Reactivity of heterocyclic α-aminomethylsilanes with alcohols

Article abstract of DOI:10.1007/s10593-021-02910-w

[Figure not available: see fulltext.] Alkoxylation of N-substituted heterocyclic aminomethylsilyl moieties was studied using primary and tertiary alcohols. The reaction of 4-(silylmethyl)morpholine and 1-(silylmethyl)azepane under catalyst- and solvent-free conditions leads to the formation of dialkoxy- and trialkoxyaminomethylsilyl derivatives. The methanolysis of 4-(silylmethyl)morpholine resulted in trimethoxyaminomethylsilane formation as the main product and two byproducts, i.e., tetramethoxysilane and N-methylmorpholine.

Full text of DOI:10.1007/s10593-021-02910-w

DOI 10.1007/s10593-021-02910-w
Chemistry of Heterocyclic Compounds 2021, 57(3), 320–324
SHORT COMMUNICATION
Reactivity of heterocyclic α-aminomethylsilanes with alcohols
Krzysztof Pypowski1*, Mariusz Mojzych1
1 Faculty of Natural Science, Siedlce University of Natural Sciences and Humanities,
54 3 Maja St., Siedlce 08-110, Poland; e-mail: pypowski@uph.edu.pl
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2021, 57(3), 320–324
Submitted March 20, 2020
Accepted after revision August 20, 2020
Alkoxylation of N-substituted heterocyclic aminomethylsilyl moieties was studied using primary and tertiary alcohols. The reaction
of 4-(silylmethyl)morpholine and 1-(silylmethyl)azepane under catalyst- and solvent-free conditions leads to the formation of dialkoxy- and
trialkoxyaminomethylsilyl derivatives. The methanolysis of 4-(silylmethyl)morpholine resulted in trimethoxyaminomethylsilane formation
as the main product and two byproducts, i.e., tetramethoxysilane and N-methylmorpholine.
Keywords: aminomethylalkoxysilane, aminomethylsilane, dehydrocondensation, solvent-free.
The chemistry of compounds with the N–CH2–Si frame-
work is a rapidly growing area of organosilicon chemistry1
and it is also the subject of many publications concerning
α-silicon effect2 and its use in the design of new and more
reactive α-aminomethylsilanes.3,4 Their specific chemical
nature is the result of Si and N atoms connection to the same
methylene group.2a,5 An amino group present in α-position
increases the reactivity of Si–O bonds, particularly in
reactions with nucleophiles.6 The interactions of this type
of organosilicon compounds are called α-effect.7 α-Amino-
methylsilanes are used in the industrial production of
polymers, cosmetics,8,9 and some of the derivatives found
their application in the synthesis of new compounds with
anticancer, neurotropic, or antibacterial activity.10,11 These
compounds are convenient substrates for the synthesis of
hypercoordinated organosilicon derivatives such as five-
coordinated silicon compounds: silatranes12 and zwitter-
ionic spirocyclic λ5 Si-silicates with an SiX4C (X = O or S)
skeleton.13
and organocatalysts1d,20b in the reaction of primary, secondary,
and tertiary silanes with aliphatic and aromatic alcohols is
the subject of many present studies. Such catalytic
processes are called dehydrogenative coupling and can be
selectively realized in the homo- and heterogeneous media.21
The purpose of this paper is to investigate the ability of
aminoalkylsilanes, with general formula R2NCH2SiH3, to
undergo dehydrogenative coupling with alcohols in catalyst-
and solvent-free conditions. It is known that the reactivity
of aminoalkylsilanes Me2N(CH2)nSiRH2 with alcohols
decreases with the increase of quantity of methylene groups
between N and Si atoms.17 To date, only a few examples of
hydrosilane alcoholysis without the use of catalysts and
solvents were described in the literature.17
For the reactivity study of α-aminomethylsilanes with
primary and tertiary alcohols, two silanes 1 and 2 with
aminoheterocyclic moiety were selected as model substrates.
Morpholin-4-ylmethylsilane (1) and azepan-4-ylmethyl-
silane (2) were obtained in the reduction of triethoxysilanes
with LiAlH4 in methyl t-butyl ether (MTBE) or Et2O
furnishing silanes 1 and 2 in high yields of 96% and 94%,
respectively (Scheme 1).22,23 The structures of both
obtained aminomethylsilanes 1 and 2 were confirmed by
1H, 13C NMR and mass spectra.
The most convenient method for the synthesis of tri-
alkoxy-α-aminoalkylsilane derivatives is based on the cata-
lyzed or noncatalyzed reaction of amine with haloalkyl-
trialkoxysilanes (R3SiCH2X), in which R is alkoxy group
and X is Br or Cl atom.14 Another group of silane
derivatives are aminomethylhydrosilanes obtained by
reduction of trihalo- or trialkoxysilane derivatives.15
Scheme 1
The reaction of hydrosilanes with alcohols usually occurs
in the presence of alkaline16 or acid catalysts,17 as well as in
the presence of numerous metal salts.18 Moreover, the use of
transition metal complexes,19 simple inorganic compounds,20
0009-3122/21/57(3)-0320©2021 Springer Science+Business Media, LLC
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Chemistry of Heterocyclic Compounds 2021, 57(3), 320–324
Scheme 3
First, the reaction of the obtained morpholin-4-ylmethyl-
silane (1) with an excess of anhydrous MeOH was
investigated at 0–5°C within 5 h. The progress of the
reaction was monitored by spectroscopic methods and was
indicated by the disappearance of the signal of SiH3 group
protons at 3.58 ppm. Analysis of the reaction mixture by
GC/MS confirmed the formation of 4-[(trimethoxysilyl)-
methyl]morpholine (3), N-methylmorpholine (4), and tetra-
methoxysilane (5) during the process (Scheme 2). Thus,
silane 3 was the major product obtained in good yield of
71% (2 equiv of MeOH) or 90% (3 equiv of MeOH), while
N-methylmorpholine (4) and tetramethoxysilane (5) were
isolated in equal molar ratio with 14.5 and 5.5% yields,
respectively.
cleavage of the Si–C bond in the formed silane 3, especially
in the case of MeOH deficiency. The NCH2–Si proton
signal at 2.01 ppm associated with intermediate 6 was also
observed. The broad Si–H singlet of intermediate 6 is labile
and was observed in the range from 3.49 to 3.60 ppm. To
explain this behavior, it should be added that the formation
of the Si–O bond is thermodynamically more favorable than
the Si–C bond, and Si–O bond has dissociation energy
530 kJ/mol comparing to 360 kJ/mol of Si–C bond.15
Scheme 2
Similarly, azepan-1-ylmethylsilane (2) reacted with 2 equiv
of MeOH at 0°C. Dimethoxy(azepan-1-ylmethyl)silane (7a)
and trimethoxy(azepan-1-ylmethyl)silane (7b) were isolated
in the yield of 85% and 12%, respectively. Meanwhile, the
reaction of silane 2 with 3 equiv of MeOH at 5°C resulted
in the formation of product 7b in 90% yield (Scheme 4).
1
The control of the reaction progress by H NMR did not
reveal the presence of Si–C bond cleavage products.
The formation of N-methylmorpholine (4) and (MeO)4Si (5)
is explained by the cleavage of the Si–C bond in α-amino-
methylmethoxysilane which is commonly observed in
silicon chemistry.24 It should be emphasized that the type
of substituent effects the induction of a partial positive
charge on the silicon atom,25 and the heterolytic cleavage of
the Si–C bond may occur catalyzed by both Lewis acids26
or Lewis bases27 and in the presence of n-BuLi that leads to
the rearrangement of α-amino functional silanes to
alkylaminosilanes (aza-Brook rearrangement).28
However, there is no data on the cleavage of the Si–C
bond during alcoholysis of hydrosilanes under mild reaction
conditions. Only the case described by Lazareva et al.29
presents the Si–C bond cleavage under autocatalytic
transesterification of N,N-bis[ethoxy(methyl)silylmethyl]-
amines with phenol.
Scheme 4
In the next step, silanes 1 and 2 were submitted to the
reaction with sterically hindered t-BuOH and BnOH. The
appropriate dialkoxysilanes and trialkoxysilanes were
formed. Optimal reaction conditions and the amount of
formed products are shown in Table 1. However, it should
be clarified that the amount of products has been calculated
on the basis of 1H NMR spectrum.
The reaction of morpholin-4-ylmethylsilane (1) with
2 equiv of t-BuOH was carried out at 35°C for 5 h.
1H NMR spectroscopic analysis revealed the presence of
di-tert-butoxy(morpholin-4-ylmethyl)silane (8a), tri-tert-but-
oxy(morpholin-4-ylmethyl)silane (8b), and a large amount
of unreacted starting material 1 (52% of compound 1 was
recovered, Table 1, entry 1). Under the same reaction
conditions, silane 2 underwent dehydrocondensation, and
tri-tert-butoxy(azepan-1-ylmethyl)silane (10b) was obtained
as the main product (Table 1, entry 5). However, increasing
the amount of t-BuOH to 3 equiv and the temperature to
50°C, trialkoxy-substituted silanes 8b and 10b were
obtained in good yields (Table 1, entries 2, 6). Silane 1 in
the reaction with BnOH (2 equiv) formed dibenzyloxy-
(morpholin-4-ylmethyl)silane (9a) in 30% yield (Table 1,
entry 3). Silane 2, in similar reaction conditions formed
disubstituted derivative 11a as the main product of this
transformation (Table 1, entry 7). However, the use of
threefold excess of BnOH and prolonged reaction time (10 h)
Alcoholysis of α-aminomethylsilanes with autocatalytic
capacity is well documented in the literature.17 These
reactions are usually carried out in electron-donating
solvent such as N,N-dimethylacetamide which probably is
involved in the intermediate stabilization of dehydro-
condensation products (solvent effect).17 We assume that
due to the hydrogen bond formation between alcohol and
amine moiety30 and the significant basicity of the nitrogen
atom in the NCH2–Si moiety25,31 the interaction of morpholin-
4-ylmethylsilane (1) with MeOH occurs through a cyclic
five-coordinated silane transition state 6 (Scheme 3), and
further the Si–C bond breaks in the presence of MeOH
leading to the formation of N-methylmorpholine (4) and
(MeO)4Si (5) (Scheme 3).
The control of the reaction progress by 1H NMR
revealed the appearance of singlets at 2.25 ppm, which is
associated with N–CH3 moiety, and at 3.56 ppm which is
typical for (MeO)4Si (5). This excluded the possible
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Chemistry of Heterocyclic Compounds 2021, 57(3), 320–324
Table 1. Reaction conditions and yields of products 8–11
SiH(OR)2
Methyl t-butyl ether (MTBE) and alcohols were dried
and purified according to standard procedures and stored
under N2.
X
N
4-(Silylmethyl)morpholine (1) was prepared according
SiH3
8–11 a
+
to the literature procedure.22
ROH
X
N
temperature
time
1-(Silylmethyl)azepane (2). A solution of triethoxy
(azepan-1-ylmethyl)silane (4.41 g, 16 mmol) in MTBE (20 ml)
was added to the suspension of LiAlH4 (1.22 g, 32 mmol)
in MTBE (100 ml) at 0°C within 1 h under Ar atmosphere.
The resulting mixture was stirred overnight at reflux. The
solvent was removed under reduced pressure, and the
residue was distilled under reduced pressure. Yield 4.31 g
Si(OR)3
1 X = O
2 X = (CH2)2
X
N
8–11 b
ROH, Temperature, Time,
Entry Silane
R
Product (yield,* %)
equiv
°C
35
50
50
50
35
50
50
50
h
1
2
3
4
5
6
7
8
t-Bu
t-Bu
Bn
2
3
2
3
2
3
2
3
5
8a (46)** 8b (2)**
1
1
1
1
2
2
2
2
5
8a (6)
9a (30)
9a (21)
8b (90)
9b (62)
9b (70)
1
(94%), colorless liquid, bp 58°C (16 mmHg). H NMR
5
spectrum, δ, ppm (J, Hz): 1.59 (8H, br. s, CH2); 2.38 (2H, q,
J = 3.7, NCH2Si); 2.62–2.68 (4H, m, CH2NCH2Si); 3.55
Bn
10
5
t-Bu
t-Bu
Bn
10a (23) 10b (60)
10a (8) 10b (78)
1
(3H, t, J = 3.7, J(1H–29Si) = 196.0, SiH3). 13C NMR
5
spectrum, δ, ppm: 26.7; 27.6 (CH2); 40.8 (NCH2Si); 58.6
(CH2NCH2Si). Mass spectrum, m/z (Irel, %): 143 [M]+ (3),
127 (60), 112 (45), 98 (21), 84 (33), 71 (22), 56 (41), 49 (22),
42 (100). Found, m/z: 144.1213 [M+H]+. C7H18NSi.
Calculated, m/z: 144.1210.
5
11a (75) 11b (10)
11a (20) 11b (65)
Bn
10
* NMR yield using TMS as an internal standard.
** Conversion of compound 1 was 48%.
allowed to obtain trisubstituted products 9b (Table 1, entry
4) and 11b (Table 1, entry 8) in good yields.
Synthesis of compounds 3, 7–10 (General method).
Silane 1 (0.5 g, 3.81 mmol) or 2 (0.55 g, 3.84 mmol)
(1 equiv) was placed into a pressure tube with a safety
valve filled with argon. Anhydrous alcohol (2 or 3 equiv)
was added portionwise over 30 min. The reaction was
carried out for 5–10 h at 0–50°C (for the conditions, see
Schemes 2 and 3 and Table 1). After completion of the
reaction, the residual alcohol was distilled off and the
remaining mixture was analyzed by 1H NMR and GC/MS.
4-[(Trimethoxysilyl)methyl]morpholine (3). Yields 0.6 g
(71%) with 2 equiv of MeOH and 0.76 g (90%) with
3 equiv of MeOH, colorless liquid. Spectral data were in a
good agreement with the reported.13b Mass spectrum, m/z
(Irel, %): 221 [M]+ (5), 206 (1), 189 (3), 190 (9), 176 (3),
164 (24), 162 (45), 150 (12), 137 (5), 121 (32), 100 (100),
91 (28). Found, m/z: 222.1161 [M+H]+. C8H20NO4Si.
Calculated, m/z: 222.1161.
It was also observed that carrying out the reaction of
silanes 1 or 2 with BnOH at temperature above 50°C led to
a mixture of mainly Si–C bond cleavage products, i.e.,
tetrabenzyloxysilane and compound 4 or 1-methylazepane,
respectively.
Thus, the optimal reaction conditions for the synthesis of
alkoxy derivatives of heterocyclic α-aminomethylsilanes with-
out the use of catalyst and solvent have been developed. It
was shown that due to α-effect morpholin-4-ylmethylsilane
possesses significantly higher reactivity in the dehydro-
condensation reaction with MeOH than azepan-1-ylmethyl-
silane. The cleavage of the Si–C bond was observed
although the process was carried out under mild reaction
conditions and led to the formation of N-methylmorpholine
and tetramethoxysilane. It should be noted that the steric
effect of the t-BuOH suppresses the formation of trialkoxy
derivative of morpholin-4-ylmethylsilane at 35°C although
at the higher temperature (50°C), tri-tert-butoxy(morpholin-
4-ylmethyl)silane was isolated in very good yield of 90%.
The obtained result proves that it is possible to synthesize
dibenzyloxy derivative of 1-(silylmethyl)azepane with a
satisfactory yield of 75%.
1-[(Dimethoxysilyl)methyl]azepane (7a). Yields 0.66 g
(85%) with 2 equiv of MeOH and 0.06 g (8%) with 3 equiv
of MeOH, colorless liquid. 1H NMR spectrum, δ, ppm (J, Hz):
1.48–1.56 (8H, m, CH2); 2.35 (2H, d, J = 3.7, NCH2Si);
2.58–2.69 (4H, m, CH2NCH2Si); 3.38 (1H, t, J = 3.7, SiH);
3.46 (6H, s, OCH3). 13C NMR spectrum, δ, ppm: 26.8
(CH2); 27.0 (CH2); 44.3 (NCH2Si); 50.7 (OCH3); 57.2
(CH2NCH2Si). Mass spectrum, m/z (Irel, %): 203 [M]+ (2),
190 (8), 176 (5), 164 (11), 150 (2), 148 (4), 134 (3), 121 (8),
112 (100), 91 (11), 84 (12), 75 (4), 70 (3), 61 (7). Found, m/z:
204.1426 [M+H]+. C9H22NO2Si. Calculated, m/z: 204.1420.
1-[(Trimethoxysilyl)methyl]azepane (7b). Yields 0.11 g
(12%) with 2 equiv of MeOH and 0.81 g (90%) with 3 equiv
Experimental
1H and 13C NMR spectra were recorded on a Bruker
DRX-300 spectrometer (300 and 75 MHz, respectively)
in CDCl3 solutions using TMS as internal standard.
Assignment of the 13C NMR data was supported by DEPT
135 experiments. Low-resolution mass spectra were
recorded on a Shimadzu GC/MS-QP5050A mass spectro-
meter (EI, 70eV) with a Shimadzu GC-17A gas chromato-
graph equipped with a Phenomenex DB 5 ms column
(30 m × 0.25 mm i. d. × 0.25 μm). High-resolution mass
spectra were recorded on an AMD 604 S mass spectro-
meter with electrospray ionization. All reactions were
carried out under dry Ar atmosphere.
1
of MeOH, colorless liquid. H NMR spectrum, δ, ppm:
1.48–1.56 (8H, m, CH2); 2.17 (2H, s, NCH2Si); 2.58–2.69
(4H, m, CH2NCH2Si); 3.48 (9H, s, CH3). 13C NMR spectrum,
δ, ppm: 26.8; 27.0 (CH2); 47.6 (NCH2Si); 50.5 (CH3); 58.0
(CH2NCH2Si). Mass spectrum, m/z (Irel, %): 233 [M]+ (6),
218 (2), 204 (5), 190 (8), 176 (5), 164 (10), 148 (4), 134 (3),
121 (7), 112 (100), 84 (13), 59 (9). Found, m/z: 234.1529
[M+H]+. C10H24NO3Si. Calculated, m/z: 234.1525.
322

Chemistry of Heterocyclic Compounds 2021, 57(3), 320–324
4-[(Di-tert-butoxysilyl)methyl]morpholine (8a). Yields
248 (14), 204 (8), 175 (2), 112 (100), 93 (11), 58 (35).
Found, m/z: 310.2175 [M+Na]+. C15H33NNaO2Si. Calcu-
lated, m/z: 310.2178.
0.48 g (46%) with 2 equiv of t-BuOH and 0.06 g (6%) with
1
3 equiv of t-BuOH, colorless liquid. H NMR spectrum,
δ, ppm (J, Hz): 1.28 (18H, s, CH3); 1.89 (2H, d, J = 3.6,
NCH2Si); 2.42–2.48 (4H, m, CH2 morpholine); 3.57 (1H, t,
J = 3.6, SiH); 3.63–3.69 (4H, m, CH2 morpholine). 13C NMR
spectrum, δ, ppm: 31.1 (CH3); 50.1 (NCH2Si); 56.9
(NCH2CH2O); 67.2 (NCH2CH2O); 72.6 (C). Mass spectrum,
m/z (Irel, %): 274 [M–H]+ (6), 216 (21), 176 (11), 133 (18),
100 (68), 84 (22), 77 (99), 75 (14), 59 (100). Found, m/z:
298.1823 [M+Na]+. C13H29NNaO3Si. Calculated, m/z:
298.1814.
1-[(Tri-tert-butoxysilyl)methyl]azepane (10b). Yields
0.83 g (60%) with 2 equiv of t-BuOH and 1.08 g (78%)
with 3 equiv of t-BuOH, colorless liquid. 1H NMR
spectrum, δ, ppm: 1.32 (27H, s, CH3); 1.51–1.70 (8H, m,
CH2 azepane); 1.96 (2H, s, NCH2Si); 2.62–2.72 (4H, m,
CH2 azepane). 13C NMR spectrum, δ, ppm: 26.9 (CH2);
27.9 (CH2); 31.6 (CH3); 47.3 (NCH2Si); 58.7 (CH2NCH2Si);
69.2 (C). Mass spectrum, m/z (Irel, %): 359 [M]+ (4), 344 (8),
330 (1), 316 (5), 302 (3), 286 (17), 276 (1), 260 (2), 246 (2),
234 (3), 204 (2), 190 (6), 178 (2), 164 (2), 135 (10), 122 (3),
112 (100), 98 (4), 58 (20). Found, m/z: 360.2939 [M+H]+.
C19H42NO3Si. Calculated, m/z: 360.2934.
4-[(Tri-tert-butoxysilyl)methyl]morpholine (8b). Yields
0.03 g (2%) with 2 equiv of t-BuOH and 1.19 g (90%) with
1
3 equiv of t-BuOH, colorless liquid. H NMR spectrum,
δ, ppm (J, Hz): 1.31 (27H, s, CH3); 1.84 (2H, s, NCH2Si);
2.43–2.48 (4H, m, CH2 morpholine); 3.67–3.72 (4H, m,
CH2 morpholine). 13C NMR spectrum, δ, ppm: 31.5 (CH3);
49.2 (NCH2Si); 57.0 (NCH2CH2O); 67.1 (NCH2CH2O);
72.8 (C). Mass spectrum, m/z (Irel, %): 347 [M]+ (9), 332 (10),
290 (17), 274 (27), 234 (3), 218 (6), 178 (15), 162 (20),
148 (9), 135 (60), 121 (5), 100 (100), 86 (11), 79 (52),
57 (93). Found, m/z: 348.2576 [M+H]+. C17H38NO4Si.
Calculated, m/z: 348.2576.
1-{[Bis(benzyloxy)silyl]methyl}azepane (11a). Yields
1.02 g (75%) with 2 equiv of BnOH and 0.27 g (20%) with
3 equiv of BnOH, colorless liquid. H NMR spectrum,
1
δ, ppm (J, Hz): 1.46–1.70 (8H, m, CH2 azepane); 2.31 (2H,
d, J = 3.8, NCH2Si); 2.51–2.56 (4H, m, CH2 azepane); 3.41
(1H, t, J = 3.8, SiH); 4.70 (4H, s, OCH2Ph); 7.26–7.41
(10H, m, H Ph). 13C NMR spectrum, δ, ppm: 26.9 (CH2);
27.1 (CH2); 45.4 (NCH2Si); 57.2 (NCH2CH2O); 63.5
(OCH2Ph); 126.5 (C-2,6 Ph); 127.1; 128.5 (C-3–5 Ph);
139.1 (C-1 Ph). Mass spectrum, m/z (Irel, %): 355 [M]+ (1),
339 (5), 324 (2), 310 (6), 296 (9), 282 (5), 270 (12), 252 (2),
238 (3), 227 (27), 213 (2), 197 (10), 165 (4), 151 (4), 137 (8),
121 (4), 112 (100), 107 (11), 91 (5), 77 (10). Found, m/z:
378.1868 [M+Na]+. C21H29NNaO2Si. Calculated, m/z:
378.1865.
4-{[Bis(benzyloxy)silyl]methyl}morpholine (9a). Yields
0.39 g (30%) with 2 equiv of BnOH and 0.27 g (21%) with
1
3 equiv of BnOH, colorless liquid. H NMR spectrum,
δ, ppm (J, Hz): 2.01 (2H, d, J = 3.6, NCH2Si); 2.35–2.41
(4H, m, CH2 morpholine); 3.50–3.58 (5H, m, CH2
morpholine, SiH); 4.67 (4H, s, OCH2Ph); 7.24–7.36 (10H,
m, H Ph). 13C NMR spectrum, δ, ppm: 46.7 (NCH2Si); 54.7
(NCH2CH2O); 64.2 (OCH2Ph); 66.0 (NCH2CH2O); 126.8
(C-2,6 Ph); 127.3; 128.3 (C-3–5 Ph); 140.8 (C-1 Ph). Mass
spectrum, m/z (Irel, %): 343 [M]+ (1), 237 (3), 207 (1), 193 (3),
173 (1), 149 (56), 143 (81), 133 (6), 121 (63), 115 (85),
105 (5), 99 (25), 91 (25), 75 (100), 59 (21). Found, m/z:
344.1686 [M+H]+. C19H26NO3Si. Calculated, m/z: 344.1682.
4-{[Tris(benzyloxy)silyl]methyl}morpholine (9b). Yields
1.06 g (62%) with 2 equiv of BnOH and 1.2 g (70%) with
1-{[Tris(benzyloxy)silyl]methyl}azepane (11b). Yields
0.18 g (10%) with 2 equiv of BnOH and 1.15 g (65%) with
1
3 equiv of BnOH, colorless liquid. H NMR spectrum,
δ, ppm: 1.83–2.04 (8H, m, CH2 azepane); 2.17 (2H, s,
NCH2Si); 2.51–2.56 (4H, m, CH2 azepane); 4.70 (6H, s,
OCH2Ph); 7.24–7.40 (15H, m, H Ph). 13C NMR spectrum,
δ, ppm: 26.8 (CH2); 26.9 (CH2); 47.3 (NCH2Si); 58.5
(NCH2CH2O); 65.7 (OCH2Ph); 126.4 (C-2,6 Ph); 127.2;
128.4 (C-3–5 Ph); 138.6 (C-1 Ph). Mass spectrum, m/z (Irel, %):
461 [M]+ (2), 448 (5), 434 (3), 420 (12), 404 (2), 390 (3),
378 (2), 364 (8), 348 (3), 334 (2), 308 (4), 292 (3), 267 (4),
252 (15), 234 (5), 211 (20), 194 (11), 137 (3), 125 (3), 112
(100), 107 (2), 91 (10), 77 (2). Found, m/z: 462.2470
[M+H]+. C28H36NO3Si. Calculated, m/z: 462.2464.
1
3 equiv of BnOH, colorless liquid. H NMR spectrum,
δ, ppm: 2.05 (2H, s, NCH2Si); 2.38–2.45 (4H, m, CH2
morpholine); 3.56–3.64 (4H, m, CH2 morpholine); 4.84
(6H, s, OCH2Ph); 7.24–7.36 (15H, m, H Ph). 13C NMR
spectrum, δ, ppm: 49.4 (NCH2Si); 56.7 (NCH2CH2O); 64.7
(OCH2Ph); 66.6 (NCH2CH2O); 126.8 (C-2,6 Ph); 127.3;
128.3 (C-3–5 Ph); 140.8 (C-1 Ph). Mass spectrum, m/z (Irel, %):
341 [M–OCH2Ph]+ (1), 234 (1), 219 (1), 205 (1), 189 (9),
179 (1), 161 (1), 149 (25), 143 (100), 133 (7), 121 (28),
115 (54), 103 (56), 91 (11), 75 (92), 59 (47). Found, m/z:
450.2108 [M+H]+. C26H32NO4Si. Calculated, m/z: 450.2100.
1-[(Di-tert-butoxysilyl)methyl]azepane (10a). Yields
0.254 g (23%) with 2 equiv of t-BuOH and 0.09 g (8%)
with 3 equiv of t-BuOH, colorless liquid. 1H NMR
spectrum, δ, ppm (J, Hz): 1.28 (18H, s, CH3); 1.51–1.70
(8H, m, CH2 azepane); 2.03 (2H, d, J = 3.8, NCH2Si); 2.50–
2.61 (4H, m, CH2 azepane); 3.42 (1H, t, J = 3.8, SiH).
13C NMR spectrum, δ, ppm: 26.7 (CH2); 27.8 (CH2); 31.2
(CH3); 47.3 (NCH2Si); 58.7 (CH2NCH2Si); 69.2 (C). Mass
spectrum, m/z (Irel, %): 287 [M]+ (1), 272 (7), 260 (3),
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