Synthesis of 1,4-diethynyl- and 1,1,4,4-tetraethynylbutatrienes

Article abstract of DOI:10.1002/hlca.200490277

In this paper, we report the synthesis and opto-electronic properties of differentially substituted 1,4-diethynyl- and 1,1,4,4-tetraethynylbuta-1,2,3- trienes. These novel chromophores greatly extend the series of building modules for oxidative coupling,

Full text of DOI:10.1002/hlca.200490277

Helvetica Chimica Acta ± Vol. 87 (2004)
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Synthesis of 1,4-Diethynyl- and 1,1,4,4-Tetraethynylbutatrienes
by Audrey Auffrant and François Diederich*
Laboratorium für Organische Chemie, ETH-Hönggerberg, HCI, CH-8093Zürich
(e-mail: diederich@org.chem.ethz.ch)
and
Corinne Boudon, Jean-Paul Gisselbrecht, and Maurice Gross
Laboratoire dꢀElectrochimie et de Chimie Physique du Corps Solide, UMR 7512, C.N.R.S.,
Â
Universite Louis Pasteur, 4 rue Blaise Pascal, F-6700 Strasbourg
In this paper, we report the synthesis and opto-electronic properties of differentially substituted 1,4-
diethynyl- and 1,1,4,4-tetraethynylbuta-1,2,3-trienes. These novel chromophores greatly extend the series of
building modules for oxidative coupling, which includes 1,2-diethynyl- and 1,1,2,2-tetraethynylethenes and 1,3-
diethynylallenes (Fig. 1). A general synthesis of 1,1,4,4-tetraethynylbutatrienes, which tolerates a significant
number of peripheral substituents, starts from pentadiynols that are oxidized to the corresponding dialkynyl
ketones, followed by Corey ± Fuchs dibromo-olefination, and transition metal mediated dimerization
(Schemes 2 and 3). A similar protocol, including oxidation of propargyl aldehydes, dibromo-olefination, and
dimerization yields the less stable 1,4-diethynylbutatrienes (Scheme 4). Attempts to prepare 1,1,4,4-tetraeth-
ynylbutatrienes with four terminal electron-donor-substituted aryl groups failed so far, mainly due to difficulties
in the dibromoolefination step (Scheme 6). cis-trans-Isomerization of differentially substituted 1,1,4,4-
tetraethynylbutatrienes is remarkably facile, with barriers to rotation in the range of those for peptide bond
isomerization (DG=ꢀ 20 kcal molÀ1). Barriers to rotation of 1,4-diethynylbutatrienes are higher (DG=ꢀ 25 kcal
molÀ1), allowing in some cases the isolation of pure isomers. Both UV/VIS spectroscopy (Figs. 2 and 3) and
electrochemical studies (Table) demonstrate that the all-C-cores in diethynyl- and tetraethynylbutatrienes have
strong electron-acceptor properties that are greatly enhanced with respect to those of diethynyl- and
tetraethynylethenes with two C(sp)-atoms less. Substitution with peripheral electron donor groups leads to
efficient intramolecular charge-transfer interactions, as evidenced by intense, bathochromically shifted longest-
wavelength bands in the UV/VIS spectra.
1. Introduction. ± The synthesis and study of conjugated organic scaffolds as sources
of advanced materials for opto-electronic applications continue to attract large interest
in the chemical community [1 ± 3]. In this context, much effort has been directed
towards the preparation of small acetylenic building blocks as precursors for the
assembly ± via oxidative coupling ± of well-defined molecular architectures extending
into one, two, and three dimensions [4][5]. Starting from (E)-diethynylethenes (DEEs,
(E)-hex-3-ene-1,5-diynes) or tetraethynylethenes (TEEs, 3,4-diethynylhex-3-ene-1,5-
diynes; Fig. 1), monodisperse conjugated poly(triacetylene) oligomers measuring up to
18 nm in length [6] and organometallic rods featuring insulating PtII s-bis(acetylide)
connectors [7] were prepared. TEE Building blocks also provided access to
perethynylated dehydroannulenes [8][9], expanded radialenes [10], and radiaannu-
lenes [9][11]. These strongly electron-withdrawing, conjugated macrocycles display
ꢁ 2004 Verlag Helvetica Chimica Acta AG, Zürich

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Fig. 1. C-Rich building blocks for acetylenic scaffolding
intense intramolecular charge-transfer bands when substituted with N,N-dialkylanilino
donor groups at the periphery.
Extension of the central olefinic core in DEEs and TEEs leads to diethynyl- and
tetraethynylallenes (Fig. 1). While methods for the preparation of 1,3-diethynylallenes
by regioselective Pd0-catalyzed cross-coupling of substrates bearing bispropargylic
leaving groups with silyl-protected alkynes have recently been developed [12][13], the
corresponding tetraethynylallenes remain elusive [13][14]. Similarly, further expansion
of the central cumulenic fragment towards diethynyl- and tetraethynylbutatrienes
(Fig. 1) has only been investigated scarcely. Prior to this project, only the preparation of
two symmetrical 1,1,4,4-tetrakis[(trialkylsilyl)ethynyl]butatrienes had been reported
[15]. In contrast, alkyl- and aryl-substituted butatrienes have been investigated to a
greater extent (for a survey of butatriene synthesis, see [16]; for recent examples, see
[17]). Thus, tetraarylated butatrienes were cyclo-oligomerized into [4]- and [6]radi-
alenes [18][19], whereas dialkyl- or diaryl-substituted butatrienes were found to
polymerize under radical-free conditions to yield substituted poly(acetylene)s [20 ± 22].
On the other hand, developing an access to partially deprotected diethynyl- and
tetraethynylbutatrienes would subsequently allow the preparation, via oxidative
coupling, of a novel class of acetylenic molecular rods and macrocycles with potentially
unusual properties.
Here, we describe the synthesis of a series of 1,4-diethynyl- and 1,1,4,4-
tetraethynylbutatrienes by dimerization of appropriate dibromo olefins. Moreover,
we show that these compounds exhibit interesting opto-electronic properties as well as
an unexpectedly low barrier for cis-trans isomerization (for an experimental and
theoretical study concerning this isomerization process, see [23]).
2. Results and Discussion. ± 2.1. Synthesis of Tetraethynyl and Diethynylbutatrienes.
1,1-Dibromoethenes have previously been shown to dimerize to butatrienes when
reacted with appropriate transition metal complexes [24]. Consequently, di- and
tetraethynylated butatrienes should be obtained starting from the corresponding
alkynylated 1,1-dibromoethenes.

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For the preparation of 1,1,4,4-tetraalkynylbutatrienes, diethynylated 1 was synthe-
sized as described in [25] via addition of (i-Pr)3SiÀCꢁCH to Me3SiÀCꢁCÀCHO,
followed by oxidation of the resulting alcohol to the bispropargylic ketone with
pyridinium chlorochromate (PCC) and Corey ± Fuchs dibromo-olefination with CBr4/
Ph3P. Deprotection with K2CO3 in THF/MeOH furnished the mono-deprotected
alkyne that was directly subjected to Sonogashira cross-coupling [26] with various iodo-
arenes under standard conditions ([Pd(PPh3)2Cl2]/CuI/HN(i-Pr)2) to give 2a ± 2c
(Scheme 1). However, yields were disappointing except for electron-deficient iodo-
arenes such as 4-nitro-iodobenzene (2a: 84%). Attempts to improve the yields in the
coupling of electron-rich iodo-arenes by using other catalyst systems ([Pd2(dba)3]/
AsPh3 in Et3N or [Pd(MeCN)2Cl2]/CuI in EtN(i-Pr)2) failed. As the coupling to 2b and
2c proceeds very slowly, decomposition of mono-deprotected 1 in solution becomes a
competitive pathway.
Scheme 1. Sonogashira Cross-Coupling between Iodoarenes and Mono-Deprotected 1
a) K2CO3, THF/MeOH. b) [Pd(PPh3)2Cl2], CuI, (i-Pr)2NH, ArI (yields over both steps).
The synthesis of the gem-dibromo olefins 2b ± 2g was finally achieved by a less
direct but more efficient route. Addition of aryl-, ferrocenyl-, or alkyl-substituted
lithium acetylide to (i-Pr)3SiÀCꢁCÀCHO gave the pentadiynols 3b ± 3g in good
yields, and subsequent oxidation with MnO2 provided the corresponding ketones 4b ±
4g (Scheme 2). Two different sets of conditions were employed in the dibromo-
olefination step: compounds 2b ± 2d were obtained by reacting ketones 4b ± 4d with
CBr4 (1.3equiv.) and Ph P (2.6 equiv.) in benzene at room temperature, whereas the
3
presence of Zn was required for the preparation of 2e ± 2g (CBr4 (2 equiv.), Ph3P (2
equiv.), and Zn (2 equiv.) in CH2Cl2 at room temperature). Our problems encountered
with the dibromo-olefination of dialkynyl ketones resemble those already pointed out
by Tykwinsky and co-workers [27]. Nevertheless, the presented methodology allowed
the preparation of 2b ± 2g in moderate-to-good overall yields (19 ± 58% starting from
(i-Pr)3-protected propargyl aldehyde).
The gem-dibromo olefins 2b ± 2g were subsequently treated with 1 equiv. of BuLi at
À 1108 in Et2O, followed by addition of 1 equiv. of [CuI ´ PBu3] (prepared according to
[28]) at À 858 to deliver the corresponding highly colored tetraethynylbutatrienes 5b ±
5g (Scheme 3). Not unexpectedly, the dimerization of the electron-deficient NO2
derivative 2a did not proceed successfully, due to the enhanced instability of the
elusive butatriene 5a caused by the presence of two strongly electron-accepting entities

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Scheme 2. Synthesis of Dialkynylated 1,1-Dibromoethenes 2b ± 2g
a) BuLi, THF, À 108; then (i-Pr)3SiÀCꢁCÀCHO. b) MnO2, Et2O, 208. c) CBr4, Ph3P, benzene, 208. d) CBr4,
PPh3, Zn, CH2Cl2, 208. Fc ˆ ferrocenyl.
(the cumulenic core and the NO2C6H4 groups) in the molecule. In contrast, yields were
particularly high in the presence of electron-donating groups (e.g., 5c: 80%). On the
other hand, the yields of donor-substituted 5f and 5g were substantially lower due to
difficulties with purification, which required both regular column (SiO2) and gel-
permeation chromatography (Bio-Beads SX-1) to separate the desired butatrienes
from 2,2-dialkynylated 1-bromo alkenes formed as side products.
Scheme 3. Synthesis of 1,1,4,4-Tetraethynylbutatrienes
a) BuLi, Et2O, À 1108, then [CuI . PBu3], À 858 ! 208. The colors of solutions in CH2Cl2 are indicated.
In the dimerization of 2b ± 2g to 5b ± 5g, respectively, the high solubility of the Cu
complex employed [24] seems to be particularly beneficial, since it allows the reaction
to take place at very low temperature, thus preventing any decomposition of starting
material and product. Accordingly, protocols for similar dimerization processes at

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room temperature [29] did not lead to any isolable tetraethynylbutatrienes. All
butatrienes 5b ± 5g were obtained as inseparable mixtures of cis- and trans-isomers as
demonstrated by 1H- and 13C-NMR spectroscopy, with the characteristic central
cumulenic resonance appearing at ca. 150 ppm in the 13C-NMR spectra. The IR spectra
of these compounds displayed weak bands around 2200 and 1530 cmÀ1, corresponding
to CꢁC and CˆC bond stretches, respectively. The obtained tetraethynylbutatrienes
5c ± 5g are surprisingly stable and can be stored for prolonged time periods in the solid
state at À 308; only 5b decomposes with time, even at low temperatures.
To evidence the potential of the (i-Pr)3Si-protected tetraethynylbutatrienes as
building blocks for acetylenic scaffolding, deprotection of the anilino derivative 5c was
attempted in the presence of Bu4NF (2 equiv.) and 2-nitrophenol (2 equiv.) in THF at
08. Complete deprotection was observed by TLC after 2 h, and the solution seems
stable enough for performing subsequent in situ oxidative couplings. Decomposition,
however, occurs upon evaporation of the solvent.
1,4-Diethynylbutatrienes had not been described prior to this work. On the way to
these new building modules, the substituted propargylic alcohols 6a ± 6d were prepared
either by nucleophilic addition of the corresponding lithium acetylide to paraformal-
dehyde [30] or via Pd-catalyzed cross-coupling between propargyl alcohol and the
appropriate aryl iodide (Scheme 4) [31][32]. Subsequent oxidation afforded the
propargyl aldehydes 7a ± 7d in high yield [14][31][32]. In the case of the ferrocenyl
derivative 7e, a direct synthesis via lithiation of ethynylferrocene, followed by addition
of dimethylformamide (DMF), was very efficient giving rise to the formation of 7e in
90% yield. Dibromo-olefination (CBr4, Ph3P, and Zn in CH2Cl2 at room temperature)
afforded the gem-dibromo olefins 8a ± 8e.
Scheme 4. Synthesis of 1,4-Diethynylbutatrienes
a) BuLi, THF, À 108, then (HCHO)x. b) HCꢁCÀCH2OH, [Pd(PPh3)2Cl2], CuI, HN(i-Pr)2. c) BuLi, THF, À
788, then DMF, À 788 ! 208. d) CBr4, Ph3P, Zn, CH2Cl2, 208. e) BuLi, Et2O, À 1108, then [CuI ´ PBu3], À 858 !
208.
The subsequent dimerization was not successful in all cases. Whereas the reaction of
the (i-Pr3)Si, N,N-dimethylanilino, and ferrocenyl derivatives, 8a, 8b, and 8e,
respectively, provided the desired 1,4-diethynylbutatrienes 9a, 9b, and 9e, respectively,

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the synthesis of the 3,5-di(tert-butyl)phenyl and 4-methoxyphenyl derivatives, 9c and
9d, respectively, was not successful. This may reflect a higher instability of 1,4-
diethynylbutatrienes under the reaction conditions as compared to 1,1,4,4-tetraeth-
ynylbutatrienes. All three butatrienes were obtained as a mixture of cis- and trans-
isomers (NMR). While one isomer of 9a could be separated and isolated in pure form,
compounds 9b and 9e were obtained as inseparable isomeric mixtures. The 13C-NMR
resonances of the two central C(sp)-atoms in the cumulene fragment of 9b and 9e
appear at ca. 155 ppm, whereas this signal appears in the spectrum of 9a at 160.9 ppm.
2.2. cis-trans Isomerization. Based on the published data for butatrienes, [16][33],
we expected the isomerization barriers to be high enough to allow separation of cis- and
trans-1,1,4,4-tetraethynylbutatrienes 5b ± 5g at room temperature. However, all at-
tempts to separate the two isomers either by gravity or high-performance liquid
chromatography failed. A subsequent determination of the activation parameters for
the cis-trans isomerization process by 1H-NMR techniques revealed a remarkably low
rotational barrier DG= for 1,1,4,4-tetraethynylbutatrienes 5d and 5f of ca. 20 kcal molÀ1,
in the range of those observed for rotation about peptide bonds [23]. This facile
isomerization process explains the failure of all our attempts to separate the cis- and
trans-isomers.
In contrast, the isolation of a pure isomer was possible for 9a, showing that
1
isomerization is less facile in the case of 1,4-diethynylbutatrienes. H-NMR Inves-
tigations allowed estimation of the barrier for thermal cis-trans isomerization of 9a as
DG=ꢀ 25 kcal molÀ1 [23]. On the other hand, all attempts to separate the isomers of 9b
and 9e remained unsuccessful. Possibly, increased extension of conjugation through the
terminal aromatic rings further reduces the barrier for rotation in these cumulenes,
thereby rendering isomer separation impossible at room temperature (for elegant
investigations on the dependence of the barrier for cis-trans isomerization in olefins as a
function of conjugation length, see [34]).
Detailed computational studies by Houk, Jarowski, and co-workers [23] confirmed
the stabilizing effect of alkynyl substituents on the proposed but-2-yne-1,4-diyl singlet
diradical transition state of the cis-trans isomerization in 1,4-diethynyl- and 1,1,4,4-
tetraethynylbutatrienes and accurately reproduced the experimentally determined
rotational barriers.
2.3. RhI Coordination. Previous reports concerning the coordination of the central
double bond in [3]cumulenes to RhI under formation of stable h2-complexes [15][35 ±
37] prompted us to investigate this complexation mode for the new tetraethynylated
butatrienes 5c and 5d. Reaction with [Rh(PPh3)3Cl] in CH2Cl2 at room temperature
proceeded rapidly in the case of 5c, whereas the corresponding conversion of 5d was
very slow, presumably due to steric hindrance (Scheme 5).
The resulting h2-complexes 10c and 10d were obtained as mixtures of isomers.
However, their high instability towards SiO2 or Al2O3 precluded any chromatographic
purification. In the course of attempted purifications, it appeared that 5c and 5d only
acted as poor ligands for RhI, since they underwent smooth decomplexation during
column chromatography. Finally, the h2-complexes were separated from starting
material by gel-permeation chromatography (GPC), thereby furnishing 10c and 10d in
13and 72% yield, respectively. The anilino-substituted complex 10c was found to be
substantially less stable than 10d, and full characterization by NMR spectroscopy was

Helvetica Chimica Acta ± Vol. 87 (2004)
Scheme 5. Synthesis of h2-RhI Complexes
3091
a) [Rh(PPh3)3Cl], CH2Cl2, 208.
not possible due to rapid degradation in solution. Separation of the cis- and trans-
isomers of the h2-RhI complexes was also not possible due to the limited stability of
these species.
2.4. Electronic Absorption Spectroscopy. The UV/VIS spectra of tetraethynylbuta-
trienes 5b ± 5g (CH2Cl2; Fig. 2) revealed strong chromophoric properties. The spectra
of the aryl-substituted tetraethynylbutatrienes 5b, 5d, and 5e are very similar with an
end-absorption around 550 nm and a longest-wavelength absorption maximum lmax
Fig. 2. Electronic absorption spectra of 5b (brown), 5c (pink), 5d (orange), 5e (red), 5f (green), and 5g (blue)
in CH2Cl2

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around 480 nm (5b: lmax ˆ 469 nm, e ˆ 35700 molÀ1 l cmÀ1; 5d: lmax ˆ 481 nm, e ˆ
41600 molÀ1 l cmÀ1; 5e: lmax ˆ 494 nm, e ˆ 50400 molÀ1 l cmÀ1). When replacing the
aryl rings by alkyl groups (in 5g) the longest-wavelength band is hypsochromically
shifted to lmax ˆ 419 nm (e ˆ 29400 molÀ1 l cmÀ1).
Introduction of strongly electron-donating dialkylanilino groups in 5c led to an
intense longest-wavelength band at 573nm, which is bathochromically shifted by more
than 100 nm (0.48 eV) as compared to the phenyl derivative 5b. The reversible
quenching of this absorption band upon acidification with TsOH and subsequent
neutralization with Et3N identifies it as a charge-transfer resulting from intramolecular
charge-transfer interactions between the anilino donor group and the electron-
accepting cumulenic core. It is worth comparing the UV/VIS spectra of anilino-
substituted tetraethynylbutatriene 5c (lmax ˆ 573nm) and the corresponding tetra-
ethynylethene derivative (lmax ˆ 459 nm) [38]. Introduction of the two additional
C(sp)-atoms into the central core of 5b leads to a strong red-shift of the intramolecular
charge-transfer band (Dl ˆ 114 nm, DE ˆ 0.53eV), thus highlighting a strong increase
of the electron-acceptor potential of the C-core.
Introduction of ferrocenyl substituents (i.e., 5f) shifts the longest-wavelength band
lmax bathochromically to 602 nm, presumably due to the intramolecular charge-transfer
character of this transition. On the other hand, the molar extinction coefficient of this
band is remarkably reduced (e ˆ 3450 molÀ1 l cmÀ1), for which we do not have a good
explanation. The second absorption band at 452 nm (e ˆ 17800 molÀ1 l cmÀ1) may be
due to metal-to-ligand charge transfer.
The UV/VIS spectra (CH2Cl2) of the dialkynylated butatrienes 9a, 9b, and 9e are
depicted in Fig. 3. The reduction of the conjugated all-C-chromophore as compared to
the tetraalkynylated analogs is clearly evident from the position of the longest-
wavelength band, which appears at lmax ˆ 419 nm in the t-Bu-substituted tetraethynyl
derivative 5g and at lmax ˆ 356 nm in (i-Pr)3Si-substituted diethynylbutatriene 9a. The
Fig. 3. Electronic absorption spectra 9a (yellow), 9b (pink), and 9e (red) in CH2Cl2. Also shown are the spectra
of 9b after addition of TsOH (brown) and subsequent neutralization with Et3N (green).

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spectrum of ferrocenyl derivative 9e resembles the one of the tetraethynylated analog
5f (Fig. 2), featuring two absorption bands, with the longest-wavelength band ±
presumably with high charge-transfer character ± appearing at lmax ˆ 516 nm (e ˆ
140 molÀ1 l cmÀ1) as compared to lmax ˆ 602 nm in the spectrum of 5f.
The decrease in chromophoric extension and electron-acceptor strength upon
removal of two CꢁC bonds is also visible in the comparison between the two
dimethylanilino-substituted derivatives, diethynylated 9b (lmax ˆ 489 nm, e ˆ
5400 molÀ1 l cmÀ1) and tetraethynylated 5c (lmax ˆ 573nm, e ˆ 40500 molÀ1 l cmÀ1):
the longest-wavelength band of the diethynylated derivative features both a strong
hypsochromic shift and a large hypochromism. Addition of TsOH caused a color
change of the solution of 9b in CH2Cl2 from purple to yellow, reflecting the
disappearance of the intramolecular charge-transfer band in the UV/VIS spectrum
(Fig. 3). Again, the original spectrum of 9b was completely recovered upon subsequent
neutralization with Et3N, albeit with a slight reduction in absorption intensity
presumably due to a slight degradation of the compound upon acidification.
2.5. Electrochemistry. The electrochemical properties of tetraethynylbutatrienes
5c ± 5f were investigated by cyclic voltammetry (CV) and rotating-disk voltammetry
‡
(RDV). The redox potentials vs. Fc /Fc (ferricinium/ferrocene couple) are listed in the
Table.
Table. Cyclic Voltammetry (CV) and Rotating-Disk Voltammetry (RDV) Data in CH2Cl2 (‡ 0.1m Bu4NPF6).
‡
Potentials are given vs. Fc /Fc. Working electrode: glassy-C electrode; counter electrode: Pt; reference
electrode: Ag/AgCl electrode.
Cyclic voltammetrya)
Rotating-disk voltammetry
E8b) [V]
DEp c) [mV]
Epd) [V]
E1/2e) [V]
Slopef) [mV]
5c
5d
5e
5f
‡ 0.28g)
À 1.38
60
60
‡ 0.28
À 1.38
À 1.88
‡ 1.01
À 1.27
À 1.83100
‡ 0.84
À 1.33
80
70
120
80
À 1.82
‡ 1.03h)
À 1.28
80
60
75
À 1.78
‡ 0.84
125
80
À 1.34
À 1.80
‡ 0.18
À 1.41
120
80
0.22
À 1.41
90
95
À 1.91
a) Scan rate 0.1 V sÀ1
.
b) E8 ˆ (Epc ‡ Epa)/2, where Epc and Epa correspond to the cathodic and anodic peak
potentials, respectively. c) DEp is the peak potential difference at v ˆ 0.1 V sÀ1
.
d) Peak potential Ep for
irreversible electron transfer. e) Half-wave potential E1/2. f) Slope of the linearized plot of E vs. log [I/(Ilim À I)].
g) Unresolved two-electron oxidation. ) The electron transfer becomes reversible at scan higher than 5 V sÀ1
.
h
All tetraethynylbutatrienes exhibit two reduction steps; the first one is a reversible
one-electron transfer, whereas the second one is irreversible. These two reductions take
place at the conjugated backbone. Reductions in compounds 5c ± 5f occur at potentials
between À 1.28 and À 1.41 V for the first one, and À 1.78 to À 1.91 V for the second
one. These values are in good agreement with the reduction potentials measured for

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‡
tetrakis[tri(isopropylsilyl)ethynyl]butatriene (Ered ˆ À1.30 and À 1.84 V vs. Fc /Fc)
[39]. Comparatively, the one-electron reduction of the tetraethynylethene (TEE) core
in tetrakis(phenylethynyl)ethene occurs at a more negative potential around À 1.80 V
[40]. As expected, introduction of electron-donating groups shifts the first reduction
potential of tetraethynylbutatrienes cathodically from À 1.28 V for 5d to À 1.34 V for
5e, À 1.38 V for 5c, and À 1.41 V for 5f. This is consistent with a more-difficult
reduction for electron-richer molecules.
The conjugated backbone in 5d is oxidized irreversibly at 1.03V. However, for 5c
and 5e the first oxidation occurs at the anilino or methoxyphenyl substituents at 0.28
and 0.84 V, respectively, since these groups are electroactive [41]. Comparison with the
corresponding tetraethynylethenes is difficult, since data are scarce, nevertheless, the
oxidation of the anilino group in the tetraethynylethene analog of 5c was measured at
0.39 V [40]. As the first oxidation potential shifts anodically going from tetraeth-
ynylbutatriene to tetraethynylethene, the presence of the [3]cumulenic acceptor
fragment does not make the oxidation of the anilino group more difficult, which may
indicate that there is almost no communication between the anilino substituent and the
C(sp)-core fragment at the HOMO level. Moreover, the ferrocenyl derivative 5f gives a
single reversible two-electron transfer, the characteristics of which denote overlap of
the two reversible one-electron transfers. The peak potential difference is equal to
120 mVand remains constant for scan rates up to 1 V sÀ1. Analysis of the peaks allowed
the determination of the potential difference between the two ferrocene units at 80 mV,
the oxidation potentials being Eox1 ˆ ‡0.14 and Eox2 ˆ ‡0.22 V. It is worth comparing
the results obtained for 5f with those published for 1,4-diferrocenyl-1,4-diphenylbuta-
triene [17b]. In the latter system, two reversible steps occur at ‡ 0.41 and ‡ 0.61 V vs.
SCE (standard calomel electrode), and an irreversible one at ‡ 1.45 vs. SCE. As the
two ferrocenyl substituents are directly connected to the cumulenic core, potential
splitting is observed. In our case, the distance between the two ferrocenyl units is larger,
so that the electrostatic interactions between the two oxidized ferrocenyl units are
reduced. Under these conditions, there are less interactions through the conjugated
backbone, so that the two oxidation potentials are very close (‡0.14 and ‡ 0.22 V vs.
‡
Fc /Fc).
2.6. Synthetic Approaches towards Tetrakis(arylethynyl)butatrienes. Since the
central C-core of tetraethynylbutatrienes proved to have strong electron-acceptor
properties (Sect. 2.4), we became interested in the synthesis of derivatives bearing four
donor groups to further enhance the intramolecular charge-transfer interactions. For
this purpose, pentadiynols 11a ± 11c were prepared by nucleophilic addition of donor-
substituted acetylides to HCO2Et. Deprotonation of the alkyne was first performed
using BuLi at À 788, but after addition of the electrophile the expected alcohol was
formed together with the corresponding aldehyde resulting from mono-addition.
Chromatographic separation of the two products was tedious, since the aldehyde
proved to be sensitive to SiO2. Finally, we found that deprotonation of the alkyne using
EtMgBr in Et2O at 408 followed by addition of HCO2Et was a more efficient
procedure, delivering 11a (R ˆ 4-MeOÀC6H4), 11b (R ˆ 4-Me2NÀC6H4), and 11c
(R ˆ Fc) in 59, 45, and 49% yield, respectively (Scheme 6). Subsequent oxidation by
MnO2 proceeded smoothly, furnishing ketones 12a ± 12c. On the other hand, dibromo-
olefination of these ketones bearing two donor groups was difficult. The transformation

Helvetica Chimica Acta ± Vol. 87 (2004)
3095
Scheme 6. Synthetic Attempts towards Tetrakis(arylethynyl)butatrienes
a) EtMgBr, Et2O, 408, then HCO2Et. b) MnO2, Et2O, 208. c) CBr4, Ph3P, P hH or CH 2Cl2, 208. d) BuLi, Et2O,
À 1108, then [CuI ´ PBu3], À 858 ! 208.
of the 4-MeOÀC6H4 derivative 12a into dibromo olefin 13a proceeded in 52% yield,
under the conditions described above (Sect. 2.1). For ketones 12b and 12c, featuring the
stronger dimethylanilino and ferrocenyl donor groups, these reaction conditions were
not efficient: 13b was isolated in only 9% yield, while 13c was not formed at all. A
variety of reaction conditions were employed to prepare 13b in higher yield, including a
recent procedure that requires the formation of a hydrazone intermediate, [42], albeit
none of them were successful. The dimerization of dibromo olefin 13a was subsequently
attempted using the conditions described above (Sect. 2.1). Unfortunately, no
butatriene could be isolated; rather the forming product seems to become unstable
when warming the solution to room temperature. This lower stability of tetrakis(ar-
ylethynyl)butatrienes may be explained by the absence of steric protection of the
cumulenic core, which, in case of the tetraethynylbutatrienes 5b ± 5f, was provided by
the lateral (i-Pr)3Si groups. Further efforts towards the preparation and character-
ization of the targeted tetrakis(arylethynyl)butatrienes are underway.
3. Conclusions. ± With the differentially substituted 1,4-diethynylated and 1,1,4,4-
tetraethynylated butatrienes reported in this paper, the series of cumulenic building
blocks for acetylenic scaffolding, which hitherto included diethynyl- and tetraethyn-
ylethenes (DEEs and TEEs) and 1,3-diethynylallenes, has been substantially extended.
Their synthesis via transition-metal-mediated coupling of alkynylated gem-dibromo-
ethenes proves to be quite versatile, tolerating a large number of substituents on the
alkyne groups. On the other hand, the preparation of the gem-dibromo-ethenes via
Corey ± Fuchs dibromo-olefination has been found problematic at instances, in
agreement with other literature reports [27]. cis-trans Isomerization of differentially
substituted 1,1,4,4-tetraethynylbutatrienes via a singlet diradical transition state is
remarkably facile, and the rotational barrier was determined in 1H-NMR investigations
as DG=ꢀ 20 kcal molÀ1, similar to the barrier for rotation about a peptide bond [23].
The barriers for 1,4-diethynylbutatrienes are higher, around 25 kcal molÀ1, allowing, in
some cases, the isolation of pure isomers. UV/VIS Spectroscopy and electrochemical
studies demonstrate that the electron-accepting power of the central all-C-core is
greatly increased upon changing from tetraethynylethenes to tetraethynylbutatrienes.
Introduction of peripheral aryl donor groups such as N,N-dimethylanilino residues

3096
Helvetica Chimica Acta ± Vol. 87 (2004)
leads to compounds (e.g., 5c) featuring intense, bathochromically shifted intra-
molecular charge-transfer bands. Attempts to introduce four peripheral donor groups
into tetraethynylbutatrienes failed so far; these compounds will be the subject of
further investigations. Preliminary work shows that 1,1,4,4-tetraethynylbutatrienes with
two terminal free alkyne groups in positions 1 and 4 of the cumulenic core can be
prepared by removal of (i-Pr)3Si-protecting groups. The reasonable stability of the
deprotected derivatives in solution should allow, in future work, the construction by
oxidative coupling of novel linear oligomers and macrocycles with unprecedented all-
C-skeletons and unusual opto-electronic properties.
Dr. Carlo Thilgen is gratefully acknowledged for his help with the nomenclature. We thank the ETH
Research Council and the German Fonds der Chemischen Industrie for support of this work.
Experimental Part
General. All reactions were carried out under an inert atmosphere (Ar or N2) by applying a positive
pressure. Chemicals were purchased from commercial suppliers and used as received. Compounds 6a [30] , 6b
and 6d [31][32], and 7a, 7b, and 7d [14][31][32] were prepared according to literature protocols. THF was
freshly distilled from sodium benzophenone ketyl, and CH2Cl2 was freshly distilled from CaH2. Et2O on
molecular sieves from Fluka was used for dimerization reactions. Evaporation in vacuo was performed using a
membrane pump at a pressure of 20 ± 50 Torr. TLC: alumina sheets precoated with 0.25-mm Macherey ± Nagel
SiO2, with fluorescent indicator. Column chromatography (CC): SiO2 60 (particle size 0.04 ± 0.063mm, 230 ±
400 mesh) from Fluka and distilled technical solvents. Size-exclusion chromatography (GPC): Bio-Beads S-X3
and S-X1 from Bio-Rad using distilled technical solvents. M.p. in open capillaries with a Büchi 540 apparatus,
uncorrected; ꢂdec.ꢀ refers to decomposition. UV/VIS Spectra: Varian CARY 500 Scan spectrophotometer, lmax
in nm and e in molÀ1 l cmÀ1. IR Spectra: Perkin-Elmer FT1600 spectrometer; selected absorption bands in
wavenumbers (cmÀ1). 1H- (300 MHz) and 13C-NMR (75 MHz) spectra: Varian Gemini 300 spectrometers;
Chemical shifts are indicated in ppm downfield from Me4Si using the solvent peak as internal reference (CDCl3:
d(H) ˆ 7.25, d(C) ˆ 77.2); coupling constants J are indicated in Hz. MS: VG-Tribid instrument operating at
70 eV (EI-MS) or on an IonSpec Ultra instrument (MALDI-MS), with 2,5-dihydroxybenzoic acid (DHB) or 2-
{(E)-3-[(4-tert-butyl)phenyl]-2-methyl-2-propenylidene}malonitrile (DCTB) as a matrix. Elemental analyses
were performed by the Mikrolabor at the Laboratorium für Organische Chemie at ETH-Zürich.
Electrochemistry. Electrochemical measurements were carried out in CH2Cl2 containing 0.1m Bu4NPF6 in a
classical three-electrode cell by cyclic voltammetry (CV) and rotating-disk voltammetry (RDV). The working
electrode was a glassy-C disk (2 mm in diameter), the auxiliary electrode a Pt wire, and the reference electrode
‡
an aq. Ag/AgCl electrode. All potentials are given vs. Fc /Fc as internal reference.
3-(Dibromomethylidene)-1-(4-nitrophenyl)-5-(triisopropylsilyl)penta-1,4-diyne (2a). K2CO3 (0.276 g,
2 mmol) was added to a soln. of 1 (0.460 g, 1.0 mmol) in THF (10 ml) and MeOH (10 ml). After stirring for
30 min, CH2Cl2 (30 ml) was introduced, and the mixture was filtered through SiO2. Evaporation in vacuo left an
orange oil to which (i-Pr)2NH (15 ml) and 4-nitro-1-iodobenzene (0.249 mg, 1 mmol) were added. This soln. was
extensively purged with Ar for 1 h, after which [Pd(PPh3)2Cl2] (0.035 g, 0.05 mmol) and CuI (0.010 g,
0.05 mmol) were introduced. The mixture turned brown. After stirring for 1 h, CH2Cl2 was added and the
mixture filtered over SiO2. Evaporation in vacuo and CC (SiO2; hexane) afforded 2a (0.429 g, 84%). Yellow
solid. Rf (hexane/Ch2Cl2 7:3) 0.47. M.p. 88.08. IR (CCl4): 2944s, 2892m, 2866s, 1596s, 1525vs, 1491w, 1462m,
1344vs, 1166w, 1107w, 1010w, 997w, 922m, 883m, 868s, 855s, 803vs. 1H-NMR (300 MHz, CDCl3): 1.12 (m, 21 H);
7.64 (d, J ˆ 9, 2 H); 8.50 (d, J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3): 147.7; 132.6; 129.2; 123.9; 114.2; 111.1;
‡
‡
‡
101.6; 101.0; 93.2; 90.9; 18.8; 11.4. EI-MS: 511.0 (15, M ), 468.0 (100, [M À i-Pr] ). HR-EI-MS: 511.0051 (M ,
‡
‡
‡
C21H25Br2NO2Si ; calc. 511.0001); 467.9496 (100, [M À i-Pr] , C18H18Br2NO2Si ; calc. 467.9453). Anal. calc. for
C21H25NO2SiBr2 (511.33): C 49.33, H 4.93, N 2.74; found: C 49.44, H 5.05, N 2.90.
1-Phenyl-5-(triisopropylsilyl)penta-1,4-diyn-3-ol (3b). BuLi (1.5m in hexanes, 2 ml, 3mmol) was added to
ethynylbenzene (0.329 ml, 3 mmol) in freshly distilled THF (30 ml) at 08. After stirring for 1 h at this temp., 3-
(triisopropylsilyl)propynal (0.631 g, 3 mmol) was introduced. After stirring for 1 h, the reaction was quenched
by adding sat. aq. NH4Cl soln. (20 ml). The mixture was extracted twice with Et2O (30 ml), the combined org.
phases were washed with H2O and sat. aq. NH4Cl soln. (20 ml), and dried (MgSO4). Evaporation in vacuo and

Helvetica Chimica Acta ± Vol. 87 (2004)
3097
CC (SiO2; hexane/CH2Cl2 7:3then 1:1) afforded 3b (0.318 g, 66 %). Brown oil. Rf (hexane/CH2Cl2 1:1) 0.29.
IR (CCl4): 3601s, 2890w, 3470w (br.), 2944vs, 2892vs, 2866vs, 2235w, 2174w, 1670w, 1600w, 1490vs, 1463vs, 1443s,
1383m, 1367m, 1294m, 1231w, 1070m, 2030vs, 1017vs, 998vs, 915m, 903m, 883vs, 809vs. 1H-NMR (300 MHz,
CDCl3): 1.10 (m, 21 H); 2.23( d, J ˆ 8, 1 H); 5.34 (d, J ˆ 8, 1 H); 7.32 (m, 3H); 7.45 ( dd, J ˆ 8, 2, 2 H). 13C-NMR
‡
(75 MHz, CD3OD): 132.5; 129.6; 129.3; 123.5; 106.5; 87.8; 85.1; 84.0; 52.9; 18.9; 12.2. EI-MS : 312.3 (21, M ),
‡
‡
‡
295.1 (29, [M À OH] ), 267.2 (77, [M À OH À i-Pr] ), 253.2 (20, [M À OH À i-PrÀ Me] ), 239.1 (57, [M À i-PrÀ
‡
‡
‡
‡
2 Me] ), 225,1 (28, [M À 2i-Pr] ), 213.1 (91, [M À 2 i-PrÀ Me] ), 183.1 (71, [M À 3i-Pr] ), 169.1 (100, [M À
‡
‡
OH À 3i-Pr] ), 139.1 (64, [M À Si(i-Pr)3 À OH] ). Anal. calc. for C20H28OSi (312.53): C 76.86, H 9.03; found:
C 76.84, H 8.87.
1-[4-(Dimethylamino)phenyl]-5-(triisopropylsilyl)penta-1,4-diyn-3-ol (3c). 4-Ethynyl-N,N-dimethylaniline
(0.508 g, 3.5 mmol), BuLi (1.5m in hexanes, 2.33 ml, 3.5 mmol), and 3-(triisopropylsilyl)propynal (0.737 g,
3.5 mmol) were reacted according to the procedure described for 3b to give 3c (0.746 g, 60%) after flash
chromatography (FC; SiO2; hexane/CH2Cl2 1:2, then hexane/AcOEt: 4 :3). Yellow oil with properties identical
to those described in [43]. Rf (hexane/CH2Cl2 3:7) 0.29. 1H-NMR (300 MHz, CDCl3): 1.08 (m, 21 H); 2.20 (d,
J ˆ 7.5, 1 H); 2.98 (s, 6 H); 5.32 (d, J ˆ 7.5, 1 H); 6.62 (d, J ˆ 9, 2 H); 7.32 (d, J ˆ 9, 2 H).
1-[3,5-Di(tert-butyl)phenyl]-5-(triisopropylsilyl)penta-1,4-diyn-3-ol (3d). 3,5-Di(tert-butyl)phenylacet-
ylene (0.643g, 3mmol), BuLi (1.5 m in hexanes, 2.0 ml, 3 mmol), and 3-(triisopropylsilyl)propynal (0.632 g,
3mmol) were reacted according to the procedure described for 3b to give 3d (0.752 g, 59%) after CC (SiO2;
hexane/CH2Cl2 1:1). Brown oil. Rf (hexane/CH2Cl2 1 :1) 0.11. IR (CCl4): 3602m, 2965vs, 2866s, 2362w, 2336w,
2226w, 1590m, 1463m, 1364m, 1248m, 1055m, 1030s, 944w, 878m, 815vs. 1H-NMR (300 MHz, CDCl3): 1.10 (m,
21 H); 1.27 (s, 18 H); 2.22 (d, J ˆ 8, 1 H); 5.34 (d, J ˆ 8, 1 H); 7.31 (d, J ˆ 2, 2 H); 7.40 (t, J ˆ 2, 1 H). 13C-NMR
(75 MHz, CDCl3): 151.1; 126.3; 123.4; 121.3; 104.6; 86.3; 85.6; 85.3; 53.4; 35.0; 31.5; 18.0; 11.4. EI-MS: 424.4 (13,
‡
‡
‡
‡
M ), 381.2 (17, [M À i-Pr] ), 351.2 (20, [M À i-PrÀ 2 Me] ), 339.3 (15, [M À 2 i-Pr] ), 325.3 (100, [M À i-PrÀ t-
‡
‡
‡
Bu] ), 273.2 (24, [M À OH-(i-Pr)3Si] ), 211.2 (16, [M À CCC6H3(C4H9)2] ). Anal. calc. for C28H44OSi (424.74):
C 79.18, H 10.44; found: C 79.11, H 10.39.
1-(4-Methoxyphenyl)-5-(triisopropylsilyl)penta-1,4-diyn-3-ol (3e). (4-Methoxyphenyl)acetylene (0.632 g,
4.79 mmol), BuLi (1.3m in hexanes, 3.19 ml, 4.79 mmol), and 3-(triisopropylsilyl)propynal (1.051 g, 5 mmol)
were reacted according to the procedure described for 3b to give 3e (1.081 g, 66%) after CC (SiO2; hexane/
CH2Cl2 1:1). Brown oil. Rf (hexane/CH2Cl2 1:1) 0.26. IR (CCl4): 3588m, 3366w, 3008m, 2945vs, 2893s, 2866vs,
2253w, 2231m, 2174w, 1607s, 1572w, 1510vs, 1464s, 1442m, 1383m, 1368m, 1368m, 1290s, 1250vs, 1221vs, 1181m,
1
1173s, 1107w, 1034vs, 913s, 904.3s, 883s, 884s, 801w. H-NMR (300 MHz, CDCl3): 1.10 (s, 21 H); 2.20 (d, J ˆ 8,
1 H); 3.81 (s, 3 H); 5.32 (d, J ˆ 8, 1 H); 6.84 (d, J ˆ 9, 2 H); 7.38 (d, J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3):
‡
160.1; 135.6; 114.5; 114.2; 104.8; 86.0; 85.4; 84.3; 55.5; 53.3; 18.8; 11.4. EI-MS: 342.1 (12, M ), 297.0 (12, [M À
‡
‡
‡
H À i-Pr] ), 283.1 (32, [M À H À i-PrÀ Me] ), 269.1 (19, [M À H À i-PrÀ 2 Me] ), 255.1 (27, [M À H À 2 i-
‡
‡
‡
‡
Pr] ), 241.0 (41, [M À H À 2 i-PrÀ Me] ), 225.1 (40, [M À 2 i-PrÀ 2 Me] ), 213.1 (54, [M À 2 i-Pr] ), 169.1 (100,
‡
[M À OH À (i-Pr)3Si] ). Anal. calc. for C21H30O2Si (342.55): C 73.63, H 8.83; found: C 73.69, H 8.83.
1-Ferrocenyl-5-(triisopropylsilyl)penta-1,4-diyn-3-ol (3f). Ethynylferrocene (0.840 g, 4.00 mmol), BuLi
(1.5m in hexanes, 2.80 ml, 4.12 mmol), and 3-(triisopropylsilyl)propynal (1.11 g, 4.12 mmol) were reacted
according to the procedure described for 3b to give 3f (1.109 g, 66%) after CC (SiO2; hexane/CH2Cl2 1 :1).
Brown oil. Rf (hexane/CH2Cl2 1:1) 0.18. IR (CHCl3): 3588m, 3155m, 2945vs, 2892m, 2866vs, 2253vs, 2233s,
1817w, 1793m, 1645w, 1463s, 1382s, 1295m, 1106s, 1098s, 1066w, 1026s, 1006vs, 903vs, 825w. 1H-NMR (300 MHz,
CDCl3): 1.11 (s, 21 H); 2.25 (d, J ˆ 6, 1 H); 4.19 (t, J ˆ 2, 2 H); 4.21 (s, 4 H), 4.19 (m, 2 H); 5.3 2 (d, J ˆ 6, 1 H);
5.24 (d, J ˆ 6, 1 H). 13C-NMR (75 MHz, CDCl3): 104.4; 87.7; 83.3; 82.7; 71.7; 71.5; 70.0; 68.9; 53.3; 18.7; 11.3.
‡
‡
‡
MALDI-MS (DHB): 420.16 (100, M ), 403.15 (17, [M À OH] ). HR-MALDI-MS: 420.1572 (100, M ,
‡
C24H32FeOSi ; calc. 420.1572). Anal. calc. for C24H32FeOSi (420.45): C 68.56, H 7.67; found: C 68.32, H 7.72.
2,2-Dimethyl-7-(triisopropylsilyl)hepta-3,6-diyn-5-ol (3g). 3,3-Dimethylbut-1-yne (0.616 ml, 5.0 mmol),
BuLi (1.5m in hexanes, 3.74 ml, 5.5 mmol), and 3-(triisopropylsilyl)propynal (1.157 g, 5.5 mmol) were reacted
according to the procedure described for 3b to give 3g (1.081 g, 74%) after CC (SiO2; hexane/CH2Cl2 7:3).
Brown oil. Rf (hexane/CH2Cl2 7 :3) 0.11. IR (CHCl3): 3591vs, 3384w (br.), 3156w, 2967vs, 2864vs, 2717w, 2726w,
2253vs, 2175m, 1794w, 1463vs, 1383s, 1364vs, 1293s, 1263s, 1215m, 1217s, 10121s, 1219s, 1207vs, 1074s, 1024vs,
997s, 909vs, 884vs, 83 2m. 1H-NMR (300 MHz, CDCl3): 1.11 (s, 21 H); 1.21 (s, 9 H); 2.05 (d, J ˆ 7.5, 1 H); 5.07 (d,
J ˆ 7.5, 1 H). 13C-NMR (75 MHz, CDCl3): 105.4; 93.3; 85.3; 76.7; 52.9; 30.8; 27.5; 18.7; 11.4. MALDI-MS
‡
‡
‡
(DHB): 275.2 ([M À OH] ). HR-MALDI-MS: 275.2139 ([M À OH] , C18H31Si ; calc. 275.2195).
1-Phenyl-5-(triisopropylsilyl)penta-1,4-diyn-3-one (4b). MnO2 (0.416 g, 4.84 mmol) was added to 3b
(0.432 g, 1.38 mmol) in Et2O (20 ml), and the soln. was stirred for 12 h. CH2Cl2 was added, and the mixture was
filtered through a plug (SiO2) to afford 4b (0.407 g, 95%). Orange oil. Rf (hexane/CH2Cl2 1:1) 0.43. IR (CCl4):

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Helvetica Chimica Acta ± Vol. 87 (2004)
2946vs, 2893s, 2867vs, 2208vs, 2175m, 2142s, 1630vs, 1598m, 1490s, 1463s, 1444m, 1385w, 1368w, 1293m, 1278vs,
1237w, 1179w, 1124vs, 1070m, 1026w, 1019m, 999s, 920m, 876s, 805s. 1H-NMR (300 MHz, CDCl3): 1.15 (m,
21 H); 7.40 (dd, J ˆ 7.5, 7, 2 H); 7.47 (tt, J ˆ 7.5, 1.5, 1 H); 7.47 (dd, J ˆ 7, 1.5, 2 H). 13C-NMR (75 MHz, CDCl3):
‡
‡
160.4; 133.5; 131.5; 128.9; 119.7; 105.4; 97.6; 91.7; 89.7; 18.7; 11.3. EI-MS: 310.3 (11, M ), 267.2 (90, [M À i-Pr] ),
‡
‡
‡
239.1 (63, [M À i-PrÀ Me] ), 223.0 (16, [M À 2 i-Pr] ), 211.1 (71, [M À 2 i-PrÀ Me] ), 195,1 (51, [M À 2 i-PrÀ 2
‡
‡
‡
‡
Me] ), 183.1 (100, [M À 3i-Pr] ), 169.0 (77, [M À C10H5O] ), 129.1 (37, [M À CꢁCSi(i-Pr)3] ). Anal. calc. for
C20H26OSi (310.51): C 77.36, H 8.44; found: C 77.49, H 8.51.
1-[4-(Dimethylamino)phenyl]-5-(triisopropylsilyl)penta-1,4-diyn-3-one (4c). Alcohol 3c (1.85 g, 5.2 mmol)
was oxidized with MnO2 (1.57 g, 18.2 mmol) according to the procedure described for 4b to give 4c (1.79 g,
97%), exhibiting properties similar to those described in [43]. Yellow oil. Rf (CH2Cl2) 0.57. 1H-NMR (300 MHz,
CDCl3): 1.12 (m, 21 H); 3.00 (s, 6 H); 6.63( d, J ˆ 9, 2 H); 7.47 (d, J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3): 160.5;
152.2; 135.8; 111.8; 104.9; 97.2; 95.9; 94.9; 91.8; 40.2; 18.6; 11.3.
1-[3,5-Di(tert-butyl)phenyl]-5-(triisopropylsilyl)penta-1,4-diyn-3-one (4d). Alcohol 3d (0.734 g,
1.73mmol) was oxidized with MnO 2 (0.521 g, 6.06 mmol) according to the procedure described for 4b to give
4d (0.697 g, 95%). Red oil. Rf (hexane/CH2Cl2 1:1) 0.45. IR (CCl4): 3020s, 2967vs, 2905s, 2868vs, 2728w, 2253m,
2210vs, 2184vs, 2149s, 2728w, 2253m, 2210vs, 2184vs, 2149s, 1620vs, 1590s, 1463vs, 1426s, 1395m, 1385m, 1365s,
1248vs, 1142vs, 1127vs, 1072m, 1019m, 998s, 958s, 909vs, 882vs, 83 0s. 1H-NMR (300 MHz, CDCl3): 1.16 (m,
21 H), 1.33 (s, 18 H); 7.45 (d, J ˆ 1.5, 2 H), 7.55 (t, J ˆ 1.5, 1 H). 13C-NMR (75 MHz, CDCl3): 160.7; 151.6; 128.0;
‡
‡
126.1; 118.8; 105.6; 97.6; 93.8; 89.3; 35.1; 31.4; 18.7; 11.3. EI-MS: 422.4 (14, M ), 379.4 (30, [M À i-Pr] ), 351.3
‡
‡
‡
‡
(100, [M À i-PrÀ 2 Me] ), 323.3 (82, [M À 2 i-PrÀ O] ), 309.3 (87, M À 2 t-Bu] ), 295.2 (73, [M À 3i-Pr] ),
‡
281.2 (44, [M À 2 t-Bu À 2 Me] ). Anal. calc. for C28H42OSi (422.72): C 79.56, H 10.01; found: C 79.49, H 10.15.
1-(4-Methoxyphenyl)-5-(triisopropylsilyl)penta-1,4-diyn-3-one (4e). Alcohol 3e (0.902 g, 2.59 mmol) was
oxidized with MnO2 (1.11 g, 12.95 mmol) according to the procedure described for 4b to give 4e (0.751 g, 85%).
Orange oil. Rf (hexane/CH2Cl2 1:1) 0.44. IR (CCl4): 3200w, 3032w, 3009m, 2946vs, 2893s, 2867vs, 2842s, 2728w,
2591w, 2558w, 2253m, 2203vs, 2164vs, 2147vs, 2051w, 1605vs, 1597vs, 1569s, 1509vs, 1463vs, 1442s, 1385m, 1368m,
1305vs, 1287vs, 1254vs, 1226s, 1218vs, 1215s, 1210vs, 1207vs, 1182s, 1175s, 1126vs, 1030vs, 998s, 907vs, 883vs, 835vs.
1H-NMR (300 MHz, CDCl3): 1.10 (m, 21 H); 3.80 (s, 3H); 6.86 ( d, J ˆ 9, 2 H); 7.56 (d, J ˆ 9, 2 H). 13C-NMR
‡
(75 MHz, CDCl3): 162.4; 160.4; 135.7; 114.7; 111.3; 105.5; 96.9; 93.3; 90.1; 55.6; 18.7; 11.3. EI-MS: 340.2 (5, M ),
‡
‡
‡
297.1 (59, [M À i-Pr] ), 269.1 (100, [M À i-PrÀ Me À CH] ), 253.1 (12, [M À 2 i-Pr] ), 241.1 (77, [M À 2 i-PrÀ
‡
‡
‡
Me] ), 213.1 (71, [M À 3i-Pr] ), 159.1 (38, [M À CꢁCSi(i-Pr)3] ). Anal. calc. for C21H28O2Si (340.54): C 74.07,
H 8.29; found: C 73.93, H 8.29.
1-Ferrocenyl-5-(triisopropylsilyl)penta-1,4-diyn-3-one (4f). Alcohol 3f (1.04 g, 2.47 mmol) was oxidized
with MnO2 (1.25 g, 14.82 mmol) according to the procedure described for 4b to give 4f (0.887 g, 85%). Red oil.
Rf (hexane/CH2Cl2 1:1) 0.44. IR (CHCl3): 3101w, 2946vs, 2893s, 2867vs, 2219s, 2181vs, 2149s, 1608vs, 1462s,
1413w, 1385w, 1368w, 1287vs, 1147vs, 1107m, 1072w, 1037vs, 1019w, 998m, 93 2m, 883s, 8839s, 827s. 1H-NMR
(300 MHz, CDCl3): 1.15 (m, 21 H); 4.28 (s, 5 H); 4.43( d, J ˆ 2, 2 H); 4.62 (d, J ˆ 2, 2 H). 13C-NMR (75 MHz,
‡
CDCl3): 160.0; 105.4; 96.3; 96.2; 88.6; 73.3; 71.3; 70.6; 59.4; 18.6; 11.2. MALDI-MS (DHB): 418.14 (100, M ).
‡
‡
HR-MALDI-MS: 418.1421 (100, M , C24H30FeOSi ; calc. 418.1415).
2,2-Dimethyl-7-(triisopropylsilyl)hepta-3,6-diyn-5-one (4g). Alcohol 3g (1.07 g, 3.70 mmol) was oxidized
with MnO2 (1.84 g, 21.19 mmol) according to the procedure described for 4b to give 4g (1.056 g, 98%). Yellow
oil. Rf (hexane/CH2Cl2 7:3) 0.52. IR (CHCl3): 3155m, 2947s, 2867s, 2253vs, 2229m, 2191m, 2156w, 1817m, 1793m,
1
1626s, 1463s, 1382s, 1271m, 1175m, 1097m, 991m, 903vs. H-NMR (300 MHz, CDCl3): 1.11 (m, 21 H); 1.29 (s,
9 H). 13C NMR (75 MHz, CDCl3): 161.1; 105.5; 103.0; 96.6; 81.3; 30.0; 29.1; 18.6; 11.3. MALDI-MS (DHB):
‡
‡
‡
313.1 ([M ‡ Na] ). HR-MALDI-MS: 313.1958 ([M ‡ Na] , C18H30NaOSi : calc. 313.1964).
3-(Dibromomethylidene)-1-phenyl-5-(triisopropylsilyl)penta-1,4-diyne (2b). CBr4 (0.542 g, 1.64 mmol) and
Ph3P (0.860 g, 3.28 mmol) were added to a soln. of 4b (0.391 g, 1.26 mmol) in benzene (40 ml). After stirring for
3 d at 208, hexane (200 ml) was added, and the suspension was filtered through a plug (SiO2; hexane).
Evaporation in vacuo and CC (SiO2; hexane) afforded 2b (0.223g, 38%). Brown oil. Rf (hexane) 0.51. IR
1
(CCl4): 2944m, 2866m, 2203w, 2151w, 1488w, 1462w, 1317w, 1164w, 1119w, 1070w, 921m, 883m, 865s. H-NMR
(300 MHz, CDCl3): 1.12 (m, 21 H); 7.3 6 (m, 3 H); 7.50 (dd, J ˆ 2, 7.5, 2 H). 13C-NMR (75 MHz, CDCl3): 131.9;
‡
129.4; 128.6; 122.5; 114.8; 108.7; 102.2; 99.9; 95.8; 86.4; 18.9; 11.4. EI-MS: 466.1 (19, M ), 423.0 (58, [M À i-
‡
‡
‡
‡
Pr] ), 395.0 (16, [M À i-PrÀ 2 Me] ), 381.0 (6, [M À 2 i-Pr] ), 368.9 (10, [M À 2 i-PrÀ Me] ), 202.9 (37, [M À
‡
‡
BrÀ CꢁCSi(i-Pr)3] ), 177.1 (100, [M À 2 BrÀ 3i-Pr] ). Anal. calc. for C21H26Br2Si (466.33): C 54.09, H 5.62;
found: C 53.89, H 5.86.
3-(Dibromomethylidene)-1-[4-(dimethylamino)phenyl]-5-(triisopropylsilyl)penta-1,4-diyne (2c). CBr4
(0.430 g, 1.3 mmol) and Ph3P (0.683g, 2.60 mmol) were reacted with 4c (0.353 g, 1.00 mmol) as described for

Helvetica Chimica Acta ± Vol. 87 (2004)
3099
2b to deliver 2c (0.248, 49%) after CC (SiO2; hexane/CH2Cl2 1:1). Brown solid. Rf (hexane/CH2Cl2 7:3) 0.40.
M.p. 55.58. IR (CCl4): 2958m, 2866m, 2197w, 1608s, 1525w, 1361w, 1156w, 908w, 883w, 864w. 1H-NMR (300 MHz,
CDCl3): 1.12 (m, 21 H); 2.99 (s, 6 H); 6.62 (d, J ˆ 9, 2 H); 7.38 (d, J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3): 150.8;
‡
133.1; 115.2; 111.9; 108.9; 106.2; 102.7; 99.01; 97.9; 85.2; 40.4; 18.9; 11.4. EI-MS: 509.0 (100, M ), 464.0 (2, [M À
‡
‡
‡
‡
i-Pr] ), 429.1 (4, [M À Br] ), 387.1 (62, [M À C6H4N(CH3)2] ), 359.0 (21, [M À C6H4N(CH3)2) À 2 Me] ). Anal.
calc. for C23H31Br2NSi (507.06): C 54.86, H 6.71, N 2.67; found: C 54.95, H 6.62, N 2.58.
3-(Dibromomethylidene)-1-[3,5-di(tert-butyl)phenyl]-5-(triisopropylsilyl)penta-1,4-diyne (2d). CBr4
(0.562 g, 2.15 mmol) and Ph3P (1.42 g, 4.29 mmol) were reacted with 4d (0.697 g, 1.65 mmol) as described for
2b to give 2d (0.534 g, 56%). Brown solid. Rf (hexane/CH2Cl2 7 :3) 0.71. M.p. 73.58. IR (CCl4): 2964vs, 2866vs,
2336w, 2205m, 1589s, 1463s, 1427w, 1384w, 1364m, 1332w, 1264w, 1248m, 1216s, 1171m, 1072w, 1019w, 997m,
977m, 920w, 899w, 878vs, 811vs. 1H-NMR (300 MHz, CDCl3): 1.15 (m, 21 H); 1.3 3 s(, 18 H); 7.3 5 (d, J ˆ 2, 2 H);
7.45 (t, J ˆ 2, 1 H). 13C-NMR (75 MHz, CDCl3): 151.2; 126.1; 124.0; 121.5; 115.0; 108.1; 102.5; 99.7; 97.2; 85.3;
‡
‡
‡
35.0; 31.5; 18.9; 11.4. EI-MS: 576.2 (4, M ), 535.2 (100, [M À i-Pr] ), 507.3(2, [ M À i-PrÀ 2 Me] ), 479.1 (10,
‡
‡
[M À 2 t-Bu] ), 304.4 (4, [M À 2 t-Bu À (i-Pr)3Si] ). Anal. calc. for C29H42Br2Si (578.54): C 60.21, H 7.32; found:
C 60.19, H 7.14.
3-(Dibromomethylidene)-1-(4-methoxyphenyl)-5-(triisopropylsilyl)penta-1,4-diyne (2e). CBr4 (1.46 g,
4.4 mmol), Ph3P (1.16 g, 4.4 mmol), and Zn (0.288 g, 4.4 mmol) were suspended in CH2Cl2 (5 ml). The soln.
was stirred for 45 min at 208, then ketone 4d (0.717 g, 2.1 mmol) was added. After stirring for 12 h at 208, hexane
(50 ml) was added, and the suspension was filtered, the precipitate obtained was dissolved in CH2Cl2 and re-
precipitated with hexane. The combined filtrates were concentrated in vacuo, and the resulting oil was purified
by CC (SiO2; hexane/CH2Cl2 7 :3) to afford 2e (0.858 g, 83%). Clear yellow oil. Rf (hexane/CH2Cl2 7 :3) 0.44. IR
(CHCl3): 3020m, 3011m, 2945vs, 2892m, 2866vs, 2841m, 2249w, 2200m, 2151w, 1606vs, 1573w, 1515s, 1505s, 1465s,
1442m, 1384w, 1304m, 1290s, 1226s, 1221vs, 1216s, 1212m, 1208vs, 1206m, 1203w, 1191m, 1108w, 1072w, 1032s,
997m, 923s, 883s, 865vs, 834vs. 1H-NMR (300 MHz, CDCl3): 1.12 (s, 21 H); 3.82 (s, 3H); 6.86 ( d, J ˆ 9, 2 H); 7.44
(d, J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3): 160.2; 133.1; 114.7; 114.2; 114.0; 107.4; 102.2; 99.3; 96.0; 85.2; 55.3;
‡
‡
‡
18.8; 11.3. EI-MS: 496.0 (22, M ), 452.9 (64, [M À i-Pr] ), 424.9 (30, [M À i-PrÀ 2 Me] ), 412.9 (19, [M À 2 i-
‡
‡
‡
Pr] ), 316.0 (21, [M À CꢁCSi(i-Pr)3] ), 207.2 (100, [M À CꢁCSi(i-Pr)3 À C6H4(OMe)] ). Anal. calc. for
C22H28Br2OSi (496.36): C 53.24, H 5.69; found: C 53.41, H 5.89.
3-(Dibromomethylidene)-1-ferrocenyl-5-(triisopropylsilyl)penta-1,4-diyne (2f). CBr4 (1.38 g, 4.17 mmol),
Ph3P (1.09 g, 4.17 mmol), Zn (0.273g, 4.17 mmol), and 4f (0.871 g, 2.08 mmol) were reacted according to the
procedure described for 2e to afford 2f (0.415 g, 35%) after CC (SiO2; hexane/CH2Cl2 1:1). Brown oil. Rf
(hexane/CH2Cl2 1:1) 0.73. IR (CHCl3): 3690m, 3023s, 3018s, 3016s, 2944m, 2866m, 2337w, 2207m, 1463w, 1226w,
1224s, 1219s, 1215m, 1210s, 1207vs, 1203w, 1186w, 998w, 947w, 882m, 825w. 1H-NMR (300 MHz, CDCl3): 1.12 (s,
21 H); 4.24 (s, 5 H); 4.27 (d, J ˆ 2, 2 H); 4.50 (d, J ˆ 2, 2 H). 13C-NMR (75 MHz, CDCl3): 114.9; 106.8; 102.4;
‡
99.0; 95.9; 82.5; 71.7; 70.2; 69.4; 63.6; 18.8; 11.3. MALDI-MS (DHB): 574.0 (100, M ). HR-MALDI-MS:
‡
‡
573.9803 (100, M , C25H30Br2FeSi ; calc. 573.9812).
5-(Dibromomethylidene)-2,2-dimethyl-7-(triisopropylsilyl)hepta-3,6-diyne (2g). CBr4 (3.00 g, 9.06 mmol),
Ph3P (2.38 g, 9.06 mmol), Zn (0.592 g, 9.06 mmol) and 4f (1.31 g, 4.53 mmol) were reacted according to the
procedure described for 2e to give 2g (1.710 g, 85%) after CC (SiO2; hexane) Yellow oil. Rf (hexane) 0.69. IR
(CDCl3): 3020s, 2945m, 2866m, 1642w, 1364w, 1295w, 871m, 822w. 1H-NMR (300 MHz, CDCl3): 1.10 (s, 21 H);
1.27 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 115.0; 107.1; 105.8; 102.9; 98.8; 76.8; 30.6; 28.6; 18.8; 11.4. EI-MS:
‡
‡
‡
‡
446.05 (27, M ), 403.0 (100, [M À i-Pr] ). HR-EI-MS: 446.0473(26, M , C19H30Br2Si ; calc. 446.0463) 402.9964
‡
‡
([M À i-Pr] , C16H23Br2Si ; calc. 402.9915).
1,8-Diphenyl-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne (5b). BuLi (1.5m in hexanes,
0.50 ml, 0.76 mmol) was added to 2b (0.353 g, 0.76 mmol) in Et2O (6 ml) at À 1108. The mixture was stirred
for 1 h at À 1008, then a soln. of [CuI ´ PBu3] (0.299 g, 0.76 mol) in Et2O (6 ml) was introduced. The resulting red
soln. was stirred for 1 h at À 858, after which it was allowed to warm to 208 within 5 h. After stirring for 12 h at
208, the soln. was filtered through SiO2. Evaporation in vacuo afforded a red solid, which was purified by CC
(SiO2: hexane) to give 5b (0.145 g, 62%). Brown solid, mixture of cis- and trans-isomers (slowly equilibrating on
the NMR time scale) in a 43:57 ratio ( 1H-NMR, without configurational assignment). Rf (hexane) 0.09. M.p.
908 (dec.). UV/VIS (CH2Cl2): 469 (35700), 450 (sh, 30300), 427 (sh, 22100). IR (CCl4): 2957m, 2944s, 2892m,
2866s, 2184w, 1489w, 1463m, 1384w, 1318w, 1233w, 1187w, 1148w, 1069w, 1019w, 996w, 908m, 883m, 814vs.
1H-NMR (300 MHz, CDCl3): major isomer: 1.13( m, 42 H); 7.3 4 (m, 6 H); 7.52 (dd, J ˆ 7.5, 2, 4 H); minor
isomer: 1.13( m, 42 H); 7.3 4 (m, 6 H); 7.48 (dd, J ˆ 7.5, 2, 4 H). 13C-NMR (75 MHz, CDCl3): 149.5, 149.3; 132.1,
132.0; 129.4; 128.6; 122.5; 104.3; 100.7, 100.4; 96.8, 96.7; 88.9, 88.8; 87.7; 18.8; 11.5.

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Helvetica Chimica Acta ± Vol. 87 (2004)
1,8-Bis[4-(dimethylamino)phenyl]-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne (5c). BuLi
(1.5m in hexanes, 0.8 ml, 1.2 mmol), 2c (0.608 g, 1.2 mmol), and [CuI ´ PBu3] (0.471 g, 1.2 mmol) were reacted as
described for 5b to give 5c (0.279 g, 80%) after CC (SiO2; hexane/CH2Cl2 7:3). Purple solid, mixture of slowly
equilibrating cis- and trans-isomers in a 44 :56 ratio (1H-NMR, without configurational assignment). Rf (hexane/
CH2Cl2 7:3) 0.13. M.p. 103± 1048. UV/VIS (CH2Cl2): 573(40500), 503(sh, 20100), 489 (17500), 409 (12600). IR
(CCl4): 2959m, 2943m, 2892w, 2865m, 2174m, 2129w, 2001w, 1605s, 1538m, 1531m, 1463w, 1445w, 1362m, 1331w,
1196w, 1182w, 1143w, 1112w, 1071w, 947w, 897w, 883w, 801vs. 1H-NMR (300 MHz, CDCl3): major isomer: 1.13
(m, 42 H); 3.00 (s, 12 H); 6.61 (d, J ˆ 9, 4 H); 7.33 (d, J ˆ 9, 4 H); minor isomer: 1.13( m, 42 H); 3.00 (s, 12 H);
6.63( d, J ˆ 9, 4 H); 7.38 (d, J ˆ 9, 4 H). 13C-NMR (75 MHz, CDCl3): 155.9; 150.8; 146.6, 146.4; 133.6, 133.5;
111.9; 109.3; 105.1, 105.0; 99.3, 99.2; 98.8, 98.4; 89.0, 88.9; 86.5; 40.3; 18.9; 11.6. MALDI-MS (DCTB): 698 (100,
‡
‡‡
‡
‡
M ), 349 (6, M ). HR-MALDI-MS: 698.4439 (M , C46H62N2Si2 ; calc. 698.4452).
1,8-Bis[3,5-di(tert-butyl)phenyl]-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne (5d). BuLi
(1.5m in hexanes, 0.53ml, 0.8 mmol), 2d (0.461 g, 0.8 mmol), and [CuI ´ PBu3] (0.314 g, 0.8 mmol) were reacted
as described for 5b to give 5d (0.235 g, 69%) after CC (SiO2; hexane/CH2Cl2 9 :1). Orange solid; mixture of
slowly equilibrating cis- and trans-isomers in a 39 :61 ratio (1H-NMR, without configurational assignment). Rf
(hexane) 0.16. M.p. 1228 (dec.). UV/VIS (CH2Cl2): 481 (41600), 456 (sh, 35500), 443 (sh, 30600). IR (CCl4):
2964vs, 2866s, 2187m, 1866s, 1589m, 1539w, 1463m, 1427w, 1394w, 1364m, 1248w, 1184w, 1158w, 904w, 878m,
833w, 812vs. 1H-NMR (300 MHz, CDCl3): major isomer: 1.15 (m, 42 H); 1.3 3 s(, 3 6 H); 7.3 8d(, J ˆ 2, 4 H); 7.43
(t, J ˆ 2, 2 H); minor isomer: 1.16 (m, 42 H); 1.3 3 s(, 3 6 H); 7.3 4d(, J ˆ 2, 4 H); 7.43( t, J ˆ 2, 2 H). 13C-NMR
(75 MHz, CDCl3): 151.2, 151.0; 149.1, 149.0; 126.5, 126.4; 124.0; 121.6, 121.5; 104.8, 104.7; 100.4, 100.0; 98.4, 98.2;
‡
‡
88.0; 87.6; 35.0; 31.5; 18.8, 18.7; 11.7, 11.6. MALDI-MS (DCTB): 837 (100, M ), 794 (20, [M À i-Pr] ). HR-
‡
‡
MALDI: 836.6117 (M , C58H84Si2 ; calc. 836.6112).
1,8-Bis(4-methoxyphenyl)-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne (5e). BuLi (1.5m in
hexanes, 0.667 ml, 1 mmol), 2e (0.494 g, 1 mmol), and [CuI ´ PBu3] (0.393 g, 1 mol) were reacted as described
for 5b to give 5e (0.188 g, 56%) after CC (SiO2; hexane/CH2Cl2 8 :2). Red solid, mixture of slowly equilibrating
cis- and trans-isomers in a 41:59 ratio (1H-NMR, without configurational assignment). Rf (hexane/CH2Cl2 8 :2)
0.20. M.p. 1008. UV/VIS (CH2Cl2): 494 (50600), 459 (sh, 31000), 381 (10600). IR (CHCl3): 3687w, 3643m, 3005m,
2958s, 2868m, 1603m, 1509w, 1481w, 1467m, 1432s, 1509w, 1432s, 1362w, 1314w, 1249w, 1157m, 1121w, 864w.
1H-NMR (300 MHz, CDCl3): major isomer: 1.10 (m, 42 H); 3.83 (s, 6 H); 6.87 (d, J ˆ 9, 4 H); 7.41 (d, J ˆ 9, 4 H);
minor isomer: 1.14 (m, 42 H); 3.82 (s, 6 H); 6.86 (d, J ˆ 9, 4 H); 7.47 (d, J ˆ 9, 4 H). 13C-NMR (75 MHz, CDCl3):
160.6; 148.4, 148.3; 133.8, 133.7; 114.7; 114.4; 104.5; 100.0, 99.7; 97.3, 97.2; 88.4, 88.3; 87.3; 55.6; 18.8; 11.6.
‡
‡
‡
MALDI (DCTB): 672 (M ). HR-MALDI-MS: 672.3805 (M , C44H56O2Si2 ; calc. 672.3819).
1,8-Diferrocenyl-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne (5f). BuLi (1.5m in hexanes,
0.467 ml, 0.70 mmol), 2f (0.402 g, 0.70 mmol), and [CuI ´ PBu3] (0.275 g, 0.70 mol) were reacted as described for
5b to give 5f (0.188 g, 37%) after CC (SiO2; hexane/CH2Cl2 9 :1) and GPC (CH2Cl2). Green solid, mixture of
slowly equilibrating cis- and trans-conformers in a 40 :60 ratio (1H-NMR, without configurational assignment).
Rf (hexane/CH2Cl2 9 :1) 0.17. M.p. 1058. UV/VIS (CH2Cl2): 602 (3450), 452 (17800). IR (CDCl3): 2959s, 2945s,
2891m, 2866s, 2184m, 2134w, 2003w, 1605w, 1542w, 1464m, 1412w, 1380w, 1301w, 1265w, 1226vs, 1106w, 997w,
935w, 883w, 825w. 1H-NMR (300 MHz, CDCl3): major isomer: 1.13( s, 42 H); 4.26 (s, 10 H); 4.31 (t, J ˆ 2, 4 H);
7.41 (t, J ˆ 2, 4 H); minor isomer: 1.14 (m, 42 H); 4.25 (s, 10 H); 4.31 (t, J ˆ 2, 4 H); 4.50 (t, J ˆ 2, 4 H). 13C-NMR
(75 MHz, CDCl3): 147.6, 147.5; 104.7, 104.6; 99.1, 98.8; 97.4, 97.3; 86.5; 85.8, 85.7; 71.9, 71.8; 70.3; 70.1, 69.8; 64.2,
‡
‡
‡
64.1; 18.8; 11.5. MALDI (DCTB): 828 (100, M ). HR-MALDI-MS: 828.2918 (M , C50H60Fe2Si2 ; calc.
828.2932).
2,2,11,11-Tetramethyl-5,8-bis[(triisopropylsilyl)ethynyl]dodeca-5,6,7-triene-3,9-diyne (5g). BuLi (1.15m in
hexanes, 0.690 ml, 0.81 mmol), 2f (0.355 g, 0.81 mmol), and [CuI ´ PBu3] (0.318 g, 0.81 mol) were reacted as
described for 5b to yield 5g (0.056 g, 24%) after CC (SiO2; hexane) and GPC (CH2Cl2). Yellow oil, mixture of
slowly equilibrating cis- and trans-isomers in a 45 :55 ratio (1H-NMR, without configurational assignment). Rf
(hexane) 0.32. UV/VIS (CH2Cl2): 419 (29400), 390 (29800), 370 (25900), 346 (18100). IR (CDCl3): 2945m,
2866m, 2253m, 2202w, 1463m, 1383w, 1363w, 1288w, 1216s, 1096w, 996w, 816w. 1H-NMR (300 MHz, CDCl3):
major isomer: 1.10 (m, 42 H); 1.26 (s, 18 H); minor isomer: 1.08 (m, 42 H); 1.25 (s, 18 H). 13C-NMR (75 MHz,
CDCl3): 150.5, 150.2; 106.0, 105.8; 105.2; 98.9, 98.7; 87.3; 78.3, 78.2; 30.7; 28.7; 18.8; 11.5. MALDI-MS (DCTB):
‡
‡
‡
‡
351 (100, [M ‡ Na À 5 i-PrÀ 2 Me] ), 573(20, M ), 595 (21, [M ‡ Na] ). HR-MALDI-MS: 572.4201 (M ,
‡
‡
‡
C38H60Si2 ; calc. 572.4234); 595.4119 ([M ‡ Na] , C38H60NaSi2 ; calc. 595.4131).
3-[3,5-Di(tert-butyl)phenyl]prop-2-yn-1-ol (6c). BuLi (1.5m in hexanes, 1.02 ml, 1.52 mmol) was added to
[3,5-di(tert-butyl)phenyl]acetylene (0.326 g, 1.52 mmol) in THF (8 ml) at À 108, and the orange soln. was stirred
for 30 min. Paraformaldehyde (0.055 g, 1.82 mmol) was added, and stirring was continued for 4 h, while the

Helvetica Chimica Acta ± Vol. 87 (2004)
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temp. reached 208. Sat. aq. NH4Cl soln. (10 ml) was added, the mixture was extracted with Et2O (2 Â 30 ml), and
the combined org. phases were washed with sat. aq. NH4Cl soln. (10 ml) and dried (MgSO4). Evaporation in
vacuo, followed by CC (SiO2; hexane/CH2Cl2 1 :1), provided 6c (0.308 g, 83%). Yellow oil. Rf (hexane/CH2Cl2
1:1) 0.17. IR (CHCl3): 3684w, 3619m, 3461w, 3019vs, 2975s, 2896m, 2405m, 2400s, 1521w, 1476m, 1424m, 1394m,
1218vs, 1045s, 910vs, 878s, 851m. 1H-NMR (300 MHz, CDCl3): 1.31 (s, 18 H); 1.62 (t, J ˆ 6, 1 H); 4.50 (d, J ˆ 6,
2 H); 7.3 0 (d, J ˆ 2, 2 H); 7.38 (t, J ˆ 2, 1 H). 13C-NMR (75 MHz, CDCl3): 150.7; 125.9; 122.9; 121.3, 86.9; 85.9;
‡
‡
‡
51.8; 34.9; 31.4. EI-MS: 244.2 (25, M ), 229.1 (100, [M À OH] ), 153.0 (29, [M À t-Bu À OH] ), 115.1 (14, [M À
‡
2 t-Bu À OH] ). Anal. calc. for C17H24O (244.18): C 82.73, H 6.25; found: C 82.56, H 6.13.
3-[3,5-Di(tert-butyl)phenyl]propynal (7c). MnO2 (0.223g, 2.59 mmol) was added to 6c (0.181 g,
0.74 mmol) in CH2Cl2. After stirring for 24 h at 208, the mixture was filtered through Celite, and the solvent
was evaporated in vacuo. The product (0.152 g, 85%), the purity of which was controlled by NMR, was directly
used for further conversions. Rf (hexane/CH2Cl2 1:1) 0.32. 1H-NMR (300 MHz, CDCl3): 1.32 (s, 18 H); 7.46 (d,
J ˆ 2, 2 H); 7.55 (t, J ˆ 2, 1 H); 9,43( s, 1 H). 13C-NMR (75 MHz, CDCl3): 177.2; 151.7; 128.0; 126.2; 118.7; 97.2;
88.1; 35.1; 31.4.
3-Ferrocenylpropynal (7e). BuLi (1.1m in hexanes, 7.13ml, 7.7 mmol) was added to
a soln. of
ethynylferrocene (1.47 g, 7 mmol) in THF (35 ml) cooled to À 788. After stirring the darkened soln. for 1 h
at this temp., DMF (1.46 ml, 19.0 mmol) was added. Stirring was continued for 1 h at À 788, then the mixture
was warmed to 208 and poured into ice-cold H2O (50 ml) containing conc. HCl (8 ml). The purple soln. was
neutralized with aq. NaHCO3 soln and turned red. The org. phase was extracted with Et2O, washed with H2O,
dried (MgSO4), and filtered through Celite. The red oil obtained after evaporation was purified by CC (SiO2;
hexane/CH2Cl2 8 :2 ! 5 :5) to give 7e (1.503g, 90%) with properties identical to those described in [44]. Red
crystals. Rf (hexane/CH2Cl2 7:3) 0.16. 1H-NMR (300 MHz, CDCl3): 4.25 (s, 5 H); 4.43( t, J ˆ 2, 2 H,); 4.61 (t, J ˆ
2, 2 H); 9.28 (s, 1 H).
1,1-Dibromo-4-(triisopropylsilyl)but-1-en-3-yne (8a). CBr4 (1.32 g, 4 mmol), Ph3P (1.05 g, 4 mmol), and Zn
(0.262 g, 4 mmol) were suspended in CH2Cl2 (5 ml). The soln. was stirred for 45 min at 208, then 7a (0.420 g,
2 mmol) was added. After stirring for 5 h at 208, hexane (50 ml) was added, and the suspension was filtered, the
obtained precipitate was dissolved in CH2Cl2 and re-precipitated with hexane. The combined filtrates were
concentrated in vacuo, and the resulting oil was purified by CC (SiO2; hexane) to afford 8a (0.470 g, 65%). Clear
yellow oil. Rf (hexane) 0.66. IR (CHCl3): 3010m, 3021m, 2946vs, 2891vs, 2865vs, 2759w, 2726w, 2166m, 2118m,
1646w, 1562m, 1463vs, 1384s, 1367s, 1260s, 1220vs, 1070vs, 1018s, 997vs, 954w, 919s, 883vs, 846vs, 824s. 1H-NMR
(300 MHz, CDCl3): 1.10 (s; 21 H); 6.61 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 120.2; 103.2; 102.7; 101.0; 18.8;
‡
‡
‡
‡
11.4. EI-MS: 365.9 (38, M ), 322.9 (81, [M À i-Pr] ), 282.8 (26, [M À 2 i-Pr] ), 266.8 (33, [M À 2 i-PrÀ Me] ),
‡
‡
‡
252.7 (36, [M À 2 i-PrÀ 2 Me] ), 202.8 (62, [M À 2 i-PrÀ Br] ), 159.0 (65, [M À 3i-Pr À Br] ), 76.9 (100, [M À 2
‡
i-PrÀ 2 Br] ). Anal. calc. for C13H22Br2Si (366.21): C 42.64, H 6.05; found: C 42.72, H 5.93.
1-(4,4-Dibromobut-3-en-1-ynyl)-4-(dimethylamino)benzene (8b). CBr4 (0.662 g, 2 mmol), Ph3P (0.526 g,
2 mmol), Zn (0.131 g, 2 mmol), and 7b (0.212 g, 1 mmol) were reacted as described for 8a to deliver 8b (0.109 g,
33%) after CC (SiO2; hexane/CH2Cl2 8 :2). Yellow solid. Rf (hexane/CH2Cl2 1 :1) 0.63. M.p. 698. IR (CHCl3):
3012m, 2191m, 1608vs, 1566w, 1520s, 1446w, 1364m, 1226vs, 1215m, 1211vs, 1210m, 1205w, 1192m, 1170w, 1127w,
1028w, 945w, 848w, 819m. 1H-NMR (300 MHz, CDCl3): 2.99 (s, 6 H); 6.62 (d, J ˆ 9, 2 H); 6.75 (s, 1 H); 7.3 6 (d,
J ˆ 9, 2 H). 13C-NMR (75 MHz, CDCl3): 150.4; 132.7; 120.1; 11.7; 111.5; 108.8; 99.0; 84.9; 40.2. MALDI-MS
‡
‡
‡
‡
(DHB): 329.9 (100, MH ), 328.9 (48, M ). HR-MALDI-MS: 329.9306 (100, MH , C12H11Br2N ; calc.
329.9316).
1-(4,4-Dibromobut-3-en-1-ynyl)-3,5-di(tert-butyl)benzene (8c). CBr4 (0.404 g, 1.22 mmol), Ph3P (0.321 g,
1.22 mmol), Zn (0.080 g, 1.22 mmol), and 7c (0.147 g, 0.61 mmol) were reacted as described for 8a to give 8c
(0.138 g, 57%) after CC (SiO2; hexane). White solid. Rf (hexane) 0.76. M.p. 888. IR (CHCl3): 3023s, 3020vs,
3016s, 2966m, 2905w, 2869w, 2200w, 1478w, 1395w, 1227w, 1223m, 1211m, 1205vs. 1H-NMR (300 MHz, CDCl3):
1.32 (s, 18 H); 6.78 (s, 1 H); 7.3 3 d(, J ˆ 2, 2 H); 7.44 (d, J ˆ 2, 1 H). 13C-NMR (75 MHz, CDCl3): 150.9; 125.7;
‡
‡
123.5; 121.3; 119.7; 101.2; 98.4; 85.0; 34.9; 31.4. EI-MS: 398.0 (50, M ), 383.0 (68, [M À Me] ), 238.1 (6, [M À 2
‡
‡
‡
Br] ), 223.1 (20, [M À 2 BrÀ Me] ), 191.0 (15, [M À C4HBr2] ). Anal. calc. for C18H22Br2 (398.18): C 54.30,
H 5.57; found: C 54.05, H 5.65.
1-(4,4-Dibromobut-3-en-1-ynyl)-4-methoxybenzene (8d). CBr4 (2.09 g, 6.32 mmol), Ph3P (1.66 g,
6.32 mmol), Zn (0.413 g, 6.32 mmol), and 7d (0.506 g, 3.16 mmol) were reacted as described for 8a to provide
8d (0.734 g, 74%) after CC (SiO2; hexane/CH2Cl2 8 :2). Yellow solid. Rf (hexane/CH2Cl2 7:3) 0.65. M.p. 54 ± 558.
IR (CHCl3): 3011m, 2962w, 2937w, 2840m, 2549w, 2200vs, 2047w, 1607vs, 1568s, 1507vs, 1465s, 1442s, 1415w,
1295s, 1279s, 1250vs, 1223s, 1218vs, 1217w, 1214s, 1209w, 1205m, 1181s, 1173vs, 1108m, 1036vs, 1022m, 1006w,
850vs, 834vs. 1H-NMR (300 MHz, CDCl3): 3.82 (s, 3H); 6.75 ( s, 1 H); 6.85 (d, J ˆ 9, 2 H); 7.42 (d, J ˆ 9, 2 H).

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Helvetica Chimica Acta ± Vol. 87 (2004)
‡
13C-NMR (75 MHz, CDCl3): 160.0; 133.0; 119.7; 114.4; 114.0; 105.6; 97.4; 85.2; 55.4. EI-MS: 315.9 (65, M ),
‡
‡
‡
‡
300.9 (37, [M À Me] ), 156.0 (41, [M À 2 Br] ), 141.0 (42, [M À 2 BrÀ Me] ), 127.9 (15, [M À CBr2 À Me] ),
‡
113.0 (100, [M À CBr2 À OMe] ). Anal. calc. for C11H8Br2 (313.89): C 41.81, H 2.55; found: C 41.79, H 3.00.
(4,4-Dibromobut-3-en-1-ynyl)ferrocene (8e). CBr4 (4.18 g, 12.63mmol), Ph 3P (3.31 g, 12.63 mmol), Zn
(0.826 g, 12.63mmol), and 7e (1.503g, 6.31 mmol) were reacted as described for 8a to afford 8e (1.883g, 76%)
after CC (SiO2; hexane). Orange solid. Rf (hexane/CH2Cl2 1:1) 0.67. M.p. 588. IR (CHCl3): 3101w, 3016w,
2983w, 2929w, 2483w, 2203vs, 1472m, 1465m, 11437w, 11419w, 1394s, 1387s, 1277w, 1257w, 1216w, 1204w, 1107s,
1098m, 1074w, 1051w, 1026w, 1004m, 826w. 1H-NMR (300 MHz, CDCl3): 4.24 (s, 5 H); 4.26 (t, J ˆ 2, 2 H); 4.48
(t, J ˆ 2, 2 H); 6.65 (s, 1 H). 13C-NMR (75 MHz, CDCl3): 120.0; 99.8; 97.3; 82.6; 71.5; 70.2; 69.4; 63.9. MALDI-
‡
‡
‡
MS (DCTB): 394 (100, M ). HR-MALDI-MS: 393.8498 (M , C14H10Br2Fe ; calc. 393.8498). Anal. calc. for
C14H10Br2Fe (393.89): C 42.69, H 2.56; found: C 42.90, H 2.85.
1,8-Bis(triisopropylsilyl)octa-3,4,5-triene-1,7-diyne (9a). BuLi (1.5m in hexanes, 0.707 ml, 1.06 mmol) was
added to 8a (0.386 g, 1.06 mmol) in Et2O (7 ml) at À 1108. The mixture was stirred for 1 h at À 1008, then a soln.
of [CuI ´ PBu3] (0.416 g, 1.06 mol) in Et2O (5 ml) was added. The resulting red soln. was stirred for 1 h at À 858,
after which it was allowed to warm to 208 within 5 h. After stirring for 12 h at 208, the now orange soln. was
filtered through SiO2. Evaporation in vacuo afforded a brown oil, which was purified by CC (SiO2; hexane) to
give 9a (0.131 g, 60%) as a mixture of cis- and trans-isomers in a 31:69 ratio (1H-NMR). Clear oil. From this
mixture, one isomer (A) was obtained in pure form (0.029 g, 13%). Isomer A: Rf (hexane) 0.65. 1H-NMR
(300 MHz, CDCl3): 1.09 (m, 42 H); 5.74 (s, 2 H). 13C-NMR (75 MHz, CDCl3): 161.6; 104.1; 101.0; 92.3; 18.7,
11.4. Isomer B: Rf (hexane) 0.67. 1H-NMR (300 MHz, CDCl3): 1.09 (m, 42 H); 5.66 (s, 2 H). 13C-NMR (75 MHz,
CDCl3): 161.3; 104.3; 100.9; 92.1; 18.7; 11.4. Isomeric mixture: UV/VIS (CH 2Cl2): 356 (3150), 332 (1600). IR
(CHCl3): 3683w, 3018m, 3015w, 2944vs, 2891m, 2865vs, 2182w, 1602m, 1464m, 1315w, 1228m, 1224vs, 1221vs,
‡
‡
1219w, 1216s, 1212vs, 1210s, 1207vs, 1204m, 997w, 884m. EI-MS: 412.3(14, M ), 370.2 (60, [M À i-Pr] ), 327.2
‡
‡
‡
‡
(37, [M À 2 i-Pr] ), 285 (100, [M À 3i-Pr] ), HR-EI-MS: 413.2968 (MH , C26H44Si2 ; calc. 413.2982).
1,8-Bis[4-(dimethylamino)phenyl]octa-3,4,5-triene-1,7-diyne (9b). BuLi (1.5m in hexanes, 0.534 ml,
0.8 mmol), 8b (0.262 g, 0.8 mmol), and [CuI ´ PBu3] (0.314 g, 0.8 mmol) were reacted as described for 9a to
provide 9b (0.025 g, 19%) after CC (SiO2; hexane/CH2Cl2 7:3). Red solid, mixture of cis- and trans-isomers in a
72 :28 ratio (1H-NMR, without configurational assignment). Rf (hexane/CH2Cl2 6 :4) 0.22. M.p. 70 ± 738. UV/
VIS (CH2Cl2): 489 (5400), 439 (3600). IR (CHCl3): 3019w, 2170w, 1795w, 1606w, 1214s, 1097w, 996w, 816w.
1H-NMR (300 MHz, CDCl3): major isomer: 2.99 (s, 12 H); 5.84 (s, 2 H); 6.62 (d, J ˆ 9, 4 H); 7.34 (d, J ˆ 9, 4 H);
minor isomer: 3.00 (s, 12 H); 5.79 (s, 2 H); 6.64 (d, J ˆ 9, 4 H); 7.37 (d, J ˆ 9, 4 H). 13C-NMR (75 MHz, CDCl3):
155.9; 150.2; 133.0, 132.9; 111.7; 109.6, 109.4; 99.7, 99.6; 90.3, 90.2; 87.8, 87.7; 40.2. MALDI-MS (DCTB): 338.2
‡
‡
‡
(100, M ). HR-MALDI-MS: 338.1774 (100, M , C24H22N2 ; calc. 338.1783).
1,8-Bis(ferrocenyl)octa-3,4,5-triene-1,7-diyne (9e). BuLi (1.5m in hexanes, 0.647 ml, 1 mmol), 8e (0.395 g,
1 mmol), and [CuI ´ PBu3] (0.393 g, 1 mmol) were reacted as described for 9a to yield 9e (0.210 g, 45%) after CC
(SiO2; hexane/CH2Cl2 9 :1). Red solid, mixture of cis- and trans-isomers in a 52 :48 ratio (1H-NMR, without
configurational assignment). Rf (hexane/CH2Cl2 1 :1) 0.42. M.p. 51 ± 538. UV/VIS (CH2Cl2): 516 (1150), 408
(4100). IR (neat): 2940w, 2862w, 1590s, 1511s, 1446w, 1365w, 1321m, 1302m, 1285m, 1252m, 1196s, 1173s, 1147s,
1
1070w, 1015m, 996vs, 93 6w, 922w, 862s, 825vs. H-NMR (300 MHz, CDCl3): major isomer: 4.25 (s, 10 H); 4.30
(m, 4 H); 4.51 (t, J ˆ 2, 4 H); 5.75 (s, 2 H); minor isomer: 4.26 (s, 10 H); 4.30 (m, 4 H); 4.48 (t, J ˆ 2, 4 H); 5.78 (s,
2 H). 13C-NMR (75 MHz, CDCl3): 156.7, 156.3; 97.5, 97.2; 89.6; 84.9; 70.6, 70.5; 69.1; 68.7, 68.6; 63.9, 63.8.
‡
‡
‡
‡
MALDI-MS (DCTB): 468. 3(60, M ); 467.0 (100, [M À H] ). HR-MALDI-MS: 468.0254 (M , C28H20Fe2 ; calc.
468.0258).
4,5-h2-{1,8-Bis[3,5-di(tert-butyl)phenyl]-3,6-bis[(triisopropylsilyl)ethynyl]octa-3,4,5-triene-1,7-diyne}(chloro)-
bis(triphenylphosphine)rhodium(I) (10d). [RhCl(PPh3)3] in CH2Cl2 (3ml) was added to 5d (0.060 g, 0.072 mmol)
in CH2Cl2 (3ml), and the mixture was stirred for 3d at 20 8. The mixture was filtered through Celite, and the
solvent was removed in vacuo. The crude product was purified by CC (SiO2; hexane/CH2Cl2 7:3), providing,
besides recovered starting material (17%), a green solid, which was further purified by GPC to give 10d
1
(isomeric mixture; 0.078 g, 72%). Rf (hexane/CH2Cl2 1:1) 0.32. H-NMR (300 MHz, CDCl3): 1.10 (m, 84 H);
1.44, 1.43, 1.36, 1.34, 1.30, 1.29 (s, 72 H); 7.26 ± 7.35 (m, 36 H); 7.42 (m, 2 H); 7.48 (d, J ˆ 2, 2 H); 7.52 (d, J ˆ 2,
2 H); 7.56 (m, 2 H); 7.62 ± 7.70 (m, 24 H); 7.77 (m, 4 H). 13C-NMR (75 MHz, CDCl3): 151.3; 151.2; 150.4; 149.9;
135.2m; 13 1.8 (t, J(P,C) ˆ 21); 130.5; 130.3; 130.2; 130.0; 128.0 (d, J(P,C) ˆ 4); 126.9; 126.0; 125.9; 123.5; 123.0;
122.2; 115.2; 115.0; 106.4; 104.0; 103.0; 98.1; 97.6; 97.4; 94.9; 91.5; 91.2; 90.7; 88.9; 88.7; 80.6; 35.1; 34.9; 34.7; 31.5;
‡
31.4; 31.3; 31.2; 18.9; 18.8; 18.7; 11.8; 11.7; 11.6; 11.4. MALDI-MS (DHB): 1238 (41, [M À PPh3] ), 1202 (30,
‡
‡
‡
[M À PPh3 À Cl] ), 1160 (6, [M À PPh3 À Cl À i-Pr] ), 1118 (41, [M À Ph3P À Cl À 2 i-Pr] ), 1075 (100,

Helvetica Chimica Acta ± Vol. 87 (2004)
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‡
‡
‡
[M À Ph3P À Cl À 3i-Pr] ), 662 (15, [Rh(PPh3)2Cl] ), 627 (51, [Rh(Ph3)2)] ). HR-MALDI-MS: 1236.5739
‡
‡
([M À PPh3] , C76H99ClPRhSi2 ; calc. 1236.5766).
1,5-Bis(ferrocenyl)penta-1,4-diyn-3-ol (11c). EtMgBr in THF (2.2 ml, 2.2 mmol) was added to ethynylfer-
rocene (0.420 g, 2 mmol) in Et2O (3ml), and the red soln. was heated to 45 8 for 90 min. After cooling to 08, ethyl
formate (0.077 ml, 0.921 mmol) was added, and stirring was pursued for 5 h at 208. Sat. aq. NH4Cl soln. (10 ml)
was added, and the phases were separated. The aq. phase was extracted again with Et2O. The combined org.
phases were washed with sat. aq. NaHCO3 soln. (20 ml) and H2O, and dried (MgSO4). Evaporation in vacuo
gave a residue, which was purified by CC (hexane/CH2Cl2 3:7) to deliver 11c (0.202 g, 49%). Brown solid. Rf
(hexane/CH2Cl2 3:7) 0.26. M.p. 65 8. IR (CHCl3): 3683w, 3604w, 3439w (br.), 3020vs, 3013m, 2399w, 2231w,
1602w, 1227w, 1225w, 1222w, 1217s, 1214vs, 1212s, 1210vs, 1207m, 1204w, 1106w, 1004m, 823m. 1H-NMR
(300 MHz, CDCl3): 2.21 (d, J ˆ 7.5, 1 H); 4.21 (t, J ˆ 2, 2 H); 4.24 (s, 5 H); 4.47 (t, J ˆ 2, 2 H); 5.55 (d, J ˆ 7.5,
‡
1 H). 13C-NMR (75 MHz, CDCl3): 83.5; 83.0; 71.6; 70.0; 69.0; 63.8; 53.6. MALDI-MS (DHB): 448.0 (80, M ),
‡
‡
‡
(100, [M À OH] ). HR-MALDI-MS: 448.0208 (80, M , C25H20Fe2O ; calc. 448.0213); 431.0174 (100, [ M À
‡
‡
OH] , C25H19Fe2 ; calc. 431.0186).
1,5-Bis(4-methoxyphenyl)penta-1,4-diyn-3-ol (11a). 4-Ethynylanisole (0.265 g, 2 mmol), EtMgBr (2.2 ml,
2.2 ml), and HCO2Et (0.077 ml, 0.921 mmol) were reacted as described for 11c to give 11a (0.159 g, 59%) with
properties identical to those described in [45]. Orange solid. Rf (CH2Cl2) 0.38. M.p. 908 ([45]: 90.58). 1H-NMR
(300 MHz, CDCl3): 2.32 (d, J ˆ 8, 1 H); 3.82 (s, 6 H); 5.55 (d, J ˆ 8, 1 H); 6.85 (d, J ˆ 9, 4 H); 7.43( d, J ˆ 9, 4 H).
13C-NMR (75 MHz, CDCl3): 159.8; 133.3; 133.0; 113.8; 84.9; 84.4; 55.3; 53.3.
1,5-Bis[4-(dimethylamino)phenyl]penta-1,4-diyn-3-ol (11b). 4-Ethynyl-N,N-dimethylaniline (0.290 g,
2 mmol), EtMgBr (2.2 ml, 2.2 ml), and HCO2Et (0.077 ml, 0.921 mmol) were reacted as described for 11c, to
give 11b (0.131 g, 45%) with properties identical to those described in [46]. Brown solid. Rf (CH2Cl2) 0.21. M.p.
1418 ([46]: 143± 145). 1H-NMR (300 MHz, CDCl3): 2.30 (d, J ˆ 7.5, 1 H); 2.98 (s, 12 H); 5.56 (d, J ˆ 7.5, 1 H);
6.61 (d, J ˆ 9, 4 H); 7.80 (d, J ˆ 7.5, 4 H). 13C-NMR (75 MHz, CDCl3): 150.2; 132.9; 111.6; 108.8; 85.3; 84.6; 53.5;
40.2.
1,5-Bis(ferrocenyl)penta-1,4-diyn-3-one (12c). MnO2 (0.294 g, 3.42 mmol) was added to 11c (0.200 g,
0.44 mmol) in Et2O. After stirring for 12 h at 208, the mixture was filtered through Celite, and the solvent was
removed in vacuo to deliver 12c (0.143g, 73%). Red powder. M.p. 70 8. Rf (hexane/CH2Cl2 3:7) 0.47. IR
(CHCl3): 3689w, 3014w, 2183vs, 1300s, 1227m, 1224w, 1221s, 1214vs, 1209vs, 1206s, 1204w, 1129s, 1107w, 1029s,
1003w, 821w. 1H-NMR (300 MHz, CDCl3): 4.30 (s, 10 H); 4.43( t, J ˆ 2, 4 H); 4.66 (t, J ˆ 2, 4 H). 13C-NMR
‡
(75 MHz, CDCl3): 159.9; 94.7; 88.4; 73.3; 71.1; 70.6; 59.9. MALDI-MS (DHB): 447.0 (100, MH ), 446.0 (86,
‡
‡
‡
M ). HR-MALDI-MS: 446.0059 (M , C25H18Fe2O ; calc. 446.0056).
1,5-Bis(4-methoxyphenyl)penta-1,4-diyn-3-one (12a). MnO2 (0.294 g, 3.42 mmol) and 11a (0.166 g,
0.59 mmol) were reacted as described for 12c to deliver 12a (0.691 g, 94%) with properties identical to the
ones previously described in [42]. Orange powder. Rf (CH2Cl2) 0.43. M.p. 117 ± 1198 ([42]: 124 ± 1258) 1H-NMR
(300 MHz, CDCl3): 3.86 (s, 3H); 6.92 ( d, J ˆ 9, 4 H); 7.61 (d, J ˆ 9, 4 H). 13C-NMR (75 MHz, CDCl3): 161.8;
160.7; 135.3; 114.3; 111.3; 92.5; 89.7; 55.5.
1,5-bis[4-(dimethylamino)phenyl]penta-1,4-diyn-3-one (12b). MnO2 (0.185 g, 2.15 mmol) and 11b (0.136 g,
0.43mmol) were reacted as described for 12c to deliver 12b (0.124 g, 92%) after CC (SiO2; CH2Cl2/hexane 1:1
then 1:0). Red solid with properties identical to those described in [43]. Rf (CH2Cl2) 0.3. M.p. 140 ± 1428 ([43]:
143± 145 8). 1H-NMR (300 MHz, CDCl3): 3.04 (s, 12 H); 6.63( d, J ˆ 9, 4 H); 7.41 (d, J ˆ 9, 4 H). 13C-NMR
(75 MHz, CDCl3): 161.0; 152.1; 135.6; 111.8; 105.4; 95.6; 91.3; 40.2.
3-(Dibromomethylidene)-1,5-bis(4-methoxyphenyl)penta-1,4-diyne (13a). CBr4 (1.58 g, 4.76 mmol), Ph3P
(1.25 g, 4.76 mmol), and Zn (0.311 g, 4.76 mmol) were suspended in a CH2Cl2 (10 ml), and the soln. was stirred
for 90 min at 208. Ketone 12a (0.690 g, 2.38 mmol) was added, and the darkened soln. was stirred for 3 d at 208.
Hexane (100 ml) was added, and the suspension was filtered. The precipitate was dissolved in CH2Cl2 and re-
precipitated with hexane. The combined filtrates were concentrated in vacuo, and the obtained yellow solid was
purified by short CC (SiO2; hexane/CH2Cl2 7:3) to afford 13a (0.553g, 52%). Clear yellow solid. Rf (CH2Cl2)
0.5. M.p. 127 ± 1288. IR (CHCl3): 3028w, 3017m, 3014w, 2840w, 2197m, 1606s, 1512s, 1465w, 1442w, 1291m, 1251s,
1227m, 1223vs, 1221w, 1215vs, 1211s, 1208s, 1204s, 1181w, 1173m, 1124w, 1108w, 1031m, 83 m4 . 1H-NMR
(300 MHz, CDCl3): 3.84 (s, 6 H); 6.87 (d, J ˆ 9, 4 H); 7.48 (d, J ˆ 9, 4 H). 13C-NMR (75 MHz, CDCl3): 160.2;
‡
‡
133.2; 114.5; 114.2; 114.0; 105.8; 95.9; 85.2; 55.4. EI-MS: 445.9 (23, M ), 286.2 (100, [M À 2 Br] ), 271.2 (61,
‡
‡
‡
[M À 2 Br À Me] ), 256.1 (8, [M À 2 BrÀ 2 Me] ), 243.2 (20, [M À 2 Me À CBr2] ). Anal. calc. for C20H14Br2O
(446.14): C 53.84, H 3.16; found: C 53.72, H 3.24.
3-(Dibromomethylidene)-1,5-bis[4-(dimethylamino)phenyl]penta-1,4-diyne (13b). CBr4 (0.431 g,
1.35 mmol), and Ph3P (0.683g, 2.6 mmol) were added to 12b (0.142 g, 0.45 mmol) in benzene (30 ml). The

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Helvetica Chimica Acta ± Vol. 87 (2004)
darkening soln. was stirred for 2 d at 208, then hexane (100 ml) was added, and the formed suspension was
filtered through a plug (SiO2; hexane). Evaporation in vacuo and CC (SiO2; hexane/CH2Cl2 7:3 ! 1 :1)
afforded 13b (0.019 g, 9%). Clear yellow solid. Rf (hexane/CH2Cl2 1:1) 0.71. M.p. 1878 (dec.). IR (CCl4): 3155w,
3053m, 2685w, 2305m, 2253s, 2188m, 1795w, 1607s, 1524m, 1465m, 1423w, 1378m, 1264vs, 1224vs, 1212vs, 1120w,
1
1097w, 906vs. H-NMR (300 MHz, CDCl3): 2.99 (s, 12 H); 6.63( d, J ˆ 9, 4 H); 7.41 (d, J ˆ 9, 4 H). 13C-NMR
‡
(75 MHz, CDCl3): 150.8; 133.2; 114.7; 111.9; 110.1; 103.4; 97.4; 85.2; 40.4. MALDI-MS (DHB): 472 (64, M ),
‡
‡
‡
471.0 (100, [M À H] ). HR-MALDI-MS (DHB): 471.9965 (M , C22H20Br2N2 ; calc. 471.9973).
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Received September 9, 2004