(4-Methoxyphenyl)amine and its derivatives in the synthesis of O-silylurethanes, ureas, and formamides

Article abstract of DOI:10.1134/S1070363217070143

Reactions of (4-methoxyphenyl)amine and its trimethylsilyl derivative with organosilicon isocyanates and phenylisocyanate have been studied. (4-Methoxyphenyl)formamide was first synthesized by the reaction of (4-methoxyphenyl)amine with ethyl formate. The structure of trimethylsilyl(4-methoxyphenyl)-carbamate and N-(4-methoxyphenyl)formamide was determined by X-ray diffraction (XRD) analysis.

Full text of DOI:10.1134/S1070363217070143

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 7, pp. 1531–1535. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © L.О. Belova, М.V. Pletneva, N.А. Golub, А.А. Korlyukov, А.D. Kirilin, А.V. Petrogradskii, 2017, published in Zhurnal Obshchei
Khimii, 2017, Vol. 87, No. 7, pp. 1138–1142.
(4-Methoxyphenyl)amine and Its Derivatives
in the Synthesis of О-Silylurethanes, Ureas, and Formamides
L. О. Belova*, М. V. Pletneva, N. А. Golub,
А. А. Korlyukov, А. D. Kirilin, and А. V. Petrogradskii
Moscow Technological University (Institute of Fine Chemical Technologies),
pr. Vernadskogo 78, Moscow, 119571 Russia
*e-mail: belova.lya@inbox.ru
Received March 2, 2017
Abstract―Reactions of (4-methoxyphenyl)amine and its trimethylsilyl derivative with organosilicon
isocyanates and phenylisocyanate have been studied. (4-Methoxyphenyl)formamide was first synthesized by
the reaction of (4-methoxyphenyl)amine with ethyl formate. The structure of trimethylsilyl(4-methoxyphenyl)-
carbamate and N-(4-methoxyphenyl)formamide was determined by X-ray diffraction (XRD) analysis.
Keywords: O-silylurethanes, ureas, formamides, trimethylsilylisocyanate, (3-isocyanato-propyl)(trimethoxy)silane
DOI: 10.1134/S1070363217070143
Organic and organosilicon heterocumulenes are
widely used for preparation of linear and heterocyclic
compounds, drugs, vulcanizing agents, and Si(C)(N)-
ceramics [1–3]. It was shown earlier [4] that, unlike
trimethylsilyl derivatives of aniline, N-(4-methoxy-
phenyl)-1,1,1-trimethylsilylamine 1 readily reacted
with carbon dioxide due to the presence in the
molecule of an electron-donor substituent increasing
its nucleophilicity (Scheme 1). The formed О-silyl-
urethane 2, unlike its analogs of the type RNHC(O)·
OSiMe3, turned out to be stable in air; its structure was
determined by XRD analysis (Fig. 1). Principal struc-
tural parameters of compound 2 are given in Table 1.
unknown ureas (Scheme 2). Therewith it was found for
organosilicon isocyanates that the synthesis of ureas is
possible only if the isocyanate group is in the carbo-
position to the silicon atom. The use of trimethyl-
silylisocyanate 3, as distinct from phenylisocyanate,
does not lead to the formation of urea 4 even when
using the catalyst tin bis(2-ethylhexanoate) (Scheme 2).
The type of the starting reagents, as well as the
composition and the structure of the obtained urea 4
allow assuming that the reaction proceeds via the
formation of its N-trimethylsilyl analog 5, which under
the conditions of the reaction is readily desililated to
urea 4.
The replacement of carbon dioxide in this reaction
by other heterocumulenes, organosilicon isocyanates
or phenylisocyanate, allowed to synthesize the earlier
Unlike trimethylsilylisocyanate, (3-isocyanato-
propyl)(trimethoxy)silane reacts with (4-methoxy-
phenyl)-1,1,1-trimethylsilylamine 1 without a catalyst
Scheme 1.
O
PhN(R)SiMe3 + CO2
PhN(R)COSiMe3
R = H, Et, Ph.
O
MeO
NHCOSiMe3
MeO
NHSiMe3 + CO2
2
1
1531

1532
BELOVA et al.
Note also that, as in the case of urea 6, the reaction
of (3-isocyanatopropyl)(trimethoxy)-silane with (4-
methoxyphenyl)amine 7 was not followed by intra-
molecular condensation of compound 8 with evolution
of methanol.
(4-Methoxyphenyl)amine 7 easily reacts with ethyl
formate leading to the preparation of (4-methoxy-
phenyl)formamide 11 for the first time (Scheme 5).
The composition and structure of formamide 11 were
Fig. 1. General view of the molecule of trimethylsilyl(4-
methoxyphenyl)carbamate 2 in the crystal.
1
proved by the data of IR, H NMR spectroscopy,
elemental analysis, and XRD analysis (Fig. 2). The
main crystallographic parameters and parameters of
refinement are summarized in Tables 2, 3.
(Scheme 3). The process is not followed by the
expected intramolecular desilylation of urea 6, but
stops at the stage of its formation. Since the removal of
the silicon atom from the isocyanate group in this
reaction leads to the formation of urea 6, the inactivity
of trimethylsilylisocyanate in the analogous process
(Scheme 2) is, apparently, due to the presence of dp–pp
conjugation in trimethylsilylisocyanate.
Therefore, investigation of the reactions of (4-meth-
oxyphenyl)amine and its trimethylsilyl derivative with
organosilicon heterocumulenes and phenylisocyanate
allowed to synthesize earlier unknown ureas and
carbamate. No intramolecular desilylation was found
both in the case of simultaneous presence of
ethoxysilyl and NH groups in the molecule, and in the
case of ethoxysilyl and NSiMe3 groups. The structure
of trimethyl(4-methoxyphenyl)carbamate and N-(4-
methoxyphenyl)formamide was studied by XRD
analysis.
The use of (4-methoxyphenyl)amine 7 in the afore-
studied reactions not only does not change the
character of the process in the case of (3-isocyanato-
propyl)(trimethoxy)silane, but also opens the
possibility to use trimethylsilylisocyanate. The formed
urea 9, as trimethylsilylurea 5, is readily desilylated
with the formation of urea 10 (Scheme 4).
EXPERIMENTAL
IR spectra were taken on a Specord IR-75 and
Nicolet 7600 instruments. H NMR spectra were re-
Table 1. Principalbondlengths and bond angles in the mole-
cule of trimethylsilyl(4-methoxyphenyl)-carbamate 2
1
corded on a Bruker DRX400 spectrometer (400 MHz)
in benzene-d6 or CDCl3. All reagents and solvents
were thoroughly dried and purified by distillation prior
to use. All synthetic operations, isolation, and sampling
for analysis were done in an atmosphere of dry
nitrogen.
Bond
d, Å
Bond angle
C9Si1C11
C10Si1C9
ω, deg
109.90(8)
110.62(9)
О1–С7
О2–С7
О3–С4
О3–С8
Si1–O2
Si1–C9
Si1–C10
Si1–C11
N1–H1
N1–C1
N1–C7
C1–C2
C1–C6
C2–C3
C3–C4
C4–C5
1.2236(18)
1.3436(18)
1.3763(19)
1.425(2)
C10 Si1C11 114.49(8)
C7O2Si1
C4O3C8
C1N1H1
C7N1C1
C2C1N1
O2Si1C9
O2Si1C10
O2Si1C11
O1C7O2
O1C7N1
O2C7N1
C2C3C4
121.01(10)
116.89(15)
117.40
XRD analysis was performed on a Bruker SMART
APEX II diffractometer (MoKα, λ 0.71073 Å, ω-
scanning) at 120 K. The structure was solved by the
direct method and refined by the least-squares method
in an anisotropic full-matrix approximation with
respect to F2hkl. Hydrogen atoms were localized from
difference Fourier syntheses of electronic density and
refined in an isotropic approximation. All calculations
were done using SHELX-2-14 [5] and OLEX2
software [6].
1.7053(12)
1.8544(17)
1.8524(18)
1.8565(17)
0.8800
125.25(13)
118.09(13)
102.92(7)
109.84(7)
108.42(7)
122.99(14)
125.51(14)
111.49(12)
119.57(15)
1.4227(19)
1.3513(19)
1.391(2)
1.392(2)
Trimethylsilyl(4-methoxyphenyl)carbamate (2).
Carbon dioxide was bubbled through 3.2 g N-(4-
methoxyphenyl)-1,1,1-trimethylsilylamine 1 at 50°С
for 3 h. 3.89 g (99%) of compound 2 was obtained, mp
1.395(2)
1.388(2)
1.391(2)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017

4-METHOXYPHENYL)AMINE AND ITS DERIVATIVES
1533
Scheme 2.
O
SiMe3
SiMe3
Me3SiN
C
O, cat
MeO
MeO
NHCN
3
4
MeO
NHSiMe3
O
PhN
C
O
1
NHCNHPh
O
Ph
1 + PhN
C
O
4
MeO
NHCN
SiMe3
5
Scheme 3.
MeO
NHSiMe3
O
(CH2)3Si(OMe)3
SiMe3
1
MeO
NHCN
+
(MeO)3Si(CH2)3N
C
O
6
O
CH2CH2
MeO
NHCN
Si CH2
OMe
MeO
Scheme 4.
O
(MeO)3Si(CH2)3N
C
O
MeO
MeO
NHCNH(CH2)3Si(OMe)3
8
MeO
NH2
O
Me3SiN
C
O
7
NHCNHSiMe3
9
O
MeO
NHCNH2
10
Scheme 5.
O
O
MeO
NHCH
MeO
NH2 + EtOCH
_EtOH
11
10
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017

1534
BELOVA et al.
Table 2. Principal bond lengths and bond angles in the
molecule of N-(4-methoxyphenyl)formamide 11
Bond
О1–С7
О2–С4
О2–С8
N1–H1
N1–C1
N1–C7
C1–C2
C1–C6
C2–C3
C3–C4
C4–C5
C5–C6
d, Å
Bond angle
C4O2C8
C1N1H1
C7N1H1
C7N1C1
C2C1N1
C2C1C6
C6C1N1
O1C7N1
ω, deg
116.83(13)
116.8
1.2282(19)
1.3699(18)
1.4307(19)
0.88
116.8
126.45(13)
118.34(13)
119.47(13)
122.16(12)
126.26(14)
1.4197(18)
1.344(2)
1.3937(19)
1.3992(19)
1.393(2)
1.396(2)
1.393(2)
1.387(2)
Fig. 2. General view of the molecule of N-(4-methoxy-
phenyl)formamide 11 in the crystal.
C 50.97; H 8.05; N 6.99.
N-(4-Methoxyphenyl)-N'-[3-(trimethoxysilyl)-
propyl]urea (8). To the solution of 6.85 g of (4-me-
Table 3. Principal crystallographic data and parameters of
refinement of structures 2 and 11
Parameter
Empirical formula
Molecular mass
Space group
a, Å
2
11
53–54°С. IR spectrum, ν, cm–1: 3358 (NH), 2955
(CH), 1670 (C=О). H NMR spectrum, δ, ppm: 0.33 s
(9H, SiCH3), 3.24 s (3H, OCH3), 5.99 br.s (1H, NH),
6.70 d (2H, CH), 7.24 d (2Н, СН). Found, %: C 55.22;
H 7.15; N 5.83. C11H17NО3Si. Calculated, %: C 55.20;
H 7.16; N 5.85.
C11H17NО3Si
239.34
C8H9O2N
151.16
1
P212121
Pna21
5.2006(2)
10.3761(5)
23.6620(11)
1276.85(10)
10.5960(7)
7.6688(5)
9.2519(6)
751.80(9)
b, Å
c, Å
N-(4-Methoxyphenyl)-N'-phenylurea (4). To 3.8 g
of N-(4-methoxyphenyl)-1,1,1-trimethylsilylamine 1
2.32 g of phenylisocyanate was added at stirring. After
filtration, 4.51 g (95.7%) of compound 5 was obtained,
mp 190–191°С (mp 189–190°С [7]). IR spectrum, ν,
Volume of unit cell, Å3
Z
4
4
Density, g/cm3
Extinction coefficient, mm–1
F(000)
1.245
0.177
512
1.336
0.097
320
1
cm–1: 3320 (NH), 1640 (С=O). Н NMR spectrum, δ,
ppm: 3.83 s (3H, OCH3), 5.25 br.s ( 2H, NH), 6.8 m
(2H, CH), 6.85 d (2H, CH), 7.05 t (1H, CH), 7.12 d
(2H, CH), 7.51 d (2H, CH). Found, %: С 69.37; Н
5.79; N 11.52. C14H14N2O2. Calculated, %: С 69.41; Н
5.82; N 11.56.
Crystal size, mm
2θmin, 2θmax
0.25×0.25×0.39 0.24×0.29×0.38 mm3
1.72, 30.67
17208
3.28°, 31.53°
9945
Total reflections
Independent reflections 3650 [0.0273] 2516 [0.0210]
[Rint]
N'-(4-Methoxyphenyl)-N-[3-(trimethoxysilyl)propyl]-
N-(trimethylsilyl)urea (6). A mixture of 5 g of N-(4-
methoxyphenyl)-1,1,1-trimethylsilylamine 1 and 5.26 g
of (3-isocyanatopropyl)-(trimethoxy)silane was kept at
95°С for 8.5 h, then distilled in a vacuum. Yield 10.05 g
Reflections with I > 2σ(I)
Refined parameters
GOF
3947
149
2350
101
1.043
0.0308
1.059
0.0420
20
R1, [for reflections with
I >2σ(I)]
(98%), bp 63–64°С (2 mmHg), nD 1.4900. IR spec-
trum, ν, cm–1: 3240 (NH), 1620 (С=O). 1Н NMR spec-
trum, δ, ppm: 0.16 s (9H, SiСH3), 0.59 t (2Н, SiCH2),
1.59 m (2Н, CH2CH2), 3.19 m (2Н, NCH2), 3.50 s (9Н,
SiOCH3), 3.81 s (3H, СOCH3), 4.25 br.s (1H, NH),
6.88 d (2Н, CH), 6.96 m (2Н, CH). Found, %: C
50.99; H 8.01; N 6.87. C17H32N2О5Si2. Calculated, %:
wR2 (for all independent
reflections)
0.0813
0.1143
ρ
min/ρmax, e Å3
–0.152/0.327
0.54(4)
–0.184/0.298
Parameter of absolute
structure
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017

4-METHOXYPHENYL)AMINE AND ITS DERIVATIVES
1535
thoxyphenyl)amine 7 in 30 mL of heptane 11.42 g of
(3-isocyanatopropyl)(trimethoxy)silane was added at
stirring. The reaction mass was stirred without heating
for 8.5 h. The precipitate was filtered off and dried in a
vacuum. Yield 18.01 g (98.6%), mp 58.2–59.3°С. IR
spectrum, ν, cm–1: 3220 (N–H), 1640 (C=O). 1Н NMR
spectrum, δ, ppm: 0.64 t (2H, SiCH2), 1.61 m (2H,
CH2CH2), 3.22 q (2H, NCH2), 3.55 s (9H, SiOСН3),
3.80 s (3H, СOCH3), 4.85 br.s (1H, NH), 6.21 br.s
(1H, NH), 6.87 d (2H, CH), 7.18 d (2H, CH). Found:
%: С 51.16; Н 7.39; N 8.48. C14H24N2O5Si1. Cal-
culated, %: С 51.20; Н 7.37; N 8.53.
(С=O). 1Н NMR spectrum, δ, ppm: 3.25 s (3Н, OCH3),
6.22 br.s (1Н, NH), 6.71 d (2H, CH), 7.43 d (2H, СH),
7.82 s (1H, CH). Found, %: С 63.55; Н 5.95; N 9.25.
C8H9NO2. Calculated, %: С 63.56; Н 6.00; N 9.27.
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N-(4-Methoxyphenyl)urea (10). A mixture of 7 g
of (4-methoxyphenyl)amine 7 and 6.55 g of tri-
methylsilylisocyanate was kept at 60°C for 12.5 h. The
precipitate was filtered off and crystallized from
chloroform. Yield 8.97 g (95%), mp 166–167°С (mp
166–167°С [8]). IR spectrum, ν, cm–1: 3470 (NH),
1
3337 and 3302 (NH2), 1648 (С=O), 1592 (NH2). Н
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(2Н, NH2) 6.83 d (2H, CH), 7.10 br.s (1H, NH), 7.26 d
(2H, СH). Found: %: С 57.81; Н 6.07; N 16.81.
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added at stirring. The reaction mass was heated with
condensation trap to complete end of ethanol evolu-
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from hexane. Yield 11.04 g (90%), mp 76–78°С. IR
spectrum, ν, cm–1: 3243 (NH), 3190 (СH), 1652
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017