Mixed reagent (aminosilyl)lithium/i-PrMgBr for the synthesis of functionalized oligosilanes

Article abstract of DOI:10.1016/S0022-328X(00)00077-2

Mixed reagents prepared in situ from the (aminosilyl)lithiums with i-PrMgBr undergo coupling reactions with chloro-oligosilanes without Si-Si bond cleavage, which is a serious side reaction with the (aminosilyl)lithiums themselves. Based on the coupling reaction and the amino-to-chloro transformation, functionalized tetrasilanes and hexasilanes are synthesized. The analysis of the ¹H- and ²⁹Si-NMR spectra indicates that these oligosilanes include three configurational isomers, ll, ul, and uu.

Full text of DOI:10.1016/S0022-328X(00)00077-2

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 601 (2000) 259–266
Mixed reagent (aminosilyl)lithium/i-PrMgBr for the synthesis of
functionalized oligosilanes
Atsushi Kawachi, Kohei Tamao *
Institute for Chemical Research, Kyoto Uni6ersity, Uji, Kyoto 611-0011, Japan
Received 27 December 1999; received in revised form 26 January 2000; accepted 26 January 2000
Abstract
Mixed reagents prepared in situ from the (aminosilyl)lithiums with i-PrMgBr undergo coupling reactions with chloro-oligosi-
lanes without SiꢀSi bond cleavage, which is a serious side reaction with the (aminosilyl)lithiums themselves. Based on the coupling
reaction and the amino-to-chloro transformation, functionalized tetrasilanes and hexasilanes are synthesized. The analysis of the
1H- and 29Si-NMR spectra indicates that these oligosilanes include three configurational isomers, ll, ul, and uu. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Oligosilanes; Magnesium; Stereoisomers
1. Introduction
of amino-disilanes and trisilanes [4]. By treatment
with an acyl chloride [4] or hydrogen chloride [5],
these amino-oligosilanes can be converted into the
chloro-oligosilanes, which work as precursors for fur-
ther SiꢀSi chain elongation reaction. This facile func-
tional group transformation is one of the most
remarkable features in the aminosilyl anion chemistry.
In the reaction of the (aminosilyl)lithiums with
chloro-oligosilanes, however, cleavage of the SiꢀSi
bond often occurs to lower the yields of the desired
coupling products. To overcome this problem, we
have tried to control the reactivity of the aminosilyl
anions by changing the counter cation Li+ to other
metal cations. Considering the electronegativity [6],
Mg (1.23), Zn (1.66), and Cu (1.75) were expected to
form more covalent bonding to Si (1.74) than Li
(0.97), so that the reactivity of silylꢀmagnesium [7],
silylꢀzinc [8], and silylꢀcopper [9] species could be dif-
ferent from that of the silyllithiums. Among the
metals examined so far, we found that magnesium is
the most suitable for our purpose. We report here the
preparation of the mixed reagents of the (aminosi-
lyl)lithium and i-PrMgBr and their application to the
synthesis of functionalized oligosilanes based on the
facile amino-to-chloro transformation.
Polysilanes have received much attention due to
their interesting chemical and physical properties [1].
To investigate these properties, synthetic methodolo-
gies for structurally well-defined oligo- and polysilanes
have been developed. The standard method for the
SiꢀSi chain elongation is based on a combination of
two steps: (1) coupling of (organosilyl)lithiums [2]
with silanes bearing good leaving groups such as
halogens and the trifluoromethane sulfonate group,
and (2) conversion of the organic groups such as the
phenyl and methyl groups on the silicon atom(s) into
good leaving groups. Based on this methodology,
Lambert et al. [3a], Suzuki et al. [3b], and Sekiguchi
et al. [3c] independently had a remarkable success in
the syntheses of dendric polysilanes with regular
three-dimensional structures.
We previously reported that the (aminosilyl)lithiums
1–3 readily react with chlorosilanes to yield a variety
* Corresponding author. Tel.: +81-774-383180; fax: +81-774-
383186.
E-mail address: tamao@sc1.kyoto-u.ac.jp (K. Tamao)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00077-2

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A. Kawachi, K. Tamao / Journal of Organometallic Chemistry 601 (2000) 259–266
2. Results and discussion
without formation of the alkylation product 5, as
shown in Eqs. (2) and (3).
2.1. Preparation and reaction of mixed
(aminosilyl)lithium/i-PrMgBr reagents
Other examined species are mentioned for compari-
son. While a silylꢀmagnesium species prepared from 1
with MgBr2 (1–MgBr2=1:1 and 2:1 mol ratio) af-
forded 4 in much lower yields, other mixed-metal
The mixed reagents were prepared in situ by mixing
the (aminosilyl)lithiums 1–3 [4] with alkyl Grignard
reagents, RMgBr, at 0°C based on the method reported
by Oshima and co-workers [7d]. The reagents might
involve the (aminosilyl)(alkyl)magnesium moieties as
previously proposed [7b], and thus potentially may
offer two reaction modes, that is, silylation and alkyla-
tion, which depend on the transfer ability of the silyl
group and the alkyl group. The reactions of a series of
reagents 1/RMgBr (R=Me, Et, i-Pr) with PhMe2SiCl
in THF–Et2O were examined (Eq. (1)). In all cases, the
silylation product, (Et2N)Ph2SiꢀSiMe2Ph (4), was more
preferred than the alkylation product, RꢀSiMe2Ph (5),
as shown in Table 1. Selectivity of the silylation in-
creased as the alkyl group became bulkier. The alkyla-
tion was completely suppressed in the case of the
isopropyl group. It is noted that the silylation should
regenerate i-PrMgX (X=Cl, Br), but no alkylation of
the chlorosilane was observed under the reaction condi-
tion. Two other mixed reagents, 2/i-PrMgBr and 3/i-
PrMgBr, also exhibited sufficient reactivity toward
PhMe2SiCl under mild conditions (0°C, 0.5–1.5 h) to
afford 6 and 7 in 72 and 57% yields, respectively,
reagents prepared from
ZnCl2·tmeda, or n-Bu2Zn afforded only a complex
mixture during the reaction with chlorosilanes.
1
with CuCN, ZnCl2,
Chart 1
(1)
(2)
(3)
Table 1
Products from reactions of the mixed reagent 1/RMgBr with
PhMe2SiCl according to Eq. (1)
2.2. Synthesis of oligosilanes
Using the (aminosilyl)lithium/i-PrMgBr mixed
reagents, the undesired SiꢀSi bond cleavage was almost
completely suppressed, as shown in Scheme 1. Thus, the
mixed reagent 1/i-PrMgBr (2 mol) reacted with the
1,1-dichlorodisilane 8 [10] to afford the desired coupling
product 9 in higher than 95% chemoselectivity, whereas
the lithium reagent 1 itself significantly caused the SiꢀSi
bond cleavage, yielding 10 in addition to 9 (9:10=
86:14). We found that the hydrolysis of the reaction
mixture of 9 under alkaline conditions using a 1 M
NaOH aq. solution at 0°C was successful to decompose
the regenerated Grignard reagent by keeping the sili-
conꢀnitrogen bond intact.
Product(s)
RMgBr
Total yield (%) a Silylation (4):Alkylation (5) b
MeMgBr
EtMgBr
i-PrMgBr
80
88
80
87:13
88:12
100:0
a Isolated yields by bulb-to-bulb distillation.
b The ratio was determined by 1H-NMR analysis of the reaction
mixture.
For the amino-to-chloro transformation, 9 was
treated with an excess of dry hydrogen chloride in Et2O
at room temperature to yield the corresponding
dichlorotetrasilane 11, as shown in Scheme 2. For
isolation, 11 was methylated with MeMgBr in Et2O
to afford 12 in 63% overall yield based on 8. The
29Si-NMR spectrum of 12 showed signals at
l
−11.5 (−SiMe3), −16.1 (−SiPh2Me), and −85.3
(+SiMe), which are consistent with the reported chem-
ical shift ranges for the polydimethylsilanes, e.g. −9 to
Scheme 1.

A. Kawachi, K. Tamao / Journal of Organometallic Chemistry 601 (2000) 259–266
261
composition of the regenerated Grignard reagent using
a 1 M NaOH aq. solution followed by the usual
work-up, the reaction mixture of 13 was treated with an
excess of dry hydrogen chloride in Et2O at room tem-
perature, yielding the dichlorotetrasilane 14. For isola-
tion, 14 was methylated with MeMgBr in Et2O
to afford 15 in 59% overall yield based on 8. The
29Si-NMR spectrum of 15 showed signals at
l
−11.9 (−SiMe3), −15.5 (−SiPhMe2), and −86.4
(+SiMe). The second silylation was performed on 14
using the reagent 1/i-PrMgBr (2 mol amt.) in THF–
Et2O at 0°C, which afforded the branched hexasilane
16. The amino-to-chloro transformation of 16 and sub-
sequent methylation of the resulting dichlorohexasilane
17 afforded the corresponding hexasilane 18 in 43%
overall yield based on 8 as a mixture of the configura-
tional isomers (see below).
Scheme 2.
−20 ppm for −SiMe3 and −79 to −81 ppm for
+SiMe [11].
An example of the synthesis of functionalized hexasi-
lanes by reiteration of this methodology is shown in
Scheme 3. The reaction of the mixed reagent, 3/i-
PrMgBr (2 mol amt.), with 8 in THF–Et2O at 0°C
afforded the desired branched tetrasilane 13. After de-
2.3. Identification of the stereoisomers of 14 and 18
The stereoisomers of 14 and 18 were identified as
follows. Due to the two chiral silicon centers, there are
Scheme 3.
Fig. 1. Configurational isomers of 14 and 18.

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0.76 in the ratio of 1:1:1:1, due to the methyl groups in
14ll and 14uu and non-equivalence of the two methyl
groups in 14ul. The 29Si-NMR spectrum (Fig. 2(b))
shows signals of the silicon atom of the Me3Si group
(Si-1) at l −78.07, −77.87, and −77.79 in the ratio
1
of 1:2:1, which is consistent with the H-NMR spec-
trum. Two signals of the branched silicon atoms (Si-2)
appear at l −11.64 and −11.51 in the ratio of 1:3,
where the former is assigned to the signal of 14ll (or
14uu) and the latter is assigned to the coincidentally
overlapped signals of 14ul and 14uu (or 14ll). Signals
for the chiral silicon atoms (Si-3) appear at l 18.42,
18.57, 18.75, and 18.90 in the ratio of 1:1:1:1, which is
1
consistent with the H-NMR spectrum.
1
The H-NMR spectrum of 18, obtained from 14 and
purified by medium-pressure liquid chromatography,
displays several peaks due to the methyl protons at-
tributed to the isomers, as shown in Fig. 3, but the
assignment of these peaks was difficult at this stage.
Fortunately, the major isomer could be isolated using
reverse-phase liquid chromatography, which allowed us
1
to make an assignment of the H and 29Si peaks, as
shown in Fig. 4.
The 1H-NMR spectrum of the major isomer (Fig.
4(a)) displays a singlet for the methyl protons on the
Me3Si group (H-1) at l −0.010 and a singlet for the
methyl protons on the branched silicon atom (H-2) at l
−0.28. A pair of signals for the methyl protons on the
chiral silicon atom (H-3) appears at l 0.41 and 0.51 in
the ratio of 1:1. The non-equivalence of the methyl
groups is the expected pattern of the isomer 18ul. The
methyl protons on the terminal silicon atoms (H-4) also
Fig. 2. 1H- and 29Si-NMR spectra of a mixture of 14ll, 14ul, and
14uu: (a) 1H-NMR, and (b) 29Si-NMR. The marked (×) peaks in the
1H-NMR spectrum are due to impurities.
three possible configurational isomers, ll, ul and its
enantiomer lu, and uu, in 14 and 18, as shown in Fig. 1,
where l and u denote ‘like’ and ‘unlike’, respectively
[12,13].
1
According to the H- and 29Si-NMR spectra of the
crude product 14 (Fig. 2), all of the three isomers are
1
present in the ratio of 1:2:1. The H-NMR spectrum
(Fig. 2(a)) displays three signals of the methyl protons
on the Me3Si group (H-1) at l 0.096, 0.15, and 0.18 in
the ratio of 1:2:1, which is consistent with the statistical
distribution of the three isomers. The methyl protons
appear on the branched silicon atoms (H-2) at l 0.34
and 0.36 in the ratio of 1:1, in one of which the signals
of the isomers 14ll and 14uu may be coincidentally
overlapped, and the other can be assigned to the signal
of the isomer 14ul. The methyl protons also appear on
the chiral silicon atom (H-3) at l 0.67, 0.70, 0.74, and
Fig. 3. 1H-NMR spectrum of 18. The peaks marked with an asterisk
(*) belong to 18ul. The marked (×) peaks are due to impurities.

A. Kawachi, K. Tamao / Journal of Organometallic Chemistry 601 (2000) 259–266
263
(1:2:1). It is plausible that the formation of 18ll and
18uu is less favorable than 18ul due to the steric repul-
sion between the phenyl groups on Si-3.
3. Experimental
3.1. General
1
The H(200 MHz)-, 13C(50.29 MHz)-, and 29Si(39.73
MHz)-NMR spectra were recorded on a Varian VXR-
200 spectrometer or the 1H(270 MHz)-, 13C(67.94
MHz)-, and 29Si(53.67 MHz)-NMR spectra were
1
recorded on a JEOL EX-270 spectrometer. The H and
13C chemical shifts are referenced to internal benzene-d6
(1H l 7.200 and 13C l 128.00). Mass spectra were
measured on a JEOL JMS-D300 mass spectrometer
connected to a JEOL LGC-20K gas chromatograph
equipped with a 1 m glass column packed with OV-17
(3%) on Chromosorb. The elemental analyses were
performed at the Microanalysis Center of Kyoto Uni-
versity or at the Microanalysis Division of the Institute
for Chemical Research, Kyoto University. Analytical
samples were purified by preparative GLC, preparative
medium-pressure liquid chromatography (MPLC), or
recycling reverse-phase liquid chromatography. The
GLC analysis was performed on a Shimadzu GC-4B
gas chromatograph equipped with a 3 or 1 m column
packed with 30% Silicone DC550 on Celite 545. Prepar-
ative MPLC was performed with a silica gel prepacked
C.I.G. column (Kusano, Si-10). Recycling reverse-phase
liquid chromatography was performed with a JAI LC-
908 equipped with JAIGEL-ODS S-343-15 and P-15
columns. Column chromatography was performed by
using Kieselgel 60 (Merck, 70–230 mesh). Thin-layer
chromatography (TLC) was performed on plates of
silica gel 60F-254 (Merck).
Fig. 4. 1H- and 29Si-NMR spectrum of 18ul. (a) 1H-NMR, and (b)
29Si-NMR.
The lithium dispersion (25 or 30 wt.% in mineral oil)
was purchased from Aldrich. Lithium granules were
purchased from Chemetall Gesellshaft. Methylmagne-
sium bromide in diethyl ether was purchased from
Tokyo Chemical Industry Co. Ethylmagnesium bro-
mide in diethyl ether and isopropylmagnesium bromide
in diethyl ether were prepared from magnesium with
ethylbromide and isopropylbromide, respectively, and
titrated prior to use [15]. Phenyldimethylchlorosilane
was distilled under reduced pressure before use. 1,1-
Dichlorotetramethyldisilane 8 was prepared by the liter-
ature method [10]. Ether and THF were distilled under
a nitrogen atmosphere from sodium–benzophenone.
Hexane was dried over sodium wire and distilled under
a nitrogen atmosphere. All reactions were carried out
under a nitrogen or argon atmosphere.
appear as a pair of signals at l 0.68 and 0.69 in the
ratio of 1:1. The 29Si-NMR spectrum (Fig. 4(b)) dis-
plays a single peak for the branched silicon atom (Si-2)
at l −76.02. A pair of signals for the chiral silicon
atoms (Si-3) appears at l −40.00 and −38.95 in the
ratio of 1:1, and also a pair of signals for the terminal
silicon atoms (Si-4) at l −19.09 and −18.94 in the
ratio of 1:1, which is consistent with the 1H-NMR
spectrum. A single peak for the silicon atom of the
Me3Si group (Si-1) appears at l −10.87. Thus the
major isomer formed is assigned to 18ul.
Based on the assignment of 18ul, other peaks in the
1H-NMR spectrum shown in Fig. 3 can be tentatively
assigned. Thus, the ratio of the isomers 18ll, 18ul, and
18uu is roughly estimated to be 1:3:1, based on the
integral ratio of the methyl protons on the terminal
silicon atoms (H-4) [14]. The estimated ratio is different
from the statistical distribution of the three isomers
The (aminosilyl)lithiums 1–3 were prepared by reac-
tion of the corresponding (amino)chlorosilanes with
lithium metal in THF as previously reported [4].

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3.2. A typical procedure for preparation of the mixed
reagent (aminosilyl)lithiums/i-PrMgBr: preparation of
2/i-PrMgBr and trapping as 1,1-bis(diethylamino)-1,2-
diphenyl-2,2-dimethyldisilane (6)
diphenylchlorosilane (5.6 mmol) and granular lithium
(26 mg-atom) in THF (10 ml) [4], was added i-PrMgBr
in Et2O (4.3 ml, 5.6 mmol) over 4 min at 0°C. The
reaction solution was then stirred at 0°C for 30 min. To
the solution was added a solution of 8 (546 mg, 2.8
mmol) in THF (1.0 ml) at 0°C over 1 min. The reaction
mixture was stirred at 0°C for 2 h and at r.t. overnight.
To the reaction mixture was slowly added a 1 M NaOH
aq. solution (0.3 ml) at 0°C and stirred for ca. 10 min.
The mixture was filtered and the filtrate was evaporated.
The residue was diluted with hexane (10 ml), dried over
K2CO3 and concentrated in vacuo to give a 1.49 g of
To a solution of 2, prepared from bis(diethyl-
amino)phenylchlorosilane (2.0 mmol) and lithium dis-
persion (11 mg atom) in THF (4.0 ml) [4], was added
i-PrMgBr in Et2O (1.5 ml, 2.0 mmol) at 0°C. The
solution was stirred at the same temperature for 30 min
to afford a dark brown solution 6. To the solution was
added phenyldimethylchlorosilane (0.36 ml, 2.2 mmol)
at 0°C. The reaction mixture was stirred at the same
temperature for 30 min and at room temperature (r.t.)
overnight. The reaction mixture was then diluted with
hexane (20 ml), stirred vigorously, and filtered. The
filtrate was concentrated and the residue was subjected
to bulb-to-bulb distillation to give 6 (543 mg, 72% yield)
as a pale yellow oil. B.p. 185–205°C/0.55 mmHg (bath
1
mixture of 9 and 10: H-NMR analysis of the mixture
showed that the ratio of 9:10 was ]95:55. 9: 1H-
NMR (C6D6): l 0.14 (s, 9H), 0.66 (s, 3H), 0.94 (t,
J=7.0 Hz, 12H), 3.00 (q, J=7.0 Hz, 8H), 7.23–7.27
(m, 12H), 7.60–7.64 (m, 4H), 7.69–7.74 (m, 4H). 10:
1H-NMR (C6D6): l 0.25 (s, 9H), 1.00 (t, J=7.0 Hz,
6H), 3.03 (q, J=7.0 Hz, 4H), 7.26–7.30 (m, 6H),
7.71–7.75 (m, 4H).
1
temperature). H-NMR (C6D6): l 0.53 (s, 6H), 1.01 (t,
J=7.0 Hz, 12H), 3.02 (q, J=7.0 Hz, 8H), 7.18–7.22
(m, 3H), 7.29–7.33 (m, 3H), 7.46–7.50 (m, 2H), 7.71–
7.75 (m, 2H). 13C-NMR (C6D6): l −1.28, 15.03, 40.24,
127.82, 127.95, 128.60, 129.15, 134.72, 135.52, 139.51,
140.23. MS: m/e 384 [M+]. Anal. Calc. for C22H36N2Si2:
C, 68.69; H, 9.43. Found: C, 68.60; H, 9.26%.
3.6. Transformation of 9: synthesis of 2-trimethylsilyl-
1,1,3,3-tetraphenyl-1,2,3-trimethyltrisilane (12)
1. Through a solution of crude 9 (1.49 g) in Et2O
(20 ml) as prepared above, was bubbled dry
hydrogen chloride, generated from ammonium
chloride (7.8 g, 148 mmol) and concentrated sul-
furic acid (6.3 ml, 113 mmol), at r.t. for 30 min
with stirring. The mixture was diluted with hexane
(20 ml) and filtered. The filtrate was concentrated
to afford crude 11 (1.27 g) as an oil, which was
used in the next step without purification.
3.3. 1-Diethylamino-1,1,2-triphenyl-2,2-
trimethyldisilane (4)
1
B.p. 225–255°C/1.0 mmHg (bath temperature). H-
NMR (C6D6): l 0.25 (s, 9H), 1.00 (t, J=7.0 Hz, 6H),
3.03 (q, J=7.0 Hz, 4H), 7.26–7.30 (m, 3H), 7.71–7.76
(m, 2H). 13C-NMR (C6D6): l −1.99, 15.28, 41.86,
127.93, 128.07, 128.85, 129.28, 134.74, 135.71, 138.12,
139.21. MS: m/e 389 [M+]. Anal. Calc. for C24H31NSi2:
C, 73.77; H, 8.01. Found: C, 73.54; H, 8.10%.
1H-NMR (C6D6):
l
0.16 (s, 9H), 0.66 (s,
3H), 7.07–7.13 (m, 12H), 7.60–7.66 (m, 8H). 13C-
NMR (C6D6): (The phenyl carbons of the ClPh2Siꢀ
groups are diastereotopic.) l −9.92, 0.13, 128.34,
128.38, 130.38, 130.43, 134.87, 135.01, 135.07,
135.41. 29Si-NMR (C6D6): l −76.32, −10.42,
10.35.
3.4. 1-Diethylamino-1,2-diphenyl-1,2,2-trimethyldisilane
(7)
1
B.p. 160–180°C/1.0 mmHg (bath temperature). H-
2. To a solution of 11 in Et2O (5.0 ml) was added
MeMgBr in Et2O (3.9 ml, 11.1 mmol) at r.t. over 10
min and the reaction mixture was refluxed for 5 h.
After being cooled to 0°C, the reaction mixture was
hydrolyzed with 1 M hydrochloric acid (10 ml) and
extracted with Et2O (2×20 ml). The combined or-
ganic layer was washed with brine (20 ml), water (20
ml), dried over MgSO4, and concentrated. The
residue was subjected to column chromatography
on silica gel (60 ml) eluted with 70:1 hexane–AcOEt
to give 12 (892 mg, overall 63% yield) (Rf=0.20) as
NMR (C6D6): l 0.42 (s, 3H), 0.44 (s, 3H), 0.52 (s, 3H),
0.92 (t, J=7.0 Hz, 6H), 2.87 (q, J=7.0 Hz, 4H),
7.23–7.29 (m, 6H), 7.47–7.52 (m, 2H), 7.58–7.62 (m,
2H). 13C-NMR (C6D6): l −2.91, −1.72, 15.71, 41.69,
128.00, 128.07, 128.74, 128.99, 134.42, 134.54, 139.54,
140.35. MS: m/e 327 [M+]. Anal. Calc. for C19H29NSi2:
C, 69.66; H, 8.92. Found: C, 69.36; H, 9.19%.
3.5. Reaction of the mixed reagent 1/i-PrMgBr with
1,1-dichlorotetramethyldisilane (8): synthesis of 2-
trimethylsilyl-1,3-bis(diethylamino)-1,1,3,3-tetraphenyl-
2-methyltrisilane (9)
1
an oil. 12: H-NMR (C6D6): l 0.029 (s, 9H), 0.52 (s,
3H), 0.62 (s, 6H), 7.15–7.22 (m, 12H), 7.45–7.57
To a solution of 1, prepared from (diethylamino)-
(m, 8H). 13C-NMR (CDCl3) (The phenyl carbons of

A. Kawachi, K. Tamao / Journal of Organometallic Chemistry 601 (2000) 259–266
265
the MePh2Siꢀ groups are diastereotopic.):
l
After being cooled to 0°C, the reaction mixture was
hydrolyzed with 1 M hydrochloric acid (12 ml) and
extracted with Et2O (2×20 ml). The combined or-
ganic layer was washed with brine (10 ml), water (10
ml), dried over MgSO4, and concentrated. The
residue was subjected to column chromatography
on silica gel (30 ml) eluted with hexane to give 15
(255 mg, overall 59% yield based on 8) (Rf=0.40)
−10.29, −2.75, 0.15, 127.67, 127.75, 128.63, 128.75,
134.86, 134.97, 137.81, 137.93. 29Si-NMR (C6D6): l
−85.29, −16.06, −11.50. MS: m/e 510 [M+, 50],
495 [M+−Me, 4], 437 [M+−SiMe3, 10], 360 (19),
313 [M+−SiPh2Me, 22], 298 (44), 236 (49), 197
[MePh2Si+, 100]. Anal. Calc. for C30H38Si4: C,
70.52; H, 7.50. Found: C, 70.43; H, 7.39%.
1
as an oil. 15: H-NMR (C6D6) (the methyl protons
3.7. Reaction of 1 with 8
of the Me2PhSiꢀ groups are diastereotopic): l 0.072
(s, 9H), 0.25 (s, 3H), 0.38 (s, 6H), 0.42 (s, 6H),
7.20–7.24 (m, 6H), 7.43–7.48 (m, 4H). 13C-NMR
(C6D6) (The methyl carbons of Me2PhSiꢀ groups are
diastereotopic.): l −12.07, −1.41 and −1.36,
0.24, 128.05, 128.74, 134.07, 140.56. 29Si-NMR
(C6D6): l −86.4, −15.5, −11.9. MS: m/e 386
[M+, 46], 371 [M+−Me, 18], 313 [M+−SiMe3,
15], 298 (3), 251 [M+−SiMe2Ph], 236 (72), 221
(22), 191 (39), 177 (57), 174 (68), 135 [Me2PhSi+,
100]. Anal. Calc. for C20H34Si4: C, 62.10; H, 8.86.
Found: C, 62.02; H, 8.67%.
To
a solution of 1, prepared from (diethyl-
amino)diphenylchlorosilane (2.2 mmol) and granular
lithium (10 mg-atom) in THF (3.0 ml) [4], was added
Et2O (1.6 ml), and then a solution of 8 (252 mg, 0.97
mmol) in Et2O (1.0 ml) was added at 0°C. This reaction
mixture was stirred at 0°C for 2 h and at r.t. overnight.
The reaction mixture was evaporated and the residue
was diluted with hexane (10 ml) and filtered. The
filtrate was concentrated in vacuo to give an 820 mg
1
mixture of 9 and 10: H-NMR analysis of the mixture
showed that the ratio of 9:10 was 86:14.
3.9. Synthesis of 3-trimethylsilyl-1,1,2,4,5,5-
hexaphenyl-1,2,3,4,5-pentamethylpentasilane (18)
3.8. Synthesis of 2-trimethylsilyl-1,3-diphenyl-1,1,2,3,3-
pentamethyltrisilane (15)
1. A solution of the mixed reagent prepared from 1
(2.1 mmol) in THF (3.5 ml) and i-PrMgBr in Et2O
(1.6 ml, 2.1 mmol) was added to a solution of the
crude 14 (382 mg, ca. 0.89 mmol), prepared as
above from 8 (4.4 mmol), in THF (5.0 ml) at 0°C
over 20 min. The reaction mixture was stirred at
0°C for 12 h and at r.t. overnight. To the reaction
mixture was added 1 M NaOH aq. solution (0.11
ml) at 0°C and the mixture was stirred at 0°C for 5
min. The mixture was dried over K2CO3 and con-
centrated to give crude 16 (832 mg) as an oil, which
was used in the next step without purification.
2. Through a solution of 16 (832 mg) in Et2O (10 ml)
was bubbled dry hydrogen chloride, generated from
ammonium chloride (7.25 g, 134 mmol) and concen-
trated sulfuric acid (6.00 ml, 108 mmol), at 0°C for
40 min with stirring. The mixture was diluted with
hexane (20 ml) and filtered. The filtrate was concen-
trated to afford crude 17 as an oil, which was used
in the next step without purification.
3. To a solution of 17 in Et2O (4.0 ml) was added
MeMgBr in Et2O (1.5 ml, 4.1 mmol) at r.t. over 5
min and the reaction mixture was stirred at r.t. for
30 min and refluxed for 6 h. After being cooled to
0°C, the reaction mixture was hydrolyzed with 1 M
hydrochloric acid (10 ml) and extracted with Et2O
(2×20 ml). The combined organic layer was
washed with brine (10 ml), water (10 ml), and dried
over MgSO4, and concentrated. The residue was
subjected to column chromatography on silica gel
1. To
a solution of 3, prepared from (diethyl-
amino)phenylmethylchlorosilane (2.9 mmol) and a
lithium dispersion (18 mg-atom) in THF (3 ml), was
added i-PrMgBr in Et2O (2.2 ml, 2.9 mmol) over 3
min at 0°C. The solution was stirred for 30 min to
afford a dark-brown solution of the mixed reagent.
To the solution was added 8 (217 mg, 1.1 mmol) in
THF (1.0 ml) at 0°C. The reaction mixture was then
stirred at 0°C for 2 h and at r.t. overnight. The
reaction mixture was diluted with hexane (20 ml),
stirred vigorously, and filtered. The filtrate was con-
centrated in vacuo to give crude 13 (600 mg) as a
colorless oil, which was used in the next step with-
out purification.
2. Through a solution of 13 (600 mg) in Et2O (10 ml)
was bubbled dry hydrogen chloride, generated from
ammonium chloride (4.1 g, 75 mmol) and concen-
trated sulfuric acid (3.2 ml, 58 mmol), at 0°C for 20
min with stirring. The mixture was diluted with
hexane (10 ml) and filtered. The filtrate was concen-
trated to afford crude 14 (455 mg) as an oil, which
1
was used in the next step without purification. H-
NMR (C6D6): l 0.096; 0.15; 0.18 (1:2:1), 0.34; 0.36
(1:1), 0.67; 0.70; 0.74; 0.76 (1:1:1:1). 29Si-NMR
(C6D6): l 18.90; 18.75; 18.57; 18.42 (1:1:1:1),
−11.51; −11.64 (3:1), −77.79; −77.87; −78.07
(1:2:1).
3. To a solution of 14 in Et2O (7.0 ml) was added
MeMgBr in Et2O (2.0 ml, 5.8 mmol) at r.t. over 7
min and the reaction mixture was refluxed for 4 h.

266
A. Kawachi, K. Tamao / Journal of Organometallic Chemistry 601 (2000) 259–266
Kuriyama, Chem. Lett. (1995) 293. (c) A. Sekiguchi, M. Nanjo,
(30 ml) eluted with 40:1 hexane–AcOEt (Rf=0.28)
and MPLC eluted with 40:1 hexane–AcOEt, which
afforded a mixture of the configurational isomers of
18 (303 mg) as an oil in an overall 43% yield based
on 8. The ratio of the isomers 18ll–18ul–18uu was
roughly estimated to be 1:3:1. An analytical sample
of the major isomer 18ul was obtained by the recy-
cling reverse-phase liquid chromatography eluted
C. Kabuto, H. Sakurai, J. Am. Chem. Soc. 117 (1995) 4195. (d)
J.B. Lambert, J.L. Pflug, J.M. Denari, Organometallics 15 (1996)
615. (e) M. Nanjo, A. Sekiguchi, Organometallics 17 (1998) 492.
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580. (b) K. Tamao, G.-R. Sun, A. Kawachi, S. Yamaguchi,
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1
with CH3CN. 18ul: H-NMR (C6D6): l −0.01 (s,
9H), 0.28 (s, 3H), 0.41 (s, 3H), 0.51 (s, 3H), 0.68 (s,
3H), 0.69 (s, 3H), 7.08–7.22 (m, 18H), 7.26–7.29
(m, 2H), 7.34–7.43 (m, 6H), 7.48–7.57 (m, 4H).
13C-NMR (CDCl3) (the phenyl carbons of the
MePh2Siꢀ groups are diastereotopic): l −8.55,
−5.39, −5.01, −3.50, −3.30, 0.49, 127.42 (2C),
127.49, 127.53, 127.62, 127.67, 127.87, 128.10,
128.48 (2C), 128.77, 128.82, 134.91 (2C), 135.11,
135.18, 135.27, 135.42, 136.68, 136.73, 137.16,
137.41 (2C), 137.52. 29Si-NMR (C6D6): l −76.0,
−40.0, −39.0, −19.1, −18.9, −10.9. MS: m/e
750 [M+, 6], 553 [M+−Ph, 80], 476 [M+−
SiPh2Me, 35], 433 [M+−SiPhMeSiPh2Me, 34], 197
(100). Anal. Calc. for C44H54Si6: C, 70.33; H, 7.24.
Found: C, 70.22; H, 7.14%.
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Acknowledgements
We thank the Ministry of Education, Science, Sports
and Culture, Japan, for the Grants-in-Aid for Scientific
Research (Grant nos. 07405043 and 09239103), and
Professor Y. Ito, Kyoto University, for the fruitful
discussions and support of this work.
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