A general synthetic method for 1,1'-bis(diacetylene-group)-connected ferrocene and π-electronic system

Article abstract of DOI:10.1246/bcsj.20100252

In contrast to the facile synthon ethynylferrocene for diacetylene ferrocene (Fc) derivatives, 1,1'-diethynylferrocene for the corresponding 1,1'-bis(diacetylene-group)-connected Fc derivatives is extremely difficult to handle under ordinary conditions, g

Full text of DOI:10.1246/bcsj.20100252

110
Bull. Chem. Soc. Jpn. Vol. 84, No. 1, 110–118 (2011)
© 2011 The Chemical Society of Japan
A General Synthetic Method for 1,1¤-Bis(diacetylene-group)-Connected
Ferrocene and ³-Electronic System
Junro Yoshino, Rumi Shimizu, Naoto Hayashi, and Hiroyuki Higuchi*
Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555
Received September 6, 2010; E-mail: higuchi@sci.u-toyama.ac.jp
In contrast to the facile synthon ethynylferrocene for diacetylene ferrocene (Fc) derivatives, 1,1¤-diethynylferrocene
for the corresponding 1,1¤-bis(diacetylene-group)-connected Fc derivatives is extremely difficult to handle under ordinary
conditions, giving rise to spontaneous self-polymerization. Under modified Eglinton oxidative coupling conditions, it has
been possible to generate 1,1¤-diethynylferrocene in situ readily from a trimethylsilyl-protected precursor and to react it
with other terminal acetylenes. The present tandem reactions could provide a general synthetic method for an extended ³-
electronic conjugation system of 1,1¤-bis(diacetylene-group)-connected Fc derivatives, of which the chemistry has been
scarcely developed.
Over the last two decades, a variety of extended ³-electronic
conjugation systems connected with the 1,3-butadiyn-1,4-diyl
linkage (diacetylene) have been demonstrated for the develop-
ment of new organic functional materials, due to linkage
advantages such as a well-defined rigid, linear molecular
structure, minimal steric hindrance, and ³-conjugation.1 Fur-
thermore these advantageous linkage characteristics are very
closely related to both functionality and processibility of the
materials. In connection with development of functional
materials based on diacetylene-group-connected derivatives,
we have been also constructing various extended ³-electronic
systems (³ES) by oxidative coupling reactions between curious
terminal acetylene components and have been proposing
structural requirements for molecular design through studies
of their structure-property relationships.2
H
Fe
Fe
2
1
πES
Fe
On one hand, in recent years, the ferrocene nucleus [1,3 Fc:
Cp2(Fe), Chart 1] holds a unique position as a promising
candidate for functional materials, particularly by virtue of its
molecular prochirality4 and electron-donating ability.5 Since
the mean distance between faced Cp rings of Fc is ca. 4 ¡,
intramolecular interactions of various types could also be
introduced both electronically and spherically into Fc by
combination with manifold components. The Fc component
itself is mostly introduced into the respective ³ES by
connection with linkages readily derivable on Cp rings, such
as vinylene,6 phenylene,7 and carbonyl analogs,8 according to
their material functions.
Some diacetylene-connected derivatives composed of Fc and
³ES are known as well, described as Fc-³ES, which are
prepared by utilizing oxidative coupling reactions of ethynyl-
ferrocene (2,9 Chart 1) with the corresponding terminal
acetylenes.10 Most of them however, are derivatives in which
the diacetylene linkage is attached to a single Cp ring of Fc
(Chart 1). In practice, strain-free 1,1¤-bis(diacetylene-group)-
connected Fc derivatives have not been reported, except for a
few limited examples, for example, diacetylene-group-bridged
Fc cyclophanes which are sterically hindered and multiply
Diacetylene-group Connected Fc-πES
Chart 1.
protected with bulky tert-butyl groups on both Cp rings.11
Therefore, in those diacetylene-group-linked Fc compounds,
even though studies of one-dimensional interaction between Fc
and ³ES can be performed to some extent, structure-property
investigations of intramolecular multidimensional interaction
between two ³-electronically extended Cp constituents in Fc
cannot be performed comprehensively. This is simply due to
synthetic issues. Actually, no general synthetic method for
electronically unperturbed and strain-free 1,1¤-bis(diacetylene-
group)-linked Fc-³ES derivatives, Fc-(³ES)2, has been
established so far. In contrast to the high utility of ethynyl-
ferrocene (2), 1,1¤-diethynylferrocene (3) which is a promising
synthon is extremely difficult to handle under ordinary
conditions, spontaneously giving rise to self-polymerization
to form diacetylene Fc polymers 4 via oxidative coupling
(Scheme 1).11 Nevertheless, it has been previously reported
Published on the web January 1, 2011; doi:10.1246/bcsj.20100252

J. Yoshino et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
111
H
aerial atmosphere
Fe
Fe
H
n
3
4
Scheme 1.
MeO-
OMe
aq. KOH
TMS
TMS
H
H
Fe
Fe
Fe
deoxygenated MeOH
75-90%
MeOH
5
6
3
Scheme 2.
TMS
πES
H
H
πES
Fe
Fe
Fe
TMS
H
πES
1,1'-Bis(diacetylene-group) Connected Fc-πES: Fc-(πES)2
5
3
Scheme 3.
that the very careful treatment of a deoxygenated solution of
the trimethylsilyl (TMS)-group-protected precursor 5 for 3 in
methanol (MeOH) with aqueous potassium hydroxide (KOH)
gives 1,1¤-(1-methoxy-1,3-butadienylene)ferrocene (6, a [4]-
ferrocenophane) as the only detectable product in isolated
yields from 75% to 90% (Scheme 2).12 Accordingly, without
rigorously controlled countermeasures, the practical use of 3
seems to be impossible. Thus, synthetic difficulty may have
resulted in the paucity of systematic studies of diacetylene-
group-connected Fc-(³ES)2 derivatives. In other words, the
successful development of general synthetic methodology for
1,1¤-bis(diacetylene-group) formation from the very reactive
synthon 3 would further the fundamental chemistries of Fc-
³ES derivatives and could also open a new door of applied
research, concurrently taking the advantages of molecular
prochirality, electron-donating ability, and multidimensional
interactions into account.
The unsettled situation of the synthesis of Fc-(³ES)2
derivatives strongly stimulated us to develop a methodology
for practical use of 3, on the basis of our achievements with
diacetylene-group-connected ³ES derivatives.2 In a previous
communication, we reported the TMS-group-protected deriv-
ative 513 chosen as an analogous synthon for 3 and examined
its behavior in both TMS deprotection and oxidative coupling
under several conditions (see below, Scheme 3). The results
suggested the high potentiality of 5 as a hopeful candidate for
generation of 3 and for construction of the Fc-(³ES)2
derivatives under basic and oxidative conditions.14 In our
continuous investigations of this methodology using 5, it has
been revealed that those reactions proceed efficiently under
appropriate conditions. In this paper, a new methodology for in
situ generation of 3 from 5 will be described, together with its
application to the cross-coupling with some typical terminal
acetylenes for the Fc-(³ES)2 derivatives 7-12 (Chart 2).
Results and Discussion
Reactivity and Behavior of TMS-Group-Protected
1,1¤-Diethynylferrocene 5 under Various Conditions. As
aforementioned, 1,1¤-diethynylferrocene (3) is extremely diffi-
cult to use in synthetic reactions as is. On the other hand, the
bis(TMS)-protected derivative 5 of 3 itself is easily derived
from the corresponding acetylferrocene and handled in air at
ambient temperature.13 Accordingly, it is natural that the
derivative 5 is employed as a useful synthon for Fc-(³ES)2
derivatives. However, as mentioned above, it is apparent that
usual work-up after TMS removal of 5 with KOH in a
deoxygenated H2O-MeOH solution afforded the [4]ferroceno-
phane derivative 6 which is proposed to form via methoxide-

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Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
1,1¤-Bis(diacetylene-group)-Connected Fc-(³ES)2
OCH3
Fe
Fe
Fe
H3CO
7
8
9
CH2CH2CH2CH3
Fe
Fe
Fe
H3CH2CH2HC2C
10
11
12
Chart 2.
Table 1. TMS-Group Deprotection Results of 5 under Various Conditionsa)
Run
Reagents and media
Temperature
Products
1
2
3
4
5
6
7
8
9
K2CO3 (0.3 equiv) in CHCl3-MeOH (1:1)15
K2CO3 (2.0 equiv) in CHCl3-MeOH (1:1)
Py-MeOH (1:1)
RT
RT
RT
50 °C
50 °C
RT
50 °C
50 °C
50 °C
4 + 5 (main)
4
5
Cu(OAc)2 (2.0 equiv) in MeOH-Py (1:1)19
K2CO3 (0.3 equiv)-Cu(OAc)2 (2.0 equiv) in MeOH-Py (1:1)
K2CO3 (2.0 equiv)-Cu(OAc)2 (2.0 equiv) in MeOH-Py (1:1)
5
4 (main) + 5
4 + 5 + 13 (7%)
4 + 5 + 13 (12%)
4 + 13 (37%)
4 + 13 (32%)
K2CO3 (2.0 equiv)-Cu(OAc)2 (2.0 equiv) in CHCl3-MeOH-Py (1:1:1)
K2CO3 (10 equiv)-Cu(OAc)2 (2.0 equiv) in CHCl3-MeOH-Py (1:1:1)
K2CO3 (10 equiv)-Cu(OAc)2 (10 equiv) in CHCl3-MeOH-Py (1:1:1)
a) 5 (50 mg, 1.3 © 10¹1 mmol) was admixed with reagents in 50 cm3 of the solution and was stirred for 10 h.
TMS
TMS
Fe
Fe
13
anion attack on the deprotected product 3 followed by an
intramolecular cyclization (Scheme 2).12 It is also true that
treatment of 5 with potassium carbonate (K2CO3) in once-
distilled MeOH under air for 10 h only afforded insoluble
substances.15 These substances should be a mixture of 1,1¤-
simultaneously with nucleophilic substitution with benzyl
halides (ArCH2-X). Finally, this tandem system proved to be
a convenient synthetic method for bis(ArCH2-group)-bridged
selenides (ArCH2-Se-R-Se-CH2Ar) of various types including
selenacyclophanes in excellent yields.17 Therefore, this suc-
cessful methodology was similarly applied to the coupling
reaction of 5 in a tandem system, TMS deprotection of 5
followed by oxidative coupling with other terminal acetylenes
in one pot. Although especially in the silylated compounds, in
situ TMS-deprotection is widely employed for organic reac-
tions,18 little attention has been paid to TMS-deprotection of 5
for organic syntheses.11,12,14
Preliminarily, the behavior of 5 under limited reaction
conditions was examined. Each reaction was carried out for
10 h under the applied conditions. Poured into water after the
deprotection, the reaction mixture was once filtered to remove
the insoluble substances 4, extracted and separated by means of
successive column chromatography (see Experimental). The
results are summarized in Table 1. The Eglinton media, i.e.,
pyridine (Py), copper(II) acetate [Cu(OAc)2], and/or co-solvent
MeOH in this case were found to be entirely inert to 5, albeit
a slightly basic reaction environment favorable for the TMS-
group deprotection of 5 (Runs 3 and 4).19 When a solution of 5
was added to Eglinton media in the presence of K2CO3, the
£
bis(diacetylene-group)-linked Fc polymers 4 [-(C C-Fc-
£
£
C C)n-], as evidenced by MS spectral measurement
£
(Scheme 1 and also see below). In the latter case, neither the
desired 1,1¤-diethynyl product 3 nor any other assignable
products could be isolated. The difference in product from 5
between these deprotection conditions likely arises from the
content of methoxide-anion in respective reaction media, which
should be further studied mechanistically. Anyway, these facts
simply conclude that the TMS removal of 5 smoothly takes
place even with the very weak base K2CO3 in MeOH to
generate 1,1¤-diethynylferrocene (3) but compound 3 is difficult
to isolate.
Such highly labile behavior of 3 bearing two reaction sites
led us to recall the diselenol synthon (HSe-R-SeH) with a
pronounced tendency toward oxidative polymerization [-(Se-
R-Se-Se-R-Se)n-] under ordinary conditions.16 In order to
handle the reactive diselenol, a corresponding stable diseleno-
cyanide derivative [(NCSe)-R-(SeCN)] was treated in a
tandem system, reduction with sodium borohydride (NaBH4)

J. Yoshino et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
113
Fe
13
4
Fe
H
H
14
Fe
Fe
15
Scheme 4.
K2CO3 (2.0 equiv)
Cu(OAc)2 (2.0 equiv)
16 (1.0 equiv)
Fe
+
+
Fe
5
TMS
RT
MeOH-Py (1:1)
43%
5.2%
8%
7
17
18
Scheme 5.
reaction gradually proceeded to form a linear Fc dimer 13 as a
homocoupling product, together with a considerable quantity of
4 (Runs 5 and 6). The reaction temperature of around 50 °C is
applicable to the present reaction, as is generally the case for
Eglinton coupling.2,19 Chloroform (CHCl3) was also effective
for the reaction (Run 7), probably due to good solubility of
13. Furthermore, it shows that 10 molar equivalents of K2CO3
to 5 works adequately, while 2 molar equivalents of Cu(OAc)2
to 5 is satisfactory (Runs 8 and 9). At this stage, it may be
concluded that the TMS removal of 5 followed by oxidative
coupling to 13 takes place rather efficiently under the
conditions of Run 8.
In this reaction, the cyclic Fc dimer 15, diacetylene-group-
bridged Fc cyclophane, was not isolated at all (Scheme 4). This
indicates that two terminal acetylene sites in 14 exist opposite
from each other in the present reaction media, apparently
suffering a steric disadvantage from the entropy-controlled
coupling reaction.11
As a result, it is suggested that 1,1¤-diethynylferrocene (3)
possibly is generated from the TMS-protected precursor 5 and
is potentially oxidatively coupled with other terminal acety-
lenes to the corresponding diacetylene Fc derivatives, some-
where in the Eglinton oxidative coupling media containing
K2CO3. In fact, this expectation proved to be correct by the
following observations (see below).
Rate of Deprotection of 5 under the Applied Conditions.
According to the preliminary and aforementioned results,14 an
oxidative heterocoupling of TMS-protected derivative 5 with
phenylacetylene (16) was examined in a mixture of MeOH-Py
(1:1) containing Cu(OAc)2 and K2CO3 (Scheme 5). As
expected, the desired 1,1¤-bis(4-phenyl-1,3-butadiynyl) Fc
derivative 7 could be obtained, though not in good yield
(ca. 5% yield under the conditions of Run 6 in Table 1, see
Scheme 5). To our best knowledge however, the present low-
yielded product 7 is the first example of Fc-(³ES)2 derivatives
with no additional substituents on the Cp rings.
In this reaction, it is apparently convenient for phenyl-
acetylene (16) to exist in the same media to react immediately
with the deprotected products from 5, because product 3 is
extremely liable toward self-polymerization. But, it would not
be necessarily profitable for 16 to exist in the same media from
the beginning of deprotection of 5. The TMS removal reaction
of 5 should compete with the oxidative homocoupling of 16 to
17, since both reactions proceed in one pot under basic and
oxidative coupling conditions (Schemes 3 and 5, also see
Table 1). During the progress of the deprotection, the terminal
acetylene 16 is also consumed to some extent to form 17,
resulting in a collapse of molar ratio between 5 and 16
(lowering yield of 7). Yet, needless to say, the reactivity of the
respective terminal acetylenes under the oxidative conditions is
different, though it may be lower than that of 3.
Therefore, deprotection of 5 (1.0 equiv) with K2CO3
(10 equiv) in a mixture of MeOH-Py (1:1) in the absence of
Cu(OAc)2 was followed and observed by means of MS,
because the first stage product 19 could be hardly separated
with column chromatography but could be eventually detected

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Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
K2CO3 (10 equiv)
1,1¤-Bis(diacetylene-group)-Connected Fc-(³ES)2
H
TMS
H
RT
Fe
Fe
Fe
4
TMS
H
TMS
MeOH-Py (1:1)
5 (m/z 378)
19 (m/z 306)
3 (m/z 234)
Scheme 6.
dominantly takes place to form diacetylene Fc polymers 4.
Under the applied conditions, the mono-deprotected product
19 (m/z 306, marked by an arrow in Figure 1a) was negligibly
observed for 15 min since the deprotection of 5 started.
Additionally, compound 19 gradually began forming at around
20 min, as well as polymers 4 (Figures 1b and 1c). After
around 1 h, the intensities of 19 and 5 (m/z 378, marked by an
arrow in Figure 1d) were reversed. The deprotection of 5 was
largely complete within about 10 h, and the first-stage product
19 disappeared completely and was replaced with Fc polymers
4 entirely (Figures 1e and 1f).
These results indicate the existence of a time zone for
addition of the terminal acetylene into the prepared solution,
i.e., between 15 and 20 min after the admixed point of 5 and
K2CO3. In practice, when phenylacetylene (16, 1.0 equiv)
existed in the same media from the beginning of the
deprotection of 5 (1.0 equiv) with K2CO3 (10 equiv) under
the Eglinton conditions [Cu(OAc)2, 2.0 equiv], 1,4-diphenyl-
1,3-butadiyne (17) was the main product (ca. 80% yield) and
1,1¤-bis(diacetylene) Fc derivative 7 was a very minor product
(Scheme 7). Similarly, when 16 was added 30 min later into an
admixed solution of 5 and K2CO3, the yield of 7 was only 8%.
In both cases, insoluble Fc polymers 4 formed in quantity. In
contrast, when 16 was added 15 min later into the admixed
solution of 5 and K2CO3 under the same conditions, the yield
of 7 significantly increased to ca. 40% (Scheme 7). As a
consequence, though it has not been optimized yet, the
respective terminal acetylenes should be added continuously
into the basic and Eglinton media containing 5 ca. 15 min later,
taking the reactivity of 3 and the terminal acetylenes into
consideration (see general procedure in Experimental).
Application to One-Pot Synthesis of Fc-(³ES)2 Deriva-
tives.
Based on a well-thought-out deprotection of 5,
heterocoupling reactions of TMS-protected derivative
5
(1.0 equiv) with typical terminal acetylenes were performed
in a mixture of MeOH-Py-CHCl3 (1:1:1) containing Cu(OAc)2
(2.0 equiv) and K2CO3 (10 equiv) at 50 °C (see Table 1,
Run 8). The solution of 5 was stirred punctually for 15 min
and then a solution of the terminal acetylene (2.0 equiv) was
added to the resultant mixture continuously over 30 min. The
reaction mixture was stirred until the reactants 5 and terminal
acetylene disappeared completely, mostly within around 10 h.
After usual work-up, the mixture was separated by column
chromatography on silica gel (SiO2). The corresponding Fc-
(³ES)2 derivatives 7-12 were successfully obtained in accept-
able yields, together with respective homocoupling products of
the terminal acetylenes (Chart 2).
Figure 1. TMS removal of 5 (50 mg, 1.3 © 10¹1 mmol) with
K2CO3 (1.3 mmol) in a mixture of MeOH and Py (1:1,
50 cm3) was followed by MS measurements in a region of
m/z 50-800. Each reaction mixture was quenched and
treated similarly to the general reaction before measurement
(see Experimental). MS spectra (a) after 15 min, (b) after
20 min, (c) after 30 min, (d) after 1 h, (e) after 2 h, and (f)
the insoluble substances 4.
with MS (Figure 1 and Scheme 6). The m/z value of 234
corresponding to 1,1¤-diethynylferrocene (3) was not observed
at all, indicating that immediately after the second TMS
removal, the oxidative self-coupling of 3 spontaneously and
In the case of the reaction with phenylacetylene (16), the Fc-
³ES derivative 18 bearing one diacetylene linkage could also
be isolated as a by-product (Scheme 5). In addition to the MS

J. Yoshino et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
115
Fe
+
Fe
+
K2CO3 (10 equiv)
TMS
Cu(OAc)2 (2.0 equiv)
MeOH-Py (1:1), RT
7
17
18
5
addition of 16 (1.0 equiv),
after a) 0 min
11%
80%
< 5%
b) 15 min
c) 30 min
39%
8%
30%
16%
< 5%
13%
Scheme 7.
TMS
πES
πES
H
Fe
Fe
Fe
Fe
TMS
TMS
H
TMS
5
19
πES
H
Fe
Fe
πES
H
3
Fe
n
4
Scheme 8.
detection of compound 19, the isolation of compounds 13 and
18 suggests that both TMS deprotection of 5 and diacetylene-
linkage formation leading to Fc-(³ES)2 proceed rather step-
wise under the present conditions, prior to other one-step
courses (Scheme 8). All the Fc-³ES derivatives including 13
and 18 are bright orange microcrystallines and are stable
enough to be stored in a refrigerator for more than 1 year.
in terms of optimization and mechanism for the present
coupling reaction, as well as limitation of application to other
terminal acetylenes such as heterocyclic nucleic compounds
like pyridine and thiophene.20
Experimental
The melting points (Mp) were determined on a hot-stage
apparatus and are uncorrected. EI and FAB mass spectra were
recorded with a JEOL JMS-700 spectrometer. IR spectra were
measured on a Jasco FT/IR 7300 spectrophotometer as KBr
disk or neat sample; only significant absorptions are recorded in
Conclusion
A synthetic methodology for 1,1¤-bis(diacetylene-group)-
connected Fc-(³ES)2 derivatives has been successfully devel-
oped by employing a tandem system, TMS-group deprotection
of 5 and oxidative coupling of the in situ generated synthon 3
(probably via 19) with other terminal acetylenes in one pot. At
present, this synthetic methodology for Fc-(³ES)2 seems to be
applicable to terminal acetylenes of several types bearing not
only alkenyl and aromatic but also alkyl structures, though not
in excellent yields. Therefore, the present results would expand
the research area of diacetylene Fc-³ES derivatives in material
science, since each Cp ring of Fc carries no substituents and
thus inherently is less perturbed both sterically and electroni-
cally.11 Further investigations of the TMS-group-protected
derivative 5 as a useful synthon for Fc-(³ES)2 are under way,
1
¯ values (cm¹1). H NMR spectra were measured in CDCl3
solution on a JEOL ECX-300A (300 MHz) or a JEOL JMN-
EPC 600 (600 MHz) spectrometer and were recorded in ¤
values (ppm) with TMS as an internal standard. The coupling
constants (J) are given in Hz. Electronic absorption spectra
were measured in CHCl3 solution on a Shimadzu UV-2200A
spectrophotometer and absorption maxima of respective bands
are reported in -max values (nm) with their extinction
coefficient (¾) (sh: shoulder). SiO2 (Fujisilysia BW 820MH
or BW 127ZH) was used for column chromatography.
Reactions were followed by TLC on aluminum sheets pre-
coated with Merck SiO2 F254 or with Merck Al2O3 GF254
.

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Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
1,1¤-Bis(diacetylene-group)-Connected Fc-(³ES)2
Organic extracts were dried over anhydrous sodium sulfate
(Na2SO4) or magnesium sulfate (MgSO4) prior to removal of
the solvents.
Compound 18: Yellow-orange microcrystalline (hexane-
CHCl3); mp: gradual decomp. above 160 °C; EI-MS: m/z 406
and 407 (M+ and M+ + 1) for C25H22SiFe as 56Fe; IR (KBr):
1
TMS Deprotection of 5 under the Reaction Conditions of
¯ = 2218, 2148, 1495, and 1430; H NMR: ¤ 7.51 (2H, dm,
Run 8 in Table 1.
A solution of 5 (49 mg, 0.13 mmol),
J = 7.8 Hz, phenyl-H), 7.37-7.28 (3H, m, phenyl-H), 4.52 and
4.50 (2H each, tm, J = 2.0 Hz, Fc-H), 4.29 (4H, broad s, Fc-H),
0.24 (9H, s, SiCH3); UV-vis (¾): 274 (38100), 289 (34400),
311 (30700), 331 (21500, sh), 378 (4800, sh), and 453 (1850).
Anal. Calcd for C25H22SiFe: C, 73.89; H, 5.46%. Found: C,
73.77; H, 5.98%. Attempts to improve the elemental analysis
failed.
Other 1,1¤-bis(diacetylene-group)-connected Fc-³ES deriv-
atives 8-12 were synthesized in a way similar to the general
procedures described above. Basically characteristic properties
of the respective Fc-(³ES)2 derivatives only are shown,
together with those of the corresponding homocoupling
products between terminal acetylenes.
Compound 8: 36% yield. Orange fine needles (hexane-
CHCl3); mp: 177-183 °C (dec); EI-MS: m/z 495 and 496
(M+ + 1 and M+ + 2) for C32H22O2Fe as 56Fe; IR (KBr):
¯ = 3006, 2219, 2144, 1602, 1510, 1251, and 831; 1H NMR: ¤
7.39 (4H, d, J = 8.8 Hz, phenyl-H), 6.77 (4H, d, J = 8.8 Hz,
phenyl-H), 4.57 and 4.35 (4H each, t, J = 2.0 Hz, Fc-H), 3.80
(6H, s, OCH3); UV-vis (¾): -max = 283 (30700), 302 (30100),
319 (29300), 343 (26200, sh), and 451 (1200). Anal. Calcd
for C32H22O2Fe: C, 77.75; H, 4.49%. Found: C, 77.52; H,
4.65%.
Cu(OAc)2 (48 mg, 0.26 mmol), and K2CO3 (179 mg, 1.3 mmol)
in a mixture of CHCl3, MeOH, and Py (50 cm3, 1:1:1) was
stirred at 50 °C for 10 h. The resultant solution was concen-
trated to ca. 10 cm3 under reduced pressure at ambient
temperature. Poured into water and filtered once, the reaction
mixture was extracted with CHCl3. The extracts were washed
with 1 M HCl, with brine, and then dried. The residue obtained
after removal of the solvents was chromatographed (º3 ©
10 cm) with hexane-CHCl3 (3:1) to afford compound 13
(16 mg, 37%) as yellow solid. 13: Orange powder (hexane-
CHCl3); mp: 175-180 °C (dec); EI-MS: m/z 610 and 611 (M+
and M+ + 1) for C34H34Si2Fe2 as 56Fe; IR (KBr): ¯ = 2220,
1
2150, 1495, and 1435; H NMR (600 MHz, CDCl3): ¤ 4.50-
4.48 (8H, m, Fc-H), 4.29 and 4.27 (4H each, tm, J = 2.4 Hz,
Fc-H), 0.25 (18H, s, SiCH3); UV-vis (¾): broad absorption
curve with a shoulder band of -max = 303 nm (38000, sh)
tailing up to around 700 nm. Anal. Calcd for C34H34Si2Fe2: C,
66.89; H, 5.61%. Found: C, 66.85; H, 5.73%.
According to the reaction conditions of Run 8 in Table 1, all
Fc-(³ES)2 derivatives 7-12 in this study were synthesized.
General experimental procedures are described, with 7 as an
example: A solution of 5 (200 mg, 0.53 mmol), Cu(OAc)2
(200 mg, 1.10 mmol), and K2CO3 (760 mg, 5.50 mmol) in a
mixture of Py, MeOH and CHCl3 (200 cm3, 1:1:1) was stirred
for 15 min at 50 °C. To the resulting mixture, phenylacetylene
(16, 120 mg, 1.17 mmol) in the same mixed solution (30 cm3)
was added continuously within 30 min and kept with vigorous
stirring for 10 h. The reaction mixture was concentrated to ca.
one-third in volume under reduced pressure, poured into water,
filtered once to remove insoluble substances 4 and extracted
with CHCl3. The extracts were shaken with 1 M HCl, washed
with brine thoroughly and then dried. The residue obtained
after removal of the solvent under reduced pressure was
chromatographed (º3 © 20 cm) with hexane-CHCl3 (2:1) to
afford compound 7 (115 mg, 50%) and compound 18 (18 mg,
8% based on 5), together with homocoupling product 17
(35 mg, 17% based on 16).
1,4-Bis(p-methoxyphenyl)-1,3-butadiyne: 55% yield. Pale
yellow needles (hexane-CHCl3); mp: gradual decomp. above
175 °C; EI-MS: m/z 262 and 263 (M+ and M+ + 1) for
C18H14O2; IR (KBr): ¯ = 3002, 2840, 2138, 1599, 1504, 1294,
1
1254, 1167, and 842; H NMR: ¤ 7.46 and 6.85 (4H each, d,
J = 9.2 Hz, phenyl-H), 3.81 (6H, s, OCH3). UV-vis (¾):
-
max = 270 (26800), 283 (25100), 300 (28200), 320 (35100),
and 343 (29100). Anal. Calcd for C18H14O2: C, 82.42; H,
5.38%. Found: C, 82.33; H, 5.63%.
Compound 9: 46% yield. Orange fine needles (hexane-
CHCl3); mp: gradual decomp. above 170 °C; FAB-MS: m/z
587 and 588 (M+ + 1 and M+ + 2) for C42H26Fe as 56Fe; IR
(KBr): ¯ = 2923, 2851, 2218, 2148, 1487, 1282, 993, and 841;
1H NMR: ¤ 7.50-7.48 (8H, m, biphenyl-H), 7.44 (4H, d,
J = 5.6 Hz, biphenyl-H), 7.40-7.37 (4H, m, biphenyl-H),
7.36-7.34 (2H, m, biphenyl-H), 4.60 and 4.37 (4H each,
t, J = 2.0 Hz, Fc-H); UV-vis (¾): -max = 285 (47500, sh),
325 (49500), 355 (31300), and 454 (1800). Anal. Calcd
for C42H26Fe: C, 86.01; H, 4.47%. Found: C, 85.86; H,
4.66%.
Compound 7: Orange microcrystalline (hexane-CHCl3);
mp: gradual decomp. above 165 °C; EI-MS: m/z 434 and 435
(M+ and M+ + 1) for C30H18Fe as 56Fe; IR (KBr): ¯ = 2218,
1
2144, 1492, and 1441; H NMR: ¤ 7.45 (4H, dm, J = 6.6 Hz,
phenyl-H), 7.32 (2H, tm, J = 7.2 Hz, phenyl-H), 7.25 (4H, dm,
J = 7.2 Hz, phenyl-H), 4.58 and 4.37 (4H each, tm, J = 2.4 Hz,
Fc-H); UV-vis (¾): -max = 265 (14700), 277 (15800), 295
(14900), 316 (15200), 345 (12500, sh), and 463 (800). Anal.
Calcd for C30H18Fe: C, 82.96; H, 4.18%. Found: C, 82.68; H,
4.41%.
1,4-Bis(p-biphenyl)-1,3-butadiyne: 33% yield. Pale yellow
needles (hexane-CHCl3); mp: gradual decomp. above 160 °C;
EI-MS: m/z 355 and 356 (M+ + 1 and M+ + 2) for C28H18; IR
(KBr): ¯ = 3031, 2923, 2852, 2146, 1598, 1482, 1006, 841,
1
and 766; H NMR: ¤ 7.62-7.58 (12H, m, biphenyl-H), 7.47-
1,4-Diphenyl-1,3-butadiyne (17):21 Colorless fine needles
(hexane-CHCl3); EI-MS: m/z 202 and 203 (M+ and M+ + 1)
for C16H10; IR (KBr): ¯ = 3050, 2148, 1484, 915, and 755;
1H NMR: ¤ 7.54-7.52 (4H, m, phenyl-H) and 7.39-7.32 (6H,
m, phenyl-H); UV-vis (¾): -max = 261 (26200), 290 (15800),
308 (31800), and 330 (29500). Anal. Calcd for C16H10: C,
95.02; H, 4.98%. Found: C, 94.91; H, 5.23%.
7.45 (4H, m, biphenyl-H), 7.39-7.36 (2H, m, biphenyl-H);
UV-vis (¾): -max = 303 (27800, sh), 312 (43800), 333
(50100), and 355 (30000). Anal. Calcd for C28H18: C, 94.88;
H, 5.12%. Found: C, 94.82; H, 5.38%.
Compound 10: 12% yield. Orange needles (hexane-
CHCl3); mp: gradual decomp. above 175 °C; FAB-MS: m/z
634 and 635 (M+ and M+ + 1) for C46H26Fe; IR (KBr):

J. Yoshino et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
117
¯ = 2925, 2850, 2220, 2150, 1485, 1285, and 841; 1H NMR: ¤
8.35-8.28 (6H, m, phenanthryl-H), 7.72 (2H, s, phenanthryl-
H), 7.61-7.38 (10H, m, phenanthryl-H), 4.67 and 4.41 (4H
each, t, J = 1.8 Hz, Fc-H); UV-vis (¾): -max = 317 (44600, sh),
337 (61500), 359 (47600), 379 (20700, sh), and 468 (2800).
Anal. Calcd for C46H26Fe: C, 87.07; H, 4.13%. Found: C,
86.95; H, 4.28%.
References
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1,4-Di-9-phenanthryl-1,3-butadiyne: 58% yield. Yellow
fine needles (hexane-CHCl3); mp: gradual decomp. above
160 °C; EI-MS: m/z 402 and 403 (M+ and M+ + 1) for C32H18;
IR (KBr): ¯ = 3028, 2925, 2850, 2146, 1598, 1482, 840, and
1
760; H NMR: ¤ 8.74-8.68 (4H, m, phenanthryl-H), 8.56-8.53
(2H, m, phenanthryl-H), 8.20 (2H, s, phenanthryl-H), 7.91 (2H,
d, J = 7.9 Hz, phenanthryl-H), 7.76-7.64 (8H, m, phenanthryl-
H); UV-vis (¾): -max = 321 (35600, sh), 334 (55500), 353
(66900), and 381 (62600). Anal. Calcd for C32H18: C, 95.49; H,
4.51%. Found: C, 95.33; H, 4.75%.
Compound 11: 38% yield. Bright orange needles (hexane-
CHCl3); mp: gradual decomp. above 155 °C; EI-MS: m/z 394
and 395 (M+ and M+ + 1) for C26H26Fe as 56Fe; IR (KBr):
¯ = 3103, 2960, 2931, 2860, 2233, 2151, and 824; 1H NMR: ¤
4.48 and 4.28 (4H each, t, J = 1.8 Hz, Fc-H), 2.32 (4H, t,
J = 7.0 Hz, CH2), 1.58-1.41 (8H, m, CH2), 0.93 (6H, t,
J = 7.3 Hz, CH3); UV-vis (¾): -max = 275 (13500, sh), 299
(15400), and 451 (970). Anal. Calcd for C26H26Fe: C, 79.19; H,
6.65%. Found: C, 78.90; H, 6.83%.
3
a) T. J. Kealy, P. L. Pauson, Nature 1951, 168, 1039. b)
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4
a) D. Savage, G. Malone, J. F. Gallagher, Y. Ida, P. T. M.
1,4-Dibutyl-1,3-butadiyne (=5,7-dodecadiyne):22 45%
yield. Colorless solid (hexane); EI-MS: m/z 162 and 163
(M+ and M+ + 1) for C12H18; 1H NMR: ¤ 2.54 (4H, t,
J = 7.2 Hz, CH2), 1.56-1.44 (8H, m, CH2), 0.91 (6H, t,
J = 7.8 Hz, CH3). Anal. Calcd for C12H18: C, 88.82; H,
11.18%. Found: C, 88.61; H, 11.25%.
Kenny, J. Organomet. Chem. 2005, 690, 383. b) D. Obendorf, H.
Schottenberger, K. Wurst, N. Schuler, G. Laus, J. Organomet.
Chem. 2005, 690, 811. c) A. Patti, S. Pedotti, Tetrahedron:
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Organomet. Chem. 2008, 693, 1716.
5
a) H. Imahori, Y. Mori, Y. Matano, J. Photochem. Photo-
Compound 12: 53% yield. Orange powder (hexane-
CHCl3); mp: gradual decomp. above 165 °C; EI-MS: m/z 443
and 444 (M+ + 1 and M+ + 2) for C30H26Fe as 56Fe; IR (KBr):
¯ = 3102, 2930, 2860, 2211, 2138, 1346, 1239, 990, and 827;
1H NMR: ¤ 6.30-6.28 (2H, m, olefinic-H), 4.51 and 4.31 (4H
each, t, J = 2.0 Hz, Fc-H), 2.17-2.15 (4H, m, CH2), 2.13-2.10
(4H, m, CH2), 1.65-1.62 (4H, m, CH2), 1.61-1.55 (4H, m,
CH2); UV-vis (¾): -max = 315 (17100) and 457 (950). Anal.
Calcd for C30H26Fe: C, 81.45; H, 5.92%. Found: C, 81.43; H,
6.10%.
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6
a) P. Shanmugam, V. Vaithiyanathan, B. Viswambharan, S.
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7
a) O. N. Kadkin, H. Han, Y. G. Galyametdinov, J.
1,4-Dicyclohexenyl-1,3-butadiyne: 32% yield. Pale yellow
needles (hexane); mp: 140-145 °C (dec); EI-MS: m/z 210 and
211 (M+ and M+ + 1) for C16H18; IR (KBr): ¯ = 3026, 2931,
2860, 2199, 2129, 1616, 1434, 1346, 917, and 841; 1H NMR: ¤
6.25-6.23 (2H, m, olefinic-H), 2.13-2.09 (8H, m, CH2), 1.64-
1.61 (4H, m, CH2), and 1.59-1.56 (4H, m, CH2); UV-vis (¾):
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8
a) P. J. Higgins, A. M. Gellett, Bioorg. Med. Chem. Lett.
-
max = 263 (8200), 278 (13600), 295 (18800), and 313
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Financial support by a Grant-in-Aid for Scientific Research
from the Ministry of Education, Culture, Sports, Science and
Technology (Integrated Organic Synthesis; No. 22106512), is
gratefully acknowledged. HH is also grateful to Center of
Instrumental Analyses at University of Toyama for their
supporting measurements of physical properties of the new
compounds.
9
Ethynylferrocene (2) is a stable compound with mp 50-
54 °C, which can be purchased from Sigma-Aldrich (CAS
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118
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
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