Towards bis(acylsilanes) and cyclic unsaturated acylsilanes via metathesis: an exploratory study

Article abstract of DOI:10.1016/j.tet.2009.02.085

New acyl(allyl)- and acyl(vinyl)silanes have been synthesized in order to explore cross metathesis or ring-closing metathesis as a new way towards bis(acyl)silanes or unsaturated cyclic acylsilanes, respectively. Metathesis from acylsilanes did not work b

Full text of DOI:10.1016/j.tet.2009.02.085

Tetrahedron 65 (2009) 5527–5534
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Tetrahedron
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Towards bis(acylsilanes) and cyclic unsaturated acylsilanes via metathesis: an
exploratory study
,
Catherine Hammaecher a, Jean-Philippe Bouillon b, Charles Portella a
*
a Universite´ de Reims Champagne-Ardenne, Institut de Chimie Mole´culaire de Reims, CNRS UMR 6229, UFR Sciences Exactes et Naturelles, BP 1039, 51687 Reims Cedex 2, France
b Universite´ de Rouen, Laboratoire Sciences et Me´thodes Se´paratives, EA 3233, UFR Sciences et Techniques, IRCOF, F-76821 Mont-Saint-Aignan cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
New acyl(allyl)- and acyl(vinyl)silanes have been synthesized in order to explore cross metathesis or
ring-closing metathesis as a new way towards bis(acyl)silanes or unsaturated cyclic acylsilanes, re-
spectively. Metathesis from acylsilanes did not work but their precursors, in particular in benzotriazol
series, proved to be good candidates. Two new benzotriazolyl substituted silacyclic compounds (tetra-
hydrosiline and dihydrosilol) were thus prepared by RCM. Their conversion into the corresponding
acylsilane failed. In contrast, the preparation of a bis(acylsilane) bearing the silicon atoms in internal
position was achieved by a two-step sequence: cross metathesis of an allyl(dimethylsilyl) benzotriazolyl
intermediate–hydrolysis.
Received 15 December 2008
Received in revised form 5 February 2009
Accepted 6 February 2009
Available online 14 April 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
encountered in trying to engage these compounds in metathesis
prompted us to consider also their precursors in such reactions.
Acylsilanes are versatile intermediates in organic synthesis.1
Bis(acylsilanes) (BAS) have been less investigated, in spite of in-
teresting properties; they indeed can undergo domino processes
combining nucleophilic addition and Brook rearrangement. Two
kinds of bis(acylsilanes) have to be considered: compounds with
external trialkylsilyl or triarylsilyl groups (Type 1 BAS, Fig. 1) and
those having internal silicon and external acyl moieties (Type 2
BAS, Fig. 1). If several studies on synthesis and/or reactivity of Type
1 BAS were reported in the literature,2 those related to type 2 BAS
(internal silyl groups) are rare, probably because the proposed
methodologies for their preparation are not effective or may not be
generalized.3 We hypothesize that type 2 BAS could be prepared via
a cross metathesis reaction between acyl(vinyl)- or acyl(allyl)si-
lanes, which led us to undertake the synthesis of a series of allyl-
and vinylacylsilanes. During these synthesis compounds bearing
a second unsaturation on the acyl moiety were also prepared in
order to explore their ring-closing metathesis. The difficulties
This paper discloses the results of this exploratory study.
2. Results and discussion
2.1. Preparation of starting acylsilanes
Surprisingly, before this study, acyl(allyl)silanes seemed to have
been reported only by Tsai’s group who studied intramolecular
radical addition on the allyl unsaturation,4 and by our group, which
very recently reported their remarkable photochemical behaviour.5
Similarly, only one paper was found mentioning an acyl(vinyl)si-
lane obtained in very low yield.6 We have prepared a series of
acyl(allyl)- and acyl(vinyl)dimethylsilanes (Table 1) according to
the retrosynthetic routes depicted in Scheme 1. A Brook–Corey type
strategy (method A)7 or a Katritzky type strategy (method B),8 both
modified in the last step, allowed us to obtain the desired
S
S
S
S
O
O
O
O
R1 SiMe2R2
A
R
R1
R'
Si
Si
R'
R'3Si
SiR'3
R
O
R2
R
R R
R
R1
Si
N
N
N
Type 1 BAS
Type 2 BAS
N
B
N
Figure 1.
1
N
R1
OPh
R2Me2Si
OPh
* Corresponding author. Tel.: þ33326913234; fax: þ33326913166.
E-mail address: charles.portella@univ-reims.fr (C. Portella).
Scheme 1. Retrosynthesis of acyl(allyl)- and acyl(vinyl)silanes.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.02.085

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C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
1) n-BuLi
THF, -15 °C
1/ (CF3CO2)2IPh
NaHCO3, MeOH
HS(CH2)3SH
R1CHO
S
S
S
S
Method A:
R2
2/ H3O+
2) ClSiMe2R2
R1 Si
BF3.OEt2
CH2Cl2
R1
2
3
O
R2
(R1 = Alkyl, phenyl; R2 = Allyl, Vinyl)
R1 Si
1
1) n-BuLi, THF, -78 °C
2) ClSiMe2R2
PhO Bt
R1 Si
FeCl3, acetone
R2
Method B:
PhO
Bt
3) n-BuLi
4) R1Br
Bt = 1-benzotriazolyl
4
Scheme 2. Synthesis of acyl(allyl)- and acyl(vinyl)silanes 1a–1k.
compounds. The reaction conditions and the results are depicted in
Scheme 2 and Table 1.
a double bond on both acyl and silyl moieties, ring-closing me-
tathesis (RCM). Metathesis reactions on such substrates are un-
precedented, but are well documented for vinyl and allylsilanes.
The later gave selectively a cross metathesis (CM)11 or RCM12 with
olefinic double bonds. Metathesis of vinylsilanes was deeply stud-
ied and was shown to proceed via metallacarbene or transsilylation
mechanisms depending on catalyst and silicon substituents.13 The
metathesis reactivity of vinylsilanes strongly depends on the sub-
stituents on silicon, and the selectivity CM versus SCM also depends
on the alkene structure.14 SCM giving bis(silyl)alkenes seems to
occur effectively only with alkoxysubstituted vinylsilanes.15
Grubbs second generation (Grubbs II) catalyst has been chosen
to explore the RCM of bis(unsaturated) acylsilanes. The RCM of
acylsilane 1g was unsuccessful: the starting material was recovered
whatever the reaction conditions (solvent, temperature), possibly
because of the presence of acidic allylic hydrogens able to de-
activate the catalyst. We reasoned that a cyclization on the in-
termediate 3f, followed by hydrolytic removal of dithioketal could
give the targeted acylsilane. Indeed, an analogous non-silylated 2-
allyl-2-homoallyl-1,3-dithiane was reported to cyclize under
Grubbs II catalysis.16 Compound 3f proved to react in the presence
of Grubbs II catalyst (2ꢀ5%), but the reaction led to a compound,
which exhibits spectral characteristics in agreement with the CM
product 5 (Scheme 4). Unfortunately, the reaction was not re-
producible and we were unable to have a correct elemental analysis
of this product. Lowering the substrate concentration did not
change the course of the reaction. These results may be due to some
competitive oligomerization.
Owing to the presence of the unsaturation, the conditions for
releasing the carbonyl group in the last step are not trivial. In the
dithiane series (Scheme 2: method A), after some unsuccessful
attempts with reagents either ineffective or which gave complex
mixtures, we have used bis(trifluoroacetoxy)iodobenzene. This
reagent was shown to release aldehydes or ketones from their
corresponding dithio(a)cetals including those bearing a double
bond.9 It was also reported to yield acyl(allyl)silanes from dithiane
precursors.4 When 3a was treated under the reported conditions
for direct obtention of the acylsilane, a low conversion and partial
degradation of the product were observed. A previous conversion
of the dithioketal moiety into a ketal function and aqueous acidic
work-up allowed us to obtain the desired acylsilane in acceptable
yield. These conditions were applied for all allyl- and vinyl-
(acyl)silanes prepared through dithiane intermediates 3 (Table 1).
Similarly, after numerous attempts to hydrolyze the benzo-
triazole-substituted intermediates 4, we decided to investigate
ferric chloride (method B), a Lewis acid, which catalyzes effectively
ketal hydrolysis.10 The conversion of intermediates 4 into the cor-
responding acylsilanes 1 was eventually achieved using anhydrous
ferric chloride in acetone (Table 1). The products were obtained in
high yields except for but-3-enoyl derivatives 1g and 1k. The direct
obtention of the final acylsilane via in situ hydrolysis by diluted
hydrochloric acid according to Katritzky procedure8 was achieved
only for the allyl compound 1e (67% overall yield).
We then turn to the intermediates prepared following the
benzotriazole route. The results of RCM of compounds 4 are sum-
marized in Table 2. Good yields of tetrahydrosiline 6g (from 4g) and
2.2. Metathesis experiments
Having these acylsilanes in hand, we were interested to attempt
self cross metathesis reaction (SCM) and, for compounds bearing
1) n-BuLi
THF, 0 °C
2) AllBr
Table 1
Synthesis of acyl(allyl)- and acyl(vinyl)silanes 1a–1k
S
S
S
All
S
Si
All
R1
R2 Method Intermediate Intermediate Intermediate Acylsilane
Si All
2 (%)
3 (%)
4 (%)
1 (%)
Ph
All
All
All
All
All
All
All
A
A
A
A
B
A
B
B
A
B
B
2aa
3a (94)
3b (72)
3c (75)
3d (70)
d
d
1a (62)
1b (88)
1c (60)
1d (75)
1e (95)
1f (30)c
1g (25)
1h (80)
1i (60)
1j (94)
1k (35)
3f (89%)
1/ (CF3CO2)2IPh
2f
c-C6H11
PhCH2CH2
PhCH2
n-C10H21
All
2b (80)
2c (90)
2d (93)
d
2fb
d
d
d
d
2/ H3O+
NaHCO3
MeOH
4e (70)
d
3f (89)
d
All
4g (75)
4h (58)
d
Pent-4-enyl All
Ph
n-C10H21
All
d
d
2ia
d
3i (89)
d
O
Vin
Vin
Vin
4j (60)
4k (65)
All
Si
d
d
a
2-Phenyl-1,3-dithiane is commercially available.
From 2-[allyl(dimethyl)silyl]dithiane (yield: 78%).
Isomerization to but-2-enoylsilane during hydrolysis (see Scheme 3).
1f (30%)
Scheme 3. Synthesis of but-2-enoyl(dimethyl)allylsilane 1f.
b
c

C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
5529
Compounds 6 were expected to be synthetic equivalents of the
corresponding cyclic unsaturated acylsilanes so far unprecedented.
Unfortunately, hydrolysis experiments either gave unexpected or
degradation products. Various Bronsted or Lewis acid conditions
were investigated. Using ytterbium triflate hydrate as Lewis acid, an
elimination occurred leading to the benzotriazolyldihydrosiline 7
(36% yield) from a rather complex mixture (Scheme 5). In order to
prevent a degradation possibly due to the presence of the double
bond, hydrogenation of 6g was carried out giving compound 8 in
98% yield. Treatment of 8 under the conditions optimized for the
preparation of acylsilanes 1 from intermediates 4 (method B)
seemed to convert cleanly 8 but we were unable to isolate any
compound (Scheme 5).
S
S
Si
3f
Grubbs II (10%)
CH2Cl2, reflux
~85% (~50/50)
S
S
Si
S
S
Si
5
After these somewhat disappointing results in RCM, we have
explored the possibility to engage vinyl- and allyl(acyl)silanes 1 in
SCM in order to have a new access to type 2 BAS. Grubbs first and
second generation and Hoveyda–Grubbs catalysts were screened.
No reaction was observed with Grubbs I and Hoveyda–Grubbs
catalysts, whatever the vinylsilyl or allylsilyl nature of the substrate
and the solvent/temperature conditions. In toluene at 80 ꢁC a slow
conversion of 1a was observed but the bis(acylsilane) degrades as it
is formed. CM reactions between allylsilyl and vinylsilyl derivatives
(1aþ1i or 1eþ1j) were unsuccessful as well. As for RCM, we then
attempted to perform the metathesis before the final hydrolysis.
We did not observed any SCM or CM from each possible combi-
nation between dithiane intermediates 3a–3d and/or 3i. The ex-
periments on benzotriazole derivatives were much more gratifying.
The intermediate 4j did not react under Grubbs II catalysis in
dichloromethane, but in these conditions, the allyl analogue 4e was
totally converted within 5 h and the 1,6-disilahex-3-ene 9 was
isolated in 52% yield as a (60:40) mixture of stereomers (Scheme 6).
This result is interesting since homocoupling between allylsilanes,
when observed, is a very minor reaction compared to cross cou-
pling with various alkenes.11 Finally, compound 9 was cleanly and
quantitatively converted into the type 2 BAS 10 under treatment
with Fe(III) chloride in acetone.
Scheme 4. CM of 2-allyl-2-allylsilyl-1,3-dithiane 3f.
Table 2
RCM of benzotriazole derived intermediates 4
OPh
Si
Bt
OPh
Si
Bt
Conditions
m
n
m
n
4
6
Substrate
m
n
Conditions
Products (%)
4g
4h
1
3
1
1
10% Grubbs II, CH2Cl2, reflux, 5 h
6g (82)
d
15% Grubbs II, toluene, 80 ꢁC, 24 or
CH2Cl2, reflux, 5 h
4k
1
0
7ꢀ2% Grubbs II, toluene, 80 ꢁC, 24 h
6k (80)
Bt
Si
7 (36%)
OPh
Si
Bt
3. Conclusion
Yb(OTf)3.2H2O
toluene, reflux
We have synthesized avariety of newacylsilanes 1 with an allyl or
a vinyl group linked to silicon. The objective to prepare type 2
bis(acylsilanes) and unsaturated cyclic acylsilanes via cross me-
tathesis or ring-closing metathesis proved to be difficult to achieve.
Coupling from acyl(allyl)- or acyl(vinyl)silanes being difficult, we
tried to overcome the problem by treatment of their precursors
under metathesis conditions. Two new benzotriazole-substituted
five and six membered silacyclic compounds 6 were thus prepared
by RCM. They were submitted to hydrolytic treatment but the cor-
responding acylsilanes could not be obtained. In contrast, we ach-
ieved the preparation of a bis(acylsilane) of type 2, bearing the silicon
atoms in internal position, by a two-step sequence: cross metathesis
of an allyl(dimethylsilyl) benzotriazolyl intermediate–hydrolysis.
Owing to the exploratory character of this study, we have not
insights on the scope and limitation of this route, which however
seems to be valuable for acyclic compounds bearing a four carbon
spacer between silicon atoms.
6g
MeOH
H2, Pd/C
O
Bt OPh
Si
FeCl , Xacetone
3
Si
8 (98%)
Scheme 5. Hydrolysis and hydrogenation of tetrahydrosiline 6g.
dihydrosilol 6k (from 4k) were obtained using at least 10% of cat-
alyst. The reaction failed for higher homologue 4h. The geminal
substitution by two sterically hindered and electro rich groups
might account for the successful cyclization of intermediates 6
comparatively to the dithiane intermediate 3f.
O
Bt OPh
Si
Bt OPh
FeCl3
Grubbs II (10%)
CH2Cl2
reflux, 5h
Si
R
Si
R
R
R
Si
R
Si
acetone, 1h
Bt OPh
O
4e
9
10
95% (60/40)
(R = n-C10H21
)
52% (60/40)
Scheme 6. Synthesis of bis(acylsilane) 10 via SCM of benzotriazole derivative 4e.

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C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
4. Experimental
J¼14.3, 3.6 Hz), 2.96 (dt, 2H, SCH2, J¼12.5, 3.0 Hz), 4.8–4.9 (m, 2H),
5.7–5.9 (m, 1H). 13C NMR:
(2ꢀSCH2), 24.4 (SCH2CH2CH2S), 26.3 (CH2), 27.4 (2ꢀCH2), 31.1
(2ꢀCH2), 43.8 (Cq), 45.6 (CH), 113.5 (CH2]), 134.6 (CH]). GC–MS:
m/z (%) 300 (Mþ), 259, 217, 201 (100). Anal. Calcd for C15H28S2Si
(300.590): C 59.93, H 9.39; found C 60.04, H 9.63.
d
¼ꢂ3.0 (Si(CH3)2), 22.9 (SiCH2), 23.8
4.1. Materials and general methods
Melting points are uncorrected. FTIR spectra were recorded on
a MIDAC Corporation Spectrafile IR apparatus. 1H and 13C spectra
were recorded on a Bruker AC-250 or AC-500 spectrometer with
CDCl3 as the solvent. Tetramethylsilane (
d
¼0.00 ppm) or CHCl3
4.2.3. 2-(Allyldimethylsilyl)-2-phenethyl-1,3-dithiane 3c
(
d
¼7.27 ppm) was used as internal standards for 1H, CDCl3
Yield: 0.89 g (75%). Oil. TLC: Rf¼0.33 (EP/AcOEt 99:1). IR (film):
(d
¼77.23 ppm) for 13C NMR spectra. GC–MS spectra were obtained
3061, 2948,1628,1495,1454,1249, 699 cmꢂ1. 1H NMR:
d
¼0.14 (s, 6H,
on Trace MS Thermoquest apparatus (70 eV) in electron impact
mode (EI). High Resolution Mass Spectra (HRMS) were performed on
Q-TOF Micromass in positive ESI mode (CV¼30 V). Elemental anal-
yses were performed with a Perkin–Elmer CHN 2400 apparatus.
Reactions were monitored by TLC (Merck F254 silica gel). All anhy-
drous reactions were carried out under dry argon. THF and toluene
were dried and distilled from sodium/benzophenone. Dichloro-
methane was dried and distilled over calcium hydride. All other
commercially available starting materials were used without further
purification. Products were usually separated by chromatography on
silica gel using a mixture of petroleum ether (EP) and ethyl acetate.
2-Phenyl-1,3-dithiane 2a is commercially available. The 2-alkyl-
1,3-dithianes 2b–2d used for the preparation of acylsilanes
(method A) were prepared from the corresponding aldehydes and
propane-1,3-dithiol in dichloromethane under BF3$OEt2 catalysis.
Their spectral data were consistent with those reported in litera-
ture: 2b and 2c,17 2d.18 2-Allyl(dimethyl)silyl-1,3-dithiane4 used in
the preparation of 3f and 1-phenoxymethylbenzotriazole19 used in
method B were prepared according to reported procedures.
Si(CH3)2), 1.74 (d, 2H, SiCH2, J¼8.1 Hz), 1.8–2.0 (m, 2H), 2.2–2.4 (m,
2H), 2.6–2.8 (m, 4H), 2.87 (t, 2H, J¼12.8 Hz), 4.8–4.9 (m, 2H, CH2]),
5.6–5.8 (m, 1H, CH]), 7.0–7.1 (m, 5H, Ph). 13C NMR:
d¼ꢂ4.9
(Si(CH3)2), 21.0 (SiCH2), 23.0 (2ꢀSCH2), 24.7 (SCH2CH2CH2S), 34.1
(CH2), 38.3 (Cq), 39.5 (CH2),113.9 (CH2]),125.6 (CH Ph),128.0 (2ꢀCH
Ph), 128.2 (2ꢀCH Ph), 134.0 (CH]), 141.9 (Cq). GC–MS: m/z (%) 322
(Mþ), 281, 223 (100), 191, 149, 115, 91. Anal. Calcd for C17H22S2Si
(322.604): C 63.64, H 8.12, S 19.88; found C 63.29, H 8.10, S 20.22.
4.2.4. 2-(Allyldimethylsilyl)-2-benzyl-1,3-dithiane 3d
Yield: 0.75 g (70%). Oil. TLC: Rf¼0.31 (EP/AcOEt 99:1). IR (film):
3060, 2915, 1628, 1493, 1453, 1248 cmꢂ1
.
1H NMR:
d¼0.10 (s, 6H,
Si(CH3)2), 1.69 (d, 2H, SiCH2, J¼8.1 Hz), 1.8–2.0 (m, 2H,
SCH2CH2CH2S), 2.28 (dt, 2H, SCH2, J¼14.0, 3.8 Hz), 2.6–2.8 (m, 2H),
3.35 (s, 2H, CH2Ph), 4.8–4.9 (m, 2H, CH2]), 5.7–5.9 (m, 1H, CH]),
7.3–7.5 (m, 5H, Ph). 13C NMR:
(SCH2CH2CH2S), 24.1 (2ꢀSCH2), 37.7 (Cq), 45.0 (CH2), 113.8 (CH2]),
126.7 (CH Ph),127.8 (2ꢀCH Ph),131.0 (2ꢀCH Ph),134.5 (CH]),138.6
(Cq). GC–MS: m/z (%) 308 (Mþ), 267, 217 (100), 209, 134, 99, 91.
d
¼ꢂ5.6 (Si(CH3)2), 20.7 (SiCH2), 24.0
4.2. General procedure for the preparation of 2-alkyl (or 2-
phenyl)-2-allyldimethyl (or dimethylvinyl)silyl-1,3-dithianes 3
(Scheme 2: method A)
4.2.5. 2-(Allyldimethylsilyl)-2-(prop-2-enyl)-1,3-dithiane 3f
The procedure was similar to the general one, but consisted in
metallation (BuLi)-allylation (AllBr) of 2-allyl(dimethyl)silyl-1,3-
dithiane 2f.
To a solution of 2-alkyl (or 2-phenyl)-1,3-dithianes 2a–2d
(4.95 mmol) in THF (50 mL), cooled at ꢂ15 ꢁC, was added a solution
of n-butyllithium (2.5 M in hexane, 1.98 mL, 1.0 equiv). The reaction
mixture was stirred for 3 h and was allowed to reach room temper-
ature then chloroallyldimethylsilane (or chlorovinyldimethylsilane)
(4.95 mmol, 1.0 equiv) was added. The stirring was maintained (12–
15 h) until the disappearance of the starting material (checked by
TLC, eluent: EP/AcOEt 99:1). At the end of the reaction, aqueous
saturated solution of NaHCO3 (25 mL) was added and then the two
phases were separated. The aqueous phase was extracted three times
with ether (3ꢀ20 mL). The combined organic phases were dried over
MgSO4 and filtered off. After evaporation of solvent, the residue was
purified by silica gel column chromatography (eluent: EP/AcOEt
99:1) affording the corresponding silyl-1,3-dithianes 3 (Table 1).
Yield: 0.62 g (89%). Oil. TLC: Rf¼0.25 (EP/AcOEt 99:1). IR (film):
3075, 2954, 1629, 1422, 1248, 1029, 915, 825 cmꢂ1. 1H NMR:
d
¼0.16
(s, 6H, Si(CH3)2), 1.78 (d, 2H, SiCH2, J¼8.0 Hz), 1.7–2.2 (m, 2H,
SCH2CH2CH2S), 2.45 (dt, 2H, H2C]CH–CH2, J¼10.2, 3.7 Hz), 3.0–3.2
(m, 4H, SCH2CH2CH2S), 4.8–4.9 (m, 2H), 5.0–5.2 (m, 2H), 5.6–5.8 (m,
1H), 5.9–6.1 (m, 1H). 13C NMR:
d
¼ꢂ5.1 (Si(CH3)2), 21.0 (SiCH2), 23.2
(2ꢀCH2, SCH2CH2CH2S), 24.9 (SCH2CH2CH2S), 37.7 (Cq), 41.5 (CH2),
113.8 (SiCH2CH]CH2), 116.6 (CH2]), 134.3 (SiCH2CH]CH2), 136.4
(CH]). GC–MS: m/z (%) 258 (Mþ), 217, 159 (100), 127, 121, 99, 59.
Anal. Calcd for C12H22S2Si (258.518): C 55.75, H 8.58, S 24.81; found
C 56.14, H 8.53, S 25.01.
4.2.6. 2-Dimethyl(vinyl)silyl-2-phenyl-1,3-dithiane 3i
Yield: 1.10 g (89%). White solid. Mp 81 ꢁC (recrystallized from
EtOH). TLC: Rf¼0.26 (EP/AcOEt 99:1). IR (film): 2945, 2897, 1590,
4.2.1. 2-(Allyldimethylsilyl)-2-phenyl-1,3-dithiane 3a
1477, 1417, 1244 cmꢂ1. 1H NMR:
d
¼0.11 (s, 6H, Si(CH3)2), 1.9–2.2 (m,
Yield: 1.27 g (94%). Oil. TLC: Rf¼0.34 (EP/AcOEt 99:1). IR (film):
2H, SCH2CH2CH2S), 2.41 (dt, 2H, SCH2, J¼14.2, 3.4 Hz), 2.76 (td, 2H,
SCH2, J¼14.2, 2.9 Hz), 5.66 (dd, 1H, Jtrans¼18.6 Hz, Jgem¼5.3 Hz), 6.09
(dd, 1H, Jcis¼14.7 Hz, Jgem¼5.3 Hz), 6.13 (dd, 1H, Jtrans¼18.6 Hz,
Jcis¼5.3 Hz), 7.18 (tt, 1Hpara, J¼7.7, 1.2 Hz), 7.35 (td, 2Hmeta, J¼7.7,
2953, 2903,1628,1591,1477,1441,1421,1248 cmꢂ1.1H NMR:
d¼ꢂ0.02
(s, 6H, Si(CH3)2), 1.56 (d, 2H, SiCH2, J¼7.8 Hz), 1.8–2.0 (m, 2H,
SCH2CH2CH2S), 2.35 (dt, 2H, SCH2, J¼14.2, 3.2 Hz), 2.76 (td, 2H, SCH2,
J¼14.2, 2.4 Hz), 4.73 (dd, 2H, Jtrans¼13.9 Hz, Jgem¼1.2 Hz), 5.5–5.8 (m,
1H), 7.21 (td,1Hpara, J¼7.4, 1.2 Hz), 7.32 (dt, 2Hmeta, J¼7.4, 1.5 Hz), 7.84
1.2 Hz), 7.89 (dt, 2Hortho, J¼7.7, 1.2 Hz). 13C NMR:
¼ꢂ5.9 (Si(CH3)2),
d
25.0 (3ꢀCH2, SCH2CH2CH2S), 46.7 (Cq), 125.2 (CH Ph), 128.2 (2ꢀCH
Ph), 129.6 (2ꢀCH Ph), 134.3 (CH2]), 134.4 (CH]), 140.0 (Cq Ph).
GC–MS: m/z (%) 280 (Mþ), 195 (100), 163, 121, 85, 77. Anal. Calcd for
C14H20S2Si (280.520): C 59.94, H 7.19; found C 59.61, H 7.39.
(dd, 2Hortho, J¼7.4, 1.2 Hz). 13C NMR:
¼ꢂ6.2 (Si(CH3)2), 20.1 (SiCH2),
d
25.0 (3ꢀCH2, SCH2CH2CH2S), 47.3 (Cq), 114.0 (CH2]), 125.3 (CH Ph),
128.3 (2ꢀCH Ph), 129.5 (2ꢀCH Ph), 134.0 (CH]), 140.2 (Cq Ph). GC–
MS: m/z (%) 294 (Mþ), 253,195,163,135,121 (100), 99, 77. Anal. Calcd
for C15H20S2Si (294.093): C 61.16, H 7.53; found C 61.04, H 7.84.
4.3. General procedure for the oxidative hydrolysis of 1,3-
dithianyl derivatives 3 into allyl- (or vinyl-) (acyl)silanes 1
(Scheme 2: method A)
4.2.2. 2-(Allyldimethylsilyl)-2-cyclohexyl-1,3-dithiane 3b
Yield: 0.76 g (72%). Oil. TLC: Rf¼0.32 (EP/AcOEt 99:1). IR (film):
2926, 2851, 1628, 1449, 1246, 824 cmꢂ1
.
1H NMR:
d
¼0.22 (s, 6H,
To a solution of 2-alkyl (or 2-phenyl)-1,3-dithianes 3 (0.67 mmol)
in methanol (3 mL) were successively added NaHCO3 (2.68 mmol,
Si(CH3)2), 1.1–1.3 (m, 5H), 1.6–2.4 (m, 10H), 2.46 (dt, 2H, SCH2,

C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
5531
4 equiv) and bis(trifluoroacetoxy)iodobenzene (1.34 mmol, 2 equiv).
The mixture was stirred at room temperature until the disappear-
ance of the starting material (45–75 min) then, it was poured into
a mixture of 1 M hydrochloric acid (15 mL) and ether (15 mL). After
the separation of the two phases, the aqueous layer was extracted
three times with ether (3ꢀ5 mL). The combined organic phases were
dried over MgSO4, filtered off and concentrated in vacuo. The residue
was purified by silica gel column chromatography (eluent: EP/AcOEt
99:1) affording the corresponding acylsilanes 1 (Table 1).
(CH Ph), 134.1 (CH2]), 135.5 (CH]), 141.0 (Cq Ph), 233.2 (C]O).
GC–MS: m/z (%) 190 (Mþ), 189 (100), 175, 105, 85, 77, 59. HRMS
(ESI): calcd for C11H14ONaSi: m/z 213.0712, found: 213.0716.
4.4. Preparation of allyl(1-benzotriazolyl-1-phenoxy-
alkyl)dimethylsilane and 1-benzo-triazolyl-1-phenoxy-
alkyl(dimethyl)vinylsilane: general procedure (Scheme 2:
method B)
To a solution of 1-phenoxymethylbenzotriazole (5.0 mmol) in
THF (70 mL), at ꢂ78 ꢁC, was added a solution of n-butyllithium
(2.5 M in hexane, 2.0 mL, 1 equiv) and then the reaction mixture
was stirred for 2 min at the same temperature. Chloro-
allyldimethylsilane (or chlorovinyldimethylsilane) (5.0 mmol,
1 equiv.) was added and the resulting mixture was stirred for 5 min,
at ꢂ78 ꢁC. One more equivalent of n-butyllithium (2.5 M, 2.0 mL)
was added and the resulting mixture was again stirred for 2 min at
ꢂ78 ꢁC. Finally, alkyl or allyl bromide (5.0 mmol, 1 equiv) was
added. The reaction was stirred for 5 min at ꢂ78 ꢁC then for 5 min
at room temperature. Water (40 mL) was added to the resulting
solution then the aqueous phase was extracted three times with
ether (3ꢀ50 mL). The combined organic phases were dried over
MgSO4, filtered off and concentrated in vacuo. The residue was
purified by silica gel column chromatography (eluent: EP/AcOEt
97:3) affording the corresponding 1H-benzotriazoles 4 (Table 1).
4.3.1. Allyl(benzoyl)dimethylsilane 1a
Yield: 51 mg (62%). Yellow oil. TLC: Rf¼0.60 (EP/AcOEt 99:1). IR
(film): 2957, 2826, 1629, 1447, 1249 cmꢂ1
.
1H NMR:
d
¼0.18 (s, 6H,
Si(CH3)2), 1.67 (d, 2H, SiCH2, J¼8.0 Hz), 4.6–4.8 (m, 2H, CH2]), 5.5–
5.6 (m, 1H, CH]), 7.1–7.9 (m, 5H, Ph). 13C NMR:
d¼ꢂ3.7 (Si(CH3)2),
22.1 (SiCH2), 114.2 (CH2]), 127.1 (2ꢀCH Ph), 128.3 (2ꢀCH Ph), 132.5
(CH Ph), 132.9 (CH]), 141.1 (Cq Ph), 234.0 (C]O). GC–MS: m/z (%)
204 (Mþ), 203 (100), 189, 135, 130, 99, 77, 59. HRMS (ESI): calcd for
C12H16ONaSi: m/z 227.0868, found: 227.0870.
4.3.2. Cyclohexyl(allyldimethylsilyl)ketone 1b
Yield: 111 mg (88%). Oil. Rf¼0.18 (EP/AcOEt 99:1). IR (film): 2928,
1636, 1449, 1258, 822 cmꢂ1. 1H NMR:
d
¼0.21 (s, 6H, Si(CH3)2), 1.1–
1.3 (m, 6H), 1.6–1.8 (m, 6H), 2.68 (t, 1H, J¼9.6 Hz), 4.8–4.9 (m, 2H,
CH2]), 5.6–5.8 (m, 1H, CH]). 13C NMR:
d¼ꢂ4.6 (Si(CH3)2), 21.6
(SiCH2), 25.6 (2ꢀCH2), 26.0 (CH2), 26.5 (2ꢀCH2), 55.7 (CH), 114.2
(CH2]), 133.3 (CH]), 249.3 (C]O). GC–MS: m/z (%) 210 (Mþ), 127,
99 (100), 83, 73.
4.4.1. Allyl(1-(benzotriazol-1-yl)-1-phenoxyundecyl)dimethyl-
silane 4e
Yield: 1.13 g (70%). Oil. Rf¼0.28 (EP/AcOEt 97:3). IR (film): 2925,
4.3.3. Allyl(dimethyl)(3-phenylpropanoyl)silane 1c
2854, 1629, 1589, 1489, 1250 cmꢂ1. 1H NMR:
d¼0.21 (s, 3H, SiCH3),
Yield: 56 mg (60%). Oil. Rf¼0.22 (EP/AcOEt 99:1). IR (film): 2955,
0.22 (s, 3H, SiCH3), 0.87 (t, 3H, CH3, J¼6.7 Hz), 1.1–1.5 (m, 16H), 1.77
(d, 2H, SiCH2, J¼7.6 Hz), 2.4–2.7 (m, 2H), 4.8–4.9 (m, 2H), 5.6–5.8
(m, 1H), 6.46 (d, 2H, 2ꢀCH Ph, J¼7.9 Hz), 6.8–7.0 (m, 3H, 3ꢀCH Ph),
7.2–7.3 (m, 2H, 2ꢀCH Bt), 7.5–7.6 (m, 1H, CH Bt), 8.0–8.1 (m, 1H, CH
1643, 1497, 1250, 825, 698 cmꢂ1. 1H NMR:
d
¼0.29 (s, 6H, Si(CH3)2),
1.78 (d, 2H, SiCH2, J¼8.0 Hz), 2.9–3.0 (m, 4H), 4.9–5.0 (m, 2H,
CH2]), 5.7–5.9 (m, 1H, CH]), 7.2–7.4 (m, 5H, Ph). 13C NMR:
d
¼ꢂ5.3
(Si(CH3)2), 21.0 (SiCH2), 28.0 (CH2), 50.8 (CH2), 114.4 (CH2]), 125.9
(CH Ph), 128.3 (2ꢀCH Ph), 128.5 (2ꢀCH Ph), 133.0 (CH]), 141.5 (Cq),
245.7 (C]O). GC–MS: m/z (%) 232 (Mþ), 141, 99, 91 (100), 75, 59.
HRMS (ESI): calcd for C14H20ONaSi: m/z 255.1181, found: 255.1175.
Bt). 13C NMR:
d
¼ꢂ3.1 (Si(CH3)2), 13.9 (CH3), 22.4 (CH2), 22.4 (CH2),
23.5 (CH2), 28.9 (CH2), 29.0 (CH2), 29.1 (CH2), 29.2 (CH2), 29.6 (CH2),
31.6 (CH2), 37.2 (CH2), 95.9 (Cq), 113.2 (CH Bt), 114.1 (CH2]), 119.5
(CH Bt), 120.6 (2ꢀCH Ph), 123.3 (CH Ph), 123.7 (CH Bt), 127.0 (CH Bt),
128.9 (2ꢀCH Ph), 133.2 (Cq Bt), 133.6 (CH]), 146.0 (Cq Bt), 155.0 (Cq
Ph). HRMS (ESI): calcd for C28H41N3ONaSi: m/z 486.2917, found:
486.2926.
4.3.4. Allyl(dimethyl)(2-phenylethanoyl)silane 1d
Yield: 82 mg (75%). Oil. Rf¼0.18 (EP/AcOEt 99:1). IR (film): 2959,
1634, 1495, 1257, 838, 701 cmꢂ1. 1H NMR:
d
¼0.12 (s, 6H, Si(CH3)2),
1.61 (dd, 2H, SiCH2, J¼8.0, 0.9 Hz), 3.85 (s, 2H, CH2CO), 4.8–4.9 (m,
4.4.2. Allyl(1-(benzotriazol-1-yl)-1-phenoxybut-3-enyl)-
dimethylsilane 4g
2H, CH2]), 5.6–5.8 (m, 1H, CH]), 7.12 (d, 2H, 2ꢀCH Ph, J¼6.9 Hz),
7.2–7.3 (m, 3H Ph). 13C NMR:
d
¼ꢂ4.7 (Si(CH3)2), 21.6 (SiCH2), 56.2
Yield: 1.01 g (75%). Oil. TLC: Rf¼0.36 (EP/AcOEt 96:4). IR (film):
(CH2), 114.6 (CH2]), 127.0 (CH Ph), 128.8 (2ꢀCH Ph), 130.1 (2ꢀCH
Ph), 133.0 (Cq), 133.2 (CH]), 243.0 (C]O). GC–MS: m/z (%) 218
(Mþ), 149, 121, 99 (100), 91, 59. HRMS (ESI): calcd for C13H18ONaSi:
m/z 241.1025, found: 241.1023.
3076, 2959, 1629, 1588, 1488, 1250 cmꢂ1
.
1H NMR:
d
¼0.21 (s, 6H,
Si(CH3)2), 1.78 (d, 2H, SiCH2, J¼8.1 Hz), 3.34 (dd, 1H,
CH2]CHCHaCHb, J¼15.3, 7.0 Hz), 3.51 (dd, 1H, CH2]CHCHaCHb,
J¼15.3, 7.0 Hz), 4.7–5.1 (m, 4H), 5.5–5.8 (m, 2H), 6.3–6.5 (m, 2H,
2ꢀCH Ph), 6.8–7.2 (m, 3H, 3ꢀCH Ph), 7.2–7.3 (m, 2ꢀCH Bt), 7.6–7.7
4.3.5. Allyl(but-2-enoyl)dimethylsilane 1f
(m, 1H, CH Bt), 7.9–8.0 (m, 1H, 1CH Bt). 13C NMR:
d
¼ꢂ3.2 (Si(CH3)2),
Yield: 10 mg (30%). Yellow oil. Rf¼0.20 (EP/AcOEt 98:2). IR
22.3 (CH2), 41.5 (CH2), 94.8 (Cq), 113.4 (CH Bt), 114.2 (CH2]), 119.3
(CH2]),119.4 (CH Bt),120.5 (2ꢀCH Ph),122.9 (CH Ph),123.1 (CH Bt),
127.1 (CH Bt), 129.0 (2ꢀCH Ph), 132.6 (CH]), 133.3 (Cq Bt), 133.5
(CH]), 146.0 (Cq Bt), 158.1 (Cq Ph). HRMS (ESI): calcd for
C21H25N3ONaSi: m/z 386.1665, found: 386.1674.
(film): 2986, 1633, 1265, 738 cmꢂ1
.
1H NMR:
d
¼0.18 (s, 6H,
Si(CH3)2), 1.67 (d, 2H, SiCH2, J¼8.0 Hz), 1.88 (dd, 3H, CH3, J¼6.8,
1.4 Hz), 4.7–4.9 (m, 2H), 5.5–5.8 (m, 1H), 6.07 (d, 1H, ]CHCO,
Jtrans¼15.9 Hz), 6.6–6.8 (m, 1H). 13C NMR:
¼ꢂ3.7 (Si(CH3)2), 21.4
d
(SiCH2), 21.5 (CH3), 113.8 (CH2]), 133.5 (CH]), 133.7 (CH]), 144.2
(CH]), 236.2 (C]O).
4.4.3. Allyl(1-(benzotriazol-1-yl)-1-phenoxyhex-5-enyl)-
dimethylsilane 4h
4.3.6. Benzoyl(dimethyl)vinylsilane 1i
Yield: 0.66 g (58%). Oil. TLC: Rf¼0.26 (EP/AcOEt 97:3). IR (film):
Yield: 46 mg (60%). Yellow oil. Rf¼0.20 (EP/AcOEt 99:1). IR
3075, 2957,1629, 1595, 1250, 842, 694 cmꢂ1. 1H NMR:
d¼0.20 (s, 6H,
(film): 3053, 2966, 1629, 1615, 1577, 1446, 1250 cmꢂ1
.
1H NMR:
Si(CH3)2), 1.1–1.6 (m, 2H), 1.81 (d, 2H, SiCH2, J¼8.1 Hz), 2.0–2.2 (m,
2H), 2.8–3.1 (m, 2H), 4.8–5.0 (m, 4H), 5.5–5.9 (m, 2H), 6.51 (d, 2H,
2ꢀCH Ph, J¼8.5 Hz), 6.9–7.1 (m, 3H, 3ꢀCH Ph), 7.2–7.3 (m, 2ꢀCH Bt),
d
¼0.44 (s, 6H, Si(CH3)2), 5.89 (dd, 1H,¼CHaHb, Jtrans¼20.0 Hz,
Jgem¼3.5 Hz), 6.14 (dd, 1H, ]CHaHb, Jcis¼14.6 Hz, Jgem¼3.5 Hz), 6.39
(dd, 1H, SiCH], Jtrans¼20.0 Hz, Jcis¼14.6 Hz), 7.4–8.1 (m, 5H Ph). 13
C
7.6–7.7 (m, 1H, CH Bt), 8.0–8.2 (m, 1H, CH Bt). 13C NMR:
(Si(CH3)2), 22.3 (CH2), 22.8 (CH2), 33.5 (CH2), 36.8 (CH2), 95.9 (Cq),
d
¼ꢂ3.2
NMR:
d
¼ꢂ3.8 (Si(CH3)2), 127.4 (2ꢀCH Ph), 128.3 (2ꢀCH Ph), 132.5

5532
C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
113.3 (CH Bt), 114.3 (CH2]), 115.2 (CH2]), 119.6 (CH Bt), 120.5
(2ꢀCH Ph), 123.4 (CH Ph), 123.9 (CH Bt), 127.1 (CH Bt), 129.0 (2ꢀCH
Ph), 133.2 (Cq Bt), 133.6 (CH]), 137.3 (CH]), 146.0 (Cq Bt), 155.1 (Cq
Ph). HRMS (ESI): calcd for C23H29N3ONaSi: m/z 414.1978, found:
414.1975.
5.6–5.7 (m, 2H). 13C NMR:
(CH2CO), 114.5 (CH2]), 119.0 (CH2]), 129.8 (CH]), 133.0 (CH]),
244.0 (C]O). GC–MS: m/z (%) 168 (Mþ), 153, 99 (100), 71, 59.
d
¼ꢂ5.0 (Si(CH3)2), 21.3 (CH2Si), 53.8
4.5.3. Allyl(dimethyl)hex-5-enoylsilane 1h
Yield: 100 mg (80%). Oil. TLC: Rf¼0.35 (EP/AcOEt 98:2). IR (film):
4.4.4. (1-(Benzotriazol-1-yl)-1-phenoxyundecyl)(dimethyl)-
vinylsilane 4j
2927, 2855, 1641, 1261 cmꢂ1. 1H NMR:
d
¼0.16 (s, 6H, Si(CH3)2), 1.45–
1.60 (m, 2H, CH2CH2CO), 1.66 (d, 2H, SiCH2, J¼7.8 Hz), 1.94 (m, 2H,
Yield: 0.81 g (60%). Oil. TLC: Rf¼0.39 (EP/AcOEt 97:3). IR (film):
CH2]CH–CH2), 2.53 (t, 2H, CH2CO, J¼7.4 Hz), 4.8–5.0 (m, 4H), 5.5–
2925, 2854, 1592, 1489, 1249, 926 cmꢂ1
.
1H NMR:
d¼0.10 (s, 3H,
5.7 (m, 2H). 13C NMR:
(CH2), 48.4 (CH2), 114.4 (CH2]), 115.2 (CH2]), 133.3 (CH]), 138.4
(CH]), 247.1 (C]O). GC–MS: m/z (%) 196, 115, 99 (100), 97, 81.
d
¼ꢂ5.0 (Si(CH3)2), 21.1 (CH2), 21.3 (CH2), 33.3
SiCH3), 0.19 (s, 3H, SiCH3), 0.78 (t, 3H, CH3, J¼6.3 Hz), 0.9–1.5 (m,
16H), 2.42 (t, 1H, J¼12.1 Hz), 2.59 (t, 1H, J¼10.9 Hz), 5.5–5.7 (m, 1H),
5.8–5.9 (m, 1H), 6.1–6.3 (m, 1H), 6.36 (d, 2H, 2ꢀCH Ph, J¼8.1 Hz),
6.8–7.0 (m, 3H, 3ꢀCH Ph), 7.1–7.3 (m, 2ꢀCH Bt), 7.5–7.6 (m, 1H, CH
4.5.4. Dimethyl(vinyl)undecanoylsilane 1j
Bt), 7.9–8.1 (m, 1H, CH Bt). 13C NMR:
d
¼ꢂ2.8 (SiCH3), ꢂ2.5 (SiCH3),
Yield: 183 mg (94%). Oil. TLC: Rf¼0.25 (EP/AcOEt 98:2). IR (film):
14.1 (CH3), 22.6 (CH2), 23.6 (CH2), 29.0 (CH2), 29.2 (CH2), 29.3 (CH2),
29.4 (CH2), 29.7 (CH2), 31.8 (CH2), 37.8 (CH2), 95.8 (Cq),113.5 (CH Bt),
119.7 (CH Bt), 120.6 (2ꢀCH Ph), 123.4 (CH Ph), 124.0 (CH Bt), 127.1
(CH Bt), 129.0 (2ꢀCH Ph), 133.3 (Cq Bt), 133.5 (CH2]), 136.7 (CH]),
146.2 (Cq Bt), 155.5 (Cq Ph). HRMS (ESI): calcd for C27H39N3ONaSi:
m/z 472.2760, found: 472.2756.
2927, 2855, 1639, 1252 cmꢂ1. 1H NMR:
d
¼0.18 (s, 6H, Si(CH3)2), 0.88
(t, 3H, CH3, J¼6.3 Hz), 1.1–1.4 (m, 14H), 1.50–1.59 (m, 2H,
CH2CH2CO), 2.59 (t, 2H, CH2CO, J¼7.3 Hz), 5.60–6.51 (m, 3H). 13C
NMR:
d
¼ꢂ5.1 (Si(CH3)2), 14.1 (CH3), 22.1 (CH2), 22.8 (CH2), 23.6
(CH2), 29.3 (CH2), 29.4 (CH2), 29.5 (CH2), 30.9 (CH2), 31.8 (CH2), 49.0
(CH2), 134.6 (CH2]), 137.2 (CH]), 246.9 (C]O). GC–MS: m/z (%)
254 (Mþ), 141, 113, 85 (100), 75, 59. HRMS (ESI): calcd for
C15H30ONaSi: m/z 277.1964, found: 277.1958.
4.4.5. (1-(Benzotriazol-1-yl)-1-phenoxybut-3-enyl)-
(dimethyl)vinylsilane 4k
Yield: 0.67 g (65%). White solid, mp 62–64 ꢁC. TLC: Rf¼0.33 (EP/
4.5.5. But-3-enoyl(dimethyl)vinylsilane 1k
AcOEt 97:3). IR (film): 3054, 2950, 1588, 1488, 1252 cmꢂ1. 1H NMR:
Yield: 15 mg (35%). Oil. TLC: Rf¼0.4 (EP/AcOEt 99:1). IR (film):
d
¼0.26 (s, 3H, SiCH3), 0.28 (s, 3H, SiCH3), 3.28 (dd, 1H,
2925, 2854, 1638, 1249 cmꢂ1. 1H NMR:
d
¼0.28 (s, 6H, Si(CH3)2), 3.36
CH2]CHCHaCHb, J¼15.2, 7.3 Hz), 3.43 (dd, 1H, CH2]CHCHaCHb,
J¼15.2, 7.3 Hz), 4.9–5.0 (m, 2H), 5.6–5.8 (m, 2H), 5.9–6.3 (m, 2H),
6.45 (d, 2H, 2ꢀCH Ph, J¼8.3 Hz), 6.9–7.1 (m, 3H, 3ꢀCH Ph), 7.3–7.4
(m, 2ꢀCH Bt), 7.65–7.71 (m, 1H, CH Bt), 7.0–8.1 (m, 1H, CH Bt). 13C
(d, 2H, CH2CO, J¼7.0 Hz), 4.9–5.0 (m, 2H), 5.7–5.9 (m, 2H), 6.0–6.2
(m, 2H). 13C NMR:
119.2 (CH2]), 134.5 (CH]), 137.3 (CH]), 245.2 (C]O).
d
¼ꢂ5.0 (Si(CH3)2), 53.6 (CH2), 115.6 (CH2]),
NMR:
d¼ꢂ2.8 (SiCH3), ꢂ2.5 (SiCH3), 42.1 (CH2), 94.7 (Cq), 113.6 (CH
4.6. Ring-closing metathesis experiments (Table 2)
Bt), 119.4 (CH2]), 119.6 (CH Bt), 120.6 (2ꢀCH Ph), 123.5 (CH Ph),
124.0 (CH Bt), 127.1 (CH Bt), 129.0 (2ꢀCH Ph), 131.6 (CH]), 133.1 (Cq
Bt), 133.8 (CH2]), 136.4 (CH]), 146.0 (Cq Bt), 155.4 (Cq Ph). HRMS
(ESI): calcd for C20H23N3ONaSi: m/z 372.1508, found: 372.1512.
4.6.1. 2-(Benzotriazol-1-yl)-1,1-dimethyl-2-phenoxy-1,2,3,6-
tetrahydrosiline 6g
To compound 4g (200 mg, 0.55 mmol) was added 10% solution
of Grubbs II catalyst (51 mg, 0.06 mmol) in CH2Cl2 (18 mL). The
reaction mixture was refluxed for 5 h until the disappearance of the
starting material (TLC, eluent: EP/AcOEt 96:4) and then it was fil-
tered through silica gel. After evaporation of solvent, the residue
was purified by silica gel column chromatography (eluent: EP/
AcOEt 97:3) affording the compound 6g (151 mg, yield: 82%).
White solid, mp 75–81 ꢁC. TLC: Rf¼0.21 (EP/AcOEt 97:3). IR
4.5. Hydrolysis of intermediates 4 into (acyl)(dimethyl)-
allylsilanes or acyl(dimethyl)-vinylsilanes 1 (Scheme 2:
method B)
To a solution of compound 4 (0.80 mmol) in acetone (2 mL) was
added a solution of anhydrous FeCl3 (0.48 mmol, 0.6 equiv) in ac-
etone (2 mL). The reaction mixture was stirred (45–75 min) at room
temperature until the disappearance of the starting material
(checked by TLC, eluent: EP/AcOEt 96:4). At the end of the reaction,
the resulting mixture was filtered on silica gel to remove FeCl3.
After evaporation of the solvent, the residue was purified by silica
gel column chromatography (eluent: EP/CH2Cl2 85:15) affording
the corresponding acylsilane 1 (Table 1).
(film): 3018, 2901, 1650, 1594, 1490, 1253 cmꢂ1. 1H NMR:
d¼0.02 (s,
3H, SiCH3), 0.14 (s, 3H, SiCH3),1.51 (dd, 2H, SiCH2, J¼3.4,1.5 Hz), 3.19
(dd, 2H, CH2C(OPh)(Bt), J¼2.6, 1.5 Hz), 5.3–5.5 (m, 1H, CH]), 5.7–
5.9 (m, 1H, CH]), 6.35 (d, 2H, 2ꢀCH Ph, J¼8.6 Hz), 6.9–7.1 (m, 3H,
3ꢀCH Ph), 7.2–7.4 (m, 2H, 2ꢀCH Bt), 7.85 (d, 1H, CH Bt, J¼8.5 Hz),
8.07 (d,1H, CH Bt, J¼8.1 Hz). 13C NMR:
¼ꢂ2.7 (SiCH3), ꢂ2.4 (SiCH3),
d
15.1 (SiCH2), 36.0 (CH2), 92.1 (Cq), 113.0 (CH Bt), 120.0 (CH Bt), 120.8
(2ꢀCH Ph), 123.5 (CH]), 123.8 (CH Ph), 124.2 (CH Bt), 127.2 (CH Bt),
127.5 (CH]), 129.1 (2ꢀCH Ph), 132.3 (Cq Bt), 146.7 (Cq Bt), 155.6 (Cq
Ph). HRMS (ESI): calcd for C19H22N3OSi: m/z 336.1532, found:
336.1539.
4.5.1. Allyl(dimethyl)undecanoylsilane 1e
Yield: 190 mg (95%). Oil. TLC: Rf¼0.28 (EP/AcOEt 98:2). IR (film):
2925, 2854, 1644, 1250 cmꢂ1. 1H NMR:
d
¼0.21 (s, 6H, Si(CH3)2), 0.89
(t, 3H, CH3, J¼5.9 Hz), 1.1–1.4 (m, 14H), 1.50–1.61 (m, 2H), 1.71 (d,
2H, SiCH2, J¼8.1 Hz), 2.58 (t, 2H, CH2CO, J¼7.2 Hz), 4.9–5.0 (m, 2H),
4.6.2. 2-(Benzotriazol-1-yl)-1,1-dimethyl-2-phenoxy-2,3-dihydro-
1H-silol 6k
5.6–5.8 (m, 1H). 13C NMR:
d
¼ꢂ5.3 (Si(CH3)2), 14.0 (CH3), 21.1 (CH2),
21.9 (CH2), 22.6 (CH2), 22.9 (CH2), 25.4 (CH2), 29.2 (CH2), 29.4 (CH2),
29.5 (CH2), 31.8 (CH2), 49.1 (CH2CO), 114.1 (CH2]), 133.9 (CH]),
246.6 (C]O). GC–MS: m/z (%) 155, 142, 127, 99 (100), 75, 59. HRMS
(ESI): calcd for C16H32ONaSi: m/z 291.2120, found: 291.2112.
To compound 4k (192.0 mg, 0.550 mmol) was added 2% solution
of Grubbs II catalyst (9.3 mg, 0.011 mmol) in toluene (18 mL). The
reaction mixture was heated at 80 ꢁC. Grubbs II catalyst (9.3 mg,
0.011 mmol) was added after each 3 h (seven portions for w24 h)
until the disappearance of the starting material (TLC, eluent: EP/
AcOEt 96:4). The resulting mixture was then filtered through silica
gel. After evaporation of solvent, the residue was purified by silica
gel column chromatography (eluent: EP/AcOEt 97:3) affording
compound 6k (141 mg, yield: 80%).
4.5.2. Allyl(but-3-enoyl)dimethylsilane 1g
Yield: 8 mg (25%). Oil. TLC: Rf¼0.42 (EP/AcOEt 99:1). IR (film):
2919, 2855, 1643, 1251 cmꢂ1. 1H NMR:
(d, 2H, SiCH2, J¼8.9 Hz), 3.36 (dt, 2H, J¼6.9, 1.3 Hz), 4.9–5.2 (m, 4H),
d
¼0.23 (s, 6H, Si(CH3)2), 1.72

C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
5533
White solid, mp 77–80 ꢁC. TLC: Rf¼0.25 (EP/AcOEt 97:3). IR
4.9.1. 1,4-Bis[(1-(benzotriazol-1-yl)-1-phenoxyundecyl)-
(film): 3019, 2962, 2400, 1591, 1490, 1261, 1216 cmꢂ1
d
.
1H NMR:
dimethylsilyl]but-2-ene 9
¼0.00 (s, 3H, SiCH3), 0.62 (s, 3H, SiCH3), 3.51 (ddd, 1H,
Oil. IR (film): 2926, 2855, 1590, 1489, 1251, 1216 cmꢂ1. HRMS
CHaCHbCH], J¼18.3, 2.8, 1.9 Hz), 4.05 (dt, 1H, CHaCHbCH], J¼18.3,
2.8 Hz), 6.19 (dt, 1H, CH], J¼11.1, 1.9 Hz), 6.56 (d, 2H, 2ꢀCH Ph,
J¼8.0 Hz), 6.83 (dt, 1H, CH], J¼11.1, 2.8 Hz), 6.97 (t, 1H, CH Ph,
J¼8.0 Hz), 7.13 (t, 2H, 2ꢀCH Ph, J¼8.0 Hz), 7.3–7.5 (m, 2H, 2ꢀCH Bt),
7.80 (d, 1H, CH Bt, J¼7.4 Hz), 8.12 (d, 1H, CH Bt, J¼7.4 Hz). 13C NMR:
(ESI): calcd for C54H79N6O2Si2: m/z 899.5803, found: 899.5817.
Major stereomer: TLC: Rf¼0.27 (EP/AcOEt 96:4). 1H NMR:
¼0.0
d
(s, 6H, Si(CH3)2), 0.8–0.9 (m, 3H, CH3), 1.1–1.7 (m, 18H, 9ꢀCH2), 2.4–
2.8 (m, 2H), 5.1–5.2 (m, 1H), 6.4–6.5 (m, 2H, 2ꢀCH Ph), 6.8–7.1 (m,
3H, 3ꢀCH Ph), 7.2–7.3 (m, 2H, 2ꢀCH Bt), 7.5–7.6 (m, 1H, CH Bt), 8.0–
d
¼1.0 (Si(CH3)2), 41.2 (CH2), 94.8 (Cq), 112.1 (CH Bt), 119.7 (2ꢀCH
8.1 (m, 1H, CH Bt). 13C NMR:
d
¼ꢂ3.0 (Si(CH3)2), 14.1 (CH3), 20.8
Ph), 120.8 (CH Bt), 123.0 (CH Ph), 124.1 (CH Bt), 127.3 (CH Bt), 128.6
(CH]), 129.6 (2ꢀCH Ph), 133.2 (Cq Bt), 146.8 (CH]), 147.0 (Cq Bt),
155.0 (Cq Ph). HRMS (ESI): calcd for C18H19N3ONaSi: m/z 344.1195,
found: 344.1190.
(CH2), 22.6 (CH2), 23.6 (CH2), 29.0 (CH2), 29.2 (CH2), 29.3 (CH2), 29.4
(CH2), 29.7 (CH2), 31.8 (CH2), 37.3 (CH2), 96.2 (Cq), 113.4 (CH Bt),
119.6 (CH Bt), 120.6 (2ꢀCH Ph), 123.4 (CH Ph), 123.9 (CH Bt), 124.7
(CH]), 127.1 (CH Bt), 129.1 (2ꢀCH Ph), 133.4 (Cq Bt), 146.1 (Cq Bt),
155.2 (Cq Ph).
Minor stereomer (selected data): Rf¼0.20 (EP/AcOEt 96:4). 1H
NMR:
d
¼5.3–5.4 (m, 1H). 13C NMR:
¼ꢂ2.8 (Si(CH3)2), 123.4 (CH]).
d
4.7. Hydrolysis of benzotriazole 6g (Scheme 5)
To a solution of benzotriazole 6g (60 mg, 0.18 mmol) in toluene
(2 mL) was added ytterbium triflate dihydrate (217 mg, 0.36 mmol).
The reaction mixture was refluxed for almost 4 h until the disap-
pearance of the starting material (TLC, eluent: EP/AcOEt 97:3). After
hydrolysis with saturated aqueous NaHCO3 (5 mL), the aqueous
phase was extracted with ether (3ꢀ5 mL). The combined organic
phases were dried over MgSO4, filtered off and concentrated under
reduced pressure. The residue was purified by silica gel column
chromatography (eluent: EP/AcOEt 97:3) affording the dihydrosi-
line 7 (14 mg, yield: 36%).
4.10. Conversion of compound 9 into bis(acylsilane) 10
Treatment of compound 9 (151 mg, 0.17 mmol) by anhydrous
FeCl3 in acetone according to the procedure above described (4.5)
gave bis(acyl)silane 10 (41 mg, 95%) as a mixture (60:40) of
stereomers.
4.10.1. But-2-ene-1,4-diylbis[dimethyl(undecanoyl)silane] 10
Oil. TLC: Rf¼0.25 (EP/AcOEt 98:2). IR (film): 2927, 2855, 1639,
1467, 1258, 1053 cmꢂ1. HRMS (ESI): calcd for C30H60NaO2Si2: m/z
277.1964, found: 277.1958.
4.7.1. 1(-Benzotriazol-1-yl)-(1,1-dimethyl)-1,6-dihydrosiline 7
Oil. TLC: Rf¼0.35 (EP/AcOEt 97:3). IR (film): 2926, 1592, 1452,
Major stereomer: 1H NMR:
d
¼0.18 (s, 6H, Si(CH3)2), 0.87 (t, 3H,
CH3, J¼6.9 Hz),1.1–1.7 (m,18H, 9ꢀCH2), 2.5–2.7 (m, 2H), 5.2–5.3 (m,
1H). 13C NMR:
1260, 1041, 757 cmꢂ1. 1H NMR:
d
¼0.32 (s, 6H, Si(CH3)2), 1.70 (d, 2H,
d¼ꢂ5.3 (Si(CH3)2), 14.1 (CH3), 14.8 (CH2), 19.5 (CH2),
SiCH2, J¼4.6 Hz), 5.9–6.1 (m, 2H, 2ꢀCH]), 6.95 (d, 1H, CH],
22.1 (CH2), 22.7 (CH2), 29.3 (CH2), 29.4 (CH2), 29.6 (CH2), 31.0 (CH2),
J¼6.3 Hz), 7.2–7.5 (m, 2H, 2ꢀCH Bt), 7.75 (d, 1H, CH Bt, J¼8.4 Hz),
8.02 (d, 1H, CH Bt, J¼8.3 Hz). 13C NMR:
¼ꢂ1.7 (Si(CH3)2), 15.9
d
31.8 (CH2), 49.2 (CH2CO), 124.1 (CH]), 247.6 (C]O).
Minor stereomer (selected data): 1H NMR:
d¼5.3–5.4 (m, 2H).
(SiCH2), 111.9 (CH Bt), 120.3 (CH Bt), 123.5 (CH]), 124.2 (CH Bt),
127.4 (CH]CBt), 127.6 (CH Bt), 129.3 (CH]), 131.4 (Cq Bt), 138.9 (Cq),
146.4 (Cq Bt). GC–MS: m/z (%) 241 (Mþ), 212 (100), 198, 119, 95.
13C NMR:
d¼ꢂ4.8 (Si(CH3)2), 122.1 (CH]).
4.11. Cross metathesis of the dithianyl derivative 3f
(Scheme 4)
4.8. Hydrogenation of compound 6g (Scheme 5)
The same procedure as for compound 6g (Table 2) was applied
to compound 3f (31 mg, 0.12 mmol, refluxing CH2Cl2, 5 h) affording
the compound 5 (49 mg, 85%) as a mixture (w50:50) of stereomers
non-separable over silica gel column chromatography (eluent: EP/
AcOEt 99:1).
A suspension of 6g (100 mg, 0.29 mmol) and 10% Pd/C catalyst
(10 mg) in methanol (6 mL) was hydrogenated under 1 atm of hy-
drogen. The reaction mixture was stirred for 12 h at room tem-
perature, and then was filtered through Celite. Evaporation of the
solvent under reduced pressure afforded the benzotriazole 8 as
a pure compound (96 mg, yield: 98%).
4.11.1. 1-[(2-Allyl-1,3-dithian-2-yl)(dimethyl)silyl]-4-[2-
(allyldimethylsilyl)-1,3-dithian-2-yl]but-2-ene 5
4.8.1. 2-(Benzotriazol-1-yl)-1,1-dimethyl-2-phenoxysilinane 8
Oil. TLC: Rf¼0.21 (EP/AcOEt 97:3). IR (film): 3072, 2930, 1594,
Oil. TLC: Rf¼0.35 (EP/AcOEt 99:1). IR (film): 3074, 2905, 1629,
1422, 1248, 1050, 839 cmꢂ1 1H NMR (mixture of stereomers):
.
1489, 1250 cmꢂ1
.
1H NMR:
d
¼0.12 (s, 3H, SiCH3), 0.20 (s, 3H,
d
¼0.19 (s, 6H, Si(CH3)2), 0.23 (s, 6H, Si(CH3)2), 1.80 (m, 4H,
SiCH3), 0.7–1.8 (br m, 6H), 2.62 (t, 1H, J¼14.5 Hz), 2.81 (dd, 1H,
J¼21.8, 14.5 Hz), 6.39 (d, 2H, 2ꢀCH Ph, J¼8.0 Hz), 6.8–7.1 (m, 3H,
3ꢀCH Ph), 7.2–7.4 (m, 2H, 2ꢀCH Bt), 7.85 (d, 1H, CH Bt, J¼5.8 Hz),
2ꢀSiCH2), 1.9–2.2 (m, 4H), 2.4–2.6 (m, 4H), 3.0–3.2 (m, 8H), 4.8–5.0
(m, 2H), 5.1–5.3 (m, 2H), 5.5–5.6 (m, 1H), 5.7–5.9 (m, 2H), 5.9–6.1
(m, 1H). 13C NMR (mixture of stereomers):
d¼ꢂ5.5 (SiCH3), ꢂ5.1
8.0–8.2 (m, 1H, CH Bt). 13C NMR:
d
¼ꢂ3.6 (SiCH3), ꢂ1.6 (SiCH3),
(SiCH3), 12.2 (SiCH2), 21.0 (SiCH2), 23.1 (2ꢀCH2), 23.3 (2ꢀCH2), 25.0
(CH2), 25.5 (CH2), 37.1 (CH2), 37.8 (2ꢀCq), 41.5 (CH2), 113.9 (CH2]),
116.8 (CH2]), 126.0 (CH]), 126.5 (CH]), 134.4 (CH]), 136.5
(CH]).
13.8 (CH2), 23.3 (CH2), 24.2 (CH2), 36.8 (CH2), 94.2 (Cq), 113.4 (CH
Bt), 115.7 (CH Bt), 119.6 (2ꢀCH Ph), 123.2 (CH Ph), 124.5 (CH Bt),
127.3 (CH Bt), 129.5 (2ꢀCH Ph), 132.3 (Cq Bt), 146.5 (Cq Bt), 155.9
(Cq Ph). HRMS (ESI): calcd for C19H23N3ONaSi: m/z 360.1508,
found: 360.1518.
Acknowledgements
4.9. Cross metathesis of compound 4e (Scheme 6)
We are grateful to CNRS and University of Reims for supporting
´
this work and to Region Champagne-Ardenne for a Ph.D. grant
The same procedure as for compound 4g was applied affording
(C.H.). The authors thank Dr. D. Harakat for HRMS analyses and they
acknowledge a referee for relevant remarks regarding metathesis
reactions.
compound
stereomers.
9 (261 mg, yield: 52%) as a mixture (60:40) of

5534
C. Hammaecher et al. / Tetrahedron 65 (2009) 5527–5534
5. Hammaecher, C.; Portella, C. Chem. Commun. 2008, 5833–5835.
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