Functionalised allylsilanes from silylcopper reagents and allene. A useful strategy for cyclopentane annulations

Article abstract of DOI:10.1016/S0040-4020(00)00129-0

Silylcupration of allene using phenyldimethylsilylcopper or t- butyldiphenylsilylcopper followed by reaction with α,β-unsaturated acyl chlorides, aldehydes or ketones affords allylsilane-containing divinyl ketones and oxoallylsilanes, respectively. They u

Full text of DOI:10.1016/S0040-4020(00)00129-0

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 2739±2751
Functionalised Allylsilanes from Silylcopper Reagents and Allene.
A Useful Strategy for Cyclopentane Annulations
*
Â
Asuncion Barbero, Carlos Garcõa and Francisco J. Pulido
 Â
Departamento de Quõmica Organica, Universidad de Valladolid, 47011 Valladolid, Spain
Received 15 September 1999; revised 6 January 2000; accepted 13 January 2000
AbstractÐSilylcupration of allene using phenyldimethylsilylcopper or t-butyldiphenylsilylcopper followed by reaction with a,b-unsatu-
rated acyl chlorides, aldehydes or ketones affords allylsilane-containing divinyl ketones and oxoallylsilanes, respectively. They undergo
highly stereocontrolled silicon-assisted intramolecular cyclizations when treated with protic or Lewis acid leading to cyclopentane
ring-formation. q 2000 Elsevier Science Ltd. All rights reserved.
Ten years ago, we reported the stoichiometric silylcupration
of allenes for the ®rst time.1 Since then the silylcupration of
allenes has become a powerful tool for the synthesis of
vinyl- and allylsilanes.2±6 Moreover, the high versatility
that allyl- and vinylsilanes show in synthetic organic
chemistry as masked carbon nucleophiles has attracted
much attention among organic chemists.7 The readily
prepared lithium bis(phenyldimethylsilyl)cuprate1 2 and
other cuprates react stereoselectively8 with allenes by syn
addition of the silyl±copper pair to one of the double bonds
to give, after addition of an electrophile, allyl- or vinyl-
silanes differently functionalised. Addition is usually regio-
selective and the formation of allyl- or vinylsilanes depends
on the substitution pattern of the allene. In a recent review9
we reported the reactivity of higher order silyl- and stannyl-
cuprates toward unactivated allenes and acetylenes showing
the scope of the reaction and the synthetic applicability of
our methodology. In particular, the reaction of 2 with allene
1 itself is not temperature dependent leading invariably to
vinylsilanes at low (2788C) and high (08C) temperatures1,2
(Scheme 1). More recently, we noted10 that phenyldimethyl-
silyl±copper 3 prepared by mixing one equivalent of
phenyldimethylsilyl±lithium and one equivalent of
copper(I) cyanide reacted with 1 at 2408C in THF showing
a regiochemistry opposite to that of the corresponding
higher order silylcuprate 2. This route allowed us to prepare
a wide variety of functionalised allylsilanes (Scheme 1).
Contrarily to 2, the silylcopper reagent 3 shows a tempera-
ture dependence when reacting with allene 1 giving allyl-
silanes after protonation at 2408C, but vinylsilanes at 08C
(Scheme 1).
Silylcupration reactions are a particular example of a more
general procedure known as metallo-metallation reactions.
They are a relatively new class of reactions closely related
to the better-known hydrometallations and carbometalla-
tions. Although known for the addition of two different
main group metals to a triple bond,11 stoichiometric
metallo-metallations usually involve the addition of copper
to one end of a triple bond and a silyl,12 gerrmyl13 or
stannyl14 group to the other. Addition of the bimetallic
species generates two adjacent nucleophilic carbons which
react sequentially with a wide range of electrophiles due to
their well differentiated reactivity. The stereochemistry of
Scheme 1.
Keywords: silylcupration; allene; allylsilane; cyclization.
* Corresponding author. Tel.: 34-983-423210; fax: 34-983-423013; e-mail: pulido@qo.uva.es
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00129-0

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A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
metallo-metallations of multiple bonds has been abundantly
proved to be syn8,15 but occasionally the overall process is
anti11,13,16 rather than syn. Metallo-metallations of double
bonds are much less common but are known for the tran-
sition metal-catalysed addition of silicon±silicon bonds
to 1,3-dienes,17 for the transition metal-catalysed addition
of silicon±magnesium,18 silicon±aluminium18 and silicon±
zinc18 bonds to allenes, for the stoichiometric silyl-
zirconation19 of allenes, for the platinum-catalysed
silylsilylation20 of double bonds and we21 and others22
reported the stoichiometric stannylcupration of allenes and
acetylenes.
Scheme 2.

A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
2741
Scheme 3.
In this paper we report in full the scope and synthetic appli-
cations of the silylcupration of allene using silylcopper
reagents. We provide details of the work published in pre-
liminary form10 and we also extend the reaction to other
bulkier silylcopper reagents as t-butyldiphenylsilyl±copper.
Moreover, we describe several new strategies for ring
formation via allylsilane intramolecular cyclization discuss-
ing factors controlling the stereochemistry.
Compound 21 undergoes isomerization to the trans-isomer
in 97% yield, when stirred with a 0.5 M solution of NaOH in
H2O/EtOH/THF. Intermediate 5 is regiochemically stable at
temperatures around 2408C however, as was mentioned
before (Scheme 1), near 08C interconversion of 5 to the
corresponding vinylsilane±allylcopper 22 occurs rapidly.
Therefore, care must be taken with the temperature control
of the process to avoid that the reversibility of the reaction
may in¯uence the outcome. This effect can be seen in the
reaction of 5-iodopentan-2-one with 1,2-propadiene and the
silylcopper reagent 3 (Scheme 3). In standard conditions
(THF, BF3, 240 to 08C) the reaction leads to the formation
of the anomalous tetrahydrofuran 23 (Scheme 3). This result
suggests that reaction of the iodoketone with intermediate 5
at 2408C proceeds very slowly. As the temperature
increases, intermediate 5 equilibrates to the vinylsilane±
allylcopper intermediate 22, then addition of 22 to the
carbonyl group followed by intramolecular nucleophilic
displacement of iodine gives 23 (Scheme 3).
Reaction with Electrophiles
The silylcopper reagent 3, prepared by stirring one equiva-
lent of phenyldimethylsilyl±lithium12a and copper(I)
cyanide at 08C in THF for 30 min, reacts with 1,2-propa-
diene (allene) 1 at 2408C in THF for 1 h leading to the
allylsilane±vinylcopper intermediate 5. In addition to
proton, several more common carbon electrophiles react
with 5 at temperatures between 2408C and 08C giving
good yields of allylsilanes 6±21 (Scheme 2).
Although the behaviour of allylsilanes toward carbonyl
compounds can be predicted, some anomalous cyclizations,
mechanistically not very well set up, have also been
observed and are at present, a matter of study. Thus, allyl-
silane 8 reacts with butyraldehyde and benzalacetone under
Lewis acid activation by TiCl4 to yield the expected alcohol
24 and the unexpected oxetane 25 and chlorocyclohexanol
The procedure herein described is quite general, thus
providing an ef®cient entry to the preparation of function-
alised allylsilanes. Reactions leading to the formation of
16±21 were carried out in the presence of BF3 for better
yields. a,b-Unsaturated aldehydes and ketones undergo
conjugate addition as the only observed reaction.
Scheme 4.

2742
A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
Scheme 5.
26 (Scheme 4). Although we defer any de®nitive statements
regarding mechanisms, a plausible pathway leading to 25
and 26 has been outlined below (Scheme 4).
not need to be described in this paper. Consequently, it
could be thought that the use of 28 has no advantages
over the bis(silylcuprate); however, reaction of 28 with
allene and a,b-unsaturated oxocompounds shows a different
reactivity pattern. Thus, we showed before4 that a,b-
unsaturated oxocompounds undergo carbonyl addition
when reacting with the intermediate cuprate resulting
from addition of lithium bis(t-butyldiphenylsilyl)cuprate
to allene whereas reaction of 29 with the same enones, in
the presence of BF3, affords the allylsilanes 30-32 resulting
from conjugate addition (Scheme 5). Reaction of 29 with
a,b-unsaturated acyl chlorides gives the divinylketones 33
and 34 (Scheme 5).
The source of chloride anion for the formation of 26 is
matter of discussion. It could be due to TiCl4 impurities
(HCl) although bidistilled and puri®ed TiCl4 gives similar
results. This leaves only the TiCl4 as the source of chlorine.
It should be noted that ketone 27 was never isolated.
t-Butyldiphenylsilyl±copper 28 was prepared as before by
mixing one equivalent of t-butyldiphenylsilyl±lithium23 and
copper(I) cyanide at 08C. It reacts with allene at any
temperature between 278 and 08C leading invariably to
allylsilanes after quenching with common electrophiles
(proton, alkyl halides, epoxides, acyl chlorides, etc). Now
intermediate 29 seems to be the only species present in a
long range of temperatures (Scheme 5). These results are
quite similar to those we reported for the lithium bis(t-butyl-
diphenylsilyl)cuprate some time ago4 and therefore, they do
Knochel Homologations
Recently Knochel et al.24 published an excellent method for
the homologation of vinylic organocopper reagents to
allylic copper±zinc organometallics by reaction of the
Scheme 6.

A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
2743
Scheme 7.
former with (iodomethyl)zinc iodide. We wondered how far
this possibility could be taken with our vinylcopper inter-
mediates 5 and 29. Obviously if the Knochel homologation
can be extended to the general reaction, this would increase
signi®cantly the synthetic versatility of our methodology.
We now report examples of these possibilities. Reaction
of intermediate 29 with (iodomethyl)zinc iodide in THF at
2508C followed by addition of ketones or enones gives the
homoallyllic alcohols 35±37 resulting from carbonyl addi-
tion of the homologated copper±zinc organometallic
reagent 40 (Scheme 6). Conjugate addition products were
not isolated. On the contrary, reaction of the phenyl-
dimethylsilyl analogue 5 in the same conditions leads to
poor yields of the alcohols 38 and 39 (Scheme 6). All efforts
to improve yields were unsuccessful.
using the classical Nazarov25 cyclization reaction. A major
limitation of the general method is the lack of control over
the position of the double bond in the cyclopentenone
moiety. In recent years, Denmark26 and others found that
silicon-assisted Nazarov reactions were an excellent solu-
tion to this problem. In most known examples of this type of
reaction a directing vinylsilane group is involved, and we
now report representative examples of silicon directed
Nazarov reactions of divinyl ketones bearing an allylsilane
unit. Silyldienones 12±14, 33 and 34 are readily prepared,
using our methodology, by reaction of a,b-unsaturated acyl
chlorides with intermediates 5 and 29 (Schemes 2 and 5).
Cyclization of the former divinyl ketones in the presence of
tri¯uoroacetic acid (TFA)/THF affords good yields of the
methylenecyclopentanones 42±46 (Scheme 7). It should be
noted that in the t-butyldiphenylsilyl series the silyl group is
not removed during cyclization.
It is uncertain whether homologation of 5 occurs in little
extent or the reactivity of 41 toward ketones is low.
However, after quenching with ammonium chloride solu-
tion much vinylsilane 4 is recovered, which suggests that
homologation of 5 is not complete.
We tested different protic and Lewis acids (TFA, FeCl3,
TiCl4, EtAlCl2, BF3), solvents (THF, CH2Cl2) and tempera-
tures (220 to 408C) for the best conditions. Of all the acids
examined TFA (3 equivalents) in THF has proven to be the
most ef®cient. The procedure herein described constitutes a
convenient method for the preparation of conjugated
methylenecyclopentanones where the strategic placement of
the silyl group directs the introduction of the new exocyclic
Directed Nazarov Reactions
Cyclopentenone annelations have been largely achieved
Scheme 8.

2744
A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
Scheme 9.
Scheme 10.

A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
2745
Scheme 11.
double bond. The key to this modi®cation of the classical
Nazarov sense is the well-documented ability of silicon to
stabilize b-carbocations.7 In the studied examples, the
so-called b-effect of the silyl moiety exerts a perfect control
over the electrocyclization of the starting divinyl ketones
(Scheme 8). A unique feature of this cyclization is the
formation of 45 and 46 in which the silyl group is retained.
This result might be due to the low electrofugacity of the
t-butyldiphenylsilyl group compared to the phenyldimethyl-
silyl group. Moreover, the higher electronegativity of
t-butyldiphenylsilyl group enhances the acidity of the
hydrogens alpha to silicon, thus assuring elimination in
the observed sense (Scheme 8). The E geometry of the
silyl-substituted double bond was assigned by NOESY
and COSY experiments.
cuprate 5 (44!48) and ®nally allylsilane terminated cycli-
zation (48!55) might be expeditiously applied to a connec-
tive annulation procedure for the synthesis of fused
cis,anti,cis-tricyclopentanoids, thus providing an easy
approach to linearly fused triquinane natural products.29
High levels of stereocontrol were found in all cyclizations
carried out, with the exception of 53 which was isolated as a
mixture of epimeric alcohols in 3:1 ratio (Scheme 10).
The stereochemistry observed in the formation of mono-
cyclic methylenecyclopentanols (NOESY) might indicate
a preference for the transition state depicted in Scheme
11, where bulky groups attain an equatorial conformation
which minimizes steric repulsions. However, formation of
bridged bicyclic methylenecyclopentanols 51 and 52
requires an axially arranged allylsilane unit for the ®nal
cyclization step (Scheme 11). Obtention of cis-fused
geometry for the bi- and tricyclopentanols 54 and 55 is
unexceptional in view of their higher thermodynamic
stability. As was observed before for the directed Nazarov
reactions, the t-butyldiphenylsilyl group may not be the
electrofugal group following cyclization. Formation of 56
and 57 seems to be consistent with the mechanism outlined
below (Scheme 11). This result is remarkable because the
t-butyldiphenylsilyl moiety is still capable of undergoing
electrophilic substitution,12b thus making this reaction
presumably more useful than we expected before.
Allylsilane Terminated Cyclizations
We have shown in Scheme 2 and 5 the reaction of allyl-
silane±vinylcopper intermediates 5 and 29 with a,b-
unsaturated aldehydes and ketones. Exocyclic a,b-unsatu-
rated enones 42 and 44 resulting from directed Nazarov
cyclization (Scheme 7) react even faster than endocyclic
or acyclic enones, giving good yields of 47 and 48 with a
high degree of stereocontrol (Scheme 9). Oxoallylsilanes
16, 17, 19±21, 47 and 48 containing a nucleophilic allyl-
silane unit and an electrophilic carbonyl moiety, undergo
intramolecular allylsilane terminated cyclization27 when
treated with a Lewis acid leading to methylenecyclo-
pentan-1-ols 49±55 (Scheme 10). Cyclization of the oxo-
allylsilanes 30 and 31 bearing the t-butyldiphenylsilyl group
occurs without loss of the silyl moiety giving cyclopenten-
1-ols 56 and 57 (Scheme 10). For the general procedure,
TiCl4 was ®rst used but in many of the studied reactions
better yields are obtained if EtAlCl2 is used instead. The
stereochemistry of the resulting compounds has been
assigned on the basis of the observed NMR coupling
constants, NOESY experiments and from previously
reported data.28 The easy access to exocyclic methylene-
cyclopentanes is one of the features of this methodology.
The methylenecyclopentanol moiety is very common in
some terpene families10b moreover, the previous results
suggest that a combination of the directed Nazarov reaction
(14!44), followed by conjugate addition of intermediate
We conclude that reaction of allene with silylcopper
reagents followed by addition of carbonyl derivatives is a
simple and ef®cient methodology for the synthesis of a large
number of allylsilanes with a wide variety of substitution
patterns. They undergo highly stereocontrolled intra-
molecular cyclizations allowing the design and develop-
ment of new strategies for cyclopentane annulation.
Moreover, a simple protocol for triquinane systems based
on the consecutive application of directed Nazarov reaction
and allylsilane terminated cyclization has been outlined.
Experimental
Allene 1 was supplied by Air Liquide in lecture bottles.
Compounds 4, 6, 10, 17 and 50 were described in previous
papers.1,10b

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A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
Silylcupration of allene. Preparation of intermediate 5
30.1, 23.7, 22.5, 14.3, 23.1; MS(EI) m/z: 232 (M1,
0.4%), 217, 189, 135 (100). Anal. Calcd for C15H24Si: C,
77.51; H, 10.41. Found: C, 77.73; H, 10.52.
A solution of phenyldimethylsilyl±lithium12a (3 mmol)
prepared in THF (3 ml) was added by syringe to a stirred
suspension of copper(I) cyanide (269 mg, 3 mmol) in THF
(5 ml) at 08C. The resulting black mixture was stirred at this
temperature for an additional period of 30 min, and then
used immediately. The solution of phenyldimethylsilyl±
copper 3 (3 mmol) in THF (8 ml) was cooled at 2408C
and a slight excess of allene 1 was added from a balloon.
The mixture was stirred for 1 h at this temperature and the
reagent 5 used immediately.
2-Dimethyl(phenyl)silylmethylpenta-1,4-diene (8). Oil,
90%; IR (neat): 1625, 1250, 1110, 985, 922, 875, 832; H
1
NMR: 7.58±7.36 (m, 5H), 5.79 (ddt, Jˆ10.1 Hz, 17.1 and
7.1, 1H), 5.06 (d with ®ne couplings, Jˆ10.1 Hz, 1H), 4.99
(d with ®ne couplings, Jˆ17.1 Hz, 1H), 4.67 (s with ®ne
couplings, 1H), 4.60 (s with ®ne couplings, 1H), 2.62 (d
with ®ne couplings, Jˆ7.1 Hz, 2H), 1.83 (s, 2H), 0.37 (s,
6H); 13C NMR: 145.4, 138.9, 136.4, 133.6, 129.0, 127.7,
116.1, 108.8, 42.8, 25.7, 22.9; MS(EI) m/z: 216 (M1,
0.14%), 201, 135 (100). Anal. Calcd for C14H20Si: C,
77.71; H, 9.32. Found: C, 78.02; H, 9.51.
Silylcupration of allene. Preparation of intermediate 29
A
solution of t-butyldiphenylsilyl-lithium23 (3 mmol)
3-Dimethyl(phenyl)silylmethylbut-3-en-1-ol (9). Oil,
57%; IR (neat): 3260, 1633, 1252, 1110, 1060, 878, 831;
1H NMR: 7.54±7.34 (m, 5H), 4.71 (s, 1H), 4.68 (s, 1H), 3.62
(t, Jˆ6.2 Hz, 2H), 2.11 (t, Jˆ6.2 Hz, 2H), 1.78 (s, 2H), 1.51
(br s, 1H), 0.33 (s, 6H); 13C NMR: 143.3, 138.6, 133.5,
129.1, 127.8, 110.5, 59.9, 41.1, 25.6, 23.0; MS(EI) m/z:
220 (M1, 0.24%), 205, 202, 135 (100). Anal. Calcd for
C13H20SiO: C, 70.85; H, 9.15. Found: C, 70.91; H, 9.13.
prepared in THF (3 ml) was added by syringe to a stirred
suspension of copper(I) cyanide (269 mg, 3 mmol) in THF
(5 ml) at 08C. The resulting green±black mixture was stirred
at this temperature for 30 min, and then used immediately.
The solution of t-butyldiphenylsilyl±copper 28 (3 mmol) in
THF (8 ml) was cooled at 2788C and a slight excess of
allene 1 was added from a balloon. The mixture was allowed
to warm up to 08C with continuous stirring for 1 h. The
reagent 29 was used immediately.
3-Dimethyl(phenyl)silylmethylbut-3-en-2-one (11). Oil,
79%; IR (neat): 1672, 1610, 1243, 1113, 935, 836; H
1
Reaction of intermediate 5 with electrophiles
NMR: 7.55±7.34 (m, 5H), 5.83 (s, 1H), 5.51 (s, 1H), 2.26
(s, 3H), 2.04 (s, 2H), 0.26 (s, 6H); 13C NMR: 199.4, 146.7,
138.3, 133.6, 129.0, 127.6, 122.7, 25.3, 19.8, 23.2; MS(EI)
m/z: 218 (M1, 5%), 203, 175, 135 (100). Anal. Calcd for
C13H18SiO: C, 71.50; H, 8.31. Found: C, 71.73; H, 8.46.
Procedure 1: methyl iodide (10 mmol), butyl iodide
(10 mmol), allyl bromide (6 mmol), ethylene oxide
(4 mmol), iodine (3.6 mmol), acetyl chloride (3.6 mmol),
cinnamoyl chloride (3.6 mmol), p-metoxycinnamoyl chloride
(3.6 mmol), cyclopent-1-enecarbonyl chloride (3.6 mmol) or
cyclohex-1-enecarbonyl chloride (3.6 mmol) was added to
the cuprate reagent 5 (3 mmol) at 2408C and the resulting
solution was kept at this temperature for 1 h. After gentle
warming to 08C (over 0.5 h) the mixture was quenched
with saturated ammonium chloride solution and extracted
twice with Et2O. The organic layer was dried over MgSO4
and rotoevaporated. Puri®cation by ¯ash-chromatography
(EtOAc:hexanes) gave the allylsilanes 6±15 (Scheme 2).
(E)-1-Phenyl-4-dimethyl(phenyl)silylmethylpenta-1,4-
dien-3-one (12). Oil, 76%; IR (neat): 1692, 1661, 1604,
1250, 1110, 982, 925, 837; H NMR: 7.60±7.34 (m, 10H),
1
7.58 (d, Jˆ16.1 Hz, 1H), 7.28 (d, Jˆ16.1 Hz, 1H), 5.92 (s,
1H), 5.58 (s, 1H), 2.22 (s, 2H), 0.34 (s, 6H); 13C NMR:
191.4, 147.5, 143.2, 138.3, 134.9, 133.6, 130.1, 129.0,
128.8, 128.1, 127.6, 121.5, 121.3, 20.9, 23.1; MS(EI)
m/z: 306 (M1, 9%), 291, 229, 135 (100). Anal. Calcd for
C20H22SiO: C, 78.38; H, 7.24. Found: C, 78.75; H, 7.45
Procedure 2: BF3´Et2O (0.38 ml, 3 mmol) was added at
2788C to a stirred solution of cuprate 5 (3 mmol) and the
mixture stirred for 10 min at this temperature, then
3.6 mmol of cinnamaldehyde, benzalacetone, chal-
cone, 3-methylcyclopent-2-en-1-one, cyclohex-2-en-1-one,
1-acetylcyclohex-1-ene or 5-iodopentan-2-one in THF
(5 ml) were added dropwise at 2408C and the resulting
mixture was kept at this temperature for 1 h. After gentle
warming to 08C (over 0.5 h) the mixture was quenched as
before and extracted with Et2O. The organic phase was
dried, evaporated and chromatographed (EtOAc:hexanes)
to give the allylsilanes 16±21 and the vinylsilane 23
(Schemes 2 and 3).
(E)-1-(4-Methoxyphenyl)-4-dimethyl(phenyl)silylmethyl-
penta-1,4-dien-3-one (13). Viscous oil, 83%; IR (Cl4C):
1650, 1633, 1601, 1257, 1115, 978, 915; H NMR: 7.58±
7.34 (m, 8H), 7.13 (d, Jˆ15.7 Hz, 1H), 6.92 (d, Jˆ8.9 Hz,
2H), 5.86 (s, 1H), 5.51 (s, 1H), 3.86 (s, 3H), 2.17 (s with ®ne
couplings, 2H), 0.29 (s, 6H); 13C NMR: 191.6, 161.4, 147.6,
143.2, 138.5, 133.7, 130.0, 129.1, 127.7, 127.5, 121.1,
119.1, 114.3, 55.3, 21.1, 23.2; MS(EI) m/z: 336 (M1,
40%), 321, 305, 258, 135 (100).
1
1-(Cyclopent-1-en-1-yl)-2-dimethyl(phenyl)silylmethyl-
prop-2-en-1-one (14). Oil, 85%; IR (neat): 1702, 1630,
1
1600, 1250, 1113, 927, 834; H NMR: 7.53±7.33 (m, 5H),
6.39 (m, 1H), 5.51 (s, 1H), 5.36 (s, 1H), 2.59±2.48 (m, 4H),
2.14 (s, 2H), 1.91 (quintet, Jˆ7.5 Hz, 2H), 0.28 (s, 6H);
13C NMR: 195.5, 146.3, 144.4, 143.7, 138.3, 133.7,
129.0, 127.6, 120.9, 33.9, 31.7, 22.6, 21.7, 23.1; MS(EI)
m/z: 270 (M1, 19%), 255, 241, 135 (100). Anal. Calcd
for C17H22SiO: C, 75.50; H, 8.20. Found: C, 75.29; H,
8.08.
2-Dimethyl(phenyl)silylmethylhex-1-ene (7). Oil, 64%;
IR (neat): 1629, 1251, 1110, 885, 830; H NMR (CDCl3,
1
300 MHz): 7.60±7.38 (m, 5H), 4.67 (s with ®ne couplings,
1H), 4.59 (s with ®ne couplings, 1H), 1.91 (t, Jˆ7.2 Hz,
2H), 1.83 (s with ®ne couplings, 2H), 1.47±1.25 (m, 4H),
0.92 (t, Jˆ7.3 Hz, 3H), 0.35 (s, 6H); 13C NMR (CDCl3,
75 MHz): 140.1, 138.5, 133.2, 129.6, 127.4, 113.3, 37.6,

A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
2747
1-(Cyclohex-1-en-1-yl)-2-dimethyl(phenyl)silylmethyl-
prop-2-en-1-one (15). Oil, 90%; IR (neat): 1703, 1638,
23.4; MS(EI) m/z: 300 (M1, 0.7%), 285, 257, 223, 135
(100). Anal. Calcd for C19H28SiO: C, 75.94; H, 9.39.
Found: C, 76.05; H, 9.32.
1
1610, 1255, 1116, 930, 839; H NMR: 7.55±7.34 (m, 5H),
6.49 (m, 1H), 5.35 (s, 1H), 5.31 (s, 1H), 2.23±2.14 (m, 4H),
2.14 (s, 2H), 1.65±1.59 (m, 4H), 0.31 (s, 6H); 13C NMR:
199.4, 145.2, 141.1, 138.3, 137.7, 133.7, 129.0, 127.6,
120.7, 25.8, 23.9, 22.2, 22.0, 21.6, 23.3; MS(EI) m/z: 284
(M1, 86%), 269, 255, 210, 135 (100). Anal. Calcd for
C18H24SiO: C, 76.00; H, 8.50. Found: 75.86; H, 8.58.
2-Methyl-2-[2-dimethyl(phenyl)silylprop-2-en-1-yl]tetra-
hydrofuran (23). Oil, 61%; IR (neat): 1605, 1595, 1243,
1115, 1047, 921; 1H NMR: 7.55±7.30 (m, 5H), 5.85 (s with
®ne couplings, 1H), 5.59 (s with ®ne couplings, 1H), 3.78±
3.52 (m, 2H), 2.41 (d with ®ne couplings, Jˆ15.1 Hz, 1H),
2.34 (d with ®ne couplings, Jˆ15.1 Hz, 1H), 1.92±1.51 (m,
4H), 1.12 (s, 3H), 0.40 (s, 3H), 0.38 (s, 3H); 13C NMR:
147.2, 139.0, 134.0, 130.7, 128.6, 127.5, 82.6, 66.7, 46.6,
36.9, 26.1, 25.8, 22.1, 22.6; MS(EI) m/z: 260 (M1, 0.12%),
245, 183, 135, 85 (100). Anal. Calcd for C16H24SiO: C,
73.79; H, 9.29. Found: C, 74.15; H, 9.50.
3-Phenyl-4-dimethyl(phenyl)silylmethylpent-4-enal (16).
Oil, 90%; IR (neat): 2731, 2833, 1734, 1642, 1253, 1110,
889, 833; 1H NMR: 9.46 (dd, Jˆ1.8 Hz and 2.6, 1H), 7.59±
7.11 (m, 10H), 4.85 (s, 1H), 4.81 (s, 1H), 3.51 (t, Jˆ7.6 Hz,
1H), 2.82 (ddd, Jˆ16.7, 2.6 and 7.6 Hz, 1H), 2.62 (ddd,
Jˆ16.7, 1.8 and 7.6 Hz, 1H), 1.78 (d, Jˆ13.9 Hz, 1H),
1.59 (d, Jˆ13.9 Hz, 1H), 0.41 (s, 3H), 0.35 (s, 3H); 13C
NMR: 201.4, 147.5, 142.1, 138.7, 133.7, 129.2, 128.6,
128.1, 127.9, 126.8, 108.9, 48.5, 46.5, 25.8, 22.7, 23.3;
MS(EI) m/z: 308 (M1, 0.4%), 293, 230, 204, 156, 135
(100). Anal. Calcd for C20H24SiO: C, 77.87; H, 7.84.
Found: C, 77.75; H, 7.86.
Reaction of intermediate 29 with electrophiles
Reaction of 29 (3 mmol) with cinnamoyl chloride
(3.6 mmol) or p-metoxycinnamoyl chloride (3.6 mmol)
was carried out in the same conditions as described before
in Procedure 1, leading to 33 and 34 (Scheme 5). Reaction of
29 (3 mmol) with cinnamaldehyde (3.6 mmol), benzalacetone
(3.6 mmol) or cyclohex-2-en-1-one (3.6 mmol) was carried
out in the presence of BF3 in the same conditions as described
above in Procedure 2, leading to 30±32 (Scheme 5).
1,3-Diphenyl-4-dimethyl(phenyl)silylmethylpent-4-en-1-
one (18). Viscous oil, 78%; IR (neat): 1682, 1628, 1258,
1111, 877, 834; 1H NMR: 7.89±7.15 (m, 15H), 4.81 (s, 1H),
4.74 (s, 1H), 3.90 (t, Jˆ7.2 Hz, 1H), 3.51 (dd, Jˆ16.7 and
7.2 Hz, 1H), 3.23 (dd, Jˆ16.7 and 7.2 Hz, 1H), 1.77 (d,
Jˆ13.9 Hz, 1H), 1.61 (d, Jˆ13.9 Hz, 1H), 0.41 (s, 3H),
0.34 (s, 3H); 13C NMR: 198.2, 148.2, 142.9, 139.0, 137.2,
133.7, 132.8, 128.9, 128.5, 128.3, 128.1, 127.9, 127.7,
126.5, 108.0, 47.6, 43.8, 25.9, 22.9, 22.7; MS(EI) m/z:
384 (M1, 0.3%), 369, 307, 279, 135 (100).
3-Phenyl-4-tert-butyl(diphenyl)silylmethylpent-4-enal
(30). Oil, 80%; IR (neat): 2826, 2737, 1728, 1625, 1110,
882; 1H NMR: 9.01 (t, Jˆ2.4 Hz, 1H), 7.69±7.02 (m, 15H),
4.93 (s, 1H), 4.77 (s, 1H), 3.24 (t, Jˆ7.6 Hz, 1H), 2.47 (dd,
Jˆ2.4 and 7.6 Hz, 2H), 2.28 (d, Jˆ14.5 Hz, 1H), 1.87 (d,
Jˆ14.5 Hz, 1H), 1.05 (s, 9H); 13C NMR: 201.7, 147.4,
141.7, 136.7, 136.3, 134.5, 134.0, 129.3, 129.1, 128.5,
128.0, 127.6, 127.5, 126,8, 110.9, 48.4, 46.5, 27.7, 19.3,
18.5; MS(EI) m/z: 412 (M1, 0.1%), 397, 395, 355, 335,
199 (100). Anal. Calcd for C28H32SiO: C, 81.50; H, 7.82.
Found: C, 81.78; H, 7.99.
3-Methyl-3-[3-dimethyl(phenyl)silylprop-1-en-2-yl]cyclo-
pentan-1-one (19). Oil, 88%; IR (neat): 1742, 1618, 1249,
1108, 875, 830; 1H NMR: 7.56±7.35 (m, 5H), 4.76 (s, 1H),
4.67 (s, 1H), 2.34 (d, Jˆ17.7 Hz, 1H), 2.29±1.71 (m, 5H),
1.78 (s, 2H), 1.12 (s, 3H), 0.38 (s, 3H), 0.37 (s, 3H); 13C
NMR: 218.9, 151.3, 139.1, 133.6, 129.1, 127.8, 108.4, 51.1,
45.9, 36.5, 33.6, 25.7, 20.4, 22.3; MS(EI) m/z: 272 (M1,
1%), 257, 244, 135 (100). Anal. Calcd for C17H24SiO: C,
74.94; H, 8.88. Found: C, 75.26; H, 9.13.
4-Phenyl-5-tert-butyl(diphenyl)silylmethylhex-5-en-2-
one (31). Oil, 85%; IR (neat): 1723, 1633, 1112, 875; H
1
NMR: 7.68±7.03 (m, 15H), 4.82 (s, 1H), 4.78 (s, 1H), 3.36
(dd, Jˆ5.4 and 9.5 Hz, 1H), 2.66 (dd, Jˆ15.6 and 9.5 Hz,
1H), 2.52 (dd, Jˆ15.6 and 5.4 Hz, 1H), 2.23 (d, Jˆ14.7 Hz,
1H), 1.91 (d, Jˆ14.7 Hz, 1H), 1.81 (s, 3H), 1.05 (s, 9H); 13C
NMR: 207.1, 148.0, 142.2, 136.4, 136.3, 134.6, 134.3,
129.2, 129.0, 128.3, 128.1, 127.5(2C), 126.6, 110.1, 48.8,
47.9, 30.0, 27.7, 19.2, 18.5; MS(EI) m/z: 426 (M1, 0.1%),
369, 239, 199 (100).
3-[3-Dimethyl(phenyl)silylprop-1-en-2-yl]cyclohexan-1-
one (20). Oil, 77%; IR (neat): 1714, 1631, 1253, 1109, 880,
841; 1H NMR: 7.55±7.33 (m, 5H), 4.65 (s with ®ne
couplings, 1H), 4.61 (s with ®ne couplings, 1H), 2.42±
1.82 (m, 7H), 1.78 (s with ®ne couplings, 2H), 1.49±1.40
(m, 2H), 0.32 (s, 6H); 13C NMR: 211.6, 149.2, 138.5, 133.5,
129.1, 127.7, 107.2, 47.0, 45.4, 41.2, 30.3, 25.1, 25.0, 23.1;
MS(EI) m/z: 272 (M1, 2%), 257, 229, 135 (100). Anal.
Calcd for C17H24SiO: C, 74.94; H, 8.88. Found: C, 75.15;
H, 8.98.
3-[3-tert-Butyl(diphenyl)silylprop-1-en-2-yl]cyclohexan-
1-one (32). Oil, 87%; IR (neat): 1697, 1642, 1111, 866; 1H
NMR: 7.75±7.34 (m, 10H), 4.72 (s, 1H), 4.58 (s, 1H), 2.29±
2.18 (m, 3H), 2.15 (dd, Jˆ14.0 and 4.4 Hz, 1H), 2.05 (d,
Jˆ14.0 Hz, 1H), 1.86±1.71 (m, 2H), 1.65 (s, 2H), 1.40±
1.23 (m, 2H), 1.08 (s, 9H); 13C NMR: 211.7, 149.0, 136.0,
132.9, 129.6, 127.6, 109.2, 46.8, 45.1, 41.1, 29.7, 26.5, 24.7,
19.3, 18.5; MS(EI) m/z: 376 (M1, 0.2%), 319, 241, 239, 199,
135, 41 (100). Anal. Calcd for C25H32SiO: C, 79.73; H, 8.56.
Found: C, 79.80; H, 8.53.
cis-1-Acetyl-2-[3-dimethyl(phenyl)silylprop-1-en-2-yl]-
cyclohexane (21). White crystals mpˆ50±518C (hexane),
1
85%; IR (Cl4C): 1709, 1633, 1255, 1113, 881; H NMR:
7.57±7.35 m, 5H), 4.65 (s, 1H), 4.59 (s, 1H), 2.93 (q,
Jˆ4.5 Hz, 1H), 2.02 (s, 3H), 1.96±1.29 (m, 9H), 1.88 (d,
Jˆ13.7 Hz, 1H), 1.76 (d, Jˆ13.7, 1H), 0.33 (s, 3H), 0.31 (s,
3H); 13C NMR: 211.7, 147.9, 138.8, 133.5, 129.0, 127.7,
108.8, 48.7, 45.7, 31.7, 27.5, 26.3, 25.8, 25.5, 21.2, 22.9,
(E)-1-Phenyl-4-tert-butyl(diphenyl)silylmethylpenta-1,4-
dien-3-one (33). Oil, 79%; IR (neat): 1669, 1600, 1110,

2748
A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
986, 927; 1H NMR: 7.65±7.32 (m, 15H), 7.44 (d,
Jˆ15.8 Hz, 1H), 6.89 (d, Jˆ15.8 Hz, 1H), 5.71 (s, 1H),
5.41 (s, 1H), 2.64 (s, 2H), 1.11 (s, 9H); 13C NMR: 192.2,
147.2, 142.9, 136.4, 135.0, 133.8, 130.0, 129.1, 128.7,
128.1, 127.4, 122.4, 121.8, 27.7, 18.5, 14.0; MS(EI) m/z:
410 (M1, 0.15%), 353 (100), 199, 105. Anal. Calcd for
C28H30SiO: C, 81.90; H, 7.36. Found: C, 82.11; H, 7.48.
1.27 (s, 3H); 13C NMR: 145.0, 128.5, 127.0, 126.5, 132.2,
119.7, 79.4, 70.4, 51.0, 48.2, 46.3, 46.0, 35.3, 31.1; MS(EI)
m/z: 264 and 266 (M1 and M12, 0.4%), 246 and 248, 211,
205 and 207, 169, 129, 91, 77, 43 (100); Found: M1-18,
246.1177. C16H19Cl requires: 246.1175. Anal. Calcd for
C16H21OCl: C, 72.58; H, 7.99. Found: C, 72.49; H, 8.05.
Homologation of cuprates 5 and 29 and reaction with
electrophiles
(E)-1-(4-Methoxyphenyl)-4-tert-butyl(diphenyl)silyl-
methylpenta-1,4-dien-3-one (34). Viscous oil, 82%; IR
(neat): 1660, 1600, 1113, 975, 915; H NMR: 7.65±7.29
(m, 12H), 7.27 (d, Jˆ15.7 Hz, 1H), 6.88 (d, Jˆ8.8 Hz,
1H), 6.77 (d, Jˆ15.7 Hz, 1H), 5.67 (s, 1H), 5.35 (s, 1H),
3.84 (s, 3H), 2.62 (s, 2H), 1.09 (s, 9H); 13C NMR: 192.4,
161.2, 147.3, 142.8, 136.4, 133.9, 129.8, 129.1, 127.7,
127.5, 121.9, 119.6, 114.2, 55.3, 27.8, 18.5, 14.1; MS(EI)
m/z: 440 (M1, 0.5%), 383, 199 (100).
1
A solution of (iodomethyl)zinc iodide (5 mmol) freshly
prepared24 in THF (5 ml) was added at 2408C to a solution
of intermediate 5 or 29 (3 mmol) which was prepared using
the general procedure. The reaction mixture was stirred at
this temperature for 30 min, then 3.6 mmol of benzal-
acetone, cyclopentanone or cyclohex-2-en-1-one in THF
(3 ml) were added dropwise and the resulting solution was
kept at 2408C for 2 h. After allowing the mixture to warm
up to 08C, it was quenched with saturated ammonium
chloride solution and extracted twice with Et2O. The
organic layer was dried, rotoevaporated and chromato-
graphed (EtOAc:hexanes) to give 35±39 (Scheme 6).
Reaction of 8 with carbonyl derivatives
To 0.22 ml of TiCl4 (2 mmol) in 10 ml of dry CH2Cl2 was
added at 2788C, under nitrogen, butyraldehyde or benzal-
acetone (2 mmol) and immediately a solution of 8 (432 mg,
2 mmol) in CH2Cl2 (1 ml). The resulting mixture was stirred
at 2788C for 30 min and quenched with MeOH at this
temperature. The solution was allowed to warm up to
room temperature, washed with a saturated solution of
sodium bicarbonate, extracted with CH2Cl2, dried over
MgSO4 and evaporated. Puri®cation by ¯ash-chromato-
graphy (EtOAc:hexanes) gave 24±26 (Scheme 4).
(E)-1-Phenyl-3-methyl-5-tert-butyl(diphenyl)silylmethyl-
hexa-1,5-dien-3-ol (35). Oil, 65%; IR (neat): 3550, 1632,
1599, 1230, 1112, 985, 892; 1H NMR: 7.68±7.28 (m, 15H),
6.51 (d, Jˆ16.2 Hz, 1H), 6.14 (d, Jˆ16.2 Hz, 1H), 4.87 (d,
Jˆ1.6 Hz, 1H), 4.72 (d, Jˆ1.6 Hz, 1H), 2.35 (d, Jˆ13.9 Hz,
1H), 2.28 (d, Jˆ13.9 Hz, 1H), 2.04 (br s, 1H), 1.99 (s, 2H),
1.23 (s, 3H), 1.05 (s, 9H); 13C NMR: 143.4, 137.0, 136.9,
136.3, 136.1, 135.9, 134.7, 134.5, 129.2, 128.5, 127.5,
127.4, 127.2, 126.4, 126.2, 115.2, 71.9, 50.6, 28.6, 27.7,
22.2, 18.5; MS(CI) m/z: 441 (M11, 1%), 440 (M1, 2%),
423, 345, 383, 239 (100). Anal. Calcd for C30H36SiO: C,
81.76; H, 8.23. Found: C, 81.50; H, 8.11.
6-Methylenenon-8-en-4-ol (24). Oil, 67%; IR (neat): 3390,
1638, 1122, 1020, 991, 911, 893; H NMR: 5.80 (ddt,
1
Jˆ17.5, 9.6 and 7.0 Hz, 1H), 5.11±5.03 (m, 2H), 4.92 (s
with ®ne couplings, 1H), 4.88 (s with ®ne couplings, 1H),
3.73 (m, 1H), 2.82 (dd, Jˆ17.2 and 7.0 Hz, 1H), 2.76 (dd,
Jˆ17.2 and 7.0 Hz, 1H), 2.25 (dd, Jˆ2.5 and 14.1, 1H),
2.06 (dd, Jˆ9.1 and 14.1, 1H), 1.74 (br s, 1H), 1.51±1.32
(m, 4H), 0.93 (t, Jˆ7.1 Hz, 3H); 13C NMR: 145.1, 135.9,
116.6, 113.5, 68.5, 44.3, 40.5, 39.2, 18.9, 14.1; MS(EI) m/z:
154 (M1, 10%), 155, 137, 111, 93, 82, 73, 67, 55, 43, 41 (100).
1-[2-tert-Butyl(diphenyl)silylmethylprop-2-en-1-yl]cyclo-
pentan-1-ol (36). Oil, 75%; IR (neat): 3555, 1624, 1240,
1100, 900; 1H NMR: 7.69±7.34 (m, 10H), 4.82 (d,
Jˆ0.8 Hz, 1H), 4.68 (d, Jˆ0.8 Hz, 1H), 2.35 (s, 2H), 1.91
(s, 2H), 1.80±1.35 (m, 8H), 1.63 (br s, 1H), 1.10 (s, 9H); 13C
NMR: 144.2, 136.3, 134.6, 129.1, 127.4, 113.8, 80.8, 48.5,
39.8, 27.8, 23.4, 22.0, 18.5; MS(CI) m/z: 379 (M11, 2%),
378 (M1, 1%), 361, 321, 239, 123 (100). Anal. Calcd for
C25H34SiO: C, 79.31; H, 9.05. Found: C, 79.52; H, 9.16.
2-Allyl-2-methyl-4-propyloxetane (25). Oil, 28%; IR
1
(neat): 1648, 1034, 988, 905; H NMR: 5.92 (ddt, Jˆ17.1,
10.1 and 7.0 Hz, 1H), 5.19±5.10 (m, 2H), 3.99 (m, 1H), 2.65
(dd, Jˆ17.0 and 10.1 Hz, 1H), 2.61 (dd, Jˆ17.0 and
10.1 Hz, 1H), 1.95 (dd, Jˆ8.4 and 15.1 Hz, 1H), 1.83 (dd,
Jˆ2.0 and 15.1 Hz, 1H), 1.59 (s, 3H), 1.53±1.30 (m, 4H),
0.94 (t, Jˆ7.0 Hz, 3H); 13C NMR: 133.3, 119.0, 73.3, 68.4,
50.3, 49.3, 40.6, 30.1, 18.6, 14.0; MS(EI) m/z: 154 (M1,
0.2%), 139, 82, 67 (100), 55, 41. Anal. Calcd for
C10H18O: C, 77.87; H, 11.76. Found: C, 78.25; H, 12.01.
1-[2-tert-Butyl(diphenyl)silylmethylprop-2-en-1-yl]cyclo-
hex-2-en-1-ol (37).Z Oil, 61%; IR (neat): 3650, 3400, 1635,
1243, 1180, 1105, 902; 1H NMR: 7.70±7.32 (m, 10H), 5.71
(dt, Jˆ10.2 and 3.6 Hz, 1H), 5.46 (d with ®ne couplings,
Jˆ10.2 Hz, 1H), 4.81 (d with ®ne couplings, Jˆ1.8 Hz,
1H), 4.64 (d, Jˆ1.8 Hz, 1H), 2.40 (d with ®ne couplings,
Jˆ13.8 Hz, 1H), 2.33 (d with ®ne couplings, Jˆ13.8 Hz,
1H), 1.98±1.47 (m, 6H), 1.92 (d, Jˆ13.6 Hz, 1H), 1.83 (d,
Jˆ13.6 Hz, 1H), 1.72 (br s, 1H), 1.08 (s, 9H); 13C NMR:
143.4, 136.4, 134.6, 132.8, 129.1, 127.5, 128.9, 114.7, 69.5,
49.6, 35.9, 27.8, 25.1, 22.4, 19.2, 18.6; MS(CI) m/z: 391
(M11, 9%), 390 (M1, 2%), 373, 333, 295 (100), 239.
Anal. Calcd for C26H34SiO: C, 79.94; H, 8.77. Found: C,
80.34; H, 9.08.
[1Sp,3Rp,5Rp]-1-Methyl-3-allyl-3-chloro-5-phenylcyclo-
hexan-1-ol (26). Oil, 69%; IR (neat): 3560, 3450, 1644,
1153, 995, 923; H NMR (CDCl3, 500 MHz): 7.35±7.19
1
(m, 5H), 5.95 (ddt, Jˆ17.0, 9.9 and 7.0 Hz, 1H), 5.21 (d,
Jˆ9.9 Hz, 1H), 5.16 (d, Jˆ17.0 Hz, 1H), 3.57 (br s, 1H),
3.38 (tt, Jˆ12.7 and 3.1 Hz, 1H), 2.59 (dd, Jˆ14.1 and
7.0 Hz, 1H), 2.57 (dd, Jˆ14.1 and 7.0 Hz, 1H), 2.27±2.18
(m, 2H), 2.02 (dd with other ®ne couplings, Jˆ13.2 and
3.1 Hz, 1H), 1.69 (d, Jˆ15.2 Hz, 1H), 1.63 (dd, Jˆ13.7
and 12.7 Hz, 1H), 1.52 (dd, Jˆ13.2 and 12.7 Hz, 1H),
1-[2-Dimethyl(phenyl)silylmethylprop-2-en-1-yl]cyclo-
pentan-1-ol (38). Oil, 27%; IR (neat): 3580, 3500, 1620,

A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
2749
1
1252, 1161, 1115, 885, 832; H NMR: 7.54±7.34 (m, 5H),
(E)-2-tert-Butyl(diphenyl)silylmethylene-4-phenylcyclo-
pentan-1-one (45). Oil, 67%; IR (neat): 1708, 1612, 1100,
750, 700; H NMR: 7.78±7.30 (m, 10H), 7.23±6.70 (m,
4.71 (s, 2H), 2.14 (s, 2H), 1.89 (s, 2H), 1.84±1.47 (m, 8H),
1.76 (br s, 1H), 0.33 (s, 6H); 13C NMR: 144.3, 138.8, 133.6,
129.0, 127.7, 111.9, 80.8, 48.6, 39.9, 27.7, 23.4, 23.1;
MS(EI) m/z: 274 (M1, 0.2%), 259, 219, 135 (100).
1
5H), 6.61 (s with ®ne couplings, 1H), 3.75 (m, 1H), 2.75
(dd, Jˆ18.8 and 6.9 Hz, 1H), 2.46 (dt, Jˆ14.8 and 1.2 Hz,
1H), 2.29 (dt, Jˆ14.8 and 1.4 Hz, 1H), 2.10 (dd, Jˆ18.8 and
2.4 Hz, 1H), 1.11 (s, 9H); 13C NMR: 209.3, 158.8, 142.6,
136.2, 134.8, 133.7, 129.6, 128.6, 127.7, 126.9, 126.6, 43.9,
43.7, 27.7, 18.5, 6.4; MS(CI) m/z: 411 (M11, 0.8%), 353
(100), 199. Anal. Calcd for C28H30SiO: C, 81.90; H, 7.36.
Found: C, 81.61; H, 7.57.
1-[2-Dimethyl(phenyl)silylmethylprop-2-en-1-yl]cyclo-
hex-2-en-1-ol (39). Oil, 20%; IR (neat): 3450, 1630, 1246,
1
1145, 1105, 871, 830; H NMR: 7.57±7.32 (m, 5H), 5.75
(dt, Jˆ10.1 and 3.4 Hz, 1H), 5.56 (d with ®ne couplings,
Jˆ10.1 Hz, 1H), 4.72 (m, 2H), 2.42±1.40 (m, 6H), 2.13 (s
with ®ne couplings, 2H), 1.92 (s with ®ne couplings, 2H),
1.63 (br s, 1H), 0.32 (s, 6H); 13C NMR: 143.5, 138.8, 134.3,
133.6, 129.0, 128.2, 127.7, 112.5, 77.2, 49.8, 35.9, 28.0,
25.1, 19.2, 22.9; MS(EI) m/z: 286 (M1, 0.3%), 268, 209,
190, 135 (100).
(E)-2-tert-Butyl(diphenyl)silylmethylene-4-(4-methoxy-
phenyl)cyclopentan-1-one (46). Oil, 63%; IR (neat): 1700,
1605, 1240, 1105, 835, 740, 690; H NMR: 7.70±7.33 (m,
1
10H), 6.72 (d, Jˆ8.8 Hz, 2H), 6.60 (d, Jˆ8.8 Hz, 2H), 6.59
(s, 1H), 3.77 (s, 3H), 3.72 (m, 1H), 2.73 (dd, Jˆ18.8 and
6.8 Hz, 1H), 2.46 (dt, Jˆ14.7 and 1.3 Hz, 1H), 2.27 (dt,
Jˆ14.7 and 1.6 Hz, 1H), 2.06 (dd, Jˆ18.8 and 2.6 Hz,
1H), 1.10 (s, 9H); 13C NMR: 209.4, 159.0, 158.2, 142.4,
136.1, 134.5, 133.7, 129.3, 127.9, 127.6, 113.9, 55.2, 43.9,
43.1, 27.6, 18.5, 6.3; MS(CI) m/z: 441 (M11, 1.5%), 425,
383 (100), 199.
Directed Nazarov reactions
A solution of 12±14, 33 or 34 (2 mmol) in THF (3 ml) was
cooled at 08C and TFA (0.46 ml, 6 mmol) was added with
continuous stirring. After 30 min at 08C, the solution was
warmed up to room temperature and stirred for an additional
period of 2 h. In the case of compounds 33 and 34 bearing
the t-butyldiphenylsilyl group the reaction temperature was
increased to 40±508C and the mixture stirred for 1 h. The
reaction was stopped by adding a saturated solution of
sodium bicarbonate (5 ml). After extraction with Et2O, the
ethereal layer was washed twice with brine, dried and
concentrated. The crude was puri®ed by ¯ash-chromato-
graphy (EtOAc:hexanes) to give 42±46 (Scheme 7).
Reaction of 42 and 44 with intermediate 5
Following Procedure 2 ketones 42 and 44 (2 mmol) were
allowed to react with cuprate 5 (2.2 mmol) in the presence
of BF3 (2 mmol) to give 47 and 48 respectively (Scheme 9).
trans-2-[2-Dimethyl(phenyl)silylmethylprop-2-en-1-yl]-
4-phenylcyclopentan-1-one (47). Oil, 84%; IR (neat):
1747, 1636, 1250, 1110, 885, 832; H NMR: 7.57±7.22
1
2-Methylene-4-phenylcyclopentan-1-one (42). Oil, 83%;
IR (neat): 1722, 1638, 936, 750, 697; H NMR: 7.39±7.22
1
(m, 10H), 4.67 (s, 1H), 4.60 (s, 1H), 3.29 (tt, Jˆ12.1 and
8.2 Hz, 1H), 2.78 (dd with ®ne couplings, Jˆ18.5 and
8.2 Hz, 1H), 2.60±2.38 (m, 3H), 2.30 (dd, Jˆ18.5 and
12.1 Hz, 1H), 1.86 (dd, Jˆ15.4 and 10.3 Hz, 1H), 1.84 (d,
Jˆ13.9 Hz, 1H), 1.74 (d, Jˆ13.9 Hz, 1H), 1.53 (q,
Jˆ12.0 Hz, 1H), 0.36 (s, 6H); 13C NMR: 218.6, 144.4,
142.9, 138.7, 133.6, 129.0, 128.6, 127.8, 126.7, 126.6,
109.3, 49.3, 45.6, 39.9, 38.5, 38.1, 25.6, 22.9, 23.0;
MS(EI) m/z: 348 (M1, 2%), 333, 292, 270, 255, 135
(100). Anal. Calcd for C23H28SiO: C, 79.26; H, 8.10.
Found: C, 79.45; H, 8.30.
(m, 5H), 6.07 (s with ®ne couplings, 1H), 5.38 (s with ®ne
couplings, 1H), 3.42 (tt, Jˆ10.1 and 7.5 Hz, 1H), 3.14 (dd
with ®ne couplings, Jˆ16.4 and 7.5 Hz, 1H), 2.87±2.70 (m,
2H), 2.53 (dd, Jˆ10.1 and 17.7 Hz, 1H); 13C NMR: 205.6,
144.5, 143.2, 128.7, 126.8, 126.6, 117.5, 45.9, 38.9, 38.0;
MS(EI) m/z: 172 (M1, 58%), 143, 128, 115, 103, 91, 68
(100). Anal. Calcd for C12H12O: C, 83.69; H, 7.02. Found:
C, 83.80; H, 7.11.
2-Methylene-4-(4-methoxyphenyl)cyclopentan-1-one (43).
Oil, 78%; IR (neat): 1726, 1640, 1250, 942, 834; 1H NMR:
7.22 (d, Jˆ8.7 Hz, 2H), 6.88 (d, Jˆ8.7 Hz, 2H), 6.06 (s with
®ne couplings, 1H), 5.37 (s with ®ne couplings, 1H), 3.81 (s,
3H), 3.37 (tt, Jˆ10.2 and 7.2 Hz, 1H), 3.11 (dd with ®ne
couplings, Jˆ16.3 and 7.2 Hz, 1H), 2.77±2.65 (m, 2H), 2.48
(dd, Jˆ10.2 and 17.9 Hz, 1H); 13C NMR: 205.7, 158.3,
144.7, 135.2, 127.6, 117.4, 114.0, 55.2, 46.1, 38.2, 38.0;
MS(EI) m/z: 202 (M1, 100%), 187, 171, 159, 134, 119,
91, 68.
[1Sp,3Rp,5Sp]-3-[2-Dimethyl(phenyl)silylmethylprop-2-
en-1-yl]bicyclo[3.3.0]octan-2-one (48). Oil, 82%; IR
(neat): 1738, 1630, 1255, 1115, 874, 835; H NMR: 7.55±
1
7.34 (m, 5H), 4.62 (s with ®ne couplings, 1H), 4.56 (s with
®ne couplings, 1H), 2.71 (m, 1H), 2.70±2.30 (m, 4H), 1.96±
1.31 (m, 8H), 1.78 (d, Jˆ13.7 Hz, 1H), 1.70 (d, Jˆ13.7 Hz,
1H), 0.34 (s, 6H); 13C NMR: 221.5, 144.9, 138.8, 133.5,
129.0, 127.7, 108.7, 51.4, 48.7, 38.0, 37.7, 34.5, 33.6,
29.0, 25.7, 24.9, 23.0; MS(EI) m/z: 312 (M1, 11%), 297,
269, 257, 235, 135 (100). Anal. Calcd for C20H28SiO: C,
76.86; H, 9.03. Found: C, 77.10; H, 8.95.
cis-3-Methylenebicyclo[3.3.0]octan-2-one (44). Oil, 75%;
IR (neat): 1720, 1635, 932; 1H NMR: 5.96 (m, 1H), 5.29 (m,
1H), 2.85 (ddt, Jˆ17.3, 8.1 and 2.9 Hz, 1H), 2.75±2.60 (m,
2H), 2.42 (dq, Jˆ17.3 and 2.1 Hz, 1H), 2.03±1.77 (m, 3H),
1.56 (quintet, Jˆ7.0 Hz, 2H), 1.21 (sextet, Jˆ7.1 Hz, 1H);
13C NMR: 210.9, 144.8, 118.0, 53.1, 37.9, 33.8, 33.5, 29.8,
26.1; MS(EI) m/z: 136 (M1, 48%), 121, 108, 93, 79, 67
(100). Anal. Calcd for C9H12O: C, 79.37; H, 8.88. Found:
C, 79.60; H, 9.01.
Allylsilane terminated cyclizations
TiCl4 catalyzed reactions. TiCl4 (0.13 ml, 1.2 mmol) was
added slowly to a solution of 16, 17 or 21 (2 mmol) in
CH2Cl2 (8 ml) at 2788C, under nitrogen. After stirring for
30 min at this temperature, 2 ml of MeOH were added at

2750
A. Barbero et al. / Tetrahedron 56 (2000) 2739±2751
once and the mixture was allowed to warm up to 08C. The
reaction mixture was washed with a saturated solution of
sodium bicarbonate, extracted with Et2O, dried over MgSO4
and rotoevaporated. Puri®cation by ¯ash-chromatography
(EtOAc:hexanes) gave 49, 50 and 53 (Scheme 10).
[1Rp,5Rp,7Sp]-3-Methylene-7-phenylbicyclo[3.3.0]octan-
1-ol (54). White crystals mpˆ67±688C (hexane), 70%; IR
1
(Cl4C): 3610, 3350, 1664, 1070, 890; H NMR: 7.34±7.18
(m, 5H), 4.87 (s with ®ne couplings, 1H), 4.85 (s with ®ne
couplings, 1H), 3.22 (tt, Jˆ12.4 and 6.2 Hz, 1H), 2.77 (dd
with ®ne couplings, Jˆ15.0 and 9.4 Hz, 1H), 2.57 (d with
®ne couplings, Jˆ15.4 Hz, 1H), 2.49 (d with ®ne couplings,
Jˆ15.4 Hz, 1H), 2.52±2.38 (m, 2H), 2.22 (dd with ®ne
couplings, Jˆ12.4 and 6.2 Hz, 1H), 2.03 (d with ®ne
couplings, Jˆ15.0 Hz, 1H), 1.78 (t, Jˆ12.4 Hz, 1H), 1.61
(br s, 1H), 1.36 (dd with other couplings, Jˆ12.4 and
3.5 Hz, 1H); 13C NMR: 150.2, 143.8, 128.3, 126.9, 126.1,
107.6, 88.8, 51.7, 48.6, 48.4, 44.2, 42.3, 39.2; MS(EI) m/z:
214 (M1, 50%), 199, 171, 156, 143, 129, 104 (100), 91.
Anal. Calcd for C15H18O: C, 84.07; H, 8.47. Found: C,
84.27; H, 8.60.
cis-3-Methylene-4-phenylcyclopentan-1-ol (49). Oil,
87%; IR (neat): 3350, 1648, 1075, 882, 750, 690; 1H
NMR: 7.36±7.20 (m, 5H), 5.03 (d with ®ne couplings,
Jˆ2.3 Hz, 1H), 4.56 (d with ®ne couplings, Jˆ2.3 Hz,
1H), 4.42 (quintet, Jˆ7.1 Hz, 1H), 3.64, (t with ®ne
couplings, Jˆ10.3 Hz, 1H), 2.87 (dd with ®ne couplings,
Jˆ16.2 and 7.1 Hz, 1H), 2.56±2.45 (m, 2H), 1.94 (br s,
1H), 1.89 (ddd, Jˆ12.6, 10.3 and 7.1 Hz, 1H); 13C NMR:
153, 143, 128.4, 128.3, 126.2, 109.1, 71.5, 48.7, 44.5, 43.0;
MS(CI) m/z: 175 (M11, 28%), 157 (100), 131, 97. Anal.
Calcd for C12H14O: C, 82.72; H, 8.10. Found: C, 82.90; H,
8.13.
10-Methylene-cis,anti,cis-tricyclo[6.3.0.02,6]undecan-1-ol
(55). Oil, 68%; IR (neat): 3595, 3450, 1655, 1065, 878; H
1
[1Rp,6Sp,7Rp]- and [1Rp,6Sp,7Sp]-7-Methyl-9-methylene-
bicyclo[4.3.0]nonan-7-ol (53). Oil, 79%; IR (neat): 3430,
1657, 1110, 880; 1H NMR: 4.92 (q, Jˆ2.2 Hz, 1H), 4.84 (q,
Jˆ2.2 Hz, 1H), 2.67 (m, 1H), 2.54 (d with ®ne couplings,
Jˆ17.6 Hz, 1H), 2.49 (d with ®ne couplings, Jˆ17.6 Hz,
1H), 1.88 (dq, Jˆ14.0 and 3.4 Hz, 1H), 1.80±1.50 (m,
4H), 1.72 (br s, 1H), 1.50±1.10 (m, 4H), 1.34 (s, 3H). The
epimeric alcohol shows a methyl signal at 1.35 (ratio 3:1);
13C NMR: 150.5, 105.6, 78.1, 48.7, 46.0, 42.0, 28.5, 25.9,
24.5, 23.3, 21.3; MS(EI) m/z: 166 (M1, 34%), 151, 148, 133,
123 (100). Anal. Calcd for C11H18O: C, 79.46; H, 10.91.
Found: C, 79.88; H, 11.22.
NMR: 4.91 (s with ®ne couplings, 2H), 2.65 (dd with ®ne
couplings, Jˆ16.7 and 7.2 Hz, 1H), 2.55±2.15 (m, 6H), 1.84
(ddd, Jˆ12.5, 8.1 and 6.4 Hz, 1H), 1.70±1.40 (m, 7H), 1.29
(sextet, Jˆ6.4 Hz, 1H); 13C NMR: 150.8, 107.5, 90.5, 51.4,
49.2, 47.4, 41.9, 37.2, 36.6, 35.2, 28.5, 27.3; MS(EI) m/z: 178
(M1, 10%), 163, 135, 123, 95, 82, 67, 41 (100). Anal. Calcd
for C12H18O: C, 80.85; H, 10.18. Found: C, 81.21; H, 10.46.
3-tert-Butyl(diphenyl)silylmethyl-4-phenylcyclopent-3-
en-1-ol (56). Oil, 69%; IR (neat): 3400, 1621, 1600, 1590,
1250, 1105, 1037, 700; 1H NMR: 7.61±7.17 (m, 15H), 4.12
(t with ®ne couplings, Jˆ5.9 Hz, 1H), 2.87 (dd with ®ne
couplings, Jˆ16.2 and 5.9 Hz, 1H), 2.53±2.39 (m, 4H),
2.02 (d, Jˆ17.4 Hz, 1H), 1.31 (br s, 1H), 0.98 (s, 9H); 13C
NMR: 138.3, 136.1, 134.4, 133.5, 131.4, 129.2, 128.1,
127.6, 127.4, 126.2, 70.0, 49.1, 46.9, 27.4, 18.3, 13.0;
MS(EI) m/z: 412 (M1, 0.2%), 355, 199 (100), 156, 135.
Anal. Calcd for C28H32SiO: C, 81.50; H, 7.82. Found: C,
81.64; H, 7.94.
Allylsilane terminated cyclizations. EtAlCl2 catalyzed
reactions
EtAlCl2 (2.4 mmol, 1.8 M in toluene) was added slowly to a
solution of 19, 20, 47, 48, 30 or 31 (2 mmol) in toluene
(8 ml) at 08C, under nitrogen. After stirring for 1 h at 08C,
brine was added (5 ml) and the mixture extracted with Et2O,
dried and evaporated. Puri®cation by ¯ash-chromatography
gave 51, 52 and 54±57 (Scheme 10).
3-tert-Butyl(diphenyl)silylmethyl-1-methyl-4-phenylcyclo-
pent-3-en-1-ol (57). Oil, 77%; IR (neat): 3570, 3450, 1628,
1600, 1590, 1235, 1110, 1080, 705; 1H NMR: 7.66±7.22 (m,
15H), 2.73 (d, Jˆ16.2 Hz, 1H), 2.58 (d, Jˆ16.2 Hz, 1H),
2.56 (d, Jˆ14.1 Hz, 1H), 2.41 (d, Jˆ14.1 Hz, 1H), 2.32 (d,
Jˆ17.1 Hz, 1H), 2.19 (d, Jˆ17.1 Hz, 1H), 1.40 (br s, 1H),
1.21 (s, 3H), 1.02 (s, 9H); 13C NMR: 138.3, 136.1, 134.3,
134.1, 132.2, 129.3, 128.1, 127.7, 127.5, 126.2, 76.5, 54.5,
52.6, 27.4, 27.2, 18.4, 12.8; MS(EI) m/z: 426 (M1, 10%),
369, 199 (100), 135. Anal. Calcd for C29H34SiO: C, 81.64;
H, 8.03. Found: C, 81.92; H, 7.83.
3-Methylene-4-methylbicyclo[2.2.1]heptan-1-ol
(51).
White crystals mpˆ50±518C (hexane), 81%; IR (Cl4C):
1
3615, 3355, 1660, 1305, 1107, 884; H NMR: 4.71 (t,
Jˆ1.9 Hz, 1H), 4.62 (t, Jˆ1.9 Hz, 1H), 2.46 (dt, Jˆ15.4
and 1.9 Hz, 1H), 2.38 (dt, Jˆ15.4 and 1.9 Hz, 1H), 1.95±
1.35 (m, 7H), 1.19 (s, 3H); 13C NMR: 156.2, 101.0, 80.1,
51.0, 47.3, 44.9, 36.7, 36.1, 17.9; MS(EI) m/z: 138 (M1,
27%), 123 (100), 110, 109, 95. Anal. Calcd for C9H14O:
C, 78.21; H, 10.21. Found: C, 78.39; H, 10.30.
Acknowledgements
6-Methylenebicyclo[3.2.1]octan-1-ol (52). White crystals
mpˆ53±548C (hexane), 92%; IR (Cl4C): 3595, 3355,
We gratefully acknowledge ®nancial support from the
Ministry of Education and Culture of Spain (DGES PB96/
Â
0357 project) and from the `Junta de Castilla y Leon'
(VA43/98 project).
1
1653, 1120, 877; H NMR: 4.76 (s with ®ne couplings,
2H), 2.68 (m, 1H), 2.61 (br s, 1H), 2.38 (d with ®ne
couplings, Jˆ16.7 Hz, 1H), 2.29 (d with ®ne couplings,
Jˆ16.7 Hz, 1H), 1.87 (m, 1H), 1.75±1.36 (m, 7H);); 13C
NMR: 152.9, 105.1, 77.7, 46.1, 44.0, 43.7, 39.4, 32.8,
20.0; MS(EI) m/z: 138 (M1, 5%), 123, 110, 109, 95 (100).
Anal. Calcd for C9H14O: C, 78.21; H, 10.21. Found: C,
78.17; H, 10.22.
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