Asymmetric synthesis of [3](1,1′)- and [3](1,1′)[3](3,3′)-ferrocenophanes

Article abstract of DOI:10.1021/om990171g

(R)-α-Ferrocenyl alcohols underwent conversion to their corresponding methyl ethers on treatment with MeOH/AcOH, which were in turn converted to ethyl 3-ferrocenylpropanoates when combined with 1-ethoxy-1-(trimethylsilyloxy)ethene and BF₃·OEt₂. After ester hydrolysis, the resulting acids (92-96% ee) underwent heteroannular Friedel-Crafts cyclization to give singly bridged ferrocenophanes of high enantiomeric purity. The methanolysis and silyl ketene acetal addition sequence was also applied to (R,R)-1,1′-bis(phenylhydroxymethyl)-ferrocene, and to (R,R)-1,1′-bis((4-bromophenyl)hydroxymethyl)ferrocene, to give the corresponding diacids (94% ee) after ester hydrolysis. On Friedel-Crafts cyclization, the first of these diacids gave a 7:37:56 ratio of singly bridged ferrocenophanes after conversion of the remaining acid functionalities to methyl esters. The least abundant product was identified as ( _pR)-1,1′-(R)-(1-oxo-3-phenyl-1,3-propanediyl)-2-(R)-(3-methoxy- 3-oxo-1-phenylpropyl)ferrocene by an X-ray crystal structure analysis. After separation, the most abundant isomer was converted in four steps to the novel doubly bridged C₂-symmetric ferrocenophane (R,R,_pS, _pS)-1,1′-(1-phenyl-1,3-propanediyl)-3,3′-(3-phenyl-1,3- propanediyl)ferrocene, characterized by an X-ray crystal structure analysis. The remaining isomer was converted to the corresponding 1,1′,3,3′-(R,R,_pR,_pR)-ferrocenophane. Also synthesized by this method was (R,R,_pS, _pS)-1,1′-(1-(4-bromophenyl)-1,3-propanediyl)-3,3′-(3-(4- bromophenyl)-1,3-propanediyl)-ferrocene, which after bromine-lithium exchange was converted to the corresponding dicarboxylicacid. (R,R,_pS, _pS)-1,1′-(1-Phenyl-1,3-propanediyl)-3,3′-(3-phenyl-1,3- propanediyl)-ferrocenium tetrafluoroborate catalyzed the reaction between methacrolein and cyclopentadiene, although no enantioselectivity was observed in the resulting Diels-Alder adducts.

Full text of DOI:10.1021/om990171g

3750
Organometallics 1999, 18, 3750-3759
Asym m etr ic Syn th esis of [3](1,1′)- a n d
[3](1,1′)[3](3,3′)-F er r ocen op h a n es
Andrew J . Locke and Christopher J . Richards*,‡
Department of Chemistry, Cardiff University, PO Box 912, Cardiff, CF1 3TB, U.K.
Received March 9, 1999
(R)-R-Ferrocenyl alcohols underwent conversion to their corresponding methyl ethers on
treatment with MeOH/AcOH, which were in turn converted to ethyl 3-ferrocenylpropanoates
when combined with 1-ethoxy-1-(trimethylsilyloxy)ethene and BF3‚OEt2. After ester hy-
drolysis, the resulting acids (92-96% ee) underwent heteroannular Friedel-Crafts cyclization
to give singly bridged ferrocenophanes of high enantiomeric purity. The methanolysis and
silyl ketene acetal addition sequence was also applied to (R,R)-1,1′-bis(phenylhydroxymethyl)-
ferrocene, and to (R,R)-1,1′-bis((4-bromophenyl)hydroxymethyl)ferrocene, to give the corre-
sponding diacids (94% ee) after ester hydrolysis. On Friedel-Crafts cyclization, the first of
these diacids gave a 7:37:56 ratio of singly bridged ferrocenophanes after conversion of the
remaining acid functionalities to methyl esters. The least abundant product was identified
as (pR)-1,1′-(R)-(1-oxo-3-phenyl-1,3-propanediyl)-2-(R)-(3-methoxy-3-oxo-1-phenylpropyl)fer-
rocene by an X-ray crystal structure analysis. After separation, the most abundant isomer
was converted in four steps to the novel doubly bridged C2-symmetric ferrocenophane
(R,R,pS,pS)-1,1′-(1-phenyl-1,3-propanediyl)-3,3′-(3-phenyl-1,3-propanediyl)ferrocene, charac-
terized by an X-ray crystal structure analysis. The remaining isomer was converted to the
corresponding 1,1′,3,3′-(R,R,pR,pR)-ferrocenophane. Also synthesized by this method was
(R,R,pS,pS)-1,1′-(1-(4-bromophenyl)-1,3-propanediyl)-3,3′-(3-(4-bromophenyl)-1,3-propanediyl)-
ferrocene, which after bromine-lithium exchange was converted to the corresponding
dicarboxylic acid. (R,R,pS,pS)-1,1′-(1-Phenyl-1,3-propanediyl)-3,3′-(3-phenyl-1,3-propanediyl)-
ferrocenium tetrafluoroborate catalyzed the reaction between methacrolein and cyclopen-
tadiene, although no enantioselectivity was observed in the resulting Diels-Alder adducts.
In tr od u ction
paratively rigid ferrocene derivatives due to linkage of
the two cyclopentadienyl rings. We are interested in the
possibilities offered by chiral, metal-containing, and
conformationally restricted building blocks for the syn-
thesis of new catalysts and materials, as could be
explored following the development of methodology for
the rapid asymmetric synthesis of ferrocenophanes. To
this end we noted that [3]-ferrocenophanes are gener-
ated in high yield on heteroannular Friedel-Crafts
cyclization of ferrocenepropanoic acids,4 a reaction
extended to R-substituted and thus chiral ferrocenepro-
panoic acids5 that have been resolved prior to cycliza-
tion.6 Resolution has also been utilized during the
synthesis of nonracemic planar chiral [3]-ferroceno-
phanes.7
The concept of ferrocene acting as a three-dimensional
metal-containing equivalent of benzene has prompted
the synthesis of novel air-stable structures that have
found many applications in catalysis and materials
science.1 This has recently been extended with the
development of several methods for the asymmetric
generation of ferrocene derivatives containing both
planar and central elements of chirality.2 However, this
activity has been barely applied to the asymmetric
synthesis of bridged ferrocenophanes,3 which are com-
‡ RichardsCJ @cardiff.ac.uk. Fax: +44 1222 874030.
(1) Ferrocenes; Togni, A., Hayashi, T., Eds.; VCH: New York,
Weinheim, 1995.
(2) Reviews: (a) Kagan, H. B.; Riant, O. Advances in Asymmetric
Synthesis; Hassner, A., Ed.; J AI Press: Greenwich, CT, 1997; Vol. 2,
pp 189-235. (b) Richards, C. J .; Locke, A. J . Tetrahedron: Asymmetry
1998, 9, 2377. (c) Togni, A. Angew. Chem., Int. Ed. Engl. 1996, 35,
1475. See also: (d) Riant, O.; Samuel, O.; Flessner, T.; Taudien, S.;
Kagan, H. B. J . Org. Chem. 1997, 62, 6733. (e) Riant, O.; Gilles, A.;
Guillaneux, D.; Samuel, O.; Kagan, H. B. J . Org. Chem. 1998, 63, 3511.
(f) Tsukazaki, M.; Tinkl, M.; Roglans, A.; Chapell, B. J .; Taylor, N. J .;
Snieckus, V. J . Am. Chem. Soc. 1996, 118, 685. (g) Iftime, G.; Daran,
J . C.; Manoury, E.; Balavoine, G. G. A. Angew. Chem., Int. Ed. Engl.
1998, 37, 1698.
We recently reported that ferrocenepropanoates can
be rapidly accessed by addition of silyl ketene acetals
to ferrocenylmethyl ethers promoted by BF3‚OEt2.8 With
the aim of applying this reaction to the synthesis of
ferrocenophanes, and specifically the C2-symmetric fer-
rocenophane 1, we also reported that the racemic diester
(3) (a) Gibis, K.-L.; Helmchen, G.; Huttner, G.; Zsolnai, L. J .
Organomet. Chem. 1993, 445, 181. (b) Iftime, G.; Daran, J . C.;
Manoury, E.; Balavoine, G. G. A. Organometallics 1996, 15, 4808. (c)
Balavoine, G. G. A.; Daran, J . C.; Iftime, G.; Manoury, E.; Moreau-
Bossuet, C. J . Organomet. Chem. 1998, 567, 191. (d) Iftime, G.; Daran,
J . C.; Manoury, E.; Balavoine, G. G. A. Angew. Chem., Int. Ed. Engl.
1998, 37, 1698.
(4) Rinehart, K. L.; Curey, R. J .; Gustafson, D. H.; Harrison, K. G.;
Bozak, R. E.; Bublitz, D. E. J . Am. Chem. Soc. 1962, 84, 3263.
(5) Huffman, J . W.; Asbury, R. L. J . Org. Chem. 1965, 30, 3941.
(6) Dormond, A. Bull. Chim. Soc. Fr. 1970, 3962.
(7) Falk, H.; Hofer, O.; Schlo¨gl. Monatsh. Chem. 1969, 100, 624.
(8) Locke, A. J .; Gouti, N.; Richards, C. J .; Hibbs, D. E.; Hursthouse,
M. B. Tetrahedron 1996, 52, 1461.
10.1021/om990171g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 08/13/1999

Synthesis of Ferrocenophanes
Organometallics, Vol. 18, No. 18, 1999 3751
Sch em e 1
2a can be readily prepared from the racemic diether 3a
with complete control of relative stereochemistry. This
reaction occurs with the addition of 2 equiv of 1-ethoxy-
1-(trimethylsilyloxy)ethene to intermediate R-ferroce-
nylcarbenium ions formed by Lewis acid-promoted
methoxide removal. We now wish to give a full account
of this reaction for the asymmetric synthesis of ferro-
cenophanes, as exemplified by 1, the stereoselectivity
of the heteroannular cyclization required for this struc-
ture, and the use of these processes for the synthesis of
functionalized ferrocenophanes.9
Resu lts a n d Discu ssion
The generation of 2a proceeds via the in situ genera-
tion and trapping of R-ferrocenylcarbenium ions ob-
tained when 3a is treated with BF3‚OEt2 in the presence
of 1-ethoxy-1-(trimethylsilyloxy)ethene. It was antici-
pated that the known configurational stability of R-fer-
rocenylcarbenium ions10 would permit application of this
general reaction to the asymmetric synthesis of ethyl
3-ferrocenylpropanoates. To test this theory, we began
by carrying out the previously reported oxazaborolidine-
catalyzed reduction of ferrocenyl ketones11 4a -c to give
known alcohols 5a /c and the new alcohol 5b. For 5a /c
this reaction had been reported to proceed in >95% ee,
and the rotations we obtained for these two compounds
were very close to those previously reported. Subsequent
methanolysis was achieved by treatment with 10%
acetic acid in methanol12 to give excellent yields of
ethers 6a -c. The absolute configuration of 6c was
determined by comparison of its rotation to that previ-
ously reported for (R)-6c,13 confirming that methanoly-
sis proceeds with retention of configuration. On treat-
ment with 1-ethoxy-1-(trimethylsilyloxy)ethene and
BF3‚OEt2 in CH2Cl2 at -78 °C, followed by warming of
the reaction mixture to room temperature, each of the
ethers was cleanly converted to ethyl 3-ferrocenylpro-
panoates 7a -c. Following hydrolysis to their corre-
sponding acids 8a -c, their enantiomeric excesses were
determined by DCC-mediated coupling with (S)-methyl
mandelate and examination of the resulting mixture by
NMR on completion of the reaction. The high enantio-
meric excesses measured (Scheme 1) reveal that both
methanolysis and silyl ketene acetal addition proceed
with excellent stereochemical integrity. The absolute
configurations assigned to 8a -c assume that C-C bond
formation also proceeds with retention of configuation,
as has been reported for the addition of organozincs14
and heteroatom nucleophiles to ferrocenyl acetates.15,16
The first series of enantiomerically enriched ferro-
cenophanes were completed by intramolecular Friedel-
Crafts cyclization. Although the best yields for this
reaction had previously been obtained by direct cycliza-
tion of acids with TFAA in CCl4,4 we found that SnCl4-
promoted cyclization of the preformed 3-ferrocenylpro-
panoyl chlorides gave excellent yields of ferrocenophanes
9a -c.
This methodology was then extended to the 1,1′-
ferrocenyldiketones 10a /b. Again use of the previously
reported oxazaborolidine-catalyzed reduction methodol-
ogy17 gave an excellent yield of known (from 10a ) and
new (from 10b) diols, both obtained as 92:8 mixtures of
diastereoisomers. Attempted purification of these diols
led to significant formation of oxaferrocenophanes formed
by dehydration. As contamination by the oxazaboroli-
dine catalyst residues could not be removed by recrys-
tallization, the crude diols were treated directly with
acetic acid in methanol to give ethers 3a /3b, from which
the minor meso diastereoisomers were readily removed
on recrystallization. Treatment with 1-ethoxy-1-(tri-
methylsilyloxy)ethene and BF3‚OEt2 in CH2Cl2 as before
gave clean conversion to diesters 2a /b with complete
control of relative stereochemistry, only a single dias-
tereoisomer being observed in the crude product mixture
(14) Perea, J . J . A.; Ireland, T.; Knochel, P. Tetrahedron Lett. 1997,
38, 5961.
(9) (a) Locke, A. J .; Richards, C. J . Tetrahedron Lett. 1996, 37, 7861.
(b) Locke, A. J .; Richards, C. J .; Hibbs, D. E.; Hursthouse, M. B.
Tetrahedron: Asymmetry 1997, 8, 3383.
(10) Gokel, G.; Hoffmann, P.; Klusacek, H.; Marquarding, D.; Ruch,
E.; Ugi, I. Angew. Chem., Int. Ed. Engl. 1970, 9, 64.
(11) Wright, J .; Frambes, L. J . Organomet. Chem. 1994, 476, 215.
(12) Nesmeyanov, A. N.; Izv. Akad. Nauk SSSR, Ser. Khim. 1963,
11, 1972.
(15) (a) Gokel, G. W.; Ugi, I. K. Angew. Chem., Int. Ed. Engl. 1971,
10, 191. (b) Gokel, G.; Marquarding, D.; Ugi, I. K. J . Org. Chem. 1972,
37, 3052. (c) Hayashi, T.; Mise, T.; Fukushima, M.; Kagotani, M.;
Nagashima, N.; Hamada, Y.; Matsumoto, A.; Kawakami, S.; Konishi,
M.; Yamamoto, K.; Kumada, M. Bull. Chem. Soc. J pn. 1980, 53, 1138.
(d) Togni, A.; Ha¨usel, R. Synlett 1990, 633. (e) Togni, A.; Rihs, G.;
Blumer, R. E. Organometallics 1992, 11, 613. (f) Schwink, L.; Knochel,
P.; Eberle, T.; Okuda, J . Organometallics 1998, 17, 7.
(13) The previous synthesis of nonracemic 6c used resolved (R)-N,N,-
dimethyl-1-ferrocenylethylamine followed by quaternization and treat-
ment with 1:1 methanol/acetonitrile: Gokel, G. W.; Marquarding, D.;
Ugi, I. K. J . Org. Chem. 1972, 37, 3052.
(16) For an exception to this general rule see: Taniguchi, N.;
Uemura, M. Tetrahedron Lett. 1998, 30, 5385.
(17) (a) Schwink, L.; Knochel, P. Tetrahedron Lett. 1996, 37, 25. (b)
Schwink, L.; Knochel, P. Chem. Eur. J . 1998, 4, 950.

3752 Organometallics, Vol. 18, No. 18, 1999
Locke and Richards
Sch em e 2
of each reaction. To determine the control of absolute
stereochemistry in these reactions, the diacids 11a /b
obtained on hydrolysis were coupled with (S)-methyl
mandalate, revealing both to be of high enantiomeric
purity (Scheme 2). We had been concerned that metha-
nolysis and/or silyl ketene acetal addition might have
proceeded via intermediate meso oxoniumferroceno-
phanes, which can now be ruled out, as these would
have led to racemic products.
F igu r e 1. Two independent crystal structures of 12.
Selected bond distances (Å) and angles (deg) with corre-
sponding values for the second structure given in paren-
theses: C(1)-Fe 2.026(8) [2.004(7)], C(3)-Fe 2.051(7)
[2.031(7)], C(1)-C(13) 1.549(10) [1.532(9)], C(10)-C(11)
1.464(10) [1.456(10)], C(1)-C(13)-C(12) 110.7(6) [110.6(6)],
C(13)-C(12)-C(11) 109.0(6) [106.6(6)], C(10)-C(11)-C(12)
118.0(6) [117.3(7)].
The synthesis of 1 requires a double intramolecular
Friedel-Crafts cyclization of 11a and reduction of the
resulting R-keto groups. Our expectation was that only
heteroannular cyclization would occur and that this
would lead predominantly to bond formation at diaster-
eomeric â-positions 3′ and 4′ in preference to diastere-
omeric R-positions 2′ and 5′, these being adjacent to a
bulky alkyl substituent. This was supported by the
previously reported cyclization of 1,1′-bis(2-carboxyeth-
yl)ferrocene, which ultimately gave an isolated ratio of
1,1′,3,3′- over 1,1′,2,2′-(1,3-propanediyl)ferrocenophanes
of 43:1.18 Treatment of the (R,R)-diacid 11a with PCl3
gave the corresponding diacid chloride, which was added
to 2.2 equiv of SnCl4 at 0 °C. After quenching, the
reaction mixture gave a mixture of acids, revealing that
only a single Friedel-Crafts cyclization had occurred.
As the acids proved unstable, decomposing during
attempted chromatography or recrystallization, they
were directly converted to their corresponding methyl
esters obtained as a 7:37:56 ratio of isomers. Column
chromatography permitted isolation of the least abun-
dant product (Rf ) 0.23, 10% EtOAc/petroleum ether)
identified as 12 by an X-ray crystal structure determi-
nation (Figure 1). The remaining two products eluted
simultaneously (Rf ) 0.13, 10% EtOAc/petroleum ether)
in a good overall yield, and a single recrystallization
from a mixture of these two solvents gave a pure sample
of the major diastereoisomer. Subsequent ionic hydro-
genation and ester hydrolysis was followed by TFAA-
mediated intramolecular Friedel-Crafts cyclization.
This proceeded with excellent selectivity due to the
rigidity imposed by the first formed bridge. Further ionic
hydrogenation gave a ferrocenophane for which the
F igu r e 2. Crystal structures of 1. Selected bond distances
(Å) and angles (deg): C(1)-Fe 2.002(3), C(2)-Fe 2.027(4),
C(5)-Fe 2.005(4), C(1)-C(13) 1.514(5), C(6)-C(11) 1.522,
C(1)-C(13)-C(12) 113.3(3), C(13)-C(12)-C(11) 117.2, C(6)-
C(11)-C(12) 114.0(3).
simplicity of the 1H/13C NMR spectra was consistent
with a doubly bridged C2-symmetric structure, and a
complete stereochemical assignment was made by an
X-ray crystal structure analysis (Figure 2). This re-
vealed the ferrocenophane to be (R,R,pS,pS)-1, thus
proving the structures of 14, 15, and 16, and also the
absolute configuration of these intermediates (Scheme
3). The enantiomeric excess of 16 was determined as
98% using 1H NMR analysis after coupling to (S)-methyl
mandelate as before. The mother liquors from the
isolation of pure 14 were evaporated and found to
contain a 1:1.5 ratio of 14 and 13. As further recrystal-
lization proved unsuccessful in providing a pure sample
of either diastereoisomer, this mixture was carried
through the same series of reactions to give a 1:1.5
mixture of 1 and a new ferrocenophane. This also gave
(18) Rinehart, K. L.; Bublitz, D. E.; Gustafson, D. H. J . Am. Chem.
Soc. 1963, 85, 970.

Synthesis of Ferrocenophanes
Organometallics, Vol. 18, No. 18, 1999 3753
Sch em e 3
Sch em e 4
Sch em e 5
1H/13C spectra consistent with a C2-symmetric structure
which was determined to contain the 1,1′,3,3′-substitu-
tion pattern of 17 by the absence of an NOE between
the hydrogens at positions 2 and 2′ with those at the
remaining cyclopentadienyl ring positions (Scheme 4).
Repeated recrystallization of a mixture of 1 and 17
consistently led to the isolation of pure samples of 1 even
when present as less than 17% of the mixture. As a
consequence, a pure sample of 17 could not be obtained.
These structural determinations enable the following
assignments of selectivity to be made for intramolecular
heteroannular Friedel-Crafts cyclization of 11a .
Sch em e 6
As predicted, this process is regioselective (93:7),
although only poorly diastereoselective (1.5:1) for the
two â-substituted regioisomers. In contrast, the minor
R-substituted regioisomer is formed with good diaste-
reoselectivity. No evidence for homoannular cyclization
was observed. Other Lewis acids including AlCl3, BF3‚
OEt2, TiCl4, and methylaluminum bis(2,6-di-tert-bu-
tylphenoxide)19 all failed to promote significant levels
of cyclization, and Et2AlCl led to a 1:1 mixture of 13
and 14.
This ferrocenophane synthesis methodology was also
applied to the diacid 11b, except that the monobridged
acids resulting from the first SnCl4-promoted Friedel-
Crafts cyclization were not converted into their methyl
esters, but were instead directly reduced with HSiEt3
in TFA. The inseparable products were further cyclized
with TFAA and reduced as before to give an excellent
overall yield of only two ferrocenophanes in a 1:1.5 ratio.
Due to the similarities of their H NMR spectra to those
1
of 17 and 1, they were assigned structures 18 and 19,
respectively, and from this mixture pure 19 was readily
isolated on recrystallization from EtOAc/petroleum
ether (Scheme 5). Further recrystallization of the evapo-
rated mother liquors consistently gave smaller pure
samples of this same isomer. Its structure was assigned
unequivocally by bromine-lithium exchange and addi-
tion of water, which gave the parent ferrocenophane 1.
When instead CO2 was passed through the reaction
mixture following bromine-lithium exchange, an excel-
lent yield of the diacid 20 was obtained after an acidic
workup, a further building block for the synthesis of
functionalized ferrocenophane derivatives (Scheme 6).
As a direct application of ferrocenophane 1, we sought
to investigate the use of its ferrocenium ion as a
potential chiral Lewis acid in the Diels-Alder reaction.
(19) Maruoka, K.; Itoh, T.; Yamamoto, H. J . Am. Chem. Soc. 1985,
107, 4573.

3754 Organometallics, Vol. 18, No. 18, 1999
Locke and Richards
Sch em e 7
In conclusion, this work has described the asymmetric
synthesis of singly bridged ferrocenophanes from R-fer-
rocenyl alcohols, utilizing enantiospecific methanolysis
and further enantiospecific C-C bond forming addition
of a silyl ketene acetal. This methodology is equally
applicable to 1,1′-disubstituted ferrocenes, and the
resulting diacids undergo a highly regioselective and
partially diastereoselective heteroannular Friedel-
Crafts cyclization. Further high-yielding steps have
provided both unfunctionalized 1/17 and functionalized
18/19/20 doubly bridged C2-symmetric ferrocenophanes
of high enantiomeric purity. Although these structures
are not suited for use as a ferrocenium chiral Lewis
acids, the X-ray structure of 1 reveals their potential
as frameworks for novel ligands and materials, on which
we aim to report in due course.
Exp er im en ta l Section
Diethyl ether and tetrahydrofuran were distilled from
sodium benzophenone ketyl. Toluene, dichloromethane, hex-
ane, and ethyl acetate were distilled from calcium hydride.
Diisopropylamine was distilled from sodium hydroxide. Pe-
troleum ether refers to that fraction boiling in the range 40-
60 °C and hexane to the fraction boiling in the range 65.5-70
°C. Column chromatography was performed on Matrix silica
60 (35-70 µm) in 10% EtOAc/40-60 petroleum ether unless
otherwise stated. The reagents BH3‚THF and BH3‚SMe2 were
used as 2 M solutions in THF.
F igu r e 3.
Ferrocenium hexafluorophosphate 21 has been reported
to act in this capacity,20 and the ferrocenium ion of a
singly bridged C2-symmetric [4]-ferrocenophane has also
been shown to catalyze the Diels-Alder reaction be-
tween methacrolein and cyclopentadiene, the product
being obtained in a modest 10% enantiomeric excess.3a
Treatment of 1 with HBF4 gave dark blue crystals of
the ferrocenium salt 22 after a basic workup to ensure
removal of trace acid (Scheme 7). Both this and com-
mercially available ferrocenium hexafluorophosphate 21
were employed as catalysts for this same Diels-Alder
reaction, the results of which are shown in Figure 3.
Compared to the uncatalyzed background reaction,
use of 5 mol % of both 21 and 22 gave a comparable
modest enhancement of rate, although 10 mol % of 22
was required to ensure completion of the reaction within
a reasonable time scale. Unfortunately, for both the
resulting exo:endo (84:16) diastereoisomers, no enanti-
oselectivity was observed as determined by examination
Asym m etr ic Red u ction of F er r ocen yl Keton es. The
oxazaborolidine catalyst was prepared as previously de-
scribed.22 The reductions of 4a -c followed the procedure
previously described for the reduction of 1,1′-disubstituted
ferrocenyl ketones.17
Syn th esis of (R)-P h en ylh yd r oxym eth ylfer r ocen e 5a .
Benzoylferrocene 4a (0.20 g, 0.69 mmol), (S)-R,R-diphenyl
B-methyloxazaborolidine (0.06 g, 0.22 mmol), BH3‚THF (0.14
mL, 0.14 mmol), and BH3‚Me2S (0.28 mL, 0.56 mmol) were
used in the synthesis. Chromatography gave an orange
crystalline solid (0.17 g, 84%): mp 89-91 °C (EtOAc/petroleum
ether); [R]D ) -129 (c 0.09 in C6H6) (lit.11 [R]D ) -85 (c 3.4
23
20
in C6H6)].
Syn th esis of (R)-(4-Br om op h en yl)h yd r oxym eth ylfer -
r ocen e 5b. 4-Bromobenzoylferrocene23 4b (0.46 g, 1.25 mmol),
(S)-R,R-diphenyl B-methyloxazaborolidine (0.11 g, 0.40 mmol),
BH3‚THF (0.27 mL, 0.27 mmol), and BH3‚Me2S (0.55 mL, 1.10
mmol) were used in the synthesis. Chromatography gave an
orange crystalline solid (0.36 g, 77%): mp 105-107 °C (EtOAc/
1
by GC and H NMR of their acetals derived from (R,R)-
2,4-pentanediol.21
25
petroleum ether); [R]D ) +73 (c 0.055 in C6H6); (found C,
Examination of the X-ray structure of 1 reveals a
cyclopentadienyl ring-ring tilt angle of 6.5°, further
opening up exposure to the metal at the side of the
molecule containing the 4/4′ and 5/5′ positions. In
attempting to use the ferrocenium ion of 1 as a chiral
Lewis acid, it was reasoned that association of a
dienophile to this exo face would place it within the C2-
symmetric environment defined by the two phenyl
substituents. However, the equatorial orientation of
these groups in 1 is maintained in solution, as shown
by the coupling constant of 9.8 Hz to the benzylic
methine protons, thus reducing their influence and
possibly explaining the lack of enantioselectivity ob-
served with 22.
54.86; H, 4.20; C17H15FeBrO requires C, 55.02; H, 4.08); νmax
(Nujol)/cm-1 3362 and 1108; δH (400 MHz, CDCl3) 2.38 (1 H,
d, J 3.0, -OH), 4.08-4.14 (4 H, m, Fc × 4), 4.16 (5 H, s, C5H5),
5.34 (1 H, d, J 3.0, FcCHAr-), 7.19 (2H, d, J 8.4, Ar), 7.37
(2H, d, J 8.4, Ar); δC (100 MHz, CDCl3) 66.13 (Fc), 67.80 (Fc),
68.67 (Fc), 68.70 (Fc), 68.89 (C5H5), 71.70 (FcCHAr-), 94.42
(Fc - ipso), 121.58 (Ar - ipso), 128.29 (Ar), 131.67 (Ar), 142.66
(Ar - ipso); m/z (ES) 372.2 (M+, 92), 370.2 (M+, 100).
Syn th esis of (R)-1-Hyd r oxyeth ylfer r ocen e 5c. Acetyl-
ferrocene 4c (1.07 g, 4.69 mmol), (S)-R,R-diphenyl B-methyl-
oxazaborolidine (0.39 g, 1.41 mmol), BH3‚THF (0.94 mL, 0.94
mmol), and BH3‚Me2S (1.90 mL, 3.80 mmol) were used in the
synthesis. Chromatography gave a yellow crystalline solid
(22) Mathre, D. J .; J ones, T. K.; Xavier, L. C.; Blacklock, T. J .;
Reamer, R. A.; Mohan, J . J .; J ones, E. T. T.; Hoogsteen, K.; Baum, M.
V.; Grabowski, E. J . J . J . Org. Chem. 1991, 56, 751.
(23) Tyurin, V. D.; Nametkin, N. S.; Gubin, S. P.; Otmanin, G.;
Sokolovskaya, M. V. Izv. Akad. Nauk SSSR, Ser. Khim. 1968, 1866
(Chem. Abstr. 1968, 70, 20203).
(20) Kelly, T. R.; Maity, S. K.; Meghani, P.; Chandrakumar, N. S.
Tetrahedron Lett. 1989, 30, 1357.
(21) Furuta, K.; Shimizu, S.; Miwa, Y.; Yamamoto, H. J . Org. Chem.
1989, 54, 1481.

Synthesis of Ferrocenophanes
Organometallics, Vol. 18, No. 18, 1999 3755
21
(0.85 g, 79%): mp 70-72 °C (EtOAc/petroleum ether); [R]D
temperature, the resultant yellow solution was acidified with
dilute hydrochloric acid and the product extracted into CH2-
Cl2 (5 mL + 5 mL). The organic phases were combined, dried
(Na2SO4), filtered, and evaporated in vacuo, and the residue
was purified by column chromatography.
) -34 (c 0.07 in C6H6) [lit.11 [R]D ) -31 (c 3.4 in C6H6)].
20
Gen er a l Meth od for th e Meth a n olysis of R-F er r ocen yl
Alcoh ols. The appropriate R-ferrocenyl alcohol (1.0 mmol) was
dissolved in methanol (4.5 mL). To the yellow solution was
added glacial acetic acid (0.5 mL) and the reaction stirred at
room temperature for 24 h. The yellow reaction mixture was
then quenched slowly with saturated NaHCO3(aq) (5 mL) and
extracted with Et2O (5 mL + 1 mL), and the combined organic
phases were washed with NaCl(aq) (5 mL), dried (Na2SO4),
filtered, and evaporated in vacuo.
Syn th esis of (R)-P h en ylm eth oxym eth ylfer r ocen e 6a .
(R)-Phenylhydroxymethylferrocene 5a (1.04 g, 3.56 mmol) was
used in the synthesis. Chromatography gave a yellow crystal-
line solid (1.00 g, 92%): mp 92-94 °C (EtOAc/petroleum ether);
Syn th esis of (R)-2-Ca r boxy-1-p h en yleth ylfer r ocen e 8a .
(R)-3-Ethoxy-3-oxo-1-phenylpropylferrocene 7a (0.33 g, 0.91
mmol) was used in the synthesis. Chromatography gave a
yellow crystalline solid (0.28 g, 92%): mp 99-101 °C (EtOAc/
20
petroleum ether); [R]D ) +97 (c 0.095 in EtOH).
Syn th esis of (R)-1-(4-Br om op h en yl)-2-ca r boxyeth yl-
fer r ocen e 8b. (R)-1-(4-Bromophenyl)-3-ethoxy-3-oxopropyl-
ferrocene 7b (0.30 g, 0.68 mmol) was used in the synthesis.
Chromatography gave an orange crystalline solid (0.23 g,
82%): mp 130-132 °C (EtOAc/petroleum ether); [R]D21 ) +56
(c 0.100 in EtOH); (found C, 55.51; H, 4.40; C19H17BrFeO2
requires C, 55.24; H, 4.16); νmax (Nujol)/cm-1 3420, 1698 and
1106; δH (400 MHz, CDCl3) 2.77 (1 H, dd, J 10.4, 15.8,
-CHHCO2H), 3.10 (1 H, dd, J 4.5, 15.7, -CHHCO2H), 3.88 (1
H, s, Fc), 4.04 (7 H, s, C5H5 and Fc × 2), 4.06 (1 H, s, Fc), 4.10
(1 H, dd, J 4.6, 10.5, FcCHAr-), 7.01 (2 H, d, J 8.4, Ar), 7.31
(2 H, d, J 8.3, Ar); δC (100 MHz, CDCl3) 41.68 (-CH2CO2H),
41.82 (FcCHAr-), 66.75 (Fc), 67.92 (Fc), 68.12 (Fc), 68.48 (Fc),
69.20 (C5H5), 92.29 (Fc - ipso), 120.86 (Ar - ipso), 129.71 (Ar),
131.89 (Ar), 143.29 (Ar - ipso), CdO signal not observed; m/z
(ES) 414.3 (M+, 43), 412.3 (M+, 43), 59.7 (100).
22
[R]D ) +52 (c 0.185 in EtOH).
Syn th esis of (R)-(4-Br om op h en yl)m eth oxym eth ylfer -
r ocen e 6b. (R)-(4-Bromophenyl)hydroxymethylferrocene 5b
(0.36 g, 0.97 mmol) was used in the synthesis. Chromatography
gave a yellow crystalline solid (0.35 g, 94%): mp 148-149 °C
(EtOAc/petroleum ether); [R]D18 ) +48 (c 0.05 in EtOH); (found
C, 56.36; H, 4.64; C18H17BrFeO requires C, 56.13; H, 4.46);
ν
max (Nujol)/cm-1 1073 and 1108; δH (400 MHz, CDCl3) 3.29 (3
H, s, -OCH3), 3.90 (1 H, s, Fc), 4.06 (5 H, s, C5H5), 4.09 (1 H,
s, Fc), 4.14 (1 H, s, Fc), 4.28 (1 H, s, Fc), 4.97 (1 H, s, FcCHAr-
), 7.30 (2 H, d, J 8.4, Ar), 7.50 (2 H, d, J 8.4, Ar); δC (100 MHz,
CDCl3) 57.42 (-OCH3), 67.31(Fc), 68.08 (Fc), 68.47 (2 × Fc),
69.20 (C5H5), 82.45 (FcCHAr-), 90.10 (Fc - ipso), 128.85 (Ar
- ipso), 129.41 (Ar), 131.79 (Ar), 132.92 (Ar - ipso); m/z (ES)
387.5 (MH+, 14), 386.4 (M+, 60), 385.7 (MH+, 74), 384.1 (M+,
100), 153.3 (58), 152.0 (100), 150.0 (64), 121.5 (100) 55.9 (45).
Syn th esis of (R)-1-m eth oxyeth ylfer r ocen e 6c. (R)-1-
Hydroxyethylferrocene 5c (0.85 g, 3.69 mmol) was used in the
synthesis. Chromatography gave an orange oil (0.83 g, 92%);
Syn th esis of (S)-2-Ca r boxy-1-m eth yleth ylfer r ocen e 8c.
(S)-3-Ethoxy-1-methyl-3-oxopropylferrocene 7c (0.84 g, 2.80
mmol) was used in the synthesis. Chromatography gave an
20
orange oil (0.56 g, 74%): [R]D ) +34 (c 0.11 in EtOH).
Gen er a l Meth od for th e Syn th esis of (S)-Meth yl Ma n -
d ela te Ester s. The appropriate ferrocenylpropanoic acid (0.06
mmol) was dissolved in dry CH2Cl2 (3 mL) and cooled to 0 °C
under an atmosphere of nitrogen. Dicyclohexylcarbodiimide
(0.14 mmol), (dimethylamino)pyridine (0.05 mol), and (S)-
methyl mandelate (0.11 mmol) were added to the resultant
yellow solution, which was allowed to stir overnight. The
reaction was quenched with saturated NaHCO3(aq) (3 mL),
and after separation, the organic phase was washed with
saturated NaCl(aq) (3 mL), dried (Na2SO4), filtered, and
evaporated in vacuo. The resultant yellow semisolids were
23
25
[R]D ) +29.6 (c 0.093 in EtOH) [lit.13 [R]D ) +27.5 (c 2.0 in
EtOH)].
Syn t h esis of (R)-3-E t h oxy-3-oxo-1-p h en ylp r op ylfer -
r ocen e 7a . Following the previously reported procedure,8 (R)-
phenylmethoxymethylferrocene 6a (0.09 g, 0.29 mmol), 1-ethoxy-
1-(trimethylsiloxy)ethene (0.18 g, 1.12 mmol), and BF3‚OEt2
(0.05 g, 0.35 mmol) gave, after chromatography, an orange oil
1
23
examined by H NMR spectroscopy to determine the ratio of
(0.10 g, 94%); [R]D ) +53 (c 0.155 in CHCl3).
diastereoisomers.
Syn th esis of (R)-1-(4-Br om op h en yl)-3-eth oxy-3-oxo-
p r op ylfer r ocen e 7b. (R)-(4-Bromophenyl)methoxymethyl-
ferrocene 6b (0.32 g, 0.83 mmol), 1-ethoxy-1-(trimethylsiloxy)-
ethene (0.54 g, 3.37 mmol), and BF3‚OEt2 (0.13 g, 0.92 mmol)
were used in the synthesis. Chromatography gave a yellow
crystalline solid (0.30 g, 82%): mp 111-113 °C (EtOAc/
Data for 8a : Major diastereoisomer, δH (400 MHz, CDCl3)
5.76 (1 H, s, -OCH(CO2CH3)Ph). Corresponding peak for
minor diastereoisomer, 5.80, 96% ee.
Data for 8b: Major diasteroisomer, δH (400 MHz, CDCl3)
3.64 (3 H, s, -CO2CH3), 5.78 (1 H, s, -OCH(CO2CH3)Ph).
Corresponding peaks for minor diastereoisomer, 3.57, 5.82,
96% ee.
Data for 8c: Major diastereoisomer, δH (400 MHz, CDCl3)
2.77 (1 H, dd, J 15.2, 4.6, -CHHCO2-), 5.89 (1 H, s,
-OCH(CO2CH3)Ph). Corresponding peaks for minor diastere-
oisomer, 2.69 (dd, J 15.1, 4.7), 5.87, 92% ee.
Gen er a l Meth od for th e F r ied el-Cr a fts Cycliza tion of
F er r ocen ylp r op a n oic Acid s. The appropriate ferrocenyl-
propanoic acid (1 mmol) was suspended in neat PCl3 (4 mmol)
under an atmosphere of nitrogen and stirred for 30 min. After
this time the ferrocenylpropanoic acid had dissolved to give a
yellow solution of the acid chloride. The excess PCl3 was
removed in vacuo to yield a yellow gum, which was subse-
quently dissolved in dry CH2Cl2 (2 mL). In a separate vessel,
SnCl4 (1.2 mmol) was added to dry CH2Cl2 (2 mL) under an
atmosphere of nitrogen and cooled to 0 °C. The acid chloride
solution was added dropwise to this SnCl4 solution over 5 min.
The resultant red solution was allowed to stir at 0 °C for 15
min, after which the cooling bath was removed and the solution
allowed to stir for a further 5 min before quenching with
saturated NaHCO3(aq) (4 mL). The two phases were separated,
and the aqueous phase was extracted with CH2Cl2 (2 mL). The
organic phases were combined, washed with saturated NaCl-
18
petroleum ether); [R]D ) +78 (c 0.125 in CHCl3); (found C,
57.37; H, 4.99; C21H21FeBrO2 requires C, 57.17; H, 4.81); νmax
(Nujol)/cm-1 1718 and 1108; δH (400 MHz, CDCl3) 1.11 (3 H,
t, J 7.2, -CH3), 2.73 (1 H, dd, J 10.7, 15.3, -CHHCO2Et), 3.04
(1 H, dd, J 4.6, 15.3, -CHHCO2Et), 3.87-3.88 (1 H, m, Fc),
4.04 (5 H, s, C5H5), 3.97-4.05 (5 H, m, Fc × 3 and -OCH2-
CH3), 4.12 (1 H, dd, J 4.6, 10.7, FcCHAr-), 7.01 (2 H, d, J 8.4,
Ar), 7.31 (2 H, d, J 8.4, Ar); δC (100 MHz, CDCl3) 14.52 (-CH3),
41.94 (-CH2CO2Et), 42.26 (FcCHAr-), 60.92 (-OCH2CH3),
66.75 (Fc), 67.80 (Fc), 68.06 (Fc), 68.33 (Fc), 69.09 (C5H5), 92.44
(Fc - ipso), 120.68 (Ar - ipso), 129.81 (Ar), 131.74 (Ar), 143.53
(Ar - ipso), 172.15 (CdO); m/z (ES) 442.3 (M+, 85%), 440.2
(M+, 93), 142.0 (93), 100.8 (100).
Syn t h esis of (S)-3-E t h oxy-1-m et h yl-3-oxop r op ylfer -
r ocen e 7c. (R)-1-Methoxyethylferrocene 6c (0.11 g, 0.45
mmol), 1-ethoxy-1-(trimethylsiloxy)ethene (0.29 g, 1.81 mmol),
and BF3‚OEt2 (0.07 g, 0.49 mmol) were used in the synthesis.
19
Chromatography gave an orange oil (0.13 g, 96%): [R]D
+19 (c 0.105 in CHCl3).
)
Gen er a l Meth od for th e Hyd r olysis of Eth yl 3-F er r o-
cen ylp r op a n oa tes. The appropriate ester (1 mmol) was
suspended in 1:1 MeOH/H2O (2 mL) containing NaOH (1.5
mmol) and heated at reflux overnight. After cooling to room

3756 Organometallics, Vol. 18, No. 18, 1999
Locke and Richards
(aq) (5 mL), dried (Na2SO4), filtered, and evaporated in vacuo,
and the residue was column chromatographed.
requires C, 53.45, H, 4.15); νmax (Nujol)/cm-1 1083; δH (400
MHz, CDCl3) 3.17 (6 H, s, -OCH3), 3.64 (2 H, s, Fc), 3.91 (2
H, s, Fc), 3.97 (2 H, s, Fc), 4.13 (2 H, s, Fc), 4.75 (2 H, s,
FcCHAr-), 7.15 (4 H, d, J 8.4, Ar), 7.43 (4 H, d, J 8.3, Ar); δC
(100 MHz, CDCl3) 55.84 (-OCH3), 66.76 (Fc), 67.36 (Fc), 67.91
(Fc), 67.96 (Fc), 80.73 (FcCHAr-), 88.82 (Fc - ipso), 120.43
(Ar - ipso), 127.93 (Ar), 130.35 (Ar), 139.38 (Ar - ipso); m/z
(ES) 586.3 (47), 585.4 (60), 584.3 (100), 583.4 (60), 581.6 (49).
Syn t h esis of (R,R)-1,1′-Bis(3-et h oxy-3-oxo-1-p h en yl-
p r op yl)fer r ocen e 2a . Following the previously reported
procedure,8 (R,R)-1,1′-bis(phenylmethoxymethyl)ferrocene 3a
(0.33 g, 0.77 mmol), 1-ethoxy-1-(trimethylsiloxy)ethene (0.49
g, 3.06 mmol), and BF3‚OEt2 (0.24 g, 1.69 mmol) gave, after
chromatography, an orange crystalline solid (0.41 g, 98%): mp
Syn th esis of (R)-1,1′-(1-Oxo-3-p h en yl-1,3-p r op a n ed iyl)-
fer r ocen e 9a . (R)-2-Carboxy-1-phenylethylferrocene 8a (0.36
g, 1.08 mmol), PCl3 (0.59 g, 4.29 mmol), and SnCl4 (0.31 g,
1.19 mmol) were used in the synthesis. Chromatography gave
an orange crystalline solid (0.32 g, 94%): mp 202-204 °C
23
(EtOAc/petroleum ether); [R]D ) +1375 (c 0.095 in CHCl3).
Syn th esis of (R)-1,1′-(1-(4-Br om op h en yl)-3-oxo-1,3-p r o-
p a n ed iyl)fer r ocen e 9b. (R)-1-(4-Bromophenyl)-2-carboxy-
ethylferrocene 8b (0.37 g, 0.90 mmol), PCl3 (0.49 g, 3.57 mmol),
and SnCl4 (0.25 g, 0.96 mmol) were used in the synthesis.
Chromatography gave an orange crystalline solid (0.33 g,
93%): mp 239-240 °C (EtOAc/petroleum ether); [R]D24 ) +967
(c 0.115 in CHCl3); (found: C, 57.96; H, 4.06; C19H15FeBrO
requires C, 57.75; H, 3.83); νmax (Nujol)/cm-1 1652; δH (400
MHz, CDCl3) 2.61 (1 H, dd, J 3.3, 10.3, FcCHArCH2-), 3.88
(1 H, dd, J 10.2, 12.9, FcCHArCHH-), 3.93-3.95 (1 H, m, Fc),
4.10-4.09 (1 H, m, Fc), 4.27 (1 H, dd, J 3.2, 12.9 FcCHA-
rCHH-), 4.32-4.34 (1 H, m, Fc), 4.38-4.39 (1 H, m, Fc), 4.50-
4.51 (1 H, m, Fc), 4.58-4.59 (1 H, m, Fc), 4.66-4.67 (1 H, m,
Fc), 5.01-5.02 (1 H, m, Fc), 7.07 (2 H, d, J 8.4, Ar), 7.34 (2 H,
d, J 8.4, Ar); δC (100 MHz, CDCl3) 49.03 (FcCHAr-), 50.14
(FcCHArCH2-), 68.31 (Fc), 68.38 (Fc), 68.74 (Fc), 71.57 (Fc),
72.69 (Fc), 73.41 (Fc), 73.48 (Fc), 73.12 (Fc), 76.79 (Fc - ipso),
91.62 (Fc - ipso), 120.95 (Ar - ipso), 128.63 (Ar), 131.99 (Ar),
142.49 (Ar - ipso), 208.25 (CdO); m/z (ES) 397.3 (MH+, 100),
396.2 (M+, 29), 395.2 (MH+, 74), 394.2 (M+, 13).
21
83-84 °C (EtOAc/petroleum); [R]D ) +95 (c 0.08 in CHCl3).
Syn th esis of (R,R)-1,1′-Bis(1-(4-br om oph en yl)-3-eth oxy-
3-oxop r op yl)fer r ocen e 2b. Using the same method as that
for 2a , (R,R)-1,1′-bis((4-bromophenyl)methoxymethyl)ferrocene
3b (1.32 g, 2.26 mmol), 1-ethoxy-1-(trimethylsiloxy)ethene
(1.45 g, 9.06 mmol), and BF3‚OEt2 (0.71 g, 5.00 mmol) gave,
22
after chromatography, an orange oil (1.50 g, 95%): [R]D
)
+75° (c 0.57 in CHCl3); (found C, 54.93; H, 4.77; C32H32Br2-
FeO4 requires C, 55.19, H, 4.64); νmax (liquid)/cm-1 1738; δH
(400 MHz, CDCl3) 1.02 (6 H, t, J 7.1, -CH3), 2.63 (2 H, dd, J
10.4, 15.2, -CHHCO2Et), 2.85 (2 H, dd, J 8.0, 15.2, -CHHCO2-
Et), 3.66-3.67 (2 H, m, Fc × 2), 3.88-4.00 (12 H, m, Fc × 6,
FcCHArCH2CO2CH2CH3), 6.93 (4 H, d, J 8.4, Ar), 7.27 (4 H,
d, J 8.4, Ar); δC (100 MHz, CDCl3) 15.53 (-CH3), 42.87
(FcCHAr-), 43.48 (-CH2CO2Et), 61.96 (-OCH2CH3), 68.31
(Fc) 69.66 (Fc), 69.97 (Fc), 70.39 (Fc), 93.59 (Fc - ipso), 121.79
(Ar - ipso), 130.86 (Ar), 132.81 (Ar), 144.22 (Ar - ipso), 172.98
(CdO); m/z (ES) 699.3 (MH+, 22), 698.4 (M+, 52), 697.5 (MH+,
68), 696.4 (M+, 100), 695.5 (MH+, 97), 694.3 (M+, 73).
Syn th esis of (S)-1,1′-(1-Meth yl-3-oxo-1,3-p r op a n ed iyl)-
fer r ocen e 9c. (S)-2-Carboxy-1-methylethylferrocene 8c (0.29
g, 1.07 mmol), PCl3 (0.59 g, 4.30 mmol), and SnCl4 (0.31 g,
1.19 mmol) were used in the synthesis. Chromatography gave
an orange crystalline solid (0.25 g, 92%): mp 136-137.5 °C
20
Syn th esis of (R,R)-1,1′-Bis(2-ca r boxy-1-p h en yleth yl)-
fer r ocen e 11a . As previously reported for the racemic series,8
(R,R)-1,1′-bis(3-ethoxy-3-oxo-1-phenylpropyl)ferrocene 2a (6.56
g, 12.19 mmol) gave a yellow crystalline solid after workup
and evaporation of the solvent (5.82 g, 99%): mp 191-193 °C
(EtOAc/petroleum ether); [R]D ) +833 (c 0.17 in CHCl3).
Syn th esis of 1,1′-Bis(4-br om oben zoyl)fer r ocen e 10b.
Following the procedure previously described for the synthesis
of dibenzoylferrocene,24 ferrocene (10.00 g, 53.8 mmol), 4-bro-
mobenzoyl chloride (25.95 g, 118.2 mmol), and AlCl3 (15.77 g,
118.3 mmol) gave dark purple fibrous crystals after recrys-
tallization from THF/petroleum ether (25.81 g, 87%): mp 193-
194 °C; (found C, 51.98; H, 2.68; C24H16Br2FeO2 requires C,
52.21; H, 2.93); νmax (Nujol)/cm-1 1630; δH (400 MHz, CDCl3)
4.52 (4 H, s, Fc × 4), 4.78 (4 H, s, Fc × 4), 7.48 (4 H, d, J 7.5,
Ar), 7.53 (4 H, d, J 7.2, Ar); δC (100 MHz CDCl3) 73.66 (Fc),
74.90 (Fc), 79.69 (Fc - ipso), 127.33 (Ar - ipso), 129.98 (Ar),
131.98 (Ar), 137.97 (Ar - ipso), 197.01 (CdO); m/z (ES) 553.8
(M+, 45), 551.7 (M+, 94), 549.8 (M+, 50), 184.7 (43), 182.7 (45),
156.6 (37), 154.6 (35), 138.7 (100), 93.5 (63).
18
(EtOAc/petroleum ether); [R]D ) +122 (c 0.095 in EtOH).
Syn th esis of (R,R)-1,1′-Bis(1-(4-br om op h en yl)-2-ca r -
boxyeth ylfer r ocen e 11b. Using the same method as that for
11a (R,R)-1,1′-bis(1-(4-bromophenyl)-3-ethoxy-3-oxopropyl)fer-
rocene 2b (2.47 g, 3.55 mmol) gave a yellow crystalline solid
19
(2.14 g, 94%): mp 179-184 °C (EtOAc/petroleum ether); [R]D
) +152 (c 0.05 in EtOH); (found C, 52.79; H, 3.99; C28H24Br2-
FeO4 requires C, 52.53, H, 3.79); νmax (Nujol)/cm-1 1710; δH
(400 MHz, DMSO-d6) 2.58 (2 H, dd, J 10.8, 15.6, -CHHCO2H),
3.78 (2 H, dd, J 4.5, 15.6, -CHHCO2H), 3.65 (2 H, d, J 1.36,
Fc × 2), 3.76 (2 H, dd, J 4.5, 10.6, FcCHAr-), 3.81 (4 H, t, J
1.33, Fc × 4), 4.00 (2 H, d, J 1.32, Fc), 6.95 (4 H, d, J 8.4, Ar),
7.22 (4 H, d, J 8.3, Ar), 12.12 (2 H, s, -CO2H); δC (100 MHz,
DMSO-d6) 42.29 (-CH2CO2H), 42.42 (FcCHAr-), 68.16 (Fc),
69.48 (Fc) 69.85 (Fc), 69.99 (Fc), 94.27 (Fc - ipso), 120.76 (Ar
- ipso), 131.34 (Ar), 132.48 (Ar), 145.57 (Ar - ipso), 174.22
(CdO); m/z (ES) 643.6 (MH+, 0.21), 642.6 (M+, 0.50), 641.6
(MH+, 1.33), 640.6 (M+, 0.58), 60.9 (100).
From the diacids (0.06 mmol), dry CH2Cl2 (4 mL), dicyclo-
hexylcarbodiimide (0.28 mmol), (dimethylamino)pyridine (0.10
mmol), and (S)-methyl mandelate (0.22 mmol), the methyl
mandalate diesters were synthesized as described above.
Data for 11a : Major diastereoisomer, δH (400 MHz, CDCl3)
3.61 (6 H, s, -CO2CH3). Corresponding peak for minor dias-
tereoisomer, 3.54, 94% ee.
Data for 11b: Major diastereoisomer, δH (400 MHz, CDCl3)
5.76 (2 H, s, -OCH(CO2CH3)Ar). Corresponding peak for minor
diastereoisomer, 5.81, 94% ee.
Th e F r ied el-Cr a fts Cycliza tion of 11a . (R,R)-1,1′-Bis-
(2-carboxy-1-phenylethyl)ferrocene 11a (0.96 g, 2.0 mmol) was
suspended in neat PCl3 (20 mL) under an atmosphere of
nitrogen and warmed to 70 °C for 60 min. After this time, the
diacid had dissolved to give a yellow solution of the corre-
Syn th esis of (R,R)-1,1′-Bis(p h en ylm eth oxym eth yl)fer -
r ocen e 3a . 1,1′-Bis(benzoyl)ferrocene 10a (6.03 g, 15.3 mmol),
(S)-R,R-diphenyl B-methyloxazaborolidine (2.54 g, 9.17 mmol),
BH3‚THF (6.13 mL, 6.13 mmol), and BH3‚Me2S (6.11 mL, 12.22
mmol) gave, as previously reported,17 the crude diol as a yellow
solid (5.79 g). Due to the tendency of these diols to form cyclic
ethers during column chromatography, this was instead
subjected directly to methanolysis which, after recrystalliza-
tion from EtOAc/petroleum ether, gave 3a as a yellow crystal-
line solid (4.82 g, 74% from 10a ): mp 104-106 °C (EtOAc/
19
petroleum ether); [R]D ) +87 (c 0.11 in EtOH).
Syn th esis of (R,R)-1,1′-Bis((4-br om op h en yl)m eth oxy-
m eth yl)fer r ocen e 3b. 1,1′-Bis(4-bromobenzoyl)ferrocene 10b
(15.00 g, 27.2 mmol), (S)-R,R-diphenyl B-methyl-oxazaboroli-
dine (4.52 g, 16.32 mmol), BH3‚THF (10.87 mL, 10.87 mmol),
and BH3‚Me2S (21.73 mL, 43.46 mmol) gave the crude diol as
a yellow solid (14.56 g). Methanolysis and recrystallization
from EtOAc/petroleum ether gave 3b as a yellow crystalline
19
solid (13.06 g, 82% from 10b): mp 115-117 °C; [R]D ) +80
(c 0.08 in EtOH); (found C, 53.21; H, 4.14; C26H24Br2FeO2
(24) Rausch, M.; Vogel, M.; Rosenberg, H. J . Org. Chem. 1957, 22,
903.

Synthesis of Ferrocenophanes
Organometallics, Vol. 18, No. 18, 1999 3757
sponding diacid chloride. The excess PCl3 was removed in
vacuo to yield a yellow gum, which was subsequently dissolved
in dry CH2Cl2 (35 mL). In a separate vessel, SnCl4 (1.15 g, 4.4
mmol) was added to dry CH2Cl2 (30 mL) under an atmosphere
of nitrogen and cooled to 0 °C. The acid chloride solution was
added dropwise to this SnCl4 solution over 5 min. The
resultant red solution was allowed to stir at 0 °C for 15 min,
after which the cooling bath was removed and the solution
allowed to stir for a further 5 min before quenching with dilute
HCl(aq) (65 mL). The two resulting phases were separated,
and the aqueous phase was extracted with additional CH2Cl2
(5 mL). The organic phases were combined, washed with dilute
HCl(aq) (2 × 30 mL), dried (Na2SO4), filtered, and evaporated
in vacuo to yield the semicyclized acids as a dark orange
residue (0.81 g). These were dissolved in dry CH2Cl2 (20 mL)
under a nitrogen atmosphere, and the resulting solution was
cooled to 0 °C. To this was added DCC (0.76 g, 3.68 mmol),
DMAP (0.09 g, 0.74 mmol), and dry MeOH (0.15 mL, 3.7
mmol), and the resulting solution was stirred at room tem-
perature overnight. After addition of saturated NaHCO3(aq)
(20 mL), the two resulting phases were separated and the
aqueous phase was washed with additional CH2Cl2 (4 mL).
The organic components were combined, washed with NaCl-
(aq) (20 mL), dried (Na2SO4), filtered, and evaporated in vacuo
to give a dark orange/brown solid.
478.5 (M+, 7). (13: δH (400 MHz, CDCl3) 3.05 (1 H, dd, J 5.7,
15.4), 3.55 (3 H, s), 4.14 (1 H, s), 4.63 (1 H, s), 4.93 (1 H, s) -
other peaks obscured by 14 in mixture).
(pS)-1,1′-((R)-3-P h en yl-1,3-p r op a n ed iyl)-3-((R)-3-m eth -
oxy-3-oxo-1-p h en ylp r op yl)fer r ocen e 15. (pR)-1,1′-((R)-1-
Oxo-3-phenyl-1,3-propanediyl)-3-((R)-3-methoxy-3-oxo-1- phe-
nylpropyl)ferrocene 14 (0.096 g, 0.20 mmol) was dissolved in
1:1 TFA/CH2Cl2 (2 mL) under an atmosphere of nitrogen to
give a red solution. Triethylsilane (0.05 g, 0.43 mmol) was
added quickly to the reaction mixture, which was stirred for
5 min. The resultant dark blue solution was quenched slowly
by the dropwise addition of saturated NaHCO3(aq) (2 mL) and
followed by the addition of CH2Cl2 (2 mL). The organic phase
was separated, washed with saturated NaCl(aq), dried (Na2-
SO4), filtered, and evaporated in vacuo to yield an orange solid.
Recrystallization from EtOAc/petroleum ether gave an orange
21
crystalline solid (0.087 g, 93%): mp 121.5-123 °C; [R]D
)
+9 (c 0.115 in CHCl3); (found C, 74.78; H, 6.09; C29H28FeO2
requires C, 74.99; H, 6.09); νmax (Nujol)/cm-1 1728; δH (400
MHz, CDCl3) 1.75 (1 H, td, J 3.9, 13.1, FcCHPhCH2CHH-),
2.21-2.24 (2 H, m, FcCHPhCH2-), 2.42 (1 H, dt, J 3.2, 14.4,
FcCHPhCH2CHH-), 2.81 (1 H, dd, J 10.1, 15.3, FcCHPhCH-
HCO2CH3), 3.01 (1 H, dd, J 3.2, 10.9, FcCHPhCH2CH2-), 3.08
(1 H, dd, J 5.1, 15.4, FcCHPhCHHCO2CH3), 3.53 (3 H, s,
-OCH3), 3.80 (1 H, m, Fc), 3.95-3.97 (3 H, m, Fc × 3), 4.03 (1
H, dd, J 5.1, 10.1, FcCHPhCH2CO2CH3), 4.07 (3 H, s, Fc × 3),
7.05-7.23 (10 H, m, Ph); δC (100 MHz, CDCl3) 26.61 (FcCH-
PhCH2-), 41.84 (FcCHPh-), 42.73 and 43.35 (FcCH2- and
FcCHPhCH2CO2CH3), 44.17 (FcCHPhCH2CO2CH3), 52.01
(-OCH3), 66.54 (Fc), 67.05 (Fc), 68.22 (Fc), 69.76 (Fc), 70.77
(Fc), 71.80 (Fc), 71.89 (Fc), 87.10 (Fc - ipso), 88.63 (Fc - ipso),
92.94 (Fc - ipso), 126.42 (Ph - para), 126.93 (Ph - para),
127.63 (Ph), 127.96 (Ph), 128.68 (Ph), 128.72 (Ph), 144.54 (Ph
- ipso), 145.79 (Ph - ipso), 172.98 (CdO); m/z (ES) 465.4
(MH+, 34), 464.4 (M+, 100).
(pR)-1,1′-((R)-1-Oxo-3-p h en yl-1,3-p r op a n ed iyl)-2-((R)-3-
m eth oxy-3-oxo-1-p h en ylp r op yl)-fer r ocen e 12. Chroma-
tography gave an orange solid (0.057 g, 6% from 11a ): mp
22
151-154 °C (EtOAc/petroleum ether); [R]D ) -573 (c 0.13
in CHCl3); (found C, 72.76; H, 5.59; C29H26FeO3 requires C,
72.80; H, 5.49); νmax (Nujol)/cm-1 1731 and 1661; δH (400 MHz,
CDCl3) 2.55 (1 H, dd, J 3.1, 10.4, FcCHPhCH2CO-), 2.89 (1
H, dd, J 11.4, 14.9, FcCHPhCHHCO2CH3), 3.29 (1 H, dd, J
3.7, 14.9, FcCHPhCHHCO2CH3), 3.57 (3 H, s, -OCH3), 3.88
(1 H, dd, J 10.4, 13.2 FcCHPhCHHCO-), 4.00-4.01 (1 H, m,
Fc), 4.09-4.10 (1 H, m, Fc), 4.31-4.32 (1 H, m, Fc), 4.36-
4.37 (1 H, m, FcCHPhCHHCO-), 4.41-4.42 (2 H, m, Fc), 4.59
(1 H, dd, J 3.7, 11.3, FcCHPhCH2CO2CH3), 4.63-4.64 (1 H,
m, Fc), 4.97-4.98 (1 H, m, Fc), 7.06 (1 H, t, J 7.3, Ph - para),
7.11-7.27 (9 H, m, Ph); δC (100 MHz CDCl3) 40.55 (FcCH-
PhCH2CO2CH3), 42.27 (FcCHPhCH2CO2CH3), 49.28 (FcCHPh-
), 51.08 (FcCHPhCH2-), 52.12 (-OCH3), 68.27 (Fc), 68.75 (Fc),
71.08 (Fc), 71.31 (Fc), 71.46 (Fc), 73.78 (Fc - ipso), 75.13 (Fc),
75.34 (Fc), 92.97 (Fc - ipso), 93.48 (Fc - ipso), 126.80 (Ph),
126.86 (Ph), 127.17 (Ph), 128.05 (Ph), 128.58 (Ph), 128.99 (Ph),
143.98 (Ph - ipso), 144.68 (Ph - ipso), 172.65 (-CO2CH3),
207.46 (CdO); m/z (ES) 479.6 (MH+, 34), 478.8 (M+, 18), 42.1
(100).
(pS)-1,1′-((R)-3-P h en yl-1,3-pr opan ediyl)-3-((R)-3-car boxy-
1-p h en yleth yl)fer r ocen e 16. (pS)-1,1′-((R)-3-Phenyl-1,3-pro-
panediyl)-3-((R)-3-methoxy-3-oxo-1-phenylpropyl)ferrocene 15
(0.31 g, 0.67 mmol) was suspended in 1:1 THF/H2O (12 mL)
containing LiOH (0.16 g, 6.7 mmol) and stirred at room
temperature for 64 h. The resultant yellow solution was
acidified with dilute HCl(aq) and the product extracted with
CH2Cl2 (24 mL + 2 mL). The organic phases were combined,
dried (Na2SO4), filtered, and evaporated in vacuo to yield a
yellow solid. Recrystallization from hexane/methanol gave a
24
yellow crystalline solid (0.27 g, 90%): mp 179-181 °C; [R]D
) -76 (c 0.100 in EtOH); (found C, 74.67; H, 5.80; C28H26FeO2
requires C, 74.66; H, 5.83); νmax (Nujol)/cm-1 1692; δH (400
MHz, CDCl3) 1.74 (1 H, td, J 3.9, 13.1, FcCHPhCH2CHH-),
2.14-2.26 (2 H, m, FcCHPhCH2-), 2.38 (1 H, d, J 14.4,
FcCHPhCH2CHH-), 2.83 (1 H, dd, J 9.7, 15.7, FcCHPhCH-
HCO2H), 3.00 (1 H, dd, J 3.0, 11.0, FcCHPhCH2CH2-), 3.11
(1 H, dd, J 5.2, 15.6, FcCHPhCHHCO2H), 3.80 (1 H, m, Fc),
3.96-3.97 (3 H, m, Fc × 3), 4.02 (1 H, dd, J 5.3, 9.7,
FcCHPhCHHCO2H), 4.05-4.07 (3 H, m, Fc × 3), 7.02-7.23
(10 H, m, Ph); δC (100 MHz, CDCl3) 26.57, (FcCHPhCH2-),
41.59 (FcCHPh-), 42.48 and 43.28 (FcCH2- and FcCHPhCH2-
CO2H), 44.12 (FcCHPhCH2CO2H), 66.58 (Fc), 67.08 (Fc), 68.19
(Fc), 69.91 (Fc), 70.87 (Fc), 71.71 (Fc), 71.89 (Fc), 87.17 (Fc -
ipso), 88.65 (Fc - ipso), 92.77 (Fc - ipso), 126.42 (Ph - para),
127.01 (Ph - para), 127.61 (Ph), 127.90 (Ph), 128.71 (Ph),
128.74 (Ph), 144.37 (Ph - ipso), 145.72 (Ph - ipso), 177.96
(CdO); m/z (ES) 450.0 (M+, 100), 391.1 (93).
The methyl mandalate ester of 16 was synthesized as
described for 8a -c.
Data for 16: Major diastereoisomer; δH (400 MHz, CDCl3)
5.75 (1 H, s, -OCH(CO2CH3)Ph). Corresponding peak for
minor diastereoisomer, 5.80, 98% ee.
Syn th esis of (R,R,pS,pS)-1,1′-(1-P h en yl-1,3-pr opan ediyl)-
3,3′-(3-p h en yl-1,3-p r op a n ed iyl)fer r ocen e 1. (pS)-1,1′-((R)-
3-Phenyl-1,3-propanediyl)-3-((R)-3-carboxy-1-phenylethyl)fer-
(pR)-1,1′-((R)-1-Oxo-3-p h en yl-1,3-p r op a n ed iyl)-3-((R)-3-
m eth oxy-3-oxo-1-p h en ylp r op yl)fer r ocen e 14. Chromatog-
raphy gave an orange solid (0.76 g, 80% from 11a ) isolated as
a 1.0:1.5 mixture of diastereoisomers 13 and 14. Recrystalli-
zation from EtOAc/petroleum ether gave the major diastere-
oisomer 14: mp 144-148 °C; [R]D20 ) -693 (c 0.105 in CHCl3);
(found C, 72.59; H, 5.77; C29H26FeO3 requires C, 72.80; H,
5.49); νmax (Nujol)/cm-1 1731 and 1652; δH (400 MHz, CDCl3)
2.57 (1 H, dd, J 3.2, 10.3, FcCHPhCH2CO-), 2.81 (1 H, dd, J
9.4, 15.5, FcCHPhCHHCO2CH3), 2.91 (1 H, dd, J 5.9, 15.5,
FcCHPhCHHCO2CH3), 3.52 (3 H, s, -OCH3), 3.67 (1 H, s, Fc),
3.87 (1 H, dd, J 10.3, 12.9, FcCHPhCHHCO-), 4.05-4.09 (2
H, dd and s, J 5.9, 9.4, FcCHPhCH2CO2CH3 and Fc), 4.24 (1
H, dd, J 3.1, 13.0, FcCHPhCHHCO-), 4.29 (1 H, s, Fc), 4.44
(1 H, s, Fc), 4.55 (1 H, s, Fc), 4.59 (1 H, s, Fc), 4.97 (1 H, s, Fc),
7.10-7.23 (10 H, m, Ph); δC (100 MHz, CDCl3) 41.44 (FcCH-
PhCH2CO2CH3), 42.28 (FcCHPhCH2CO2CH3), 49.51 (FcCHPh),
50.28 (FcCHPhCH2-), 52.11 (-OCH3), 67.20 (Fc), 68.25 (Fc),
70.80 (Fc), 71.53 (Fc), 72.29 (Fc), 73.21 (Fc), 73.46 (Fc), 76.21
(Fc - ipso), 92.30 (Fc - ipso), 98.63 (Fc - ipso), 126.82 (Ph),
127.16 (Ph - para), 127.31 (Ph - para), 127.94 (Ph), 128.84
(Ph), 128.95 (Ph), 143.44 (Ph - ipso), 143.88 (Ph - ipso),
172.44 (-CO2CH3), 208.64 (CdO); m/z (ES) 479.4 (MH+, 100),

3758 Organometallics, Vol. 18, No. 18, 1999
Locke and Richards
rocene 16 (0.36 g, 0.80 mmol) was dissolved in dry CH2Cl2 (10
mL) under an atmosphere of nitrogen at room temperature.
TFAA (0.34 g, 1.62 mmol) was added to the resultant dark
orange solution, which was allowed to stir overnight to yield
a dark green solution. The reaction mixture was quenched
slowly by the dropwise addition of saturated NaHCO3(aq) (10
mL). The organic phase was separated, washed with saturated
NaCl(aq) (10 mL), dried (Na2SO4), filtered, and evaporated in
vacuo to yield a yellow/green semisolid (0.35 g). This R-keto-
ferrocenophane was dissolved in 1:1 TFA/CH2Cl2 (10 mL)
under an atmosphere of nitrogen. Triethylsilane (0.19 g, 1.63
mmol) was added quickly to the resultant solution, which was
further stirred for 10 min. The resultant dark blue solution
was quenched slowly by the dropwise addition of saturated
NaHCO3(aq) (10 mL). The organic phase was separated,
washed with saturated NaCl(aq) (10 mL), dried (Na2SO4),
filtered, and evaporated in vacuo to yield a yellow solid.
Chromatography with 3:97 EtOAc/petroleum ether gave a
yellow crystalline solid (0.32 g, 96% from 16): mp 254-256
(90), 165.1 (97), 151.9 (100). Subsequent cyclization with TFAA
(3.49 g, 16.62 mmol) gave two R-keto ferrocenophanes as a
yellow/green impure solid (4.75 g), that was reduced with
triethylsilane (1.91 g, 16.43 mmol) in 1:1 TFA/CH2Cl2 (100 mL)
to give a 1:1.5 ratio of 18 and 19 as a yellow solid (4.05 g, 92%
from the two intermediate trimethylene acids).
Isola t ion of (R,R,p S,p S)-1,1′-(1-(4-Br om op h en yl)-1,3-
p r op a n ed iyl)-3,3′-(3-(4-b r om op h en yl)-1,3-p r op a n ed iyl)-
fer r ocen e 19. Recrystallization from EtOAc/petroleum ether
gave pure 19 as a yellow crystalline solid: mp 228-229 °C;
20
[R]D ) -71 (c 0.205 in CHCl3); (found C, 58.27; H, 4.21;
C
28H24Br2Fe requires C, 58.36; H, 4.21); δH (400 MHz, CDCl3)
1.78 (2 H, td, J 3.3, 13.0, Hd), 2.10-2.24 (4 H, m, Hb and Hc),
2.38 (2 H, brd, J 14.3, He), 2.99 (2 H, brd, J 9.9, Ha), 4.03 (4 H,
s, Hg and Hh), 4.23 (2 H, s, Hf), 7.14 (4 H, d, J 8.4, Ar), 7.30 (4
H, d, J 8.4, Ar); δC (100 MHz; CDCl3) 26.31 (FcCHArCH2-),
43.69 (FcCHAr-), 46.61 (FcCH2-), 69.67 (Fc), 70.96 (Fc × 2),
86.55 (Fc - ipso), 86.98 (Fc - ipso), 120.05 (Ar - ipso), 129.50
(Ar), 131.67 (Ar), 144.76 (Ar - ipso); m/z (ES) 578.2 (M+, 56),
575.9 (M+, 100), 574.2 (M+, 43).
24
°C (EtOAc/petroleum ether); [R]D ) -99 (c 0.185 in CHCl3);
(found C, 80.65; H, 6.02; C28H26Fe requires C, 80.37; H, 6.28);
δH (400 MHz, CDCl3) 1.79 (2 H, td, J 3.5, 11.5, Hd), 2.15-2.26
(4 H, m, Hb and Hc), 2.38 (2 H, brd d, J 14.4, He), 3.04 (2 H, d,
J 9.9, Ha), 4.03 (2 H, s, Hg or Hh), 4.09 (2 H, s, Hg or Hh), 4.25
(2 H, s, Hf), 7.09 (2 H, t, J 7.3, Ph - para), 7.20 (4 H, t, J 7.6,
Ph - meta), 7.28 (4 H, d, J 7.5, Ph - ortho); δC (100 MHz,
CDCl3) 25.98 (FcCHPhCH2-), 43.87 (FcCHPh-), 46.40
(FcCH2-), 69.32 (Fc), 70.41 (Fc × 2), 86.14 (Fc - ipso), 86.99
(Fc - ipso), 125.88 (Ph - para), 127.33 (Ph), 128.24 (Ph),
145.40 (Ph - ipso); m/z (ES) 419.5 (MH+, 40), 418.3 (M+, 88),
102.0 (66), 59.9 (100).
Syn th esis of (R,R,pR,pR)-1,1′-(1-P h en yl-1,3-pr opan ediyl)-
3,3′-(3-p h en yl-1,3-p r op a n ed iyl)fer r ocen e 17. A mixture of
13/14 was carried through the above procedure to give a
mixture of ferrocenophanes from which 1 could be isolated on
recrystallization from EtOAc/petroleum ether. Repeated re-
crystallization of the mother liquors gave a yellow solid
enriched in the minor ferrocenophane 17: (found C, 80.15; H,
6.40; C28H26Fe requires C, 80.37; H, 6.28); δH (400 MHz, CDCl3)
1.80 (2 H, td, J 3.0, 12.9, Hd), 2.11-2.27 (4 H, m, Hb and Hc),
2.50 (2 H, dt, J 3.2, 14.6, He), 2.99 (2 H, dd, J 2.2, 11.6, Ha),
3.98 (2 H, s, Hg or Hh), 4.01 (2 H, s, Hg or Hh), 4.15 (2 H, s, Hf),
7.09 (2 H, t, J 7.3, Ph - para), 7.20 (4 H, t, J 7.5, Ph - meta),
7.28 (4 H, d, J 7.3, Ph - ortho); δC (100 MHz, CDCl3) 25.80
(FcCHPhCH2-), 42.78 (FcCH2-), 43.38 (FcCHPh-), 67.33 (Fc),
70.24 (Fc), 71.52 (Fc), 85.68 (Fc - ipso), 86.67 (Fc - ipso),
124.94 (Ph - para), 126.18 (Ph), 127.29 (Ph), 144.74 (Ph -
ipso).
Isola tion of (R,R,pR,pR)-1,1′-(1-(4-Br om op h en yl)-1,3-
p r op a n ed iyl)-3,3′-(3-(4-b r om op h en yl)-1,3-p r op a n ed iyl)-
fer r ocen e 18. Repeated recrystallization of the mother liquors
gave a yellow solid enriched in the minor ferrocenophane 18,
which was characterized as a mixture of diastereoisomers.
(found C, 58.49; H, 4.39; C28H24FeBr2 requires C, 58.36; H,
4.21); δH (400 MHz, CDCl3) 1.79 (2 H, td, J 2.9, 12.8, Hd), 2.05-
2.23 (4 H, m, Hb and Hc), 2.50 (2 H, dt, J 3.3, 14.6, He), 2.93 (2
H, dd, J 2.3, 11.8, Ha), 3.97 (2 H, m, Hg or Hh), 4.01 (2 H, m,
Hg or Hh), 4.09 (2 H, s, Hf), 7.15 (4 H, d, J 8.4, Ar), 7.31 (4 H,
d, J 8.4, Ar); δC (100 MHz, CDCl3) 25.66 (FcCHArCH2-), 42.58
(FcCH2-), 42.78 (FcCHAr-), 67.13 (Fc), 70.29 (Fc), 71.73 (Fc),
85.68 (Fc - ipso), 86.25 (Fc - ipso), 118.66 (Ar - ipso), 127.94
(Ar), 130.28 (Ar), 143.66 (Ar - ipso).
P r oof of t h e St r u ct u r e of (R,R,p S,p S)-1,1′-(1-(4-
Br om op h en yl)-1,3-p r op a n ed iyl)-3,3′-(3-(4-br om op h en yl)-
1,3-p r op a n ed iyl)fer r ocen e 19. (R,R,pS,pS)-1,1′-(1-(4-Bromo-
phenyl)-1,3-propanediyl)-3,3′-(3-(4-bromophenyl)-1,3-pro-
panediyl)ferrocene 19 (0.050 g, 0.087 mmol) was dissolved in
dry THF (2 mL) under an atmosphere of nitrogen and cooled
to -78 °C. Butyllithium in hexane (0.347 mmol) was added to
the resultant yellow solution, which was stirred at -78 °C for
60 min. The cooling bath was removed and the yellow solution
allowed to warm to room temperature for 15 min. The
resultant dark orange/red solution was quenched with H2O
(2 mL). Standard workup and chromatography with 3:97
EtOAc/petroleum ether gave a yellow crystalline solid (0.033
g, 91%): mp 253-255 °C. The 1H NMR spectroscopic data
obtained were identical to that previously reported for 1.
Syn th esis of (R,R,pS,pS)-1,1′-(1-(4-Ca r boxyp h en yl)-1,3-
p r op a n ed iyl)-3,3′-(3-(4-ca r boxyp h en yl)-1,3-p r op a n ed iyl)-
fer r ocen e 20. (R,R,pS,pS)-1,1′-(1-(4-Bromophenyl)-1,3-pro-
panediyl)-3,3′-(3-(4-bromophenyl)-1,3-propanediyl)ferrocene 19
(0.216 g, 0.375 mmol) was dissolved in dry THF (7 mL) under
an atmosphere of nitrogen and cooled to -78 °C. Butyllithium
in hexane (0.94 mmol) was added to the resultant yellow
solution, which was stirred at -78 °C for 60 min. Dry CO2
was bubbled through the yellow solution for 5 min to give a
yellow suspension. The cooling bath was removed and the
reaction mixture allowed to warm to room temperature before
it was quenched with dilute HCl(aq) (10 mL). Further addition
of Et2O (5 mL) gave a yellow emulsion, which was separated
and filtered in vacuo to yield 20 as a yellow solid (0.183 g,
87%): mp > 300 °C; (found C, 64.07; H, 5.12; C30H26FeO4‚3H2O
requires C, 64.29; H, 5.77); νmax (Nujol)/cm-1 1680; δH (400
MHz, DMSO-d6) 1.78 (2 H, t, J 12.4, Hd), 2.08-2.27 (6 H, m,
Hb, Hc, He), 3.13 (2 H, d, J 10.5, Ha), 4.04 (2 H, s, Hg or Hh),
4.13 (2 H, s, Hg or Hh), 4.39 (2 H, s, Hf), 7.29 (4 H, d, J 8.3,
Ar), 7.41 (4 H, d, J 8.3, Ar), 12.75 (brs, 2 H, -CO2H); δC (100
MHz, DMSO-d6) 26.16 (FcCHArCH2-), 43.93 (FcCHAr-),
Syn th esis of (R,R,pR,pR)-1,1′-(1-(4-Br om op h en yl)-1,3-
p r op a n ed iyl)-3,3′-(3-(4-b r om op h en yl)-1,3-p r op a n ed iyl)-
fer r ocen e 18 a n d (R,R,p S,p S)-1,1′-(1-(4-Br om op h en yl)-
1,3-pr opan ediyl)-3,3′-(3-(4-br om oph en yl)-1,3-pr opan ediyl)-
fer r ocen e 19. Using the methods described for the synthesis
of 1, (R,R)-1,1′-bis(1-(4-bromophenyl)-2-carboxyethylferrocene
11b (5.15 g, 8.04 mmol), PCl3 (80 mL), and SnCl4 (4.61 g, 17.70
mmol) gave 4.93 g of the intermediate semicyclized acids.
Direct reduction with triethylsilane (2.02 g, 17.37 mmol) in
1:1 TFA/CH2Cl2 (80 mL) gave the trimethylene acids as a
yellow solid (4.65 g, 95% from 11b): νmax (Nujol)/cm-1 1708;
m/z (ES) 610.6 (35), 609.7 (41), 608.5 (86), 607.4 (61), 605.9

Synthesis of Ferrocenophanes
Organometallics, Vol. 18, No. 18, 1999 3759
Ta ble 1. Cr ysta llogr a p h ic Da ta for Com p lexes 1
a n d 12
46.50 (FcCH2-), 69.86 (Fc), 71.14 (Fc × 2), 86.66 (Fc - ipso),
87.51 (Fc - ipso), 126.29 (Ar), 128.26 (Ar), 130.14 (Ar), 151.81
(Ar), 168.07 (-CdO); m/z (LSIMS) 506.0 (M+, 4%), 505.0 (M
- H+, 4), 153 (65), 107 (100).
1
12
formula
fw
C
28H26Fe
C58H50Fe2O6
954.68
150(2)
P r ep a r a tion of (R,R,pS,pS)-1,1′-(1-P h en yl-1,3-p r op a n e-
d iyl)-3,3′-(3-p h en yl-1,3-p r op a n ed iyl)fer r ocen iu m Tet -
r aflu or obor ate 22. (R,R,pS,pS)-1,1′-(1-Phenyl-1,3-propanediyl)-
3,3′-(3-phenyl-1,3-propanediyl)ferrocene 1 (0.19 g, 0.045 mmol)
was dissolved in CH2Cl2 (5 mL) and CH3NO2 (2 mL) to yield a
yellow solution. To this was added HBF4 (54% in ether, 0.006
mL, 0.044 mmol), and the resultant dark blue mixture was
stirred for 90 min. The solvent was evaporated in vacuo to
yield a dark blue oil, which was triturated with hexane (2 ×
3 mL). The resultant dark blue semisolid was stirred with Et2O
(5 mL) for 120 min, after which the solvent was decanted to
yield a dark blue semisolid. The oil was dissolved in ni-
tromethane (1 mL) and filtered through Na2SO4 into a vessel
containing Et2O (3 mL), which was cooled at -10 °C overnight.
The resultant blue solid was removed by filtration, dissolved
in CH2Cl2 (5 mL), and quenched with saturated NaHCO3(aq)
(5 mL) (to remove any remaining HBF4). The organic phase
was evaporated in vacuo, and the resultant dark blue solid
was dissolved in CH2Cl2 (1 mL), covered with a layer of hexane
(3 mL), and cooled at -10 °C overnight. The resultant blue
crystals were contaminated with yellow crystals of 1, which
were removed manually. Recrystallization from CH2Cl2/hexane
gave a blue crystalline solid (0.13 g, 57%): mp 218-221 °C;
418.34
150(2)
0.71069
monoclinic
P2(1)
12.911(3)
5.8400(10)
13.436(3)
103.72(3)
984.2(4)
4
temp, K
wavelength, Å
cryst syst
space group
a, Å
0.71069
orthorhombic
P2(1)2(1)2(1)
9.5070(9)
19.9830(16)
23.830(5)
b, Å
c, Å
â, deg
V, Å3
4527.2(10)
4
1.401
0.696
1992
Z
d
calcd, g cm-3
1.412
0.778
440
µ, mm-1
F(000)
cryst size, mm
θ range, deg
no. of reflns coll
no. of indep reflns
0.12 × 0.10 × 0.10
1.97-25.03
4412
0.3 × 0.4 × 0.2
1.99-25.11
18598
6799 (Rint )
0.1414)
2468 (Rint
)
0.0694)
no. of data/restraints/
params
2468/1/262
6799/6/598
GOF on F2
1.008
0.384
final R indices [I > 2σI)
R1 ) 0.0321,
wR2 ) 0.0826
R1 ) 0.0339,
wR2 ) 0.0831
R1 ) 0.0419,
wR2 ) 0.0908
R1 ) 0.1164,
wR2 ) 0.1249
R indices (all data)
21
[R]D ) +400 (c 0.01 in CH2Cl2); (found C, 66.85; H, 5.39;
C
28H26FeBF4 requires C, 66.56; H, 5.20); m/z (APCI) 418
(Mo KR) ) 0.71069 Å). The crystal-to-detector distance was
50 mm, and the detector 2θ swing angle was 20°. Slightly more
than one hemisphere of data were recorded. Following normal
data processing, the space groups were determined as P21 (1)
and P212121 (12) from analysis of the systematically absent
reflections and progression to a smooth refinement. The
structures were solved via direct methods26 and refined by full-
matrix least squares.27 Corrections for absorption were made
using the program DIFABS,28 and the maximum, minimum,
and average correlation factors were 1.048, 0.927, 0.994 (1)
and 1.201, 0.818, 1.002 (12). Non-hydrogen atoms were refined
anisotropically, while hydrogen atoms were placed in calcu-
lated ideal positions. Refinement was based on F2 and involved
a total of 262 (1) and 598 (12) parameters. Crystal data, details
of data collection, and refinement are given in Table 1.
(C28H26Fe+, 100).
Gen er a l Meth od for th e Diels-Ald er Rea ction be-
tw een Meth a cr olein a n d Cyclop en ta d ien e. Methacrolein
(0.021 g, 0.30 mmol) and cyclopentadiene (0.040 g, 0.61 mmol)
were dissolved in dry CH2CH2 (2 mL) under an atmosphere of
nitrogen at room temperature. Either no catalyst, ferrocinium
hexafluorophosphate 21 (0.005 g, 0.015 mmol), or 22 (0.0076
g, 0.015 mmol, 5 mol %, or 0.0152 g, 0.030 mmol, 10 mol %)
was added to the reaction mixture. Samples were taken from
the reaction mixture using a microsyringe, at 1, 3, 6, 21, and
48 h intervals, filtered through an alumina plug (to remove
ferrocinium salts), dissolved in CDCl3 (=1 mL), and examined
by 1H NMR spectroscopy. Then 1.1 equiv (with respect to
methacrolein) of (R, R)-2,4-pentanediol (0.034 g, 0.33 mmol)
and a catalytic quantity of p-TsOH were added to the Diels-
Alder reaction. The resultant solutions were allowed to stir
overnight, after which the solutions were filtered through
alumina plugs to remove any ferricinium salts and p-TsOH.
The resultant solutions were examined directly by both 1H
NMR spectroscopy and gas chromatography.
Ack n ow led gm en t. We are very grateful to F. C.
Brown (Steel Equipment) Ltd. for the generous provi-
sion of a studentship (A.J .L.). We also wish to thank D.
E. Hibbs, M. Light, and M. B. Hursthouse for assistance
with the crystal structure determinations.
Cr ysta l Str u ctu r e Deter m in a tion s. Crystals of com-
plexes 1 and 12 were selected for full structural X-ray analysis.
They had dimensions of 0.12 × 0.10 × 0.10 and 0.3 × 0.4 ×
0.2, respectively, and were mounted with Areldite on glass
fibers. Cell dimensions and intensity data for both crystals
were recorded at 150 K, as previously described,25 using a
FAST TV area detector diffractometer mounted at the window
of a rotating anode. The generator was operated at 50 kV, 50
mA with a graphite monochromated molybdenum anode (λ-
Su p p or tin g In for m a tion Ava ila ble: Text giving full
characterization for 2a , 3a , 5a -9a , 5c-9c, and 11a and details
of the X-ray structure determinations of 1 and 12. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM990171G
(26) Sheldrick, G. M. SHELXS-86. Acta Crystallogr. 1990, A46, 467.
(27) Sheldrick, G. M. SHELXL-93, Program for Crystal Structure
Refinement; University of Go¨ttingen, Germany, 1993.
(25) Danopoulos, A. A.; Wilkinson, G.; Hussain-Bates, B.; Hurst-
house, M. B. J . Chem. Soc., Dalton Trans. 1991, 1855.
(28) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158 (adapted
for FAST geometry by Karaulov, A., University of Wales, Cardiff, 1991).