Synthesis of 1-silabicyclo[4.4.0]dec-5-en-4-ones: A model of the A and B rings of 10-silatestosterone

Article abstract of DOI:10.1002/ejoc.200800305

1-Silabicyclo[4.4.0]dec-5-en-4-ones, a novel type of organosilicon compound, have been prepared from 2-methylidene-1-(3-oxopropyl)-1- silacyclohexanes by an ene reaction as the key transformation. Various routes to the starting aldehydes from 3-halopropyl, allyl, or 3-(4-methoxybenzyloxy) propylsilanes have been investigated. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800305

FULL PAPER
DOI: 10.1002/ejoc.200800305
Synthesis of 1-Silabicyclo[4.4.0]dec-5-en-4-ones: A Model of the A and B Rings
of 10-Silatestosterone
Silvia Díez-González,[a][‡] Renée Paugam,[a] and Luis Blanco*[a]
Keywords: Silicon / Synthesis design / Ene reaction / Diastereoselectivity / Fused-ring systems
1-Silabicyclo[4.4.0]dec-5-en-4-ones, a novel type of organo-
silicon compound, have been prepared from 2-methylidene-
1-(3-oxopropyl)-1-silacyclohexanes by an ene reaction as the
key transformation. Various routes to the starting aldehydes
from 3-halopropyl, allyl, or 3-(4-methoxybenzyloxy)propyl-
silanes have been investigated.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
Siladrugs[1] are of interest due to the unique properties
of the silicon atom.[2] Among them, silasteroids have been
the subject of few studies. Two groups have reported inde-
pendently the synthesis of 6,6-dimethyl-6-silasteroids.[3,4]
This sila-substitution was performed to block the 6-hydrox-
ylation pathway in order to prevent the aromatization of
the B ring. Various compounds like dimethylsilaestradiol
(1) and the analogue 2 of mestranol, a potent oral contra-
ceptive agent, or some 5,6-secosilasteroids like 3 have been
screened for estrogenic, anti-estrogenic, and post-coital ac-
tivity (Figure 1). No significant estrogenic or anti-estrogenic
activity was observed using doses 100–1000 times that of
an estradiol standard. Compounds 1 and 3 exhibited post-
coital activity in rats, but only at 10 mgkg–1. The binding
affinity of silaestradiol 1 towards the estrogen receptor pro-
tein of the rat uterus was found to be 0.3% that of estradiol.
Figure 1. Some examples of 6-silasteroids and related compounds
biologically tested.
In these studies, two methyl groups were introduced onto two main groups of new compounds could be envisioned,
the silicon atom to avoid the presence of Si–H bonds, a the 10- and 13-silasteroids. Of the 10-silasteroids, we con-
priori unstable in a biological environment. Therefore, the sidered 10-silatestosterone (4b) an interesting target. One of
absence of estrogenicity could be due to steric or electronic the metabolic pathways of testosterone (4a) gives undesir-
effects.
able estradiol (Scheme 1)[5] and aromatization of the A ring
We thought that sila-substitution of the steroid skeleton of the sila analogue 4b should be prevented by the presence
could lead to new compounds with interesting pharmaco- of a silicon atom.[3,6] Theoretical[7] and experimental esti-
dynamic and/or pharmacokinetic properties if the replace- mates[8] of the strength of the π bond of the C=Si double
ment was carried out without the introduction of other new bond (ca. 39 kcalmol–1) show that it is less stable than the
substituents to the parent steroid. Substitution of a quater- C=C double bond (65 kcalmol–1). Therefore, the formation
nary carbon atom by a silicon atom fulfils this requirement of a C=Si double bond should need more energy than the
and should yield stable compounds in biological media. So, formation of an analogous C=C double bond.
1-Silabicyclo[4.4.0]dec-5-en-4-ones of type 24, models of
the A and B rings of silatestosterone (4b), were our first
goal because the paucity of reported methods for the prepa-
ration of bicyclo[n.m.0]alkanic compounds with a ring junc-
tion silicon atom is evident.[9–11] The formation of 3-methyl-
idene-4-silacyclohexanols by the ene reaction from isopro-
penylsilanes bearing a 3-oxopropyl chain on the silicon
atom has been reported.[12] We envisaged a synthesis of
[a] Laboratoire de Synthèse Organique et Méthodologie, Institut
de Chimie Moléculaire et des Matériaux d’Orsay, UMR 8182
(Associée au CNRS),
Bât. 420, Univ. Paris-Sud, 91405 Orsay, France
Fax: +33-1-69156278
E-mail: lublanco@icmo.u-psud.fr
[‡] Present address: Institute of Chemical Research of Catalonia
(ICIQ),
Av. Països Catalans, 16, 43007 Tarragona, Spain
3298
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Synthesis of 1-Silabicyclo[4.4.0]dec-5-en-4-ones
Scheme 1. Metabolic transformation of testosterone into estradiol.
1-silabicyclo[4.4.0]dec-6-en-4-ols 22 starting from 2-methyl-
idene-1-silacyclohexanes 11 and subsequent transformation
to our goal (Scheme 2).
Scheme 4. Preparation of 3-halopropylsilanes 7. Reagents and con-
ditions: i) for 6a and 6c, [H2PtCl6], cyclohexane, reflux, 14 h; for
6b and 6d, [H2PtCl6], without solvent; ii) THF, addition of 5 at
10 °C, then 3 h at 20 °C; iii) Grignard reagent (1 equiv.), THF,
65 °C, 1.4 h.
Oxidation of the chloropropylsilanes 7a,b at 105 °C un-
der modified Kornblum conditions[16] gave the expected al-
dehydes 11a,b in 50 and 36% yields, respectively
(Scheme 5). The aldehyde 11a was obtained in a slightly
better yield (54%) by reaction at 20 °C of the bromopro-
pylsilane 7c with DMSO in the presence of silver tetrafluo-
roborate and subsequent treatment with triethylamine.[17]
The very low yield observed for the preparation of bro-
mopropylsilane 6c makes this reaction sequence via the bro-
minated derivative 7c less efficient than the one via chloro-
propylsilane 7a.
Scheme 2. Retrosynthesis of 1-silabicyclo[4.4.0]dec-5-en-4-ones 24.
Results and Discussion
Among the various approaches to the required 2-methyl-
idene-1-(3-oxopropyl)-1-silacyclohexanes 11 that have been
tested, the intramolecular hydrosilylation of hex-5-ynyl-
silanes was successful.[13] But the shortest way to 2-methyl-
idene-1-silacyclohexanes would be a priori from polyhalo-
or polyethoxysilanes and 2,6-dibromohex-1-ene 5 using an
organodimetallic derivative or Barbier-type conditions.[14]
The synthesis of aldehydes 11 was attempted via the corre-
sponding 3-halopropyl derivatives 7 or the allylsilanes 10
(Scheme 3).
Scheme 5. Preparation of 3-oxopropylsilanes 11 from halopropyl-
silanes.
Scheme 3. Retrosynthesis of 2-methylidene-1-silacyclohexanes 11.
Reactions of the commercially available methyl- and
phenyltrichlorosilane with the Grignard reagent obtained
from 2,6-dibromohexene (5), as described above, have al-
lowed the synthesis of the 1-chloro-2-methylidenesilacy-
Synthesis of (3-Oxopropyl)silanes 11
The reactions at 65 °C of dichloro(3-halopropyl)silanes clohexanes 8a and 8b in 33 and 45% yields, respectively,
6a–c with the Grignard reagent prepared from 2,6-dibro- after purification by distillation.[14] Initially, the introduc-
mohexene (5) in THF at 10 °C gave the 2-methylidenesilacy- tion of a masked 3-oxopropyl chain was attempted. Alde-
clohexanes 7a–c in moderate yields after purification by sil- hyde 11a was not detected after reaction in diethyl ether of
ica gel chromatography.[14] The 3-halopropylsilanes 6 were the chlorosilane 8a with the Grignard reagent prepared
generally isolated by distillation after reaction of the com- from 3-bromopropanal dimethyl acetal[18] followed by acid
mercially available methyl- and phenyldichlorosilane with treatment (oxalic acid/silica gel[19]). Reaction of 8a with the
allyl bromide and chloride in the presence of [H2PtCl6].[15] lithiated derivative[20] of N-allylpyrrolidine and subsequent
(3-Bromopropyl)phenylsilane (6d) was probably formed un- acid hydrolysis (3  aqueous HCl) gave the aldehyde 11a in
der these reaction conditions but polymerization occurred 12% yield only. Much better results were obtained by indi-
during the distillation under low pressure (Scheme 4).
rect formation via the 1-allyl-2-methylidenesilacyclohexanes
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S. Díez-González, R. Paugam, L. Blanco
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10a,b synthesized by addition of a solution of allylmagne- ered, in a minor amount, alcohol 13 as a result of the hy-
sium chloride in THF to the chlorosilanes 8a,b and purifi- droboration of the exocyclic double bond, which could be
cation by silica gel chromatography (Scheme 6).
easily separated from alcohol 12a by silica gel chromatog-
raphy. No improvements in yield or the 12a/13 ratio were
observed by modifying the reaction time or the temperature
of the hydroboration step or by decreasing the temperature
of the oxidative step. The presence of such a byproduct was
not observed in the case of the phenylated silane 10b
(Scheme 8).
Scheme 6. Preparation of allylsilanes 10. Reagents and conditions:
i) THF, addition of 5 at 10 °C, then 3 h at 20 °C; ii) Grignard rea-
gent (1 equiv.), THF, 65 °C, 1.4 h; iii) Grignard reagent (1 equiv.),
THF, addition at 0 °C then 14 h at 20 °C; iv) Mg, THF, slow ad-
dition of reactants then 2 h at 60 °C; v) NaBF4, tetraglyme, 70 °C.
The methylated silane 10a was also prepared in similar
yields from the commercially available allyldichloromethyl-
silane or the corresponding difluorosilane 9[21] and dibro-
mohexene 5 under Barbier-type conditions. With these di-
halosilanes, lower yields of silane 10a were obtained with
the preformed Grignard reagent (5% from the dichloro-
silane and 20% from compound 9).
Treatment of the allylsilanes 10a,b with 9-borabicy-
clononane (9-BBN) at 20 °C for 2 h and subsequent oxi-
dation with pyridinium chlorochromate (PCC) on Ce-
lite®[22] in refluxing dichloromethane gave the expected al-
dehydes 11a and 11b in 30 and 55% yields, respectively
(Scheme 7).
Scheme 8. Formation of (3-hydroxypropyl)silanes 12 from the allyl-
silanes 10.
This difference in reactivity led us to study this transfor-
mation further. Reaction of 1-hexyl-1-methyl-2-methyl-
idenesilacyclohexane (14) under the aforementioned condi-
tions afforded the corresponding 2-(hydroxymethyl)sila-
cyclohexane 15 in 3% yield. Treatment of an equimolar
mixture of the hexylsilane 14 and allyltrimethylsilane under
the same conditions led only to the formation of (3-hy-
droxypropyl)trimethylsilane (16; Scheme 9). Therefore, the
unusually high reactivity of the exocyclic double bond of
1-allyl-2-methylidenesilacyclohexane 10a seems due to the
presence of the allyl group.
Scheme 7. Preparation of 3-oxopropylsilanes 11 from allylsilanes.
This synthesis of the phenylated aldehyde 11b from tri-
chlorophenylsilane was more efficient (overall yield 20%)
than the approach via chloropropylsilane 7b (overall yield
3.5%). The preparation of the methylated aldehyde 11a via
chloropropylsilane 7a was more efficient than all the meth-
ods studied (overall yield 23.5%).
Scheme 9. Hydroboration of vinylsilane 14 and allyltrimethylsilane.
Oxidation of the (3-hydroxypropyl)silanes 12a,b with the
Comments on the Hydroboration of 1-Allyl-2-methylidene-
silacyclohexanes 10
When the hydroboration reactions of allylsilanes 10a and Dess–Martin reagent[24] gave the expected aldehydes 11a,b
10b with 9-BBN were followed by oxidative cleavage with a in good yields[25] (Scheme 10). However, allylsilanes 10a
basic solution of hydrogen peroxide at 50 °C,[23] the and 10b were converted into the corresponding aldehydes
alcohols 12a and 12b were isolated in moderate yields (50– 11 in better overall yields when the intermediate boranes
65%). The reaction of the methylated silane 10a also deliv- were treated with PCC (see above).
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Synthesis of 1-Silabicyclo[4.4.0]dec-5-en-4-ones
without solvent, a mixture of oligomers was obtained.
Compound 18a was not detected after treatment of the di-
ethoxysilane 21 with the Grignard reagent obtained from
dibromohexene 5. However, reaction of an equimolar
amount of the diethoxysilane 21 with the dilithiated reagent
prepared from 5 and lithium gave the methylidenesila-
cyclohexane 18a in too low a yield (15%) for synthetic pur-
poses (Scheme 12).
Scheme 10. Preparation of 3-oxopropylsilanes 11 from alcohols 12.
Other Syntheses of the (3-Hydroxypropyl)silanes 12
The 3-hydroxypropylsilanes 12a,b were also synthesized
by reaction of the chloromethylidenesilacyclohexanes 8a
and 8b with the Grignard reagent prepared from 3-bromo-
1-(4-methoxybenzyloxy)propane (17) and subsequent treat-
ment of the ethers 18a,b with 2,3-dichloro-5,6-dicyano-
quinone (DDQ)[26] (Scheme 11).
Scheme 11. Preparation of (3-hydroxypropyl)silanes 12 from the
bromopropanol derivative 17. Reagents and conditions: i) Mg,
THF, 60 °C; ii) 8a or 8b (0.9 equiv.), THF, 20 °C, 1.4 h; iii) DDQ
(1.3 equiv.), DCM/H2O, 20 °C, 0.5 h.
Scheme 12. Retrosynthesis of (3-benzyloxypropyl)silane 18a and
preparation from a diethoxysilane. Reagents and conditions: i)
[H2PtCl6], DCM, 20 °C, 14 h; ii) [H2PtCl6], air, cyclohexane, reflux,
3 h; iii) a) 5 and Li, Et2O, –5 °C, 14 h; b) 21 and dilithiated reagent
In this approach, (3-oxopropyl)silanes 11a and 11b were
prepared via the protected 3-hydroxypropylsilanes 18 in 10
and 16% overall yields, respectively. These yields are lower
than those obtained via chloropropylsilane 7a for the meth- (1 equiv.), 20 °C, 10 h.
ylated product and via allylsilane 10b for the phenylated
product.
A more convergent approach to 18a was envisaged from
Synthesis of the Silabicyclodecenones 24
dibromohexene 5 and dichlorosilane 20 bearing a (4-meth-
oxybenzyloxy)propyl chain. Allyl 4-methoxybenzyl ether
(19) reacted with dichloromethylsilane in the presence of
Speier’s catalyst,[27] but the expected silane 20 could not be
isolated. The 1H NMR spectrum of the crude reaction mix-
ture showed the absence of ethylenic protons and of protons
characteristic of the methoxybenzyloxy group (Scheme 12).
Benzyl ethers can be easily cleaved by trimethylsilyl iodide[28]
or bromide.[29] In our case, a similar intramolecular reaction
of the chlorosilane 20 could explain its subsequent transfor-
mation. When the allyl ether 19 was treated with dichlo-
romethylsilane in the presence of Wilkinson’s catalyst in re-
fluxing benzene, 4-methoxybenzyl chloride was the only
product isolated by distillation. Moreover, treatment in
THF at 20 °C of the unconcentrated crude reaction mixture
of this hydrosilylation with the Grignard reagent prepared
from dibromohexene 5 gave the methylidenesilacyclohexane
18a, but in less than 5% yield. When the temperature of the
last step was increased to reflux temperature, the expected
compound 18a was not detected. Alternatively, hydro-
silylation of the allyl ether 19 with diethoxymethylsilane, in
refluxing cyclohexane in the presence of Speier’s catalyst
and air[30] satisfactorily gave the expected silane 21, which
was unstable over silica gel. No reaction occurred at room
Treatment of the 3-oxopropylsilanes 11a and 11b with an
excess of dichloromethylaluminium in dichloromethane at
–78 °C led to the preparation of the bicyclic compounds 22
in excellent yields.[12] Gratifyingly, only one diastereoisomer
was formed under these reaction conditions (Scheme 13).
Scheme 13. Preparation of silabicyclodec-6-en-4-ols 22 by the ene
reaction and NOE effects.
1
The H NMR spectra of these alcohols are very similar
temperature with Speier’s catalyst, even in the absence of for the silabicyclic core protons and show a broad singlet
solvent. In the presence of Wilkinson’s catalyst[31] at 80 °C at around 4.07 ppm. This signal, attributed to the proton
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S. Díez-González, R. Paugam, L. Blanco
FULL PAPER
linked to the carbon bearing the hydroxy group, indicates was observed with 22a under these conditions. This lack of
that this proton is in an equatorial position. Moreover, a reactivity may be related to the axial position of the hy-
NOESY experiment performed on the alcohol 22a showed droxy group.
cross-peaks between the protons of the methyl on the sili-
However, the α,β-ethylenic ketones 24 were easily ob-
con atom and one of the protons on C-3 and one of those tained by a two-step method.[36] Oxidation of the alcohols
on C-5. Therefore it can be deduced that these stereoselec- 22a,b with Jones’ reagent in acetone gave the β,γ-ethylenic
tive ene reactions delivered the silabicyclodecenols 22 with ketones 23a,b in excellent yields. Migration of the carbon–
a trans relationship between the hydroxy group and the carbon double bond under basic conditions followed by
methyl on the silicon atom. Minimized molecular modeling neutralization afforded the expected ketones 24a and 24b,
geometries[32] of cis- and trans-silabicyclodecenol 22a which were isolated in medium-to-good yields after silica
showed a chair conformation for the silacyclohexanol part gel chromatography (Scheme 14).
of the two isomers (Figure 2). The trans isomer is the only
one that agrees with the observed NMR features.
Scheme 14. Preparation of silabicyclodec-5-en-4-ones 24. Reagents
and conditions: i) CrO3/H2SO4, acetone, 20 °C, 10 min; ii) KOH
(cat.), MeOH, 50–60 °C, 50 min, then neutralization with acetic
acid.
Finally, comparison of the chemical shifts of the ethyl-
Figure 2. MM+-minimized geometries of the cis and trans isomers
22a.
enic protons of the silabicyclo[4.4.0]decenones 24a and 24b
and that of the α-hydrogen of 4,4-dimethyl-4-silacyclohex-
2-en-1-one (25)[37] with those of the carbon analogues
26a,[38] 26b,[39] and 27[40] shows the silicon atom exerts a
similar downfield effect on these protons (Figure 4 and
Table 1).
Such trans diastereoisomers should be obtained by trans-
fer of the allylic proton of the starting aldehyde 11, which
is on the same face as the oxopropyl chain. Examination of
a Dreiding molecular model shows this proton is the only
one accessible to undergo an ene reaction. Interactions of
the oxygen and carbon atoms of the carbonyl group with
this allylic proton and the methylene group carbon atom,
respectively, lead to a trans diastereoisomer (Figure 3). The
same type of trans diastereoisomer has been proposed for a
product resulting from a molybdenum(II)-complex-cata-
lyzed ene cyclization of a carbon analogue of the sila-
cyclohexanes 11.[33]
Figure 4. Selected cycloalkenones for NMR comparison.
Table 1. NMR chemical shifts of the vinylic proton α to the car-
bonyl group.
Silacyclohexenones
Carbon analogues
Compound δ [ppm]
Compound
δ [ppm]
24a
24b
25
6.33[a]
6.54[a]
6.47[b]
26a
26b
27
5.70[a]
6.10[a]
5.71[b]
Figure 3. Dreiding model of the ene reaction with aldehydes 11.
[a] In CDCl3. [b] In CCl4.
Initially the preparation of the α,β-ethylenic ketones 24
was attempted by Oppenauer oxidation of homoallylic
alcohols 22 using a large excess of tris(isopropoxy)alumi-
num in the presence of cyclohexanone as cosolvent.[34]
From the methylated silane 22a, it was not possible to de-
tect the expected ketone 24a among the various compounds
Conclusions
We have established various synthetic routes to 1-sila-
resulting from the aldol condensation of cyclohexanone. bicyclo[4.4.0]dec-5-en-4-ones 24, a new class of compounds
With the phenylated alcohol 22b, the ketone 24b was iso- with a silicon atom at the ring junction. The silabicyclic
lated in 9% yield after silica gel chromatography. A catalytic core was built by a diastereoselective ene reaction from a 1-
method with the dichlorotris(triphenylphosphane)ruthe- (3-oxopropyl)-2-methylidene-1-silacyclohexane. The meth-
nium complex in the presence of potassium carbonate in ylated compound 24a was prepared in five steps from
acetone allowed the Oppenauer oxidation of various ste- dichloro(3-chloropropyl)methylsilane in 16% overall yield.
roidic homoallylic alcohols with the hydroxy group in the The phenylated analogue 24b was synthesized in seven steps
equatorial position to α,β-ethylenic ketones.[35] No reaction from trichlorophenylsilane in 15% yield via an allylated in-
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Synthesis of 1-Silabicyclo[4.4.0]dec-5-en-4-ones
2.9 Hz, 1 H, C=CH2), 5.78 (ddt, J = 9.3, 17.2, 8.2 Hz, 1 H,
CH=CH2), 7.30–7.49 (m, 3 H, m- and p-HAr), 7.49–7.56 (m, 2 H,
o-HAr) ppm. 13C NMR (62.9 MHz, CDCl3): δ = 11.1 (C-6), 20.3
(Si-CH2Allyl), 24.1 (C-5), 30.6 (C-4), 39.8 (C-3), 113.8 (CH=CH2),
124.2 (C=CH2), 127.7 (m-CHAr), 129.1 (p-CHAr), 133.9
(CH=CH2), 134.4 (o-CHAr), 134.9 (CAr), 148.7 (C-2) ppm. LRMS:
m/z (%) = 228 (8) [M]+, 188 (19), 187 (100), 159 (27), 145 (12), 131
termediate. The silabicyclodecenone 24a is a model of the
A and B rings of 10-silatestosterone. Our results concerning
the silasteroid will be published in due course.
Experimental Section
(12), 109 (34), 107 (42), 105 (75), 81 (12), 79 (12), 53 (11). IR: ν =
˜
General: All reactions were performed under argon using oven-
dried glassware. All the commercially available silanes 6a–e, 6g, and
6h were used without further purification. Sodium tetrafluoro-
borate and hexachloroplatinic acid were kept in a desiccator filled
with P2O5. THF was distilled prior to use over the radical anion
of benzophenone. Cyclohexane was filtered through basic alumina
prior to use. Column chromatography was performed on silica gel
SDS (70–200 µm).
3069 (ν=CH), 3048 (ν=CH), 2918, 1630 (νC=C), 1428 (νSi–Ar), 1111
(δSi–Ar), 893 (δ=CH), 699 cm–1. HRMS: calcd. for C14H20Si [M]+
228.1334; found 228.1336.
1-Methyl-2-methylidene-1-(3-oxopropyl)-1-silacyclohexane (11a)
From the (3-Chloropropyl)silane 7a: A mixture of chloropropyl-
silane 7a (0.107 g, 0.453 mmol), NaHCO3 (91.5 mg, 1.0 mmol),
NaI (195 mg, 1.3 mmol), and DMSO (3 mL) was heated at 105 °C
for 2 h. After cooling, water was added and the organic products
were extracted with diethyl ether. After separation, the aqueous
phase was extracted twice with diethyl ether. The combined organic
phases were washed with water, dried with Na2SO4, and concen-
trated under reduced pressure. Silica gel column chromatography
(pentane/Et2O, 9:1) allowed the isolation of the starting material
7a (33.5 mg, conversion: 73.5%) and the (3-oxopropyl)silane 11a
(35.3 mg, 50%) as colorless oils.
NMR spectra were recorded with a Bruker AC 200, AC 250, or
DRX 400 spectrometer at room temperature. Chemical shifts (δ)
are reported in ppm with respect to tetramethylsilane; a solvent
signal (CDCl3) was used as the internal reference (CHCl3: 7.27;
CDCl3: 77.0 ppm). Certain signals were assigned on the basis of
COSY, HSQC, HMBC, DEPT, or TOCSY experiments. IR spectra
were recorded with a Perkin–Elmer FT-IR Spectrum One instru-
ment with neat samples on NaCl plates. Mass spectra were re-
corded using the electron ionization method (70 eV) with a Nermag
R10–10 instrument coupled to an OKI DP125 chromatographer
(low resolution) or with a Finnigan MAT 95 S instrument (high
resolution). Elemental analyses were performed by the Microana-
lyse Service of the Institut de Chimie des Substances Naturelles at
Gif-sur-Yvette (ICSN).
From the (3-Bromopropyl)silane 7c: A solution of (bromopropyl)-
silane 7c (0.103 g, 0.42 mmol) in DMSO (1 mL) was added to a
mixture of silver tetrafluoroborate (0.108 g, 0.55 mmol) and
DMSO (0.5 mL) and the reaction mixture was stirred at 20 °C for
14 h. After addition of triethylamine (0.15 mL, 1.07 mmol) the re-
action mixture was stirred 15 min and water and diethyl ether were
added. The separated aqueous phase was extracted twice with di-
ethyl ether. The combined organic phases were washed with brine,
dried with Na2SO4, and concentrated under reduced pressure.
Silica gel column chromatography (pentane/Et2O, 8:2) allowed the
isolation of the starting material 7c (27 mg, conversion: 71%) and
the (3-oxopropyl)silane 11a (30.4 mg, 54%) as colorless oils.
The syntheses and/or spectroscopic data of 2,6-dibromohexene (5),
dihalosilanes 6a–c and 9, and methylidenesilacyclohexanes 7a–c,
8a,b, and 10a have already been reported.[14] 3-Bromo-1-(4-meth-
oxybenzyloxy)propane (17)[41] was prepared by a three-step se-
quence from propane-1,3-diol via 3-(4-methoxybenzyloxy)propan-
1-ol.[42] The hydroxy group was replaced by a bromine atom by
treatment of the corresponding mesylate (MsCl, NEt3, DCM, 0 °C,
2 h) with LiBr in N-methylpyrrolidinone at 20 °C for 3 d (82% yield
from the alcohol).
From the (3-Hydroxypropyl)silane 12a: Dess–Martin reagent
(0.19 g, 0.44 mmol) was added to a solution of (hydroxypropyl)-
silane 12a (49.2 mg, 0.27 mmol) in pyridine (6.5 mL) and dichloro-
methane (1 mL) maintained at 0 °C. The reaction mixture was
stirred at 20 °C for 1.4 h and diethyl ether was added. The organic
phase was washed, successively, with a saturated aqueous sodium
thiosulfate solution, a saturated aqueous sodium hydrogen carbon-
ate solution, and water. The organic phase was dried with Na2SO4,
concentrated under low pressure, and the (3-oxopropyl)silane 11a
(43.6 mg, 89%) was isolated as a colorless oil after silica gel column
chromatography (pentane/Et2O, 9:1).
1-Allyl-1-methyl-2-methylidene-1-silacyclohexane (10b): A 0.65 
solution of allylmagnesium chloride in THF (2.8 mL, 1.8 mmol)
was added dropwise to 1-chloro-1-methyl-2-methylidene-1-sila-
cyclohexane (8a) (0.29 g, 1.8 mmol) maintained at 0 °C. The reac-
tion mixture was stirred at 20 °C for 14 h and a saturated NH4Cl
aqueous solution was added. The organic product was extracted
with diethyl ether and, after separation, the aqueous phase was
extracted twice with diethyl ether. The combined organic phases
were washed with water, dried with Na2SO4, and concentrated
under reduced pressure. The crude product was purified by silica
gel column chromatography (pentane) to afford the allylmethylsila-
cyclohexane 10a (0.18 g, 60%) as a colorless oil.[14]
From the Allylsilane 10a: A 0.5  solution of 9-BBN in THF
(3.8 mL, 1.9 mmol) was added dropwise to allylsilane 10a (0.32 g,
1.9 mmol). After stirring for 3 h at 20 °C, the reaction solution was
transferred through a cannula into a suspension of a 50:50 mixture
of PCC and Celite® (7.4 g, 17.1 mmol) in dichloromethane
(30 mL). The reaction mixture was heated at reflux for 2 h and
was filtered, after cooling, through a silica gel pad (EtOAc). After
concentration under low pressure silica gel column chromatography
(pentane/Et2O, 8:2) afforded the starting material 10a (37.4 mg,
conversion: 88%) and the (3-oxopropyl)silane 11a (90.1 mg, 30%)
1-Allyl-2-methylidene-1-phenyl-1-silacyclohexane (10b): Following
the same procedure as above, 1-choro-2-methylidene-1-phenyl-1-
silacyclohexane (8b) (0.70 g, 3.14 mmol) and a 0.65  solution of
allylmagnesium chloride in THF (4.85 mL, 3.15 mmol) afforded,
after silica gel column chromatography (pentane), 10b (0.57 g,
1
79%) as a colorless oil. Rf (pentane) = 0.48. H NMR (250 MHz,
CDCl3): δ = 0.90 (ddd, J = 4.6, 10.1, 14.6 Hz, 1 H, 6-H), 1.14 (ddd, as colorless oils. Rf (pentane/Et2O, 4:1)
J = 3.8, 7.4, 14.6 Hz, 1 H, 6Ј-H), 1.40–1.57 (m, 1 H, 4-H), 1.57– (250 MHz, CDCl3): δ = 0.11 (s, 3 H, SiCH3), 0.65 (ddd, J = 4.6,
=
0.48. 1H NMR
1.82 (m, 2 H, 4’-H, 5-H), 1.82–2.02 (m, 5’-H) and 1.93 (d, J = 10.2, 14.6 Hz, 1 H, 6-H), 0.80–1.10 (m, CH2CH2CHO) and 0.90
8.2 Hz, CH2CH=CH2) (3 H), 2.21–2.54 (m, 2 H, 3-H, 3’-H), 4.86 (ddd, J = 4.6, 7.5, 14.6 Hz, 6Ј-H) (3 H), 1.33–1.55 (m, 1 H, 4-H),
(d, J = 9.3 Hz, 1 H, CH=CH2 cis), 4.88 (d, J = 17.2 Hz, 1 H, 1.55–1.77 (m, 2 H, 4’-H, 5-H), 1.77–1.89 (m, 1 H, 5’-H), 2.21–2.43
CH=CH2 trans), 5.28 (d, J = 2.9 Hz, 1 H, C=CH2), 5.66 (d, J =
(m, 2 H, 3-H, 3’-H), 2.46–2.72 (m, 2 H, CH2-CHO), 5.14 (d, J =
Eur. J. Org. Chem. 2008, 3298–3307
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3303

S. Díez-González, R. Paugam, L. Blanco
FULL PAPER
3.2 Hz, 1 H, C=CH2), 5.50 (d, J = 3.2 Hz, 1 H, C=CH2), 9.76 (t,
H, 4-H), 1.48–1.62 (m, 4’-H) and 1.60 (quint, J = 6.5 Hz,
CH2CH2OH) (3 H), 1.62–1.73 (m, 1 H, 5-H), 1.73–1.86 (m, 1 H,
J = 1.4 Hz, 1 H, CHO) ppm. 13C NMR (62.9 MHz, CDCl3): δ =
–5.6 (SiCH3), 4.5 (CH2CH2CHO), 13.3 (C-6), 24.3 (C-5), 30.8 (C- 5’-H), 2.33–2.46 (m, 2 H, 3-H), 3.62 (t, J = 6.5 Hz, 2 H, CH2OH),
4), 38.3 (CH2CHO), 39.7 (C-3), 122.4 (C=CH2), 153.6 (C-2), 202.9 5.14 (d, J = 3.5 Hz, 1 H, C=CH2), 5.48 (d, J = 3.5 Hz, 1 H,
(CHO) ppm. LRMS: m/z (%) = 182 (2) [M]+, 167 (10), 154 (15),
126 (21), 125 (23), 113 (15), 112 (28), 111 (23), 101 (100), 99 (97),
C=CH2) ppm. 13C NMR (62.9 MHz, CDCl3): δ = –5.6 (SiCH3),
8.4 (CH2CH2CH2OH), 13.4 (C-6), 24.4 (C-5), 26.9 (CH2CH2OH),
97 (47), 95 (14), 85 (30), 83 (10), 71 (20), 61 (15), 59 (23), 55 (17), 30.9 (C-4), 39.8 (C-3), 65.5 (CH2OH), 121.6 (C=CH2), 151.6 (C-
53 (10), 45 (43), 43 (42). IR: ν = 3040 (ν=CH), 2917, 2852, 2714
2) ppm. LRMS: m/z (%) = 184 (1) [M]+, 169 (7), 141 (12), 127 (17),
˜
(νOC–H), 1725 (νC=O), 1630 (νC=C), 1446, 1408, 1252 (δSi–CH3), 1177,
921, 894 (δ=CH), 797 cm–1. HRMS: calcd. for C10H18OSi [M]+
182.1126; found 182.1124.
125 (16), 109 (10), 102 (11), 101 (100), 99 (24), 97 (28), 87 (13), 75
(26), 74 (36), 61 (35), 59 (25), 45 (12), 43 (12). IR: ν = 3328 (νOH),
˜
3039 (ν=CH), 2915, 1631 (νC=C), 1437, 1248 (δSi–CH3), 1052 (νC–O),
918, 892 (δ=CH), 866, 791 cm–1. HRMS: calcd. for C10H20OSi
[M]+ 184.1283; found 184.1282.
2-Methylidene-1-(3-oxopropyl)-1-phenyl-1-silacyclohexane
(11b):
Following the same procedure as above for the synthesis of alde-
hyde 11a from allylsilane 10a, addition of 9-BBN to 1-allyl-2-meth-
ylidene-1-phenyl-1-silacyclohexane (8b) (0.52 g, 2.28 mmol) fol-
lowed by oxidation of the resulting borane with PCC afforded, af-
ter silica gel column chromatography (pentane/Et2O, 4:1), 11b
1-(3-Hydroxypropyl)-2-methylidene-1-phenyl-1-silacyclohexane
(12b): Following the same procedure as above for the synthesis of
alcohol 12a from silane 18a, the reaction of DDQ with 18b (0.46 g,
1.26 mmol) afforded, after silica gel column chromatography (pen-
tane/Et2O, 4:1), 12b (0.22 g, 71%) as a colorless oil. Rf (pentane/
1
(0.31 g, 55%) as a colorless oil. Rf (pentane/Et2O, 1:1) = 0.65. H
1
NMR (200 MHz, CDCl3): δ = 0.83 (ddd, J = 4.5, 10.3, 14.6 Hz, 1
H, 6-H), 1.07–1.26 (m, CH2CH2CHO) and 1.22 (ddd, J = 4.5, 7.5,
Et2O, 1:1) = 0.23. H NMR (400 MHz, CDCl3): δ = 0.87 (ddd, J
= 4.6, 10.7, 12.5 Hz, 6-H) and 0.90–1.00 (m, CH2CH2CH2OH) (3
14.6 Hz, 6Ј-H) (3 H), 1.44–1.57 (m, 1 H, 4-H), 1.62–1.77 (m, 2 H, H), 1.21 (ddd, J = 4.6, 7.0, 12.5 Hz, 1 H, 6Ј-H), 1.46–1.57 (m, 1 H,
4’-H, 5-H), 1.86–2.00 (m, 1 H, 5’-H), 2.30–2.40 (m, 1 H, 3-H), 4-H), 1.61–1.80 (m, CH2CH2OH) and 1.65–1.77 (m, 4’-H, 5-H) (4
2.40–2.51 (m, 3 H, 3’-H, CH2CHO), 5.21 (d, J = 2.9 Hz, 1 H, H), 1.92–2.03 (m, 1 H, 5’-H), 2.32–2.55 (m, 2 H, 3-H, 3’-H), 3.60
C=CH2), 5.61 (d, J = 2.9 Hz, 1 H, C=CH2), 7.23–7.37 (m, 3 H, (t, J = 7.0 Hz, 2 H, CH2OH), 5.28 (d, J = 3.0 Hz, 1 H, C=CH2),
m- and p-HAr), 7.40–7.54 (m, 2 H, o-HAr), 9.66 (t, J = 1.5 Hz,
5.65 (d, J = 3.0 Hz, 1 H, C=CH2), 7.31–7.46 (m, 3 H, m- and p-
H
1
H, CHO) ppm. 13C NMR (100 MHz, CDCl3):
δ
=
3.8
Ar), 7.46–7.62 (m, 2 H, o-HAr) ppm. 13C NMR (62.9 MHz,
(CH2CH2CHO), 11.4 (C-6), 24.1 (C-5), 30.5 (C-4), 38.2 CDCl3): δ = 8.1 (C-6), 11.5 (CH2CH2CH2OH), 24.2 (C-5), 26.9
(CH2CHO), 39.7 (C-3), 124.3 (C=CH2), 128.0 (m-CHAr), 129.4 (p- (CH2CH2OH), 30.7 (C-4), 39.9 (C-3), 65.5 (CH2OH), 123.9
CHAr), 134.3 (o-CHAr), 134.4 (CAr), 148.4 (C-2), 202.6
(CHO) ppm. LRMS: m/z (%) = 244 (3) [M]+, 217 (14), 216 (62),
215 (14), 189 (11), 188 (26), 187 (30), 175 (30), 174 (38), 167 (22),
164 (18), 163 (100), 162 (37), 161 (88), 160 (22), 159 (39), 147 (13),
145 (17), 133 (12), 131 (18), 123 (23), 117 (11), 109 (12), 107 (31),
(C=CH2), 127.8 (m-CHAr), 129.1 (p-CHAr), 134.3 (o-CHAr), 135.5
(CAr), 149.3 (C-2) ppm. LRMS: m/z (%) = 246 (1) [M]+, 187 (7),
168 (7), 164 (17), 163 (100), 159 (14), 145 (7), 136 (30), 123 (23),
109 (11), 107 (17), 105 (28), 92 (11), 91 (7), 80 (10), 78 (8), 44 (24).
IR: ν = 3326 (νOH), 3068 (ν=CH), 3045 (ν=CH), 2918, 1428 (νSi–Ar),
˜
105 (47), 84 (15). IR: ν = 3068 (ν=CH), 3045 (ν=CH), 2918, 2852, 1110 (δSi–Ar), 1054 (νC–O), 923, 892 (δ=CH), 733, 700 cm–1. HRMS:
˜
2717 (νOC–H), 1723 (νC=O), 1428 (νSi–Ar), 1176, 1111 (δSi–Ar), 924,
892 (δ=CH), 737, 701 cm–1. HRMS: calcd. for C15H20OSi [M]+
244.1283; found 224.1284.
calcd. for C15H22OSi [M]+ 246.1440; found 246.1442.
1-[3-(4-Methoxybenzyloxy)propyl]-1-methyl-2-methylidene-1-sila-
cyclohexane (18a)
1-(3-Hydroxypropyl)-1-methyl-2-methylidene-1-silacyclohexane (12a)
From the Diethoxysilane 21: A solution of 2,5-dibromohexene (5)
(1.92 g, 7.9 mmol) in diethyl ether (15 mL) was added dropwise to
a suspension of lithium (0.24 g, 34.3 mmol) in diethyl ether (3 mL)
maintained at –5 °C. The reaction mixture was stirred at –5 °C for
14 h and the resulting organometallic solution was titrated by acid/
base reaction (0.385 , assuming formation of a dilithiated species,
87%). The diethoxysilane 21 (0.826 g, 2.65 mmol) was added to
this solution of organolithiated reagent (6.9 mL, 2.65 mmol). After
10 h at 20 °C, a saturated aqueous ammonium chloride solution
was added and the organic products were extracted three times with
From the Allylsilane 10a: A 0.5  solution of 9-BBN in THF
(2.24 mL, 1.12 mmol) was added dropwise to allylsilane 10a
(0.18 g, 1.12 mmol). After stirring for 3 h at 20 °C, a 3  aqueous
solution of NaOH (0.34 mL, 1.01 mmol) and a 35% aqueous solu-
tion of H2O2 (0.3 mL, 3.36 mmol) were added. The reaction mix-
ture was heated at 50 °C for 1 h and after cooling the organic prod-
ucts were extracted with pentane. The organic phases were dried
with Na2SO4 and concentrated under reduced pressure. Silica gel
column chromatography (pentane/Et2O, 1:1) allowed the isolation
of the starting material 10a (41 mg, conversion: 78%), 12a (80 mg, diethyl ether. The combined organic phases were washed with
50%) and 1-allyl-2-hydroxymethyl-1-methyl-1-silacyclohexane (13)
(15mg, 9.4%) as colorless oils.
water, dried with Na2SO4, and concentrated under reduced pres-
sure. 18a (0.134 g, 15%) was isolated as a colorless oil after silica
gel column chromatography (pentane/Et2O, 9:1).
From the [3-(4-Methoxybenzyloxy)propyl]silane 18a: DDQ (0.149 g,
0.54 mmol) was added to a mixture of 18a (0.124 g, 0.41 mmol),
From the Chlorosilacyclohexane 8a: A solution of 1-chloro-1-
water (0.220 mL), and dichloromethane (4 mL) maintained at 5 °C. methyl-2-methylidene-1-silacyclohexane (8a) (0.22 g, 1.36 mmol) in
After stirring at 20 °C for 0.5 h, a saturated aqueous sodium hydro-
gen carbonate solution was added and the organic products were
extracted with dichloromethane. The combined organic phases
were dried with Na2SO4 and concentrated under reduced pressure.
The (3-hydroxypropyl)silane 12a (52.2 mg, 69%) was isolated as a
THF (1.5 mL) was added dropwise to a 0.56  solution of 3-(4-
methoxybenzyloxy)propylmagnesium bromide in THF (2.7 mL,
1.5 mmol) prepared by reaction for 6 h of 3-bromo-1-(4-methoxy-
benzyloxy)propane (17) with magnesium in THF at 60 °C. After
14 h at 20 °C, a saturated aqueous ammonium chloride solution
was added and the organic products were extracted three times with
colorless oil after silica gel column chromatography (pentane/Et2O,
1
3:1). Rf (pentane/Et2O, 1:1) = 0.28. H NMR (400 MHz, CDCl3): diethyl ether. The combined organic phases were washed with
δ = 0.11 (s, 3 H, SiCH3), 0.50–0.64 (m, 6-H) and 0.53–0.75 (m, water, dried with Na2SO4, and concentrated under reduced pres-
CH2CH2CH2OH), and 0.64–0.70 (m, 6Ј-H) (4 H), 1.32–1.48 (m, 1 sure. The silane 18a (0.205 g, 50%) was isolated as a colorless oil
3304
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3298–3307

Synthesis of 1-Silabicyclo[4.4.0]dec-5-en-4-ones
after silica gel column chromatography (pentane/Et2O, 4:1). Rf
(pentane/Et2O, 1:1) = 0.58. 1H NMR (400 MHz, CDCl3): δ = 0.12
(SiCH2CH2), 55.1 (OCH3), 58.0 (CH3CH2O), 72.4 (OCH2CAr),
72.5 (CH2CH2O), 113.7 (m-CHAr), 129.1 (o-CHAr), 130.7
(s, 3 H, SiCH3), 0.59–0.74 (m, CH2CH2CH2O) and 0.61 (ddd, J = (CArCH2), 159.0 (CArO) ppm. LRMS: m/z (%) = 312 (0.1) [M]+,
4.6, 9.9, 14.4 Hz, 6-H), and 0.76 (ddd, J = 4.6, 7.7, 14.4 Hz, 6Ј-H)
(4 H), 1.39–1.52 (m, 1 H, 4-H), 1.53–1.64 (m, 4’-H) and 1.58–1.71 145 (18), 137 (49), 134 (30), 133 (90), 130 (13), 122 (24), 121 (100),
(m, CH2CH2O), and 1.64–1.76 (m, 5-H) (4 H), 1.76–1.87 (m, 1 H, 105 (21), 98 (11), 89 (23), 77 (26). IR: ν = 2972, 2929, 1613 (νC=C),
267 (13), 266 (69), 265 (39), 237 (21), 235 (35), 224 (10), 207 (12),
˜
5’-H), 2.27–2.44 (m, 2 H, 3-H, 3’-H), 3.45 (t, J = 6.9 Hz, 2 H,
CH2CH2O), 3.82 (s, 3 H, OCH3), 4.47 (s, 2 H, OCH2CAr), 5.13 (d,
1514 (νC=CO), 1249 (δSi–CH3 or νAr–O), 1102 (νC–O), 1038 (νSi–OC),
822 (δ=CH) cm–1. HRMS: calcd. for C16H28O4Si [M]+ 312.1757;
J = 3.5 Hz, 1 H, C=CH2), 5.49 (d, J = 3.5 Hz, 1 H, C=CH2), 6.90 found 312.1770.
(d, J = 8.7 Hz, 2 H, m-HAr), 7.28 (d, J = 8.7 Hz, 2 H, o-HAr) ppm.
1-Methyl-1-silabicyclo[4.4.0]dec-6-en-4-ol (22a): A 1  solution of
MeAlCl2 in hexanes (0.56 mL, 0.56 mmol) was added to a solution
of aldehyde 11a (56 mg, 0.31 mmol) in dichloromethane (2.3 mL)
maintained at –78 °C. The reaction mixture was stirred at –78 °C
for 6 h, then a saturated aqueous sodium hydrogen carbonate solu-
tion was added, and the organic products were extracted three
times with dichloromethane. The combined organic phases were
washed with water, dried with Na2SO4, and concentrated under
reduced pressure. The siladecenol 22a (56 mg, 100%) was isolated
as a colorless oil after filtration through a silica gel pad (pentane/
Et2O, 1:1). Rf (pentane/Et2O, 1:1) = 0.35. 1H NMR (250 MHz,
CDCl3): δ = 0.13 (s, 3 H, SiCH3), 0.50–0.70 (m, 10-H) and 0.58–
0.72 (m, 2-H) (2 H), 0.74–0.95 (m, 10Ј-H) and 0.78–0.93 (m, 2’-H)
(2 H), 1.51–1.72 (m, 9-H) and 1.56–1.78 (m, 3-H) (2 H), 1.85–2.02
(m, 1 H, 9’-H), 2.08–2.27 (m, 3 H, 3’-H, 8-H, 8’-H), 2.34 (ddd, J
= 2.3, 4.0, 13.7 Hz, 1 H, 5-H), 2.60 (ddddd, J = 2.6, 2.6, 2.6, 2.6,
13.7 Hz, 1 H, 5’-H), 4.07 (br. s, 1 H, 4-H), 6.38 (br. t, J = 4.7 Hz,
1 H, 7-H) ppm. 13C NMR (62.9 MHz, CDCl3): δ = –5.6 (SiCH3),
8.0 (C-2), 11.0 (C-10), 21.3 (C-9), 30.1 (C-3), 30.8 (C-8), 44.9 (C-
5), 66.3 (C-4), 134.0 (C-6), 143.2 (C-7) ppm. LRMS: m/z (%) = 182
(31) [M]+, 167 (74), 154 (32), 139 (64), 126 (40), 125 (43), 113 (52),
111 (61), 101 (59), 99 (78), 97 (57), 96 (47), 95 (44), 87 (42), 85
(38), 84 (38), 75 (46), 69 (32), 67 (36), 61 (100), 59 (42), 45 (61), 43
13C NMR (62.9 MHz, CDCl3):
δ
=
–5.6 (SiCH3), 8.8
(CH2CH2CH2O), 13.4 (C-6), 24.0 (CH2CH2O), 24.4 (C-5), 30.9 (C-
4), 39.8 (C-3), 55.2 (OCH3), 72.4 (OCH2CAr), 72.9 (CH2CH2O),
113.7 (m-CHAr), 121.6 (C=CH2), 129.2 (o-CHAr), 130.7 (CArCH2),
151.7 (C-2), 159.0 (CArO) ppm. LRMS: m/z (%) = 304 (32) [M]+,
247 (15), 208 (13), 207 (29), 162 (23), 161 (38), 135 (12), 126 (10),
125 (42), 123 (13), 122 (88), 121 (100), 102 (10), 101 (84), 99 (22),
97 (67), 91 (18), 85 (10), 78 (19), 77 (24), 71 (17), 59 (21), 43 (8).
IR: ν = 3038 (ν=CH), 2915, 2851, 1608 (νC=C), 1513 (νC=CO), 1250
˜
(δSi–CH3 or δAr–O), 1171, 1098 (νC–O), 1036 (νSi–OC), 820
(δ=CH) cm–1. HRMS: calcd. for C18H28O2Si [M]+ 304.1858; found
304.1847.
1-[3-(4-Methoxybenzyloxy)propyl]-2-methylidene-1-phenyl-1-sila-
cyclohexane (18b): Following the same procedure as above for the
synthesis of silane 18a from chlorosilane 8a, reaction of a 0.56 
of 3-(4-methoxybenzyloxy)propylmagnesium bromide in THF
(4.85 mL, 2.72 mmol) with 1-chloro-2-methylidene-1-phenyl-1-sila-
cyclohexane (8b) (0.605 g, 2.72 mmol) afforded 18b (0.60 g, 60%)
as a colorless oil after silica gel column chromatography (pentane/
Et2O, 4:1). Rf (pentane/Et2O, 4:1) = 0.52. 1H NMR (400 MHz,
CDCl3): δ = 0.70–0.98 (m, 4 H, 6-H, CH2CH2CH2O), 1.00–1.25
(m, 1 H, 5-H), 1.32–1.52 (m, 1 H, 5’-H), 1.53–1.62 (m, 3 H, 4-H,
CH2CH2O), 1.62–1.93 (m, 1 H, 4’-H), 2.16–2.43 (m, 2 H, 3-H),
3.54 (t, J = 6.3 Hz, 2 H, CH2CH2O), 3.80 (s, 3 H, OCH3), 4.42 (s,
2 H, OCH2CAr), 5.25 (d, J = 3.4 Hz, 1 H, C=CH2), 5.63 (d, J =
3.4 Hz, 1 H, C=CH2), 6.87 (d, J = 8.6 Hz, 2 H, m-HAr for
CH2C6H4O), 7.23 (d, J = 8.6 Hz, 2 H, o-HAr for CH2C6H4O), 7.30–
7.44 (m, 3 H, m- and p-HAr for PhSi), 7.55–7.64 (m, 2 H, o-HAr
(35). IR: ν = 3400 (νOH), 3040 (ν=CH), 2907, 2852, 1713, 1623
˜
(νC=C), 1429 (δ=CH), 1249 (δSi–CH3), 1124, 1081, 1056, 1018, 916,
880, 832 (δ=CH), 773 cm–1. HRMS: calcd. for C10H18OSi [M]+
182.1126; found 182.1124.
1-Phenyl-1-silabicyclo[4.4.0]dec-6-en-4-ol (22b): Following the same
procedure as above for the synthesis of siladecenol 22a, reaction
of aldehyde 11b (95 mg, 0.31 mmol) with MeAlCl2 afforded the
siladecenol 22b (90 mg, 95%) as a colorless oil after silica gel col-
umn chromatography (pentane/Et2O, 1:1). Rf (pentane/Et2O, 1:1)
for PhSi) ppm. 13C NMR (100 MHz, CDCl3):
(CH2CH2CH2O), 11.4 (C-6), 23.6 and 24.1 (CH2CH2O, C-5), 30.6
(C-4), 39.8 (C-3), 55.0 (OCH3), 72.3 and 72.9 (CH2CH2O, OCH2-
δ = 8.3
1
CAr), 113.6 (m-CHAr for CH2C6H4O), 123.7 (C=CH2), 127.7 (m-
= 0.32. H NMR (400 MHz, CDCl3): δ = 0.73 (ddd, J = 3.6, 13.0,
CHAr for PhSi), 129.1 and 129.2 (o-CHAr for CH2C6H4O, p-CHAr
for PhSi), 130.6 (CArCH2), 134.3 (o-CHAr for PhSi), 135.5 (CArSi),
14.4 Hz, 1 H, 10-H), 0.98 (br. ddd, J = 2.7, 6.7, 14.4 Hz, 10’-H)
and 1.00 (ddd, J = 5.0, 14.8, 14.8 Hz, 2-H), and 1.10 (ddd, J = 4.0,
4.0, 14.8 Hz, 2’-H) (3 H), 1.61 (dddd, J = 1.6, 4.0, 14.1, 14.1 Hz,
3’-H) and 1.69 (ddddd, J = 2.8, 4.6, 10.0, 13.0, 14.0 Hz, 9’-H) (2
H), 1.93 (m, 1 H, 9-H), 2.10–2.33 (m, 3 H, 3’-H, 8-H, 8’-H), 2.43
(ddd, J = 1.8, 3.7, 14.0 Hz, 1 H, 5-H), 2.62 (ddddd, J = 2.0, 2.5,
2.8, 2.8, 13.8 Hz, 1 H, 5’-H), 4.08 (br. s, 1 H, 4-H), 6.56 (br. t, J =
4.2 Hz, 1 H, 7-H), 7.31–7.51 (m, 3 H, m- and p-HAr), 7.51–7.71 (m,
2 H, o-HAr) ppm. 13C NMR (100 MHz, CDCl3): δ = 6.4 (C-2), 11.0
(C-10), 21.0 (C-9), 30.1 (C-3), 30.8 (C-8), 45.1 (C-5), 69.3 (C-4),
128.4 (m-CHAr), 129.7 (p-CHAr), 131.7 (C-6), 134.9 (o-CHAr), 136.4
(CAr), 145.3 (C-7) ppm. LRMS: m/z (%) = 244 (20) [M]+, 216 (26),
198 (11), 189 (20), 188 (30), 187 (29), 175 (26), 174 (19), 167 (28),
166 (58), 161 (26), 149 (19), 139 (28), 138 (82), 131 (24), 125 (34),
151.7 (C-2), 159.0 (CArO) ppm. IR: ν = 3064 (ν=CH), 3043 (ν=CH),
˜
2916, 2852, 1613 (νC=C), 1587, 1513 (νC=CO), 1428, 1302, 1248
(δSi–CH3 or δAr–O), 1172, 1098 (νC–O), 1037 (νSi–OC), 924, 821
(δ=CH) cm–1. HRMS: calcd. for C23H30O2NaSi [M
+
Na]+
389.1907; found 389.1907.
Diethoxy[3-(4-methoxybenzyloxy)propyl]methylsilane (21): Di-
ethoxymethylsilane (0.5 mL, 3.1 mmol) and allyl 4-methoxybenzyl
ether (19)[43] were added to a mixture of [H2PtCl6] (ca. 0.5 mg) in
cyclohexane (2 mL), protected from moisture with a calcium chlo-
ride guard tube. After heating at reflux for 3 h, solvent and impuri-
ties were removed under vacuum (0.1 Torr) to afford 21 (0.70 g,
75%) as a colorless oil. Gas chromatography showed a 96% pure
product. 1H NMR (250 MHz, CDCl3): δ = 0.13 (s, 3 H, SiCH3),
0.58–0.61 (m, 2 H, SiCH2), 1.22 (t, J = 7.1 Hz, 6 H, CH3CH2O),
1.60–1.76 (m, 2 H, SiCH2CH2), 3.43 (t, J = 8.7 Hz, 2 H,
CH2CH2O), 3.77 (q, J = 7.1 Hz, 4 H, CH3CH2O), 3.82 (s, 3 H,
OCH3), 4.44 (s, 2 H, OCH2CAr), 6.89 (d, J = 8.9 Hz, 2 H, m-HAr),
7.27 (d, J = 8.9 Hz, 2 H, o-HAr) ppm. 13C NMR (50.3 MHz,
124 (24), 123 (100), 121 (25), 107 (32), 105 (77), 91 (23). IR: ν =
˜
3400 (νOH), 3040 (ν=CH), 2907, 2850, 1712, 1625 (νC=C), 1427
(νSi–Ar), 1123 (δSi–Ar), 1123, 1082, 1053, 918, 887, 830 (δ=CH),
775 cm–1. HRMS: calcd. for C15H20OSi [M]+ 244.1283; found
244.1276.
1-Methyl-1-silabicyclo[4.4.0]dec-6-en-4-one (23a): A 0.67  aqueous
CDCl3): δ = –5.0 (SiCH3), 10.0 (SiCH2), 18.3 (CH3CH2O), 23.1 solution of Jones’ reagent (0.64 mL, 2.4 mmol) was added to a
Eur. J. Org. Chem. 2008, 3298–3307
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3305

S. Díez-González, R. Paugam, L. Blanco
FULL PAPER
solution of alcohol 22a (0.400 g, 2.2 mmol) in acetone (100 mL)
maintained at 10 °C. After stirring for 10 min at 20 °C, the reaction
mixture was diluted with dichloromethane and washed with water.
The separated aqueous phase was extracted twice with dichloro-
methane. The combined organic phases were dried with Na2SO4
and concentrated under reduced pressure. The siladec-6-enone 23a
(0.396 g, 99%) was isolated as a colorless oil after silica gel column
chromatography (pentane/Et2O, 4:1). Rf (pentane/Et2O, 3:1) = 0.33.
1H NMR (250 MHz, CDCl3): δ = 0.38 (s, 3 H, SiCH3), 0.43 (ddd,
J = 4.0, 14.1, 14.1 Hz, 1 H, 10-H), 0.64–0.78 (m, 10’-H) and 0.65–
0.77 (m, 2-H) (2 H), 0.83 (ddd, J = 3.0, 6.2, 13.9 Hz, 1 H, 2’-H),
1.53–1.67 (m, 1 H, 9-H), 1.72–1.84 (m, 1 H, 9’-H), 1.85–1.98 (m, 1
H, 8-H), 1.98–2.10 (m, 1 H, 8’-H), 2.32–2.47 (m, 2 H, 3-H), 2.83
(d, J = 15.0 Hz, 1 H, 5-H), 3.18 (dd, J = 3.0, 15.0 Hz, 1 H, 5’-H),
6.13 (br. q, J = 3.0 Hz, 1 H, 7-H) ppm. 13C NMR (62.9 MHz,
CDCl3): δ = –5.8 (SiCH3), 9.1 (C-10), 9.8 (C-2), 20.0 (C-9), 29.8
(C-8), 38.4 (C-3), 52.6 (C-5), 131.4 (C-6), 141.6 (C-7), 210.5 (C-
4) ppm. LRMS: m/z (%) = 180 (33) [M]+, 152 (27), 138 (19), 137
(17), 125 (25), 124 (43), 109 (38), 97 (23), 96 (100), 81 (10), 59 (15),
(C-9), 30.4 (C-8), 35.9 (C-3), 38.7 (C-7), 137.9 (C-5), 167.6 (C-6),
202.0 (C-4) ppm. LRMS: m/z (%) = 180 (21) [M]+, 153 (11), 152
(88), 125 (16), 124 (100), 109 (42), 97 (9), 96 (75), 95 (11), 79 (9),
69 (10), 68 (10), 67 (11), 55 (10), 43 (15). IR: ν = 3045 (ν=CH), 3016
˜
(ν=CH), 2924, 2852, 1666 (νC=O), 1590 (νC=C), 1428, 1315, 1252
(δSi–CH3), 1123, 886, 840 (δ=CH), 789, 760 cm–1. HRMS: calcd. for
C10H16OSi [M]+ 180.0970; found 180.0973.
1-Phenyl-1-silabicyclo[4.4.0]dec-5-en-4-one (24b): Following the
same procedure as above for the synthesis of siladec-5-enone 24a,
reaction of alcohol 23b (64 mg, 0.26 mmol) with KOH in methanol
afforded the siladec-5-enone 24b (54 mg, 85%) as a colorless oil
after silica gel column chromatography (pentane/Et2O, 4:1). Rf
(pentane/Et2O, 4:1) = 0.26. 1H NMR (250 MHz, CDCl3): δ = 0.78
(ddd, J = 4.7, 14.5, 14.5 Hz, 1 H, 10-H), 1.11–1.29 (m, 2 H, 2-H,
2’-H), 1.30–1.58 (m, 3 H, 10’-H, 9-H, 9’-H), 1.95–2.04 (m, 1 H, 8-
H), 2.06–2.17 (m, 1 H, 8’-H), 2.41–2.53 (m, 1 H, 7-H), 2.54–2.62
(m, 2 H, 7’-H, 3-H), 2.76 (ddd, J = 5.0, 5.0, 16.0 Hz, 1 H, 3’-H),
6.54 (s, 1 H, 5-H), 7.38–7.53 (m, 3 H, m- and p-HAr), 7.53–7.68 (m,
2 H, o-HAr) ppm. 13C NMR (100 MHz, CDCl3): δ = 9.0 (C-2),
12.6 (C-10), 23.6 (C-9), 30.4 (C-8), 35.8 (C-3), 38.9 (C-7), 128.3 (m-
CHAr), 130.0 (p-CHAr), 133.3 (CAr), 134.5 (o-CHAr), 139.8 (C-5),
165.0 (C-6), 202.3 (C-4) ppm. LRMS: m/z (%) = 242 (35) [M]+, 215
(18), 214 (100), 187 (13), 186 (85), 159 (14), 158 (95), 157 (10), 145
55 (23), 53 (15), 45 (22), 43 (43). IR: ν = 3045 (ν=CH), 2909, 2854,
˜
2251, 1705 (νC=O), 1619 (νC=C), 1429 (δ=CH), 1412, 1252 (δSi–CH3),
1114, 915, 824 (δ=CH) cm–1. HRMS: calcd. for C10H16OSi [M]+
180.0970; found 180.0966.
(9), 144 (10), 131 (12), 130 (25), 129 (8), 107 (10), 105 (33). IR: ν
˜
1-Phenyl-1-silabicyclo[4.4.0]dec-6-en-4-one (23b): Following the
same procedure as above for the synthesis of siladec-6-enone 23a,
reaction of alcohol 22b (21.1 mg, 0.086 mmol) with Jones’ reagent
afforded the siladec-6-enone 23b (20.3 mg, 97%) as a colorless oil
after silica gel column chromatography (pentane/Et2O, 3:1). Rf
(pentane/Et2O, 3:1) = 0.28. 1H NMR (250 MHz, CDCl3): δ = 0.74
(ddd, J = 3.6, 13.9, 13.9 Hz, 1 H, 10-H), 1.03–1.17 (m, 10’-H) and
1.03–1.17 (m, 2-H) (2 H), 1.42 (ddd, J = 3.6, 6.4, 13.9 Hz, 1 H, 2’-
H), 1.67–1.80 (m, 1 H, 9-H), 1.88–2.02 (m, 1 H, 9’-H), 2.11–2.25
(m, 1 H, 8-H), 2.25–2.38 (m, 1 H, 8’-H), 2.47–2.68 (m, 2 H, 3-H),
3.13 (dd, J = 2.5, 16.5 Hz, 1 H, 5-H), 3.40 (ddd, J = 2.5, 6.0,
16.5 Hz, 1 H, 5’-H), 6.54 (br. q, J = 3.4 Hz, 1 H, 7-H), 7.37–7.50
(m, 3 H, m- and p-HAr), 7.59–7.69 (m, 2 H, o-HAr) ppm. 13C NMR
(100 MHz, CDCl3): δ = 9.4 and 9.5 (C-2, C-10), 20.1 (C-9), 30.2
(C-8), 39.0 (C-3), 53.6 (C-5), 128.2 (m-CHAr), 129.7 (p-CHAr),
134.2 (C-6), 134.4 (o-CHAr), 135.0 (CAr), 144.2 (C-7), 211.2 (C-
4) ppm. LRMS: m/z (%) = 242 (100) [M]+, 215 (7), 214 (32), 200
(8), 199 (10), 188 (16), 187 (12), 186 (17), 160 (11), 159 (12), 158
(34), 131 (13), 130 (13), 108 (20), 107 (23), 106 (16), 105 (56), 93
= 3048 (ν=CH), 3056 (ν=CH), 2924, 2853, 1666 (νC=O), 1590 (νC=C),
1428 (νSi–Ar), 1314, 1269, 1120 (δSi–Ar), 885, 768 (δ=CH), 729,
698 cm–1. HRMS: calcd. for C15H18OSi [M]+ 242.1127; found
242.1125. C15H18OSi (242.39): calcd. C 74.33, H 7.49; found C
74.39, H 7.45.
Acknowledgments
S. D.-G. thanks the Education, Research and Universities Depart-
ment of the Basque Government (Spain) for a doctoral fellowship.
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˜
1705 (νC=O), 1618, 1589 (νC=C), 1428 (νSi–Ar), 1265, 1112 (δSi–Ar),
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1-Methyl-1-silabicyclo[4.4.0]dec-5-en-4-one (24a): Seven drops (ca.
20 µL each) of a 10% aqueous KOH solution were added over
50 min to a solution of the siladec-6-enone 23a (0.307 g, 1.7 mmol)
in methanol (4 mL) maintained at 50–60 °C. After cooling, the re-
action mixture was neutralized with acetic acid and taken off with
water and diethyl ether. The separated aqueous phase was extracted
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with water to neutrality, dried with Na2SO4, and concentrated un-
der reduced pressure. The siladec-5-enone 24a (0.208 g, 68%) was
isolated as a colorless oil after silica gel column chromatography
(pentane/Et2O, 4:1). Rf (pentane/Et2O, 3:1) = 0.30. 1H NMR
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1.14–1.30 (m, 1 H, 8-H), 1.44–1.61 (m, 1 H, 9-H), 1.90–2.02 (m, 1
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7’-H), 2.62–2.80 (m, 1 H, 3’-H), 6.33 (s, 1 H, 5-H) ppm. 13C NMR
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Received: March 21, 2008
Published Online: May 20, 2008
Eur. J. Org. Chem. 2008, 3298–3307
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3307