Novel highly stereoselective approach toward (Z)-1,2-bis(silyl)ethenes

Article abstract of DOI:10.1055/s-2006-950238

A new flexible and stereoselective protocol for the synthesis of the compounds of the general formula, (Z)-Ph₂RSiCH=CHSiRPh₂ (where R is an alkyl, alkenyl or alkoxy substituent) has been developed. The title compounds have been effic

Full text of DOI:10.1055/s-2006-950238

PAPER
3739
Novel Highly Stereoselective Approach toward (Z)-1,2-Bis(silyl)ethenes
S
tereoselectiv
i
A
ppr
o
o
ac
h
toward
t
Z
)-1,2
r
Pes awluć, Bogdan Marciniec,* Beata Dudziec, Grzegorz Hreczycho, Maciej Kubicki
Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
Fax +48(61)8291508; E-mail: marcinb@amu.edu.pl
Received 10 May 2006; revised 3 July 2006
1,2-bis(silyl)ethenes, development of more efficient and
Abstract: A new flexible and stereoselective protocol for the syn-
straightforward synthetic methods is of great significance.
thesis of the compounds of the general formula, (Z)-
Ph2RSiCH=CHSiRPh2 (where R is an alkyl, alkenyl or alkoxy sub-
stituent) has been developed. The title compounds have been effi-
In the last two decades we have developed the silylative
coupling reaction of vinylsilane derivatives in the pres-
ence of transition-metal complexes (e.g. ruthenium and
rhodium) initially containing or generating M–H and M–
Si bonds.7 This process under optimum conditions has be-
come an excellent method for the selective synthesis of
(E)-1,2-bis(silyl)ethenes,8 as well as macromolecular or-
ganosilicon compounds containing (E)-1,2-bis(silyl) frag-
ments,9 which can be used as interesting synthetic
reagents for organic synthesis and polymeric materials
(Scheme 1).
ciently
obtained
by
ruthenium
hydride
complex
[RuHCl(CO)(PCy3)2]-catalyzed (Z)-selective silylative coupling
cyclization of 1,2-bis(diphenylvinylsiloxy)ethane or N,N¢-dimeth-
yl-N,N¢-di(diphenylvinylsilyl)ethane-1,2-diamine to generate re-
spective disilacyclic platforms, followed by their reaction with
Grignard reagents or alcohols. (Z)-Bis(silyl)ethenes could not be
synthesized by a metathesis procedure.
Key words: vinylsilanes, silylative coupling, ruthenium complex,
Grignard reagent, cyclization
R
Vinylsilanes are a class of compounds that has attracted
significant attention in recent years as important interme-
diates in stereocontrolled organic synthesis.1 Over the last
few decades, considerable effort has been made to find
new routes for the preparation of these compounds and for
their selective reaction with different electrophiles. Due to
similar properties of 1,2-bis(silyl)ethenes to those of vi-
nylsilanes, they have gained significant attention as poten-
tial precursors in organic and organosilicon syntheses.2
Despite their importance, there is a only limited number of
access routes to doubly silylated ethenes. Conventional
approaches to (Z)-1,2-bis(silyl)ethenes involve catalytic
double silylation of alkynes3 and hydrosilylation of alky-
nylsilanes by hydrosilanes.3a,4 Unfortunately, (Z)-1,2-
bis(silyl)ethenes cannot be synthesized via homo-meta-
thesis reaction due to the inactivity of vinylsilanes in this
process.5 Several independent methods, e.g. stoichiomet-
ric reaction of alkoxytitanium(IV) complexes with bis(si-
lyl)acetylenes and silylcupration of alkynes have also
been investigated.6 However, application of these meth-
ods has been limited because of difficulties in accessing
stereo- and regiodefined isomers, owing to the possibility
of forming a mixture of two [b-(Z) and b-(E) in bis-silyla-
tion] or three [b-(Z), b-(E) and a- in hydrosilylation] iso-
meric bis(silyl)ethenes. The use of the above-mentioned
methods is hampered not only by formation of a mixture
of stereo- or regioisomers but also by the relatively high
cost of the starting acetylenic derivatives as well as plati-
num or palladium complexes, which mostly catalyze these
processes. Therefore, in view of the growing interest in
R
Si
R
R
Si
R
[Ru]
R
Si
R
Si
R
R
R
R
+
R
– H2C=CH2
R
Si
R
R
Si
R
[Ru]
R
Si
R
R
R
R
Si
R
X
X
Si
R
Si
R
X
– H2C=CH2
n
X = O, NH, (CH2)n, C6H4
[Ru] = [RuCl2(CO)3], [RuHCl(CO)(PCy3)2], [RuHCl(CO)2(PPh3)2]
Scheme 1 Synthesis of (E)-1,2-bis(silyl)ethenes
The silylative coupling reaction of vinyl organosilicon
compounds occurs by cleavage of the =C–Si bond of the
vinyl-substituted silicon compound and the activation of
the =C–H bond of the second vinylsilane molecule. The
mechanism of this reaction involves insertion of vinylsi-
lane into the M–H bond followed by b-silyl elimination,
which generates a M–Si species and ethylene, followed by
insertion of the second vinylsilane molecule into the M–
Si bond. In the last stage, elimination of the isomeric
bis(silyl)ethenes with regeneration of the initial M–H
complex takes place.10 During the course of our recent
studies on the silylative coupling cyclization of divinyl-
substituted organosilicon compounds, we have developed
new facile and efficient protocols for the synthesis of
alkyl-, aryl-, alkenyl- or alkoxy-substituted 1,1-bis(si-
lyl)ethenes using cyclic silyl ether or cyclic silyl amine.
These 1,1-bis(silyl)ethenes were selectively obtained by
ruthenium-catalyzed silylative coupling exo-cyclization
of divinyl-substituted monomers, followed by their reac-
tion with Grignard11a reagents or alcohols11b (Scheme 2).
SYNTHESIS 2006, No. 21, pp 3739–3745
x
x.
x
x
.
2
0
0
6
Advanced online publication: 09.10.2006
DOI: 10.1055/s-2006-950238; Art ID: T07806SS
© Georg Thieme Verlag Stuttgart · New York
Although the silylative coupling methodology reported so
far establishes a simple and convenient route for the selec-

3740
P. Pawluć et al.
PAPER
Me
Me
Me
Me
Si
Si
Me
X
Me
Me
RMgX
ROH
Si
Si
R
R
Me
Me
Me
Me
RuHCl(CO)(PR'3)n
85–92%
Si
Si
55–88%
X
X
X
Me
Me
Me
Me
Me
RO
X = O, NMe
Si
Si
OR
81–95%
Scheme 2 Synthesis of 1,1-bis(silyl)ethenes
XH
XH
tive synthesis of a wide range of (E)-1,2- and 1,1-bis(si-
lyl)ethenes, this particular procedure could not have been
applied in the synthesis of (Z)-1,2-bis(silyl) derivatives
which also seem to be desirable reagents in the organic
and organosilicon syntheses. Very recently we have re-
ported the first example of effective silylative coupling
cyclization of 1,1¢-(diphenylvinylsilyl)ferrocene to give
cyclic product containing a Z-vinylene bond between the
silicon atoms.12 Bulky phenyl substituents have apparent-
ly been the reason for such a regioselectivity of the prod-
uct isolated. However, this compound possesses a rigid
structure and cannot be functionalized to produce substi-
tuted (Z)-1,2-bis(silyl)ethenes. Therefore, the aim of the
paper is to extend the silylative coupling procedure to the
stereoselective synthesis of substituted (Z)-1,2-bis(si-
lyl)ethenes.
Et3N
Ph
+
2
Si
Si
X
X Si
pentane, r.t.,
or 40 °C,
2–24 h
Ph
Ph
Ph
Ph
Ph
Cl
1 X = O (80%)
2 X = NMe (78%)
Scheme 3 Synthesis of divinyl-substituted monomers
Ruthenium complexes [RuHCl(CO)(PPh3)3] (I),
[Ru(SiMe3)(Cl)(CO)(PPh3)2]
(II)
and
[Ru-
HCl(CO)(PCy3)2] (III) have recently been reported as ef-
fective catalysts for selective silylative coupling
cyclization11 and polycondensation8a of divinyl-substitut-
ed monomers. In view of the structural similarity of 1 and
2 to the earlier reported substrates, we expected com-
pounds 1 and 2 to also undergo the silylative coupling cy-
clization. The conditions for an effective transformation
of 1,2-bis(diphenylvinylsiloxy)ethane (1) and N,N¢-dimeth-
yl-N,N¢-di(diphenylvinylsilyl)ethane-1,2-diamine (2) in
the presence of ruthenium catalysts were optimized by
catalytic screenings of the substrate conversion and the
yield of cyclic product by using GC and GC-MS methods.
Generally, the catalysis of the initial hexacovalent ruthe-
The starting 1,2-bis(diphenylvinylsiloxy)ethane (1) and
N,N¢-dimethyl-N,N¢-di(diphenylvinylsilyl)ethane-1,2-di-
amine (2) were conveniently prepared by the reaction of
chlorodiphenylvinylsilane with ethylene glycol and N,N¢-
dimethylethane-1,2-diamine, respectively in the presence
of triethylamine in high yield, as outlined in Scheme 3.
Table 1 Silylative Coupling Cyclization of 1 and 2a
Compound 1
Compound 2
Catalyst
Time (h)
Yield of 3 (%)b
Time (h)
48
Yield of 4 (%)b
RuHCl(CO)(PPh3)3
48
24
48
24
48
24
36
24
36
24
48
0
10
0
15
18
16
25
42
100
22
48
45
72
RuHCl(CO)(PPh3)3/CuCl (5%)
RuHCl(CO)(PPh3)3/CuCl (5%)
Ru(SiMe3)(Cl)(CO)(PPh3)2
Ru(SiMe3)(Cl)(CO)(PPh3)2
RuHCl(CO)(PCy3)2
24
14
48
30
24
56
48
86
24
RuHCl(CO)(PCy3)2
100
72
48
c
RuHCl(CO)(PCy3)2
48
c
RuHCl(CO)(PCy3)2
100
88
36
RuHCl(CO)(PCy3)2/CuCl (5%)
RuHCl(CO)(PCy3)2/CuCl (5%)
24
100
48
a Reaction conditions: toluene, 110 °C, argon atmosphere, monomer/[Ru] = 100:1.
b Determined by GC.
c Without toluene, 110 °C, glass ampoule.
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PAPER
Stereoselective Approach toward (Z)-1,2-Bis(silyl)ethenes
3741
nium complex I was less effective than in the presence of (4) was determined on the basis of the 1H, 13C NMR and
coordinatively unsaturated pentacoordinated ruthenium DEPT spectra. Moreover, the cyclic silyl ether 3 proved to
complexes. Unexpectedly, the cyclization of the com- be a solid and yielded a crystal amenable to X-ray struc-
pounds 1 and 2 did not occur in the presence of the ruthe- ture determination (Figure 1).
nium hydride complex I. At 1 mol% catalyst loading an
outstanding catalytic activity was observed for the
pentacoordinated ruthenium hydride complex containing
tricyclohexylphosphine: [RuHCl(CO)(PCy3)2] (III).
However, the use of CuCl (5 mol%), reported to be an ef-
ficient co-catalyst for silylation of styrenes13a and vinyl-
boranes,13b caused a slight increase in the catalytic activity
of complex I, while when used with catalyst III it did not
appreciably affect the rate i.e. the efficiency of the silyla-
tive coupling cyclization (Table 1).
The silylative coupling cyclization of 1 successfully pro-
ceeded in the presence of [RuHCl(CO)(PCy3)2] (1 mol%),
without solvent, under argon atmosphere (glass ampoule)
and divinyl silyl ether 1 was exclusively transformed into
cyclic product 3 (Equation 1) in 36 hours at 110 °C. How-
Figure 1 A perspective view of the molecule 3. The anisotropic dis-
placement ellipsoids are drawn at 50% probability level, hydrogen
atoms are depicted as spheres of arbitrary radii.
Figure 1 shows the perspective view of the molecule 3.14
The C2–C3 bond length, of 1.355(5) Å proves that this is
a double bond, and the disposition of Si atoms around this
bond is cis [the torsion angle Si–C–Si is 1.5(6)°].
ever, toluene could also be employed without affecting ei-
ther the activity of the catalyst or the selectivity of this
process. Contrary to the above-mentioned process the si-
lylative coupling cyclization of 2 occurred efficiently only
in toluene, in the open system (Equation 2), however, it
required a longer reaction time (48 h).
To understand the role of the phenyl group in these studies
we synthesized, the analogous divinyl silyl ether (5) bear-
ing the methylphenylsilyl groups instead of the diphenyl-
silyl fragments. We performed the silylative coupling
cyclization of 5 under similar conditions as those applied
for the compound 1 {[RuHCl(CO)(PCy3)2] (1 mol%), tol-
uene, 110 °C, 24 h}. GC-MS and NMR analyses of the
products showed that silylative coupling cyclization of 5
(mixture of diastereoisomers) allows the synthesis of a
mixture of cyclic products 6a and 6b (meso- and racemic
mixture) containing endo-vinylene bond and 7a and 7b
(meso- and racemic mixture) containing exo-methylene
fragment between silicon atoms (Equation 3). Thus, the
selectivity of the silylative coupling cyclization depends
on the organyl group attached to silicon, producing stereo-
selectively the Z-vinylene product when the substituents
are phenyl groups (presumably due to steric effects) and
the mixture of products containing either Z-vinylene and
exo-methylene bond when both methyl and phenyl groups
are employed. It is worth noting that dimethylsilyl-substi-
tuted monomers under the same conditions led to the re-
gioselective formation of the product containing 1,1-
bis(silyl)ethene fragments.11
RuH(Cl)(CO)(PCy3)2
Ph
Ph
Ph
(1mol%)
Si
O
Si
O
Si
O
O Si
Ph
Ph
Ph
Ph
Ph
110 °C, 36 h
– CH2=CH2
1
3 (86%)
Equation 1 Synthesis of (Z)-2,2,5,5-tetraphenyl-1,6-dioxa-2,5-di-
silacyclooct-3-ene
RuH(Cl)(CO)(PCy3)2
Ph
Ph
Me
N
Me
N
(1mol%)
Si
N
Si
N
Ph
Ph
Si
Si
Ph
Ph
Ph toluene, 110 °C, 48 h
Me
Me
Ph
– CH2=CH2
2
4 (88%)
Equation 2 Synthesis of (Z)-2,2,5,5-tetraphenyl-1,6-dioxa-2,5-di-
silacyclooct-3-ene
The use of this catalytic system for silylative coupling cy-
clization of 1 and 2 gave exclusively a disilacyclic prod-
ucts containing Z-vinylene bond between silicon atoms
with perfect stereoselectivities and high yields (86–88%).
The Z-configuration in the endo-cyclic vinylene bond of
the cyclic products, (Z)-2,2,5,5-tetraphenyl-1,6-dioxa-
2,5-disilacyclooct-3-ene (3) and (Z)-1,6-dimethyl-
2,2,5,5-tetraphenyl-1,6-diaza-2,5-disilacyclooct-3-ene
To test the synthetic utility of cyclic silyl ether 3, we pur-
sued transformation of the obtained product into syntheti-
cally useful (Z)-1,2-bis(organyldiphenylsilyl)ethenes
(Equation 4). After preliminary attempts we found that
RuH(Cl)(CO)(PCy3)2
(1 mol%)
Ph
Ph
Me
Ph
Me
Si
O
Si
O
Si
Si
Si
O
O
Si
Me
Ph
Me
Ph
Me
Ph
Me
+
O
O
toluene, 110 °C, 24 h
5
6a,b
7a,b
6a,b/7a,b = 1:5
Equation 3 Silylative coupling cyclization of 1,2-bis(methylphenylvinylsiloxy)ethane
Synthesis 2006, No. 21, 3739–3745 © Thieme Stuttgart · New York

3742
P. Pawluć et al.
PAPER
treatment of 3 with 2.5 equivalents of the corresponding ed (Z)-1,2-bis(alkoxydiphenylsilyl)ethenes (Equation 5)
Grignard reagent in THF (0.5 M concentration of the sol- as expected.19 Using this procedure we have synthesized
vent) at 65 °C for 24 hours under argon atmosphere pro- two new organosilicon compounds: (Z)-1,2-bis(methoxy-
vided substituted (Z)-1,2-bis(silyl)ethenes in moderate to diphenylsilyl)ethene 12 (isolated yield, 79%) and (Z)-1,2-
good yields (Table 2).
bis(ethoxydiphenylsilyl)ethene (13) (isolated yield, 66%).
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
RMgX
Ph
Ph
Ph
Si
O
Si
O
Si
N
Si
N
ROH
Ph
Ph
Si
Si
Si
R
Si
R
Ph
Ph
Ph
THF, 65 °C
THF, 65 °C,
4 h
OR
OR
Me
Me
8–11
3
4
12 R = Me (79%)
13 R = Et (66%)
Equation 4 Synthesis of (Z)-1,2-bis(organyldiphenylsilyl)ethenes
Equation 5 Synthesis of (Z)-1,2-bis(alkoxydiphenylsilyl)ethenes
However, when ethylmagnesium bromide was used, the
reaction mixture had to be refluxed for a longer time and
an increased amount of the Grignard reagents (from 2.5–
3 equiv) did not appreciably affect the rate of this reaction.
When phenylmagnesium bromide (3 equiv) was added to
the cyclic silyl ether 3 under the same reaction conditions,
no reaction occurred and the starting material was recov-
ered unchanged. Table 2 summarizes the results of this re-
action.
In conclusion, we have described a novel stereoselective
and efficient protocol for the synthesis of (Z)-1,2-bis(or-
ganyldiphenylsilyl)ethenes from easily available starting
materials. Otherwise difficult to synthesize compounds of
the general formula (Z)-RPh2SiCH = CHSiPh2R, were ex-
clusively obtained by Z-selective silylative coupling cy-
clization of divinyl-substituted monomers catalyzed by
ruthenium hydride complex and subsequent treatment of
the resulting cyclic bis(silyl) derivatives with various
Grignard reagents or alcohols. Extension of the silylative
coupling procedure to Z-bis(silyl) derivatives makes this
particular method a universal and extremely useful route
for the regio- and stereoselective synthesis of isomeric
(Z)-1,2-, (E)-1,2- as well as 1,1-bis(silyl)ethenes.
Table 2 Synthesis of (Z)-1,2-Bis(organyldiphenylsilyl)ethenes
Compound R1
X
Time (h) Yield (%)a
8a
9
Me
I
24
48
24
24
72
78
63
90
78
Et
Br
Br
Br
Br
10
CH=CH2
CH2CH=CH2
Ph
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were recorded
on a Varian XL 300 spectrometer using CDCl3 or as a solvent. GC
analyses were performed on a Varian 3400 with a Megabore col-
umn (30 m) and TCD. Mass spectra of the products were deter-
mined by GC-MS analysis on a Varian Saturn 2100T, equipped
with a BD-5 capillary column (30 m) and a Finnigan Mat 800 ion
trap detector. All reactions were performed under an atmosphere of
deoxygenated and dried argon. Et3N, N,N¢-dimethylethane-1,2-di-
amine and pentane were dried over CaH2, distilled under argon and
stored over molecular sieves type 4A. THF and toluene were dried
over sodium and benzophenone and freshly distilled prior to use.
Ethylene glycol was dried (CaSO4) and distilled under argon. Grig-
nard reagents were synthesized via well-known procedures de-
scribed in the literature. [RuHCl(CO)(PCy3)2] was prepared by
adaptation of a procedure described in literature.15
11
–
0b
a Isolated yields of chromatographically pure products.
b Exclusively recovered starting material. Reaction conditions: THF,
65 °C.
In all of the reactions examined excellent stereoselectivity
was attained and no isomeric product could be detected.
All products were isolated and characterized spectroscop-
ically. Results of the spectroscopic analyses (1H, 13C
NMR, DEPT and HMQC) of the products obtained in the
above-mentioned reaction have confirmed the occurrence
of the Z-vinylene carbons between silicon atoms. The Z-
configuration of compound 8a was additionally con-
firmed by preparing the geometrically defined E-isomer
8b of 1,2-bis(methyldiphenylsilyl)ethene by another
route, i.e. [RuHCl(CO)(PCy3)2]-catalyzed selective sily-
lative homo-coupling of methyldiphenylvinylsilane7and a
comparison of their spectroscopic data.
Silylative Coupling Cyclization of 1 and 2 Using Different
Catalysts (Table 1)
In a typical catalytic test, a toluene solution of the ruthenium
hydride catalyst I, II or III was placed in a 5-mL glass mini-reactor.
Then the divinyl compound 1 or 2 and dodecane as internal standard
(5% by volume) were added (molar ratio: [Ru]/1 or 2 = 1:100). Af-
ter that, the reaction mixture was heated at 110 °C under the condi-
tions shown in Table 1. The composition of the reaction mixture
was analyzed by GC and identified by use of GC-MS. The progress
of the reactions was monitored by GC-MS. The selectivity and yield
of the reactions were calculated by using the internal standard meth-
od.
Inspired by the recently reported successful transforma-
tion of cyclic product containing SiN(Me)R functional-
ities into 1,1-bis(alkoxydimethylsilyl)ethenes,11b we en-
visioned compound 4 to be a good substrate candidate for
the synthesis of (Z)-1,2-bis(silyl)ethenes containing both
alkoxy and aryl substituents. We have found that the treat-
ment of the cyclic compound 4 with 2.5 equivalents of the
corresponding alcohol in THF at 65 °C for 4 hours, yield-
1,2-Bis(diphenylvinylsiloxy)ethane (1)
A solution of anhyd Et3N (23.5 mL, 0.169 mol) in pyridine (500
mL) was introduced into a flame-dried three-necked, 1-L round-bot-
tomed flask equipped with a magnetic stirring bar, rubber septum
cap and argon bubbling tube. To the resulting solution was added
Synthesis 2006, No. 21, 3739–3745 © Thieme Stuttgart · New York

PAPER
Stereoselective Approach toward (Z)-1,2-Bis(silyl)ethenes
3743
ethylene glycol (4.55 mL, 0.081 mol). Chlorodiphenylvinylsilane
(36.0 mL, 0.162 mol) was subsequently added and the mixture was
stirred under the flow of argon for 2 h at r.t. After the disappearance
of the substrate was confirmed by GC, the resulting salt was filtered
off and the volatiles were removed in an evaporator. Distillation un-
der reduced pressure afforded 29.03 g (80%) of compound 1; pale-
yellow oil; bp 140 °C/0.5 mmHg.
1H NMR, (CDCl3): d = 3.95 (s, 4 H, CH2O), 5.86–5.94 (dd, J = 4.0,
20.1 Hz, 2 H, CH2=CH), 6.23–6.29 (dd, J = 3.9, 14.8 Hz, 2 H,
CH2=CH), 6.42–6.53 (dd, J = 14.8, 20.1 Hz, 2 H, 2 × CH2=CH),
7.36–7.66 (m, 20 H, C6H5).
(Z)-1,6-Dimethyl-2,2,5,5-tetraphenyl-1,6-diaza-2,5-
disilacyclooct-3-ene (4)
Compound 2 (5.0 g, 0.014 mol) was added to a solution of [Ru-
HCl(CO)(PCy3)2] (0.102 g, 1.4 × 10–4 mol) and toluene (50 mL) in
a two-necked, 100-mL flask equipped with a magnetic stirring bar
and a reflux condenser. The mixture was heated under the flow of
argon for 24 h at 110 °C with stirring. The solvent was removed us-
ing an evaporator and the cyclic products were isolated by ‘bulb-to-
bulb’ distillation to give 4.15 g (88%) of 4; colorless oil; bp 145–
147 °C/0.5 mmHg).
1H NMR (CDCl3): d = 2.48 (s, 6 H, NCH3), 3.16 (s, 4 H, CH2), 7.13
(s, 2 H, CH=CH), 7.32–7.68 (m, 20 H, C6H5).
13C NMR (CDCl3): d = 36.1 (NCH3), 52.2 (CH2), 133.4, 134.9,
137.8 (C6H5), 150.1 (CH=CH).
13C NMR (CDCl3): d = 64,8 (CH2O), 127,7 (CH2=CH), 129,8
(CH2=CH), 133.3, 133.9, 134.9, 136.9 (C6H5).
MS (EI): m/z (%) = 451 (15), 401 (100), 357 (10), 329 (25), 279
(20), 210 (60), 183 (30), 105 (30), 77 (15), 51 (15).
Anal. Calcd for C30H32N2Si2: C, 75.58; H, 6.77; N, 5.88; Found: C,
75.88; H, 6.91; N, 5.73.
Anal. Calcd for C30H30O2Si2: C, 75.27; H, 6.32. Found: C, 75.58; H,
6.42.
1,2-Bis(methylphenylvinylsiloxy)ethane (5)
A solution of anhyd Et3N (9.42 mL, 0.068 mol) in anhyd pentane
(200 mL) was introduced into a flame-dried three-necked, 500-mL
round-bottomed flask equipped with a magnetic stirring bar, rubber
septum cap and argon bubbling tube. To the resulting solution was
added ethylene glycol (1.82 mL, 0.032 mol). Chloromethylphen-
ylvinylsilane (11.4 mL, 0.0624 mol) was subsequently added and
the mixture was stirred under the flow of argon for 2 h at r.t. After
the disappearance of the substrate was confirmed by GC, the result-
ing salt was filtered off and the volatiles were removed in evapora-
tor. Distillation under reduced pressure afforded 10.18 g (89%) of
compound 5; colorless oil; bp 120 °C/0.5 mmHg.
1H NMR (CDCl3): d = 0.48 (s, 6 H, CH3), 3.79 (s, 4 H, CH2O), 5.86–
5.94 (dd, J = 4.4, 19.7 Hz, 2 H, CH2=CH), 6.14–6.21 (dd, J = 4.4,
15.1 Hz, 2 H, CH2=CH), 6.26–6.38 (dd, J = 15.1, 19.7 Hz, 2 H,
CH2=CH), 7.36–7.65 (m, 20 H, C6H5).
13C NMR (CDCl3): d = –3.28 (CH3), 64.4 (CH2O), 127,7
(CH2=CH), 129.6 (CH2=CH), 133.9, 134.9, 135.3, 135.9 (C6H5).
N,N¢-Dimethyl-N,N¢-di(diphenylvinylsilyl)ethane-1,2-diamine
(2)
A solution of anhyd Et3N (16.6 mL, 0.19 mol) in anhyd pentane
(200 mL) was introduced into a flame-dried three-necked, 500-mL
round-bottomed flask equipped with a magnetic stirring bar, rubber
septum cap and argon bubbling tube. To the resulting solution was
added N,N¢-dimethylethane-1,2-diamine (6.0 mL, 0.057 mol).
Chlorodiphenylvinylsilane (25.2 mL, 0.113 mol) was subsequently
added and the mixture was stirred under the flow of argon for 4 h at
40 °C. After the disappearance of the substrate was confirmed by
GC, the resulting salt was filtered off under argon and the volatiles
were removed in evaporator. Distillation under reduced pressure af-
forded 22.32 g (78%) of compound 2; colorless oil; bp 145–147 °C/
0.5 mmHg.
1H NMR (300 MHz, CDCl3): d = 2.46 (s, 6 H, NCH3), 3.05 (s, 4 H,
CH2), 5.86–5.94 (dd, J = 3.8, 20.2 Hz, 2 H, CH=CH2), 6.03–6.07
(dd, J = 3.8, 13.6 Hz, 2 H, CH=CH2), 6.41–6.48 (dd, J = 13.6, 20.3
Hz, 2 H CH=CH2), 7.15–7.23 (m, 4 H, C6H5), 7.63–7.75 (m, 16 H,
C6H5).
MS (EI): m/z (%) = 451 (15), 401 (100), 357 (10), 329 (25), 279
(20), 210 (60), 183 (30), 105 (30), 77 (15), 51 (15).
13C NMR (75 MHz, CDCl3): d = 35.9 (NCH3), 50.2 (CH2), 127.6
(CH=CH2), 129.3 (CH=CH2), 134.4, 135.4, 135.6, 136.2 (C6H5).
Anal. Calcd for C20H26O2Si2: C, 67.74; H, 7.39. Found: C, 67.89; H,
7.42
MS (EI): m/z (%) = 478 (10), 406 (30), 356 (70), 329 (70), 303 (30),
252 (100), 226 (30), 181 (45), 105 (45), 78 (50).
Compounds 6 and 7 (Mixture of Four Isomers)
Compound 5 (5.0 g, 0.014 mol) of was added to a solution of [Ru-
HCl(CO)(PCy3)2] (0.102 g, 1.4 × 10–4 mol) and toluene (50 mL) in
a two-necked, 100-mL flask equipped with a magnetic stirring bar
and a reflux condenser. The mixture was heated under the flow of
argon for 24 h at 110 °C with stirring. The solvent was removed in
evaporator and the cyclic products were isolated by ‘bulb-to-bulb’
distillation to give 4.23 g (92%) of a mixture of compounds 6a, 6b,
7a, 7b; colorless oil; bp 112–115 °C/0.5 mmHg.
1H NMR (CDCl3): d = 0.50, 0.51, 0.56, 0.57 (s, CH3), 3.73, 3.84,
3.87, 3.88 (s, CH2O), 6.42 (s, CH=CH), 6.46 (s, CH=CH), 7.05 (s,
C=CH2), 7.32–7.68 (m, 20 H, C6H5).
13C NMR (CDCl3): d = –2.2, –2.1, –1.4, –1.3 (CH3), 65.4, 66.8
(CH2O), 127.7, 127.8, 129.6, 129.7, 133.9, 134.2 (C6H5), 144.7,
144.8 (C=CH2), 150.4 (C=CH2), 152.0 (CH=CH)
MS (EI): m/z (%) = 326 (M+, 10), 311 (60), 283 (50), 267 (60), 249
(100), 195 (70), 179 (30), 165 (35), 145 (50), 119 (45), 105 (95), 91
(45), 77 (40).
Anal. Calcd for C32H36N2Si2: C, 76.14; H, 7.19; N, 5.55. Found: C,
76.22; H, 7.31, N, 5.78.
(Z)-2,2,5,5-Tetraphenyl-1,6-dioxa-2,5-disilacyclooct-3-ene (3)
[RuHCl(CO)(PCy3)2] (152 mg, 2.1 × 10–4 mol) and compound 1
(10.0 g, 0.021 mol) were placed in a glass ampoule, which was
sealed under argon and heated for 36 h at 110 °C. After the disap-
pearance of the substrate was confirmed by GC, the cyclic product
was isolated by recrystallization from hexane to give 8.09 g (86%)
of 3; colorless solid; bp 145–147 °C/0.5 mmHg.
1H NMR (CDCl3): d = 3,88 (s, 4 H, CH2O), 7,36 (s, 2 H, CH=CH),
7,34–7,64 (m, 20 H, C6H5).
13C NMR (CDCl3): d = 65.5 (CH2O), 127.7, 129.8, 134.7, 134.9
(C6H5), 149.6 (CH=CH).
MS (EI): m/z (%) = 373 (100), 330 (30), 251 (10), 182 (10), 105
(10), 77 (15), 51 (15).
Anal. Calcd for C28H26O2Si2: C, 74.62; H, 5.81. Found C, 74.68; H,
5.96.
Anal. Calcd for C18H22O2Si2: C, 66.21; H, 6.79. Found: C, 66.41; H,
6.89.
Synthesis 2006, No. 21, 3739–3745 © Thieme Stuttgart · New York

3744
P. Pawluć et al.
PAPER
(Z)-1,2-Bis(organyldiphenylsilyl)ethenes; General Procedure
A glass reactor (50-mL, two-necked, round-bottomed flask
equipped with a magnetic stirring bar, reflux condenser, argon bub-
bling tube and thermostated heating oil bath) was evacuated and
flushed with argon. (Z)-2,2,5,5-Tetraphenyl-1,6-dioxa-2,5-disilacy-
clooct-3-ene (3; 2.5 g, 5.5 mmol) and THF (10 mL) were added to
the reactor. Grignard reagent (molar ratio of the compound 3 to
Grignard reagent was 1: 2.5) was added dropwise at r.t. The mixture
was stirred under the conditions shown in Table 2. After the disap-
pearance of the substrate was confirmed by GC, the solvent was re-
moved in an evaporator, pentane (20 mL) was added and the
resulting salt was filtered off. After evaporation the crude product
was distilled under reduced pressure to afford the analytically pure
product.
13C NMR (CDCl3): d = 21.6 (CH2), 114.4 (CH=CH2), 127.6, 127.8,
129.3, 129.5 (C6H5), 133.9 (CH=CH2), 135.3, 135.5 (C6H5), 150.3
(CH=CH).
MS (EI): m/z (%) = 472 (M+, 5), 431 (100), 390 (95), 354 (75), 328
(20), 260 (75), 224 (20), 181 (30), 145 (20), 105 (40), 79 (10), 53
(15).
Anal. Calcd for C32H32Si2: C, 81.30; H, 6.82. Found: C, 81.48; H,
6.56.
(E)-1,2-Bis(methyldiphenylsilyl)ethene (8b)
1H NMR (300 MHz, CDCl3): d = 0.65 (s, 6 H, CH3), 7.07 (s, 2 H,
CH=CH), 7.26–7.53 (m, 20 H, C6H5).
13C NMR (75 MHz, CDCl3): d = –3.9 (CH3), 127.7, 129.2, 134.7,
136.1 (C6H5), 150.3 (CH=CH).
(Z)-1,2-Bis(methyldiphenylsilyl)ethene (8a)
Yield: 1.46 g (78%); colorless oil; bp 122 °C/0.5 mmHg.
1H NMR (300 MHz, CDCl3): d = 0.13 (s, 6 H, CH3), 7.32 (s, 2 H,
CH=CH), 7.29–7.49 (m, 20 H, C6H5).
13C NMR (75 MHz, CDCl3): d = 1.2 (CH3), 129.0, 134.3, 134.7,
137.2 (C6H5), 149.1 (CH=CH).
MS (EI): m/z (%) = 405 (15), 327 (25), 264 (70), 223 (25), 197
(100), 145 (30), 105 (20), 53 (10).
Anal. Calcd for C28H28Si2: C, 79.94; H, 6.71. Found: C, 79.78; H,
6.92.
(Z)-1,2-Bis(alkoxydiphenylsilyl)ethenes; General Procedure
A glass reactor (50-mL, two-necked, round-bottomed flask
equipped with a magnetic stirring bar, reflux condenser and argon
bubbling tube) was evacuated and flushed with argon. (Z)-1,6-Di-
methyl-2,2,5,5-tetraphenyl-1,6-diaza-2,5-disilacyclooct-3-ene (4;
2.62 g, 5.5 mmol) and THF (10 mL) were added to the reactor. At
r.t., the corresponding alcohol (molar ratio of the compound 4 to al-
cohol was 1:2.5) was added dropwise. The mixture was stirred at
65 °C for 4 h. After the reaction was complete, the excess of the al-
cohol and the solvent were evaporated in vacuo. After evaporation,
the crude product was distilled under reduced pressure to afford the
analytically pure product.
MS (EI): m/z (%) = 405 (20), 327 (25), 265 (75), 223 (25), 197
(100), 145 (30), 105 (30).
Anal. Calcd for C28H28Si2: C, 79.94; H, 6.71. Found: C, 79.68; H,
6.54.
(Z)-1,2-Bis(ethyldiphenylsilyl)ethene (9)
Yield: 1.26 g (63%); colorless oil; bp 128 °C/0.5 mmHg.
1H NMR (300 MHz, CDCl3): d = 0.83–0.88 (q, J = 7.7 Hz, 4 H,
CH2), 1.48–1.53 (t, J = 7.9 Hz, 6 H, CH3), 7.38 (s, 2 H, CH=CH),
7.30–7.52 (m, 20 H, C6H5).
13C NMR (75 MHz, CDCl3): d = 7.4 (CH2), 8.7 (CH3), 129.4, 129.6,
(Z)-1,2-Bis(methoxydiphenylsilyl)ethene (12)
Yield: 1.50 g (79%); colorless oil; bp 144 °C/0.5 mmHg.
1H NMR (300 MHz, CDCl3): d = 3.68 (s, 6 H, OCH3), 7.06 (s, 2 H,
CH=CH), 7.32–7.68 (m, 20 H, C6H5).
13C NMR (75 MHz, CDCl3): d = 58.2 (OCH3), 134.1, 134.9, 134.9,
137.8 (C6H5), 149.8 (CH=CH).
134.4, 136.2 (C6H5), 150.2 (CH=CH).
MS (EI): m/z (%) = 420 (100), 372 (10), 342 (20), 314 (15), 260
(20), 184 (45), 105 (40).
Anal. Calcd for C30H32Si2: C, 80.30; H, 7.19. Found: C, 80.62; H,
7.23.
(Z)-1,2-Bis(diphenylvinylsilyl)ethene (10)
Yield: 1.78 g (90%); colorless oil; bp 124 °C/0.5 mmHg.
MS (EI): m/z (%) = 376 (5), 345 (70), 299 (100), 228 (30), 181 (50),
105 (45), 78 (10).
1H NMR (300 MHz, CDCl3): d = 5.51–5.58 (dd, J = 4.4, 19.5 Hz, 2
H, CH2=CH), 5.94–6.00 (dd, J = 4.4, 14.6 Hz, 2 H, CH2=CH),
6.04–6.15 (dd, J = 19.5, 14.7 Hz, 2 H, CH2=CH), 7.28–7.60 (m, 20
H, C6H5), 7.56 (s, 2 H, CH=CH).
Anal. Calcd for C28H28O2Si2: C, 74.29; H, 6.23. Found: C, 74.47; H,
6.42.
(Z)-1,2-Bis(ethoxydiphenylsilyl)ethene (13)
Yield: 1.74 g (66%); colorless oil; bp 155 °C/0.5 mmHg.
13C NMR (75 MHz, CDCl3): d = 129.3, 129.4 (C6H5), 134.3
(CH=CH2), 135.5, 135.8 (C6H5), 136.5 (CH=CH2), 150.1
(CH=CH).
1H NMR (300 MHz, CDCl3): d = 1.24–1.28 (t, J = 6.8 Hz, 6 H,
CH2CH3), 3.78–3.82 (q, J = 6.9 Hz, 4 H, CH2CH3), 7.02 (s, 2 H,
CH=CH), 7.22–7.56 (m, 20 H, C6H5).
13C NMR (75 MHz, CDCl3): d = 20.2 (CH2CH3), 58.9 (CH2CH3)
133.8, 134.3, 134.9, 137.6 (C6H5), 150.1 (CH=CH).
MS (EI): m/z (%) = 417 (5), 367 (20), 340 (25), 312 (20), 259 (35),
209 (60), 183 (85), 155 (20), 131 (30), 105 (100), 77 (20), 53 (50).
Anal. Calcd for C30H28Si2: C, 81.02; H, 6.35. Found: C, 80.78; H,
6.55.
Anal. Calcd for C30H32O2Si2: C, 74.95; H, 6.71. Found: C, 75.12; H,
6.98.
(Z)-1,2-Bis(allyldiphenylsilyl)ethene (11)
Yield: 1.64 g (78%); colorless oil; bp 133 °C/0.5 mmHg.
Acknowledgment
1H NMR (CDCl3): d = 1.68–1.70 (d, J = 5.4 Hz, 4 H, CH2), 4.74–
4.82 (m, 2 H, CH=CH2), 4.86–4.95 (m, 2 H, CH=CH2), 5.53–5.64
(m, 2 H, CH=CH2), 7.32 (s, 2 H, CH=CH), 7.27–7.51 (m, 20 H,
C6H5).
Financial support from the Ministry of Science and Higher Educa-
tion (Poland), Grants 3T09A 145 26 and PBZ-KBN 118/T09/17, is
gratefully acknowledged.
Synthesis 2006, No. 21, 3739–3745 © Thieme Stuttgart · New York

PAPER
Stereoselective Approach toward (Z)-1,2-Bis(silyl)ethenes
3745
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Pawluc, P. Tetrahedron Lett. 2000, 41, 10303.
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Synthesis 2006, No. 21, 3739–3745 © Thieme Stuttgart · New York