Copper(I)-catalyzed synthesis of ferrocenyl aryl ethers

Article abstract of DOI:10.1021/om0497893

Ferrocenyl aryl ether can be synthesized in good yields by CuI/2,2,6,6-tetramethylheptane-3,5-dione (TMHD)-catalyzed coupling reactions from iodoferrocene or 1,1′-diiodoferrocene and various phenols in NMP solvent using Cs₂CO₃ or K

Full text of DOI:10.1021/om0497893

3548
Organometallics 2004, 23, 3548-3551
Notes
Cop p er (I)-Ca ta lyzed Syn th esis of F er r ocen yl Ar yl Eth er s
Markus R. an der Heiden, Guido D. Frey, and Herbert Plenio*
Institut fu¨r Anorganische Chemie, TU Darmstadt, Petersenstr. 18,
64287 Darmstadt, Germany
Received March 24, 2004
Summary: Ferrocenyl aryl ether can be synthesized in
good yields by CuI/ 2,2,6,6-tetramethylheptane-3,5-dione
(TMHD)-catalyzed coupling reactions from iodoferrocene
or 1,1′-diiodoferrocene and various phenols in NMP
solvent using Cs2CO3 or K3PO4 bases.
the contrary, ferrocenyl aryl ethers are almost unknown;
the only synthesis of such compounds dates back to the
early 1960s when Rausch10 and Nefedova11 described
Ullmann type coupling reactions at elevated tempera-
tures to produce ferrocenyl phenyl ethers in modest
yields of around 10-25%.
Consequently, we wish to describe here a reliable and
high-yielding synthesis of ferrocenyl aryl ethers from
bromo- or iodoferrocenes and phenols mediated by
copper(I)-based catalysts.12
To synthesize ferrocenyl aryl ethers, we first tested
the Pd-catalyzed Buchwald-Hartwig ether synthesis13
using various phenols and iodo- or bromoferrocenes.
Unfortunately, all our attempts using different phos-
phine ligands and palladium sources as catalysts did
not lead to the formation of the desired products.
Following this, we evaluated several copper-based cata-
lysts,14 which were demonstrated to work efficiently for
the synthesis of aryl ethers by Buchwald et al. (CuI/
1,10-phenanthroline, Cs2CO3),15 Venkataraman et al.
[Cu(neocup)(PPh3) and Cu(PPh3)3Br],16 and Song et al.
[CuCl/THMD].17 Among these, the CuI/1,10-phenan-
throline catalyst (Table 1, entries 1-4) and the Cu-
(PPh3)3Br complex resulted in the formation of modest
amounts of ferrocenyl aryl ethers. In test reactions of
iodoferrocene and 1,4-tert-butylphenol up to 16% yield
of coupling products were formed with the CuI/1,10-
phenanthroline system (10 mol % CuI and 20 mol %
phen) after 24 h at 110 °C.
Ferrocenes constitute an important class of organo-
metallic compounds, which has found numerous ap-
plications as ligands in homogeneous catalysis,1 for
molecular recognition,2 in polymer sciences,3 and as
biolabels,4 sensors,5 NLO materials,6 and molecular
switches.7
Nonetheless, several deficits in the preparative chem-
istry of ferrocenes are still obvious. As an example, the
synthetic availability of heteroatom (oxygen, nitrogen)-
substituted ferrocenes is rather limited, as the synthetic
routes traditionally used to introduce such heteroatoms
on benzenes are not suitable for ferrocenes. The main
entries into this chemistry are 1,1′-diaminoferrocene
and 1,1′-dihydroxyferrocene or the respective monosub-
stituted ferrocenes, which can be functionalized via
simple nucleophilic substitutions with alkyl halides to
result in secondary or tertiary ferrocenylamines or in
ferrocenyl alkyl ethers.8
Related compounds with additional substituents on
ferrocene are less easily obtained. Basically, substituted
ferrocenyl alkyl ethers are accessible primarily via the
stable trialkylsilyl-protected hydroxyferrocenes, which
can be obtained in good yields from the respective
lithiated cyclopentadienyl silyl ethers and FeCl2.9 On
Significantly improved yields were obtained with the
Venkataraman catalyst Cu(PPh3)3Br. However, instead
of using a preformed copper-phosphine complex, we
considered it more practical to in situ generate the
respective catalyst. Consequently, we evaluated the
* Corresponding author. E-mail: plenio@tu-darmstadt.de.
(1) (a) Colacot, T. J . Chem. Rev. 2003, 103, 3101. (b) Blaser, H.-U.
Adv. Synth. Catal. 2002, 344, 17. (c) Ferrocenes; Togni, A., Hayashi,
T., Eds.; VCH: Weinheim, 1995. (d) Dai, L. X.; Tu, T.; You, S. L.; Deng,
W. P.; Hou, X. L. Acc. Chem. Res. 2003, 36, 659.
(2) Beer, P. D.; Gale, P. A.; Chen, G. Z. Coord. Chem. Rev. 1999,
186, 3.
(3) Manners, I. Macromol. Symp. 2003, 196, 57.
(4) (a) Salmain, M.; J aouen, G. C. R. Chim. 2003, 6, 249. (b)
Nakayama, M.; Ihara, T.; Nakano, K.; Maeda, M. Talanta 2002, 56,
857.
(5) Luk, Y. Y.; Abbott, N. L. Science 2003, 301, 623.
(6) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc, M.
Adv. Organomet. Chem. 1999, 43, 349.
(10) Rausch, M. D. J . Org. Chem. 1961, 26, 1802.
(11) Nefedov, V. A.; Nefedova, M. N. Zh. Obs. Khim. 1966, 36, 122.
(12) Ley, S. V.; Thomas, A. W. Angew. Chem. 2003, 115, 5585.
(13) (a) Mann, G.; Shelby, Q.; Roy, A. H.; Hartwig, J . F. Organo-
metallics 2003, 20, 2775. (b) Torraca, K. E.; Huang, X.; Parrish, C. A.;
Buchwald, S. L. J . Am. Chem. Soc. 2001, 123, 10770. (c) Aranyos, A.;
Old, D. W.; Kiyomori, A.; Wolfe, J . P.; Sadighi, J . P.; Buchwald, S. L.
J . Am. Chem. Soc. 1999, 121, 4369.
(7) Plenio, H.; Aberle, C. Chem. Eur. J . 2001, 7, 4438.
(8) (a) Herberhold, M. In Ferrocenes; pp 219-279, ref 1c. (b) Shafir,
A.; Power, M. P.; Whitener, G. D.; Arnold, J . Organometallics 2000,
19, 3978. (c) Herberhold, M.; Brendel, H.-D.; Hofmann, A.; Hofmann,
B.; Milius, W. J . Organomet. Chem. 1998, 556, 173. (d) Bildstein, B.;
Malaun, M.; Kopacka, H.; Wurst, K.; Mitterbo¨ck, M.; Ongania, K.-H.;
Opromolla, G.; Zanello, G. Organometallics 1999, 18, 4325.
(9) (a) Plenio, H.; Aberle, C. Organometallics 1997, 16, 5950. (b)
Plenio, H.; Aberle, C. Chem. Commun. 1996, 2123.
(14) Cristau, H.-J .; Cellier, P. P.; Hamada, S.; Spindler, J .-F.;
Taillefer, M. Org. Lett. 2004, 6, 913.
(15) Wolter, M.; Nordmann, G.; J ob, G. E.; Buchwald, S. L. Org. Lett.
2002, 4, 973.
(16) (a) Gujadhur, R. K.; Bates, C. M.; Venkataraman, D. Org. Lett.
2001, 3, 4315. (b) Gujadhur, R. K.; Venkataraman, D. Synth. Commun.
2001, 31, 2865.
(17) Buck, E.; Song, Z. J .; Tschaen, D.; Dorner, P. G.; Volante, R.
P.; Reider, P. J . Org. Lett. 2002, 4, 1623.
10.1021/om0497893 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 06/10/2004

Notes
Organometallics, Vol. 23, No. 14, 2004 3549
Ta ble 1. Liga n d Scr een in g for th e Cou p lin g of
Iod ofer r ocen e a n d 1,4-ter t-Bu tylp h en ola
Ta ble 2. Liga n d /Ba se Scr een in g for th e Cou p lin g
of Iod ofer r ocen e a n d P h en ols in NMP a
yieldb
entry
ligand
base
[%]
1
2
3
4
5
6
7
8
2-t-Bu, 4-Me
2-t-Bu, 4-Me
2-t-Bu, 4-Me
2-t-Bu, 4-Me
3-t-Bu
3-t-Bu
3-t-Bu
3-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
4-t-Bu
2,4-Me2
2,4-Me2
2,4-Me2
2,4-Me2
PPh3
PPh3
TMHD
TMHD
PPh3
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
Cs2CO3
K3PO4
21
13
84
72
53
68
96
83
52
71
99
81
41
56
80
75
entry
solvent
ligand
base
yielde [%]
PPh3
1,10-phenb
1,10-phenb
1,10-phenb
1,10-phenb
Cy2PBnc
Cs2CO3
K3PO4
DABCO
Et3N
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K3PO4
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
9
16
<5
<5
94
84
64
85
99
28
37
54
30
TMHD
TMHD
PPh3
1
2
3
4
5
6
7
8
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
NMP
9
10
11
12
13
14
15
16
PPh3
TMHD
TMHD
PPh3
PPh3
TMHD
TMHD
(1-Ad)2PBnc
c
P(o-tolyl)3
c
PPh3
PPh3
PPh3
c
9
d
10
11
12
13
d
NMP
NMP
toluene
BnPAd2
a
Conditions: iodoferrocene (0.125 mmol), CuI (5 mol %), ligand
(12.5 mol %), base (0.25 mmol), phenol (0.25 mmol), T ) 110 °C,
NMP. Samples taken after 17 h. bYields determined by GC.
TMHDd
TMHDd
a
Conditions: iodoferrocene (0.125 mmol), base (0.25 mmol), 1,4-
b
Ta ble 3. Cou p lin g of Iod ofer r ocen e a n d
1,1′-Diiod ofer r ocen e in th e P r esen ce of
2,2,6,6-Tetr a m eth ylh ep ta n e-3,5-d ion e (TMHD)a
tert-butylphenol (0.25 mmol). CuI (10 mol %), 1,10-phenanthro-
line (20 mol %), 110 °C, 24 h. c CuI (10 mol %), ligand (20 mol %),
d
110 °C, 30 h. CuI (5 mol %), ligand (12.5 mol %), 110 °C; 5 h.
e Yields determined by GC.
yieldb
[%]
isolated
suitability of several different phosphines (PPh3, (1-Ad)2-
PBn, Cy2PBn, P(o-tolyl)3) in combination with CuI (10
mol %) as the copper source, utilizing different Cu:P
ratios and several different bases in toluene solvent.
Among the bases, Cs2CO3 and K3PO4 turned out to be
the best ones. Concerning the influence of the phos-
phines, neither the nature of the substituents nor the
ratio Cu:P appears to be critical. As can be seen in Table
1, copper complexes with various phosphines result in
the formation of 1 in roughly the same yields (entries
5-9). Consequently, we decided to use PPh3 as the
cheapest one of the phosphines studied together with
equimolar amounts of CuI. While the yields of the
ferrocenyl aryl ethers are satisfactory, the large amounts
of catalysts needed as well as extended reaction times
obviously render this route less attractive.
entry
ferrocene
yieldc [%]
1
2
3
4
5
6
7
8
H
FcI
FcI
FcI
FcI
FcI
FcI
FcI
FcI
62
89
>95
44
42
81
86
30
77
89
87
65
24
90
40
65
27
30
22
none
none
none
2,4-Me2
3,5-Me2
2,4,6-Me3
2-t-Bu, 4-Me
3-t-Bu
93
>95
>95
86
33
>95
4-t-Bu
2,4-t-Bu
2-t-Bu, 6-Me
4-Cl
H
4-t-Bu
2,4-Me2
3,5-Me2
FcOH
2-NO2
4-OMe, 2-NO2
4-Cl, 2-NO2
9
FcI
FcI
10
11
12
13
14
15
16
17
18
1,1′-FcI2
1,1′-FcI2
1,1′-FcI2
1,1′-FcI2
FcI
FcI
FcI
FcI
75
70
60
<5
<5
<5
Recently another protocol for an improved Ullmann
type coupling for diaryl ether synthesis was published
by Song et al., which utilizes 2,2,6,6-tetramethylhep-
tane-3,5-dione (TMHD) as a ligand in combination with
CuCl as the copper source, Cs2CO3 as the base, and
NMP as the solvent.17
a
Conditions: iodoferrocene (0.125 mmol) or 1,1′-diiodoferrocene
(0.062 mmol), CuI (5 mol %), TMHD (12.5 mol %), Cs2CO3 (0.25
mmol), phenol (0.25 mmol), T ) 110 °C, NMP, reaction time 20 h.
Yields determined by GC. c Yields based on isolated material
after chromatographic purification.
b
The optimized reaction conditions [CuI (5 mol %),
TMHD (12.5 mol %), Cs2CO3 (0.25 mmol), T ) 110 °C,
solvent NMP] for the synthesis of ferrocenyl aryl ethers
were now applied to the synthesis of several ferrocenyl
aryl ethers (Table 3). Most coupling reactions now result
in the formation of the respective ferrocenyl aryl ethers
in very good yields. Steric bulk (Me or t-Bu) ortho to
the oxygen atom does not reduce the yields of the
coupling products significantly (entries 2, 5, 8), while
for phenols with substituents in both the 2- and the
6-position respectable coupling yields are observed.
Somewhat unexpectedly the reaction fails completely
with strongly electron-withdrawing substituents on the
phenol, since none of the -NO2-substituted phenols can
be coupled successfully. Interestingly, instead of ether
formation, a hydro-dehalogenation takes place, to gen-
erate ferrocene from the corresponding ferrocenyl ha-
Consequently, we tested NMP as the solvent for the
coupling reactions, applying the improved conditions
from the first screen to the catalysts CuI/PPh3 and CuI/
TMHD. The results (Table 1, entries 10-13) clearly
show that NMP is a more suitable solvent, especially
for the CuI/TMHD system (entry 12). Consequently, we
decided to study this catalytic system in more detail. A
second set of screening experiments was performed
focusing on the CuI/THMD and the CuI/PPh3 catalysts.
From the results presented in Table 2 it is quite clear
that the combination of CuI/TMHD gives much better
results than CuI/PPh3. Furthermore, with CuI/THMD
the catalyst activity is consistently higher when using
Cs2CO3 as a base instead of K3PO4. However, with a
view to the drastically lower price of K3PO4 the phos-
phate should still be considered as an alternative.

3550 Organometallics, Vol. 23, No. 14, 2004
Notes
lides. Such a transformation is known to be a typical
side-reaction in transition metal-catalyzed cross-cou-
pling reactions.18 The respective 1,1′-substituted ferro-
cenyl aryl ethers were also synthesized in good yields
from 1,1′-diiodoferrocene (entries 11-14). The modest
yields observed after isolation of the respective ferrocene
diethers are most likely due to significant decomposition
(oxidation) during chromatographic purifications of the
small amounts of material synthesized. It should be
noted that the diferrocenyl ether (entry 15) is a simple
metallocene compound that has not been described in
the literature before. The compound is formed in a
modest yield (22%) with the Cu(I)-catalyzed methodol-
ogy since it is accompanied by the reduction of Cu(I) to
Cu(0).
ically demanding phenols can be coupled efficiently,
while reactions of electron-deficient nitrophenols do not
yield the respective aryl ethers but result in the forma-
tion of dehalogenated ferrocenes instead.
Exp er im en ta l Section
Gen er a l Meth od s. Phenols, bases, CuI, and ligands were
used as received. All reactions and experiments were per-
formed under an atmosphere of dry argon using standard
Schlenk techniques. Column chromatography: Silica MN60
(63-200 µm), TLC on Merck plates coated with silica gel 60,
F254. Gas chromatography: Perkin-Elmer Autosystem with
a Varian CP-SIL-8 column; ferrocene samples were applied
to the column using the sandwich technique to obtain repro-
ducible results. NMR spectroscopy: spectra recorded at 293 K
with a Bruker Avance 500 (1H NMR 500 MHz, 13C NMR 125
MHz), a Bruker AC 300 (1H NMR 300 MHz, 13C NMR 75
MHz), or a Bruker AC 200 (1H NMR 200 MHz) spectrometer.
1H NMR spectra were referenced to residual protonated
impurities in the solvent (CDCl3 7.24 ppm), 13C NMR to the
solvent signal (CDCl3 77.0 ppm). Starting materials were
commercially available or prepared according to literature
procedures: iodoferrocene,19,20 1,1′-diiodoferrocene,21 1,1′-di-
bromoferrocene.22 The coupling products obtained were char-
acterized by 1H NMR and 13C NMR spectroscopy. For phenoxy-
ferrocene (1)23 and 1,1′-diphenoxyferrocene (11)23 spectroscopic
data were found to be identical with those reported in the
literature.
Gen er a l P r oced u r e for th e Scr een in g of Cou p lin g
Rea ction s. In a Schlenk tube CuI (2.4 mg, 12.5 µmol, 10 mol
%), the respective ligand (25 µmol, 20 mol %), the respective
ferrocenyl halide (0.125 mmol), the respective phenol (0.25
mmol), and bases (0.25 mmol) were dissolved in NMP or
toluene (7.5 mL), and the reaction was stirred at 110 °C for a
given time. In the case of NMP solvent after completion of the
reaction, diethyl ether was added (35 mL) and the mixture
was extracted with water (3 × 15 mL). After evaporation of
the volatiles the crude product was purified by column
chromatography (n-heptane).
Op tim ized P r oced u r e for Syn th esis of F er r ocen yl
P h en yl Eth er s. In a Schlenk tube CuI (2.4 mg, 12.5 µmol,
5.0 mol %), TMHD (6.4 µL, 31.2 µmol), iodoferrocene (78 mg,
0.25 mmol) (or half the molar amount of 1,1′-diiodoferrocene),
the respective phenol (0.50 mmol), and Cs2CO3 (163.2 mg, 0.50
mmol) were dissolved in NMP (15 mL), and the reaction was
stirred at 110 °C for the given time. After completion, diethyl
ether was added (50 mL) and the mixture was extracted with
water (3 × 25 mL). After evaporation of the organic solvent
the crude product was purified by column chromatography (n-
heptane) to obtain the respective pure products.
For all of the reactions described in Tables 1-3 we
have used iodoferrocene or 1,1′-diiodoferrocene as the
organometallic building blocks. The reason for this was
the expectation that the lower bond energy of the
carbon-iodine bond would render more active sub-
strates than with the carbon-bromine bond in bromi-
nated ferrocenes. However, since only bromoferrocene
and 1,1′-dibromoferrocene are commercially available,
we considered it useful to also evaluate coupling reac-
tions of brominated ferrocenes. Using the same catalyst
it is also possible to couple bromoferrocene; however,
the activity of the catalyst is roughly half of that for
iodoferrocenes. Consequently, much higher catalyst
loadings are required to effect the coupling reactions.
Su m m a r y. We have presented here a simple and
high-yielding synthesis of various ferrocenyl aryl ethers
by a Ullmann type coupling of halogenated ferrocenes
(FcI, 1,1′-FcI2, FcBr, 1,1′-FcBr2) and different phenols
using a catalyst composed of CuI and 2,2,6,6-tetra-
methylheptane-3,5-dione (TMHD). Unhindered and ster-
2,4-Dim eth ylp h en oxyfer r ocen e (2). Rf ) 0.26 [n-hep-
tane]. 1H NMR (CDCl3): 2.23 (s, 3H, o-CH3), 2.26 (s, 3H,
p-CH3), 3.87 (“t”, 2H, J ) 2.0 Hz, C5H4), 4.14 (t, 2H, J ) 2.0
Hz, C5H4), 4.23 (s, 5H, C5H5), 6.86 (s, 2H, C6H3), 6.97 (s, 1H,
C6H3). 13C NMR (CDCl3): 16.2 (ArCH3), 20.7 (ArCH3), 59.1
(C5H4), 62.6 (C5H4), 69.3 (C5H5), 117.0 (ArC), 127.1 (ArC), 128.1
(C(C5H4)O), 131.7 (ArC), 132.3 (H3C-ArC), 154.5 (O-ArC).
3,5-Dim eth ylp h en oxyfer r ocen e (3). Rf ) 0.19 [n-hep-
1
tane]. H NMR (CDCl3): 2.26 (s, 6H, CH3), 3.93 (“t”, 2H, J )
1.9 Hz, C5H4), 4.21 (t, 2H, J ) 1.9 Hz, C5H4), 4.26 (s, 5H, C5H5),
6.60 (s, 2H, C6H3), 6.65 (s, 1H, C6H3). 13C NMR (CDCl3): 21.5
(19) Bildstein, B.; Malaun, M.; Kopacka, H. Organometallics 1999,
18, 4325.
(20) Kamounah, F. S.; Christensen, J . B. J . Chem. Res. Synop. 1997,
150.
(21) Kovar, R. F.; Rausch, M. D.; Rosenberg, H. Organomet. Chem.
Synth. 1970/71, 1, 173.
(22) Dong, T.-Y.; Lai, L.-L. J . Organomet. Chem. 1996, 509, 131.
(23) Nesmeyanov, A. N.; Petrovskii, P. V.; Fedorov, L. A.; Robas, V.
I.; Fedin, E. I. Zh. Strukt. Khim. 1973, 14, 49.
(18) Mukhopadhyay, S.; Rothenberg, G.; Gitis, D.; Baidossi, M.;
Ponde, D. E.; Sasson, Y. J . Chem. Soc., Perkin Trans. 2000, 1809.

Notes
Organometallics, Vol. 23, No. 14, 2004 3551
(ArCH3), 60.2 (C5H4), 63.0 (C5H4), 69.4 (C5H5), 114.7 (o-ArC),
122.0 (C(C5H4)O), 124.2 (p-ArC), 139.2 (H3C-ArC), 159.1 (O-
ArC).
3H, o-CH3), 3.72 (“t”, 2H, J ) 2.0 Hz, C5H4), 3.95 (t, 2H, J )
2.0 Hz, C5H4), 4.17 (s, 5H, C5H5), 6.79 (t, 1H, J ) 7.6 Hz, C6H3),
7.12 (d, 1H, J ) 7.6 Hz, C6H3), 7.16 (d, 1H, J ) 7.6 Hz, C6H3).
4-Ch lor op h en oxyfer r ocen e (10). Rf ) 0.11 [n-heptane].
1H NMR (CDCl3): 3.94 (“t”, 2H, J ) 2.2 Hz, C5H4), 4.12 (“t”,
d, 2H, J ) 2.2 Hz, C5H4), 4.18 (s, 5H, C5H5), 6.86 (d, 2H, J )
8.6 Hz), 7.23 (d, 2H, J ) 8.6 Hz).
1,1′-Di(p h en oxy)fer r ocen e (11). Rf ) 0.55 [cyclohexane].
1H NMR (CDCl3): 3.89 (“t”, 4H, J ) 2.0 Hz, C5H4), 4.15 (t,
4H, J ) 2.0 Hz, C5H4), 6.91-6.96 (m, 4H, ArH), 7.03-7.04 (m,
2H, ArH), 7.18-7.23 (m, 4H, ArH). 13C NMR (CDCl3): 58.9
(C5H4), 61.9 (C5H4), 117.4 (ArC), 122.8 (ArC), 129.8 (ArC), 123.1
(C(C5H4)O), 159.3 (O-ArC). Anal. Calcd for C22H18FeO2
(370.23): C, 71.37; H, 4.90. Found: C, 70.94, H, 5.02.
2,4,6-Tr im eth ylp h en oxyfer r ocen e (4). Rf ′ ) 0.185 [n-
1
heptane]. H NMR (CDCl3): 2.18 (s, 6H, o-CH3), 2.22 (s, 3H,
p-CH3), 3.77 (“t”, 2H, J ) 1.9 Hz, C5H4), 4.02 (t, 2H, J ) 1.9
Hz, C5H4), 4.22 (s, 5H, C5H5), 6.78 (s, 2H, C6H3). 13C NMR
(CDCl3): 16.8 (ArCH3), 20.7 (ArCH3), 59.2 (C5H4), 61.7 (C5H4),
69.3 (C5H5), 129.5 (ArC), 122.4 (C(C5H4)O), 134.2 (H3C-ArC),
142.1 (H3C-ArC), 154.3 (O-ArC). Anal. Calcd for C19H20FeO
(320.21): C, 71.27; H, 6.30. Found: C, 71.19; H, 6.31.
2-ter t-Bu tyl-4-m eth ylp h en oxyfer r ocen e (5). Rf ) 0.29
[n-heptane]. 1H NMR (CDCl3): 1.46 (s, 9H, t-BuH), 3.94 (t,
2H, J ) 2.0 Hz, C5H4), 4.21 (“t”, 2H, J ) 2.0 Hz, C5H4), 4.28
(s, 5H, C5H5), 6.69 (t, 1H, J ) 8.2 Hz, C6H3), 6.84 (d, 1H, J )
8.2 Hz, C6H3), 7.07 (s, 1H, J ) 8.2 Hz, C6H3). 13C NMR
(CDCl3): 21.0 (ArCH3), 30.1 (CH3), 34.8 (CCH3), 61.1 (C5H4),
63.2 (C5H4), 69.4 (C5H5), 115.9 (ArC), 121.7 (C(C5H4)O), 127.1
(ArC), 127.4 (ArC), 130.9 (H3C-ArC), 138.3 (t-Bu-ArC), 156.5
(O-ArC).
3-ter t-Bu tylp h en oxyfer r ocen e (6). Rf ) 0.18 [n-heptane].
1H NMR (CDCl3): 1.31 (s, 9H, t-BuH), 3.98 (“t”, 2H, J ) 1.9
Hz, C5H4), 4.25 (t, 2H, J ) 1.9 Hz, C5H4), 4.30 (s, 5H, C5H5),
6.78-6.74 (m, 1H, ArH), 7.23-7.04 (m, 3H, ArH). 13C NMR
(CDCl3): 31.4 (CH3), 34.9 (CCH3), 59.8 (C5H4), 63.1 (C5H4), 69.6
(C5H5), 113.1 (ArC), 115.0 (ArC), 119.6 (ArC), 123.0 (C(C5H4)O),
128.9, 153.1 (t-Bu-ArC), 158.6 (O-ArC).
1,1′-Di(4-ter t-bu tylp h en oxy)fer r ocen e (12). Rf ) 0.58
1
[cyclohexane/ethyl acetate (20:1)]. H NMR (CDCl3): 1.22 (s,
18H, t-BuH), 3.95 (“t”, 2H, J ) 2.2 Hz, C5H4), 4.21 (t, 4H, J )
2.2, C5H4), 6.91 (d, 4H, J ) 8.6 Hz, C6H4), 7.23 (d, 4H, J ) 8.6
Hz, C6H4). 13C NMR (CDCl3): 31.6 (CH3), 34.3 (C(CH3)3), 60.8
(C5H4), 64.2 (C5H4), 117.0 (ArC), 126.2 (ArC), 141.7 (C(C5H4)O),
145.4 (t-Bu-ArC), 156.4 (ArC).
1,1′-Di(2,4-d im eth ylp h en oxy)fer r ocen e (13). Rf ) 0.57
1
[cyclohexane]. H NMR (CDCl3): 2.17 (s, 6H, o-CH3), 2.22 (s,
6H, p-CH3), 3.85 (“t”, 4H, J ) 2.0 Hz, C5H4), 4.11 (t, 4H, J )
2.0 Hz, C5H4) 6.77-6.84 (m, 4H, C6H3), 6.98 (br s, 2H, C6H3).
13C NMR (CDCl3): 18.8 (ArCH3), 23.4 (ArCH3), 58.8 (C5H4),
63.0 (C5H4), 115.8 (ArC), 125.8 (ArC), 129.6 (ArC), 130.5
(C(C5H4)O), 131.3 (ArC), 134.4 (ArC), 155.6 (O-ArC).
4-ter t-Bu tylp h en oxyfer r ocen e (7). Rf ) 0.17 [n-heptane].
1H NMR (CDCl3): 1.22 (s, 9H, t-BuH), 3.86 (“t”, 2H, J ) 1.9
Hz, C5H4), 4.13 (t, 2H, J ) 1.9 Hz, C5H4), 4.19 (s, 5H, C5H5),
6.85 (d, 2H, J ) 8.8 Hz, C6H4), 7.21 (d, 2H, J ) 8.8 Hz, C6H4).
13C NMR (CDCl3): 31.6 (CH3), 34.3 (CCH3), 59.8 (C5H4), 62.9
(C5H4), 69.4 (C5H5), 116.7 (o-ArC), 126.2 (m-ArC), 141.6
(C(C5H4)O), 145.3 (t-Bu-ArC), 156.5 (O-ArC). Anal. Calcd for
1,1′-Di(3,5-d im eth ylp h en oxy)fer r ocen e (14). Rf ) 0.56
1
[cyclohexane]. H NMR (CDCl3): 2.24 (s, 12H, CH3), 3.93 (“t”,
4H, J ) 1.9 Hz, C5H4), 4.16 (t, 4H, J ) 1.9 Hz, C5H4), 6.55 (s,
4H, C6H3), 6.66 (s, 2H, C6H3). 13C NMR (CDCl3): 20.3 (ArCH3),
59.0 (C5H4), 64.7 (C5H4), 113.7 (o-ArC), 123.1 (C(C5H4)O), 124.7
(p-ArC), 138.1 (H3C-ArC), 153.2 (O-ArC).
C
20H22FeO (334.24): C, 71.87; H, 6.63. Found: C, 71.37; H,
6.78.
2,4-Di-ter t-bu tylp h en oxyfer r ocen e (8). Rf ) 0.28 [n-
1
Difer r ocen yl Eth er (15). Rf ) 0.49 [n-heptane]. H NMR
(CDCl3): 3.78 (“t”, 4H, J ) 1.9 Hz, C5H4), 4.08 (t, 4H, J ) 1.9
Hz, C5H4), 4.20 (s, 10H, C5H5). 13C NMR (CDCl3): 62.9 (C5H4),
65.3 (C5H4), 68.4 (C5H5), 124.9 (C(C5H4)O). EI-MS: m/z 330
(M+).
heptane]. 1H NMR (CDCl3): 1.27 (s, 9H, 4-t-BuH), 1.47 (s, 9H,
2-t-BuH), 3.95 (“t”, 2H, J ) 1.9 Hz, C5H4), 4.23 (t, 2H, J ) 1.9
Hz, C5H4), 4.29 (s, 5H, C5H5), 6.71 (d, 1H, J ) 8.6 Hz, C6H3),
7.05 (d, 1H, J ) 8.6 Hz, C6H3), 7.30 (s, 1H, C6H3). 13C NMR
(CDCl3): 30.1 (o-C(CH3)3), 31.7 (p-C(CH3)3), 34.4 (CCH3), 35.1
(CCH3), 61.2 (C5H4), 63.2 (C5H4), 69.4 (C5H5), 115.0 (ArC), 121.3
(C(C5H4)O), 123.3 (ArC), 123.8 (ArC), 137.5 (o-t-Bu-ArC), 144.1
(p-t-Bu-ArC), 156.3 (O-ArC).
Ack n ow led gm en t. This work was supported by the
TU Darmstadt, the Deutsche Forschungsgemeinschaft,
and the Fonds der Chemischen Industrie. We wish to
thank Frau E. Hilms for experimental assistance.
2-ter t-Bu tyl-6-m eth ylp h en oxyfer r ocen e (9). Rf ) 0.11
[n-heptane]. 1H NMR (CDCl3): 1.42 (s, 9H, t-BuH), 2.25 (s,
OM0497893