Mg-promoted reductive coupling of aromatic carbonyl compounds with trimethylsilyl chloride and bis(chlorodimethylsilyl) compounds

Article abstract of DOI:10.1016/j.tet.2006.01.026

Mg-promoted reductive coupling of aromatic carbonyl compounds (1) with chlorosilanes, such as trimethylsilyl chloride (TMSCl:2), 1,2- bis(chlorodimethylsilyl)ethane (3) and 1,5-dichlorohexamethyltrisiloxane (4), in N,N-dimethylformamide (DMF) at room temperature brought about selective and facile reductive formation of both of carbon-silicon and oxygen-silicon bonds to give the corresponding α-trimethylsilylalkyl trimethylsilyl ethers (5) and cyclic siloxanes (6), (7) in moderate to good yields, respectively. The present facile and selective coupling may be initiated through electron transfer from Mg metal to aromatic carbonyl compounds (1).

Full text of DOI:10.1016/j.tet.2006.01.026

Tetrahedron 62 (2006) 3103–3111
Mg-promoted reductive coupling of aromatic carbonyl
compounds with trimethylsilyl chloride and
bis(chlorodimethylsilyl) compounds*
Tetsuro Uchida,a Yoshio Kita,b Hirofumi Maekawaa and Ikuzo Nishiguchia,
*
aDepartment of Chemistry, Nagaoaka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188, Japan
bOrient Chemical Industries, 8-1, Sanrahigashi-machi, Neyagawa, Osaka 572-8581, Japan
Received 23 November 2005; revised 9 January 2006; accepted 10 January 2006
Available online 13 February 2006
Abstract—Mg-promoted reductive coupling of aromatic carbonyl compounds (1) with chlorosilanes, such as trimethylsilyl chloride
(TMSCl:2), 1,2-bis(chlorodimethylsilyl)ethane (3) and 1,5-dichlorohexamethyltrisiloxane (4), in N,N-dimethylformamide (DMF) at room
temperature brought about selective and facile reductive formation of both of carbon–silicon and oxygen–silicon bonds to give the
corresponding a-trimethylsilylalkyl trimethylsilyl ethers (5) and cyclic siloxanes (6), (7) in moderate to good yields, respectively. The
present facile and selective coupling may be initiated through electron transfer from Mg metal to aromatic carbonyl compounds (1).
q 2006 Elsevier Ltd. All rights reserved.
1. Introduction
with TMSCl (2) in DMF at room temperature to give the
corresponding a-trimethylsilylalkyl trimethylsilyl ethers (5)
in good yields. Furthermore, Mg-promoted one-pot cycliza-
tion of aromatic carbonyl compounds (1), including
ketones, and esters, with bis(chlorodimethylsilyl) com-
pounds, such as 1,2-bis(chlorodimethylsilyl)ethane (3) or
1,5-dichlorohexamethyltrisiloxane (4), to give the corre-
sponding cyclic siloxane compounds (6, 7) in good yields,
respectively (Scheme 1).
Effective formation of a carbon–silicon bond is one of the
most attractive subjects in organic synthesis2 because of
much usefulness and important functions of organosilicon
compounds. It have been reported3 that carbon–silicon bond
formation was accomplished by treatment of carbonyl
compounds and activated olefins with an alkali metal such
as Li or Na in THF or DME as the solvent in the presence of
trimethylsilyl chloride (TMSCl), although selectivity and/or
yield of C-silylated products were not always satisfactory
and special caution was generally needed for treatment of
these alkali metals.
O
Mg
1
2
On the other hand, a variety of Mg-promoted carbon-
silylation of carbonyl compounds and activated olefins were
reported by Calas et al.,4 although carcinogenic hexam-
ethylphosphoric triamide (HMPA)5,6 was necessary to use
as the solvent.
OSiMe
SiMe
3
R
R
3
2
1
Me SiCl
3
+
R
R
DMF
2
5
1
Yield=82–14%
Me
Me
Si
Si
Me
Cl
Me
1
O
R
R
Si
Cl
2
Si
Mg
O
Me
Me
Me
6
Me
Me
We now wish to report a facile method for selective and
effective carbon–silicon bond formation through Mg-
promoted reductive coupling of carbonyl compounds (1)
2
1
+
R
R
3
DMF
Me
O
Me Me Me
Cl Si O Si O Si Cl
1
Si
1
Yield=73–39%
R
R
O
Si
Me
2
Me Me Me
Si
Me
O
* See, Ref. 1.
Me
Me
4
1
i
7
R =H, CH , C H , C H , OCH , OC H , O C H
3 7
Keywords: Silylation; Electron transfer; Aromatic carbonyl compounds;
Magnesium.
3
2
5
3
7
3
2
5
2
R =Aryl, Hetrocyclic
*
Corresponding author. Tel.: C81 258 47 9307; fax: C81 258 47 9300;
e-mail: nishiiku@vos.nagaokaut.ac.jp
Scheme 1.
0040–4020/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.01.026

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T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
2. Result and discussion
mixed diarylethanediol (9a) in good yields, respectively
(Scheme 2).
2.1. Mg-promoted reductive coupling of carbonyl
compounds with TMSCl
Me SiCl
3
O
H C OSiMe
KHSO
o
3
3
4
2
Ph CH
3
Ph SiMe
3
Mg, DMF
Yield=66 %
It was found that treatment of benzaldehyde (1a) with
TMSCl in the presence of commercially available mag-
nesium turnings for Grignard reagents in DMF at room
temperature brought about facile and selective reductive
formation of carbon–silicon and oxygen–silicon bonds to
give a-trimethylsilyloxyl benzyltrimethylsilane (5a) in a
82% yield. Among a variety of reactive metals such as Zn,
Al, and Mg, Mg showed the best result in present reaction,
and no or little formation of 5a was observed when Zn or Al
was employed instead of Mg. It may be noteworthy that any
reactions did not occur to recover 1a quantitatively when
TMSCl was absent in the reaction system. This reductive
coupling reaction was also considerably influenced by a
relative ratio of Mg, 2, and 1a. The best result for formation
of 3a was obtained when the relative proportion of Mg/2/1a
was 3:8:1.7 Employment of DMF as a solvent gave the best
result among acetonitrile, tetrahydrofuran, dimethoxyethane
and N,N-dimethyl-acetoamide.
150 C
1h
5h
Me Si
3
CH
2
Ph
8h
Yield=51 %
1) n-Bu NSiPh F
3 2
4
OMe
OH
p-MeOC H CHO
OSiMe
SiMe
3
6
4
H
Ph
3
Ph
+
2) H
OH
9a
Yield=82 %
5a
Scheme 2.
2.2. Mg-promoted one-pot cyclization of aromatic
carbonyl compounds with bis(chlorodimethylsilyl)
compounds (3, 4)
Under the similar optimized reaction conditions, a variety of
trimethylsilylated adducts 5a–l were efficiently obtained in
good to excellent yields, as shown in Table 1. It was quite
interesting that the present reaction readily proceeded with
not only aromatic aldehydes (1a–g) but also aromatic
ketones (1h–k) and ester (1l). The a-trimethylsilylalkyl
trimethylsilyl ethers (5) were readily hydrolyzed with an
acidic aqueous solution to the corresponding a-trimethyl-
silyl alcohols.
At the next step, use of bis(chlorodimethylsilyl) compounds
(3, 4) instead of TMSCl in the present cross coupling
brought about efficient and selective one-pot cyclization of
aromatic carbonyl compounds (1) to give the corresponding
cyclic siloxanes (6h–v, 7h–t) successfully.
Generally the reaction was carried out in anhydrous DMF at
room temperature with magnetically stirring under nitrogen
atmosphere for 20 h. Commercially available magnesium
turnings for Grignard reaction was also used without any
pre-treatment in the present cyclization. After usual work-
up of the reaction mixture, column chromatography of the
crude products gave the corresponding cyclic siloxanes
(6h–v, 7h–t) in 39–73% yields, as shown in Tables 2 and 3.
Table 1. Mg-promoted silylation of aldehydes, ketones and esters with
TMSCI (2)a
O
Mg
1
OSiMe
R
3
2
Me SiCl
1
3
+
R
R
2
SiMe
R
3
DMF
2
5
1
Table 2. Cyclization of aromatic carbonyl compounds in the presence of
1,2-bis(chlorodimethylsilyl)ethane (3)a
Entry
R1 in 1
R2 in 1
Yield of 5 (%)b
Me
Me
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
CH3
C2H5
C6H5
CH3
OC2H5
C6H5
o-ClC6H4
(1a)
(1b)
(1c)
(1d)
(1e)
(1f)
(1g)
(1h)
(1i)
82 (5a)
79 (5b)
75 (5c)
73 (5d)
54 (5e)
78 (5f)
52 (5g)
74 (5h)
14 (5i)c
68 (5j)
42 (5k)
56 (5l)
Me Me
Si
Si
O
Mg
O
1
Si
Cl
+
R
Cl
Si
Me Me
2
1
DMF
R
R
m-ClC6H4
p-ClC6H4
p-CF3C6H4
o-CH3OC6H4
2-Thienyl
C6H5
C6H5
C6H5
2-Thienyl
C6H5
2
Me
R
Me
6
3
1
Entry
R1 in 1
R2 in 1
Yield of 6 (%)b
1
2
3
4
5
6
7
8
CH3
CH3
CH3
CH3
C6H5
(1h)
(1m)
(1n)
(1o)
(1p)
(1i)
(1q)
(1l)
(1r)
(1s)
(1t)
43 (6h)
43 (6m)
43 (6n)
47 (6o)
49 (6p)
53 (6i)
48 (6q)
54 (6l)
73 (6r)
60 (6s)
69 (6t)
66 (6u)
73 (6v)
9
m-MeOC6H4
p-MeOC6H4
m-ClC6H4
p-ClC6H4
C6H5
C6H5
C6H5
m-MeOC6H4
p-MeC6H4
m-ClC6H4
C6H5
10
11
12
(1j)
(1k)
(1l)
CH3
a Reaction condition: substrate (5 mmol), trimethysilylchloride (2)
(8.0 equiv per mol), magnesium (3.0 equiv per mol), DMF (60 mL),
20 h, room temperature, under N2 atmosphere.
C2H5
C3H7
OC2H5
OC2H5
OC2H5
OC2H5
OCH3
OiC3H7
b Isolated yield.
9
c 4-Trimethylsilylpropiophenone was obtained in 20% yield.
10
11
12
13
(1u)
(1v)
The product 5a–l can be easily transformed to many useful
compounds such as esters, aldehydes, ketones, alcohols, and
ethers.8 For example, treatment of the product 5h with
KHSO4, and that of the product 5a with n-Bu4NSiPh3F2/
p-methoxybenzaldehyde gave a-silylstyrene (8h) and the
C6H5
a Reaction condition: substrate (5 mmol), 1,2-bis(chlorodimethylsilyl)-
ethene (3) (4.5 equiv per mol), magnesium (6.0 equiv per mol), DMF
(60 mL), 20 h, room temperature, under N2 atmosphere.
b GC yield.

T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
3105
Table 3. Cyclization of aromatic carbonyl compounds in the presence of
1,5-dichlorohexamethyltrisiloxane (4)a
Also, reduction potential of aromatic esters (1l, 1r–v) are
generally more positive (less reducible) than that of
aromatic aldehydes and ketones.
Me
Me
Si
1
O
Me Me Me
Cl Si O Si O Si Cl
Me Me Me
4
O
Mg
R
O
+
2
2
1
Me
Me
Si
This unexpected phenomenon observed in this study may be
probably attributed to some side-reactions11 of aromatic
aldehydes and ketones with bis(chlorodimethylsilyl) com-
pounds (3, 4), because our recent study12 showed that Mg-
promoted facile formation of enol trimethylsilyl ethers was
observed in the reaction of aromatic ketones with
trimethylsilyl choride under the similar conditions.
R
R
R
Si
DMF
O
Me
Me
1
7
Entry
R1 in 1
R2 in 1
Yield of 7 (%)b
1
2
3
4
5
6
7
8
9
CH3
CH3
CH3
CH3
C6H5
(1h)
(1m)
(1n)
(1w)
(1p)
(1l)
(1r)
(1s)
(1t)
43 (7h)
43 (7m)
43 (7n)
47 (7w)
49 (7p)
54 (7l)
73 (7r)
60 (7s)
69 (7t)
m-MeOC6H4
p-MeC6H4
p-MeC6H4
p-ClC6H4
C6H5
m-MeOC6H4
p-MeC6H4
m-ClC6H4
The reaction of aromatic aldehydes with bis(chloro-
dimethylsilyl) compounds (3, 4) may be possibly
accompanied with formation of pinacol type of complex
dimeric product mixtures, because of lower electrophilicity
of 3 and 4 in comparison with that of TMSCl as well as more
stability (longer life-time) of the anion radical of aromatic
aldehydes in comparison with that of aromatic esters.
CH3
OC2H5
OC2H5
OC2H5
OC2H5
a Reaction condition: substrate (5 mmol), 1,5-dichlorohexamethyltrisilox-
ane) (4) (4.5 equiv per mol), magnesium (6.0 equiv per mol), DMF
(60 mL), 20 h, room temperature, under N2 atmosphere.
b GC yield.
It may be also interesting that the presence of an electron-
withdrawing group on the phenyl ring of benzoic esters
brought about some increase in the yield of the cyclic
siloxanes (6, 7) (entries 9 and 11 of Table 1), although
similar substituent effect was not clearly observed in the
reaction of acetophenone derivatives. The yield is not
sensitive to a steric bulkiness of an alkoxy substituent of
benzoic esters (entries 11–13 of Table 1).
These cyclic siloxanes (6l–v, 7l–t) as well as non-cyclic
product 5l, the reductive coupling products from aromatic
esters, may be useful reagents in organic synthesis as
masked acyl silanes.9
It may be noteworthy tendency in the present cyclization
that the reaction of aromatic esters (1l, 1r–t) with both of
1,2-bis(chlorodimethylsilyl)ethane (3) and 1,5-dichlorohexa-
methyltrisiloxane (4) gave the corresponding cyclic silox-
anes (6l, 6r–t, 7l, 7r–t) in moderate to good yields (entries
8–13 in Table 2 and entries 6–9 in Table 3) while the similar
cyclic siloxanes (6h–p, 7h–w) were obtained in relatively
low yields from the reaction of aromatic ketones (1h, 1i,
1m–p, 1w) with bis(chlorodimethylsilyl) compounds (3, 4)
(entries 1–7 in Table 2 and entries 1–5 in Table 3).10
Although the detailed role of TMSCl (2) and bis(chloro-
dimethylsilyl) compounds (3 or 4) in this reaction still
remains ambiguous,13 the following reaction mechanism
may be proposed for the present Mg-promoted reductive
coupling and cyclization from these experimental results as
shown in Scheme 4. Cyclic voltammetry of the chloro-
silanes, TMSCl (2), 1,2-bis(chlorodimethylsilyl)ethane (3)
and 1,5-dichlorohexamethyltrisiloxane (4) do not give any
reduction peak up to 3.0 V versus Ag/AgC in DMF, while
aromatic aldehydes, ketones and esters show their reduction
peaks at K1.93, 2.10 and K2.36 V versus Ag/AgC in DMF,
respectively. Therefore, the first electron transfer from the
Mg-metal to aromatic carbonyl compounds (1) may
generate the corresponding anion radical, which may be
subjected to the first electrophilic attack by TMSCl (2), 1,2-
bis(chlorodimethylsilyl)ethane (3) or 1,5-dichlorohexa-
methyltrisiloxane (4) to the carbon atoms of carbonyl
compounds followed by the fast second electron transfer
giving the corresponding anionic intermediates (12). The
second electrophilic attack to the oxygen atoms of the
anonic intermediates (12) by TMSCl (2), 1,2-bis(chloro-
dimethylsilyl)ethane (3) or 1,5-dichlorohexamethyltrisiloxane
(4) gave the a-trimethylsilylalkyl trimethylsilyl ethers (5)
and final cyclic siloxane products (6, 7), respectively
(Scheme 2).
Furthermore, similar treatment of benzaldehydes with
bis(chlorodimethylsilyl) compounds (3, 4) led to formation
the corresponding cyclization products (6a, 7a) in 40 and
12% yields, respectively (Scheme 3).
Me
Me
Me
Me Me
Si
Si
Mg
O
O
H
Ph
Me
6a
Si
Cl
Cl
Si
+
Ph
H
H
DMF
Me Me
3
1a
Yield=40 %
Me
Me
Si
O
O
Me Me Me
Cl Si O Si O Si Cl
Me Me Me
4
Mg
H
O
+
Me
Ph
1a
Si
Ph
Me
DMF
Si
O
Me
Me
7a
Electrophilic attack of bis(chlorodimethylsilyl) compounds
(3, 4) to the oxygen atoms of the carbonyl anion radicals
(10) may generate a-silyloxy radicals (13), which may be
subjected to the second slower electron transfer to the
radical intermediate (13) giving the anion intermediate (15)
in comparison with the faster electron transfer to the radical
intermediate (16), giving the anion intermediate (11),
because of steric effect in the electron transfer process
Yield=12 %
Scheme 3.
This tendency was unusual since the reaction of aromatic
aldehydes with TMSCl gave better yields than the similar
reductive coupling of aromatic esters with the same reagent,
as shown above.

3106
T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
pattern, high selectivity, good yield and interesting
functions of the products, which may possess high
potentiality in organic chemistry.
R1
R2
Me3SiCl
Me3Si
OSiMe3
O
R1 R2
SiMe3
5
11
Me3SiCl
3. Experimental
3.1. General
( fast )
Mg (+e)
O
Me3Si
R2
SiMe3
R1
O
R1 R2
16
N,N-Dimethylformamide (DMF) was distilled from CaH2.
Unless otherwise mentioned, all the materials commercially
obtained were used without further purification. Organic
extracts were dried over anhydrous MgSO4 and concen-
trated under reduced pressure by a rotary evaporator. Flash
chromatography was carried out using Merck 60 (Mesh
230–400) silica gel. Reactants and chromatography frac-
tions were analyzed using precoated silica gel 60 F254 plates
(Merck). 1H NMR spectra at 270 and 400 MHz were
measured in the CCl4 and CDCl3 solutions. Chemical shifts
are expressed in ppm downfield from internal dichloro-
methane (5.32 ppm). The apparatus of cyclic voltammetry
was ASL model 600 (ASL).
17
Mg (+e)
Me3SiCl
Me3SiCl
O
Mg (+e)
O
R2
R1
R2
R1
1
10
Me Me
Me Me
Mg (+e) Cl Si Y Si Cl
Cl Si Y Si Cl
Me Me
3.2. Cyclic voltammetry analysis
Me Me
Cyclic voltammetry was performed in a beaker-type cell
equipped with Pt electrodes as the anode and the cathode, a
reference electrode (Ag/AgCl) at room temperature. The
solvent was DMF containing 1 wt% Bu4NClO4 as a
supporting electrolyte. Sweep rate was 200 mV/s.
Me
O
R2
Me
Me
Me
Si
Cl
Si
O
R1
R2
Cl
Me
Si
Y
Si
Me
R'
13
Me
Me
12
3.3. General procedure for synthesis of a-trimethylsilyl-
alkyl trimethylsilyl ethers (5)
Mg (+e)
( Slow )
Me
Me
A typical procedure is as follows. A solution containing
TMSCl (8 mmol) and Mg turnings (15 mmol) in 60 ml of
dry DMF was stirred under nitrogen atmosphere. A DMF
solution of benzaldehyde (1a) (10 mmol/5 ml) was drop-
wise added to the solution for 1 h at room temperature,
which was then stirred for about 4 h. Then the reaction
mixture was poured into 200 ml of a saturated aqueous
ammonium chloride solution and was extracted by three
100 ml portions of ether. Usual work-up and subsequent
column chromatography or distillation of the residue gave
a-trimethylsilyl-a-trimethyl-siloxytoluene (5a) in a good
yield with formation of a small amount of the homo-
coupling by-product, 1,2-diphenyl-1,2-ethanediol.
O
Me
O
R2
R
Si
Y
Me
Si
Si
Cl
Me
Me
Me
Si
Me
6 or 7
X
R'
15
Dimerization
- H
(Oligomerization)
Further reactions
Me
Me
Si
O
Cl
Si
R2
Me
Me
R'
14
3.3.1. a-Trimethylsilyl-a-trimethylsiloxytoluene (5a). 1H
NMR (CCl4, 270 MHz) d (ppm): 0.07 (9H, s), 0.14 (9H, s),
4.56 (1H, d), 7.18–7.50 (5H, m). 13C NMR (CCl4,
67.5 MHz) d (ppm): K4.13, 0.00, 70.29, 124.83, 125.09,
127.40, 144.38. IR (neat) n (cmK1): 1250, 1050. MS m/z 252
(M). Anal. Calcd for C13H24OSi2: C, 61.84; H, 9.58. Found:
C, 62.05; H, 9.41.
Scheme 4.
from Mg metal.14 That may result in long-life time of the
radical intermediate (13), to give various type of side-
reactions such as dimerization, oligomerization, or elimi-
nation of hydrogen radicals in the case of aromatic ketones
giving reactive silyloxy enol ethers (14) under the reaction
conditions.
3.3.2. a-Trimethylsilyl-a-trimethylsiloxy-o-chloroto-
1
luene (5b). H NMR (CCl4, 270 MHz) d (ppm): 0.03 (9H,
s), 0.03 (9H, s), 4.99 (1H, s), 7.01–7.48 (4H, m). 13C NMR
(CCl4, 67.5 MHz) d (ppm): K3.74, K0.12, 66.04, 126.29,
126.45, 127.98, 128.81, 129.94, 142.32. IR (neat) n (cmK1):
1250, 1055. MS m/z 286 (MC). Anal. Calcd for C13H23-
ClOSi2: C, 54.41; H, 8.08. Found: C, 54.26; H, 8.25.
In conclusion, we have successfully developed one-pot
selective formation of carbon–silicon and oxygen–silicon
bonds and efficient novel cyclization, that are initiated by
electron transfer from Mg metal. The present reactions may
be characterized by simple procedure, unique reaction

T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
3107
3.3.3. a-Trimethylsilyl-a-trimethylsiloxy-m-chrolo-
7.38–7.41 (10H, m). 13C NMR (CCl4, 67.5 MHz) d (ppm):
1.82, 86.84, 128.24, 128.33, 128.46, 140.79. IR (neat) n
(cmK1): 2950, 1740, 1490, 1445, 1250, 895, 840, 700. MS
m/z 328 (MC). Anal. Calcd for C19H28OSi2: C, 69.45; H,
8.59. Found: C, 69.15; H, 8.41.
1
toluene (5c). H NMR (CCl4, 270 MHz) d (ppm): K0.04
(9H, s), 0.03 (9H, s), 4.41 (1H, s), 6.98–7.26 (4H, m). 13C
NMR (CCl4, 67.5 MHz) d (ppm): K4.17, K0.03, 69.83,
122.86, 124.74, 125.27, 128.97, 133.82, 146.77. IR (neat) n
(cmK1): 1250, 1055. MS m/z 286 (M). Anal. Calcd for
C13H23ClOSi2: C, 54.41; H, 8.08. Found: C, 54.11; H, 8.36.
3.3.11. a-Trimethylsilyl-a-trimethylsiloxy-2-ethylthio-
phene (5k). 1H NMR (CCl4, 270 MHz) d (ppm): 0.01
(9H, s), 0.12 (9H, s), 1.73 (1H, s), 6.67 (1H, dd, JZ1.0,
3.6 Hz), 7.00 (1H, dd, JZ3.6, 5.0 Hz), 7.12 (1H, dd, JZ1.0,
5.0 Hz). 13C NMR (CCl4, 67.5 MHz) d (ppm): K4.40, 2.55,
25.18, 71.89, 120.32, 122.03, 126.49, 154.27. IR (neat) n
(cmK1): 1250, 1040. MS m/z 272 (MC). Anal. Calcd for
C12H24OSSi2: C, 52.88; H, 8.88. Found: C, 53.01; H, 8.93.
3.3.4. a-Trimethylsilyl-a-trimethylsiloxy-p-chloro-
toluene (5d). H NMR (CCl4, 270 MHz) d (ppm): K0.03
1
(9H, s), 0.04 (9H, s), 4.43 (1H, s), 7.09 (2H, d, JZ8.4 Hz),
7.24 (2H, d, JZ8.4 Hz). 13C NMR (CCl4, 67.5 MHz) d
(ppm): K4.18, 0.02, 69.79, 126.07, 127.92, 130.67, 143.02.
IR (neat) n (cmK1): 1245, 1050. MS m/z 286 (MC). Anal.
Calcd for C13H23ClOSi2: C, 54.41; H, 8.08. Found: C,
54.36; H, 8.11.
3.3.12. a-Ethoxy-a-trimethylsiloxy-a-trimethylsiloxy-
toluene (5l). 1H NMR (CCl4, 270 MHz) d (ppm): 0.04
(9H, s), 0.21 (9H, s), 1.28–1.32 (3H, m), 3.50–3.55 (2H, m),
7.16–7.54 (5H, m). 13C NMR (CCl4, 67.5 MHz) d (ppm):
K2.49, 2.21, 15.55, 58.96, 104.30, 124.77, 126.61, 127.33,
143.91. IR (neat) n (cmK1): 2950, 1250, 1100, 1040,
840 cmK1. MS m/z 267 ((MKOEt)C). Anal. Calcd for
C15H28O2Si2: C, 60.75; H, 9.25. Found: C, 60.72; H, 9.20.
3.3.5. a-Trimethylsilyl-a-trimethylsiloxy-p-trifluoro-
methyltoluene (5e). H NMR (CCl4, 270 MHz) d (ppm):
1
K0.04 (9H, s), 0.11 (9H, s), 4.61 (1H, s), 7.34 (2H, d, JZ
8.1 Hz), 7.59 (2H, d, JZ8.1 Hz). IR (neat) n (cmK1): 1250,
1050. MS m/z 320 (MC). Anal. Calcd for C14H23F3OSi2: C,
52.47; H, 7.23. Found: C, 54.26; H, 7.11.
3.3.6. a-Trimethylsilyl-a-trimethylsiloxy-o-methoxyl-
toluene (5f). H NMR (CCl4, 270 MHz) d (ppm): K0.05
1
3.4. Procedure for synthesis of a-trimethylsilylstylene
(8h)
(9H, s), 0.02 (9H, s), 3.78 (3H, s), 4.94 (1H, s), 6.78 (1H, dd,
JZ1.0, 7.6 Hz), 6.93 (1H, ddd, JZ7.6, 7.6, 1.0 Hz), 7.11
(1H, ddd, JZ1.3, 6.0, 7.6 Hz), 7.34 (1H, dd, JZ1.3,
7.6 Hz). 13C NMR (CCl4, 67.5 MHz) d (ppm): K3.88,
K0.05, 54.72, 63.27, 109.08, 120.29, 125.57, 126.52,
133.10, 154.30. IR (neat) n (cmK1): 1250, 1050. MS m/z
267 (MKMe)C). Anal. Calcd for C14H26O2Si2: C, 59.52; H,
9.28. Found: C, 59.80; H, 9.03.
A solution containing 5h (10 mmol) and 6 N HCl aqueous
(2 ml) in 20 ml of dry DMF was stirred for 8 h under a
nitrogen atmosphere. Then the reaction mixture was poured
into 200 ml of a saturated NaHCO3 solution and was
extracted by three 100 ml portions of ether. Usual work-up
and subsequent evaporation of ether under reduced pressure
gave the a-hydroxy-a-trimethylsilylethylbenzenein a 66%
yield. Then anhydrous KHSO4 and a-hydroxy-a-trimethyl-
silylethylbenzene was stirred at 150 8C in vacuo
(10 mmHg). Distillation of reaction mixture gave the 8h
in a 55% yield.
3.3.7. a-Trimethylsilyl-a-trimethylsiloxy-2-methylthio-
phene (5g). 1H NMR (CCl4, 270 MHz) d (ppm): 0.03
(9H, s), 0.07 (9H, s), 4.71 (1H, s), 6.71 (1H, dd, JZ1.0,
3.5 Hz), 6.93 (1H, dd, JZ3.5, 4.6 Hz), 7.10 (1H, dd, JZ1.0,
4.6 Hz). 13C NMR (CCl4, 67.5 MHz) d (ppm): K4.08,
K0.02, 66.90, 120.59, 122.10, 126.36, 148.95. IR (neat) n
(cmK1): 1250, 1050. MS m/z 258 (MC). Anal. Calcd for
C11H22OSSi2: C, 51.10; H, 8.58. Found: C, 51.23; H, 8.62.
3.4.1. a-Trimethylsilylstylene (8h). 1H NMR (CCl4,
270 MHz) d (ppm): 0.20 (9H, s), 5.62 (1H, d, JZ3.0 Hz),
5.81 (1H, d, JZ3.0 Hz), 7.20–7.35 (5H, m). 13C NMR
(CCl4, 67.5 MHz) d (ppm): K0.88, 126.22, 126.69, 127.13,
144.76, 128.14, 153.51. IR (neat) n (cmK1): 2950, 1400,
1250, 840, 680 cmK1. MS m/z 176 (MC). Anal. Calcd for
C11H16Si: C, 74.93; H, 9.15. Found: C, 74.88; H, 9.27.
3.3.8. a-Trimethylsilyl-a-trimethylsiloxyethylbenzene
1
(5h). H NMR (CCl4, 270 MHz) d (ppm): 0.03 (9H, s),
0.19 (9H, s), 1.82 (3H, s), 7.18–7.39 (5H, m). 13C NMR
(CCl4, 67.5 MHz) d (ppm): K4.36, 2.84, 24.08, 73.10,
124.87, 124.98, 127.57, 148.07. IR (neat) n (cmK1): 1250,
1050. MS m/z 209 ((MK57)C). Anal. Calcd for
C14H26OSi2: C, 63.09; H, 9.83. Found: C, 63.20; H, 10.01.
3.5. Procedure for synthesis of 1-(4-methoxyphenyl)-2-
phenyl-ethane-1,2-diol (9a)
A solution containing 5a (1 mmol), p-methoxybenzal-
˚
dehyde (3 mmol) and powder MS 4 A (3 wt equiv) in
3.3.9. a-Trimethylsilyl-a-trimethylsiloxypropylbenzene
(5i). H NMR (CCl4, 270 MHz) d (ppm): K0.39 (9H, s),
1
20 ml of dry THF was stirred for 2 h under nitrogen
atmosphere. Then n-Bu4NSiPh3F2 (2 mmol) was added to
the solution at room temperature, and the mixture was
stirred for another 2 h. After removal of THF, MeOH
(20 ml) and acetic acid (0.3 ml) were added to the solution
at room temperature, the resulting mixture was stirred for
K0.12 (9H, s), 0.55 (3H, d, JZ7.3 Hz), 1.73–1.83 (2H, m),
6.78–7.00 (5H, m). 13C NMR (CCl4, 67.5 MHz) d (ppm):
K3.72, 2.19, 8.52, 18.23, 78.44, 124.60, 125.32, 127.44,
145.44. IR (neat) n (cmK1): 2940, 1250, 1120, 1050, 1020,
835. MS m/z 280 (MC). Anal. Calcd for C15H28OSi2: C,
64.22; H, 10.06. Found: C, 64.05; H, 11.0.
˚
about 8 h. Subsequent removal of MS 4 A by filtration and
that of the solvent by distillation from the reaction mixture
gave a crude oil. Purification of the crude oil by the column
chromatography to gave 9a in a 82% yield.
3.3.10. Diphenyl-trimethylsilyl-trimethyloxymethane
(5j). H NMR (CCl4, 270 MHz) d (ppm): 0.04 (18H, s),
1

3108
T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
3.5.1. 1-(4-Methoxyphenyl)-2-phenyl-ethane-1,2-diol
(9a).15 One isomer was isolated by recrystallization
(hexnane–AcOEt).
1.55, 5.78, 9.41, 20.95, 26.79, 72.96, 123.68, 128.37,
133.93, 145.73. IR (neat) n (cmK1): 3088, 3021, 2959,
2903, 1508, 1445, 1414, 1366, 1249, 1183, 1117, 1076,
1050. MS m/z 278 (MC). Anal. Calcd for C15H26OSi2: C,
64.68; H, 9.41. Found: C, 64.45; H, 9.19.
1H NMR (CDCl3, 400 MHz) d (ppm): 2.10 (1H, d, JZ
2.8 Hz), 2.15 (1H, d, JZ2.8 Hz), 3.77 (3H, s), 4.78 (1H, dd,
JZ2.8, 2.8 Hz), 4.81 (1H, dd, JZ2.8, 2.8 Hz), 6.84–6.88
(2H, m), 7.18–7.22 (2H, m), 7.26–7.35 (5H, m). 13C NMR
(CDCl3, 100 MHz) d (ppm): 55.26, 77.81, 78.12, 113.69,
127.07, 128.08, 128.26, 128.32, 131.81, 139.93, 159.46. IR
(neat) n (cmK1): 3350, 1460, 1040. MS m/z 244 (M). Mp:
129.2–131.0 8C (lit.: 135 8C).
3.6.4. 3-(2,2,5,5,6-Pentamethyl-1-oxa-2,4-disilacyclohex-
6-yl)-chlorobenzene (6o). H NMR (CDCl3, 400 MHz) d
1
(ppm): K0.31 (3H, s), 0.10 (3H, s), 0.25 (6H, s), 0.75–1.19
(4H, m), 1.67 (3H, s), 7.10–7.29 (4H, m). 13C NMR (CDCl3,
100 MHz) d (ppm): K6.41, K4.19, 0.49, 1.48, 5.68, 9.23,
26.70, 72.92, 121.88, 124.01, 124.78, 128.88, 133.88,
151.19. IR (neat) n (cmK1): 3068, 2959, 2903, 1592,
1567, 1476, 1453, 1416, 1368, 1250, 1213, 1112, 1065,
1051. MS m/z 298 (MC, 35Cl), 300 (MC, 37Cl). Anal. Calcd
for C14H23ClOSi2: C, 56.25; H, 7.75. Found: C, 56.11; H,
7.67.
3.6. General procedure for synthesis of cyclic
siloxane (6,7)
To a 100 ml three-necked round flask equipped with a
thermometer and a dropping funnel was placed aromatic
carbonyl compound (1) (5 mmol) and magnesium turnings
(30 mmol) in dry DMF (40 ml). After cooling the flask in a
ice bath, 1,2-bis(chlorodimethylsilyl)ethane (3) or 1,5-
dichloro-hexamethyltrisiloxane (4) (22.5 mmol) in DMF
(20 ml) was added under magnetic stirring over 20 min. The
resulting solution was stirred for 20 h at room temperature
under nitrogen atmosphere. After stirring, the reaction
solution was added in NaHCO3 aqueous (300 ml) over
30 min and was extracted with ether. After evaporation of
ether under reduced pressure, column chromatography of
the crude products (eluent; hexane/EtOAcZ20:1 or 10:1)
gave the corresponding cyclic siloxane (6,7). All new
3.6.5. 4-(2,2,5,5,6-Pentamethyl-1-oxa-2,4-disilacyclohex-
6-yl)-chlorobenzene (6p). H NMR (CDCl3, 400 MHz) d
1
(ppm): K0.33 (3H, s), 0.08 (3H, s), 0.24 (3H, s), 0.26 (3H,
s), 0.92 (4H, m), 1.67 (3H, s), 7.19–7.28 (4H, m). 13C NMR
(CDCl3, 100 MHz) d (ppm): K6.43, K4.26, 0.51, 1.48,
5.64, 9.28, 26.62, 72.88, 125.19, 127.74, 130.32, 147.42. IR
(neat) n (cmK1): 3084, 2959, 2903, 2801, 1899, 1486, 1445,
1397, 1367, 1250, 1216, 1172, 1115, 1092, 1074, 1049,
1011, 1074, 1049. MS m/z 298 (MC, 35Cl), 300 (MC, 37Cl).
Anal. Calcd for C14H23ClOSi2: C, 56.25; H, 7.75. Found: C,
56.28; H, 7.61.
products were identified by spectroscopic methods (1H, 13
NMR, IR, MASS) and elemental analysis.
C
3.6.6. 4-(6-Ethyl-2,2,5,5-tetramethyl-1-oxa-2,4-disilacyclo-
hex-6-yl)benzene (6i). 1H NMR (CDCl3, 400 MHz) d
(ppm): K0.38 (3H, s), 0.09 (3H, s), 0.26 (6H, s), 0.72 (3H, t,
JZ7.0 Hz), 0.78–1.07 (4H, m), 2.12 (2H, m), 7.10–7.32
(5H, m). 13C NMR (CDCl3, 100 MHz) d (ppm): K6.41,
K4.24, 0.60, 0.71, 5.85, 6.37, 9.42, 29.91, 76.23, 124.27,
124.28, 127.63, 146.26. IR (neat) n (cmK1): 3084, 3057,
3020, 2962, 2934, 2904, 1599, 1492, 1444, 1418, 1372,
1249, 1103, 1089, 1056, 1008. MS m/z 278 (MC). Anal.
Calcd for C15H26OSi2: C, 64.68; H, 9.41. Found: C, 64.44;
H, 9.21.
3.6.1. 2,2,5,5,6-Pentamethyl-1-oxa-2,4-disilacyclohex-6-
yl-benzene (6h). 1H NMR (CDCl3, 400 MHz) d (ppm):
K0.33 (3H, s), 0.09 (3H, s), 0.25 (3H, s), 0.26 (3H, s), 0.84–
1.05 (4H, m), 1.70 (3H, s), 7.11–7.33 (5H, m). 13C NMR
(CDCl3, 100 MHz) d (ppm): K6.38, K4.22, 0.54, 1.53,
5.75, 9.36, 26.67, 73.09, 123.72, 124.64, 127.67, 148.70. IR
(neat) n (cmK1): 3085, 3057, 3020, 2959, 2903, 1600, 1491,
1444, 1416, 1367, 1249, 1115, 1093, 1066, 1051. MS m/z
264 (MC). Anal. Calcd for C14H24OSi2: C, 63.57; H, 9.15.
Found: C, 63.30; H, 9.04.
3.6.7. 6-Propyl-2,2,5,5-tetramethyl-1-oxa-2,4-disilacyclo-
hex-6-ylbenzene (6q). 1H NMR (CDCl3, 400 MHz) d
(ppm): K0.39 (3H, s), 0.07 (3H, s), 0.11 (3H, s), 0.25
(3H, s), 0.74–1.09 (8H, m), 1.37–1.49 (1H, m), 1.98–2.06
(2H, m), 7.09–7.14 (1H, m), 7.21–7.31 (4H, m). 13C NMR
(CDCl3, 100 MHz) d (ppm):K6.55, K4.24, K0.35, 0.57,
5.81, 9.41, 14.36, 15.04, 39.82, 76.15, 124.06, 124.25,
127.62, 146.69. IR (neat) n (cmK1): 3084, 3058, 3020, 2957,
2905, 2873, 2360, 1598, 1493, 1465, 1444, 1418, 1250,
1132, 1117, 1058, 1030. MS m/z 292 (MC). Anal. Calcd for
C16H28OSi2: C, 65.69; H, 9.65. Found: C, 65.43; H, 9.40.
3.6.2. 3-(2,2,5,5,6-Pentamethyl-1-oxa-2,4-disilacyclohex-
6-yl)-methoxybenzene (6m). H NMR (CDCl3, 400 MHz)
1
d (ppm): K0.31 (3H, s), 0.10 (3H, s), 0.25 (3H, s), 0.26 (3H,
s), 0.79–1.04 (4H, m), 1.68 (3H, s), 3.82 (3H, s), 6.69 (1H,
ddd, JZ0.8, 2.8, 8.0 Hz), 6.82 (1H, ddd, JZ0.8, 2.8,
8.0 Hz), 6.91 (1H, dd, JZ1.6, 2.8 Hz), 7.21 (1H, t,
JZ8.0 Hz). 13C NMR (CDCl3, 100 MHz) d (ppm):
K6.36, K4.11, 0.54, 1.49, 5.78, 9.33, 26.75, 73.13,
109.65, 110.08, 116.28, 128.57, 150.72, 159.27. IR (neat)
n (cmK1): 3078, 2956, 2903, 2832, 1600, 1579, 1482, 1464,
1431, 1367, 1313, 1284, 1250, 1195, 1162, 1050. MS m/z
294 (MC). Anal. Calcd for C15H26O2Si2: C, 61.17; H, 8.90.
Found: C, 60.94; H, 8.80.
3.6.8. 6-Ethoxy-2,2,5,5-tetramethyl-1-oxa-2,4-disilacyclo-
hex-6-ylbenzene (6l). 1H NMR (CDCl3, 400 MHz) d
(ppm): K0.36 (3H, s), 0.12 (3H, s), 0.26 (3H, s), 0.29
(3H, s), 0.77–0.96 (3H, m), 1.15 (3H, t, JZ7.0 Hz), 1.19–
1.24 (1H, m), 3.18 (1H, dq, JZ7.2, 9.2 Hz), 3.46 (1H, JZ
7.2, 9.2 Hz), 7.20 (1H, m), 7.32 (3H, m). 13C NMR (CDCl3,
100 MHz) d (ppm):K6.04, K4.96, K0.07, K0.02, 5.25,
9.18, 15.21, 55.29, 102.58, 125.99, 126.07, 127.70, 143.11.
IR (neat) n (cmK1): 3089, 3024, 2963, 2923, 2868, 1600,
3.6.3. 4-(2,2,5,5,6-Pentamethyl-1-oxa-2,4-disilacyclohex-
6-yl)-toluene (6n). H NMR (CDCl3, 400 MHz) d (ppm):
1
K0.33 (3H, s), 0.08 (3H, s), 0.24 (3H, s), 0.25 (3H, s), 0.75–
1.07 (4H, m), 1.67 (3H, s), 2.33 (3H, s), 7.09–7.17 (4H, m).
13C NMR (CDCl3, 100 MHz) d (ppm): K6.32, K4.19, 0.57,

T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
3109
1509, 1454, 1406, 1369, 1259, 1224, 1210, 1184, 1124,
1054. MS m/z 294 (MC). Anal. Calcd for C15H26O2Si2: C,
61.17; H, 8.90. Found: C, 60.92; H, 8.99.
n (cmK1): 3058, 3064, 3022, 2967, 2907, 2879, 1484, 1466,
1445, 1419, 1378, 1366, 1250. MS m/z 308 (MC). Anal.
Calcd for C16H28O2Si2: C, 62.28; H, 9.15. Found: C, 62.01;
H, 9.33.
3.6.9. 3-(6-Ethoxy-2,2,5,5-tetramethyl-1-oxa-2,4-disila-
cyclohex-6-yl)methoxybenzene (6r). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.33 (3H, s), 0.14 (3H, s), 0.26 (3H,
s), 0.29 (3H, s), 0.77–0.96 (3H, m), 1.16 (3H, t, JZ7.0 Hz),
1.19–1.24 (1H, m), 3.20 (1H, dq, JZ7.2, 9.2 Hz), 3.46 (1H,
dq, JZ7.2, 9.2 Hz), 6.75–6.78 (1H, m), 6.90–6.93 (2H, m),
7.23–7.29 (1H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm):K6.05, K4.86, K0.07, K0.02, 5.22, 9.12, 15.22,
55.09, 55.36, 102.47, 111.19, 111.85, 118.54, 128.65,
145.02, 159.28. IR (neat) n (cmK1): 3078, 2956, 2897,
2832, 1599, 1581, 1484, 1465, 1433, 1419, 1387, 1284,
1250. MS m/z 324 (MC). Anal. Calcd for C16H28O3Si2: C,
59.21; H, 8.93. Found: C, 58.97; H, 8.93.
3.6.14. 2,2,5,5-Pentamethyl-1-oxa-2,4-disilacyclohex-6-
yl-benzene (6a). H NMR (CDCl3, 400 MHz) d (ppm):
1
K0.16 (3H, s), 0.01 (3H, s), 0.24 (3H, s), 0.25 (3H, s), 0.78–
1.68 (4H, m), 4.78 (1H, s), 7.11–7.33 (5H, m). 13C NMR
(CDCl3, 100 MHz) d (ppm): K8.08, K4.17, K3.20,
K0.72, 7.54, 9.33, 71.13, 124.27, 125.09, 127.87, 143.27.
IR (neat) n (cmK1): 3083, 3061, 3023, 2957, 2900, 2822,
1601, 1439, 1449, 1415, 1249, 1204, 1157, 1076, 1048,
1024. MS m/z 250 (MC). Anal. Calcd for C13H22OSi2: C,
62.33; H, 8.85. Found: C, 62.51; H, 8.99.
3.6.15. 2,2,4,4,6,6,7-Heptamethyl-1,3,5-trioxa-2,4,6-trisi-
lacyclohept-7-ylbenzene (7h). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.10 (3H, s), 0.17 (3H, s), 0.18 (3H,
s), 0.21 (3H, s), 0.22 (3H, s), 0.25 (3H, s), 1.79 (3H, s), 7.17–
7.36 (5H, m). 13C NMR (CDCl3, 100 MHz) d (ppm):
K3.67, K2.71, 0.69, 0.94, 1.24, 2.59, 24.79, 75.40, 124.56,
125.18, 127.69, 146.83. IR (neat) n (cmK1): 3086, 3057,
3022, 2963, 2925, 2903, 2868, 1599, 1492, 1444, 1409,
1370, 1261, 1220, 1072. MS m/z 326 (MC). Anal. Calcd for
C14H26O3Si3: C, 51.48; H, 8.02. Found: C, 51.23; H, 7.98.
3.6.10. 4-(6-Ethoxy-2,2,5,5-tetramethyl-1-oxa-2,4-disila-
cyclohex-6-yl)methylbenzene (6s). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.35 (3H, s), 0.11 (3H, s), 0.25 (3H,
s), 0.29 (3H, s), 0.77–0.96 (3H, m), 1.14 (3H, t, JZ7.0 Hz),
1.19–1.23 (1H, m), 3.17 (1H, dq, JZ7.2, 9.2 Hz), 3.43 (1H,
dq, JZ7.2, 9.2 Hz), 7.09–7.20 (4H, m). 13C NMR (CDCl3,
100 MHz) d (ppm):K6.00, K4.93, K0.07, K0.01, 5.26,
9.22, 15.21, 21.12, 55.12, 102.57, 125.94, 128.41, 135.49,
140.12. IR (neat) n (cmK1): 3022, 2971, 2896, 2801, 1605,
1586, 1482, 1443, 1408, 1386, 1248. MS m/z 308 (MC).
Anal. Calcd for C16H28O2Si2: C, 62.28; H, 9.15. Found: C,
62.39; H, 9.31.
3.6.16. 3-(2,2,4,4,6,6,7-Heptamethyl-1,3,5-trioxa-2,4,6-
trisilacyclohept-7-yl)methoxybenzene (7m). 1H NMR
(CDCl3, 400 MHz) d (ppm): K0.07 (3H, s), 0.15 (3H, s),
0.18 (3H, s), 0.22 (3H, s), 0.24 (3H, s), 0.26 (3H, s), 1.79
(3H, s), 3.84 (3H, s), 6.73 (1H, ddd, JZ0.8, 2.8, 8.0 Hz),
6.89 (1H, ddd, JZ0.8, 2.8, 8.0 Hz), 6.99 (1H, dd, JZ1.6,
2.8 Hz), 7.24 (1H, t, JZ8.0 Hz). 13C NMR (CDCl3,
100 MHz) d (ppm): K3.59, K2.57, 0.68, 0.71, 0.93, 2.58,
24.87, 55.07, 75.42, 109.96, 111.07, 117.03, 128.59, 148.80,
159.21. IR (neat) n (cmK1): 3081, 2963, 2833, 1599, 1580,
1486, 1464, 1432, 1370, 1314, 1286, 1260, 1196, 1165,
1120, 1058, 1012. MS m/z 356 (MC). Anal. Calcd for
C15H28O4Si3: C, 50.52; H, 7.91. Found: C, 50.47; H, 7.69.
3.6.11. 3-(6-Ethoxy-2,2,5,5-tetramethyl-1-oxa-2,4-disila-
cyclohex-6-yl)chlorobenzene (6t). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.34 (3H, s), 0.12 (3H, s), 0.26 (3H,
s), 0.29 (3H, s), 0.77–0.96 (3H, m), 1.15 (3H, t, JZ7.0 Hz),
1.13–1.23 (1H, m), 3.12 (1H, dq, JZ7.2, 9.2 Hz), 3.45 (1H,
dq, JZ7.2, 9.2 Hz), 7.16–7.31 (4H, m). 13C NMR (CDCl3,
100 MHz) d (ppm):K6.05, K4.97, K0.11, K0.09, 5.14,
9.04, 15.17, 55.54, 102.07, 124.14, 126.13, 126.25, 128.99,
133.95, 145.56. IR (neat) n (cmK1): 3067, 2957, 2930, 2897,
1593, 1570, 1471, 1409, 1250. MS m/z 328 (MC, 35Cl), 330
(MC, 37Cl). Anal. Calcd for C15H25ClO2Si2: C, 54.76; H,
7.66. Found: C, 54.82; H, 7.43.
3.6.17. 3-(2,2,4,4,6,6,7-Heptamethyl-1,3,5-trioxa-2,4,6-
trisilacyclohept-7-yl)toluene (7n). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.09 (3H, s), 0.11 (3H, s), 0.16 (3H,
s), 0.21 (3H, s), 0.22 (3H, s), 0.25 (3H, s), 1.78 (3H, s), 2.37
(3H, s), 6.98–7.20 (4H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm): K3.62, K2.65, 0.69, 0.74, 0.95, 2.61, 21.80, 24.86,
75.37, 121.71, 125.28, 125.95, 127.59, 137.08, 146.81. IR
(neat) n (cmK1): 3023, 2963, 2923, 2867, 1604, 1586, 1487,
1455, 1409, 1370, 1259, 1174, 1058. MS m/z 340 (MC).
Anal. Calcd for C15H28O3Si3: C, 52.89; H, 8.29. Found: C,
52.63; H, 8.19.
3.6.12. 6-Methoxy-2,2,5,5-tetramethyl-1-oxa-2,4-disila-
cyclohex-6-ylbenzene (6u). H NMR (CDCl3, 400 MHz)
1
d (ppm): K0.33 (3H, s), 0.11 (3H, s), 0.27 (3H, s), 0.32 (3H,
s), 0.80–0.98 (3H, m), 1.16–1.25 (1H, m), 3.06 (3H, s),
7.21–7.37 (5H, m). 13C NMR (CDCl3, 100 MHz) d (ppm):
K6.09, K5.03, K0.07, K0.02, 5.23, 9.19, 48.25, 102.81,
126.14, 126.26, 127.76, 142.34. IR (neat) n (cmK1): 3058,
3063, 3023, 2958, 2905, 2878, 2822, 1599, 1494, 1482,
1446, 1415, 1249. MS m/z 280 (MC). Anal. Calcd for
C14H24O2Si2: C, 59.94; H, 8.62. Found: C, 59.72; H, 8.91.
3.6.18. 4-(2,2,4,4,6,6,7-Heptamethyl-1,3,5-trioxa-2,4,6-
trisilacyclohept-7-yl)toluene (7w). 1H NMR (CDCl3,
400 MHz) d (ppm): K0.09 (3H, s), 0.11 (3H, s), 0.16 (3H,
s), 0.20 (3H, s), 0.21 (3H, s), 0.24 (3H, s), 1.77 (3H, s), 2.34
(3H, s), 7.11–7.27 (4H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm): K3.64, K2.71, 0.69, 0.73, 0.95, 2.58, 20.95, 24.86,
75.24, 124.54, 128.42, 134.62, 143.83. IR (neat) n (cmK1):
3089, 3024, 2963, 2923, 2868, 1600, 1509, 1454, 1406,
1369, 1259, 1224, 1210, 1184, 1124, 1054. MS m/z 340
3.6.13. 6-Isoprpyl-2,2,5,5-tetramethyl-1-oxa-2,4-disila-
cyclohex-6-ylbenzene (6v). H NMR (CDCl3, 400 MHz)
1
d (ppm): K0.45 (3H, s), 0.21 (3H, s), 0.28 (3H, s), 0.33 (3H,
s), 0.74–0.95 (3H, m), 0.98 (3H, d, JZ6.0 Hz), 1.04–1.19
(1H, m), 1.11 (3H, d, JZ6.0 Hz), 3.91 (1H, sept, JZ
6.0 Hz), 7.19–7.38 (5H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm): K5.32, K4.14, 0.60, 1.46, 5.26, 8.51, 24.44, 25.29,
65.45, 102.86, 126.04, 126.16, 127.50, 144.36. IR (neat)

3110
T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
(MC). Anal. Calcd for C15H28O3Si3: C, 52.89; H, 8.29.
Found: C, 52.82; H, 8.01.
Calcd for C15H27ClO4Si3: C, 46.07; H, 6.96. Found: C,
45.98; H, 6.79.
3.6.19. 4-(2,2,4,4,6,6,7-Heptamethyl-1,3,5-trioxa-2,4,6-
trisilacyclohept-7-yl)chlorobenzene (7p). 1H NMR
(CDCl3, 400 MHz) d (ppm): K0.09 (3H, s), 0.12 (3H, s),
0.18 (3H, s), 0.23 (3H, s), 0.24 (3H, s), 0.26 (3H, s), 1.78
(3H, s), 7.16–7.32 (4H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm): K3.74, K2.77, 0.66, 0.71, 0.93, 2.57, 24.73, 75.18,
126.01, 127.78, 130.94, 145.54. IR (neat) n (cmK1): 3086,
3034, 2963, 2925, 2903, 2868, 1489, 1456, 1398, 1370,
1258. MS m/z 361 (MC, 35Cl), 363 (MC, 37Cl). Anal. Calcd
for C14H25ClO3Si3: C, 46.57; H, 6.98. Found: C, 46.49; H,
6.72.
3.6.24. 2,2,4,4,6,6,-Hexamethyl-1,3,5-trioxa-2,4,6-trisila-
cyclohept-7-ylbenzene (7a). 1H NMR (CDCl3, 400 MHz) d
(ppm): 0.02 (3H, s), 0.14 (3H, s), 0.19 (3H, s), 0.22 (6H, s),
0.27 (3H, s), 4.79 (1H, s), 7.13–7.22 (1H, m), 7.27–7.35
(4H, m). 13C NMR (CDCl3, 100 MHz) d (ppm): K4.69,
K2.41, K1.96, K0.57, 0.70, 0.92, 71.03, 124.71, 125.49,
127.91, 142.06. IR (KBr) n (cmK1): 3082, 3063, 3024, 3002,
2962, 2900, 2843, 1600, 1494, 1452, 1411, 1259. MS m/z
312 (MC). Anal. Calcd for C13H24O3Si3: C, 49.95; H, 7.74.
Found: C, 49.99; H, 7.85.
3.6.20. 7-Ethoxy-2,2,4,4,6,6,-hexamethyl-1,3,5-trioxa-
2,4,6-trisilacyclohept-7-ylbenzene (7l). H NMR (CDCl3,
1
Acknowledgements
400 MHz) d (ppm): K0.16 (3H, s), 0.16 (3H, s), 0.19 (3H,
s), 0.27 (6H, s), 0.31 (3H, s), 1.21 (3H, t, JZ7.0 Hz), 3.30–
3.37 (1H, m), 3.41–3.48 (1H, m), 7.22–7.38 (5H, m). 13C
NMR (CDCl3, 100 MHz) d (ppm): K2.71, K2.66, 0.68,
0.79, 0.99, 0.99, 15.34, 56.32, 126.63, 126.81, 127.70,
141.76. IR (neat) n (cmK1): 3064, 2965, 2899, 1259, 1206,
1126, 1090, 1037, 1014. MS m/z 356 (MC). Anal. Calcd for
C14H26O3Si3: C, 51.48; H, 8.02. Found: C, 51.23; H, 7.98.
This work was partially supported by the 21st Century
Center of Excellent (COE) Program of Nagaoka University
of Technology provided by The Ministry of Education,
Culture, Sports, Science and Technology, Japan.
References and notes
3.6.21. 3-(7-Ethoxy-2,2,4,4,6,6,-hexamethyl-1,3,5-trioxa-
2,4,6-trisilacyclohept-7-yl)methoxybenzene (7r). 1H
NMR (CDCl3, 400 MHz) d (ppm): K0.14 (3H, s), 0.15
(3H, s), 0.20 (3H, s), 0.26 (6H, s), 0.28 (3H, s), 1.20 (3H, t,
JZ7.0 Hz), 3.34 (1H, dq, JZ7.2, 9.2 Hz), 3.45 (1H, dq,
JZ7.2, 9.2 Hz), 3.83 (3H, s), 6.77–6.79 (1H, m), 6.94–6.96
(2H, m), 7.23–7.28 (1H, m). 13C NMR (CDCl3, 100 MHz) d
(ppm): K2.63, K2.52, 0.68, 0.79, 0.97, 1.00, 15.36, 55.13,
56.39, 103.74, 111.66, 112.80, 119.33, 128.65, 143.66,
159.24. IR (neat) n (cmK1):3079, 2963, 2901, 2833, 1599,
1582, 1487, 1465, 1433, 1314, 1285, 1258. MS m/z 386
(MC). Anal. Calcd for C16H30O5Si3: C, 49.70; H, 7.82.
Found: C, 49.89; H, 7.99.
1. A preliminary report: Ishino, Y.; Maekawa, H.; Takeuchi, H.;
Sukata, K.; Nishiguchi, I. Chem. Lett. 1995, 829.
2. (a) Pawlenko, S. Organo Silicon Chemistry; Walter de
Gruyter: Berlin, New York, 1986. (b) Colvin, E. W. Silicon
Reagents in Organic Synthesis; Academic: London, 1988. (c)
Negishi, E. Organometallics in Organic Synthesis; Wiley:
New York, 1980. (d) Weber, P. W. Silicon Reagents for
Organic Synthesis; Springer: Berlin, Heidelberg, New York,
1983. (e) Colvin, W. E. Silicon in Organic Synthesis;
Butterworths: London, 1981.
3. (a) Kuwajima, I.; Atsumi, K.; Anegami, I. J. Chem. Soc.,
Chem. Commun. 1974, 76. (b) Dunogues, J.; Calas, R.;
Duffaut, N.; Lapouyade, P. J. Organomet. Chem. 1973, 49, C9.
(c) Dunogues, J.; Ekouya, A.; Calas, R.; Duffaut, N.
J. Organomet. Chem. 1975, 87, 151. (d) Picard, J. P.;
Ekouya, A.; Dunogues, J.; Duffaut, N.; Calas, R.
J. Organomet. Chem. 1972, 93, 51. (e) Ekouya, A.;
Dunogues, J.; Duffaut, N.; Calas, R. J. Organomet. Chem.
1977, 142, C35. (f) Kuwajima, I.; Sato, T.; Minami, N.; Abe,
T. Tetrahedron Lett. 1976, 32, 1591. (g) Kuwajima, I.;
Minami, N.; Abe, T.; Sato, T. Bull. Chem. Soc. Jpn. 1978,
51, 2391.
3.6.22. 4-(7-Ethoxy-2,2,4,4,6,6,-hexamethyl-1,3,5-trioxa-
2,4,6-trisilacyclohept-7-yl)toluene (7s). H NMR (CDCl3,
1
400 MHz) d (ppm): K0.15 (3H, s), 0.15 (3H, s), 0.18
(3H, Si–CH3, s), 0.26 (6H, s), 0.31 (3H, s), 1.20 (3H, t,
JZ7.0 Hz), 2.38 (3H, s), 3.34 (1H, dq, JZ7.2, 9.2 Hz), 3.43
(1H, dq, JZ7.2, 9.2 Hz), 7.04–7.06 (1H, m), 7.14–7.28 (3H,
m). 13C NMR (CDCl3, 100 MHz) d (ppm): K2.68, K2.61,
0.69, 0.81, 1.01, 1.03, 15.37, 21.73, 56.26, 103.86, 123.96,
127.35, 127.42, 127.56, 137.17, 141.66. IR (neat) n (cmK1):
3024, 2964, 2900, 1605, 1587, 1484, 1444, 1410, 1387,
1258. MS m/z 370 (MC). Anal. Calcd for C16H30O4Si3: C,
51.85; H, 8.16. Found: C, 51.69; H, d 8.02.
4. (a) Calas, R.; Biran, C.; Dunogues, J.; Duffaut, N. C. R. Acad.
Sci. C, 1969, 269, 412. (b) Picard, J. P.; Calas, R.; Dunogues,
J.; Duffaut, N.; Gerval, J.; Lapouyade, P. J. Org. Chem. 1979,
44, 420. (c) Calas, R.; Dunogues, J.; Pillot, J. P.; Biran, C.;
Duffaut, N. J. Organomet. Chem. 1970, 25, 43.
3.6.23. 3-(7-Ethoxy-2,2,4,4,6,6,-hexamethyl-1,3,5-trioxa-
2,4,6-trisilacyclohept-7-yl)chlorobenzene (7t). 1H NMR
(CDCl3, 400 MHz) d (ppm): K0.15 (3H, s), 0.15 (3H, s),
0.19 (3H, s), 0.25 (3H, s), 0.26 (3H, s), 0.31 (3H, s), 1.20
(3H, t, JZ7.0 Hz), 3.28 (1H, m), 3.44 (1H, m), 7.21–7.35
(4H, m). 13C NMR (CDCl3, 100 MHz) d (ppm): K2.69,
K2.67, 0.64, 0.76, 0.94, 1.02, 15.31, 56.55, 103.34, 124.94,
126.79, 126.90, 128.97, 133.94, 144.27. IR (neat) n (cmK1):
3069, 2964, 2900, 1593, 1571, 1472, 1444, 1410, 1388,
1259, 1198. MS m/z 390 (MC, 35Cl), 392 (MC, 37Cl). Anal.
5. Calas et al. represented the used solvent, hexamethyl-
phosphortriamide ((Me2N)3PO) as the abbreviation HMPT in
their series of Mg-promoted reactions. However, the solvent,
(Me2N)3PO, is represented as carcinogenic hexamethylpho-
sphoric triamide (HMPA) and should be different from
hexamethylphosphorous triamide ((Me2N)3P) (HMPT),
which may be too expensive to use as solvent.6
6. Picard, J. P. J. Organomet. Chem. 1972, 34, 279.

T. Uchida et al. / Tetrahedron 62 (2006) 3103–3111
3111
7. Requirement for use of more than theoretical amount
(probably 1 or 2 equiv mol) of Mg-metal may be attributed
to low efficiency of electron transfer in a heterogenous reaction
system between Mg-metal and starting substrate and some
side-reactions such as Mg-promoted dimerization of chloro-
silanes to disilanes.
surprising phenomenon may be partially elucidated by much
higher reactivity of TMSCl in comparison with bis(chloro-
dimethylsilyl)ethane (3), as shown in unusual attack of
TMSCl to the p-position of reactive anion radical intermediate
of 1i.
11. Formation of a variety of by-products and tarric materials
resulted in relatively low yield of the desired products (6 and
7) in Mg-promoted cyclization of aromatic ketones with
dichlorosilanes (3 and 4).
8. (a) Tsuge, O.; Kanemasa, S.; Nagahama, H.; Tanaka, J. Chem.
Lett. 1984, 1803. (b) Ito, Y.; Nagatsuka, M.; Saegusa, T. J. Am.
Chem. Soc. 1980, 102, 863. (c) Yoshida, J.; Matsunaga, S.;
Isoe, S. Tetrahedron Lett. 1989, 30, 5293. (d) Schinger, D.;
Heathcock, H. C. Tetrahedron Lett. 1981, 22, 1881. (e) Page,
B. C. P.; Rosenthal, S.; Williams, V. R. Tetrahedron Lett.
1987, 28, 4455.
12. Ishino, Y.; Kita, Y.; Maekawa, H.; Ohno, T.; Yamasaki, Y.;
Miyata, T.; Nishiguchi, I. Tetrahedron Lett. 1999, 40, 1349.
13. In this reactions, three kind of roles for TMSCl may be
postulated; that is, activation of 1 as electrophiles by
coordination to the oxygen atom of the carbonyl group,
stabilization of anion intermediates, and activation of Mg
metal.
9. Picard, J.; Calas, R.; Dunogues, J.; Duffaut, N.; Gerval, J.;
Lapouyade, P. J. Org. Chem. 1979, 44, 420.
10. The present coupling of aromatic alkyl ketones (1h, 1i, 1q)
with bis(chlorodimethylsilyl)ethane (3) gave the correspond-
ing cyclic coupling products (6h, 6i, 6q) in similar yields,
although that of 1i with TMSCl gave the corresponding
product (5i) in only 14% yield, accompanying unusual
formation of 4-trimethylsilylpropiophenone (20%). This
14. Ring strain of the cyclic products from the reaction of
aromatic alkyl ketones (1) with bis(chlorodimethylsilyl)
compounds (3, 4) may be an additional effect for their lower
yield.
15. Imuta, M.; Ziffer, H. J. Org. Chem. 1978, 43, 33.