
O
180°C, 1 h
OMe
OH
+
MeO
OMe
14a
1 : 0.8 14b
W(CO)6
72%
OH
14a + 14b
13
1 : 3.5
EXPERIMENTAL
General procedure for the alkylation of phenols
with dimethyl carbonate. A 17-mL stainless steel
high-pressure micro reactor was charged with 3 mmol
of Mn2(CO)10, W(CO)6, or Co2(CO)8, 100 mmol of
the corresponding phenol, and 300 mmol of dimethyl
carbonate, and the reactor was hermetically closed and
heated for 1 h at 180°C. The reactor was then cooled to
room temperature and opened, and the mixture was
filtered through a layer of alumina. Unreacted dimethyl
carbonate was distilled off, and the residue was
distilled under atmospheric or reduced pressure or
recrystallized from ethanol.
The H and 13C NMR spectra were recorded on
a Bruker Avance-400 spectrometer at 400.13 and
100.62 MHz, respectively, using CDCl3 as solvent.
The mass spectra were obtained on a Shimadzu
GCMS-QP2010Plus instrument (SPB-5 capillary col-
umn, 30 m×0.25 mm, carrier gas helium, oven tem-
perature 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). The ele-
mental compositions were determined on a Carlo Erba
1106 analyzer. The progress of reactions and the purity
of products were monitored by GLC on Shimadzu
GC-9A and GC-2014 instruments (2-m×3-mm column
packed with 5% 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).
1
Anisole. Yield 98%, bp 153.6–154°C [6].
1-Methoxy-2-methylbenzene (4). Yield 30%,
bp 170–171°C. 13C NMR spectrum, δC, ppm: 16.02
(CH3), 55.32 (OCH3), 110.23 (C6), 120.28 (C4), 126.55
(C2, C5), 157.64 (C1). Found, %: C 78.54; H 8.19.
C8H10O. Calculated, %: C 78.65; H 8.25.
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METHYLATION OF PHENOL AND ITS DERIVATIVES
333
1-Methoxy-3-methylbenzene (5). Yield 81%,
130.45 (C4), 136.15 (C3, C5), 154.68 (C1). Found, %:
C 80.74; H 10.12. C12H18O. Calculated, %: C 80.85;
H 10.18.
13
bp 75.9–76°C (30 mm). C NMR spectrum, δC, ppm:
21.76 (CH3), 55.37 (OCH3), 110.72 (C6), 114.68 (C2),
121.44 (C4), 129.18 (C5), 139.47 (C3), 159.52 (C1).
Found, %: C 78.49; H 8.21. C8H10O. Calculated, %:
C 78.65; H 8.25.
1-Methoxy-2-propylbenzene. Yield 50%, bp 82–
83°C (14 mm). 13C NMR spectrum, δC, ppm: 14.45
(CH3), 23.42 (CH2), 32.17 (CH2), 55.32 (OCH3),
110.62 (C6), 120.76 (C4), 126.58 (C5), 129.96 (C3),
131.05 (C2), 157.74 (C1). Found, %: C 79.87; H 9.32.
C10H14O. Calculated, %: C 79.96; H 9.39.
1-Methoxy-3-methylbenzene (6). Yield 95%,
bp 173.5–174°C. 13C NMR spectrum, δC, ppm: 20.48
(CH3), 54.62 (OCH3), 113.92 (C2, C6), 129.75 (C4),
129.90 (C3, C5), 157.88 (C1). Found, %: C 78.55;
H 8.19. C8H10O. Calculated, %: C 78.65; H 8.25.
1-Chloro-2-methoxybenzene. Yield 2%. Found, %:
C 58.85; H 4.92; Cl 24.78. C7H7ClO. Calculated, %:
C 58.97; H 4.95; Cl 24.86.
1-Methoxy-2,3-dimethylbenzene. Yield 99%,
13
bp 95.8–96°C (30 mm). C NMR spectrum, δC, ppm:
1,2-Dichloro-4-methoxybenzene. Yield 85%,
bp 88–89°C (7 mm). 13C NMR spectrum, δC, ppm:
56.94 (OCH3), 114.69 (C5), 115.53 (C3), 124.49 (C1),
131.33 (C6), 131.62 (C2), 158.52 (C4). Found, %:
C 47.25; H 3.39; Cl 39.95. C7H6Cl2O. Calculated, %:
C 47.49; H 3.42; Cl 40.05.
11.99 (CH3), 20.56 (CH3), 55.83 (OCH3), 110.02 (C6),
122.43 (C4), 124.78 (C2), 128.74 (C5), 137.70 (C3),
157.36 (C1). Found, %: C 79.29; H 8.82. C9H12O.
Calculated, %: C 79.37%; H 8.88.
1-Methoxy-3,4-dimethylbenzene. Yield 99%,
bp 72.8–73°C (8 mm). 13C NMR spectrum, δC, ppm:
19.05 (CH3), 19.75 (CH3), 54.20 (OCH3), 110.92 (C6),
115.65 (C2), 128.30 (C4), 130.44 (C5), 137.48 (C3),
157.43 (C1). Found, %: C 79.25; H 8.84. C9H12O.
Calculated, %: C 79.37%; H 8.88.
3-Methoxyaniline. Yield 99%, bp 117–118°C
13
(9 mm). C NMR spectrum, δC, ppm: 55.06 (OCH3),
101.02 (C2), 103.98 (C4), 107.96 (C6), 130.11 (C5),
147.72 (C1), 160.76 (C3). Found, %: C 68.12; H 7.31;
N 11.29. C7H9NO. Calculated, %: C 68.29; H 7.31;
N 11.38.
1-Methoxy-3,5-dimethylbenzene. Yield 99%,
bp 77–78°C (14 mm). 13C NMR spectrum, δC, ppm:
21.36 (2C, CH3), 111.85 (C2, C6), 122.50 (C4), 139.34
(C3, C5), 159.92 (C1). Found, %: C 79.27; H 8.85.
C9H12O. Calculated, %: C 79.37; H 8.88.
Methyl 3-methoxybenzoate. Yield 99%, bp 96–
97°C (3 mm). 13C NMR spectrum, δC, ppm: 52.42
(OCH3), 56.16 (OCH3), 113.93 (C2), 119.15 (C4),
121.86 (C6), 129.19 (C5), 131.70 (C1), 159.42 (C3),
166.42 (C=O). Found, %: C 64.95; H 6.03. C9H10O3.
Calculated, %: C 65.05; H 6.07.
1-Methoxy-2,6-dimethylbenzene. Yield 99%,
bp 74–75°C (20 mm). 13C NMR spectrum, δC, ppm:
15.49 (2C, CH3), 58.88 (OCH3), 123.32 (C4), 128.24
(C3, C5), 130.20 (C2, C6), 156.65 (C1). Found, %:
C 79.31; H 8.85. C9H12O. Calculated, %: C 79.37;
H 8.88.
2-Methoxynaphthalene (8). Yield 99%, mp 73–
74°C (from EtOH). 13C NMR spectrum, δC, ppm:
55.50 (OCH3), 106.69 (C1), 119.15 (C3), 123.72 (C6),
124.75 (C8), 125.68 (C5), 127.01 (C7), 127.55 (C4),
130.12 (C10), 135.77 (C9), 157.72 (C2). Found, %:
C 83.42; H 6.34. C11H10O. Calculated, %: C 83.51;
H 6.37.
1-Methoxy-2,3,5-trimethylbenzene. Yield 99%,
bp 84.5–85°C (7 mm). 13C NMR spectrum, δC, ppm:
11.60, 20.03, 21.38 (CH3); 110.52 (C6), 119.95 (C2),
124.92 (C4), 137.32 (C3), 137.54 (C5), 157.43 (C1).
Found, %: C 79.87; H 9.35. C10H14O. Calculated, %:
C 79.96; H 9.39.
1-Methoxynaphthalene (9). Yield 89%, bp 109–
110°C (4 mm). 13C NMR spectrum, δC, ppm: 55.32
(OCH3), 103.64 (C2), 120.12 (C4), 121.99 (C8), 125.78
(C9), 127.14 (C7), 127.35 (C5), 127.92 (C3), 128.36
(C6), 134.70 (C10), 155.32 (C1). Found, %: C 83.45;
H 6.32. C11H10O. Calculated, %: C 83.51; H 6.37.
1-Methoxy-2,3,6-trimethylbenzene. Yield 99%,
bp 80.5–81°C (8 mm). 13C NMR spectrum, δC, ppm:
13.80, 15.84, 19.86 (CH3); 124.32 (C4), 125.54 (C2),
127.11 (C6), 128.45 (C5), 135.25 (C3), 156.95 (C1).
Found, %: C 79.89; H 9.37. C10H14O. Calculated, %:
C 79.96; H 9.39.
1,3-Dimethoxybenzene (12a). Yield 86%, bp 78–
79°C (6 mm). 13C NMR spectrum, δC, ppm: 55.20
(OCH3), 100.42 (C2), 106.09 (C4, C6), 129.84 (C5),
160.85 (C1, C3). Found, %: C 69.34; H 7.25. C8H10O2.
Calculated, %: C 69.54; H 7.30.
1-Methoxy-2,3,4,5,6-pentamethylbenzene. Yield
99%, bp 110–111°C (4 mm). 13C NMR spectrum, δC,
ppm: 11.30, 16.52, 17.16 (CH3); 121.84 (C2, C6),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 3 2015

KHUSNUTDINOV et al.
334
2. Beutel, T., J. Chem. Soc., Faraday Trans., 1998, vol. 94,
3-Methoxyphenol (12b). Yield 14%, bp 113–114°C
13
p. 985.
(5 mm). C NMR spectrum, δC, ppm: 55.22 (OCH3),
101.67 (C2), 106.52 (C4), 108.16 (C6), 130.25 (C5),
156.73 (C1), 160.27 (C3). Found, %: C 67.66; H 6.47.
C7H8O2. Calculated, %: C 67.73; H 6.50.
3. Tundo, P. and Selva, M., Acc. Chem. Res., 2002, vol. 35,
p. 706.
4. Ando, T., Yamawaki, J., Kawate, T., Sumi, S., and
Hanafusa, T., Bull. Chem. Soc. Jpn., 1982, vol. 55,
p. 2504.
1,4-Dimethoxybenzene (14a). Yield 56%, bp 85–
86°C (10 mm). 13C NMR spectrum, δC, ppm: 55.60
(OCH3), 114.82 (C2, C3, C5, C6), 154.16 (C1, C4).
Found, %: C 69.42; H 7.27. C8H10O2. Calculated, %:
C 69.54; H 7.30.
4-Methoxyphenol (14b). Yield 44%, mp 56–57°C
(from EtOH). 13C NMR spectrum, δC, ppm: 55.75
(OCH3), 115.35 (C3, C5), 116.39 (C2, C6), 150.72 (C1),
153.93 (C4). Found, %: C 67.62; H 6.46. C7H8O2. Cal-
culated, %: C 67.73; H 6.50.
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