Magnesium-induced regiospecific C-silylation of suitably substituted enoates and dienoates

Article abstract of DOI:10.1016/j.tet.2010.09.001

The β-aryl-β-silyl and β,β-disilyl propionates have been synthesized from cinnamates and β-silyl acrylates by a regiospecific reductive C-silylation using Mg/silyl chloride/DMF system at room temperature. These reductive C-silylation conditions have also been applied to δ-aryl substituted dienoates wherein silylation took place at the δ-position leading to the synthesis of single regioisomeric allylsilanes with very high stereoselectivity.

Full text of DOI:10.1016/j.tet.2010.09.001

Tetrahedron 66 (2010) 8562e8568
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Magnesium-induced regiospecific C-silylation of suitably substituted enoates and
dienoates
*
Pintu K. Kundu, Sunil K. Ghosh
Bio-Organic Division, Bhabha Atomic Research Centre Trombay, Mumbai 400085, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 May 2010
Received in revised form 27 August 2010
Accepted 1 September 2010
Available online 9 September 2010
The
lates by a regiospecific reductive C-silylation using Mg/silyl chloride/DMF system at room temperature.
These reductive C-silylation conditions have also been applied to -aryl substituted dienoates wherein
b-aryleb-silyl and b,b-disilyl propionates have been synthesized from cinnamates and b-silyl acry-
d
silylation took place at the
very high stereoselectivity.
d-position leading to the synthesis of single regioisomeric allylsilanes with
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Regiospecific
Reductive C-silylation
Unsaturated esters
Magnesium
Allyl silane
1. Introduction
used. The choice of Me2PhSi group is due to its convertibility to
the corresponding alcohol under oxidative conditions (Fle-
mingeTamao)29 with complete retention of stereochemistry. Al-
though Me2PhSi group is an equivalent to a hydroxyl group, it is not
the most easily oxidizable group. The proposed mechanism29c
shows that the phenyl group undergoes an ipso-substitution by
first reacting with an electrophile such as bromine or mercuric ac-
etate. It is therefore expected that electron rich aryl ring would make
this ipso-substitution more facile. This has been demonstrated by
converting dimethyl(p-tolyl)silyl30 and (2-methoxyphenyl)dime-
thylsilyl groups31 to a hydroxyl functionality under milder condi-
tions and better yields. But the major hurdle was the preparation of
dimethyl(aryl)silyl lithiums from the corresponding silyl chlorides,
which does not occur32 for electron rich aryl groups. So the popu-
larity of Me2PhSi group remained because of the easy preparation of
Me2PhSiLi33 from the commerciallyavailable silyl chloride and facile
conjugate additions of mono-34 and bis-silylcuprate22,28 reagents
derived from it to unsaturated carbonyl compounds.
The unique properties of silicon1 have led to its wide utilization in
organic chemistry ranging from protecting functional groups2 to
temporary tether3 in general and as masking hydroxyl group,4
to highly controlled and selective organic reactions1,5 in particular.
Asilicongroupisknowntostabilizeeitheranelectrondeficientcentre
such as a carbocation at the
the -position (
-effect)8 with respect to it. These stabilizing effects
play important roles in directing the regioselectivity in various or-
b-position (b
-effect)6,7 or a carbanion at
a
a
ganic reactions, especially in b-silyl carbonyl compounds. Some re-
cent examples include BaeyereVilliger oxidation,9 BamfordeStevens
reaction,10 Beckmann fragmentation,11 Curtius reaction,12 Norrish
type I and II cleavages,13 palladium-catalyzed nucleophilic sub-
stitution,14 Nazarov cyclizations,15 decarboxylation reactions,16 ste-
reospecific 1,2-silyl shifts,17 and cyclobutane18 formation.
Carbonyl compounds having a silyl group at b-position are pop-
ular targets because of their versatile nature19 as stated earlier and
also excellent surrogate for the acetate aldol20 reaction. The avail-
Reductive silylation of a,b-unsaturated carbonyl compounds is
able methods of preparation of
b
-silyl carbonyl compounds include
known to be mediated by metals, notably by lithium,35 ytterbium,36
and magnesium.37 Electrochemical methods38 have also been used,
although, rarely. The outcome of these reactions depended upon
the functionalities attached to the double bond, metal, and the
solvent used in these reactions. Picard et al.37a,b have shown that
hydrosilylation of unsaturated carbonyl compounds,21 silylmetala-
tion of unsaturated carbonyl compounds22,23 and methods based on
the use of various transition metal catalysts.24e27 Amongst these,
silylmetalation of unsaturated carbonyl compounds using dimethyl
(phenyl)silyl lithium (Me2PhSiLi)28 as a source reagent is widely
a,b-unsaturated esters in the presence of Mg and trimethylsilyl
chloride (TMSCl) in hexamethylphosphoric triamide (HMPA) can
produce three different types of products viz. C-silylation at the
* Corresponding author. E-mail address: ghsunil@barc.gov.in (S.K. Ghosh).
b-position with respect to the ester moiety, reductive dimerization
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.001

P.K. Kundu, S.K. Ghosh / Tetrahedron 66 (2010) 8562e8568
8563
or simple saturation of the double bond. The quantum of each
product depended on the functionalities attached to the double
bond. The C-silylation at the -position was the main product
obtained with cinnamic esters. Similar results were obtained when
-aryl
-phosphorylacrylate derivatives37c were subjected under
b
Scheme 1. Reductive silylation of ethyl cinnamate.
b
a
reductive silylation conditions using TMSCl/Mg/DMF system.
Arylidene malonates/aceto acetates/cyanoacetates were not so se-
lective under these conditions and produced in addition to the
C-silylated product, a significant amount of double bond reduced
Table 1
Optimization of conditions for the reductive silylation of ethyl cinnamatea
Entry
Me3SiCl
equiv
Concn of 1a
(M) in DMF
Temperature
(ꢀC)/time (h)
2a:3ab
Yield (%)c
of 2a
product. Reductive trimethylsilylation of
ketones, esters, and nitriles using a Mg anode in an undivided
electrochemical cell38 mainly produced the
-C-silylated products
in moderate yields. While -unsaturated aldehydes and ketones
b-aryl-a,b-unsaturated
1
2
3
4
5
6
7
8
3
6
12
15
20
6
6
6
6
6
0.1
0.1
0.1
0.1
0.1
0.2
0.06
0.05
0.1
0.2
0.2
0.2
0.2
0.2
0/1.5
0/1.5
0/1.5
0/1.5
0/1.5
0/1.5
0/1.5
0/1.5
ꢁ15/1.5
30/0.5
65/0.15
30/0.5
30/1
85:15
91:9
91:9
91:9
91:9
92:8
90:10
89:11
71:19
95:5
91:9
94:6
94:6
93:7
68
75
76
76
76
77
73
72
50
84
79
78d
73e
70f
b
a,b
under these conditions preferred for reductive dimerization39 to
generate bis-(enol silyl) ethers with very high regioselectivity. We
have also recently shown40 that the reductive conditions using Mg/
TMSCl/DMF system on silicon-tethered diacrylic esters or amides
preferred for intramolecular reductive coupling of the two acrylic
units leading to 3,4-bis-silyl substituted adipic acid derivatives with
9
10
11
12
13
14
6
6
6
6
very high selectivity with no C-silylation at the
therefore, became curious to know the outcome of this reductive
dimerization protocol on -dimethyl(aryl)silylacrylates. Which
b-position. We,
b
30/1.5
pathway it would follow, reduction, C-silylation or dimerization?
Herein, we report our successful approach to the reductive C-sily-
a
Unless stated, Mg (12 equiv) metal was used.
Ratio determined by 1H NMR.
Yield of homogeneous material obtained after silica-gel chromatography.
Mg (9 equiv) metal was used.
Mg (6 equiv) metal was used.
Mg (3 equiv) metal was used.
b
c
d
e
f
lation of
b
-dimethyl(aryl)silylacrylates/cinnamates at
b-position
and reductive C-silylation of
d
-phenyldienoate at -position leading
d
to functionalized allylsilanes.
2. Results and discussion
Table 1, entries 12e14) and carried out the silylation reaction of
ethyl cinnamate with 6 equiv of TMSCl in each case at room tem-
Prior to work with b-dimethyl(aryl)silylacrylates, we decided to
perature. The b-silylated product 2a was formed in all cases but
find out suitable conditions for the reductive silylation of ethyl
cinnamate as it is known37b to react in this fashion under Mg/
TMSCl/HMPA system. When ethyl cinnamate 1a was subjected
under our reported40 conditions (reactant concentration 0.1 M in
DMF, 12 equiv each of Mg and TMSCl with respect to ethyl cinna-
mate, at 0 ꢀC), it was gratified to note that the reaction took place
with complete consumption of starting material (Scheme 1). The
crude reaction product indeed showed the formation of ethyl
required longer reaction time. Although, the ratio of silylation to
reduction, i.e., the formation of 2a:3a did not change, significant
drop in the isolated yield of 2a was observed. The best condition is
therefore to add the ethyl cinnamate to a mixture of 6 equiv of
TMSCl, 12 equiv of Mg in DMF (0.2 M) at 30 ꢀC for 0.5 h (Table 1,
entry 10). Under these conditions the C-silylated product 2a was
isolated in 84% yield with the double bond reduction product 3a
now found to be negligible (w5%). The double bond reduction
product 3a was also easily separated from C-silylated product 2a by
column chromatography.
b
-phenyl b-trimethylsilyl propionate 2a associated with a small
amount of double bond reduced product, ethyl dihydrocinnamate
3a (2a:3a¼9/1 as revealed by 1H NMR). No reductive dimerization
product could be detected from the crude product. The C-silylated
product 2a was also isolated in 76% yield. To improve upon the yield
and selectivity, the procedure was then modified by adding ethyl
cinnamate to the mixture of Mg and TMSCl under various condi-
tions as presented in Table 1. As our study aimed to introduce
various silyl groups, optimization of the quantity of silyl chloride
was therefore essential. We began our studies with the use of
3 equiv of TMSCl with respect to ethyl cinnamate at 0 ꢀC (Table 1,
entry 1). Increasing the proportion of TMSCl from 3 equiv to 6 equiv
reduced the formation of the reduction product 3a and the overall
yield was also improved (Table 1, entry 2). Further increase in
TMSCl quantity did not improve the yield of the silylated product 2a
much (Table 1, entries 3e5). Increasing the reactant concentration
did not change the selectivity or the yield while reactions under
dilute conditions produced more double bond reduction product 3a
(Table 1, entries 6e8). When the reaction temperature was lowered,
the selectivity of C-silylation versus double bond reduction
detoriated (Table 1, entry 9) and also the isolated yield of 2a de-
creased significantly. Interestingly, carrying out the reaction at
room temperature (30 ꢀC) increased the reaction rate, the yield of
product 2a and the selectivity of the reaction (Table 1, entry 10).
Further increase in the reaction temperature shortened the re-
action time but yield and selectivity dropped marginally (Table 1,
entry 11). We also varied the quantity of magnesium (9e3 equiv;
As mentioned earlier, suitable substituents on silicon, especially
aryl groups make the silyl group as a masked hydroxyl group. To
generalize the Mg/TMSCl/DMF system for efficient reductive
C-silylation at the b-position of ethyl cinnamates, reductive silyla-
tion with PhMe2SiCl and silyl chlorides, which do not form the
corresponding silyl lithium easily, such as p-TolMe2SiCl, p-Ans-
Me2SiCl, and AllMe2SiCl were pursued. All these silyl groups30,41 are
also known to be the surrogate of the hydroxyl group. The results of
reductive silylation under the optimized conditions are presented
in Table 2. In all cases the b-silylated product was obtained in very
good yield and purity (Table 2, entries 1e6). Even, chlor-
odimethylsilane reacts very cleanly to produce the corresponding
b-silylated product in high yield (Table 2, entry 6). Electron do-
nating substituent at the phenyl ring of the substituted ethyl cin-
namate did not hinder the reaction (Table 2, entries 7 and 8).
We next turned our attention to know the fate of
under these optimized reductive silylation conditions using
Mg/chlorosilane/DMF system at 30 ꢀC. We prepared two
-silyl ac-
b-silyl acrylates
b
rylates 1c and 1d as the substrates following the reported pro-
cedures42 using cobalt carbonyl mediated silylation of ethyl/methyl
acrylate with appropriate dimethyl(aryl)silanes (Scheme 2). When
dimethyl(phenyl)silyl acrylate 1c was subjected under the reductive
silylation conditions using Mg/TMSCl/DMF system, the -disily-
lated product 4a was isolated in good yield (Table 3, entry 1).
b-
b,b

8564
P.K. Kundu, S.K. Ghosh / Tetrahedron 66 (2010) 8562e8568
Table 2
Table 3
Reductive silylation of cinnamates with various silyl chloridesa
Reductive silylation of b
-silyl substituted acrylates with various silyl chloridesa
Entry
1
Acrylate
Silyl chloride
Me3SiCl
Product
Yield (%)b
81
Entry
1
Cinnamate
Silyl chloride
Me3SiCl
Product
Yield (%)b of 2
1c
1a
84
2
3
4
5
6
1c
1d
1d
1d
1d
p-TolMe2SiCl
Me3SiCl
79
70
71
70
70
2
3
4
5
1a
1a
1a
1a
PhMe2SiCl
75
75
80
89
p-TolMe2SiCl
p-AnsMe2SiCl
AllMe2SiCl
PhMe2SiCl
p-TolMe2SiCl
p-AnsMe2SiCl
6
7
1a
1b
Me2SiHCl
Me3SiCl
85
70
7
1d
AllMe2SiCl
72
a
Mg (12 equiv) metal and silyl chloride (6 equiv) were used in all experiments.
Yield of homogeneous material obtained after silica-gel chromatography.
b
8
1b
p-TolMe2SiCl
71
a
Mg (12 equiv) metal and silyl chloride (6 equiv) were used in all experiments.
Yield of homogeneous material obtained after silica-gel chromatography.
b
Scheme 3. Silyl Grignard route to reductive b-C-silylation.
which accepts another electron from Mg to give the anion species,
that is, quenched by the silyl chloride to give the C-silylated
b
Scheme 2. Synthesis of b-silyl substituted acrylates.
product. The former pathway seems to be not operative in the
present case. This was augmented by the following experiments.
When a mixture of TMSCl and Mg metal in DMF was stirred at room
temperature and the supernatant was added to ethyl cinnamate 1a,
no silyl addition product 3a was observed. No reaction also took
place when a DMF solution of ethyl cinnamate was added to the
residual Mg metal. But the desired product 3a was formed when
6 equiv of TMSCl was added to this mixture. Although silyl Grignard
reagents are known to be produced from silyl chlorides having aryl
substitutions, trialkylsilyl chlorides do not form such species under
normal conditions.43 The alternate and most plausible mechanism
for the reductive C-silylation is depicted in Scheme 4. Without
TMSCl, there was no reaction including the double bond reduction.
The role of the silyl chloride was manifold. First, it probably acti-
vates the metal by cleaning the oxide/hydroxide/carbonate coating
from the surface. TMSCl is also known to increased the reduction
potential value of octanoylimidazole from ꢁ2.00 to ꢁ1.04 V versus
SCE44 or acetophenone ꢁ2.34 to ꢁ1.38 V versus SCE.45 It is logically
expected that TMSCl would increased the reduction potential value
of the cinnamate substrate thus accelerates the single electron
transfer from Mg to the substrate. Its presence also increases the
chemoselectivity of the reaction in favor of the C-silylation prod-
ucts over double bond reduction product or dimerization. The re-
ductive C-silylation process was probably accelerated by quenching
Although a trace amount (<5%) of reductive dimerization product
was formed, no double bond reduction could be seen in the crude
reaction product. A similar clean reaction took place for 1c when
TMSCl was replaced by dimethyl(p-tolyl)silyl chloride (Table 3, entry
2). The reductive C-silylationwasthenrepeatedwiththesilylacrylate
methyl ester 1d using various silyl chlorides as presented in Table 3.
The desired b,b-disilylated products 4ceg were formed in moderate
to good yield. Compared to ethyl ester 1c, methyl ester 1d produced
slightly more amount of the reductive dimerization products
(10e15%) as judged from the crude reaction product by 1H NMR af-
fecting the isolated yields of
b,b-disilylated products 4ceg (Table 3,
entries 3e7). Acrylates with a
b-alkyl group viz. ethyl crotonate or
ethyl 5-phenyl-2-pentenoate under the same conditions did not re-
act. After prolonged stirring at room temperature some unidentified
products were formed presumably bycross reactionwith thesolvent,
i.e., DMF under the reaction conditions.
The reductive
b C-silylation of cinnamate can occur by two
pathways. The silyl chloride can react with magnesium metal to
give intermediate silyl Grignard species, which then undergo 1,4-
addition to cinnamate 1a to give the product 3a (Scheme 3). The
other possibility is the single electron transfer from Mg metal to the
cinnamate, activated by silyl chloride, to generate a benzyl radical,

P.K. Kundu, S.K. Ghosh / Tetrahedron 66 (2010) 8562e8568
8565
Scheme 4. Plausible mechanism of reductive b-C-silylation.
the radical anion 5, formed by electron transfer from Mg to the
acrylate 1a, with TMSCl to give the ketene silyl acetal radical 6. One
more electron transfer from Mg to 6 provided the intermediate
triphenyldifluorosilicate48 can cause desilylation to generate aryl
and silyl stabilized carbanion which can be trapped with electro-
philes. As homoenolates are considered equivalent to umpolung of
acrylates, the present methodology is thus amounted to overall
umpolung generation while making the silylated compounds from
the acrylates as well their possible uses. The allylsilanes are known
as useful synthetic intermediates and the additional ester func-
tionality at the terminal of the allysilane would enhance their
utility. The C-silylations described here is electrophilic. Thus, there
is no limitation for the choice of silyl groups, a crucial factor for
anion 7, which was then quenched by silyl chloride to give the
silylated silyl ketene acetal 8. The silyl acetal 8 underwent hydro-
lysis during aqueous work-up conditions and provided the -silyl
b-C-
b
propionate 2a. By this process, TMSCl also protected the reductive
silylation product from further reactions like Claisen condensation
or oligomerizations. The C-silylation took place only with
silyl acrylates and not with -alkyl acrylates. The aryl groups are
known to stabilize the carbanion at the benzylic positions and
b-aryl/
b
nucleophilc silylation reactions. Although
b-silylation using the
a silicon group is also known to stabilize a carbanion
a
to it. As the
silyl chloride like p-TolMe2SiCl, p-AnsMe2SiCl, AllMe2SiCl etc. are
not possible by using the conventional procedure of 1,4 addition
using silylcuprate reagents, it is easily done by using Mg/silyl
chloride/DMF system.
reduction potential of benzyl radical (ꢁ1.45 V vs SCE)46 and
a-silyl
radical (ꢁ1.51 V vs SCE)47 is higher compared to alkyl radicals
(ꢁ2.0 V vs SCE),46 the reductive silylation process was favored with
these two classes of substrates.
We turned our attention to study this reductive silylation on
dienic esters because these substrates can react in different modes
to produce regio-isomeric C-silylated products. When the diene
ester 9a was treated under the optimized reductive silylation
conditions as described for ethyl cinnamate, (Scheme 5) using
TMSCl, the allyl silane 10a was formed without a trace of the other
regioisomer. Moreover, the allyl silane was also formed with high
stereoselectivity where (E)-isomer was found to be the major
product (E/Z¼86/14 by GC) as revealed from the 1H NMR coupling
constant values of the olefinic protons (J¼16 Hz). While changing
the silyl chloride from TMSCl to p-TolMe2SiCl, the corresponding
allyl silane 10b was formed in good yield and also contaminated
with a small amount of the (Z)-isomer (19%). Interestingly, alkyl
substituted dienoate 9b under the same conditions did not provide
the desired allyl silane 10c. Instead, some unidentified oligomeric
products were formed.
4. Experimental
4.1. General methods
DMF was dried over CaH2 followed by storage over 4 Å molec-
ular sieves. Mg turnings were purified by washing with dilute
hydrochloric acid, water followed by washing with acetone and
dried under vacuum. TMSCl was distilled over CaH2 before use.
Silylated acrylates 1c and 1d were prepared following the reported
procedure42 and not included in the experimental.
1H NMR and 13C NMR spectra were recorded on a Bruker
200 MHz spectrometers. Spectra were referenced to residual
chloroform (
reported in parts per million (
d
7.25 ppm, 1H; 77.00 ppm, 13C). Chemical shifts are
d
); multiplicities are indicated by s
(singlet), d (doublet), t (triplet), q (quartet), quint (pentet), m
(multiplet), and br (broad). Coupling constants, J, are reported in
Hertz. C, H, and N analyses were performed at the Indian Institute of
Technology, Mumbai and at the Hydrometallurgy Division, BARC,
Mumbai. High resolution mass spectra were recorded at 60e70 eV
on a Waters Micromass Q-TOF spectrometer (ESI, Ar). Infrared
spectra (IR) were recorded on a JASCO FTIR spectrophotometer in
NaCl cells or in KBr discs. Peaks are reported in cmꢁ1. The mass
spectra were recorded on a Shimadzu GCeMS 2010 mass spec-
trometer (EI 70 eV). Gas chromatography (GC) studies were carried
out using Younglin Acme 6000 M Gas Chromatograph fitted with
Scheme 5. Regiospecific reductive silylation of dienoates.
3. Conclusions
a
capillary column (WCOT Fused Silica, CP-SIL-5-CB,
m; Carrier: helium 1 mL/min).
50 mꢂ0.25 mm/0.39 mm, 0.25
m
Analytical thin-layer chromatography was performed using home
made silica gel plates (about 0.5 mm).
In conclusion, we have successfully developed a Mg/silyl chlo-
ride/DMF system for the reductive C-silylation at the
b-position of
b
-aryl and -silyl substituted enoates with very good yields. The C-
b
4.1.1. General procedure: preparation of (3RS)-ethyl 3-phenyl-3-tri-
methylsilylpropionate 2a38. Freshly distilled TMSCl (3.8 mL,
30 mmol) was added to a stirred suspension of magnesium turn-
ings (1.46 g, 60 mmol) in dry DMF (20 mL) at room temperature
under an argon atmosphere. After 15 min, a solution of trans-ethyl
cinnamate 1a (0.88 g, 5 mmol) in dry DMF (5 mL) was added to the
reaction mixture, stirred for 0.5 h, and poured into cold saturated
sodium bicarbonate solution. The reaction mixture was extracted
silylation selectivity was very high over the reductive dimerization
or the simple double bond reduction. The reductive silylation
conditions are applicable to
silylation took place at the
allylsilanes as single regioisomer and with very high stereo-
selectivity. The -aryle -silyl and -disilyl propionates can be
considered as a ester homoenolate because tetrabutylammonium
d-aryl substituted dienoates wherein
d-position leading to the synthesis of
b
b
b,b

8566
P.K. Kundu, S.K. Ghosh / Tetrahedron 66 (2010) 8562e8568
with 15% ethyl acetate/hexane. The organic extract was washed
with brine, dried over anhydrous MgSO4, and evaporated. The
residue was purified by column chromatography on silica using
hexane/EtOAc (98:2) as eluent to give the product 2a (1.05 g, 84%)
as a colorless liquid; Rf (95% hexane/EtOAc) 0.52; nmax (liquid film)
3026, 2956, 2899, 1736, 1601, 1495, 1450, 1250, 1163, 1034, 839,
1252, 1166, 1034, 908, 881, 758 cmꢁ1
; dH (200 MHz, CDCl3)
7.28e7.20 (2H, m, Ph), 7.14e7.04 (3H, m, Ph), 4.02 (2H, q, J¼7.1 Hz,
CO2CH2CH3), 3.93e3.85 (1H, m, Me2SiH), 2.89e2.68 (3H, m,
PhCHCH2CO), 1.11 (3H, t, J¼7.1 Hz, CO2CH2CH3), 0.11 (3H, s, J¼3.5 Hz,
SiMeAMeBH), -0.02 (3H, s, J¼3.5 Hz, SiMeAMeBH); dC (50 MHz,
CDCl3) 172.7, 142.1, 128.2 (2C), 127.2 (2C), 125.0, 60.2, 35.5, 30.5,
14.0, ꢁ5.7, ꢁ6.1; m/z (EI) 236 (M, 11), 221 (MꢁMe, 6), 207 (7), 193
(17), 163 (17), 147 (11), 135 (52), 117 (33), 104 (100), 91 (16), 75 (41).
700 cmꢁ1
; dH (200 MHz, CDCl3) 7.26e7.18 (2H, m, Ph), 7.11e7.00
(3H, m, Ph), 3.99 (2H, q, J¼7.1 Hz, CO2CH2CH3), 2.81e2.59 (3H, m,
PhCHCH2CO), 1.08 (3H, t, J¼7.1 Hz, CO2CH2CH3), ꢁ0.04 (9H, s,
Me3Si); dC (50 MHz, CDCl3) 173.1, 142.4, 128.0 (2C), 127.3 (2C), 124.7,
60.1, 34.8, 32.5, 14.0, ꢁ3.2 (3C).
4.1.7. (3RS)-Ethyl 3-(4-methoxyphenyl)-3-trimethylsilylpropionate
2g38. Yield 70%; colorless liquid; Rf (90% hexane/EtOAc) 0.58; nmax
(liquid film) 3069, 2955, 2901, 2835, 1733, 1610, 1510, 1249, 1162,
4.1.2. (3RS)-Ethyl 3-dimethyl(phenyl)silyl-3-phenylpropionate 2b23
.
1108, 1038, 841, 758 cmꢁ1
; dH (200 MHz, CDCl3) 6.95 (2H, d,
Yield 75%, colorless liquid; Rf (95% hexane/EtOAc) 0.53; nmax (liquid
film) 3069, 3025, 2959, 2901, 1733, 1600, 1494, 1450, 1251, 1167,
J¼8.5 Hz, Ar), 6.78 (2H, d, J¼8.5 Hz, Ar), 3.99 (2H, q, J¼7.1 Hz,
CO2CH2CH3), 3.76 (3H, s, OMe), 2.80e2.50 (3H, m, ArCHCH2CO),1.09
(3H, t, J¼7.1 Hz, CO2CH2CH3), ꢁ0.05 (9H, s, SiMe3); dC (50 MHz,
CDCl3) 173.0, 156.8, 134.1, 128.0 (2C), 113.3 (2C), 60.0, 54.9, 34.9,
31.3, 13.9, ꢁ3.3 (3C).
1114, 1033, 908, 835, 699 cmꢁ1
; dH (200 MHz, CDCl3) 7.38e7.30 (4H,
m, Ph), 7.26e7.07 (4H, m, Ph), 6.96e6.92 (2H, m, Ph), 3.90 (2H, q,
J¼7.1 Hz, CO2CH2CH3), 2.88e2.56 (3H, m, PhCHCH2CO), 1.03 (3H, t,
J¼7.1 Hz, CO2CH2CH3), 0.25 (3H, s, SiMeAMeBPh), 0.21 (3H, s,
SiMeAMeBPh); dC (50 MHz, CDCl3) 172.7, 141.6, 136.3, 134.0
(2C), 129.1, 127.9 (2C), 127.6 (2C), 127.4 (2C), 124.8, 60.0, 34.8, 32.2,
13.8, ꢁ4.3, ꢁ5.6.
4.1.8. (3RS)-Ethyl 3-dimethyl(4-methylphenyl)silyl-3-(4-methoxyph-
enyl)propionate 2h. Yield 71%; colorless liquid; Rf (90% hexane/
EtOAc) 0.56; nmax (liquid film) 3065, 3032, 2956, 2904, 2834, 1734,
1606, 1509, 1442, 1247, 1162, 1107, 1038, 842, 795, 778 cmꢁ1
; dH
4.1.3. (3RS)-Ethyl 3-dimethyl(4-methylphenyl)silyl-3-phenylpropionate
2c. Yield 75%, colorless liquid; Rf (95% hexane/EtOAc) 0.50; nmax
(liquid film) 3062, 3025, 2958, 1735, 1602, 1494, 1450, 1250, 1164,
(200 MHz, CDCl3) 7.30 (2H, d, J¼7.6 Hz, Ar), 7.16 (2H, d, J¼7.6 Hz,
Ar), 6.86 (2H, d, J¼8.6 Hz, Ar), 6.74 (2H, d, J¼8.6 Hz, Ar), 3.91 (2H, q,
J¼7.1 Hz, CO2CH2CH3), 3.76 (3H, s, OMe), 2.79e2.52 (3H, m, ArCH-
CH2CO), 2.35 (3H, s, ArMe), 1.04 (3H, t, J¼7.1 Hz, CO2CH2CH3), 0.21
(3H, s, SiMeAMeB), 0.18 (3H, s, SiMeAMeB); dC (50 MHz, CDCl3) 173.0,
157.0, 139.0, 134.1 (2C), 133.60, 132.8, 128.5 (2C), 128.4 (2C), 113.4
(2C), 60.0, 55.0, 35.1, 31.2, 21.3, 13.9, ꢁ4.1, ꢁ5.5; m/z (EI) 356 (M, 6),
149 (100), 134 (22), 121 (13), 91 (4); HRMS (ESI): MNaþ, found
379.1696. C21H28O3SiNa requires 379.1705.
1106, 1034, 836, 796 cmꢁ1
;
dH (200 MHz, CDCl3) 7.30 (2H, d, J¼7.6 Hz,
Ar), 7.27e7.06 (5H, m, Ph), 6.95 (2H, d, J¼7.6 Hz, Ar), 3.91 (2H, q,
J¼7.1 Hz, CO2CH2CH3), 2.96e2.50 (3H, m, PhCHCH2CO), 2.36 (3H, s,
AreMe), 1.04 (3H, t, J¼7.1 Hz, CO2CH2CH3), 0.23 (3H, s, SiMeAMeBAr),
0.20 (3H, s, SiMeAMeBAr); dC (50 MHz, CDCl3) 172.9,141.8,139.0, 134.1
(2C), 132.7, 128.5 (2C), 127.9 (2C), 127.5 (2C), 124.8, 60.0, 34.8, 32.3,
21.3, 13.9, ꢁ4.1, ꢁ5.5; HRMS (ESI): Mþ, found 326.1727. C20H26O2Si
requires 326.1702.
4.1.9. (3RS)-Ethyl 3-dimethyl(4-methylphenyl)silyl-3-trimethylsilyl-
propionate 4a. Yield 81%; colorless liquid; Rf (95% hexane/EtOAc)
0.65; nmax (liquid film) 3067, 2955, 2899, 1736, 1369, 1252, 1199,
4.1.4. (3RS)-Ethyl 3-dimethyl(4-methoxyphenyl)silyl-3-phenylpropio-
nate 2d. Yield 80%, colorless liquid; Rf (95% hexane/EtOAc) 0.36; nmax
(liquid film) 3060, 3023, 2957, 2903, 2837, 1732, 1595, 1504, 1278,
1105, 1037, 837, 734 cmꢁ1
; dH (200 MHz, CDCl3) 7.41 (2H, d,
J¼7.6 Hz, Ar), 7.15 (2H, d, J¼7.6 Hz, Ar), 4.06e3.92 (2H, m,
CO2CH2CH3), 2.37 (2H, d, J¼6.4 Hz, CH2CO), 2.33 (3H, s, ArMe), 1.19
(3H, t, J¼7.1 Hz, CO2CH2CH3), 0.76 (1H, t, J¼6.4 Hz, SiCHCH2CO), 0.30
(3H, s, SiMeAMeB), 0.28 (3H, s, SiMeAMeB), ꢁ0.06 (9H, s, SiMe3); dC
(50 MHz, CDCl3) 174.6,138.5,135.4,133.8 (2C),128.4 (2C), 60.3, 30.9,
21.4, 14.1, 8.6, ꢁ0.4 (3C), ꢁ1.4, ꢁ2.4; m/z (EI) 307 (MꢁMe, 70), 249
(8), 231 (43), 149 (100), 133 (19), 121 (11), 103 (12), 73 (19).
1250, 1183, 1112, 1033, 822 cmꢁ1
; dH (200 MHz, CDCl3) 7.32 (2H, d,
J¼8.5 Hz, Ar), 7.20e6.90 (3H, m, Ph), 6.97e6.90 (2H, m, Ph), 6.89 (2H,
d, J¼8.5 Hz, Ar), 3.95 (2H, q, J¼7.1 Hz, CO2CH2CH3), 3.82 (3H, s, OMe),
2.86e2.57 (3H, m, PhCHCH2CO), 1.04 (3H, t, J¼7.1 Hz, CO2CH2CH3),
0.22 (3H, s, SiMeAMeBAr), 0.20 (3H, s, SiMeAMeBAr); dC (50 MHz,
CDCl3) 173.0, 160.5, 141.8, 135.5 (2C), 127.9 (2C), 127.5 (2C), 127.1,
124.8, 113.4 (2C), 60.1, 54.9, 34.9, 32.5, 13.9, ꢁ4.0, ꢁ5.3; m/z (EI) 342
(M, 15), 327 (MꢁMe, 4), 297 (5), 207 (5), 195 (14), 165 (100), 135 (13),
122 (8), 104 (11); HRMS (ESI): MNaþ, found 365.1542. C20H26O3SiNa
requires 365.1543.
4.1.10. Ethyl 3,3-bis-dimethyl(4-methylphenyl)silylpropionate 4b.
Yield 79%; colorless liquid; Rf (95% hexane/EtOAc) 0.60; nmax (liquid
film) 3066, 3010, 2955, 1734, 1603, 1251, 1104, 1036, 835, 796 cmꢁ1
;
dH (200 MHz, CDCl3) 7.36 (4H, d, J¼7.5 Hz, Ar), 7.13 (4H, d, J¼7.5 Hz,
Ar), 3.84 (2H, q, J¼7.2 Hz, CO2CH2CH3), 2.34 (2H, d, J¼6.5 Hz,
SiCHCH2CO), 2.33 (6H, s, 2ꢂArMe), 1.20 (3H, t, J¼7.2 Hz,
CO2CH2CH3), 1.05 (1H, t, J¼6.5 Hz, SiCHCH2CO), 0.20 (6H, s,
2ꢂSiMeBMeA), 0.18 (6H, s, 2ꢂSiMeBMeA); dC (50 MHz, CDCl3) 174.2,
138.5 (2C), 135.3 (2C), 133.8 (4C), 128.4 (4C), 60.2, 31.0, 21.3 (2C),
13.9, 8.1, ꢁ1.5 (2C), ꢁ2.5 (2C); m/z (EI) 398 (M, 1), 383 (MꢁMe, 45),
308 (17), 307 (54), 249 (11), 207 (14), 149 (100), 133 (26), 121 (16),
103 (11); HRMS (ESI): MNaþ, found 421.1977. C23H34O2Si2Na re-
quires 421.1995.
4.1.5. (3RS)-Ethyl 3-dimethyl(2-propenyl)silyl-3-phenylpropionate 2e.
Yield 89%, colorless liquid; Rf (95% hexane/EtOAc) 0.52; nmax (liquid
film) 3078, 3060, 3026, 2958, 2901,1736,1630,1600,1370,1251,1163,
1035, 897, 838, 701 cmꢁ1
; dH (200 MHz, CDCl3) 7.26e7.20 (2H, m, Ph),
7.13e7.02 (3H, m, Ph), 5.76e5.60 (1H, m, SiCH2CH]CH2), 4.87e4.81
(2H, m, SiCH2CH]CH2), 3.98 (2H, q, J¼7.1 Hz, CO2CH2CH3), 2.89e2.66
(3H, m, PhCHCH2CO), 1.47 (2H, d, J¼7.9 Hz, SiCH2CH]CH2), 1.08 (3H,
t, J¼7.1 Hz, CO2CH2CH3), ꢁ0.01 (3H, s, SiMeAMeB), ꢁ0.06 (3H, s,
SiMeAMeB); dC (50 MHz, CDCl3) 172.8, 141.9, 134.1, 128.1 (2C), 127.3
(2C),124.8,113.5, 60.1, 34.8, 31.4, 21.4,13.9, ꢁ5.3 (2C); m/z (EI) 276 (M,
1), 261 (MꢁMe, 5), 235 (MꢁC3H5, 100), 207 (27), 171 (9), 147 (9), 99
(60), 75 (66); HRMS (ESI): MNaþ, found 299.1411. C16H24O2SiNa re-
quires 299.1444.
4.1.11. (3RS)-Methyl 3-dimethyl(phenyl)silyl-3-trimethylsilylpropio-
nate 4c. Yield 70%; colorless liquid; Rf (95% hexane/EtOAc) 0.58;
nmax (liquid film) 3069, 2999, 2952, 2898, 1739, 1428, 1348, 1252,
1204, 1050, 1032, 837, 815 cmꢁ1
; dH (200 MHz, CDCl3) 7.54e7.47
4.1.6. (3RS)-Ethyl 3-dimethyl(hydro)silyl-3-phenylpropionate 2f.
Yield 85%, colorless liquid; Rf (95% hexane/EtOAc) 0.56; nmax (liquid
film) 3061, 3025, 2961, 2903, 2116, 1734, 1601, 1494, 1450, 1371,
(2H, m, Ph), 7.35e7.32 (3H, m, Ph), 3.53 (3H, s, CO2CH3), 2.38 (2H, d,
J¼6.5 Hz, SiCHCH2CO), 0.77 (1H, t, J¼6.5 Hz, SiCHCH2CO), 0.32 (3H,
s, SiMeAMeB), 0.30 (3H, s, SiMeAMeB), ꢁ0.06 (9H, s, SiMe3);

P.K. Kundu, S.K. Ghosh / Tetrahedron 66 (2010) 8562e8568
8567
dC (50 MHz, CDCl3) 174.8, 139.0, 133.7 (2C), 128.8, 127.6 (2C), 51.4,
30.6, 8.7, ꢁ0.5 (3C), ꢁ1.5, ꢁ2.6; m/z (EI) 294 (M, 2), 279 (MꢁMe, 80),
217 (50), 163 (19), 151 (27), 135 (100), 121 (26), 89 (41), 73 (30).
CHCH]CHCH2), 2.96 (1H, d, J¼10.0 Hz, CHCH]CHCH2), 1.25 (3H, t,
J¼7.1 Hz, CO2CH2CH3), ꢁ0.04 (9H, s, SiMe3); dC (50 MHz, CDCl3)
171.9, 142.2, 133.7, 128.2 (2C), 127.0 (2C), 124.5, 120.0, 60.4, 42.9,
38.3, 14.1, ꢁ3.1 (3C); GCeMS (EI) (column: WCOT Fused Silica, CP-
4.1.12. Methyl 3,3-bis-dimethyl(phenyl)silylpropionate 4d. Yield
71%; colorless liquid; Rf (95% hexane/EtOAc) 0.56; nmax (liquid film)
3069, 3049, 2952, 2899, 2843, 1738, 1427, 1349, 1253, 1206, 1112,
SIL-5-CB, 50 mꢂ0.25 mm/0.39 mm, 0.25
mm; Carrier: helium 1 mL/
min; temp: 60 ꢀC-2 min-10 ꢀC/min-300 ꢀC): tR 16.57 min, (3E,5RS)-
10a (86%); tR 16.79 min, (3Z,5RS)-10a (14%); m/z for (3E,5RS)-10a:
276 (M,11), 261 (MꢁMe, 3), 158 (21), 130 (99), 115 (23), 73 (100); m/
z for (3Z,5RS)-10a: 276 (M, 11), 261 (MꢁMe, 3), 158 (10), 130 (67),
115 (19), 73 (100).
1048,1027, 838, 813, 700 cmꢁ1
; dH (200 MHz, CDCl3) 7.49e7.44 (4H,
m, Ph), 7.34e7.30 (6H, m, Ph), 3.38 (3H, s, CO2CH3), 2.38 (2H, d,
J¼6.6 Hz, SiCHCH2CO), 1.07 (1H, t, J¼6.6 Hz, SiCHCH2CO), 0.30 (6H,
s, 2ꢂSiMeAMeB), 0.20 (6H, s, 2ꢂSiMeBMeA); dC (50 MHz, CDCl3)
174.6, 138.9 (2C), 133.8 (4C), 128.9 (2C), 127.6 (4C), 51.4, 30.8, 8.3,
ꢁ1.6 (2C), ꢁ2.6 (2C); m/z (EI) 356 (M, 3), 341 (MꢁMe, 59), 279 (60),
231 (15), 221 (34), 193 (13), 151 (23),135 (100),121 (22), 107 (11), 89
(14); HRMS (ESI): MNaþ, found 379.1510. C20H28O2Si2Na requires
379.1526.
4.1.17. (3E,5RS)-Ethyl 5-dimethyl(4-methylphenyl)silyl-5-phenylpenta
noate 10b. Yield 70%; colorless liquid; contains 19% of (3Z,5RS)-iso-
mer; Rf (95% hexane/EtOAc) 0.57; nmax (liquid film) 3061, 3025, 2979,
2871, 1733, 1659, 1601, 1494, 1369, 1248, 1157, 1106, 1030, 967, 831,
760 cmꢁ1
; dH (200 MHz, CDCl3) 7.41e7.04 (7H, m, Ph and Ar), 6.90
(2H, d, J¼7.3 Hz, Ar), 5.85 (1H, dd, J¼15.0, 9.9 Hz, SiCHCH]CHCH2),
5.51e5.36 (1H, m, SiCHCH]CHCH2), 4.13 (2H, q, J¼7.1 Hz,
CO2CH2CH3), 3.12 (1H, d, J¼9.9 Hz, SiCHCH]CHCH2), 3.03 (2H, d,
J¼7.1 Hz, SiCHCH]CHCH2), 2.35 (3H, s, ArMe), 1.25 (3H, t, J¼7.1 Hz,
CO2CH2CH3), 0.23 (6H, s, SiMe2); dC (50 MHz, CDCl3) 171.8, 141.6,
138.8, 134.3 (2C),133.6,132.8,128.2 (2C), 128.0 (2C),127.3 (2C), 124.6,
120.2, 60.4, 42.7, 38.3, 21.4, 14.1, ꢁ4.3, ꢁ4.8; GCeMS (EI) (column:
4.1.13. (3RS)-Methyl 3-dimethyl(4-methylphenyl)silyl-3-dimethyl(phe-
nyl)silylpropionate 4e. Yield 70%; colorless liquid; Rf (95% hexane/
EtOAc) 0.57; nmax (liquid film) 3068, 3011, 2952, 2900, 1739, 1428,
1348, 1252, 1204, 1105, 1048, 1032, 831, 815, 797 cmꢁ1
; dH (200 MHz,
CDCl3) 7.49e7.28 (7H, m, Ar), 7.14 (2H, d, J¼7.5 Hz, Ar), 3.39 (3H, s,
CO2CH3), 2.38 (2H, d, J¼6.6 Hz, SiCHCH2CO), 2.34 (3H, s, ArMe), 1.05
(1H, t, J¼6.6 Hz, SiCHCH2CO), 0.23 (3H, s, SiMeBMeA), 0.20 (6H, s,
2ꢂSiMeAMeB), 0.18 (3H, s, SiMeBMeA); dC (50 MHz, CDCl3) 174.7,
139.0, 138.7, 135.2, 133.9 (4C), 128.8, 128.5 (2C), 127.6 (2C), 51.4, 30.8,
21.4, 8.4, ꢁ1.5 (2C), ꢁ2.5, ꢁ2.6; m/z (EI) 370 (M, 1), 355 (MꢁMe, 56),
280 (15), 279 (53), 235 (17),193 (11),165 (18),149 (100),135 (80),121
(30), 105 (15), 89 (23); HRMS (ESI): MNaþ, found 393.1665.
C21H30O2Si2Na requires 393.1682.
WCOT Fused Silica, CP-SIL-5-CB, 50 mꢂ0.25 mm/0.39 mm, 0.25
mm;
Carrier: helium 1 mL/min; temp: 60 ꢀC-2 min-10 ꢀC/min-300 ꢀC): tR
21.6 min, (3E,5RS)-10b (80%); tR 21.94 min, (3Z,5RS)-10b (20%); m/z
for (3E,5RS)-10b: 352 (M, 7), 149 (100), 130 (28), 121 (11); m/z for
(3Z,5RS)-10b: 352 (M, 13), 149 (100), 130 (41), 121 (15); HRMS (ESI):
MHþ, found 353.1921. C22H29O2Si requires 353.1937.
Supplementary data
4.1.14. (3RS)-Methyl 3-dimethyl(4-methoxyphenyl)silyl-3-dimethyl
(phenyl)silylpropionate 4f. Yield 70%; colorless liquid; Rf (95% hex-
ane/EtOAc) 0.47; nmax (liquid film) 3068, 3019, 2999, 2952, 2902,
2837, 1738, 1503, 1428, 1278, 1249, 1205, 1183, 1111, 1032, 834,
Supplementary data associated with this article can be found in
online version at doi:10.1016/j.tet.2010.09.001. These data include
MOL files and InChIKeys of the most important compounds
described in this article.
810 cmꢁ1
; dH (200 MHz, CDCl3) 7.48e7.32 (7H, m, Ar), 6.88 (2H, d,
J¼8.2 Hz, Ar), 3.81 (3H, s, CO2CH3), 3.41 (3H, s, ArOMe), 2.38 (2H, d,
J¼6.5 Hz, SiCHCH2CO), 1.04 (1H, t, J¼6.5 Hz, SiCHCH2CO), 0.28 (3H,
s, SiMeBMeA), 0.20 (6H, s, 2ꢂSiMeAMeB), 0.18 (3H, s, SiMeBMeA); dC
(50 MHz, CDCl3) 174.7, 160.2, 139.0, 135.2 (2C), 133.8 (2C), 129.6,
128.8, 127.6 (2C), 113.3 (2C), 54.9, 51.4, 30.8, 8.5, ꢁ1.5, ꢁ1.6, ꢁ2.4,
ꢁ2.6; m/z (EI) 371 (MꢁMe, 58), 231(11), 181 (14), 165 (100), 151
(32), 135 (65), 121 (23), 89 (21).
References and notes
1. Colvin, E. W. Silicon Reagents in Organic Synthesis; Academic: London, 1988.
2. Greene, T. W.; Wuts, P. M. G. Protective Groups in Organic Synthesis, 2nd ed.;
Wiley Interscience: New York, NY, 1990.
3. (a) Bols, M.; Skrydstrup, T. Chem. Rev. 1995, 95, 1253; (b) Fensterbank, L.;
Malacria, M.; Sieburth, S. McN Synthesis 1997, 813; (c) Gauthier, D. R.; Zandi, K.
S.; Shea, K. J. Tetrahedron 1998, 54, 2289.
4. (a) Fleming, I. Chemtracts: Org. Chem. 1996, 9, 1; (b) Tamao, K.; Ishida, N.; Ito, Y.;
Kumada, M. Org. Synth. 1990, 69, 96.
5. (a) Fleming, I.; Dunogues, J.; Smithers, R. Org. React. 1989, Chaper 2; (b)
Hiyama, T. Chem. Record 2008, 8, 337; (c) Hosomi, A.; Miura, K. Bull. Chem. Soc.
Jpn. 2004, 77, 835.
4.1.15. (3RS)-methyl 3-dimethyl(2-propenyl)silyl-3-dimethyl(phenyl)
silylpropionate 4g. Yield 72%; colorless liquid; Rf (95% hexane/
EtOAc) 0.57; nmax (liquid film) 3070, 2952, 2901, 1739, 1630, 1428,
1254, 1204, 1157, 1112, 1028, 814, 700 cmꢁ1
; dH (200 MHz, CDCl3)
7.54e7.49 (2H, m, Ph), 7.36e7.33 (3H, m, Ph), 5.81e5.59 (1H, m,
SiCH2CH]CH2), 4.84e4.75 (2H, m, SiCH2CH]CH2), 3.51 (3H, s,
CO2CH3), 2.41 (2H, d, J¼6.4 Hz, SiCHCH2CO), 1.48e1.43 (2H, m,
SiCH2CH]CH2), 0.84 (1H, t, J¼6.4 Hz, SiCHCH2CO), 0.34 (3H, s,
SiMeAMeB), 0.32 (3H, s, SiMeAMeB), ꢁ0.05 (3H, s, SiMeBMeA), ꢁ0.06
(3H, s, SiMeBMeA); dC (50 MHz, CDCl3) 174.7, 138.8, 134.7, 133.8 (2C),
128.9, 127.6 (2C), 113.2, 51.5, 30.5, 23.6, 7.5, ꢁ1.5, ꢁ2.4, ꢁ2.5, ꢁ3.1;
m/z (EI) 305 (MꢁMe, 3), 279 (MꢁC3H5, 94), 231 (23), 163 (41), 151
(25), 135 (100), 121 (31), 89 (62); HRMS (ESI): MNaþ, found
343.1526. C17H28O2Si2Na requires 343.1526.
6. Sommer, L. H.; Bailey, D. L.; Goldberg, G. M.; Buck, C. E.; Bye, T. S.; Evans, F. J.;
Whitmore, F. C. J. Am. Chem. Soc. 1954, 76, 1613.
7. For a review, see: White, J. M. Aust. J. Chem. 1995, 48, 1227.
8. Magnus, P. D.; Sarkar, T. K.; Djuric, S. In Comprehensive Organometallic Chem-
istry; Wilkinson, G., Stone, F. G. A., Abell, E. W., Eds.; Pergamon: Oxford, 1981,
Chapter 48.
9. Hudrlik, P. F.; Hudrlik, A. M.; Yimenu, T.; Waugh, M. A.; Nagendrappa, G.
Tetrahedron 1988, 44, 3791.
10. Sarkar, T. K.; Ghorai, B. K. J. Chem. Soc., Chem. Commun. 1992, 1184.
11. (a) Nishiyama, H.; Sakuta, K.; Osaka, N.; Arai, H.; Matsumoto, M.; Itoh, K.
Tetrahedron 1988, 44, 2413; (b) Hudrlik, P. F.; Waugh, M. A.; Hudrlik, A. M. J.
Organomet. Chem. 1984, 271, 69.
12. Verma, R.; Ghosh, S. K. J. Chem. Soc., Perkin Trans. 1 1998, 2377.
13. (a) Hwu, J. R.; Gilbert, B. A.; Lin, L. C.; Liaw, B. R. J. Chem. Soc., Chem. Commun.
1990, 161; (b) Hwu, J. R.; Chen, B.-L.; Huang, L. W.; Yang, T.-H. J. Chem. Soc.,
Chem. Commun. 1995, 299.
14. (a) Thorimbert, S.; Malacria, M. Tetrahedron Lett. 1996, 37, 8483; (b) Thorimbert,
S.; Malacria, M. Tetrahedron Lett. 1998, 39, 9659; (c) Commandeur, C.; Thor-
imbert, S.; Malacria, M. J. Org. Chem. 2003, 68, 5588.
15. (a) Denmark, S. E.; Wallace, M. A.; Walker, C. B. J. Org. Chem. 1990, 55, 5543; (b)
Kang, K.-T.; Kim, S. S.; Lee, J. C.; Jong, S. U. Tetrahedron Lett. 1992, 33, 3495.
16. Nishiyama, H.; Matsumoto, M.; Arai, H.; Sakaguchi, H.; Itoh, K. Tetrahedron Lett.
1986, 27, 1599.
4.1.16. (3E,5RS)-Ethyl 5-phenyl-5-trimethylsilylpentanoate 10a.
Yield 72%; colorless liquid; contains 14% of (3Z,5RS)-isomer; Rf (95%
hexane/EtOAc) 0.58; nmax (liquid film) 3061, 3026, 2980, 2957, 2898,
2871, 1737, 1638, 1600, 1495, 1368, 1249, 1159, 1031, 968, 839,
700 cmꢁ1
; dH (200 MHz, CDCl3) 7.29e7.04 (5H, m, Ph), 5.93 (1H, dd,
J¼15.0, 10.0 Hz, SiCHCH]CHCH2), 5.57e5.43 (1H, m, SiCHCH]
CHCH2), 4.13 (2H, q, J¼7.1 Hz, CO2CH2CH3), 3.06 (2H, d, J¼6.9 Hz,

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