Transformations of diallylsilanes under the action of electrophilic reagents

Article abstract of DOI:10.1016/j.jorganchem.2008.11.017

Reactions of dimethyl-, diphenyl-, and (chloromethyl)methyldiallylsilanes with acetic, trifluoroacetic, triflic acids and complex BF₃ · 2AcO{cyrillic}H are studied. Depending on the structure of the starting diallylsilane and the nature of the

Full text of DOI:10.1016/j.jorganchem.2008.11.017

Journal of Organometallic Chemistry 694 (2009) 420–426
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Transformations of diallylsilanes under the action of electrophilic reagents
*
Elena N. Suslova, Alexandr I. Albanov, Bagrat A. Shainyan
A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Division of Russian Academy of Sciences, 1 Favorsky Street, 664033 Irkutsk, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 August 2008
Received in revised form 26 September 2008
Accepted 7 November 2008
Available online 14 November 2008
Reactions of dimethyl-, diphenyl-, and (chloromethyl)methyldiallylsilanes with acetic, trifluoroacetic, tri-
flic acids and complex BF3 ꢀ 2AcOH are studied. Depending on the structure of the starting diallylsilane
and the nature of the electrophilic reagent the following processes are realized: addition of an electro-
phile to one C@C bond; expulsion of one or two molecules of propene with addition of the electrophile
residue to the silicon atom; and rearrangement with elimination of one allyl group from silicon and its
attachment to the second allyl group of diallylsilane. Quantum chemical calculations of all three types
of transformations are performed on the example of the reactions of dimethyl- and bis(chloro-
methyl)diallylsilanes with HF, CF3COOH, CF3SO3H, as well as of the intermediate carbenium and siliceni-
um cations.
Keywords:
Diallylsilanes
Addition
Elimination
Rearrangement
Protodesilylation
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
ments similar to that described in [1] are also known. They proceed
either for diallylsilanes as in the reaction of R2Si(CH2CH@CH2)2
Recently we have shown that the reaction of diallyl(diphenyl)-
silane (1) with complex BF3 ꢀ 2AcOH gives the product of rear-
rangement, fluoro(2-methyl-4-pentenyl)diphenylsilane [1]. It was
of interest to analyze the dependence of the reaction course on
the structure of the silane and electrophilic reagent as well as on
the reaction conditions. A priori, based on the literature data, one
could assume three routes, namely, (i) addition of the acid to allyl
group, (ii) elimination of one or two molecules of propene, and (iii)
rearrangement with rupture of the Si–CH2CH@CH2 bond followed
by addition of the eliminated allyl group to the second allyl group
of diallylsilane.
with
a
,b-unsaturated ketones and BF3 ꢀ OEt2 occurring at room
temperature and resulting in R2Si(F)CH2CH(Me)CH2CH@CH2 as
by-products [11] or during thermolysis of silanes R2Si(CH2CH@CH2)-
(CH2CHClCH3), apparently, initiated by dehydrochlorination and
eventually giving rise to the products of elimination R2Si(Cl)-
(CH2CH@CH2) and rearrangement R2Si(F)CH2CH(Me)CH2CH@CH2
[12].
In spite of abundance of the literature dealing with each type of
these reactions, the number of works concerning diallylsilanes is
rather limited, although the presence of two allyl groups provides
a possibility for new transformations, like the aforementioned
rearrangement with both allyl groups being involved. We also
failed to find studies reporting the effect of the structure of the
silane and electrophilic reagent on the reaction course and the
reasons directing the reaction in favor of this or that mechanism.
In order to fill in this gap we have undertaken this study and
examined the behaviour of diallyl(diphenyl)silane (1), diallyl(di-
methyl)silane (2) and diallyl(chloromethyl)methylsilane (3) under
the action of different electrophiles – acetic, trifluoroacetic and
triflic acids, and complex BF3 ꢀ 2AcOH. All reactions were carried
out in boiling methylene chloride or upon cooling to ꢁ20 °C. It
turned out that depending on the structure of the reagents all
the aformentioned reaction routes are realized.
All three types of the reactions are known in the literature.
Electrophilic addition to allyl group in allylsilanes was thoroughly
studied [2–4]; they obey the Markovnikov rule due to stabilization
of the initially formed carbocation by the
r
(CH2–Si) ? p(C+)
electrondonating effect [5]. Elimination of the allyl group under
acidic conditions (protodesilylation reactions) was also actively
studied (see, e.g., a comprehensive review [6]); owing to these
reactions allylsilanes became effective synthons for preparation
of various organic compounds [6–9]. Special mentioning deserves
elimination of one allyl group from mono- and diallylsilanes
MenAll3ꢁnSiCH2Cl (n = 0–2) under the action of Lewis acids (FeCl3,
AlCl3) occurring under mild conditions (25–40 °C) to afford
MenAll2ꢁnSi(Cl)CH2Cl [10]. No further elimination was detected,
as the authors believe, due to mild conditions used. Rearrange-
2. Results and discussion
We have found that diallyl(diphenyl)silane (1) does not react
with acetic acid but with trifluoroacetic acid it forms the adduct
to one allyl group 4 in 70% yield. With more strong triflic acid
* Corresponding author. Tel.: +7 3952 51 1425; fax: +7 3952 419346.
E-mail address: bagrat@irioch.irk.ru (B.A. Shainyan).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.017

E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
421
the reaction proceeds similar to that with complex BF3 ꢀ 2AcOH1 to
afford the rearrangement products 5 and 6 in 80% and 63% yield,
respectively (Scheme 1).
20 ppm with J 291 Hz, that completely coincided with that in the
independently synthesized allyl(chloromethyl)fluoro(methyl)-
silane 12. Therefore, the reaction proceeds by 86% as rearrange-
ment and by 14% as elimination. With the most strong
electrophile, triflic acid, at room temperature the products of rear-
rangement 13 and elimination of one molecule of propene 14 are
formed in the ratio of 1:1. When the reaction is carried out at
ꢁ20 °C this ratio changes to 1:1.5 in favor of the elimination prod-
uct 14 (Scheme 3).
It is known from the literature that the reaction of diallyl(di-
methyl)silane (2) with triflic acid at ꢁ40 °C gives rise to the product
of elimination of one molecule of propene Me2Si(CH2CH@CH2)-
OSO2CF3 (7) [13]. At room temperature the reaction occurs similarly
except for 25% of the bis-triflate Me2Si(OSO2CF3)2 is formed as a by-
product due to elimination of two molecules of propene [13]. We
have found that silane 2 does not react with acetic acid at room
temperature, whereas with trifluoroacetic acid it gives the product
of elimination 8 in 51% yield. With more strong electrophile, com-
plex BF3 ꢀ 2AcOH, difluoro(dimethyl)silane (9) is formed as a result
of elimination of two molecules of propene. Both products
[difluoro(dimethyl)silane and propene] are gaseous, so, they were
trapped by bubbling the evolved gases into CCl4 in a cooled trap.
Formation of difluoro(dimethyl)silane is unequivocally proved by
The structure of all products was confirmed by 1H, 13C, 19F, 29Si
NMR spectroscopy. The presence of a chiral carbon atom in mole-
cules 4, 5, 6 causes diastereotopism of the methylene protons, and
in the proton spectra of compounds 10, 11, 13 due to the presence
of two chiral centers (silicon and carbon atoms) the multiplet sig-
nals of two diastereomers (R,S) and (R,R) presenting in a close to
1:1 ratio are superimposed so that it does not allow to determine
the fine structure of the multiplets.
Table 1 summarizes the results of investigation of the reactions
of diallylsilanes with different electrophilic reagents. As follows
from these data, the course of the reaction and the ratio of the
products formed depend both on the strength of the acid and the
structure of the original diallylsilane.
3
the presence of a septet with JHF 6.1 Hz and a doublet of septets
on the 29Si satellite signals with 1JHF 290.7 Hz in the 19F NMR spec-
trum. The formation of propene is proved by the presence in the 1H
NMR spectrum a doublet of the methyl group, two doublets of the
@CH2 group with characteristic coupling constants Jcis and Jtrans
,
and a multiplet of CH@ proton, in the ratio of 3:1:1:1, as well as
the corresponding signals in the 13C NMR spectrum. Therefore,
combining our and the Uhlig’s [13] results, the following scheme
can be written for silane 2 (Scheme 2).
Dependence of the ease of the reaction of allylsilanes with acids
on the acid strength is well known in the literature. Thus, isomeric
allylsilanes Me3SiCH2CH@CHSiMe2Ph and PhMe2SiCH2CH@CH-
SiMe3 do not suffer any changes in acetic acid after 5 days at room
temperature but react with more strong halogenoacetic acids, the
time of the reaction being drastically decreased with the strength
of the acid: from 10.5 h for ClCH2COOH to <1 min for CF3COOH
[14]. That means that the first step of the reaction is protonation
of the substrate. Possible routes for the formation of the products
of addition, elimination and rearrangement for diallylsilanes are
shown in Scheme 4. Depending on the stability of the silicenium
cations, the process may be either stepwise or concerted (vide
infra).
No formation of other products for the reactions of silanes 1 and
2
with electrophiles when carrying out at low temperature
(ꢁ20 °C) or upon large dilution and slow addition of the reagents
was detected.
Diallyl(chloromethyl)methylsilane (3) does not react with
acetic acid, either. Trifluoroacetic acid in methylene chloride adds
to one allyl group giving rise to the adduct 10 in good yield. In
the reaction of silane 3 with complex BF3 ꢀ 2AcOH, similar to silane
1, the only isolated product was the product of rearrangement 11.
However, the 29Si NMR spectrum of the crude product, apart from
the two close doublets at 24 ppm corresponding to two diastereo-
mers of compound 11, contained another doublet (ꢂ14%) at
Such a weak acid as acetic acid cannot protonate the double
bond, therefore, no reaction occurs with none of the investigated
substrates in this medium. No reaction is observed also for silane
Me
Ph
Ph
CH2CHCH2CH=CH2
CF3SO3H
Si
OSO2CF3
Ph
Ph
CH2CH=CH2
Ph
Ph
CH2CH=CH2
CF3COOH
5
Si
Si
CH2CHCH3
OCOCF3
CH2CH=CH2
Ph
CH2CHCH2CH=CH2
BF3 2AcOH
Si
1
Me
F
Ph
4
6
Scheme 1.
Me
Me
CH2CH=CH2
CF3SO3H
Si
[13]
-MeCH=CH2
OSO2CF3
Me
Me
CH2CH=CH2
OC(O)CF3
Me
CH2CH=CH2
CF3COOH
Si
7
Si
-MeCH=CH2
Me
CH2CH=CH2
Me
Me
F
BF3 2AcOH
8
Si
2
-2MeCH=CH2
F
9
Scheme 2.

422
E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
Table 1
Routes of the reactions of diallylsilanes R0R00Si(CH2CH@CH2)2 with electrophiles.
HX
R0, R00
AcOH
CF3COOH
BF3 ꢀ 2AcOH
CF3SO3H
Ph, Ph
Me, Me
Me, ClCH2
No reaction
No reaction
No reaction
Addition
Elimination
Addition
Rearrangement
Rearrangement
Double eliminationa
Rearrangement + elimination
Elimination [13]b
Elimination + rearrangement
a
At 25–40 °C.
At ꢁ40 °C.
b
3 with trifluoroacetic acid in methanol, unlike the reaction in
methylene chloride (vide supra). Different behaviour of dial-
lyl(chloromethyl)methylsilane (3) with respect to trifluoroacetic
acid in methanol and methylene chloride is in good compliance
with the determining role of protonation as the first step of the
process. The protonating ability of trifluoroacetic acid in methanol
is lower than in methylene chloride due to strong specific solvation
of the carboxylic group, that accounts for the absence of any
transformations in methanol.
More complicated is the situation with the competition be-
tween the processes of rearrangement and elimination. According
to Scheme 2, it is determined by the interaction of the carbocation
center with orbitals
p(C@C) and r(CH2–Si), routes a and b in
Scheme 3, respectively. Therefore, it could be anticipated that elec-
trondonating substituents at the silicon atom will, first of all, favor
the elimination reaction due to the enhanced
r
(CH2–Si) ? p(C+)
interaction. Comparison of the results presented in Table 1 for dial-
lylsilanes 2 and 3 confirms this conclusion.
Formation of adducts is observed only in the reaction with tri-
fluoroacetic acid that apparently is due to higher nucleophilicity
of the anion CF3COOꢁ as compared to that of the triflate anion
The competition between the two processes could also have
been affected by steric effects of the group R. However, the steric
effects of R should be similar, if not to say identical, for the two
silicenium cations depicted in Scheme 4, diorganyl(2-methyl-4-
pentenyl)silicenium cation and diorganyl(allyl)silicenium cation,
since the surrounding of the silicon atom is nearly the same. This
CF3SOꢁ. As to complex BF3 ꢀ 2AcOH, there are no data on the nucle-
3
ophilicity of the conjugated anion but it evidently should be low
due to interactions of the HBF2(OAc)–Fꢀ ꢀ ꢀH–OAc type.
Me
CH2CHCH2CH=CH2
Si
Me
F
ClCH2
Me
CH2CH=CH2
Me
CH2CH=CH2
CH2CH=CH2
CF3COOH
BF3 2AcOH
11
Si
Si
ClCH2
CH2CHCH3
OCOCF3
ClCH2
Me
CH2CH=CH2
Si
3
10
ClCH2
F
CF3SO3H
12
Me
Me
CH2CH=CH2
Me
CH2CHCH2CH=CH2
Si
Si
ClCH2
OSO2CF3
ClCH2
OSO2CF3
14
13
Scheme 3.
R
R
CH2CH=CH2
Si
Si
CH2CH=CH2
H+
b
Me
R
Si
R
R
R
R
CH2 CH CH3
a
b
CH2CHCH2CH=CH2
X-
CH2CH=CH2
X-
Si
Si
a
CH3CH=CH2
a
R
CH2 CH CH2
X-
c
R
R
R
R
CH2CH=CH2
CH2CHCH2CH=CH2
X
Si
Me
X
R
R
CH2 CH CH3
X
Si
rearrangement
elimination
CH2 CH CH2
addition
Scheme 4.

E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
423
Table 2
Thermal effects (DE, kcal/mol) for reactions of diallylsilanes R2Si(CH2CH@CH2)2 with electrophiles HX.
No.
Reaction
R
X
ꢁ
DE
1
2
3
4
5
6
7
8
Me
CF3COO
CF3SO2O
F
CF3COO
CF3SO2O
F
CF3COO
CF3SO2O
F
CF3COO
CF3SO2O
F
CF3COO
CF3SO2O
F
CF3COO
CF3SO2O
F
13.0
14.7
15.1
12.9
13.8
13.3
28.1
32.2
37.7
22.9
26.6
29.2
43.0
46.0
52.3
38.3
42.0
47.6
ꢁ17.3
ꢁ25.0
R2SiAll2 þ HX ! R2SiðAllÞCH2CHðXÞCH3
ClCH2
Me
R2SiAll2 þ HX ! R2SiðXÞCH2CH@CH2 þ CH3CH@CH2
R2SiAll2 þ HX ! R2SiðXÞCH2CHðCH3ÞCH2CH@CH2
9
10
11
12
13
14
15
16
17
18
19
20
ClCH2
Me
ClCH2
R
R
CH2CH=CH2
CH2CHCH3
R2SiCH2CH=CH2 CH3CH=CH2
Me
ClCH2
Si
is true also for the two final products for the rearrangement and
elimination processes. Therefore, it is the electronic effects that
are responsible for the result of the competition between the rear-
rangement and elimination. Lowering the stability of the siliceni-
um cations leading, in the limit, to a concerted transformation of
the carbocation into the final products by routes a and b does
not change this conclusion.
To get a better insight into the understanding of the depen-
dence of the course of the reaction on the structure of the reagents
we have performed quantum chemical calculations of the reagents,
products, and intermediate carbenium and silicenium cations.
Thermal effects of the reactions of addition, elimination and rear-
rangement were calculated for dimethyl- and bis(chloro-
methyl)diallylsilane simulating the behaviour of substrates with
electrondonating and electronwithdrawing substituents at the
by 10–20 kcal/mol. Such an order is clear enough since the prod-
ucts of rearrangement and elimination have the Si–X bond
(X = O, F) which is much stronger than the Si–C bond in the prod-
ucts of addition, especially for X = F. A larger exothermicity of rear-
rangement as compared to elimination is explained by the fact that
formally the product of rearrangement is formed by addition of
propene to the product of elimination, that is, by rupture of one
C@C bond and formation of two C–C bonds.
Calculation of the initially formed carbenium cations
[R2Si(All)CH2CHCH3]+ (R = Me, ClCH2) suggests the presence of very
strong interaction of the
r
(CH2–Si) ? p(C+) type, leading to elon-
gation of the Si–C bond and transfer of the electron density to
the formed molecule of propene. As a result, their structure virtu-
ally corresponds to a silicenium cation interacting with the mole-
cule of propene:
silicon atom. HF, CF3COOH, and CF3SO3H were chosen as electro-
philes. Besides, the reactions of conversion of the initially formed
carbenium cation to the silicenium cation as a result of elimination
of the molecule of propene from dimethyl- and bis(chloro-
methyl)allylsilyl propenylium cations have also been calculated.
The results are represented in Table 2.
That means that the transition state for the reaction of elimination
of propene (reactions (19) and (20) in Table 2) is late, that is, close
in structure to the product of the reaction, silicenium cation.
With this, for the dimethylsubstituted cation it is more late than
in the bis(chloromethyl)substituted cation, and hyperconjugation
r
(CH2–Si) ? p(C+) for R = Me is notably stronger, as witnessed by
Obviously, being obtained without taking into account solvent
effects and entropy factors, these data can be considered as giving
only an estimation of the relative preferability of different reaction
routes for different substrates and electrophiles. As follows from
Table 2, all three processes are exothermic, the rearrangement
being the most and the addition the least thermodynamically
favorable. Elimination is less exothermic as compared to rear-
rangement by ꢂ15 kcal/mol, but more exothermic than addition
much larger Si–C distance (2.166 Å and 2.074 Å), a larger charge
on the silicon atom (+1.012 and +0.956), and more developed dou-
ble bond in the eliminated fragment (lC@C 1.376 Å and 1.388 Å,
\HCCH 169.3° and 160.2°). All this is indicative of the predomi-
nance of elimination for R = Me.
For appraisal of the relative probability of the elimination and
addition reactions from the data of Table 2, the values DDE =
D
Eelim
ꢁ
DEadd for R = Me and ClCH2 should be compared. For all

424
E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
electrophiles the values of |DDE| for R = Me are by 5–7 kcal/mol
larger than for R = ClCH2, that is, the relative probability of elimina-
tion is higher for R = Me. Therefore, the analysis of both the struc-
ture of the intermediate carbenium cations and the thermal effects
of the corresponding reactions testifies to preferability of elimina-
tion for diallylsilanes with electrondonating substituents at the sil-
icon atom, in compliance with the experimental observations
(Table 1). The largest DDE value is observed for the reaction with
HF and, indeed, in the reaction of diallyl(dimethyl)silane (2) with
complex BF3 ꢀ 2AcOH double elimination occurs, that is, two mole-
cules of propene are expelled and difluoro(dimethyl)silane (9) is
formed (Table 1).
trometer for CDCl3 solutions at working frequencies 400.13 (1H),
100.62 (13C), 376.50 (19F) and 79.50 (29Si) MHz; 1H, 13C and 29Si
NMR chemical shifts are reported in parts per million downfield
to TMS, and 19F NMR in parts per million downfield to CFCl3.
4.4. Reactions of diallylsilanes with electrophiles
4.4.1. 2-[Allyl(diphenyl)silyl]-1-methylethyl trifluoroacetate (4)
To diallyl(diphenyl)silane (1) (1.45 g, 5.49 mmol) in absolute
CH2Cl2 (5 mL) the solution of trifluoroacetic acid (0.63 g,
5.49 mmol) in CH2Cl2 (5 mL) was added dropwise at room temper-
ature in the course of 15 min. The reaction mixture was refluxed
for 4 h, washed with cold water (3 ꢃ 25 mL), dried over CaCl2. After
removal of solvent the title compound 4 (1.45 g, 70%) was obtained.
Analytically pure sample was isolated by flash chromatography
(hexane/ether 80:1–8:1, Rf 0.61) as a colorless oil. Anal. Calc. for
C20H21F3SiO2: C, 63.48; H, 5.59; F, 15.06; Si, 7.41. Found: C,
Now let us compare the values of DDE0 =
D
Erearr
ꢁ
DEelim for
R = Me and ClCH2. Following the same logic, they may be used
for appraisal of the relative probability of the elimination and
rearrangement reactions. First, the |DDE0| values for R = ClCH2 are
larger than for R = Me, that is, the relative probability of rearrange-
ment for R = ClCH2 is higher. Indeed, in the reaction of silane 3 with
complex BF3 ꢀ 2AcOH the rearrangement is the main process
whereas with silane 2 only the product of elimination is observed.
In the reaction with CF3SO3H, silane 2 gives only elimination prod-
uct whereas silane 3 gives rise to both products (Table 1). Second,
the DDE0 value for silane 3 is by 3.0 kcal/mol larger for HF than for
CF3SO3H, which is also in agreement with the experimental
observation of lower percentage of elimination in the reaction with
complex BF3 ꢀ 2AcOH than with CF3SO3H (14% and 50–60%, respec-
63.54; H, 5.98; F, 15.28; Si, 6.96%. mmax(liquid film): 3080, 2995,
1785, 1620, 1600, 1420, 1390, 1160, 1110, 790, 695 cmꢁ1; dH
7.54–7.42 (10H, m, Ph); 5.80 (1H, m, CH@); 5.25 (1H, m, CMe);
4.98 (1H, d, J 15.8 Hz, CH2@); 4.95 (1H, d, J 9.3 Hz, CH2@); 2.20
(2H, d, J 8.0 Hz, CH2C@); 1.85 (1H, dd, J 14.7, 8.31 Hz, SiCHaHbC);
1.62 (1H, dd, J 14.7, 6.0 Hz, SiCHaHbC); 1.28 (3H, d, J 6.0 Hz,
CH3C); dC 156.76 (q, J 41.5 Hz, C@O); 128.22, 129.96, 133.99,
134.98 (Ph); 115.44 (CH2@); 114.77 (q, J 286 Hz, CF3); 75.70
(CH); 22.56 (Me); 21.06, 20.80 (SiCH2); dF ꢁ75.28; dSi 12.01.
tively). Third, the DDE0 values are substantially smaller than DD
E
0
(ꢁDD
E
= 0.5, 1.6 and 3.8 kcal/mol for CF3COOH, CF3SO3H, HF,
4.4.2. (2-Methyl-4-pentenyl)(diphenyl)silyl
respectively). This comply with the possibility of parallel formation
of the products of rearrangement and elimination and the absence
of simultaneous formation of the products of elimination and addi-
tion (Table 1).
trifluoromethanesulfonate (5)
To silane 1 (1.06 g, 4.0 mmol) in absolute CH2Cl2 (5 mL) the
solution of triflic acid (0.60 g, 4.0 mmol) in CH2Cl2 (1 mL) was
added dropwise at room temperature in the course of 10 min
and stirred upon reflux during 4 h. After removal of solvent and
vacuum distillation of the residue the title compound 5 (0.78 g,
50%) was obtained as a colorless oil, b.p. 158–160 °C/1 mm Hg.
Anal. Calc. for C19H21F3O3SSi: C, 55.07; H, 5.07; F, 13.77; S, 7.73
Si, 6.76. Found: C, 54.60; H, 4.55; F, 13.20; S, 8.17; Si, 6.47%. dH
7.69 (4 H, m, Ho); 7.59 (2H, m, Hp); 7.50 (4H, m, Hm); 5.73 (1H,
ddt, J 17.0, 10.0, 7.1 Hz, CH@); 5.05 (1H, d, J 17.1 Hz, @CHtrans);
4.99 (1H, d, J 10.0 Hz, @CHcis); 2.09, 2.02 (1H, dt, J 7.0, 13.6 Hz,
CH2C@); 1.92 (1H, m, CH); 1.70 (1H, dd, J 15.4, 8.9 Hz, SiCHaHbC);
1.43 (1H, dd, J 15.4, 4.8 Hz, SiCHaHbC); 0.95 (3H, d, J 6.6 Hz,
CH3C); dC 136.30 (CH@); 134.79 (Cm); 131.73 (Cp); 129.59 (C1);
128.38 (Co); 118.30 (q, J 318 Hz, CF3); 116.79 (CH2); 44.30 (CH2Vi);
28.24 (CH); 22.23 (Me); 21.19 (SiCH2); dF ꢁ76.52; dSi 13.12.
3. Conclusion
The above experimental and theoretical investigation allows us
to conclude that reactions of diallylsilanes with electrophiles can
proceed in three principal directions – addition of electrophile,
elimination of the molecule of propene, and rearrangement includ-
ing elimination of one allyl group and its addition to the second al-
lyl group of the same molecule. The course of the reaction and the
composition of the reaction products depend on the acidity of the
electrophile and the nature of the substituents at silicon, and are
rather insensitive to the reaction conditions.
4. Experimental
4.4.3. Allyl(dimethyl)silyl trifluoroacetate (8)
To silane 2 (1.0 g, 7.1 mmol) in absolute CH2Cl2 (10 mL) the
solution of trifluoroacetic acid (0.81 g, 7.1 mmol) in CH2Cl2
(5 mL) was added dropwise at room temperature in the course of
40 min. The reaction mixture was refluxed for 1 h until evolution
of propene ceased. After removal of solvent and vacuum distilla-
tion of the residue the title compound 8 (0.77 g, 51%) was obtained
as a colorless liquid, b.p. 57–57.5 °C/115 mm Hg. Anal. Calc. for
4.1. General remarks
Reaction of silane 1 with complex BF3 ꢀ 2AcOH is described in
our previous work [1]. All reactions were carried out in argon
atmosphere. Flash chromatography was performed on silica gel
60 purchased from Merck.
C7H11F3O2Si: C, 39.62; H, 5.22. Found: C, 39.05; H, 5.15%.
mmax(li-
quid film) 2970, 1780, 1640, 1390, 1230, 1180, 1070, 805 cmꢁ1
;
4.2. Theoretical calculations
dH 5.74 (1H, ddt, J 8.2, 9.2, 17.5 Hz, CH@); 4.99 (2H, m, CH2@);
1.87 (2H, d, J 7.9 Hz, SiCH2); 0.41 (6H, s, SiCH3); dC 156.66 (q, J
All calculations were performed at the B3LYP/6-311+G(d,p) le-
vel of theory with the basis set augmented with polarization func-
tions on heavy atoms with full optimization of all variables using
the GAUSSIAN 03 suite of programs [15].
42.6 Hz, CO); 130.93 (CH@); 115.87 (@CH2); 114.59 (q,
J
285.9 Hz, CF3); 22.83 (SiCH2Vi); ꢁ2.85 (SiCH3); dF ꢁ75.73; dSi
28.48.
4.3. Spectroscopic measurements
4.4.4. Reaction of diallyl(dimethyl)silane (2) with complex BF3 ꢀ 2AcOH
To silane 2 (0.815 g, 5.8 mmol) in CH2Cl2 (50 mL) the solution of
complex BF3 ꢀ 2AcOH (1.09 g, 5.8 mmol) in CH2Cl2 (20 mL) was
added dropwise at room temperature during 1.5 h; the tempera-
IR spectra were taken on a Specord IR-75 instrument. 1H, 13C,
19F, 29Si NMR spectra were recorded on a Bruker DPX 400 spec-

E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
425
ture rised to 32 °C. The gaseous products evolved were trapped in
bubbler with CCl4 cooled to ꢁ20 °C. After the reaction was
completed the reaction mixture was stirred for 30 min at room
temperature and refluxed until the gas evolution ceased
(ꢂ30 min). The solution of the evolved gaseous products in CCl4,
judged from the data of 1H, 13C and 19F NMR spectroscopy with
cyclohexane as an internal standard, contained the mixture of
difluoro(dimethyl)silane (9) and propene.
6.60; Cl, 23.22; F, 12.44; Si, 18.40. Found: C, 39.19; H, 6.64; Cl,
23.72; F, 11.92; Si, 17.96%. dH 5.80 (1H, ddt, J 17.0, 10.1, 8.0 Hz,
CH@); 5.05 (1H, dq, J 17.0, 1.2 Hz, @CHtrans); 5.01 (1H, d, J
10.1 Hz, @CHcis); 2.90 (2H, dd, J 2.8, 3.1 Hz, CH2Cl); 1.88 (2H, dd,
J 7.5, 6.6 Hz, SiCH2Vi); 0.37 (3H, d, J 7.2 Hz, SiCH3); dC 130.76
(CH@); 116.08 (@CH2); 26.79 (d, J 19.0 Hz, CH2Cl); 20.83 (d, J
12.5 Hz, SiCH2Vi); ꢁ4.88 (d, J 13.8 Hz, SiCH3); dSi 20.31 (d, J
290.6 Hz).
4.4.5. Difluoro(dimethyl)silane (9).
4.4.9. Reaction of diallyl(chloromethyl)methylsilane (3)
with triflic acid
1
3
dH 0.27 (t, J 1.2 Hz, SiCH3); dF ꢁ129.79 (sept, JSiF 290.7 Hz, JHF
6.1 Hz). Propene. dH 5.69 (1H, ddq, J 17.0, 10.1, 6.4 Hz, CH@); 4.91
(1H, d, J 17.0 Hz, @CHtrans); 4.83 (1H, d, J 10.1 Hz, @CHcis); 1.66
(3H, d, J 6.4 Hz, CH3); dC 132.48 (CH@); 115.39 (@CH2); 18.81 (CH3).
To silane 3 (3.77 g, 21.6 mmol) in absolute CH2Cl2 (7 mL) the
solution of triflic acid (3.24 g, 21.6 mmol) in CH2Cl2 (8 mL) was
added dropwise at room temperature in the course of 50 min
and stirred at reflux during 4 h. After removal of solvent and vac-
uum distillation of the residue 4.11 g (total yield 63%) of the mix-
ture of products 13 and 14 in the ratio of 1:1 was obtained. After
repeat vacuum distillation compound 13 (1.4 g, 20%) with b.p.
125–130 °C/35 mm Hg and compound 14 (1.6 g, 21%) with b.p.
104–108 °C/35 mm Hg were obtained as colorless oils.
4.4.6. 2-[Allyl(chloromethyl)methylsilyl]-1-methylethyl
trifluoroacetate (10)
Prepared similar to 4 from diallyl(chloromethyl)methylsilane
(3) (1.245 g, 7.1 mmol) and trifluoroacetic acid (0.81 g, 7.1 mmol)
as colorless liquid. Purified by flash chromatography (hexane/ether
50:3–8:1, Rf 0.42); yield 1.5 g (73%). Anal. Calc. for C10H16ClF3O2Si:
C, 41.59; H, 5.54; Cl, 12.31; F, 19.76; Si, 9.71. Found: C, 41.68; H,
4.4.10. (Chloromethyl)(methyl)(2-methyl-4-pentenyl)silyl
5.71; Cl, 12.15; F, 20.00; Si, 9.61%.
mmax(liquid film) 2980, 1780,
trifluoromethanesulfonate (13)
1620, 1320, 1385, 1205, 1150, 810, 715 cmꢁ1; dH 5.74, 5.75 (1H,
ddt, J 16.9, 10.2, 8.1 Hz, CH@); 5.27 (1H, tq, J 6.5, 6.5 Hz, CHO);
4.93 (1H, ddt, J 16.9, 2.0, 1.0 Hz, @CHtrans); 4.92 (1H, ddt, J 10.2,
2.0, 1.0 Hz, @CHcis); 2.82, 2.81 (2H, s, CH2Cl); 1.69 (2H, dt, J 8.1,
1.0 Hz, SiCH2C@); 1.41 (3H, d, J = 6.2 Hz, CH3C); 1.314, 1.297 (1H,
dd, J 5.8 Hz, SiCH2C); 1.216, 1.199 (1H, dd, J 14.8, 6.7 Hz, SiCH2C);
0.169, 0.168 (3H, s, SiCH3); dC 156.96 (q, J 41 Hz, C@O); 132.66
(CH@); 115.00 (@CH2); 114.47 (q, J 286 Hz, CF3); 75.30 (CHO);
28.32, 28.26 (CH2Cl); 22.71 (CH3); 20.55, 20.52 (SiCH2CHMe);
20.30, 20.26 (SiCH2Vi); ꢁ6.02 (SiCH3); dF ꢁ75.55; dSi ꢁ0.298. From
the data of NMR spectroscopy, the compound is the mixture of
diastereomers. The assignment of signals was made using the
2D-HSQC procedure.
Anal. Calc. for C9H16F3ClO3SSi requires Cl, 10.94; S, 9.86; Si, 8.63.
Found: Cl, 11.61; S, 9.59; Si, 7.99%. dH 5.75 (1H, ddt, J 17.1, 10.2,
6.9 Hz, CH@); 5.05 (2H, m, @CH2); 3.07 (2H, s, CH2Cl); 2.06 (2H,
t, J 6.5 Hz, CH2Vi); 1.88 (1H, m, CH); 1.23 (1H, dd, J 15.5, 4.8 Hz, Si-
CHaHb); 1.03 (3H, d, J 6.6 Hz, CH3); 0.94 (1H, dd, J 15.5, 9.2 Hz, Si-
CHaHb); 0.65 (3H, s, SiCH3); dC 136.17 (CH@); 118.42 (q, J 318.5 Hz,
CF3); 116.94 (@CH2); 44.31 (CH2Vi); 28.10 (CH); 27.01 (CH2Cl);
22.20 (CH3); 20.89 (SiCH2); ꢁ3.50 (SiCH3); dF ꢁ76.40; dSi 29.50.
4.4.11. 2-Allyl(chloromethyl)methylsilyl
trifluoromethanesulfunate (14)
dH 5.77 (1H, ddt, J 7.8, 10.0, 17.1 Hz, CH@); 5.14 (2H, m, @CH2);
3.08 (2H, s, CH2Cl); 2.07 (2H, d, J 7.8 Hz, SiCH2Vi); 0.64 (3H, s,
SiCH3); dC 128.60 (CH@); 118.36 (q,
J 318 Hz, CF3); 118.06
4.4.7. (Chloromethyl)(fluoro)methyl(2-methyl-4-pentenyl)silane (11)
To silane 3 (0.529 g, 3.03 mmol) in absolute CH2Cl2 (3 mL) the
solution of complex BF3 ꢀ 2AcOH (0.57 g, 3.03 mmol) in CH2Cl2
(2 mL) was added dropwise during 10 min and stirred for 4 h upon
reflux. Then the mixture was washed with water to neutral
reaction and dried over CaCl2. After removal of solvent and vacuum
distillation of the residue 0.271 g of the crude product with b.p.
98–98.5 °C/37 mm Hg was obtained. The crude product containing
ꢂ90% of the title compound 11. Analytically pure sample of the title
compound 11 (0.354 g, 60%) was obtained by flash chromatography
(hexane/ether 40:1, Rf 0.77) as a colorless liquid. Anal. Calc. for
C8H16ClFSi: C, 49.34; H, 8.28; Cl, 18.20; F, 9.76; Si, 14.42. Found:
(@CH2); 25.78 (CH2Cl); 20.18 (SiCH2Vi); ꢁ4.82 (SiCH3); dF
ꢁ75.92. dSi 24.58.
Acknowledgements
The authors are grateful to V.I. Zhun’ (State Research Institute of
Chemistry and Technology of Organoelement Compounds, Mos-
cow) who kindly provided us with silanes 1 and 3, and to S.V. Kir-
pichenko (Irkutsk Institute of Chemistry, Irkutsk) for synthesis of
silane 12 and helpful discussions.
References
C, 49.48; H, 8.57; Cl, 18.31; F, 9.80; Si, 14.17%. mmax(liquid film)
2920–2970, 1640, 1405, 1270, 880 cmꢁ1; dH 5.75 (1H, m, CH@);
5.01 (2H, m, @CH2); 2.86 (2H, m, CH2Cl); 2.06 (1H, dt, J 14.0,
7.2 Hz, CHaHbC@); 2.00 (1H, dt, J 14.0, 6.9 Hz, CHaHbC@); 1.84
(1H, m, CH); 0.99 (3H, d, J 6.7 Hz, CH3); 0.97 (1 H, m, SiCHaHb);
0.72 (1H, m, SiCHaHb); 0.37 (3H, d, J 7.3 Hz, SiCH3); dC 136.82
(CH@); 116.34 (@CH2); 44.46, 44.42 (CH2Vin); 28.37, 28.35 (CH);
28.03, 27.87 (d, J 19.1 Hz, CH2Cl); 22.43, 22.38 (CCH3); 21.40,
21.36 (d, J 12.1 Hz, SiCH2); ꢁ3.58, ꢁ3.72 (d, J 22.5 Hz, SiCH3); dF
ꢁ163.25, ꢁ163.33 (d, J 289.9 Hz); dSi 24.14, 24.02 (d, J 288.6 Hz).
[1] E.N. Suslova, A.I. Albanov, B.A. Shainyan, Russ. J. Gen. Chem. (Engl. Transl.) 78
(2008) 873.
[2] A.D. Petrov, V.F. Mironov, V.A. Ponomarenko, E.A. Chernyshev, Synthesis of
organosilicon monomers, M.: AN SSSR, 1961, p. 550.
[3] V.I. Zhun’, A.L. Tsvetkov, Synthesis and properties of allylsilanes, M.:
NIITEKhim, 1990, p. 105.
[4] L. Chabaud, P. James, Y. Landais, Eur. J. Org. Chem. (2004) 3173.
[5] H.-U. Siehl, T. Müller, in: The Chemistry of Functional Groups. The Chemistry of
Organic Silicon Compounds, vol. 2, Part 1, 1998, p. 595.
[6] I. Fleming, A. Barbero, D. Walter, Chem. Rev. 97 (1997) 2063.
[7] D.G. Hall, J.W.J. Kennedy, Angew. Chem., Int. Ed. 42 (2003) 4732.
[8] V.V. Levin, A.D. Dilman, P.A. Belyakov, A.A. Korlyukov, M.I. Struchkova, V.A.
Tartakovsky, Eur. J. Org. Chem. (2004) 5141.
[9] Z.-L. Tang, Chinese J. Chem. 26 (2008) 525.
4.4.8. Allyl(chloromethyl)fluoro(methyl) silane (12)
[10] V.I. Zhun’, O.L. Ustinova, V.D. Sheludyakov, G.N. Turkel’taub, T.F. Slyusarenko,
S.N. Tandura, S.I. Androsenko, Zhurn. Obshch. Khim. 60 (1990) 1111.
[11] T. Akiyama, K. Asayama, S. Fujiyoshi, J. Chem. Soc. Perkin 1 (1998) 3655.
[12] G. Manuel, G. Bertrand, P. Mazerolles, J. Ancelle, J. Organometal. Chem. 212
(1981) 311.
Allyl(chloro)(chloromethyl)(methyl)silane Me(ClCH2)Si(Me)Cl
(12.25 g, 70 mmol) was treated with 50 mL of 40% aqueous HF, or-
ganic layer separated and dried over KF. After vacuum distillation
the title compound 12 (4.29 g, 35%) was obtained with b.p. 60–
65 °C/55 mm Hg. Anal. Calc. for C5H10ClFSi requires C, 39.34; H,
[13] W. Uhlig, J. Organomet. Chem. 452 (1993) 29.
[14] I. Fleming, J.A. Langley, J. Chem. Soc. Perkin 1 (1981) 1421.

426
E.N. Suslova et al. / Journal of Organometallic Chemistry 694 (2009) 420–426
[15] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, GAUSSIAN, Inc., Pittsburgh PA, 2003.