Synthesis and properties of functionalized alkylalkoxysilanes

Article abstract of DOI:10.1134/S1070363216080144

A method of chloroalkylalkoxysilanes synthesis scalable to pilot production has been proposed. Morpholinotrialkoxysilanes have been prepared and studied as vulcanizing agents for low-molecular silicone rubbers. The reaction of N-morpholinomethyltrialkoxysilanes with triethanolamine has afforded N-[(silatranyl)-methyl]morpholine; it has been studied by X-ray analysis.

Full text of DOI:10.1134/S1070363216080144

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 8, pp. 1859–1863. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © А.V. Lebedev, R.М. Minas’yan, А.М. Abramkin, V.D. Sheludyakov, N.Е. Kuzmina, А.B. Lebedeva, G.Е. Surikov, V.B. Rybakov,
2
016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86, No. 8, pp. 1321–1326.
Synthesis and Properties of Functionalized Alkylalkoxysilanes
a*
a
a
a
А. V. Lebedev , R. М. Minas’yan , А. М. Abramkin , V. D. Sheludyakov ,
a
a
a
b
N. Е. Kuzmina , А. B. Lebedeva , G. Е. Surikov , and V. B. Rybakov
a
State Research Institute of Chemistry and Technology of Organoelement Compounds,
sh. Entuziastov 38, Moscow, 105118 Russia
*
е-mail: leanvik@yandex.ru
b
Lomonosov Moscow State University, Moscow, Russia
Received January 14, 2016
Abstract—A method of chloroalkylalkoxysilanes synthesis scalable to pilot production has been proposed.
Morpholinotrialkoxysilanes have been prepared and studied as vulcanizing agents for low-molecular silicone
rubbers. The reaction of N-morpholinomethyltrialkoxysilanes with triethanolamine has afforded N-[(silatranyl)-
methyl]morpholine; it has been studied by X-ray analysis.
Keywords: alkyl orthoformate, functionalized alkylalkoxysilane, silicone hardener, silatrane
DOI: 10.1134/S1070363216080144
The alkylalkoxysilanes functionalized at the alkyl
reaction is performed as a one-pot process, by simple
mixing of the reagents, refluxing, and isolation of the
products by distillation. In the case of simplest alkoxy-
silanes (R = Me, Et), the formed gaseous alkyl
chlorides are easily removed and condensed in a trap.
This present work aimed to investigate the possibility
of industrial use of method b to obtained func-
tionalized derivatives of alkylalkoxysilanes and to
point their potential application.
group are among industrial organosilicon monomers.
In the laboratory practice, alkoxysilanes are usually
obtained via the reaction of chlorosilanes with alcohols
in the presence of urea [1] (method a):
1
n
2
R
SiCl4–n + R OH + (NH
2
)
2
CO
1
1
n
2
→
R
Si(OR )4–n + (NH
2
)
2
CO·HCl,
2
A somewhat higher cost of the reagents used in
method b as compared to method a is fully levelled out
1
2
R = H, alkyl, alkenyl; R = alkyl, n = 0–3.
when using expensive chlorosilanes like chloromethyl-
1
However, the industrial-scale application of this
method requires regeneration of urea, utilization of
hydrogen chloride, and removal of residual chlorine,
lowering the overall yield. Therefore, for industrial
production of alkoxysilanes the alternative method (b)
has been proposed, using trialkyl orthoformates instead
of alcohols [2].
trichlorosilane 1a (R = ClCH , n = 1) affording the α-
2
functionalized chloromethyltrialkoxysilanes 2а, 2b
[R = Me (а); Et (b)] in 80% yield via method a and in
2
the higher yield (85% as shown in this work) via
method b. Therefore, taking into account the simplicity
of the equipment design and formation of valuable side
products, the cost-efficiency of the two methods is
practically the same.
Si
Cl + HC(OR)3
Si OR + RCl + HCOOR
Method b was also used by us for the preparation of
alkoxysilanes 3–7 from other industrially available
chlorosilanes (Table 1). The reported results showed
that the orthoformate method was applicable for pilot-
scale production of various alkoxysilanes including
those prepared from expensive chlorosilanes, such as
isocyanate 7. A similar substitution reaction according
Alkyl chlorides and alkyl formates formed along
with the target alkoxysilanes are valuable commercial
products as well, giving another advantage of this
process in the pilot-scale production. The formed
alkoxysilanes do not contain residual chlorine. The
1
859

1
860
LEBEDEV et al.
Table 1. Reaction conditions, yields, and characteristics of methylalkoxysilanes
Orthoformate/ Temperature, Time,
bp, °С
(mmHg)
20
Yield,
%
Chlorosilane
Product
n
D
chlorosilane
°С
h
ClCH
ClCH
ClCH
ClCH
2
2
2
2
SiCl
SiCl
SiCl
3
3
2
3.65
3.02
2.1
90
90
5
ClCH
ClCH
ClCH
ClCH
2
2
2
2
Si(OMe)
Si(OEt)
Si(OMe)
SiMe (OMe) (4)
SiH (5)
3
(2a)
(2b)
Me (3)
156 (753)
52 (4)
1.4070
1.4065
1.4123
1.4310
1.4222
1.4183
1.4265
85
83
87
79
90
81
84
4
4
3
Me
Cl
100
2
140 (755)
117 (749)
61 (746)
195 (744)
75 (3)
SiMe
2
1.3
95
11
2
2
Cl
2
Cl
3
Cl
3
(Me)SiH
2.2
25
Me(MeO)
2
Si(CH
Si(CH
2
2
)
)
3
3
Cl
4.0
95–100
85–95
7
(MeO)
(MeO)
3
Si(CH
Si(CH
2
)
)
3
3
Cl (6)
NCO
4.0
7
3
2
NCO (7)
to method a would be apparently complicated by the
involvement of the isocyanate group in the reaction
with alcohol.
silicone seals, imparting them high adhesion to
different surfaces.
1
1
ClCH
2
Si(OR )
а, 2b
3
+ Et
2
NH → Et
2
NCH
8а, 8b
2 3 2
Si(OR ) + Et NH·HCl
2
The structure and purity of the products were
confirmed by NMR spectroscopy data. The purity of
the final products was 98–99%, allowing to use them
in further syntheses without additional purification.
A drawback of the use of compounds 8а, 8b is their
strong amine smell, imparted also to the hardened
compositions based on polysiloxane rubbers with
terminal hydroxyl groups. This shortage can be
overcome by the use of morpholine derivatives 9а, 9b
prepared by us using the procedure described in [4],
via direct reaction of compounds 2а or 2b with mor-
pholine in the presence of triethylamine.
The chlorine atom in compounds 2а, 2b is readily
replaced with amino group [3]. The formed amino-
methyltrialkoxysilanes, for example 8а, 8b, have
found wide application as efficient hardeners of
O
O
Et N
3
1
1
ClCH Si(OR ) +
(R O) SiCH
N
+ Et N HCl
3
2
3
3
2
HN
2
a, 2b
9a, 9b
Compounds 9а and 9b were liquids sensitive to air
moisture, but they could be distilled under reduced
pressure. Their performance characteristics as
hardeners of silicone rubbers were comparable to those
of compound 8b (widely used in practice under the
exhibited the vulcanization time and the mechanical
properties similar to those based on commercial
hardener 8b. Note that compounds 9а and 9b had no
smell, which is especially important in view of the
household applications or the use in poorly ventilated
rooms. Therefore, compounds 9а, 9b are potentially
suitable for industrial implementation.
“product ADE-3” trademark) and unexpectedly exceeding
those of the earlier studied diazole derivatives (Table 2).
On top of the application as silicon hardener,
compounds 9а and 9b could be used as modifiers of
hydroxyl-containing surfaces like silica or alumina.
Their use as co-reagents for preparation of new organo-
silicon nitrogen-containing resins and synthones for
certain reactions was also attractive.
We used the hardening composition consisting of
polydimethylsiloxane rubber SKTN-G with viscosity
of 16000 сP, ZnO, the simplest titanium chelate
compound as the main adhesive, and a vulcanizing
agent as a model system. Physico-mechanical pro-
perties of the vulcanized compositions were estimated
after 7 days of hardening by measuring their tensile
elastic-strength properties. As follows from Table 2,
the compositions based on hardeners 9а and 9b
For example, the reaction of compounds 9а and 9b
with triethanolamine via the known procedure [7]
afforded silatrane 10.
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SYNTHESIS AND PROPERTIES OF FUNCTIONALIZED ALKYLALKOXYSILANES
1861
Table 2. Characteristics of compositions based on SKTN-G rubber and aminoalkyltrialkoxysilanes
Ultimate tensile
strength of the
vulcanizate, MPa
Time of surface
vulcanization, min
Relative elongation of
the vulcanizate, %
Vulcanizing agent
N,N-Diethylaminomethyltriethoxysilane (8b)
N-Morpholinomethyltrimethoxysilane (9a)
N-Morpholinomethyltriethoxysilane (9b)
15
19
2.1
2.0
2.2
0.7
0.4
0.2
0.4
258
235
245
155
176
164
195
25
а
[
[
[
N-(3,5-Dimethylpyrazolyl)methyl]trimethoxysilane
210
240
360
>480
а
N-(3,5-Dimethylpyrazolyl)ethyl]triethoxysilane
а
N-(Imidazolyl)methyl]trimethoxysilane
а
{β-[N-(Imidazolyl)ethyl]}triethoxysilane
a
Synthesized as described in [5, 6].
pensive chlorosilanes) in pilot-scaled industrial produc-
tion. The N-morpholinomethyltrialkoxysilanes easily
prepared from the chlorinated derivatives demonstrate
high efficiency as hardeners of low-molecular silicon
rubbers and are promising for the industrial use as well
as synthons in organic synthesis.
1
O
N
CH Si(OR )
2 3
9
a, 9b
2
OCH CH2
N(CH CH OH)
3
2
2
O
N
CH SiOCH CH N
2
2
2
_
1
R OH
EXPERIMENTAL
OCH CH2
2
1
10
H NMR spectra were recorded in a CDCl solution
3
using a Bruker AM-360 spectrometer operating at
360.13 MHz. X-ray analysis was performed using a
STOE StadiVari Pilatus-100K (Germany) single-
crystal diffractometer. The data were deposited at the
Cambridge Crystallographic Database Center, CCDC
1440079.
The structure of silatrane 10 (Fig. 1) was deter-
mined by X-ray analysis; its crystal structure data and
refinement parameters are collected in Table 3 and
bond distances and bond angles are collected in
Table 4.
The structure of silatrane 10 was similar to that of
other silatranes [7]. Deviation of Si(1) atom off the
equatorial plane formed by the oxygen atoms (Δ) was
Chloromethyltrimethoxysilane (2a). 570.2
g
(3.1 mol) of chloromethyltrichlorosilane was added
dropwide to 1127.8 g (10.64 mol) of methyl ortho-
formate so that the mixture was slightly boiling. After
addition of chlorosilane, the mixture was heated to 90°С,
kept at that temperature for 5 h, and distilled to afford
0
.209 Å. It has been adopted [7] that the deviation
value reflects the variation of the atom hybridization.
Hence, in molecule 10 hybridization of the silicon
3
1
atom was closer to sp than for the earlier studied N-[β-
449.8 g of compound 2a. Н NMR spectrum, δ, ppm:
(
trimethoxysilyl)ethyl]diazoles and N-[β-(silatranyl)
ethyl]pyrazoles, the Δ for the latter being 0.171–
.192 Å [8, 9]. Note that the only shortened contact
between the H and O atoms of silatranyl fragments of
2.77 s (2H, CH ), 3.58 s (9H, OCH ).
2
3
Compounds 2b–7 were prepared similarly. Reac-
tion conditions, physico-chemical constants, and
product yields are shown in Table 1.
0
2
3A
С31A"
the neighboring molecules (А and А"), O ···H
.49 Å, was observed in the crystal structure of com-
1
2
Chloromethyltriethoxysilane (2b). Н NMR spec-
pound 10, indicative of weak electrostatic inter-
trum, δ, ppm: 1.22 t (9H, 3CH ), 2.77 s (2H, CH ),
3
2
molecular interaction.
3.87 m (6H, OCH2).
1
In summary, substitution of chlorine atoms under
the action of orthoformates is an efficient method
applicable both in laboratory practice and (for ex-
Chloromethyl(methyl)dimethoxysilane (3). Н NMR
spectrum, δ, ppm: 0.25 s (3H, CH ), 2.78 s (2H, CH ),
3.57 s (6H, OCH3).
3
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 8 2016

1
862
LEBEDEV et al.
Fig. 1. General view of the molecule of compound 10.
1
1
Chloromethyl(dimethyl)methoxysilane (4). Н NMR
Dimethoxy(methyl)silane (5). Н NMR spectrum,
δ, ppm: 0.19 s (3H, CH ), 3.56 s (6H, OCH ), 4.53 s
spectrum, δ, ppm: 0.25 s (6H, 2CH ), 2.80 s (2H,
3
3
3
CH ), 3.49 s (3H, OCH ).
(1H, SiH).
2
3
1
(
3-Chloropropyl)trimethoxysilane (6). Н NMR
Table 3. Crystallographic and structure refinement parameters
of compound 10
spectrum, δ, ppm: 0.78 m (2H, CH ), 1.88 m (2H,
2
CH ), 3.54 m (2H, ClCH ), 3.58 s (9H, OCH ).
2
2
3
Parameter
Molecular formula
Value
1
(
3-Isocyanatopropyl)trimethoxysilane (7).
Н
C
11
H
22
N
2
O
4
Si
NMR spectrum, δ, ppm: 0.77 m (2H, CH ), 1.87 m
2
Temperature of the experiment, K
λ, Å
Syngony
Space group
a, Å
295(2)
1.54186
Monoclinic
P2 /n
10.5247(6)
11.3532(5)
11.7857(6)
106.164(4)
1352.59(12)
4
(2H, CH ), 2.86 m (2H, OCNCH ), 3.57 s (9H, OCH ).
2
2
3
Amination of chloromethyl derivatives 2а, 2b.
.5 mol of the corresponding compound 2а, 2b was
0
1
added dropwise at stirring over 1 h to a mixture of 48 g
(
(
0.55 mol) of dry freshly distilled morpholine, 56 g
0.55 mol) of triethylamine, and 100 mL of toluene pre-
b, Å
c, Å
heated to 65°С; then the mixture was heated to 100–
05°С for 15 h. After cooling, the mixture was filtered
β, deg
1
3
V, Å
under nitrogen atmosphere, and the precipitate was
washed with toluene (2 × 25 mL). Vacuum distillation
of the combined filtrate gave compounds 9а, 9b in
Z
3
ρ, g/cm
µ, cm
1.347
1.637
592
–1
8
0% yield, respectively.
F(000)
Crystal size, mm
θ range, deg
3
N-Morpholinomethyltrimethoxysilane (9a). Yield
0.10 × 0.10 × 0.10
4.99/71.89
–12 ≤ h ≤ 12, 0 ≤ k ≤ 13,
2
0
1
8
0%, bp 90°С (5 mmHg), nD = 1.4400. Н NMR
spectrum, δ, ppm: 2.00 s (2H, CH ), 2.44 t (4Н,
2
hkl indices range
СH N), 3.59 s (9H, OCH ), 3.68 t (4Н, CH O).
2
3
2
0
≤ l ≤ 14
Total number of reflections
Independent reflections, Rint
Refined reflections
GООF
2502
2502, 0.0301
2502/163
N-Morpholinomethyltriethoxysilane (9b). Yield
2
0
1
80%, bp 83°С (1 mmHg), nD = 1.4339. Н NMR
spectrum, δ, ppm: 1.23 t (9H, CH ), 1.98 s (2H, CH ),
3
2
0.904
2.46 t (4Н, СH N), 3.67 t (4Н, СH O), 3.85 q (6H,
2
2
R
R
1
/wR
/wR
2
[I > 2σ(I)]
0.0549/0.1397
0.0757/0.1464
0.367/–0.338
OCH2).
1
2
(all reflections)
N-[(Silatranyl]morpholine (10). Equimolar amounts
of compound 9 and triethanolamine were stirred for
3
Δρmax/Δρmin, e/Å
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 8 2016

SYNTHESIS AND PROPERTIES OF FUNCTIONALIZED ALKYLALKOXYSILANES
1863
Table 4. Bond lengths and bond angles in the molecule of compound 10
Bond
Length, Å
Angle
Value, deg
Angle
Value, deg
1
21
31
11
1
21
1
31
11
11
1
13
1
1
1
1
N –C
1.456(4)
1.471(4)
1.474(4)
2.183(2)
1.505(4)
1.422(3)
1.654(2)
1.518(5)
1.428(4)
1.658(2)
1.512(4)
1.418(3)
1.6634(19)
1.894(3)
1.469(4)
1.449(4)
1.471(4)
1.494(5)
1.424(4)
1.419(4)
1.510(5)
C N C
115.3(2)
O Si N
82.90(9)
82.36(10)
83.01(9)
175.88(12)
119.4(2)
111.8(2)
108.1(2)
109.5(3)
110.8(3)
112.3(3)
109.6(2)
111.2(3)
111.6(3)
1
21
1
23
1
N –C
C N C
113.5(3)
O Si N
1
31
1
33
1
N –C
C N C
113.9(3)
O Si N
1
21
1
41
1
1
N –Si
C N Si
104.73(19)
104.06(16)
103.58(17)
106.6(2)
C Si N
1
1
12
31
1
1
42 41
1
C –C
C N Si
N C Si
1
2
13
11
1
1
47 42 41
C –O
C N Si
C N C
1
3
1
1
11 12
47 42 43
O –Si
N C C
C N C
2
1
22
13 12 11
41 42 43
C –C
O C C
108.2(3)
C N C
2
2
23
12 13
1
42 43 44
C –O
C O Si
123.26(17)
106.8(3)
N C C
2
3
1
1
21 22
45 44 43
O –Si
N C C
O C C
3
1
32
23 22 21
46 45 44
C –C
O C C
107.7(3)
C O C
3
2
33
22 23
1
45 46 47
C –O
C O Si
123.8(2)
O C C
3
3
1
1
31 32
42 47 46
O –Si
N C C
106.4(3)
N C C
1
41
33 32 31
Si –C
O C C
109.1(2)
4
1
42
47
43
32 33
1
C –N
C O Si
122.85(18)
118.16(12)
117.93(12)
119.21(12)
100.56(11)
93.98(12)
97.20(11)
4
2
13
1
23
33
33
N –C
O Si O
4
2
13
1
N –C
O Si O
4
3
44
45
23
1
C –C
O Si O
4
4
13
1
41
41
41
C –O
O Si C
4
5
46
23
1
O –C
O Si C
46
47
33
1
C –C
O Si C
8
h at 70°С in the presence of 2 mol % of sodium
5. Sheludyakov, V.D., Viktorov, N.A., Tkachev, A.S., and
Mironov, V.F., Zh. Obshch. Khim., 1977, vol. 47, no. 1,
p. 90.
ethoxide, gradually adding ethanol to the reaction
mixture to avoid its thickening. The formed silatrane
1
Yield 70%, mp 98–100°С. Н NMR spectrum, δ, ppm:
1
3
6
. Mironov, V.F., Sheludyakov, V.D., Viktorov, N.A.,
Ryasin, G.V., and Chizhikova, M.P., Authot’s
Certificate 346306 , 1972, Byull. Izobret., 1972, no. 23.
. Voronkov, M.G. and D’yakov, V.M., Silatrany
0 was crystallized from ethanol and dried in vacuum.
1
.797 s (2H, CH ), 2.453 t (4Н, 2СH N), 2,787 t (6H,
2 2
7
8
СH N) 3.688 t (4Н, 2СH O), 3.754 t (6H, 3CH О).
2
,
2
2
(
Silatranes), Novosibirsk: Nauka, 1978.
. Sheludyakov, V.D., Kuz’mina, N.E., Abramkin, A.M.,
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Cheshkov, D.A., and Storozhenko, P.A., Russ. J. Gen.
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S1070363211120073.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 8 2016