Synthesis of the first pentaethynylferrocene derivatives

Article abstract of DOI:10.1016/j.jorganchem.2004.05.006

The synthesis of novel pentaethynylated ferrocene derivatives by a combination of consecutive lithiation and functionalization steps is reported. The repetitive functionalization scheme involves the ortho metalation of a acetal functionalized ferrocene followed by reaction with N-formylpiperidine and alkynylation utilizing a diazophosphonate reagent. Starting from a bisprotected ferrocene-1,2,3-triscarbaldehyde, Ohira-alkynylation and Pd-catalyzed protection of the free alkyne with 4-iodotoluene leads to a ferrocene in which one Cp-ring is 1,2,3-substituted by two acetal rings (1,2-position) and an internal alkyne. Metalation of the ferrocene nucleus with sec-BuLi, workup with DMF and reduction with LiAlH₄ leads to a 1,2,3,4-tetrasubstituted ferrocene carrying a hydroxymethyl group. The acetal groups are removed by para-toluenesulfonic acid and the aldehyde groups are converted into arylalkynes. A second metalation followed by workup with DMF furnishes a 1,2,3,4,5-pentasubstituted ferrocenecarbaldehyde. The aldehyde is transformed into an alkyne by the Ohira method and converted to an internal alkyne by Pd-catalyzed reaction with 4-iodotoluene. The sequence gives a 1,2,3,4,5-pentasubstituted ferrocene derivative with four alkyne groups and one hydroxymethyl group. Airless Marko oxidation of the alcohol is followed by another Ohira alkynylation. Pd-catalyzed arylation finishes the reaction sequence to give the symmetrical 1,2,3,4,5-pentakis(4′-tolylethynyl) ferrocene, the first pentaethynylferrocene derivative. A second, similar route was explored that furnished 1,2,3,4,5-pentakis(4′-butylphenylethynyl) ferrocene and its butadiyne-bridged dimer.

Full text of DOI:10.1016/j.jorganchem.2004.05.006

Journal of Organometallic Chemistry 689 (2004) 4345–4356
www.elsevier.com/locate/jorganchem
Synthesis of the first pentaethynylferrocene derivatives
b
Winfried Steffen , Matthew Laskoski , Jason G.M. Morton , Uwe H.F. Bunz
b
b
a,
*
a
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA
b
USC NanoCenter, University of South Carolina, Columbia, SC 29208, USA
Received 4 May 2004; accepted 4 May 2004
Available online 2 July 2004
Abstract
Starting from a bisprotected ferrocene-1,2,3-triscarbaldehyde, Ohira-alkynylation and Pd-catalyzed protection of the free alkyne
with 4-iodotoluene leads to a ferrocene in which one Cp-ring is 1,2,3-substituted by two acetal rings (1,2-position) and an internal
alkyne. Metalation of the ferrocene nucleus with sec-BuLi, workup with DMF and reduction with LiAlH4 leads to a 1,2,3,4-tetra-
substituted ferrocene carrying a hydroxymethyl group. The acetal groups are removed by para-toluenesulfonic acid and the aldehyde
groups are converted into arylalkynes. A second metalation followed by workup with DMF furnishes a 1,2,3,4,5-pentasubstituted
ferrocenecarbaldehyde. The aldehyde is transformed into an alkyne by the Ohira method and converted to an internal alkyne by Pd-
catalyzed reaction with 4-iodotoluene. The sequence gives a 1,2,3,4,5-pentasubstituted ferrocene derivative with four alkyne groups
and one hydroxymethyl group. Airless Marko oxidation of the alcohol is followed by another Ohira alkynylation. Pd-catalyzed ary-
lation finishes the reaction sequence to give the symmetrical 1,2,3,4,5-pentakis(40-tolylethynyl)ferrocene, the first pentaethynylferro-
cene derivative. A second, similar route was explored that furnished 1,2,3,4,5-pentakis(40-butylphenylethynyl)ferrocene and its
butadiyne-bridged dimer.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Alkynes; Ferrocenes; Palladium-catalyzed couplings; Peralkynylation
1. Introduction and historical perspective
Rayleigh in 1911 [a]. Nowadays breath figures attract
great attention as flexible templates to make nano- and
microstructured solid state materials [b,c,d,e,f,g]. Con-
trary to Physics, research in Chemistry has generated
scientific questions that only could be asked by the pro-
gress Chemistry itself had generated. Such questions
could not have been asked before synthetic and method-
ological ground work had been done. A general example
is the synthesis of natural products [3]. Many natural
products that have been synthesized recently were either
simply not known or if they were known their synthesis
was impossible due to the lack of specific methodologies
to construct their molecular framework. A classic exam-
ple are the enediyne antibiotics [3]. Spectacular scientific
results in chemical research generated in the past are as-
similated and utilized as routine and standard methods in
fields that are removed from its original context, almost
In this contribution, we describe the synthesis of two
derivatives of 1,2,3,4,5-pentaethynylferrocene. Starting
from a partially protected ferrocene-1,2,3-trialdehyde
(1) [1], a series of metalation, carbonylation, and alkyny-
lation steps furnish the targets in a step-wise manner
through a ‘‘merry-go-round’’ substitution process on
one Cp-ring of the ferrocene nucleus.
In Mathematics and Physics, classic questions origi-
nating in the 18th, 19th or early 20th century, remain
highly topical today. A nice example is breath figures,
the fog that settles on a cold mirror when water vapor
condenses. Breath figures were first described by Lord
*
Corresponding author. Tel./fax: +1-404-385-1795.
E-mail address: uwe.bunz@chemistry.gatech.edu (U.H.F. Bunz).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.05.006

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W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
in a sense that chemistry develops as a hierarchical com-
bination of freestanding modules. Consequently, the
time frame of chemical history necessary one has to
know to successfully operate a research group, goes
back less than 20 years, and cited papers may reach back
one to two decades. By the same token, elegant contri-
butions published 40 or 50 years ago, are either irrele-
vant today or have been incorporated into the
textbooks as general paradigms, but do not tend to
aid in the understanding of topical questions in current
chemistry. There are exceptions, such as the discovery
of ferrocene and its functionalization [4] to mention only
one here. An example for the removal of a concept from
its original context into a new one, in the field of carbon-
rich organometallic chemistry, is the independent dis-
covery of Heck, Cassar, Sonogashira, and Hagihara
(HCS) that terminal alkynes couple to aromatic bro-
mides and iodides in the presence of (Ph3P)2PdCl2,
CuI and amines [5]. The HCS coupling is general and
has opened up the field of carbon-rich and carbon-rich
organometallic chemistry [6–19]. Originally designed to
make monoalkynylated benzenes, it allows the connec-
tion between alkynes and arenes into complex carbon-
rich objects [20–26].
do generally not work well in this coupling but those are
of course amenable to the regular HCS coupling [15].
These developments were in place when Kra¨tschmer
and Kroto [16] isolated C60 – Buckminsterfullerene – im-
pacting and exposing carbon-rich species and their orga-
nometallic complexes as an increasingly attractive field
for synthetic chemists. Diederich reported in 1991 [17],
soon afterwards, the first organometallic complex of a
cyclocarbon species. This contribution further fuelled
the interest in carbon-rich organometallics. In 1993–
1994 then a series of peralkynylated and perbutadiyny-
lated cyclobutadiene and cymantrene complexes
were synthesized by Bunz et al. [18] utilizing the Stille–
Losterzo protocol. Since then carbon-rich organometal-
lics is an established field and several reviews and two
JOMC special issues have covered this area. An exten-
sive review in this journal in 2003 reports recent devel-
opments in the field of highly alkynylated p-complexes
[19]. Peralkynylated p-perimeters have already found
use as precursors to cyclohexatrienes, carbon-rich
nano-objects, high carbon content materials, liquid crys-
tals, and NLO-active oligomers [20–26].
Due to great interest, the field of carbon-rich organo-
metallics [27–34] has been the subject of several confer-
ences and symposia. With powerful synthetic methods
available, abundant exciting targets and opportunities
present, alkynylated p-complexes and carbon-rich or-
ganometallics will play an exciting role in materials sci-
ence and conjugated materials. Highly alkynylated
ferrocenes are uncharted waters for the time being – that
despite the importance of the iron sandwich and the suc-
cessful syntheses of 1,10-diethynylferrocenes by Schlo¨gl
et al. and other groups [10,15,33].
Carbon-rich organometallics is a vibrant sub-field of
organometallic chemistry. It combines the elements of
classic acetylene chemistry with that of either the p-
complexes such as ferrocene, cymantrene and cyclobut-
adiene complexes, or the chemistry of acetylides, such as
the ones popularized by Gladysz and coworkers [6], Ro-
senthal in Rostock [7], the Rennes groups around Dix-
neuf and Lapinte [8] as well as YamÕs [9] group in
Hong Kong.
This historical perspective however is restricted to
alkynylated p-complexes and their short history. The
field emanated from roots that go back to Schlo¨glÕs re-
port of the synthesis of ethynylferrocene in 1963 [10].
However, this compound was regarded as laboratory
curiosity and for a long time there were no further devel-
opments. Only in 1979 and 1982 Vollhardt reported the
spectacular Bergman rearrangement of (1,2-diethynylcy-
clobutadiene)(cyclopentadienyl)cobalt complexes. This
complex and its 1,3-isomer were synthesized [11] by an
elegant cobalt mediated [2+2] cycloaddition strategy
[12]. However, their chemistry lay dormant until their
incorporation into conjugated organometallic polymers
was reported in 1995 [13]. While the HCS coupling is
known since 1975, it is not well suited for the attachment
of alkynes to carbonyl substituted p-complexes such as
cymantrene (cyclopentadienylmanganese tricarbonyl).
Stille and Losterzo [14], however, discovered that stan-
nylated alkynes couple smoothly to iodocymantrene in
the presence of (CH3CN)2PdCl2 in DMF. This variant
of the Stille coupling offers a fairly general access to alk-
ynylated p-complexes as long as the corresponding orga-
nometallic iodides are sterically unhindered. Ferrocenes
There have been several unsuccessful attempts at
making peralkynylated ferrocenes, ruthenocenes and cy-
clopentadienylcobalt complexes (Scheme 1). These at-
tempts highlight two concepts on how to approach
organometallic target molecules. In the first case, Rubin
et al. [34] reacted a lithiated pentaethynylcyclopentadi-
ene with FeCl2. Unfortunately, outer sphere electron
transfer took place, and the cyclopentadienyl-anion
was oxidized to its radical while FeCl2 was reduced to
iron. The preferred electron transfer is probably due to
the great steric bulk of the pentakis(triisopropylsilyl)
protected pentaethynylcyclopentadienyl-anion. Smaller
substituents leave the pentaethynylcylcopentadiene un-
stable, making access to decaethynylferrocene and related
ferrocenes difficult via this route.
The second concept utilizes the alkynylation of a pre-
formed sandwich complex. Michl and coworkers [35]
and Winter and coworkers [36] have reported several
promising pentaiodocyclopentadienyl complexes for this
approach. We attempted their alkynylation via the
Heck–Cassar–Sonogashira–Hagihara reaction, [5] but
even under forcing reaction conditions the starting ma-
terials were re-isolated. The high steric hindrance of

W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
4347
R
R
H3C
H3C
CH3
Ph
Ph
Ph
L2PdCl2
CuI
L2PdCl2
CuI
CH3
Ph
FeCl2
H3C
Ru
Co
I
x
x
x
I
I
I
I
R
R
R
I
R
I
I
I
L = PPh3
I
R
Scheme 1. Attempted syntheses of peralkynylated sandwich complexes.
H3C
CH3
the ‘‘second deck’’ on the opposing side (tetraphenylcy-
clobutadiene and pentamethylcyclopentadienyl) shuts
down the reactivity of the sp2-bound iodides (Scheme 1).
In light of the aforementioned results, we have pre-
pared pentaethynylferrocene derivatives by a step-wise
approach that works well under increased steric duress.
Fire-and-sword metalations utilizing butyllithium were
followed by robust functional group transformations.
H3C
FeCp
(PPh3)2PdCl2,
piperidine, CuI
i. p-TsOH
FeCp
6a
ii. 2, MeOH,
K2CO3
4a
CH3
OH
8, 97%
7, 65%
HO
Scheme 3. Synthesis of a trialkynylated ferrocene derivative.
2. Results
yield. Pd-catalyzed reaction of 7 with 4a furnished 8
(97%). The reaction sequence continued with the lithia-
tion of 8. The formed organolithium compound was re-
acted with DMF (Scheme 4) to deliver the aldehyde 9 in
40% yield. Ohira alkynylation [24] transformed 9 into
the free alkyne 10 in 75% yield. The reaction was not
hampered by the presence of the hydroxymethyl group.
The free alkyne was capped by the Pd-catalyzed reaction
of 10 with 4a to form 11a in 94% yield. The alcohol 11a
was oxidized by the airless Marko reaction utilizing
Cu2Cl2 in the presence of phenanthroline and di-tert-
butylazodicarboxylate on solid K2CO3 support [38]. A
final Ohira alkynylation furnished the pentaethynylfer-
rocene derivative 12a in 62% yield. To obtain a symmet-
rical substitution pattern around the ferrocene ring
The aldehyde 1 [1] was transformed by the Ohira-
method [37], utilizing the diazophosphonate 2 to give
the alkynylated ferrocene 3 (Scheme 2). Employing Pd-
catalysis, the alkyne 3 was coupled to 4a and 4b to fur-
nish the ferrocenes 5a and 5b. Both of these could be
metalated by sec-butyllithium to afford the carbinols
6a and 6b in one pot after quenching with N,N-dimeth-
ylformamide or N-formylpiperidine (NFP) and subse-
quent reduction with LiAlH4. The alcohols 6 were the
last common intermediates in the two routes explored
to synthesize pentaethynyl-ferrocene derivatives 12–14.
The bisketal 6a (R=CH3, Schemes 2 and 3) was de-
protected by para-toluenesulfonic acid (TsOH). The re-
sulting (unstable) dialdehyde was not characterized but
immediately reacted with 2 to give the diyne 7 in 65%
O
O
P
OMe
OMe
R
I
O
O
O
O
H3C
(2)
O
O
4a R = CH3,
b R = Bu
O
O
N2
O
(PPh3)2PdCl2,
piperidine, CuI
K2CO3, MeOH
FeCp
FeCp
3, 86%
1
O
O
O
O
O
i. sec-BuLi
O
HO
O
O
(a) DMF
(b) NFP
ii. LiAlH4
FeCp
R
FeCp
5a, 99%
b, 76%
R
6a, 79%
b, 61%
Scheme 2. Synthesis of tetrasubstituted ferrocenes by the lithiation/formylation/alkynylation protocol.

4348
W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
H3C
CH3
While this reaction sequence worked satisfactorily for
the introduction of the five alkyne groups, the question
arose whether it would be better to deprotect the two ac-
etal groups in the later stages of the synthesis. With this
in mind, lithiation of 6b was followed by reaction with
NFP (Scheme 6). The aldehyde 15 was isolated in 48%
yield, along with unreacted 6b which proved difficult
to remove by column chromatography. The mixture
was alkynylated and coupled to 4b, yielding 17. Depro-
tection of the ketals gave 18, which was separable from
19 by column chromatography. Subsequent Ohira alky-
nylation (Scheme 7) afforded the critical intermediate 20
in 22% yield, which was arylated to 11b in 54% yield by
4b in a Pd-catalyzed reaction. Marko oxidation and Oh-
ira alkynylation transformed 11b into 12b. When 12b
H3C
CH3
(PPh3)2PdCl2,
2, MeOH,
CuI, 4a
sec-BuLi,
FeCp
FeCp
8
K2CO3
DMF
amine
CH3
OH
OH
9, 40%
CH3
O
10, 75%
H3C
H3C
CH3
CH3
i. Marko
oxidation
FeCp
FeCp
ii. 2, MeOH,
K2CO3
HO
CH3
O
O
O
CH3
O
O
O
O
2, K2CO3
11a, 94%
12a, 62%
i. BuLi
ii. NFP
H3C
O
H3C
6b
MeOH
Scheme 4. Synthesis of a pentaalkynylated ferrocene derivative.
FeCp
16, 48%
HO
Bu
Bu
OH
O
FeCp
(Scheme 5), the terminal alkyne group in 12a was
capped via an additional Sonogashira reaction. The
symmetrical ferrocene derivative 13a was isolated in
93% yield as the sole product.
15, 48%
O
O
O
O
O
(PPh3)2PdCl2
piperidine, CuI
O
p-TsOH
R
R
OH
FeCp
Bu
4b
OH
FeCp
R
R
CpFe
CpFe
Bu
(PPh3)2PdCl2
CuI/amine
17, 60%
18, 47%
Bu
R
Bu
I
R
O
4
O
R
HO
R
+
FeCp
side product, 19
Bu
13a 93%
b 34%
12a
R
R
b
R
R
Scheme 6. Synthesis of
carrying butyl groups.
a
pentaethynylated ferrocene derivative
R
R
Bu
Bu
CpFe
FeCp
OH
i. Marko
(PPh3)2PdCl2
piperidine, CuI
2, K2CO3
oxidation
R
R
MeOH
12b,
18
63%
ii. 2, MeOH,
OH
4b
K2CO3
FeCp
CpFe
R
R
Bu
14a 0%
b 60%
Bu
Bu
20, 22%
11b, 54%
Bu
Scheme 5. Synthesis of a pentaalkynylated ferrocene derivative and its
dimer.
Scheme 7. Synthesis of a pentaethynylated ferrocene.

W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
4349
was treated under the conditions of the Sonogashira
coupling, 13b was formed, but only in 34% yield. This
was surprising, as the analog, 13a, was isolated in almost
quantitative yield. Further elution of the column led to a
second compound, identified – according to its spectro-
scopic properties – as the formally dehydrogenated di-
mer of 12b (Scheme 5). This unusual dimer, 14b, was
the main product and had formed in 60% yield.
rather than alkynes, 6b was metalated with BuLi and
quenched with NFP to furnish an inseparable mixture
containing 6b and 15. From NMR integration we could
estimate the yield of the metalation to be 48%. The re-
sult suggests that metalation in the presence of the ketal
groups is only marginally better. The mixture was car-
ried through to the stage where 18 and 19 were formed
by cleavage of the ketals. Clean separation of 18 and 19
was achieved by column chromatography. The remain-
ing steps were similar to the synthesis of 12a, but the
double Ohira alkynylation of 20 did not work as well
as the transformation of 6afi7, making the second se-
quence overall less appealing than the first one.
3. Discussion
The introduction of five contiguous alkyne groups on
one cyclopentadienyl ring [30j] of ferrocene was execut-
ed by a stepwise metalation/functionalization strategy.
The challenge was the presence of the second cyclopen-
tadienyl ring in ferrocene and its inadvertent metalation
under the employed reaction conditions. To avoid the
metalation of the second ring, the substituents placed
on the first ring had to: (a) direct the metalation into
the adjacent position and (b) be easily convertible into
alkynes. This combination made ketalized aldehydes
and/or free hydroxymethyl groups the ortho-directing
groups of choice. Acetals [39] have been reported useful
in ortho-lithiation schemes, and Szeimies and coworkers
[40] and Seebach and coworkers [41] have demonstrated
that hydroxymethylgroups can be utilized in this regard.
Both functional groups are used less than benzamides or
oxazolines [42] due to their inferior activating power. In
our study, this is not a problem since ferrocene itself can
be metalated [43]. Here, the ketal and hydroxymethyl
groups were used only for ortho-directing purposes.
Metalation of 5a and 5b, workup with DMF or NFP,
and one-pot reduction worked well and furnished 6a
and 6b in good yields. While the position of the hydrox-
ymethyl group on the ring cannot be attributed beyond
any doubt, spectroscopic data and chemical principles
suggest the structure we propose, where the hydroxym-
ethyl group is adjacent to the ketal groups. Metalation
of the second ring was not observed in this specific case.
For the (problematic) introduction of the 5th substi-
tuent, we utilized two different approaches. In the first
approach (Schemes 3 and 4; R=Me), deketalization
was followed by Ohira alkynylation and protection of
the free alkyne to give 8 in a 63% overall yield. Metala-
tion of 8 furnished the aldehyde 9 in a yield of only 40%.
Side products were species resulting from the deprotona-
tion of the lower ring or from double deprotonation of
both rings. We speculate that the increased steric pres-
sure deactivated the last proton on the ring, making
the 5th deprotonation difficult. Once the last substituent
was in position, functional group transformations
worked well and furnished 12a and 13a without further
problems.
In the last step, the free alkyne of 12b was coupled to
4-butyliodobenzene (4b) in a Pd-catalyzed reaction of the
Sonogashira type (Scheme 5). Contrary to the case of
12a, we isolated only a 34% yield of 13b. The main prod-
uct was the dimer 14b, formed in 60% yield. This dimer
1
was characterized by H NMR and 13C NMR spectros-
copies, with the analytical data supporting our structural
hypothesis. The formation of 14b can be explained by ox-
idative dimerization of 12b during the Sonogashira cou-
pling, arising via the adventitious presence of oxygen or
any other oxidant. Such dimerizations are commonly ob-
served (to a varying degree) in Pd-catalyzed couplings,
but are usually minor side reactions [44].
4. Conclusions
A series of novel alkynylated ferrocenes has been re-
ported. We have demonstrated that by a combination of
metalation, formylation, and alkynylation, all five posi-
tions in one Cp ring of a ferrocene can be replaced by
alkyne groups. In one case, we obtained the but-
adiyne-bridged dimeric decaethynylbiferrocene, 14b.
The pentaalkynylated ferrocenes 13a and 13b are stable
and can be stored indefinitely. In the future, we will re-
port upon the use of the partially alkynylated and fully
alkynylated ferrocenes as modules for the construction
of novel carbon-rich organometallic nanostructures.
5. Experimental
5.1. General
THF was freshly distilled from potassium and benzo-
phenone. All other reagents were of commercial grade
and used as obtained. Reactions employing Schlenk
1
flasks were performed under inert atmosphere. H and
13C NMR spectra were recorded in CDCl3 on a Bruker
AM 300 or a Varian Mercury 400 spectrometer. The
mass spectra were measured on a VG 70SQ. IR spectra
were obtained using a Perkin–Elmer FTIR 1600 on
NaCl plates.
To investigate if the 5th metalation would be easier
performed in the presence of the original ketal groups

4350
W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
5.2. Synthesis of 3
65.37, 45.9, 25.58, 25.41, 21.06. MS (70 eV, EI): m/z
Calc. For M+ (C27H28FeO4) 472.13, Found 472.1.
ꢀ1), 298
In a 100 mL oven-dried Schlenk flask, 1 (4.09 g, 10.6
mmol) and finely powdered K2CO3 (4.69 g, 33.9 mmol)
were dissolved/suspended in dry methanol (8 mL) and
dry THF (3 mL). The flask was cooled to ꢀ10 ꢁC and
dimethyl(azo-2-oxopropyl)phosphonate (2) (4.07 g,
21.2 mmol) was added drop-wise. The reaction mixture
was stirred for 8 h under exclusion of light. NaH-
CO3(aq) was added and the mixture was extracted with
ethylether (200 mL). The combined organic layers were
dried over magnesium sulfate and the solvent was re-
moved in vacuo. Column chromatography (SiO2; hex-
anes/CH2Cl2 4:1+10% NEt3) furnished 3 (3.48 g, 86%)
as a yellow crystalline solid: m.p.: 87 ꢁC. IR (Neat): m
UV–Vis (CHCl3): k 256 (e=6536 cmꢀ1
M
(e=5524 cmꢀ1 Mꢀ1), 318 (e=496 cmꢀ1 Mꢀ1). Elemental
Analysis. Calc. (in %): C 68.65; H 5.97, Found: C 68.71,
H 5.91. 5b: m.p.: 78 ꢁC. IR (Neat): m 2954, 2851, 1459,
1
1235, 1113, 997 cmꢀ1. H NMR (300 MHz, CDCl3): d
3
7.37 (d, JH,H =8.24 Hz, 2H), 7.14 (d, JH,H =8.24 Hz,
3
3
2H), 5.75 (s, 1H), 5.58 (s, 1H), 4.45 (d, JH,H =2.47
3
Hz, 1H), 4.41 (d, JH,H =2.47 Hz, 1H), 4.32–4.01 (m,
4H), 4.22 (s, 5H), 3.99–3.84 (m, 4H), 2.59 (t,
3JH,H =7.69 Hz, 2H), 2.18–2.05 (m, 2H), 1.62–1.52 (m,
2H), 1.41–1.24 (m, 4H), 0.96–0.81 (m, 3H). 13C NMR
(75 MHz, CDCl3): d 142.64, 131.23, 128.32, 121.21,
100.49, 99.35, 87.81, 86.05, 85.07, 85.05, 71.62, 70.35,
67.56, 67.50, 67.40, 67.26, 66.84, 65.84, 35.51, 33.39,
25.99, 25.80, 22.21, 13.88. MS (70 eV, EI): m/z (%) Calc.
For M+ (C30H34FeO4) 514.18, Found 514 (100).
3249, 2960, 2846, 1235, 1104, 993 cmꢀ1. H NMR (300
1
MHz, CDCl3): d 5.70 (s, 1H, acetal-CH), 5.51 (s, 1H, ac-
etal-CH), 4.41 (d, 1H, 3JH,H =2.7 Hz, sub. Cp ring), 4.37
3
(d, 1H, JH,H =2.7 Hz, sub. Cp ring), 4.30–4.10 (m, 4H,
acetal-CH2), 4.20 (s, 5H, Cp-H), 4.00–3.81 (m, 4H, ace-
tal-CH2), 2.78 (s, 1H, alkyne-H), 2.14–2.06 (m, 2H, ace-
tal-CH2), 1.39–1.30 (m, 2H, acetal-CH2). 13C NMR (75
MHz, CDCl3): d 99.40, 98.46, 84.85, 84.57, 80.43, 75.49,
71.10, 70.15, 66.85, 66.75, 66.65, 66.53, 66.31, 63.49,
25.25, 25.14. MS (70 eV, EI): m/z Calc. For M+
(C20H22FeO4) 382.09, Found 382. UV–Vis (CHCl3): k
5.4. Synthesis of 6a
In an oven-dried 500 mL Schlenk flask, 5a (3.93 g,
8.32 mmol) was dissolved in dry THF (150 mL). The so-
lution was cooled to ꢀ78 ꢁC for 10 min and sec-BuLi
(7.0 mL, 1.30 M, 9.1 mmol) was added. The solution be-
came dark-brown and cloudy after 5 min. After 20 min,
the temperature was raised to ꢀ10 ꢁC for 1.5 h. The
reaction mixture was re-cooled to ꢀ78 ꢁC and N,N-
dimethylformamide (0.85 mL, 11 mmol) was added. A
brown precipitate homogenized after 1 h stirring at am-
bient temperature. The addition of brine turned the col-
or of the solution to deep red. The organic layer was
extracted with CH2Cl2, dried over magnesium sulfate,
and the solvent was removed in vacuo under the exclu-
sion of light. The raw product was dissolved under inert
conditions in dry THF (100 mL) and cooled to 0 ꢁC. Ad-
dition of LiAlH4 (10.8 mL, 1.00 M in THF, 10.8 mmol)
changed the color of the solution from red to yellow.
Stirring was continued for another 10 min. The reaction
mixture was quenched with brine and extracted with
CH2Cl2. The combined organic layers were dried over
magnesium sulfate and the solvent was removed in vac-
uo. Column chromatography (SiO2; hexanes/CH2Cl2
2.5:1+10% NEt3) furnished 6a (3.31 g, 79%) in the sec-
ond fraction as a yellow foam. IR (Neat): m 3480 (bd-
244 (e=6552 cmꢀ1
M M
ꢀ1), 316 (e=1284 cmꢀ1 ꢀ1), 443
(e=202 cmꢀ1 ꢀ1). Elemental Analysis. Calc. (in %):
C 62.85; H 5.80, Found: C 62.81, H 5.74.
M
5.3. Synthesis of 5a and 5b
In a 100 mL Schlenk flask, 3 (3.23 g, 8.45 mmol) was
dissolved in dry piperidine (5 mL). To the solution was
added (PPh3)2PdCl2 (3.6 mg, 5.1 lmol), CuI (2.4 mg, 13
lmol) and 4-iodotoluene (4a) (2.20 g, 10.1 mmol) or 4-
iodobutylbenzene (4b) (2.64 g, 10.1 mmol). The reaction
mixture was stirred at ambient temperature for 4 h.
Water was added and the mixture was extracted with
ethylether (150 mL). The combined organic layers were
dried over magnesium sulfate and the solvent was re-
moved in vacuo. Column chromatography (SiO2; hex-
anes/CH2Cl2 4:1+10% NEt3) furnished 5a (3.93 g,
99%) or 5b (3.31 g, 76%) as orange solids. 5a: m.p.:
139 ꢁC. IR (Neat): m 2970, 2852, 2208, 1548, 1236,
1
1
1087, 819 cmꢀ1. H NMR (300 MHz, CDCl3): d 7.35
OH), 2964, 2850, 1544, 1373, 1112, 997, 817 cmꢀ1. H
3
(d, 2H, JH,H =8.2 Hz, aromatic-H), 7.10 (d, 2H,
3
NMR (300 MHz, CDCl3): d 7.37 (d, 2H, JH,H =8.4
Hz, aromatic-H), 7.11 (d, 2H, JH,H =8.4 Hz, aromat-
ic-H), 5.90 (s, 1H, acetal-CH), 5.54 (s, 1H, acetal-CH),
3JH,H =8.2 Hz, aromatic-H), 5.76 (s, 1H, acetal-CH),
3
3
5.58 (s, 1H, acetal-CH2), 4.45 (d, 1H, JH,H =2.5 Hz,
3
sub. Cp ring), 4.41 (d, 1H JH,H =2.5 Hz, sub. Cp ring),
2
3
4.64 (dd, 1H, JH,H =11.8 Hz, JH,H =2.5 Hz, alcohol-
CH2), 4.46 (s, 1H, sub. Cp ring), 4.31–4.15 (m, 4H
acetal-CH2, 1H, alcohol-CH2), 4.25 (s, 5H, Cp-H),
4.32–4.01 (m, 4H, acetal-CH2), 4.22 (s, 5H, unsub. Cp-
H), 3.99–3.84 (m, 4H, acetal-CH2), 2.34 (s, 3H, meth-
yl-H), 2.18–2.05 (m, 2H, acetal-CH2), 1.41–1.24 (m,
2H, acetal-CH2). 13C NMR (75 MHz, CDCl3): d
137.16, 130.80, 128.58, 120.62, 100.04, 99.89, 87.38,
85.77, 84.73, 71.25, 69.89, 67.09, 66.95, 66.83, 66.50,
3
4.03–3.85 (m, 4H acetal-CH2), 3.45 (d, 1H, JH,H =4.4
Hz, alcohol-OH), 2.34 (s, 3H, methyl-H), 2.15–2.11 (m,
2H, acetal-CH2), 1.43–1.29 (m, 4H, acetal-CH2). 13C
NMR (75 MHz, CDCl3): d 137.26, 130.71, 128.49,

W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
4351
120.21, 99.89, 99.55, 87.66, 86.67, 85.86, 84.99, 83.26,
71.81, 71.67, 67.21, 63.60, 58.84, 45.65, 25.45, 25.25,
20.93. MS (70 eV, EI): m/z Calc. For M+ (C28H30FeO5)
502.14, Found 502. UV–Vis (CHCl3): k 257 (e=18047
sulfate and the solvent was removed in vacuo to yield
a red solid. In a 100 mL oven-dried Schlenk flask, the
red solid and finely powdered K2CO3 (800 mg, 5.79
mmol) were dissolved/suspended in dry methanol (5
mL) and dry THF (2 mL). The flask was cooled to
ꢀ10 ꢁC and 2 (780 mg, 4.06 mmol) was added drop-
wise. The reaction mixture was stirred for 8 h under
exclusion of light, quenched with NaHCO3(aq), and ex-
tracted with ethylether (200 mL). The combined organic
layers were dried over magnesium sulfate and the sol-
vent was removed in vacuo. Column chromatography
(SiO2; hexanes/CH2Cl2 4:1+10% NEt3) furnished 7
(221 mg, 65%) as a yellow crystalline solid: m.p.: 57
ꢁC. IR (Neat): m 3450 (bd-OH), 2969, 2770, 2212,
cmꢀ1
cmꢀ1
M M
ꢀ1), 302 (e=13725 cmꢀ1 ꢀ1), 446 (e=490
M
ꢀ1). Elemental Analysis. Calc. (in %): C 66.94;
H 6.02, Found: C 66.93, H 6.09.
5.5. Synthesis of 6b
In an oven-dried 500 mL Schlenk flask, 5b (4.68 g,
9.10 mmol) was dissolved in dry THF (250 mL). The so-
lution was cooled to ꢀ78 ꢁC for 10 min and sec-BuLi
(7.7 mL, 1.30 M, 10 mmol) was added. The solution be-
came dark-brown and cloudy after 5 min. After 20 min,
the temperature was raised to ꢀ10 ꢁC for 1.5 h. The re-
action mixture was re-cooled to ꢀ78 ꢁC and N-formylpi-
peridine (1.13 g, 16.0 mmol) was added. A brown
precipitate homogenized after 1 h stirring at ambient
temperature. The addition of brine turned the color of
the solution to deep red. The organic layer was extracted
with CH2Cl2, dried over magnesium sulfate, and the sol-
vent was removed in vacuo under the exclusion of light.
The raw product was dissolved under inert conditions in
dry THF (100 mL) and cooled to 0 ꢁC. Addition of
LiAlH4 (11.8 mL, 1.00 M in THF, 11.8 mmol) changed
the color of the solution from red to yellow. The reac-
tion mixture was quenched with brine and extracted
with CH2Cl2. The combined organic layers were dried
over magnesium sulfate and the solvent was removed
in vacuo. Column chromatography (SiO2; hexanes/
CH2Cl2 4:1+10% NEt3) furnished 6b (3.02 g, 61%) in
the second fraction as a yellow foam. IR (Neat): m
1544, 1299, 999, 815 cmꢀ1
.
1H NMR (300 MHz,
3
CDCl3): d 7.39 (d, 2H, JH,H =8.4 Hz, aromatic-H),
7.12 (d, 2H, JH,H =8.4 Hz, aromatic-H), 4.70 (s, 1H,
3
2
sub. Cp ring), 4.46 (dd, 2H, JH,H =27.7 Hz,
3JH,H =12.4 Hz, alcohol-CH2), 4.29 (s, 5H, Cp-H),
3.13 (s, 1H, alkyne-H), 3.06 (s, 1H, alkyne-H), 2.34 (s,
3H, methyl-H). 13C NMR (75 MHz, CDCl3): d 138.54,
131.81, 129.33, 120.43, 90.49, 89.61, 84.66, 79.47,
79.35, 79.20, 79.17, 74.61, 71.87, 70.44, 69.58, 67.86,
59.19, 21.81. MS (70 eV, EI): m/z Calc. For M+
(C24H18FeO) 378.07, Found 378.
5.7. Synthesis of 8
In a 25 mL Schlenk flask, 7 (388 mg, 1.03 mmol) was
dissolved in dry piperidine (2 mL). To the solution was
added (PPh3)2PdCl2 (1.4 mg, 2.0 lmol), CuI (1.0 mg, 5.3
lmol) and 4a (563 mg, 2.58 mmol). The reaction mixture
was stirred at ambient temperature for 2 h. Water was
added and the mixture was extracted with ethylether
(100 mL). The combined organic layers were dried over
magnesium sulfate and the solvent was removed in vacuo.
Column chromatography (SiO2; hexanes/CH2Cl2
1:4+10% NEt3) furnished 8 (557 mg, 97%) as an orange
solid: m.p.: 180 ꢁC (decomposition). IR (Neat): m 3340
1
2954, 2849, 2212, 1469, 1236, 1106, 994, 818 cmꢀ1. H
3
NMR (300 MHz, CDCl3): d 7.37 (d, JH,H =8.4 Hz,
2H), 7.12 (d, JH,H =8.4 Hz, 2H), 5.90 (s, 1H), 5.54 (s,
3
3
1H), 4.64 (d, JH,H =4.4 Hz, 1H), 4.46 (s, 1H), 4.31–
4.15 (m, 4H), 4.25 (s, 5H), 4.03–3.85 (m, 4H), 3.45 (d,
3
3JH,H =4.4 Hz, 1H), 2.59 (t, JH,H =7.7 Hz, 2H), 2.15–
2.11 (m, 2H), 1.62–1.52 (m, 2H), 1.43–1.29 (m, 4H),
(bd-OH), 2920, 2866, 1950, 1512, 1107, 1002, 814 cmꢀ1
.
3
0.91 (t, JH,H =7.3 Hz. 13C NMR (75 MHz, CDCl3): d
1H NMR (300 MHz, CDCl3): d 7.49–7.41 (m, 8H, aro-
matic-H), 7.16–7.13 (m, 4H, aromatic-H), 4.74 (s, 1H,
sub. Cp ring), 4.61 (s, 5H, Cp-H), 4.53 (dd, 2H,
160.40, 142.47, 130.93, 128.05, 120.63, 100.12, 99.77,
87.90, 86.88, 85.86, 84.99, 83.26, 71.81, 67.41, 67.36,
63.87, 59.04, 45.85, 35.17, 33.07, 25.66, 25.46, 11.27.
MS (70 eV, EI): m/z (%) Calc. For M+ (C31H36FeO5)
544.19, Found 544 (100).
3
2JH,H =32.4 Hz, JH,H =11.5 Hz, alcohol-CH2), 2.36 (s,
9H, methyl-H). 13C NMR (75 MHz, CDCl3): d 138.18,
138.02, 137.95, 131.94, 131.46, 131.40, 131.39, 129.06,
129.00 129.02, 120.77, 120.48, 120.32, 91.32, 91.23,
89.40, 89.14, 85.13, 84.67, 84.01, 74.03, 71.84, 71.14,
68.87, 68.55, 59.45, 21.48. MS (70 eV, EI): m/z Calc. For
M+ (C38H30FeO) 558.16, Found 558. Elemental Analysis.
Calc. (in %): C 81.72; H 5.41, Found: C 81.66, H 5.50.
5.6. Synthesis of 7
To a 100 mL round bottom flask was added 6a (434
mg, 0.864 mmol), p-toluenesulfonic acid (410 mg, 2.16
mmol), THF (3 mL), and H2O (2 mL). The resulting
mixture was stirred for 15 min at ambient temperature
and under exclusion of light. Water was added and the
mixture was extracted with ethylether (100 mL). The
combined organic layers were dried over magnesium
5.8. Synthesis of 9
In an oven-dried 25 mL Schlenk flask, 8 (557 mg, 1.00
mmol) was dissolved in dry THF (10 mL). The solution

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W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
was cooled to ꢀ78 ꢁC for 10 min and sec-BuLi (0.85 mL,
1.30 M, 1.1 mmol) was added. The solution became
dark-brown and cloudy after 5 min. After 20 min, the
temperature was raised to 0 ꢁC for 1 h. The reaction
mixture was re-cooled to ꢀ78 ꢁC and DMF (0.08 mL,
1 mmol) was added under exclusion of light. A brown
precipitate homogenized after 1 h stirring at ambient
temperature. The reaction mixture was quenched with
brine and extracted with ethylether (125 mL). The com-
bined organic layers were dried over magnesium sulfate
and the solvent was removed in vacuo. Column chroma-
tography (SiO2; hexanes/CH2Cl2 2.5:1+10% NEt3) fur-
nished 9 (233 mg, 40%) in the second fraction as a
dark red oil. IR (Neat): m (cmꢀ1) 3418 (bd-OH), 3082,
2920, 2210, 1905, 1662 (C@O), 1512, 1411, 1041, 814.
1H NMR (300 MHz, CDCl3): d 10.32 (s, 1H, ald-H),
7.50–7.44 (m, 6H, aromatic-H), 7.19–7.15 (m, 6H, aro-
was added (PPh3)2PdCl2 (2.2 mg, 3.1 lmol), CuI (1.5
mg, 7.9 lmol) and 4a (50.0 mg, 0.229 mmol). The reac-
tion mixture was stirred at ambient temperatures for 2 h.
Water was added and the mixture was and extracted
with ethyl ether (100 mL). The combined organic layers
were dried over magnesium sulfate and the solvent was
removed in vacuo. Column chromatography (SiO2; hex-
anes/ CH2Cl2 1:4+10% NEt3) furnished 11a (99 mg,
94%) as an orange oil. IR (Neat): m 3280, 2945, 2860,
2188, 1512, 1448, 1105, 813 cmꢀ1 1H NMR (300
.
MHz, CDCl3): d 7.51–7.44 (m, 8H, aromatic-H), 7.15
(d, 8H, JH,H =8.4 Hz, aromatic-H), 4.80 (s, 2H, alco-
3
hol-CH2), 4.36 (s, 5H, Cp-H), 2.37 (s, 12H, methyl-H).
13C NMR (75 MHz, CDCl3): d 138.40, 138.16, 131.55,
131.50, 129.10, 129.06, 120.58, 120.12, 91.68, 89.81,
84.22, 83.52, 75.75, 71.27, 69.21, 58.96, 21.52. Two sig-
nals are missing due to spectral overlap. MS (70 eV,
EI): m/z Calc. For M+ (C47H36FeO) 672.21, Found
2
3
matic-H), 4.72 (dd, 1H, JH,H =10.4 Hz, JH,H =8.9
Hz, alcohol-CH2), 4.44 (s, 5H, Cp-H), 4.24 (dd, 1H,
672. UV–Vis (CHCl3): k 288 (e=14,915 cmꢀ1
M
ꢀ1),
3
2JH,H =8.5 Hz, JH,H =5.8 Hz, alcohol-CH2), 2.37 (s,
384 (e=1177 cmꢀ1 ꢀ1). Elemental Analysis. Calc. (in
%): C 83.92; H 5.39, Found: C 83.18, H 6.06.
M
9H, methyl-H). 13C NMR (75 MHz, CDCl3): d 195.88,
138.49, 138.39, 138.25, 131.24, 131.18, 131.09 128.80,
128.75, 128.73, 119.64, 119.31, 119.26 93.16, 92.75,
92.34, 91.31, 82.62, 81.92, 81.60, 75.30, 75.13, 74.67,
74.29, 72.34, 57.70, 21.13. MS (70 eV, EI): m/z Calc.
For M+ (C39H30FeO2) 586.16, Found 586.
5.11. Synthesis of 12a
In a 25 mL oven-dried Schlenk flask, 11a (99.0 mg,
0.147 mmol), CuCl (3.0 mg, 30 lmol), 1,10-phenanthro-
line (5.0 mg, 28 lmol), and K2CO3 (8.0 mg, 58 lmol)
were dispersed in dry toluene (2 mL). Di-tert-butylazo-
dicarboxylate (40.0 mg, 0.170 mmol) was added under
nitrogen and the reaction was heated to 90 ꢁC for 2 h.
The reaction mixture was filtered over celite with
CH2Cl2 as the mobile phase and the solvent was re-
moved in vacuo. The resulting unstable, dark-red oil
was transferred with CH2Cl2 into a 25 mL Schlenk flask
and the solvent was removed in vacuo. To this was added
K2CO3 (78.0 mg, 0.564 mmol), dry methanol (2 mL) and
dry THF (1 mL) under nitrogen. The solution was
cooled to ꢀ10 ꢁC and 2 (71.0 mg, 0.370 mmol) was
added drop-wise. The resulting reaction mixture was stir-
red for 8 h under exclusion of light. NaHCO3(aq) was
added and the mixture was extracted with ethylether
(200 mL). The combined organic layers were dried over
magnesium sulfate and the solvent was removed in vac-
uo. Column chromatography (SiO2; hexanes/CH2Cl2
2.5:1+10% NEt3) furnished 12a (61 mg, 62%) as a
red-yellow oil. IR (Neat): m 2920, 2858, 2341, 1732,
5.9. Synthesis of 10
In a 25 mL oven-dried Schlenk flask, 9 (128 mg, 0.218
mmol) and finely powdered K2CO3 (100 mg, 0.724
mmol) were dissolved in dry methanol (4 mL) and dry
THF (2 mL). The flask was cooled to ꢀ10 ꢁC and 2
(100 mg, 0.521 mmol) was added drop-wise. The reaction
mixture was stirred for 8 h under exclusion of light.
NaHCO3(aq) was added and the mixture was extracted
with ethylether (200 mL). The combined organic layers
were dried over magnesium sulfate and the solvent was
removed in vacuo. Column chromatography (SiO2; hex-
anes/CH2Cl2 4:1+10% NEt3) furnished 10 (95 mg, 75%)
as a red-yellow oil. IR (Neat): m 3276, 2952, 2854, 1506,
1
1458, 1107, 815 cmꢀ1. H NMR (300 MHz, CDCl3): d
3
7.50–7.42 (m, 6H, aromatic-H), 7.15 (d, 6H, JH,H =8.4
3
Hz, aromatic-H), 4.74 (d, 2H, JH,H =5.5 Hz, alcohol-
CH2), 4.34 (s, 5H, Cp-H), 3.09 (s, 1H, alkyne-H), 2.36
(s, 9H, methyl-H). 13C NMR (75 MHz, CDCl3): d
138.48, 138.29, 138.24, 131.64, 131.55, 131.51, 129.11,
129.06, 129.03, 120.47, 120.36, 120.01, 91.82, 91.76,
90.41, 83.93, 83.67, 93.67, 83.21, 79.35, 78.71, 75.94,
71.70, 71.50, 69.37, 67.25, 58.74, 21.53. MS (70 eV, EI):
m/z Calc. For M+ (C40H30FeO) 582.16, Found 582.
1
1512, 1153, 817 cmꢀ1. H NMR (400 MHz, CDCl3): d
3
7.50 (d, 8H, JH,H =8.4 Hz, aromatic-H), 7.16 (d, 8H,
3JH,H =8.4 Hz, aromatic-H), 4.41 (s, 5H, Cp-H), 3.17
(s, 1H, alkyne-H), 2.37 (s, 12H, methyl-H). 13C NMR
(100 MHz, CDCl3): d 138.36, 138.31, 131.69, 131.61,
129.09, 129.05, 120.46, 120.34, 91.91, 91.86, 83.94,
83.68, 79.23, 79.20, 78.94, 77.22, 71.75, 71.45, 21.57.
MS (70 eV, EI): m/z Calc. For M+ (C48H34Fe) 666.20,
Found 666. UV–Vis (CHCl3): k 292 (e=55,940 cmꢀ1
5.10. Synthesis of 11a
In a 25 mL Schlenk flask, 10 (92.0 mg, 0.158 mmol)
was dissolved in dry piperidine (1 mL). To the solution
M M
ꢀ1), 380 (e=6565 cmꢀ1 ꢀ1).

W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
4353
5.12. Synthesis of 13a
ganic layers were dried over magnesium sulfate and
the solvent was removed in vacuo. Column chromatog-
raphy (SiO2; hexanes/CH2Cl2 4:1+10% NEt3) furnished
16 and 6b (2.35 g crude material, 80%) in a 2/3 ratio as a
yellow oil which was immediately taken to the next step.
In a 25 mL Schlenk flask, 12a (57.0 mg, 85.6 lmol)
was dissolved in dry piperidine (1 mL). To the solution
was added (PPh3)2PdCl2 (1.0 mg, 1.4 lmol), CuI (0.8
mg, 4 lmol) and 4a (24.0 mg, 0.110 mmol). The reaction
mixture was stirred at ambient temperature for 2 h.
Water was added and the mixture was extracted with
ethylether (75 mL). The combined organic layers were
dried over magnesium sulfate and the solvent was re-
moved in vacuo. Column chromatography (SiO2; hex-
anes/CH2Cl2 1:2.5+10% NEt3) furnished 13a (60 mg,
93%) as an orange crystalline solid: m.p.: 152 ꢁC (turned
dark), 168 ꢁC (decomposition). IR (Neat): m 2923, 2858,
5.15. Synthesis of 17
In a 25 mL Schlenk flask, the oil containing 16 and 6b
(2.35 g crude material, 1.90 mmol alkyne) was dissolved
in dry piperidine (3 mL). To the solution was added
(PPh3)2PdCl2 (36.3 mg, 51.9 lmol), CuI (9.9 mg, 52
lmol), and 4b (1.35 g, 5.19 mmol). The reaction mixture
was stirred at ambient temperature for 2 h. Water was
added and the mixture was extracted with ethylether
(125 mL). The combined organic layers were dried over
magnesium sulfate and the solvent was removed i vacuo.
Chromatography (SiO2; hexanes/CH2Cl2 4:1+10%
NEt3) furnished a mixture of 17 and 6b (2.33 g crude
material, 80%) in a 1/3 ratio which was immediately taken
to the next step.
2329, 1712, 1512, 1176, 813 cmꢀ1. H NMR (400 MHz,
1
3
CDCl3): d 7.52 (d, 10H, JH,H =8.4 Hz, aromatic-H),
3
7.17 (d, 10H, JH,H =8.4 Hz, aromatic-H), 4.42 (s, 5H,
Cp-H), 2.38 (s, 15H, methyl-H). 13C NMR (100 MHz,
CDCl3): d 138.23, 131.60, 129.09, 120.57, 91.77, 84.24,
77.11, 71.22, 21.57. MS (70 eV, EI) m/z Calc. For M+
(C55H40Fe) 756.25, Found 756. UV--Vis (CHCl3): k
298 (e=51,208 cmꢀ1 Mꢀ1), 384 (e=5561 cmꢀ1 Mꢀ1). El-
emental Analysis. Calc. (in %): C 87.29; H 5.33,
Found: C 87.41, H 5.90.
5.16. Synthesis of 18 and 19
To a 100 mL round bottom flask was added the oil
containing 17 and 6b (1.40 g), p-toluenesulfonic acid
(951 mg, 5.00 mmol), THF (3 mL) and H2O (5 mL).
The reaction mixture was stirred for 30 min under exclu-
sion of light. Water was added and the mixture was ex-
tracted with ethylether (100 mL). The combined organic
layers were dried over magnesium sulfate and the sol-
vent was removed in vacuo. Column chromatography
(SiO2; hexanes/EtOAc 4:1) furnished 18 (140 mg, 47%)
as a yellow-red oil and 19 (500 mg, 78%) as a red oil.
18: IR (Neat): m 2953, 2856, 1680, 1513, 1412, 831
5.13. Synthesis of 15
In an oven-dried 25 mL Schlenk flask, 6b (2.68 g,
4.92 mmol) was dissolved in dry THF (100 mL). The
solution was cooled to ꢀ78 ꢁC for 10 min and BuLi
(5.4 mL 2.00 M, 11 mmol) was added. The solution
turned dark-brown and cloudy after 5 min. After
20 min, the temperature was raised to 0 ꢁC for 1 h.
The reaction mixture was re-cooled to ꢀ78 ꢁC and
NFP (1.39 g, 12.3 mmol) was added. A brown precipi-
tate homogenized after 1 h stirring at ambient temper-
ature. The reaction mixture was quenched with brine
and extracted with ethylether (200 mL). The combined
organic layers were dried over magnesium sulfate and
the solvent was removed in vacuo. Column chromatog-
raphy (SiO2; hexanes/CH2Cl2 4:1+10% NEt3) furnished
6b and 15 in a 1/1 ratio (2.61 g crude material, 96%) as
a light sensitive, red oil which was immediately taken to
the next step.
1
cmꢀ1. H NMR (400 MHz, CDCl3): d 10.70 (s, 1H),
10.52 (s, 1H), 7.49–7.45 (m, 4H), 7.20–7.17 (m, 4H),
4.76–4.73 (m, 2H), 4.50 (s, 5H), 4.35–4.30 (m, 1H),
2.65–2.60 (m, 4H), 1.65–1.55 (m, 4H), 1.41–1.29 (m,
4H), 0.95–0.90 (m, 6H). 13C NMR (100 MHz, CDCl3):
d 197.35, 193.37, 144.31, 144.21, 131.66, 131.60,
128.59, 128.55, 119.36, 119.29, 96.13, 94.50, 94.36,
81.15, 80.97, 79.01, 78.37, 76.95, 76.57, 75.49, 57.91,
35.56, 33.26, 22.19, 13.84. MS (70 eV, EI): m/z (%) Calc.
For M+ (C37H36FeO3) 584.20, Found 584 (100). 19: IR
5.14. Synthesis of 16
(Neat): m 2960, 2865, 1676, 1414, 1360, 1015, 834 cmꢀ1
.
1H NMR (400 MHz, CDCl3): d 10.71 (s, 1H), 10.47 (s,
1H), 7.39 (d, JH,H =8.3 Hz, 2H), 7.16 (d, JH,H =8.5
3
3
In a 25 mL oven-dried Schlenk flask, the oil contain-
ing 6b and 15 (2.61 g crude material, 2.37 mmol alde-
hyde) and finely powdered K2CO3 (0.850 g, 6.15
mmol) were dissolved/suspended in dry methanol (8
mL) and dry THF (2 mL). The flask was cooled to
ꢀ10 ꢁC and 2 (1.19 g, 6.20 mmol) was added drop-wise.
The reaction mixture was stirred for 8 h under exclusion
of light. NaHCO3(aq) was added and the mixture was
extracted with ethylether (200 mL). The combined or-
3
Hz, 2H), 5.24 (s, 1H), 4.49 (s, 5H), 4.05 (t, JH,H =6.6
3
Hz, 1H), 3.75–3.70 (m, 2H), 2.61 (t, JH,H =7.7 Hz,
2H), 1.61–1.53 (m, 2H), 1.37–1.30 (m, 2H), 0.91 (t,
3JH,H =7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): d
196.95, 193.53, 144.07, 131.34, 128.46, 119.07, 95.88,
91.81, 81.57, 80.06, 79.27, 76.57, 74.40, 73.75, 58.92,
35.40, 33.13, 22.07, 13.74. MS (70 eV, EI): m/z (%) Calc.
For M+ (C25H24FeO3) 428.11, Found 428 (100).

4354
W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
5.17. Synthesis of 20
furnished 21 (22 mg, 88 %) in the second fraction as a
red/yellow oil. IR: m 2908, 1765, 1458, 1370, 1277,
1
In a 25 mL oven-dried Schlenk flask, 18 (140 mg,
0.240 mmol) and finely powdered K2CO3 (166 mg,
1.20 mmol) were dissolved/suspended in dry methanol
(1 mL) and dry THF (1 mL). The solution was cooled
to 0 ꢁC and 2 (232 mg, 1.20 mmol) was added drop-wise.
The reaction mixture was stirred for 8 h under exclusion
of light. NaHCO3(aq) was added and the mixture was
extracted with ethylether (200 mL). The combined or-
ganic layers were dried over magnesium sulfate and
the solvent was removed in vacuo. Column chromatog-
raphy (SiO2; hexanes/EtOAc 4:1) furnished 20 (32 mg,
22%) in the first fraction as a yellow oil. IR (Neat): m
1141, 833 cmꢀ1. H NMR (400 MHz, CDCl3): d 10.47
(s, 1H), 7.55–7.51 (m, 8H), 7.20–7.16 (m, 8H), 4.44 (s,
5H), 2.66–2.60 (m, 8H), 1.64–1.55 (m, 8H), 1.40–1.32
(m, 8H), 0.93–0.91 (m, 12 H). 13C NMR (100 MHz,
CDCl3):
d 192.0, 143.97, 143.94, 132.00, 131.96,
128.80, 128.76, 120.58, 120.52, 93.51, 93.40, 83.35,
83.07, 77.57, 75.88, 71.11, 35.92, 33.67, 22.55, 14.19.
MS (70 eV, EI): m/z (%) Calc. For M+ (C59H58FeO)
838.38, Found 838 (100).
5.20. Synthesis of 12b
3287, 2962, 1734, 1363, 1266, 1094, 834 cmꢀ1
.
1H
In a 25 mL oven-dried Schlenk flask, 21 (10.0 mg,
11.9 lmol) and finely powdered K2CO3 (3.3 mg, 24
lmol) were dissolved in dry methanol (1 mL) and dry
THF (1 mL). The solution was cooled to ꢀ10 ꢁC and
2 (5.3 mg, 28 lmol) was added drop-wise. The reaction
mixture was stirred for 8 h under exclusion of light.
NaHCO3(aq) was added and the mixture was extracted
with ethylether (200 mL). The combined organic layers
were dried over magnesium sulfate and the solvent was
removed in vacuo. Purification by thick layer chroma-
tography with hexanes as the mobile phase furnished
12b (7.0 mg, 70%) in the second fraction as a yellow
NMR (300 MHz, CDCl3): d 7.49–7.43 (m, 4H), 7.16–
7.14 (m, 4H), 4.72 (m, 2H), 4.33 (s, 5H), 3.14 (s, 1H),
3.09 (s, 1H), 2.63–2.59 (m, 4H), 1.60–1.57 (m, 4H),
1.37–1.31 (m, 4H), 0.93–0.90 (m, 6H). 13C NMR (75
MHz, CDCl3):
d 143.64, 143.45, 131.69, 131.57,
128.52, 128.43, 120.44, 120.09, 92.00, 91.94, 90.52,
83.30, 82.87, 79.42, 79.23, 78.59, 78.35, 76.00, 72.10,
69.73, 69.61, 67.75, 58.66, 35.61, 33.41, 33.38, 22.26,
13.91.
5.18. Synthesis of 11b
1
oil. H NMR (400 MHz, CDCl3): d 7.52–7.50 (m, 8H),
7.18–7.15 (m, 8H), 4.39 (s, 5H), 3.15 (s, 1H), 2.62 (t,
In a 25 mL Schlenk flask, 20 (32.0 mg, 55.5 lmol) was
dissolved in dry piperidine (2 mL). To the solution was
added (PPh3)2PdCl2 (1.9 mg, 2.7 lmol), CuI (0.5 mg, 3
lmol), and 4b (33.0 mg, 0.127 mmol). The reaction mix-
ture was stirred at ambient temperature for 8 h. Water
was added and the mixture was extracted with ethylether
(100 mL). The combined organic layers were dried over
magnesium sulfate and the solvent was removed in vacuo.
Column chromatography (SiO2; hexanes/ EtOAc 4:1)
furnished 11b (25 mg, 54%) in the first fraction as a yel-
3JH,H =7.7 Hz, 8H), 1.64–1.57 (m, 8H), 1.38–1.33 (m,
3
8H), 0.93 (d, JH,H =7.4 Hz, 12H). 13C NMR (100
MHz, CDCl3):
d 143.38, 143.33, 131.73, 131.65,
128.47, 128.43, 120.69, 120.58, 91.95, 91.90, 83.96,
83.71, 79.21, 79.16, 78.95, 77.23, 71.78, 71.49, 35.65,
33.43, 22.30, 13.94.
5.21. Synthesis of 13b and 14b
1
low oil. H NMR (300 MHz, CDCl3): d 7.53–7.46 (m,
In a 25 mL Schlenk flask, 12b (35.0 mg, 42.0 lmol)
was dissolved in dry piperidine (2 mL). To the solu-
tion was added (PPh3)2PdCl2 (1.5 mg, 2.1 lmol),
CuI (0.5 mg, 3 lmol), and 4b (16.4 mg, 63.0 lmol).
The reaction mixture was stirred at ambient tempera-
ture for 6 h. Water was added and the mixture was
extracted with ethylether (100 mL). The combined or-
ganic layers were dried over magnesium sulfate and
the solvent was removed in vacuo. Column chroma-
tography (SiO2; hexanes/CH2Cl2 16:1) furnished 13b
(14 mg, 34%) in the first fraction and 14b (21 mg,
60%) in the second fraction as yellow, crystalline ma-
8H), 7.17–7.15 (m, 8H), 4.80 (bs, 2H), 4.34 (s, 5H),
2.64–2.59 (m, 8H), 1.63–1.55 (m, 8H), 1.39–1.32 (m,
8H), 0.95–0.90 (m, 12H). 13C NMR (75 MHz, CDCl3):
d 143.47, 143.21, 131.62, 131.56, 128.51, 120.84,
120.36, 91.77, 89.87, 84.22, 83.53, 75.79, 71.34, 69.21,
59.06, 35.64, 33.43, 33.41, 22.29, 13.93.
5.19. Synthesis of 21 via an airless Marko oxidation
In a 25 mL oven-dried Schlenk flask, 11b (25.0 mg,
29.7 lmol), Cu2Cl2 (0.4 mg, 2 lmol), 1,10-phenanthro-
line (0.6 mg, 3 lmol), and K2CO3 (1 mg, 7 lmol) were
dispersed in dry toluene (5 mL). Di-tert-butylazodicarb-
oxylate (15.0 mg, 0.714 mmol) was added under nitro-
gen and the reaction was heated to 90 ꢁC for 2 h. The
reaction mixture was filtered over Celite with CH2Cl2
as the mobile phase and the solvent was removed in vac-
uo. Column chromotagraphy (SiO2; hexanes/EtOAc 5:1)
1
terials. 13b: H NMR (400 MHz, CDCl3): d 7.51 (d,
3
3JH,H =7.96 Hz, 10H), 7.16 (d, JH,H =7.95 Hz,
3
10H), 4.39 (s, 5H), 2.62 (t, JH,H =7.7 Hz, 10H),
1.65–1.55 (m, 10H), 1.39–1.29 (m, 10H), 0.96–0.86
(m, 15H). 13C NMR (100 MHz, CDCl3): d 142.56,
130.21, 124.23, 120.70, 91.33, 83.51, 75.98, 71.16,
34.95, 34.13, 24.76, 11.98. MS (70 eV, IE): m/z Calc.

W. Steffen et al. / Journal of Organometallic Chemistry 689 (2004) 4345–4356
4355
For M+ (C70H70Fe) 966.18, Found 966.). Elemental
Analysis. Calc. (in %): C 86.93; H 7.30, Found: C
86.51, H 7.52. 14b: 1H NMR (400 MHz, CDCl3): d
7.56–7.51 (m, 16H), 7.19–7.09 (m, 16H), 4.47 (s,
5H), 2.65–2.54 (m, 16H), 1.66–1.50 (m, 16H), 1.40–
1.24 (m, 16H), 0.95–0.84 (m, 24H). 13C NMR (100
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