New evidence on the regiochemistry of the tert-butyldiphenylsilylcupration of allene using the silylcuprate or silylcopper reagent

Article abstract of DOI:10.1016/S0040-4020(03)00945-1

The regiochemistry in the tert-butyldiphenylsilylcupration of the allene depends on the temperature and also on the nature of the electrophile. Thus, the intermediate generated by addition of the silylcuprate at -78°C reacted with electrophiles to give allylsilanes, except with oxo compounds which afforded vinylsilanes. On the other hand, the silylcopper reagent was added at -40°C leading, in all cases, to the corresponding allylsilanes. When enones were used as electrophile the vinylsilanes were the 1,2-addition products and the allylsilanes those from 1,4-addition. These functionalized vinyl or allyl tert-butyldiphenylsilanes are interesting synthons for the preparation of conjugated tert-butyldiphenylsilyltrienes and functionalized exocyclic alkylidenecyclopentenes.

Full text of DOI:10.1016/S0040-4020(03)00945-1

Tetrahedron 59 (2003) 5855–5859
New evidence on the regiochemistry of the
tert-butyldiphenylsilylcupration of allene using the
silylcuprate or silylcopper reagent
*
Purificacion Cuadrado, Ana M. Gonzalez-Nogal, Alicia Sanchez and M. Angeles Sarmentero
´
´
´
´ ´
Departamento de Quımica Organica, Universidad de Valladolid, Dr Mergelina sn, 47011 Valladolid, Spain
Received 7 April 2003; revised 8 May 2003; accepted 13 June 2003
Abstract—The regiochemistry in the tert-butyldiphenylsilylcupration of the allene depends on the temperature and also on the nature of the
electrophile. Thus, the intermediate generated by addition of the silylcuprate at 2788C reacted with electrophiles to give allylsilanes, except
with oxo compounds which afforded vinylsilanes. On the other hand, the silylcopper reagent was added at 2408C leading, in all cases, to the
corresponding allylsilanes. When enones were used as electrophile the vinylsilanes were the 1,2-addition products and the allylsilanes those
from 1,4-addition. These functionalized vinyl or allyl tert-butyldiphenylsilanes are interesting synthons for the preparation of conjugated
tert-butyldiphenylsilyltrienes and functionalized exocyclic alkylidenecyclopentenes.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
aldehyde, acetone, cinnamaldehyde, methylvinylketone
and 2-cyclohexenone as electrophiles and the products
were identified by 13C and 1H NMR spectroscopy at
300 MHz, we realized that they had a vinylsilane structure
instead of allylsilane. Moreover, we have synthesized the
allylsilane 5g by silylcupration from allene with the tert-
butyldiphenylsilylcopper reagent at 2408C and subsequent
treatment with cinnamaldehyde. In this case, 5g (54%) was
obtained together with the allylsilane 5k (17%) resulting
from 1,4-addition (Scheme 7). When enones were used as
electrophiles, the reaction products were the allylsilanes
from 1,4-addition rather than the vinylsilanes from 1,2-
addition obtained by reaction with the silylcuprate.
Some years ago1 we reported that lithium bis-(tert-
butyldiphenylsilyl)cuprate reacts regioselectively with
allenes affording allyl- or vinylsilanes. The regiochemistry
depends not only on the substitution pattern of allene but
also on the temperature. Thus, the lithium bis-(tert-
butyldiphenylsilyl)cuprate reacts at 2788C with allene
itself 1 followed by hydrolysis at this temperature to give
the allylsilane 2 resulting from addition of the bulky tert-
butyldiphenylsilyl group at the less hindered extreme of
allene. When the reaction was carried out at 08C, the
regiochemistry changed and we obtained the vinylsilane 3
(Scheme 1).
We also described1 that the reaction of allylsilane–
vinylcuprate intermediate 4, generated at 2788C, with
other electrophiles different from proton such as methyl
iodide, iodine, acetyl chloride, ethylene oxide and oxo
compounds, yielded the corresponding allylsilanes 5a–i
(Scheme 2).
2. Results and discussion
2.1. Silylcupration of allene using lithium bis-(tert-
butyldiphenylsilyl)cuprate and reaction with
electrophiles
The lithium bis-(tert-butyldiphenylsilyl)cuprate reacts with
A recent revision of the reaction of the tert-butyldiphenyl-
silylcupration intermediates with carbonyl compounds has
revealed that we committed a mistake in the assignment of
the regiochemistry of the compounds 5e–i, which was
established in the base of the 1H NMR spectrum recorded at
80 MHz. When we repeated the reaction using acet-
Keywords: allene; silylcupration; allylsilanes; vinylsilanes.
*
Corresponding author. Tel.: þ34-983-423-213; fax: þ34-983-423-013;
e-mail: agn@qo.uva.es
Scheme 1.
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00945-1

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P. Cuadrado et al. / Tetrahedron 59 (2003) 5855–5859
Scheme 4.
8 from the alcohol 7c by dehydration with trifluoroacetic
acid (Scheme 4).
2.2. Silylcupration of allene with the tert-
butyldiphenylsilylcopper reagent
We demonstrated earlier3 that the dimethylphenylsilyl-
copper reagent is added to allene with the opposite
regioselectivity to that shown by the corresponding
silylcuprate. With the aim of obtaining allylsilanes, more
interesting than their regioisomer vinylsilanes,4,5 we have
accomplished the silylcupration of allene using the tert-
butyldiphenylsilylcopper reagent. In order to know the
regioselectivity of the allene silylcupration with this new
reagent, we have carried out the reaction at several
temperatures. We have verified that, as opposed to the
silylcuprate, the silylcopper reagent is always added to the
end of the allenic system, independently of the temperature,
to give an allylsilane intermediate 4, whose hydrolysis
afforded, in all cases, the allylsilane 2 (Scheme 5).
Scheme 2.
allene 1 at 2788C and then with acetaldehyde, acetone,
cinnamaldehyde, methylvinylketone and 2-cyclohexenone
between 2788C and 08C to give the vinylsilanes 7a–e by
1,2-addition from the intermediate 6 instead of the expected
allylsilanes 5e–i. The presumed intermediate 6 did not react
with cinnamoyl chloride and only the vinylsilane 3 resulting
from protodecupration was formed. Other electrophiles such
as methyl iodide, iodine, acetyl chloride and ethylene oxide
afforded the corresponding allylsilanes 5a–d via the
intermediate 4, as was described in our earlier paper.1
Presumably, the addition of the silylcuprate is reversible and
the overall regiochemistry is controlled in either sense, not
only by the temperature but also by the electrophile
(Scheme 3).
The reaction with other electrophiles different from proton
is more complicated. Some electrophiles, like methyl iodide
and acetyl chloride, react easily and in good yields at 2788C
via the allylsilane intermediate 4, leading to the correspond-
ing allylsilanes 5a and 5c, but the cinnamoyl chloride does
not react at this temperature. We isolated only the
vinylsilane 3 resulting from protodecupration of the
vinylsilane intermediate 6. Fortunately, the intermediate
allylsilane 4, generated at 2408C, reacted successfully with
cinnamoyl chloride to give the expected allylsilane 5j,
which was impossible to synthesize through the silylcuprate
(Scheme 6).
Although the vinylsilanes bearing the bulky tert-butyldi-
phenylsilyl group can be substituted for electrophiles,2 one
advantage of this hindered group versus the dimethylphe-
nylsilyl or trimethylsilyl group is the possibility of its
heating with acids without protodesilylation.2 This allowed
us to synthesize the conjugated tert-butyldiphenylsilyltriene
At this temperature, the vinylcopper intermediate 4 reacted
with a,b-unsaturated oxo compounds such as cinnamalde-
hyde, benzalacetone and 2-cyclohexenone, affording the
allylsilane 5g resulting from 1,2-addition and the allylsi-
lanes 5k–5m from 1,4-addition. On the contrary, the 1-
acetylcyclohexene and saturated oxo compounds, like
acetaldehyde and acetone, did not react with the intermedi-
ate 4. In the same conditions, the allylsilane 2 resulting from
the final hydrolysis was exclusively obtained (Scheme 7).
The utility of vinyl and divinyl ketones containing an
allylsilane moiety is well-documented. They can serve as
substrates for the synthesis of methylencyclopentanols by
Scheme 3.
Scheme 5.

P. Cuadrado et al. / Tetrahedron 59 (2003) 5855–5859
5857
Scheme 8.
1,2- and 1,4-addition products was isolated. Other electro-
philes like cinnamoyl chloride, unreactive in the reaction
with the silylcuprate, were shown to be very reactive when
the silylcopper was used. In any case, the products of these
reactions are functionalized allyl or vinylsilanes with many
uses in organic synthesis,8 whose two new applications are
described here.
Scheme 6.
Lewis acid-catalyzed annulation6 or cyclopentenones via
silicon-directed Nazarov cyclizations.7 Nevertheless, the
synthetic possibilities of allylsilanes bearing a diallylalco-
hol unit in annulation processes have not been exploited.
3. Experimental
3.1. General
Attempts to induce the allyl-mediated cyclization of 5g by
protic or Lewis acids, such as TFA, TiCl4, SnCl4, FeCl3, and
AlCl3 were unsatisfactory. Nevertheless, when 5g reacted
with ethyl chloroformate in the presence of AlCl3, the
electrophilic substitution of the allylsilane moiety occurred
with concomitant cyclization to give 9 as a 1:9 mixture of Z/
E stereoisomers. The ester group, more electroattractive
than the tert-butyldiphenylsilyl group, evidently enhances
the acidity of the a-hydrogen and promotes the annulation
(Scheme 8). This result opens an interesting route to
functionalized exocyclic alkylidenecyclopentenes.
THF was distilled from sodium benzophenone ketyl in a
recycling still. All chromatographic and work-up solvents
were distilled prior to use. Copper (I) cyanide was dried in
vacuo over P2O5. The allene 1 was bought. Lithium tert-
butyldiphenylsilylcuprate was prepared as previously
described1 and the tert-butyldiphenylsilylcopper reagent
was prepared in the same way mixing one equivalent of the
tert-butyldiphenylsilyllithium and one equivalent of copper
(I) cyanide. All reactions involving organometallic reagents
1
were carried out under nitrogen atmosphere. H and 13C
NMR spectra were recorded at 300 and 75 MHz, respect-
ively, in CDCl3 as an internal standard. Carbon multi-
plicities were assigned by DEPT experiments. Reactions
were monitored by TLC on a pre-coated plate of silica gel
60 (nano-SIL-20, Macherey-Nagel). Flash chromatography
was performed on silica gel 60 (230–400 mesh, M–N).
In conclusion, as well as correcting an earlier error, we now
report two complementary methods of regiocontrol in the
tert-butyldiphenylsilylcupration of allene. Especially inter-
esting is the reaction of the silylcupration intermediates with
oxo compounds, which affords vinylsilanes with the
silylcuprate and allylsilanes with the silylcopper reagent.
Furthermore, with enones as electrophiles the vinylsilanes
were the allylic alcohols resulting from 1,2-addition
whereas the allylsilanes were the ketones from 1,4-addition.
When cinnamaldehyde was used as an electrophile for
quenching the silylcopper intermediate, a 3:1 mixture of
3.2. tert-Butyldiphenylsilylcupration of allene with
lithium tert-butyldiphenylsilylcuprate and reactions
with electrophiles
The general procedure is the one previously described1 and
when we have used as electrophiles methyl iodide, iodine,
acetyl chloride and ethylene oxide the products obtained
were the same allylsilanes 5a–d as described earlier.1
Nevertheless, the products resulting from the reactions with
carbonyl compounds have the structure of vinylsilanes 7a–e
rather than allylsilanes 5e–i. To confirm it we describe
below their spectroscopic properties.
3.2.1. 4-(tert-Butyldiphenylslyl)pent-4-en-2-ol (7a). By
reaction of allylcuprate 6 with acetaldehyde (70% yield);
Rf¼0.2 (hexane/EtOAc, 20:1); IR (CCl4) 3600 sharp, 3200
1
broad, 1630, 1110, 1080 and 870 cm21; H NMR d 7.65–
7.53 (m, 4H), 7.47–7.29 (m, 6H), 6.09 (d, J¼2.5 Hz, 1H),
5.81 (d, J¼2.5 Hz, 1H), 3.58 (m, 1H), 2.40 (dd, J¼15.1,
4.2 Hz, 1H), 2.25 (dd, J¼15, 8.4 Hz, 1H), 1.58 (s br, 1H),
1.18 (s, 9H), and 1.04 (d, J¼6.9 Hz, 3H); 13C NMR d
144.13, 136.36, 134.32, 132.41, 129.26, 127.78, 65.55,
47.64, 29.72, 22.76, 18.52; MS (EI) m/z 267 (Mþ2But,
28%), 249 (8), 199 (100), 181 (10), 135 (5), 105 (12), 77
Scheme 7.

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P. Cuadrado et al. / Tetrahedron 59 (2003) 5855–5859
(10) and 57 (15). Anal. calcd for C21H28OSi: C, 77.72; H,
8.70. Found: C, 77.8; H, 8.75.
2408C and stirred under nitrogen for 1 h. The electrophile
(2 mmol) was added dropwise at 2408C and then the
mixture was slowly allowed to warm to 08C until TLC
indicated complete reaction. Quenching at 08C with aqueous
ammonium chloride, aqueous workup with diethyl ether,
drying (MgSO4), and chromatography gave the following
products.
3.2.2. 4-(tert-Butyldiphenylsilyl)-2-methylpent-4-en-2-ol
(7b). By reaction of 6 with acetone (45%); Rf¼0.2 (hexane/
EtOAc, 20:1); IR (neat) 3300, 1630, 1190, 1100 and
1
850 cm21; H NMR d 7.70–7.55 (m, 4H), 7.49–7.37 (m,
6H), 6.10 (d, J¼2.1 Hz, 1H), 5.82 (d, J¼2.1 Hz, 1H), 2.35
(s, 2H), 1.56 (s br, 1H), 1.24 (s, 6H) and 1.17 (s, 9H); MS
(EI) m/z 281 (Mþ2But, 8%), 199 (100), 181 (12), 135 (8),
105 (10), 77 (22) and 57 (28). Anal. calcd for C22H30OSi: C,
78.05; H, 8.93. Found: C, 77.90; H, 8.97.
3.3.1. 3-(tert-Butyldiphenylsilyl)propene (2). By hydroly-
sis of the intermediate from silylcupration (95% yield);
Rf¼0.55 (hexane); IR (neat) 1660, 1100, and 810 cm21; 1H
NMR d 7.81–7.62 (m, 4H), 7.49–7.36 (m, 6H), 5.84 (ddt,
J¼18.0, 10.1, 7.8 Hz, 1H), 4.98 (dd, J¼18.0, 2.0 Hz, 1H),
4.89 (dd, J¼10.1, 2.0, 1H), 2.27 (d, J¼7.8 Hz, 2H), and 1.16
(s, 9H); 13C NMR d 134.71, 136.05, 134.45, 129.16, 127.61,
114.61, 27.94, 18.84, and 18.56; MS (EI) m/z 280 (Mþ, 3%),
239 (20), 223 (35), 197 (19), 181 (22), 145 (21), 135 (100),
and 105 (77).
3.2.3. (E)-5-(tert-Butyldiphenylsilyl)-1-phenylhexa-1,5-
dien-3-ol (7c). By reaction of cinnamaldehyde with 6;
colorless oil (70%); Rf¼0.18 (hexane/EtOac, 20:1); IR
(CCl4) 3660 sharp, 3400 br, 1620, 1100, and 960 cm21; 1H
NMR d 7.74–7.60 (m, 4H), 7.45–7.19 (m, 11H), 6.24 (d,
J¼15.9 Hz, 1H), 6.15 (d, J¼2.6 Hz, 1H), 6.02 (dd, J¼15.9,
6.4 Hz, 1H), 5.86 (d, J¼2.6 Hz, 1H); 4.02 (m, 1H), 2.53 (dd,
J¼15.4, 4.3 Hz, 1H), 2.43 (dd, J¼15.4, 8.5 Hz, 1H), 1.75 (s
br, 1H), and 1.18 (s, 9H); 13C NMR d 142.65, 136.11,
135.39, 134.65, 134.06, 132.74, 131.45, 129.23, 128.23,
127.55, 127.39, 126.17, 70.59, 54.52, 26.41, and 18.82; MS
(EI) m/z 355 (Mþ2But, 51%), 337 (15), 277 (20), 259 (18),
199 (100), 183 (90), 135 (95), 105 (65), 77 (24), and 57 (26).
Anal. calcd for C28H32OSi: C, 81.50; H, 7.82. Found: C,
81.73; H, 7.87.
3.3.2. 3-(tert-Butyldiphenylsilyl)-2-methylpropene (5a).
Using methyl iodide as an electrophile at 2788C (85%);
Rf¼0.59 (hexane); IR (neat) 1640, 1100, and 880 cm21; 1H
NMR d 7.90–7.81 (m, 4H), 7.52–7.46 (m, 6H), 4.76 (d,
J¼1.3 Hz, 1H), 4.73 (d, J¼1.3 Hz, 1H), 2.39 (s, 2H), 1.56
(s, 3H), and 1.21 (s, 9H); 13C NMR d 143.15, 136.12,
134.79, 129.03, 127.39, 110.85, 27.76, 25.46, 22.17, and
18.55; MS (EI) m/z 294 (Mþ, 4%), 237 (80), 135 (100), 105
(58), and 57 (39).
3.2.4. 5-(tert-Butyldiphenylsilyl)-3-methylhexa-1,5-dien-
3-ol (7d). By adding methylvinylketone to 6; colorless oil
(67%); Rf¼0.19 (hexane/EtOAc, 20:1); IR (neat) 3500,
3.3.3. 3-[(tert-Butyldiphenylsilyl)methyl]but-3-en-2-one
(5c). By reaction of intermediate generated at 2788C with
acetyl chloride (88%); Rf¼0.36 (hexane/EtOAc, 20:1); IR
1
1
1630, 1100, 990 and 830 cm21; H NMR d 7.76–7.61 (m,
(neat) 1700, 1670, 1610, 1100, and 810 cm21; H NMR d
4H), 7.42–7.34 (m, 6H), 6.17 (d, J¼2.4 Hz, 1H), 5.88 (d,
J¼2.4 Hz, 1H), 5.63 (dd, J¼17.1, 10.2 Hz, 1H), 5.26 (dd,
J¼17.1, 1.9 Hz, 1H), 4.92 (dd, J¼10.2, 1.9 Hz, 1H), 2.53 (d,
J¼15.3 Hz, 1H), 2.43 (d, J¼15.3 Hz, 1H), 2.07 (s br, 1H),
1.26 (s, 3H) and 1.18 (s, 9H); MS (EI) m/z 293 (Mþ2But,
6%), 199 (100), 163 (4), 105 (30), 77 (25), and 57 (16).
Anal. calcd for C23H30OSi: C, 78.80; H, 8.63. Found: C,
78.66; H, 8.57.
7.62–7.59 (m, 4H), 7.40–7.33 (m, 6H), 5.68 (s, 1H), 5.38
(s, 1H), 2.49 (s, 2H), 1.97 (s, 3H), and 1.09 (s, 9H); 13C
NMR d 199.27, 146.30, 136.21, 133.76, 128.96, 127.26,
123.36, 27.57, 24.91, 18.31, and 12.69; MS (EI) m/z 322
(Mþ, 1%), 265 (100), 181 (24), 135 (81), 105 (83), 77 (32),
and 43 (83).
3.3.4. 2-(tert-Butyldiphenylsilyl)propene (3). By reaction
of intermediate formed at 2788C with cinnamoyl chloride
(86%); Rf¼0.75 (hexane); IR (neat) 1620, 1100, and
3.2.5. 1-[2-(tert-Butyldiphenylsilyl)prop-2-en-1-yl]cyclo-
hex-2-enol (7e). By reaction of 2-cyclohexenone with 6;
colorless oil (45%); Rf¼0.20 (hexane/EtOAc, 20:1); IR
1
810 cm21; H NMR d 7.75–7.54 (m, 4H), 7.42–7.30 (m,
6H), 5.95 (d, J¼3.2 Hz, 1H), 5.48 (d, J¼3.2 Hz, 1H), 1.98
(s, 3H), and 1.16 (s, 9H); 13C NMR d 142.22, 136.17,
135.34, 129.10, 127.44, 131.54, 27.46, 25.22, and 18.29;
MS (EI) m/z 280 (Mþ, 1%), 223 (100), 197 (38), 183 (30),
and 105 (58).
1
(neat) 3400, 1640, 1100, 1080, and 830 cm21; H NMR d
7.81–7.64 (m, 4H), 7.39–7.26 (m, 6H), 6.21 (d, J¼1.8 Hz,
1H), 5.85 (d, J¼1.8 Hz, 1H), 5.52 (dt, J¼9.4, 4.6 Hz, 1H),
5.33 (d, J¼9.4 Hz, 1H), 2.42 (d, J¼15.1 Hz, 1H), 2.38 (d,
J¼15.1 Hz, 1H), 1.94 (m, 2H), 1.78–1.42 (m, 4H), 1.21 (s,
1H) and 1.09 (s, 9H); MS (EI) m/z 376 (Mþ, 1%), 319 (10),
279 (92), 199 (100), 135 (40), 77 (18), and 57 (29). Anal.
calcd for C25H32OSi: C, 79.73; H, 8.56. Found: C, 79.85; H,
8.49.
3.3.5. (E)-4-[(tert-Butyldiphenylsilyl)methyl]-1-phenyl-
penta-1,4-dien-3-one (5j). By reaction with cinnamoyl
chloride at 2408C (74%); Rf¼0.27 (hexane/EtOAc, 20:1);
1
IR (CCl4) 1705, 1680, 1600, 1100, 990, and 815 cm21; H
NMR d 7.65–7.62 (m, 4H), 7.46–7.26 (m, 11H), 7.43
(d, J¼15.7 Hz, 1H), 6.88 (d, J¼15.7 Hz, 1H), 5.70 (s, 1H),
5.40 (s, 1H), 2.63 (s, 2H), and 1.10 (s, 9H); 13C NMR d
192.13, 147.19, 142.89, 136.35, 134.93 133.75, 129.94,
129.10, 128.69, 128.05, 127.41, 122.41, 121.74, 27.68,
18.47, and 13.97; MS (EI) m/z 353 (Mþ2But, 100%),
275 (4), 199 (23), 135 (31), 105 (34), and 57 (68). Anal.
calcd for C28H30OSi: C, 81.90; H, 7.36. Found: C, 81.73; H,
7.41.
3.3. tert-Butyldiphenylsilylcupration of allene with tert-
butyldiphenylsilylcopper reagent and reactions with
electrophiles
Allene 1 (1 mmol) was added to a solution of the tert-
butyldiphenylsilylcopper reagent [prepared by mixing tert-
butyldiphenylsilyllithium (1 mmol) and copper (I) cyanide
(1 mmol)] in THF (5 mL). The mixture was cooled at

P. Cuadrado et al. / Tetrahedron 59 (2003) 5855–5859
5859
3.3.6. (E)-4-[(tert-Butyldiphenylsilyl)methyl]-1-phenyl-
penta-1,4-dien-3-ol (5g). Using cinnamaldehyde as an
electrophile (54%); Rf¼0.15 (hexane/EtOAc, 20:1); IR
(CCl4) 3660 sharp, 3400 br, 1645, 1100, and 960 cm21; 1H
NMR d 7.74–7.66 (m, 4H), 7.47–7.14 (m, 11H), 6.33 (d,
J¼15.9 Hz, 1H), 5.96 (dd, J¼15.9, 6.7 Hz, 1H), 5.00 (s,
1H), 4.80 (s, 1H), 4.18 (d, J¼6.7 Hz, 1H), 92.34 (d, J¼14.9,
1H), 2.09 (d, J¼14.9 Hz, 1H), 1.69 (s br, 1H), and 1.06 (s,
9H); 13C NMR d 147.37, 136.33, 136.27, 134.44, 134.25,
130.98, 130.12, 129.26, 128.44, 127.53, 126.46, 110.79,
76.22, 27.73, 18.51, and 15.66; MS (EI) m/z 355 (Mþ2But,
27%), 311 (10), 277 (12), 225 (15), 199 (50), 183 (52), 135
(74), 105 (80), and 57 (100). Anal. calcd for C28H32OSi: C,
81.50; H, 7.82. Found: C, 81.34; H, 7.76.
graphed to give 8 (89%); colorless oil; Rf¼0.63 (hexane); IR
(neat) 1610, 1595, 1580, 1100, 960 and 830 cm21; 1H NMR
d 7.66–7.62 (m, 4H), 7.47–7.19 (m, 11H), 6.75 (dd,
J¼15.6, 10.4 Hz, 1H), 6.64 (d, J¼15.6 Hz, 1H), 6.54 (d,
J¼15.4 Hz, 1H), 6.37 (dd, J¼15.4, 10.4 Hz, 1H), 6.23 (d,
J¼3.1 Hz, 1H), 5.60 (d, J¼3.1 Hz, 1H), and 1.17 (s, 9H);
MS (EI) m/z 337 (Mþ2But, 100), 259 (12), 183 (58), 155
(7), 105 (38), and 57 (19). Anal. Calc. for C28H30Si: C,
85.22; H, 7.66. Found: C, 85.09; H, 7.61.
3.3.11. E-3-(Ethoxycarbonylmethylene)-5-phenylcyclo-
pentene (9). To a solution of AlCl3 (4 mmol) in CH2Cl2
(5 mL) at 2308C was slowly added ClCO2Et (2 mmol) and
stirred for 30 min. Then the alcohol 5g (1 mmol) was added
and the mixture was stirred at this temperature for 90 min,
hydrolyzed with an aqueous solution of ammonium
chloride, extracted with CH2Cl2, dried (MgSO4) and
chromatographed using hexane/CH2Cl2 as eluent to give 9
as major product. Oil (63%); Rf¼0.69 (CH2Cl2); IR (neat)
3.3.7. 4-[(tert-Butyldiphenylsilyl)methyl]-3-phenylpent-
4-enal (5k). Using cinnamaldehyde as an electrophile
(17%); Rf¼0.21 (hexane/EtOAc, 20:1); IR (neat) 1720,
1
1620, 1100, and 865 cm21; H NMR d 9.01 (t, J¼2.3 Hz,
1
1H), 7.65 (m, 4H), 7.41 (m, 6H), 7.28 (m, 3H), 7.03 (m, 2H),
4.91 (s, 1H), 4.76 (s, 1H), 3.23 (t, J¼7.6 Hz, 1H), 2.46 (dd,
J¼2.3, 7.6 Hz, 2H), 2.27 (d, J¼14.5 Hz, 1H), 1.88 (d,
J¼14.5 Hz, 1H), and 1.04 (s, 9H); 13C NMR d 201.34,
147.20, 141.58, 136.19, 134.29, 129.13, 128.37, 127.44,
127.39, 126.66, 110.75, 48.26, 46.35, 27.57, 19.15, and
18.33. MS (EI) m/z 355 (Mþ2But, 25%), 277 (4), 199 (100),
135 (45), 105 (28), and 57 (72). Anal. calcd for C28H32OSi:
C, 81.50; H, 7.82. Found: C, 81.63; H, 7.78.
1715, 1625, and 830 cm21; H NMR d 7.73 (d, J¼5.7 Hz,
1H), 7.66–7.07 (m, 6H), 6.67 (d, J¼5.7 Hz, 1H), 4.38 (q,
J¼7.1 Hz, 2H), 3.52 (dd, J¼10.3, 8.5 Hz, 1H), 3.02 (dd,
J¼10.3, 17.6 Hz, 1H), 2.89 (dd, J¼8.5, 17.6 Hz, 1H), and
1.38 (t, J¼7.1 Hz, 3H); 13C NMR d 168.03, 156.02, 145.31,
135.89, 134.74, 134.16, 130.90, 129.57, 128.03, 61.59,
51.18, 34.50, and 23.20; MS (EI) m/z 228 (Mþ, 2%), 213
(100), 183 (28), 155 (6), 105 (10), and 77 (5). Anal. calcd for
C15H16O2: C, 78.92; H, 7.06. Found: C, 78.79; H, 7.11.
3.3.8. 5-[(tert-Butyldiphenylsilyl)methyl]-4-phenylhex-5-
en-2-one (5l). By adding benzalacetone to the intermediate
of silylcupration (65%); Rf¼0.20 (hexane/EtOAc, 20:1); IR
Acknowledgements
1
(neat) 1710, 1620, 1100, and 860 cm21; H NMR d 7.70–
´
We thank the Spanish Ministerio de Ciencia y Tecnologıa
for financial support (Grant BQU2000-0943).
7.66 (m, 4H), 7.47–7.37 (m, 6H), 7.30–7.21 (m, 3H), 7.07–
7.04 (m, 2H), 4.83 (s, 1H), 4.78 (s, 1H), 3.37 (dd, J¼9.6,
5.3 Hz, 1H), 2.68 (dd, J¼15.6, 9.6, 1H), 2.51 (dd, J¼5.6,
5.3 Hz, 1H), 2.25 (d, J¼14.8 Hz, 1H), 1.92 (d, J¼14.8 Hz,
1H), 1.78 (s, 3H), and 1.06 (s, 9H); 13C NMR d 207.24,
142.30, 136.23, 135.76, 135.13, 134.74, 129.00, 128.39,
128.16, 127.66, 116.10, 50.32, 48.26, 30.61, 26.50, 22.70,
and 18.16; MS (EI) m/z 369 (Mþ2But, 23%), 291 (5), 239
(8), 199 (100), 135 (51), 105 (37), and 43 (79). Anal. calcd
for C29H34OSi: C, 81.64; H, 8.03. Found: C, 81.79; H, 8.08.
References
´
1. Barbero, A.; Cuadrado, P.; Gonzalez, A. M.; Pulido, F. J.;
Fleming, I. J. Chem. Soc. Perkin Trans. I 1991, 2811–2816.
´
2. Barbero, A.; Cuadrado, P.; Fleming, I.; Gonzalez, A. M.; Pulido,
´
F. J.; Sanchez, A. J. Chem. Soc. Perkin Trans. I 1995, 1525–1532.
´
3. Blanco, F. J.; Cuadrado, P.; Gonzalez, A. M.; Pulido, F. J.;
3.3.9. 3-[3-(tert-Butyldiphenylsilyl)prop-1-en-2-yl]cyclo-
hexenone (5m). By reaction with 2-cyclo hexenone (52%);
Rf¼0.30 (hexane/EtOAc, 20:1); IR (CCl4) 1680, 1630, 1100,
and 860 cm21; 1H NMR d 7.75–7.72 (m, 4H), 7.44–7.34 (m,
6H), 4.72 (s, 1H), 4.58 (s, 1H), 2.19 (m, 3H), 2.11 (dd, J¼14.0,
4.4 Hz, 1H), 2.05 (d, J¼14.0 Hz, 1H), 1.86–1.71 (m, 2H),
1.65 (s, 2H), 1.40–1.23 (m, 2H), and 1.08 (s, 9H); 13C NMR d
211.74, 148.96, 135.97, 132.87, 129.55, 127.64, 109.17,
46.78, 44.97, 41.08, 29.66, 26.52, 24.71, 19.26, and 18.50; MS
(EI) m/z 319 (Mþ2But, 17%), 241 (3), 199 (32), 183 (9), 135
(56), 105 (40), 57 (64), 55 (24), and 41 (100). Anal. calcd for
C25H32OSi: C, 79.73; H, 8.56. Found C, 79.87; H, 8.68.
Fleming, I. Tetrahedron Lett. 1994, 35, 8881–8882.
4. For leading references to the reactivity of allyl and vinylsilanes,
see: (a) Chan, T. H.; Fleming, I. Synthesis 1979, 761. (b) Weber,
W. P. Silicon Reagents for Organic Synthesis; Springer: Berlin,
1983; pp 79–108 and 173–201.
5. In the course of our investigations concerning the behavior
toward electrophiles of dimetalated alkenes bearing silicon
groups in a vinylic and allylic position, we have substituted the
allylic tert-butyldiphenylsilyl group in the presence of a vinylic
tert-butyl diphenylsilyl or even a better electrofugal group like
dimethylphenylsilyl. These results will be published as soon as
possible.
6. (a) Trost, B. M.; Coppola, B. P. J. Am. Chem. Soc. 1982, 104,
6879. (b) Schinzer, D. Synthesis 1988, 263.
3.3.10. (E,E)-2-(tert-Butyldiphenylsilyl)-6-phenylhexa-
1,3,5-triene (8). 7c (0.51 g, 1.2 mmol) and a 1% solution
of F3CCO2H in CH2Cl2 (15 mL) were stirred at 2308C for
1 h. The mixture was washed with a 1 M aqueous solution of
NaHCO3, and the organic layer washed with water, dried
(MgSO4) concentrated in vacuo and the residue chromato-
7. (a) Denmark, S. E.; Jones, T. K. J. Am. Chem. Soc. 1982, 104,
2642. (b) Denmark, S. E.; Wallace, M. A.; Walker, C. B. J. Org.
Chem. 1990, 55, 5543, and references cited therein.
`
8. Fleming, I.; Dunogues, J.; Smithers, R. Org. React. 1989, 37,
57–575.