Vinyldisiloxanes: Their synthesis, cross coupling and applications

Article abstract of DOI:10.1039/c0ob00338g

During the studies towards the development of pentafluorophenyldimethylsilanes as a novel organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our previous report focused on the synthesis and base induced cross coupling of aryl substituted vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our research, studies into the factors which influence the successful outcome of the cross coupling reaction with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism discussed. Further investigation into expanding the breadth and diversity of substituted vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical trans-stilbenes and cyclic structures containing the trans-alkene architecture.

Full text of DOI:10.1039/c0ob00338g

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PAPER
Vinyldisiloxanes: their synthesis, cross coupling and applications†
Hannah F. Sore, Christine M. Boehner, Luca Laraia, Patrizia Logoteta, Cora Prestinari, Matthew Scott,
Katharine Williams, Warren R. J. D. Galloway and David R. Spring*
Received 28th June 2010, Accepted 7th September 2010
DOI: 10.1039/c0ob00338g
During the studies towards the development of pentafluorophenyldimethylsilanes as a novel
organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding
disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with
the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our
previous report focused on the synthesis and base induced cross coupling of aryl substituted
vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our
research, studies into the factors which influence the successful outcome of the cross coupling reaction
with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism
discussed. Further investigation into expanding the breadth and diversity of substituted
vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical
trans-stilbenes and cyclic structures containing the trans-alkene architecture.
developed: examples include silacyclobutanes,10,11 triallyl-
Introduction
silanes,12
phenyldimethylsilanes,13
benzyldimethylsilanes,14
[2-(hydroxymethyl)-
2-pyridylsilanes,15
2-thienylsilanes,16,17
The synthesis of carbon–carbon bonds by transition metal catal-
ysed cross coupling has developed over the past 40 years into
arguablyoneofthemostutilisedandimportantclassesofreactions
within organic chemistry.1 Numerous organometallic species have
been developed as suitable cross coupling partners, two of the most
significant being organotin (Stille)2 and organoboron reagents
(Suzuki).3 To expand on the scope, breadth and application
of cross coupling reactions even further, ongoing research into
alternative coupling species and conditions are being developed
that offer the possibility of milder reaction conditions, greater
functional group tolerance, reduced toxicity, ease of reagent
synthesis, trouble-free isolation and increased reagent stability.
Consequently, the pioneering discovery by Hiyama and Hatanaka
that organosilicon reagents could effectively participate in palla-
dium catalysed cross coupling aroused interest.4 The addition of
fluoride ions was required to activate the Si–C bond by formation
of a pentacoordinate silyl species which facilitates transmetallation
with palladium(II).5,6 Since these pioneering reports, significant
advances in the cross coupling of organosilicon reagents have
been made, the most prominent being the coupling of silanols
under fluoride free (base induced) conditions.7,8
phenyl]dimethylsilanes18 and disiloxanes.9,19–22 When subjected to
the appropriate reactions conditions these ‘masked’ silanols are
deprotected in situ to reveal the active silanol in preparation for
the subsequent coupling reaction. Drawbacks of existing ‘masked’
silanols include loss of double bond configuration upon coupling,
protodesilylation, the wrong group transferring (benzyl migration
with benzyldimethylsilanes specifically) and high sensitivity to
reaction conditions and variations in the coupling partners.11,13,23
Disiloxanes offer the advantage of increased stability relative
to the silanol and the potential to be carried through multi-step
synthesis; moreover, they are highly atom efficient compared to al-
ternative ‘masked’ silanols.9,19,20 In addition, aryl substituted vinyl-
disiloxanes are readily prepared from inexpensive starting materi-
als, show good levels of functional group tolerance and can react
under mild basic conditions with retention of stereochemistry.19
As a continuation from our previous research, herein, we aim to
highlight and expand on our initial discoveries to include alkyl
substituted vinyldisiloxanes and exemplify possible applications
of this novel vinyldisiloxane methodology. On examination of
the experimental data, a mechanism was proposed and influential
factors identified to account for the observed isomerisation of the
double bond geometry in particular coupling reactions.
The high reactivity and suitability of organosilanols for
cross coupling; consequently, can hinder their progression
as a functional group through multistep syntheses.9,10 As
a result, more stable ‘masked’ forms of silanols have been
Results and Discussion
Department of Chemistry, University of Cambridge, Lensfield Road, Cam-
bridge, UK CB2 1EW. E-mail: spring@cam.ac.uk
The transition to disiloxanes
† Electronic supplementary information (ESI) available: 1H-NMR and
13C-NMR spectra for all compounds. See DOI: 10.1039/c0ob00338g
In our quest to develop pentafluorophenyldimethylvinylsilanes
(1, Scheme 1) into new class of ‘masked’ silanols, the necessary
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induced conditions, two similar experiments were conducted.
One experiment started from the disiloxane (6), the other from
the respective silanol (8). Treatment of the two silicon reagents
with KOH in CD3OD resulted in identical 1H-NMR spectra,
indicating an equilibrium had been established in both incidences,
ultimately resulting in the indistinguishable spectra. Building
on these prior NMR experiments, we were optimistic that the
disiloxane (6) would participate in fluoride free cross coupling
with 4-iodoacetophenone. The ratio of disiloxane to aryl halide
used was 1 : 1.5, making the aryl halide the limiting reagent,
assuming that the disiloxane acts as two equivalents. Monitoring
the coupling reaction over time saw complete consumption of the
aryl halide and formation of the (E)-disubstituted alkene (9).
Scheme 1 Potential intermediates in the fluoride free coupling.
regio- and stereoselective synthesis of (E)-, (Z)- and a-vinylsilanes
was successfully achieved; however, the development of fluoride
free cross coupling conditions proved challenging.24 Excellent
yields and selectivities were obtained under fluoride induced cross
coupling procedures;24 but, on applying base activated coupling
conditions, the selectivity and yields acquired were inconsistent
and sometimes disappointing. Consquently, a detailed examina-
tion into the reaction profile was undertaken.
On considering the potential intermediates in the reaction
pathway (Scheme 1), three fundamental questions arose: 1) how
facile is the deprotection of the pentafluorophenyl group with base
to reveal the active silanolate (transformation 1 to 2); 2) under the
reaction conditions is the silanolate (2) in an equilibrium with
the more stable disiloxane (3), or is the corresponding disiloxane
acting as a silicon sink removing the silyl reagent from the active
reaction mixture; and 3) are disiloxanes able to directly participate
in fluoride free cross coupling with aryl halides (conversion of 3
to produce 4)?
Development of substituted vinyldisiloxanes
1
After the interesting results from the H-NMR studies, the aim
was to develop and optimise the synthesis and cross coupling of
substituted vinyldisiloxanes, with the intention of creating: 1) an
attractive atom efficient alternative to existing ‘masked’ silanols
that was able to partake in cross coupling under base induced
conditions; 2) a protocol that utilised cheap reagents and was
operationally simple; 3) a process that created and then maintained
excellent geometrical purity of the disubstituted double bond; and
4) the products in good yields and under mild conditions.
To evaluate the scope of the cross coupling reaction, it was
first necessary to prepare a variety of substituted vinyldisiloxanes.
Exceptional (E)-selectivity can be achieved for the hydrosilylation
of terminal alkynes with Pt-catalysts.25 In agreement with a report
by Denmark22 it was found that the hydrosilylation of terminal
alkynes with 1,1,3,3-tetramethyl-disiloxane (11) produced the
corresponding (E)- vinyldisiloxanes (3) in excellent yields and
selectivity when the catalytic complex (tBu3P)Pt(DVDS) was
employed (Table 1). Pleasingly, the high yields and selectivity were
maintained when a wide variety of terminal alkynes were surveyed.
Alkyl substituted terminal alkynes containing functionalities such
as a free alcohol, a silyl protected alcohol and a bulky tert-butyl
group and aryl substituted terminal alkynes containing electron
rich, electron poor and heterocyclic rings were all well tolerated;
the products were formed in good yields, with only the (E)-
disiloxanes observed by crude 1H-NMR spectroscopy.
A series of 1H-NMR experiments were conducted in an attempt
to answer these key questions (Scheme 2). On treating pentafluo-
rophenyldimethylvinylsilane 5 with KOH in deuterated methanol,
no starting material was observed after immediate inspection by
1H-NMR spectroscopy. The pentafluorophenyl group had been
displaced within seconds under the basic reaction conditions,
producing a mixture of the corresponding disiloxane (6) and
presumably the silanolate (7). To determine if the disiloxane
(6) and active silanolate (7) are in equilibrium under base
The scope of the fluoride free cross coupling was explored by
coupling a variety of differentially substituted (E)-vinyldisiloxanes
(3) with a selection of aryl iodides (Table 2). Firstly, the impact
of the aryl iodide on the yield and regioselectivity (i.e. (E)-, (Z)-
or (a)- product alkene geometry) of the reaction was investigated.
In no case was there evidence for the formation of any of the
undesired (Z)-product isomer. Electron deficient aryl iodides,
including those with bulky ortho-substituents and heteroaryls,
coupled in good yields and with excellent regioselectivity, only the
desired (E)-isomer was observed by crude 1H-NMR spectroscopy
(entries 1 to 4).19 Interestingly, the cross coupling of electron rich
aryl iodides proved to be more challenging, with poor yields and
regioselectivities for the desired (E)-isomer being obtained on
employment of the standard reaction conditions (entries 5 & 6).
Mixtures of the a- and (E)-stilbenes were observed by crude 1H-
NMR; consequently, the isolated yields of the desired (E)-isomers
were only modest. Simply elevating the reaction temperature did
not assist in improving the regioselectivity for the (E)-isomer.
Scheme 2 1H-NMR experiments.
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Table 1 Synthesis of substituted (E)-vinyldisiloxanesa
Table 2 Fluoride free cross coupling of substituted (E)-vinyldisiloxanes
(3) with a selection of aryl iodidesa
Entry
1
Product
(E) (%)b
≥99
Yield (%)c
96
3a
3b
Desired (E)- isomer of
product
Crude isomeric Yield
ratio (E) : a
b
Entry ArI
1
(%)c
2
3
≥99
≥99
90
91
100 : 0
91
3c
2
3
100 : 0
100 : 0
91
75
4d
5
3d
3e
≥99
≥99
94
89
4d
5
100 : 0
62 : 38
57 : 43
56
37
33
6
7
3f
≥99
≥99
89
84
3g
8
3h
≥99
94
6
a Reaction conditions: alkyne (10) (1 equiv), silane (11) (2 equiv),
(tBu3P)Pt(DVDS) (0.2 mol%), toluene, rt. b Determined by 1H-NMR
spectroscopy. c Isolated yield after flash silica chromatography. d Heated
at 60 ◦C.
7
8
9
100 : 0
100 : 0
100 : 0
70
83
61
Although complete consumption of the aryl iodide was seen with
raised temperatures, this also resulted in an increased percentage of
the reduced aryl iodide and homo-coupled impurities. The homo-
coupled product results from an Ullmann coupling of the starting
aryl iodide.
Investigation into the effect the vinyldisiloxane substituent
has on the successful outcome of the reaction was then ex-
plored. Our previous research found that the electronic nature
of the aryl vinyldisiloxane did not appear to significantly affect
either the reactivity or regioselectivity of the cross coupling
reaction; consequently, the corresponding (E)-stilbenes were all
isolated in good yields and with excellent levels of regioselectivity
(Table 2, entries 7 to 9).19 Unfortunately, on examining the base
induced cross coupling of straight chain alkyl substituted (E)-
vinyldisiloxanes, only moderate levels of regioslectivity for the
desired product isomers (E)-4j and (E)-4k was observed (entries
10 & 11). Isomerisation of the alkene geometry of the disiloxane
starting materials had occured, leading to a mixture of the ipso and
10
58 : 42
79 : 21
100 : 0
100 : 0
19
8
11e
12e
13
24
39
1
cine substituted products by crude H-NMR spectroscopy. The
desired ipso products were isolated by flash silica chromatography,
although typically only low yields were obtained because of the
difficult separation of the isomers.
Interestingly, the sterically bulky alkyl substituted disiloxanes
displayed excellent regioselectivity, only producing the ipso sub-
stituted product on coupling with 4-iodoacetophenone, albeit
in modest yields (entries 12 & 13). In these incidences where
a Reaction conditions: aryl halide (12) (1.5 equiv), disiloxane (3), KOH
(3 equiv), Pd(dba)2 (2.5 mol%), MeOH, rt. b Determined by analysis of
1H-NMR spectrum of crude product material. c Isolated yield of pure (E)-
isomer after flash silica chromatography. d Heated at 70 ◦C. e Heated at
50 ◦C.
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transmetallation is potentially slower, the aryl halide is consumed
by reduction or homo-coupling in preference to reacting with
the active silanolate, resulting in reduced yields of the coupled
products.
Initially the mechanism is similar to the base induced catalytic
cycle, with oxidative addition of the aryl halide (R–X) to the pal-
ladium(0) species, followed by formation of the covalent Pd–O–Si
bond on reaction with the active silanolate group, generated in situ
from the disiloxane under the basic reaction conditions (Scheme 3,
intermediate 13). Further coordination of the double bond within
the tetracoordinate intermediate, facilitates Pd insertion, forming
the C–Pd bond and subsequently generating a b-cationic silicon
species (Scheme 3, intermediate 14). Progression through pathway
a results in formation of the expected ipso substituted product.
In order to promote this pathway and hence elimination, it
is necessary that the C–Si s bond is sufficiently electron rich;
consequently, stabilisation of the intermediate carbocation is
advantageous. The presence of an aryl group at R1 stabilises
the adjacent cation and in addition the use of an electron rich
silyl reagent enhances the silicon b-effect: the combination of
these two factors assists in promoting pathway a when electron
deficient aryl halides are employed. However, when electron rich
aryl halides are used, the enhanced nucleophilicity of the aryl
group now facilitated a 1,3-migration of the R group from Pd to the
b-carbon via pathway b, eventually leading to the cine substituted
products after a series of carbopalladation, dehydropalladation,
hydropalladation and reductive elimination steps.
It can also be postulated therefore, that the absence of a
carbocation stabilising group at R1 leads to the observed moderate
levels of regioselectivity for the trans substituted products on cross
coupling straight chain alkyl substituted trans vinyldisiloxanes,
even when electron deficient aryl iodides are employed as the
electrophilic partner. High levels of regioselectivity for the trans
substituted product were maintained when bulky alkyl substituted
vinyldisiloxanes were cross coupled, which may be due to the
steric hindrance of the alkyl group leading to formation of the
more thermodynamically stable (E)-isomer. Alternatively, these
high levels of trans selectivity may be rationalised on the basis
of kinetic considerations; a bulky group would be expected to
undergo slower transfer to carbon (Scheme 3, pathway b) meaning
that reaction via pathway a is favoured.
Isomerisation – the influential factors
On examining these results two factors appear to be critical for
achieving high yields and levels of regioselectivity for the desired
trans-isomer when cross coupling substituted (E)-vinyldisiloxanes.
Firstly, the electronic nature of the aryl halide has a significant
effect, with electron withdrawing substitutents producing the
desired trans-isomer (ipso substituted product) whereas electron
donating groups lead to the unexpected a-isomer (cine substituted
product). Secondly, the vinyl substituent (R1) is also highly
influential, with good yields and maintained trans double bond ge-
ometry only being achieved with aryl substituted vinyldisiloxanes.
The reaction of alkyl substituted vinyldisiloxanes only produced
the desired trans coupled products in disappointing yields and
regioselectivity; however, good regioselectivity was obtained with
bulky alkyl groups.
A similar isomerisation phenomenon has been described
by Hiyama for the palladium catalysed cross coupling
of a-alkenylfluorodimethylsilanes under fluoride activation.26,27
Hiyama noted that the relative proportions of ipso vs. cine
substituted products were closely related to the electronic nature
of the aryl iodides used, with electron rich aryl iodides yielding the
highest percentage of the cine substituted product.26 A mechanism
to account for the observed isomerisation with trans substituted
vinyldisiloxanes is proposed which amalgamates the mechanism
suggested by Hiyama to explain the isomerisation phenomenon
under fluoride activation,26 the base induced cross coupling
mechanism8,28 and the experimental observations reported here
(Scheme 3). The base induced cross coupling process is believed to
proceed via a tetracoordinate palladium intermediate rather than
the pentacoordinate species described for the fluoride activated
reaction.5,8,28
Combating isomerisation
In an endeavour to improve the regioselectivity for the (E)-
isomer (ipso substitution product) over the a-product, when
cross coupling electron rich aryl halides with aryl substiuted
vinyldisiloxanes, a variety of ligands were investigated. It was
anticipated that increasing the steric bulk around the palladium
would block the ability of the aryl group to attack the b-cation,
thus preventing progression through pathway b (Scheme 3). An
increased bite angle around the palladium (i.e., the angle of
P–Pd–P), would decrease the vinyl–Pd–Ar angle, thus assisting
in rapid reductive elimination and the potential for reduced
isomerisation of the double bond geometry on coupling. A total
of ten ligands were explored, including monodentate, bidentate
and biaryl phosphine ligands, in the coupling of 4-iodoanisole
with phenyl substituted vinyldisiloxane. A clean reaction profile
and excellent regioselectivity for the (E)-isomer was observed with
tri(o-t◦olyl)phosphine as the ligand when the reaction was heated
at 80 C. The impact of the ligand on the regioselectivity for the
(E)-isomer was highly pronounced as on applying the optimised
reaction conditions, both 4-iodoanisole and 4-iodotoluene were
Scheme 3 Proposed mechanism for the base induced cross coupling of
substituted vinyldisiloxanes with aryl halides which aims to account for
the observed trends in isomerisation.
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coupled in good yields with excellent levels of selectivity for the
ipso substituted products (Scheme 4).
and yields for the ipso substituted product being observed under
fluoride activation rather than base induced conditions. It can
be postulated therefore, that the fluoride induced coupling of
substituted vinyldisiloxanes proceeds via an alternative pathway
to the mechanism proposed in Scheme 3.
Synthesis of unsymmetrical trans-stilbenes
Unsymmetrical trans-stilbenes display a range of biological ac-
tivities. For example, Resveratrol, a hydroxylated trans-stilbene
and more recently one of its analogues DMU-212 have emerged
as interesting anticancer agents.29 The regio and stereoselective
formation of the double bond is key to the generation of these
(E)-stilbenes. As an extension of the disiloxane methodology,
the developement of an efficient method for the synthesis of
unsymmetrical trans-stilbenes by reacting differentially subsituted
bissilyl olefins (15) under sequential palladium cross couplings
with aryl halides using fluoride free conditions followed by fluoride
induced activation conditions was investigated (Scheme 7). In a
similar strategy, Denmark et al. synthesised a selection of unsym-
metrical 1,4-disubstituted 1,3-butadienes from the sequential cross
coupling of 1,4-bissilylbutadienes using a silanol and thienylsilane
as the two distinct silicon sources.23 Likewise, Hiyama et al.
performed a fluoride induced double cross coupling of a 1,2-
bissilylated alkene to generate a trans-stilbene.17 Herein, the unique
feature of our bissilyl olefin (15) is that one silicon substituent
cross couples readily under base activation whilst the other silyl
group requires the presence of fluoride to enable coupling to occur.
Selection of the appropriate reaction conditions allows the silyl
substituents to be distinguished. Most significantly, by following
this procedure disubstituted stilbenes are generated from readily
available aryl halides, mitigating the use of acetylene gas or the
requirement for terminal alkynes which have limited commercial
availability.
Scheme 4 Fluoride free cross coupling of electron rich aryl iodides with
phenyl substituted vinyldisiloxane.
Application of these modified conditions to the coupling of
alkyl subsituted vinyldisiloxanes did result in an improvement in
the regioselectivity for the trans coupled products; however, the
isolated yields remained low (Scheme 5). Vinyldisiloxanes 3e and
3f were cross coupled with 4-iodoacetophenone using the modified
reaction conditions: KOH (7 equiv), Pd(dba)2 (2.5 mol%), P(o-
tolyl)3 (5 mol%), MeOH, 80 ◦C. Only the (E)-isomers were
observed on inspecting the crude 1H-NMR spectra; however,
extensive reduction and homo-coupling of the starting aryl iodide
was also seen. This resulted in poor isolated yields of the desired
coupled products.
Scheme 5 Fluoride free cross coupling of 4-iodoacetophenone with alkyl
substituted vinyldisiloxanes.
The high level of regioselectivity for the ipso coupled product
was maintained during the cross coupling of alkyl subsituted
vinyldisiloxanes when fluoride induced conditions were employed
(TBAF) (Scheme 6).22 In the coupling of vinyldisiloxane 3e with 4-
iodoacetophenone under fluoride activation conditions excellent
selectivity was observed for the ipso coupled product on examining
the 1H-NMR spectra of the crude reaction mixture. No cine
product was visible. It has emerged that the coupling reaction is
highly dependent upon the activation source: with better selectivity
Scheme 7 Bissilyl strategy for the synthesis of unsymmetrical alkenes.
The bissilyl olefin (15) was generated by (tBu3P)Pt(DVDS)
catalysed hydrosilylation of the commercially available trimethylsi-
lylacetylene with tetramethyldisiloxane. The bissilyl disiloxane (15)
was produced in a 70% yield, with excellent regioselectivity, only
1
the (E)-isomer being observed by H-NMR spectroscopy. Initial
base activated cross coupling with the bissilyl disiloxane were
disappointing, with loss of (E)-selectivity being observed (E/Z,
2/1). After a broad optimisation screen of the reaction conditions
and the introduction of ligands, excellent selectivity for the (E)-
isomer (Scheme 8, 16a & 16b) was achieved. Good (E)-selectivity
was maintained in the subsequent fluoride activated palladium
catalysed cross coupling of the (E)-vinyltrimethylsilanes. The
unsymmetrical disubstituted olefins (Scheme 8, 4n & 4d) were
generated with excellent (E)-selectivity.
Scheme 6 Fluoride induced cross coupling of an alkyl vinyldisilane.
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‘masked’ silanols; which, were able to cross couple under base or
fluoride induced conditions with retention of the double bond
geometry. The developed protocol utilised inexpensive reagents
and was operationally simple. The hydrosilylation/coupling pro-
cess offers an effective method for obtaining disubstituted double
bonds with excellent geometrical purity; ultimately, generating the
products in good yields and under mild conditions.
The disiloxane methodology has successfully been applied to
the synthesis of unsymmetrical stilbenes and cyclic structures. The
sequential palladium catalysed cross coupling of the bissilyl alkene
has enabled the functionalisation of both groups around a (E)-
disubstituted alkene. The unsymmetrical (E)-alkenes were gener-
ated with excellent selectivity from easy to handle and readily avail-
able starting materials avoiding the use of acetylene gas or terminal
alkynes with limited commercial availablility. Synthesis of the
synthetically challenging vinyl-aryl-lactone macrocyclic scaffold
was achieved with excellent selectivity via a palladium catalysed
intramolecular cyclisation of the intermediate vinyldisiloxane.
The development of disiloxanes as effective cross coupling
partners has continued to build the Hiyama reaction into a
viable and practical alternative to the existing strategies for
making disubstituted double bonds. This methodology could find
applications in natural product synthesis and in the synthesis of
biologically active compounds within the pharmaceutical industry.
To expand upon the disiloxane-mediated methodology, explo-
ration into the efficient and mild coupling of aryl and heteroaryl
disiloxanes is ongoing and results will be reported in due course.
Scheme 8 Synthesis of unsymmetrical (E)-stilbenes.
Intramolecular cyclisation
To expand on the disiloxane methodology further, the potential
to form lactones via an intramolecular Hiyama cross coupling
reaction was explored (Scheme 9). Cyclic structures containing
the vinyl-aryl-lactone motif are common architectures found in
natural products and are typically constructed via a Stille or
Suzuki cross coupling.30 The developement of methodology to
construct these synthetically challenging scaffolds from inexpen-
sive and readily synthesised vinyldisiloxanes would be appealing,
mitigating the use of toxic or unstable reagents.
Experimental Section
General information
All experiments were carried out under an atmosphere of nitrogen,
using anhydrous solvents, unless otherwise stated. All chemicals
were purchased from Sigma–Aldrich, Strem or Fluorochem.
Room temperature refers to 20–25 ◦C. Analytical thin layer
chromatography was carried out on Merck Kieselgel 60 F254 plates
with visualisation by ultraviolet light or staining with potassium
permanganatemadeusingastandardprocedure. Retentionfactors
(Rf ) are quoted to 0.01. Flash column chromatography was
performed using Merck Kieselgel 60 (230–400 mesh) or biotage
silica columns under a positive pressure of nitrogen. Infra-red
spectra were recorded on a Perkin Elmer Spectrum One FT-IR
spectrometer fitted with an Attenuated Total Reflectance (ATR)
Scheme 9 Intra-molecular Hiyama cross coupling of disiloxanes.
Using standard reaction conditions for ester formation, the sub-
stituted terminal alkyne (19) was isolated in an excellent yield. Hy-
drosilylation of the alkyne proceeded with excellent selectivity for
the (E)-isomer when catalysed by the Pt-complex; even in the pres-
ence of an aryl iodide within the molecule. The (E)-disiloxane was
isolated in a moderate yield. In the initial cyclisation attempts 10
equivalents of TBAF were used; however, this predominately led to
protodesilylation, with only trace amounts of the desired product
being observed. Additionally, at higher concentrations, cyclic
dimer formation was also observed. Reducing the equivalents of
TBAF and increasing the dilution resulted in a modest yield of
desired product being isolated. Pleasingly, these early results high-
light the potential of disiloxanes to participate in intramolecular
cross coupling reactions. With further investigation we envisage
that this approach will offer an attractive alternative to existing
methods commonly used to construct these difficult scaffolds.
sampling accessory as neat films. Maximum absorbance (vmax
)
are quoted in wavenumbers (cm-1) and the abbreviations used
to describe the absorbance intensity are: w, weak; m, medium; s,
strong. Proton nuclear magnetic resonance (1H-NMR) and carbon
nuclear magnetic resonance (13C-NMR) were recorded using
ambient probe temperatures on the following instruments: Bruker
DXP 400, Bruker Avance DXP 400, Bruker Avance 500 BB-ATM,
Bruker Avance Cyro 500. The following deuterated solvents were
used: chloroform (CDCl3) and methanol (CD3OD). 1H-NMR
chemical shifts (d) are quoted in ppm relative to the residual non-
deuterated solvent peak and coupling constants (J) are quoted to
the nearest 0.1 Hertz (Hz). Spectral data is reported as follows:
chemical shift, integration, multiplicity [s, singlet; d, doublet; t,
triplet; q, quartet; sept, septuplet; m, multiplet; br, broad; or as a
combination of these, e.g. br s, dd etc.], coupling constant(s) and
Conclusions
The synthesis and cross coupling of vinyldisiloxanes has been de-
veloped creating an attractive atom efficient alternative to exisiting
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1
assignment. Proton assignment is supported by COSY (2D H–
(s, C C). dH (400 MHz, CDCl3) 8.20 (4H, d, J = 8.8 Hz, Ar
CH), 7.56 (4H, d, J = 8.8 Hz, Ar CH), 7.00 (2H, d, J = 19.1 Hz,
SiCH CHAr), 6.65 (2H, d, J = 19.1 Hz, SiCH CHAr), 0.31
(12H, s, Si(CH3)2). dC (101 MHz, CDCl3) 147.7 (Ar CNO2),
144.4 (Ar C), 142.3 (SiCH CH), 134.8 (SiCH CH), 127.4 (Ar
CH), 124.3 (Ar CH). LCMS (A) Rt 1.65 min, [M+H2O]+ 445.9.
HRMS (ESI) m/z found 429.1314, C20H25N2O5Si2 (MH+) requires
429.1302 (D = 2.8 ppm).
1H) spectra where necessary. Carbon assignment is supported by
DEPT editing and HMQC (2D one bond H–13C) correlations
1
where necessary. High resolution mass spectrometry (HRMS)
was carried out with a Micromass Q-TOF or a Micromass
LCT premier spectrometer using electrospray ionisation (ESI) or
electron ionisation (EI) and the calculated mass value relative to
found mass value is within the error limits of 5 ppm mass units.
Low resolution mass spectrometry (LCMS) was carried out using
either method LCMS (A) or LCMS (B). LCMS (A): Acquity
UPLC BEH C18 column (50mmx2.1mm i.d. 1.7 mm packing
diameter) at 40 ◦C. Solvent A = 0.1% v/v solution of formic
acid in water. Solvent B = 0.1% v/v solution of formic acid in
acetonitrile. The gradient employed was over 2 min going from
100% A to 100% B at a flow rate of 1 ml min-1. LCMS (B):
ABZ++ column. Solvent A = 1% v/v solution of formic acid
and 10 mM ammonium acetate in water. Solvent B = 0.05% v/v
solution of formic acid and 5% water in acetonitrile. The gradient
was employed over 8 min going from 100% A to 100% B at a
flow rate of 5 ml min-1. The UV detection was an averaged signal
from wavelength of 210 nm to 350 nm and mass spectra were
recorded on a mass spectrometer using alternate-scan positive
and negative mode electrospray ionisation. Melting points were
carried out using a Buchi melting point B545 apparatus and are
uncorrected.
(E)-b-Di-(4-methoxystyryl)-tetramethyldisiloxane (3c)
Following general method A, the crude residue was puri-
fied by flash silica column chromatography eluting with a
stepped gradient of dichloromethane : petroleum ether 40–60
(0 : 100 → 20 : 80) to yield product as a white solid (91%).
Rf 0.46 [dichloromethane : petroleum ether 40–60 (50 : 50)]. vmax
(neat)/cm-1 2959 (m, C–H), 2839 (w, C–H), 1602 (s, C C), 1571
(w, C C), 1506 (s, C C). dH (500 MHz, CDCl3) 7.36 (4H, d,
J = 8.8 Hz, Ar CH), 6.90 (2H, d, J = 19.2 Hz, SiCH CHAr),
6.85 (4H, d, J = 8.8 Hz, Ar CH), 6.28 (2H, d, J = 19.2 Hz,
SiCH CHAr), 3.82 (6H, s, OCH3), 0.23 (12H, s, Si(CH3)2). dC
(125 MHz, CDCl3) 159.7 (Ar COCH3), 143.7 (SiCH CH), 131.1
(Ar C), 127.8 (Ar CH), 125.9 (Ar CH), 113.9 (SiCH CH), 55.3
(OCH3), 0.9 (Si(CH3)2). m.p. 58.0–58.6 ◦C. HRMS (ESI) m/z
found 421.1626, C22H30O3Si2Na (MNa+) requires 421.1621 (D =
1.1 ppm).
General method A, for the hydrosilylation of terminal alkynes
(E)-b-Di-(3-pyridylvinyl)-tetramethyldisiloxane (3d)
A solution of tri-tert-butylphosphine (0.1 mol%, 1.0 M in toluene)
was added to a solution of platinum(0)-1,3-divinyl-1,1,3,3-
tetramethyldisiloxane complex (0.1 mol%, 0.1 M in xylenes) under
N2 and stirred for 5 min. On cooling the reaction to 0 ◦C,
1,1,3,3-tetramethyldisiloxane (11) (1 equiv) in anhydrous toluene
(~ 0.13 ml per mmol disiloxane) was added followed by terminal
alkyne (10) (2 equiv) in anhydrous toluene (~ 0.07 ml per mmol
alkyne). The reaction mixture was stirred at room temperature
for 16 h. Solvent was removed and crude residue purified by flash
silica chromatography to yield vinyldisiloxane (3).
Following general method A except heated reaction at 60 ◦C, the
crude residue was purified by flash silica column chromatography
eluting with a gradient of ethyl acetate : cyclohexane (25 : 75 →
100 : 0) to yield product as a colourless oil (94%). Rf 0.21 [ethyl
acetate]. vmax (neat)/cm-1 2957 (w, C–H), 1606 (m, C C), 1566 (w,
C
C). dH (400 MHz, CDCl3) 8.63 (2H, d, J = 2.0 Hz, Ar CH),
8.49 (2H, dd, J = 4.8, 1.5 Hz, Ar CH), 7.74 (2H, ddd, J = 7.9,
2.0, 1.9 Hz, Ar CH), 7.23–7.28 (2H, m, Ar CH), 6.94 (2H, d, J =
19.1 Hz, SiCH CHAr), 6.54 (2H, d, J = 19.3 Hz, SiCH CHAr),
0.28 (12H, s, Si(CH3)2). dC (101 MHz, CDCl3) 149.2 (Ar CH),
148.7 (Ar CH), 140.8 (SiCH CH), 133.4 (Ar C), 132.8 (Ar CH),
131.5 (SiCH CH), 123.5 (Ar CH), 0.8 (Si(CH3)2). LCMS (A)
Rt 0.96 min, [M+H]+ 340.9. HRMS (ESI) m/z found 341.1494,
C18H25N2OSi2 (MH+) requires 341.1505 (D = -3.2 ppm).
(E)-b-Distyryltetramethyldisiloxane (3a)31
Following general method A, the crude product was purified
by flash silica column chromatography eluting with a gradient
of dichloromethane : cyclohexane (0 : 100 → 50 : 50) to yield the
product as a colourless oil (96%). Rf 0.39 [petroleum ether 40–60].
vmax (neat)/cm-1 2944 (m, C–H), 2867 (m, C–H), 1641 (w, C C),
1516 (s, C C). dH (400 MHz, CDCl3) 7.44 (4H, d, J = 7.3 Hz,
o-Ar CH), 7.33 (4H, t, J = 7.4 Hz, m-Ar CH), 7.24–7.30 (2H, m,
p-Ar CH), 6.97 (2H, d, J = 19.3 Hz, SiCH CHAr), 6.46 (2H, d,
J = 19.1 Hz, SiCH CH), 0.27 (12H, s, Si(CH3)2). dC (101 MHz,
CDCl3) 144.3 (SiCH CH), 138.2 (Ar C), 128.6 (Ar CH), 128.5
(SiCH CH), 128.2 (Ar CH), 126.5 (Ar CH), 0.9 (Si(CH3)2).
(E)-b-Di-(5-methylhex-1-enyl)-tetramethyldisiloxane (3e)
Following general method A, the crude residue was purified by
flash silica column chromatography eluting with cyclohexane
(100%) to yield product as a colourless oil (89%). Rf 0.42
[cyclohexane]. vmax (neat)/cm-1 2956 (m, C–H), 2928 (w, C–H),
2849 (w, C–H), 1619 (m, C C). dH (400 MHz, CDCl3) 6.10
(2H, dt, J = 18.6, 6.3 Hz, SiCH CHCH2), 5.57–5.65 (2 H,
m, SiCH CH), 2.07–2.15 (4H, m, SiCH CHCH2), 1.51–1.62
(2H, m, CH(CH3)2), 1.25–1.33 (4H, m, CH2CH(CH3)2), 0.90
(12H, d, J = 6.5 Hz, CH(CH3)2), 0.12 (12H, s, Si(CH3)2). dC
(101 MHz, CDCl3) 148.6 (SiCH CH), 129.5 (SiCH CH), 38.1
(CH2CH(CH3)2), 34.8 (SiCH CHCH2), 28.0 (CH(CH3)2), 22.9
(CH(CH3)2), 1.2 (Si(CH3)2). HRMS (ESI) m/z found 349.2347,
C18H38OSi2Na (MNa+) requires 349.2353 (D = 1.9 ppm).
(E)-b-Di-(4-nitrostyryl)-tetramethyldisiloxane (3b)
Following general method A, the crude residue was purified by
flash silica column chromatography eluting with a gradient of
dichloromethane : cyclohexane (0 : 100 → 50 : 50) to yield product
as a colourless oil (90%). Rf 0.13 [dichloromethane : cyclohexane
(30 : 70)]. vmax (neat)/cm-1 2961 (w, C–H), 1589 (m, C C), 1512
510 | Org. Biomol. Chem., 2011, 9, 504–515
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(E)-b-Di-(4-tert-butyldimethylsilanyloxy)but-1-
(E)-1-(4-Styrylphenyl)ethanone (4a)32
enyl)tetramethyldisiloxane (3f)
Following general method B, the crude residue purified
by flash silica chromatography eluting with a gradient of
dichloromethane : hexane (0 : 100 → 10 : 90 → 20 : 80 → 30 : 70)
Following general method A, the crude residue was purified by
flash silica column chromatography eluting with a gradient of
dichloromethane : cyclohexane (0 : 100 → 25 : 75) to yield product
as a colourless oil (89%). Rf 0.48 [dichloromethane : cyclohexane
(50 : 50)]. vmax (neat)/cm-1 2955 (w, C–H), 2930 (w, C–H), 2858
(w, C–H), 1620 (w, C C). dH (400 MHz, CDCl3) 6.09 (2H, dt,
J = 18.8, 6.3 Hz, SiCH CHCH2), 5.68 (2H, d, J = 18.6 Hz,
SiCH CH), 3.68 (4H, t, J = 6.8 Hz, CH2CH2O), 2.34 (4H, q,
J = 6.5 Hz, SiCH CHCH2), 0.90 (18H, s, Si(CH3)2C(CH3)3),
0.12 (12H, s, Si(CH3)2), 0.06 (12H, s, Si(CH3)2C(CH3)3). dC
(101 MHz, CDCl3) 144.3 (SiCH CH), 131.9 (SiCH CH), 62.6
(CH2CH2O), 40.1 (SiCH CHCH2), 26.0 (Si(CH3)2C(CH3)3),
18.4 (Si(CH3)2C(CH3)3), 0.8 (Si(CH3)2), -5.2 (Si(CH3)2C(CH3)3).
HRMS (ESI) m/z found 525.3069, C24H54O3Si4Na (MNa+) re-
quires 525.3048 (D = 4.0 ppm).
to yield the product as
a white solid (91%). Rf 0.17
[dichloromethane : hexane (30 : 70)]. vmax (neat)/cm-1 3083 (w, C–
H), 3022 (w, C–H), 2956 (w, C–H), 2922 (C–H), 1676 (s, C O),
1594 (w, C C), 1577 (w, C C), 1558 (w, C C). dH (400 MHz,
CDCl3) 7.95 (2H, d, J = 8.4 Hz, Ar CH), 7.58 (2H, d, J = 8.4 Hz, Ar
CH), 7.55–7.53 (2H, m, Ar CH), 7.40–7.37 (2H, m, Ar CH), 7.32–
7.29 (1H, m, Ar CH), 7.22 (1H, d, J = 16.3 Hz, ArCH CHAr),
7.12 (1H, d, J = 16.3 Hz, ArCH CHAr), 2.60 (3H, s, C OCH3).
dC (101 MHz, CDCl3) 197.8 (C O), 142.4 (Ar CCOCH3), 137.1
(Ar C), 136.4 (Ar C), 131.9 (ArCH CHAr), 129.3 (Ar CH), 129.2
(Ar CH), 128.7 (Ar CH), 127.9 (ArCH CHAr), 127.2 (Ar CH),
126.9 (Ar CH), 30.1 (C OCH3). m.p. 143.2–144.5 ◦C (lit. value
139–141 ◦C).32 LCMS (A) Rt 1.24 min, [M+H]+ 222.9.
(E)-1-Styryl-3-(trifluoromethyl)benzene (4b)33
(E)-b-Di-(3,3-dimethylbut-1-enyl)-tetramethyldisiloxane (3g)
Following general method B, the crude residue was purified by
flash silica column chromatography eluting with cyclohexane
(100%) to yield the product as a white solid (91%). Rf 0.45
[cyclohexane]. vmax (neat)/cm-1 3038 (w, C–H), 1575 (w, C C).
dH (400 MHz, CDCl3) 7.84 (1H, s, Ar CH), 7.73 (1H, d, J =
7.8 Hz, Ar CH), 7.58–7.64 (3H, m, Ar CH), 7.51–7.57 (1H,
m, Ar CH), 7.46–7.50 (2H, m, Ar CH), 7.36–7.43 (1H, m, Ar
CH), 7.25 (1H, d, J = 16.0 Hz, ArCH CHAr), 7.18 (1H, d, J =
16.0 Hz, ArCH CHAr). dF (376 MHz, CDCl3) -63.14 (3F, s).
dC (101 MHz, CDCl3) 138.1 (Ar C), 136.6 (Ar C), 131.1 (q, J =
31.9 Hz, Ar CCF3), 130.5 (ArCH CHAr), 129.5 (Ar CH), 129.1
(Ar CH), 128.8 (Ar CH), 128.2 (Ar CH), 127.1 (ArCH CHAr),
126.7 (Ar CH), 124.2 (q, J = 273.7 Hz, CF3), 124.0 (q, J = 4.0 Hz,
Ar CH), 123.1 (q, J = 3.7 Hz, Ar CH). m.p. 66.6–67.4 ◦C (lit. value
67–68 ◦C).34
Following general method A, the crude residue was purified
by flash silica column chromatography eluting with cyclohex-
ane (100%) to yield product as a colourless oil (84%). Rf
0.48 [cyclohexane]. vmax (neat)/cm-1 2958 (m, C–H), 1615 (m,
C
C). dH (400 MHz, CDCl3) 6.10 (2H, d, J = 19.1 Hz,
SiCH CH), 5.51 (2H, d, J = 19.1 Hz, SiCH CH), 1.01
(18H, s, C(CH3)3), 0.12 (12H, s, Si(CH3)2). dC (101 MHz, CDCl3)
158.1 (SiCH CH), 122.6 (SiCH CH), 34.9 (C(CH3)3), 29.0
(C(CH3)3), 0.9 (Si(CH3)2). HRMS (ESI) m/z found 321.2044,
C16H34OSi2Na (MNa+) requires 321.2040 (D = -1.2 ppm).
(E)-b-Di-(3-hydroxy-3-methylbut-1-enyl)-tetramethyldisiloxane
(3h)
Following general method A, the crude residue was purified by
flash silica column chromatography eluting with a stepped gradi-
ent of diethyl ether : petroleum ether 40–60 (0 : 100 → 10 : 90 →
20 : 80→ 30 : 70 → 40 : 60) to yield product as a colourless oil
(94%). Rf 0.17 [diethyl ether : petroleum ether 40–60 (50 : 50)]. vmax
(neat)/cm-1 3352 (br m, O–H), 2971 (m, C–H), 1620 (w, C C).
(E)-1-Nitro-2-styrylbenzene (4c)35
Following general method B, the crude residue was puri-
fied by flash silica column chromatography eluting with a
gradient of dichloromethane : cyclohexane (0 : 100 → 25 : 75)
to yield the product as
a yellow solid (75%). Rf 0.45
d
H (400 MHz, CDCl3) 6.20 (2H, d, J = 19.1 Hz, SiCH CH), 5.78
[dichloromethane : cyclohexane (50 : 50)]. vmax (neat)/cm-1 3076 (w,
(2H, d, J = 18.9 Hz, SiCH CH), 1.30 (12H, s, COH(CH3)2), 0.14
(12H, s, Si(CH3)2). dC (101 MHz, CDCl3) 153.9 (SiCH CH),
124.3 (SiCH CH), 71.9 (COH(CH3)2), 29.3 (COH(CH3)2), 0.7
(Si(CH3)2). HRMS m/z found 325.1631, C14H30O3Si2Na (MNa+)
requires 325.1642 (D = 3.4 ppm).
C–H), 3022 (w, C–H), 2918 (w, C–H), 2850 (w, C–H), 1625 (w,
C
C), 1602 (w, C C), 1569 (m, C C). dH (400 MHz, CDCl3)
7.98 (1H, d, J = 8.8 Hz, Ar CH), 7.78 (1H, d, J = 7.8 Hz, Ar
CH), 7.58–7.65 (2H, m, Ar CH), 7.56 (2H, d, J = 7.5 Hz, Ar CH),
7.37–7.45 (3H, m, ArCH CHAr and Ar CH), 7.31–7.36 (1H, m,
Ar CH), 7.10 (1H, d, J = 16.1 Hz, ArCH CHAr). dC (101 MHz,
CDCl3) 148.0 (Ar CNO2), 136.5 (Ar C), 133.9 (Ar C), 133.0 (Ar
CH), 133.0 (ArCH CHAr), 128.8 (Ar CH), 128.6 (Ar CH), 128.1
(Ar CH), 127.9 (ArCH CHAr), 127.1 (Ar CH), 124.7 (Ar CH),
123.5 (Ar CH). m.p. 72.1–72.9 (lit. value 70–72 ◦C).36 LCMS (A)
Rt 1.30 min, [M+H]+ 225.9.
General method B, for Cross Coupling of Aryl Iodides
Vinyldisiloxane (3) (1 equiv), aryl iodide (12) (1.5 equiv), potas-
sium hydroxide (3 equiv) and Pd(dba)2 (2.5 mol%) in methanol
(~ 7 ml per mmol disiloxane) were stirred for 2–16 h. Reaction
mixture was partitioned between water and dichloromethane, sep-
arated, aqueous extracted further with dichloromethane. Organic
extracts were combined, dried (MgSO4), concentrated and crude
residues purified by flash silica chromatography to yield coupled
product (4).
(E)-3-Styrylpyridine (4d)32
Following general method B except heating the reaction at
70 ◦C, the crude residue was purified by flash silica column
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chromatography eluting with
a
gradient of dichlorome-
product as a yellow solid (70%). Rf 0.25 [dichloromethane]. vmax
(neat)/cm-1 2922 (w, C–H), 1671 (s, C O ketone), 1598 (s, C C),
1559 (m, C C). dH (400 MHz, CDCl3) 8.26 (2 H, d, J = 8.8 Hz, Ar
CH), 8.00 (2 H, d, J = 8.3 Hz, Ar CH), 7.69 (2 H, d, J = 8.8 Hz, Ar
CH), 7.65 (2 H, d, J = 8.3 Hz, Ar CH), 7.32 (1 H, d, J = 16.0 Hz,
ArCH CHAr), 7.26 (1 H, d, J = 16.0 Hz, ArCH CHAr), 2.64
(3 H, s, C OCH3). dC (101 MHz, CDCl3) 197.0 (C O), 146.9 (Ar
CNO2), 142.8 (Ar CCOCH3), 140.3 (Ar C), 136.6 (Ar C), 131.6
(ArCH CHAr), 128.7 (Ar CH), 128.6 (ArCH CHAr), 126.9
(Ar CH), 126.7 (Ar CH), 123.9 (A◦r CH), 26.3 (C OCH3). m.p.
188.2–193.8 ◦C (lit. value 194–197 C).38 LCMS (A) Rt 1.22 min,
[M - H]- 265.0. HRMS (ESI) m/z found 290.0792, C16H13NO3Na
(MNa+) requires 290.0788 (D = -1.5 ppm).
thane : hexane (0 : 100 → 50 : 50 → 100 : 0) to yield the product as
a white solid (56%). Rf 0.20 [ethyl acetate : cyclohexane (50 : 50)].
vmax (neat)/cm-1 3028 (w, C–H), 1687 (s, N C), 1638 (w, C C),
1568 (m, C C). dH (400 MHz, CDCl3) 8.73 (1H, s, Py CH), 8.50
(1H, d, J = 4.0 Hz, Py CH), 7.85 (1H, dt, J = 7.5, 4.0 Hz, Py CH),
7.54 (2H, d, J = 7.5 Hz, Ar CH), 7.39 (2H, t, J = 7.5 Hz, Ar CH),
7.25–7.34 (2H, m, Py CH and Ar CH), 7.18 (1H, d, J = 16.0 Hz,
ArCH CHAr), 7.08 (1H, d, J = 16.0 Hz, ArCH CHAr). dC
(101 MHz, CDCl3) 148.5 (Py CH), 136.6 (Ar or Py C), 133.0 (Ar
or Py C), 132.7 (Py CH), 130.8 (ArCH CHAr), 128.8 (Ar CH),
128.2 (Ar CH), 126.6 (Ar CH an◦d Py CH), 124.9 (ArCH CHAr),
◦
123.5 (Py CH). m.p. 77.6–79.9 C (lit. value 81–83 C).32 LCMS
(A) Rt 0.73 min, [M+H]+ 182.0.
(E)-1-(4-(4-methoxystyryl)phenyl)ethanone (4h)19
(E)-1-Methyl-4-styrylbenzene (4e)35
Following general method B, the crude residue was purified by
flash silica column chromatography eluting with a gradient of
dichloromethane : petroleum ether (50 : 50 → 70 : 30) to yield the
product as a yellow solid (83%). Rf 0.49 [ethyl acetate : petroleum
ether 40–60 (50 : 50)]. vmax (neat)/cm-1 3330–2842 (w, C–H), 1667
(s, C O), 1595 (m C C), 1559 (w, C C). dH (400 MHz, CDCl3)
7.93 (2 H, d, J = 8.4 Hz, Ar CH), 7.54 (2 H, d, J = 8.3 Hz, Ar CH),
7.47 (2 H, d, J = 8.7 Hz, Ar CH), 7.17 (1 H, d, J = 16.3 Hz,
ArCH CHAr), 6.99 (1 H, d, J = 16.3 Hz, ArCH CHAr),
6.91 (2 H, d, J = 8.7 Hz, Ar CH), 3.83 (3 H, s, OCH3), 2.59
(3 H, s, C OCH3). dC (100 MHz, CDCl3) 197.9 (C O), 160.3
(Ar C), 142.8 (Ar C), 136.0 (Ar C), 131.44 (CH), 129.9 (Ar C),
129.3 (CH), 128.8 (CH), 126.6 (CH), 125.7 (CH), 114.6 (CH),
55.7 (OCH3), 26.9 (C OCH3). LCMS (B) Rt 4.78 min, [M+H]+
253.2.
Following general method B except using potassium hydroxide
(7 equiv.), adding tri(o-tolyl)phosphine (5 mol%) and heating the
reaction mixture at 80 ◦C, the crude residue was purified by flash
silica column chromatography eluting with cyclohexane (100%) to
yield the product as a white solid (72%). Rf 0.38 [cyclohexane]. vmax
(neat)/cm-1 3023 (w, C–H), 2914 (w, C–H), 2856 (w, C–H), 1594
(w, C C), 1576 (w, C C). dH (400 MHz, CDCl3) 7.60 (2H, d, J =
7.5 Hz, Ar CH), 7.51 (2H, d, J = 8.0 Hz, Ar CH), 7.44 (2H, t, J =
7.5 Hz, Ar CH), 7.31–7.36 (1H, m, Ar CH), 7.26 (2H, d, J = 8.0 Hz,
Ar CH), 7.19 (1H, d, J = 16.0 Hz, ArCH CHAr), 7.14 (1H, d, J =
16.0 Hz, ArCH CHAr), 2.45 (3H, s, CH3). dC (101 MHz, CDCl3)
137.5 (Ar C), 134.5 (Ar C), 129.4 (Ar CH), 128.6 (Ar CH), 128.6
(Ar CH), 127.7 (ArCH CHAr), 127.4 (ArCH CHAr), 126.4
(Ar CH), 126.4 (Ar CH and Ar CMe), 21.3 (CH3). m.p. 119.7–
120.9 (lit. value 118–119 ◦C).37
(E)-1-(4-(2-(Pyridin-3-yl)vinyl)phenyl)ethanone (4i)39
(E)-1-Methoxy-4-styrylbenzene (4f)32
Following general method B except heating the reaction at 50 ◦C,
the crude residue was purified by flash silica column chromatogra-
phy eluting with a gradient of ethyl acetate : cyclohexane (25 : 75 →
100 : 0) to yield the product as a white solid (40.0 mg, 61%). Rf
Following general method B except using potassium hydrox-
ide (7 equiv.), adding tri(o-tolyl)phosphine (5 mol%) and
heating the reaction mixture at 80 ◦C, the crude residue
was purified by flash silica column chromatography eluting
with a gradient of dichloromethane : cyclohexane (0 : 100 →
25 : 75) to yield the product as a white solid (66%). Rf
0.40 [dichloromethane : petroleum ether 40–60 (40 : 60)]. vmax
(neat)/cm-1 3022 (w, C–H), 3003 (w, C–H), 2964 (w, C–H), 2838
(w, C–H), 1601 (w, C C), 1593 (w, C C), 1571 (w, C C),
1509 (w, C C). dH (400 MHz, CDCl3) 7.41 (2H, d, J = 7.4 Hz,
Ar CH), 7.38 (2H, d, J = 8.7 Hz, Ar CH), 7.28–7.24 (2H, m,
Ar CH), 7.17–7.13 (1H, m, Ar CH), 6.99 (1H, d, J = 16.3 Hz,
ArCH CHAr), 6.89 (1H, d, J = 16.3 Hz, ArCH CHAr), 6.82
(2H, d, J = 8.7 Hz, Ar CH), 3.75 (3H, s, OCH3). dC (101 MHz,
CDCl3) 159.7 (Ar COCH3), 138.1 (Ar C), 130.6 (Ar C), 129.0 (Ar
CH), 128.6 (ArCH CHAr), 128.1 (Ar CH), 127.6 (Ar CH), 127.0
(ArCH CHAr), 126.7 (Ar CH), 114.6 (Ar CH), 55.7 (OCH3).
0.30 [ethyl acetate]. vmax (neat)/cm-1 3021 (w, C–H), 1671 (s, C
O
ketone), 1599 (s, C C), 1558 (w, C C), 1583 (w, C C), 1571 (w,
C
C), 1561 (w, C C). dH (400 MHz, CDCl3) 8.83 (1 H, d, J =
1.8 Hz, Py CH), 8.60 (1 H, dd, J = 4.8, 1.5 Hz, Py CH), 8.05 (2 H,
d, J = 8.4 Hz, Ar CH), 7.93 (1 H, ddd, J = 8.1, 1.8, 1.5 Hz, Py CH),
7.68 (2 H, d, J = 8.4 Hz, Ar CH), 7.39 (1 H, dd, J = 8.1, 4.8 Hz, Py
CH), 7.27 (2 H, s, ArCH CHAr), 2.69 (3 H, s, C OCH3). dC
(101 MHz, CDCl3) 197.4 (C O), 149.2 (Py CH), 148.8 (Py CH),
141.2 (Ar CCOCH3), 136.5 (Py C), 133.0 (Py CH), 132.4 (Ar C),
129.6 (ArCH CHAr), 128.9 (Ar CH), 127.6 (ArCH CHAr),
126.7 ◦(Ar CH), 123.6 (Py CH), 26.6 (C OCH3). m.p. 106.5–
108.5 C (lit. value 99–101 ◦C).39 LCMS (A) Rt 0.69 min, [M+H]+
224.0.
◦
m.p. 130.5–132.2 ◦C (lit. value 134–136 C).32 LCMS (A) Rt
(E)-1-(4-(5-Methylhex-1-enyl)phenyl)ethanone (4j)40
1.39 min, [M+H]+ 211.0.
Following general method B, the crude residue was purified
by flash silica column chromatography eluting with a gradient
of dichloromethane : cyclohexane (0 : 100 → 100 : 0) to yield the
product as a colourless oil (19%). Rf 0.55 [dichloromethane].
vmax (neat)/cm-1 2955 (w, C–H), 2927 (w, C–H), 2869
(w, C–H), 2849 (w, C–H), 1679 (s, C O ketone), 1648 (w, C C),
(E)-1-(4-(4-Nitrostyryl)phenyl)ethanone (4g)38
Following general method B, the crude residue was purified
by flash silica column chromatography eluting with a gradient
of dichloromethane : cyclohexane (0 : 100 → 100 : 0) to yield the
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1601 (s, C C), 1563 (w, C C). dH (400 MHz, CDCl3) 7.89
(2H, d, J = 8.3 Hz, Ar CH), 7.41 (2H, d, J = 8.6 Hz, Ar CH),
6.33–6.47 (2H, m, ArCH CHCH2), 2.59 (3H, s, COCH3), 2.25
(2H, td, J = 7.7, 5.8 Hz, ArCH CHCH2), 1.62 (1H, apparent
sept, J = 6.5 Hz, CH(CH3)2), 1.34–1.42 (2H, m, CH2CH(CH3)2),
0.93 (6H, d, J = 6.8 Hz, CH(CH3)2). dC (101 MHz, CDCl3)
197.6 (C O), 142.7 (Ar CCOCH3), 135.3 (Ar C), 134.7
(CH CH), 128.7 (CH CH and Ar CH), 125.9 (Ar CH), 38.2
(CH2CH(CH3)2), 31.0 (ArCH CHCH2), 27.6 (CH(CH3)2), 26.5
(C OCH3), 22.5 (CH(CH3)2). LCMS (B) Rt 5.20 min, [M+H]+
217.28.
C–H), 1668 (s, C O, ketone), 1600 (m, C C), 1563 (m, C C).
dH (400 MHz, CDCl3) 7.90 (2H, d, J = 8.4 Hz, Ar CH), 7.45
(2H, d, J = 8.3 Hz, Ar CH), 6.64 (H, d, J = 16.1 Hz, CH CH),
6.47 (1H, d, J = 16.1 Hz, CH CH), 2.59 (3H, s, COCH3), 1.44
(6H, s, C(CH3)2OH). dC (101 MHz, CDCl3) 198.1 (C O), 142.2
(Ar CCOCH3), 140.9 (Ar CH), 136.3 (Ar CCH CH), 129.2
(CH CH), 126.9 (CH CH), 125.9 (Ar CH), 71.5 (C(CH3)2OH),
30.3 (C(CH3)2OH), 27.0 (C OCH3).
1,1,3,3-Tetramethyl-1,3-bis[2-(trimethylsilyl)ethenyl]-,(E,E)-
disiloxane (15)
Following general method A, except using ethynyl(trimethyl)silane
(2.2 equiv.) as the acetylene, the crude residue was purified by
flash silica column chromatography eluting with hexane (100%)
to yield product as a volatile colourless oil (70%). Rf 0.54
[hexane]. vmax (neat)/cm-1 2957 (w, C–H), 1407 (w, C C). dH
(400 MHz, CDCl3) 6.64 (2H, d, J = 22.6 Hz, SiCH CHSi(CH3)3),
6.53 (2H, d, J = 22.6 Hz, SiCH CHSi(CH3)3), 0.13 (12H, s,
Si(CH3)2), 0.07 (18H, s, Si(CH3)3). dC (101 MHz, CDCl3)
153.0 (SiCH CHSi(CH3)3), 151.5 (SiCH CHSi(CH3)3), 2.1
(Si(CH3)2), 0.03 (Si(CH3)3). HRMS (ESI) m/z found 353.1572,
C14H34OSi4Na (MNa+) requires 353.1579 (D = 2.0 ppm).
(E)-1-(4-(4-(tert-Butyldimethylsilyloxy)but-1-
enyl)phenyl)ethanone (4k)
Following general method B except heating the reaction at 50 ◦C,
the crude residue was purified by flash silica column chromatog-
raphy eluting with a gradient of dichloromethane : cyclohexane
(0 : 100 → 100 : 0) to yield the product as a colourless oil (8%).
Rf 0.35 [dichloromethane]. vmax (neat)/cm-1 2955 (w, C–H), 2929
(w, C–H), 2857 (w, C–H), 1683 (s, C O ketone), 1650 (w, C C),
1603 (s, C C), 1563 (w, C C). dH (400 MHz, CDCl3) 7.90 (2H,
d, J = 8.3 Hz, Ar CH), 7.42 (2H, d, J = 8.6 Hz, Ar CH), 6.34–6.53
(2H, m, ArCH CHCH2), 3.76 (2H, t, J = 6.5 Hz, CH2CH2O),
2.60 (3H, s, COCH3), 2.47 (2H, q, J = 6.6 Hz, ArCH CHCH2),
0.91 (9H, s, Si(CH3)2C(CH3)3), 0.07 (6H, s, Si(CH3)2C(CH3)3). dC
(101 MHz, CDCl3) 197.6 (C O), 142.4 (Ar CCOCH3), 135.5
(Ar C), 130.8 (CH CH), 130.7 (CH CH), 128.8 (Ar CH),
126.0 (Ar CH), 62.6 (CH2CH2O), 36.7 (ArCH CHCH2), 26.6
(C OCH3), 25.9 (Si(CH3)2C(CH3)3), 18.4 (Si(CH3)2C(CH3)3),
-5.2 (Si(CH3)2C(CH3)3). LCMS (B) Rt 5.37 min, [M+H]+ 305.20.
HRMS (ESI) m/z found 305.1938, C18H29O2Si (MH+) requires
305.1937 (D = 0.3 ppm).
General method C, for the synthesis of (E)-vinyltrimethylsilanes
1,1,3,3-tetramethyl-1,3-bis[2-(trimethylsilyl)ethenyl]-,(E,E)-
disiloxane (15) (1 equiv.), aryl iodide (1.8 equiv.) and potassium
hydroxide (6 equiv.) were dissolved in tbutanol (~ 30 ml per mmol
disiloxane).
Rac-2,2¢-bis(diphenylphosphino)-1,1¢-binaphthyl
(5 mol%) followed by bis(dibenzylideneacetone)palladium(0)
(5 mol%) were added and the reaction mixture was heated at
80 ◦C for 16–19 h. Reaction mixture was partitioned between
water and dichloromethane, separated, aqueous extracted further
with dichloromethane. Organic extracts were combined, dried
(MgSO4), concentrated and crude residue purified by flash silica
chromatography to yield the product (16).
(E)-1-(4-(3,3-Dimethylbut-1-enyl)phenyl)ethanone (4l)41
Following general method B except heating the reaction at 50 ◦C,
the crude residue was purified by flash silica column chromatog-
raphy eluting with a gradient of dichloromethane : cyclohexane
(0 : 100 → 50 : 50) to yield the product as a colourless oil (24%).
Rf 0.50 [dichloromethane]. vmax (neat)/cm-1 2960 (w, C–H), 2867
(w, C–H), 1682 (s, C O ketone), 1645 (w, C C), 1603 (s,
(E)-4-Nitrostyryltrimethylsilane (16a)42
Following general method C, the crude residue was
purified by flash silica column chromatography eluting
with dichloromethane : petroleum ether 40–60 (20 : 80) to
C
C), 1563 (w, C C). dH (400 MHz, CDCl3) 7.90 (2H, d,
J = 8.3 Hz, Ar CH), 7.44 (2H, d, J = 8.3 Hz, Ar CH), 6.31–
6.45 (2H, m, CH CH), 2.60 (3H, s, COCH3), 1.14 (9H, s,
C(CH3)3). dC (101 MHz, CDCl3) 197.7 (C O), 145.0 (CH CH),
142.9 (Ar CCOCH3), 135.4 (Ar C), 128.7 (Ar CH), 126.0 (Ar
CH), 123.9 (CH CH), 33.7 (C(CH3)3), 29.4 (C(CH3)3), 26.6
(C OCH3). LCMS (A) Rt 1.35 min, [M+H]+ 203.1. HRMS
(ESI) m/z found 203.1435, C14H19O (MH+) requires 203.1436
(D = -0.5 ppm).
yield product as
a bright yellow solid (45%). Rf 0.45
[dichloromethane : petroleum ether 40–60 (20 : 80)]. vmax
(neat)/cm-1 3645–3524 (w, C–H), 2958 (m, C–H), 1592 (m,
C
C), 1520 (m, C C). dH (400 MHz, CDCl3) 8.19 (2H, d,
J = 8.8 Hz, Ar CH), 7.55 (2H, d, J = 8.7 Hz, Ar CH), 6.92
(1H, d, J = 19.1 Hz, SiCH CHAr), 6.71 (1H, d, J = 19.1 Hz,
SiCH CHAr), 0.19 (9H, s, Si(CH3)3). dC (101 MHz, CDCl3)
147.1 (Ar CNO2), 144.4 (Ar C), 141.2 (Ar CH), 136.2 (Ar CH),
126.9 (SiCH CHAr), 123◦.9 (SiCH CHAr), -1.5 (Si(CH3)3).
m.p. 59 ◦C (lit. value 59–61 C).42
(E)-1-(4-(3-Hydroxy-3-methylbut-1-enyl)phenyl)ethanone (4m)
Following general method B, except using 5 equiv. of base
and heating to 50 ◦C, the crude was purified by flash silica
chromatography eluting with a gradient of petroleum ether 40–
60 : ethyl acetate (80 : 20 → 70 : 30 → 60 : 40) to yield the product as
a colourless oil (39%). Rf 0.30 [dichloromethane : petroleum ether
(40–60) (30 : 70)]. vmax (neat)/cm-1 3472 (w, O–H), 3220–2930 (w,
3-[(1E)-2-(trimethylsilyl)ethenyl]-pyridine (16b)43
Following general method C, the crude residue was purified by
flash silica column chromatography eluting with a gradient of
dichloromethane : methanol (99 : 1 → 98 : 2 → 97 : 3) to yield
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product as a brown oil (43%). Rf 0.38 [dichloromethane : methanol
(98 : 2)]. vmax (neat)/cm-1 3549–3424 (w, C–H), 2949 (m, C–
H), 2368 (s, C–H), 2313 (s, C–H), 1623 (w, C C). dH
(400 MHz, CDCl3) 8.61 (1H, d, J = 1.7 Hz, Py CH), 8.45
(1H, dd, J = 4.7, 1.3 Hz, Py CH), 7.75–7.72 (1H, m, Py
CH), 7.25–7.22 (1H, m, Py CH), 6.84 (1H, d, J = 19.2 Hz,
SiCH CHPy), 6.57 (1H, d, J = 19.2 Hz, SiCH CHpy), 0.16
(9H, s, Si(CH3)3). dC (101 MHz, CDCl3) 148.8 (Py CH), 148.5
(Py CH), 139.9 (Py C), 132.8 (Py CH), 132.6 (Py CH), 123.4
(SiCH CHPy), 119.6 (SiCH CHPy), -1.4 (Si(CH3)3). HRMS
(ESI) m/z found 178.1052, C10H16NSi (MH+) requires 178.1059
(D = -3.9 ppm).
CH2), 1.32 (10H, m, (CH2)5). dC (101 MHz, CDCl3) 166.7 (C O),
141.2 (Ar CH), 135.6 (Ar C), 132.4 (Ar CH), 130.8 (Ar CH), 127.8
(Ar CH), 93.9 (Ar CI), 84.7 (CH2C CH), 68.0 (CH2C CH),
65.8 (OCH2), 29.3 (CH2), 29.1 (CH2), 29.0 (CH2), 28.7 (CH2),
28.5 (CH2), 28.4 (CH2), 25.9 (CH2), 18.4 (CH2). HRMS (ESI)
m/z found 421.0651, C18H23O2INa (MNa+) requires 421.0641 (D =
-3.9 ppm).
(E)-Di-(11-(2-iodobenzoyloxy)undec-1-enyl)tetramethyldisiloxane
(20)
A solution of tri-tert-butylphosphine (4.0 mL, 0.0024 mmol, 1.0 M
in toluene) was added to a solution of platinum(0)-1,3-divinyl-
1,1,3,3-tetramethyldisiloxane complex (60 mL, 0.0024 mmol, 2%
in xylenes) under N2 and stirred for 5 min. On cooling the reaction
to 0 ◦C, 1,1,3,3-tetramethyldisiloxane (0.085 mL, 0.5 mmol)
in anhydrous toluene was added followed by 10-undecyn-1-ol
(400 mg, 1.0 mmol) in anhydrous toluene. The reaction mixture
was stirred at room temperature for 16 h. The solvent was removed
under reduced pressure and the crude residue purified by flash
silica column chromatography eluting with a gradient of ethyl
acetate : petroleum ether (40–60) (0 : 100 → 5 : 95) to yield product
as a colourless oil (0.2 g, 43%). Rf 0.55 [ethyl acetate : petroleum
ether (40–60) (5 : 95)]. vmax (neat)/cm-1 2853 (m, C–H), 1729 (s,
General method D, for the synthesis of unsymmetrical stilbenes
To a solution of (E)-vinyltrimethylsilane (16) (1 equiv.) and
aryl iodide (1 equiv.) in tetrahydrofuran (~ 4.5 ml per mmol
silane) was added a tetrabutylammonium fluoride solution (1.0 M
in tetrahydrofuran, 3 equiv.) and bis(dibenzylideneacetone)-
palladium(0) (5 mol%). The reaction mixture was stirred at room
temperature for 16–19 h, then filtered through silica eluting with
dichloromethane and the filtrate was concentrated under reduced
pressure. The crude residue was purified by flash silica column
chromatography to yield the product.
C
O ester), 1618 (w, C C), 1584 (w, C C). dH (400 MHz,
(E)-4-Methyl-4¢-nitro-stilbene (4n)44
CDCl3) 7.98 (2H, dd, J = 8, 1.2 Hz, Ar CH), 7.77 (2H, dd, J =
7.6, 1.6 Hz, Ar CH), 7.39 (2H, td, J = 7.6, 1.2 Hz, Ar CH), 7.13
(2H, td, J = 7.6, 1.6 Hz, Ar CH), 6.08 (2H, dt, J = 18.4, 6.4 Hz,
SiCH CH), 5.59 (2H, d, J = 18.4 Hz, SiCH CH), 4.33 (4H, t, J =
6.8 Hz, OCH2), 2.06 (4H, m, CH2), 1.77 (4H, m, CH2), 1.31 (24H,
m, (CH2)6), 0.12 (12H, s, Si(CH3)2). dC (101 MHz, CDCl3) 166.7
(C O), 148.0 (SiCH CH), 141.2 (Ar CH), 135.6 (Ar C), 132.5
(Ar CH), 130.8 (Ar CH), 129.4 (SiCH CH), 127.9 (Ar CH),
93.9 (Ar CI), 65.9 (OCH2), 36.5 (CH2), 29.5 (CH2), 29.4 (CH2),
29.2 (CH2), 29.2 (CH2), 28.6 (CH2), 28.6 (CH2), 26.0 (CH2), 0.8
(Si(CH3)2). HRMS (EI) m/z found 930.8815, C40H60I2O5Si2 (M+)
requires 930.8813 (D = 0.7 ppm).
Following general method D, the crude residue was purified by
flash silica column chromatography eluting with a gradient of
dichloromethane : petroleum ether (40–60) (0 : 100 → 10 : 90 →
20 : 80 → 30 : 70) to yield product as a yellow solid (32%). Rf
0.30 [dichloromethane : petroleum ether (40–60) (30 : 70)]. vmax
(neat)/cm-1 3541–3472 (w, C–H), 1710 (s, C O, ketone), 1594
(w, C C), 1518 (m, C C). dH (400 MHz, CDCl3) 8.21 (2H, d,
J = 8.9 Hz, Ar CH), 7.62 (2H, d, J = 8.7 Hz, Ar CH), 7.45 (2H,
d, J = 8.1 Hz, Ar CH), 7.25 (1H, d, J = 16.4 Hz, CH CH), 7.21
(2H, d, J = 8.0 Hz, Ar CH), 7.10 (1H, d, J = 16.3 Hz, CH CH),
2.39 (3H, s, CH3). dC (101 MHz, CDCl3) 146.6 (Ar CNO2), 142.7
(Ar C), 133.3 (Ar C), 129.6 (Ar CCH3), 127.0 (Ar CH), 126.7
(Ar CH), 126.1 (Ar CH), 125.3 (Ar CH), 124.1 (ArCH CHAr),
122.◦7 (ArCH CHAr), 21.4 (CH3). m.p. 150 ◦C (lit. value
150 C).45
(E)-4,5,6,7,8,9,10,11-Octahydrobenzo[c][1]oxacyclopentadecin-
1(3H)-one (21)47
To a solution of anhydrous tetrahydrofuran and allyl palladium
chloride (12 mg, 30 mol%) under N2 at 0 ◦C, was added
vinyldisiloxane (21) (100 mg, 0.11 mmol) in tetrahydrofuran and
tetrabutylammonium fluoride (0.25 mL, 0.25 mmol) dropwise.
The reaction mixture was stirred at 0 ◦C for 5 h, and then
warmed to room temperature and stirred overnight. The solvent
was removed under reduced pressure. The crude residue was
purified by flash silica column chromatography eluting ethyl
acetate : petroleum ether (40–60) (5 : 95) followed by preparative
TLC eluting dichloromethane : petroleum ether (40–60) (40 : 60)
to yield the product as a colourless oil (12 mg, 22%). Rf
0.40 [dichloromethane : petroleum ether (40–60) (40 : 60)]. vmax
(neat)/cm-1 2928 (m, C–H), 2855 (m, C–H), 1710 (w, C O ester),
1649 (m, C C), 1601 (m, C C), 1447 (m, C–H). dH (400 MHz,
CDCl3) 7.64 (1H, dd, J = 8.0, 1.6 Hz, Ar CH), 7.40 (1H, d, J = 8.0,
Ar CH), 7.33 (1H, td, J = 8.0, 1.2 Hz, Ar CH), 7.17 (1H, td, J =
8.0, 1.2 Hz, Ar CH), 6.88 (1H, d, J = 15.6 Hz, CH CHAr), 5.92
(1H, dt, J = 15.6, 7.6 Hz, CH CHAr), 4.33 (2H, t, J = 5.2 Hz,
Undec-10-yn-1-yl 2-iodobenzoate (19)46
To a solution of 2-iodobenzoic acid (0.730 g, 2.97 mmol) in
dichloromethane was added undec-10-yn-1-ol (0.5 g, 2.97 mmol),
N,N¢-dicyclohexylcarbodiimide (0.72 g, 3.5 mmol) and then 4-
(dimethylamino)-pyridine (0.09 g, 0.75 mmol). The reaction was
stirred at room temperature for 16 h. The reaction mixture was
concentrated and purified by flash silica column chromatography
eluting with dichloromethane to yield the product as a colourless
oil (1.12 g, 95%). Rf 0.65 [ethyl acetate : petroleum ether (40–60)
(5 : 95)]. vmax (neat)/cm-1 3303 (m, C–H alkyne), 2927 (m, C–H),
2855 (w, C–H), 2117 (w, C C), 1726 (s, C O, ester), 1584 (m,
C
C), 1562 (w, C C). dH (400 MHz, CDCl3) 7.91 (1H, dd, J =
7.6, 0.8 Hz, Ar CH), 7.71 (1H, dd, J = 7.6, 1.6 Hz, Ar CH), 7.33
(1H, td, J = 7.6, 1.2 Hz, Ar CH), 7.07 (1H, td, J = 7.6, 1.6 Hz, Ar
CH), 4.26 (2H, t, J = 6.4, OCH2), 2.10 (2H, dt, J = 7.2, 2.8 Hz CH2),
1.86 (1H, t, J = 2.4 Hz, C CH), 1.70 (2H, m, CH2), 1.44 (2H, m,
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OCH2), 1.64 (2H, m, CH2), 2.19 (2H, m, CH2), 1.33 (12H, m,
(CH2)6). dC (101 MHz, CDCl3) 167.8 (C), 137.4 (C), 135.0 (CH),
131.7 (CH), 130.4 (C), 130.3 (CH), 129.8 (CH), 127.8 (CH), 127.0
(CH), 65.5 (CH2), 31.7 (CH2), 29.3 (CH2), 28.1 (CH2), 27.5 (CH2),
26.4 (CH2), 25.7 (CH2), 25.2 (CH2), 24.5 (CH2). HRMS (EI) m/z
found 273.1857, C18H25O2 (M+) requires 273.1855 (D = 0.7 ppm).
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