Study on the synthesis of nonracemic C2-symmetric 1,1′-binaphthyl-2,2′-diyl bridged ferrocene. Stereochemical result of the cross-coupling reactions controlled by Pd(II) or Pd(IV) complex intermediacy

Article abstract of DOI:10.1016/S0022-328X(01)00926-3

Palladium catalyzed Negishi, Suzuki and Stille cross-coupling reactions of enantiopure 2,2′-diiodo-1,1′-binaphthyl with the corresponding 1,1′-dimetalloferrocenes gave the C₂-symmetric binaphthyl bridged ferrocene 1-1,1′-(1,1′-binaphthyl-2,2′-d

Full text of DOI:10.1016/S0022-328X(01)00926-3

Journal of Organometallic Chemistry 637–639 (2001) 318–326
www.elsevier.com/locate/jorganchem
Study on the synthesis of nonracemic C2-symmetric
1,1%-binaphthyl-2,2%-diyl bridged ferrocene. Stereochemical result of
the cross-coupling reactions controlled by Pd(II) or Pd(IV)
complex intermediacy
P. Kasa´k, R. Mikla´sˇ, M. Putala *
Department of Organic Chemistry, Faculty of Natural Sciences, Comenius Uni6ersity, Mlynska´ dolina, SK-842 15 Bratisla6a, Slo6ak Republic
Received 4 January 2001; received in revised form 29 March 2001; accepted 29 March 2001
Abstract
Palladium catalyzed Negishi, Suzuki and Stille cross-coupling reactions of enantiopure 2,2%-diiodo-1,1%-binaphthyl with the
corresponding 1,1%-dimetalloferrocenes gave the C2-symmetric binaphthyl bridged ferrocene 1-1,1%-(1,1%-binaphthyl-2,2%-
diyl)ferrocene (1). The latter was obtained by Stille coupling with the bis(trimethylstannyl) derivative but not with the
bis(tributylstannyl) one. Products of alkyl group transfer from tin to binaphthyl were obtained as the main products in both cases.
The stereochemical result of these cross-coupling reactions in the positions 2 and 2% of 1,1%-binaphthyl depends on the reactivity
of 1,1%-dimetalloferrocenes. Negishi coupling proceeds stereoconservatively (affording enantiopure product 1). Complete racemiza-
tion of binaphthyl moiety occurs during the reactions with less reactive boron and tin organometallics. Proposed different reaction
pathways include C1-symmetric palladium(II) intermediate in the former and configurationally unstable C2-symmetric pal-
lada(IV)cyclic intermediate in the latter cases. In contrast to the cross-coupling reactions, free radical arylation of ferrocene with
enantiopure 1,1%-binaphthyl-2,2%-bisdiazonium salt gave predominantly oligomeric binaphthyl bridged ferrocenes and only traces
of the partially racemized product 1. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Binaphthyl; Cross-coupling; Ferrocene; Mechanism; Palladium complexes; Stereoconservative
1. Introduction
For our study we chose 1,1%-binaphthyl-2,2%-diyl as
the chiral bridge. The synthesis and X-ray study of the
ferrocene derivative 1 was published [3c]. But the origi-
nal synthesis was performed with a racemic substrate -
via Negishi cross-coupling reaction of racemic
2,2%-diiodo-1,1%-binaphthyl (2a) with 1,1%-bis(chlorozin-
cio)ferrocene (3a). Substitution reactions in the posi-
tions 2 and 2% of nonracemic 1,1%-binaphthyl derivatives
[4] are challenging from the stereochemical point of
view since the substitution occurs in the positions where
nonbonding interactions between the substituents are
crucial for the configurational stability of these deriva-
tives. Thus, it is important to investigate whether or not
these substitution reactions can proceed without scram-
bling of enantiomeric purity. There is known just one
stereoconservative cross-coupling reaction in the posi-
tions 2 and 2% of nonracemic 1,1%-binaphthyl deriva-
tives-methylation of 2,2%-ditriflate 2b by methyl-
Nonracemic ansa-metallocenes, especially C2-sym-
metric ones, represent a group of organometallic com-
pounds interesting with respect to potential applications
in stereoselective catalysis [1]. The bridge restricts rota-
tion of the cyclopentadienyl rings and allows one to
precisely design a chiral pocket around the catalytic
center and the C2-symmetry reduces the number of
possible stereoisomers, which simplifies their synthesis
and application. The majority of these nonracemic C2-
symmetric ansa-metallocenes are of early transition
metals. Although the syntheses of several C2-symmetric
ansa-ferrocenes (ferrocenophanes) have been reported
[2,3], only a few of them have been prepared in non-
racemic forms [2].
* Corresponding author. Fax: +421-7-6029-6690.
E-mail address: putala@fns.uniba.sk (M. Putala).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00926-3

P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
319
magnesium halides [5]. In addition, a few other relative
stereoconservative substitutions of nonracemic 1,1%-bi-
naphthyl 2,2%-dielectrophiles (2a, 2b) catalyzed by tran-
sition metal complexes were reported [6].
A wide variety of methods to attach aryl groups
directly to ferrocene have been elaborated:
“ cross-coupling reactions of metalloferrocenes (Li [7],
Mg [7], Zn [8], Hg [9], Sn [10], B [11]) with haloare-
nes, or haloferrocenes with arylboronic acids [12];
“ oxidative coupling of metalloarenes and metallofer-
rocenes or Ullmann coupling [13];
“ reaction of lithioferrocenes with heteroarenes [14];
“ arylation of ferrocene with arenediazonium salts [15],
aryldiazanes (in the presence of AlCl3 or Ag2O) [16],
or chlorobenzene (catalyzed by intramolecular ferro-
cenylphosphane palladium complex) [17];
solvents (THF, PhMe, NMP) were tried. The unreacted
ditriflate 2b was recovered almost quantitatively. Small
amounts of biferrocenyl 5a (5%) were obtained as the
only product.
The original synthesis of racemic 1 from diiodide 2a
with dizinc 3a in the presence of Pd(dppf)Cl2 [3c] was
reported to give 37% yield accompanied with
oligomeric compounds 4 and a small amount of the
biferrocenyl 5. A similar result was obtained in the
synthesis of the analogous 1,1%-(1,1%-biphenyl-2,2%-
diyl)ferrocene [3b] from 2,2%-diiodo-1,1%-biphenyl and
3a (20% yield+oligomers; formation of 5a was not
noticed). We found the result of the former reaction (2a
with 3a) close to the reported one (35% 1+4+1.5%
5a; Table 1, entry 2). Attempts to increase the yield of
1 by further optimization were not successful.
It has to be mentioned that this reaction (2a with 3a)
is quite sensitive to the conditions. The best results were
obtained from dizinc 3a prepared by dilithiation of
ferrocene in the presence of TMEDA, if the latter was
used as received from the supplier (without additional
drying; entry 2). Thorough drying led to a decreased
yield of 1 and an increased amount of biferrocenyl 5a
(entry 3). When we used 1,1%-dibromoferrocene instead
of ferrocene/TMEDA in the reaction with n-butyl-
lithium for the synthesis of 1,1%-dilithioferrocene, the
results were more reproducible but the yield of 1 was
lower (entry 4). The fact that the method of the prepa-
ration of 3a can influence significantly the efficiency of
the cross-coupling of 3a with aryl electrophiles was also
observed in the synthesis of 1,1%-bis(anthracen-9-
yl)ferrocene 3h (35–40% starting from FcBr2 vs. 5%
from FcH/TMEDA).
In order to avoid precautions required for the synthe-
sis and handling of 3a we also examined cross-coupling
reactions with less sensitive 1,1%-metalloferrocenes. Con-
ditions reported for an efficient synthesis of diarylfer-
rocenes from diboronic acid 3b and iodoarenes [11a]
(DME/aqueous NaOH/Pd(dppf)Cl2) in our case yielded
only traces of the desired product 1 and significant
hydrodehalogenation of diiodide 2a (entry 5). Modifica-
tion of the solvent mixed with water, base or ligand did
not improve the result remarkably. This observation is
in accordance with previous attempts to synthesize
2,2%-diaryl-1,1%-binaphthyls via Suzuki reaction from
racemic dibromide 2c [24], where the reaction stops in
the first step, affording predominantly the monoary-
lated product (48–70%, partialy hydrodebrominated)
and only traces of the diarylated product (B3%). We
found that hydrodehalogenation of 2a does not occur
in aprotic solvents. From trial combinations of solvents
(THF, dioxane, DME, PhMe), catalysts precursors
(Ni(dppf)Cl2/BuLi or Zn; Pd(dppf)Cl2; Pd(dba)2 with
dppf, dppe, PPh3, CuI, without ligand; palladacycle 8),
and bases (K2CO3, K3PO4, KF, AcONa), the best result
was obtained in the case of THF/Pd(dba)2/K3PO4; the
yield of 1 rose to 8% (entry 6).
“ photolysis of haloferrocenes or diferrocenylmercury
in the presence of arenes [18];
“ photolysis and thermal decomposition of dicar-
bonyl(h5 -cyclopentadienyl)(h1 -arenecarbonyl)iron
(Ar–CO–Fp) [8h];
“ synthesis of arylcyclopentadienyl ligand followed by
metallation [19].
However, the yields of arylferrocenes are moderate at
best (10–60%), and only a few cross-coupling reactions
exceed the given range.
The choice of synthetic methods for our study was
limited also by availability of 1,1%-binaphthyl-2,2%-diyl
precursors in an enantiopure form. The following 2,2%-
dielectrophiles are readily accessible:
“ ditriflate 2b from commercially available enantiopure
1,1%-binaphthyl-2,2%-diol (BINOL) [20], or in one ad-
ditional step starting from 2-naphthol [21] and sim-
ple resolution of BINOL [22];
“ dibromide 2c and diiodide 2a in three steps from
2-naphthol [23], including simple resolution of 2,2%-
diamine [23];
“ also bisdiazonium salt 2d can be considered; it is
formed as an intermediate in the synthesis of di-
halides 2a and 2c [23].
The synthesis of suitable nonracemic 2,2%-dimetallo-
1,1%-binaphthyls has not been reported [4].
2. Results and discussion
2.1. Synthesis of racemic 1
In agreement with the general trend in the reactivity
of aryl electrophiles in cross-coupling reactions (OTfB
BrBI), we found that the ditriflate 2b, the most easily
accessible of 1,1%-binaphthyl 2,2%-dielectrophiles 2, is the
least reactive one (in a cross-coupling reaction with
dizinc 3a). The product 1 was not obtained, even a
variety of different reaction conditions, catalysts (nickel
and palladium complexes with dppf, dppe and PPh3),

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P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
The diboronic acid 3b is sparingly soluble in aprotic
vents; entry 8). Use of CuO as a cocatalyst to
Pd(dba)2/4 PPh3 (in analogy to Refs. [10a,10e]; entry 9)
led to a transfer of the butyl group to binaphthyl.
Although the Stille cross-coupling reaction was found
to be effective in the synthesis of arylferrocenes [10], it
is apparently significantly sensitive to steric factors.
Indeed, use of the less hindered bis(trimethylstannyl)
derivative 3e (entry 10) afforded the desired product 1
(11%) accompanied with methylation products 6c and
7c in addition to oligomers 4.
Cross-coupling of the diiodide 2a with dicopper 3f
(entry 11) and dimercury 3g (entry 12) did not proceed
under any conditions. The dicopper 3f was almost
quantitatively transformed by to biferrocenyl 5a and
oligomeric ferrocenes 5b (terferrocenyl was identified
among them).
The possible application of bisdiazonium salt 2d in
the synthesis of 1 would save one step in the synthesis
of the binaphthyl precursor, but for this reaction only
its decomposition under catalytic conditions was ob-
served. We applied it therefore in situ to a direct
arylation of ferrocene 3h (entry 13). This reaction gave
just traces of the desired product 1 (2%). The rest of
binaphthyl precursor 2d was transformed to oligomers
4—with a significant predominance of oligomers 4 over
organic solvents. Therefore we tried to use the more
soluble diboronate 3c. The optimized conditions were
found to be the same as for 3b, to afford the desired
product 1 in 12% yield (entry 7).
In the reactions with 3b as well as its ester 3c the
formation of 1 was accompanied by the oligomers 4,
but 5a was not detected (with the exception of when
Pd(dba)2/CuI or palladacycle 8 were used as catalysts).
The relatively low efficiency of the Suzuki cross-cou-
pling reaction for our system was quite surprising be-
cause it was reported that the Suzuki reaction gives
good results in the synthesis of hindered biaryl com-
pounds [25]. Most probably in our binaphthyl system,
the steric hindrance exceeded the limit, below which it
is still viable (bulky 2-substituted 1-naphthyl sub-
stituent in ortho-position to iodine). This assumption is
supported also by the fact that the yield of 1 was higher
in the reactions where no phosphine ligand on palla-
dium was used, giving a possibility to form less hin-
dered, more catalytically active palladium species. On
the other hand palladium species not stabilized with
phosphine ligands were more labile. As evidenced by
the precipitation of black palladium(0) powder and low
conversion of diodide 2a during these reactions. Never-
theless, this is the highest yield of 2,2%-diarylated-1,1%-bi-
naphthyl obtained by Suzuki couplings yet.
product
1 in comparison to the cross-coupling
reactions.
Stille coupling of diiodide 2a with bis(tributylstannyl)
derivative 3d did not occur under the examined condi-
tions (reflux, various Pd-catalysts, additives and sol-
We did not give special attention to oligomers 4,
since they have been already characterized [3c], their
isolation is problematic (mixture, low retention factors,
Table 1
Synthesis of racemic 1
Precursor of
Binaphthyl
Solvent/additive
Temp./time (d) Conv. c (%) Isolated yield (%)
Ferrocene a
Catalyst b
1 d
5a
6/7
1
2
3
4
5
6
7
8
9
2b X=OTf 3a M=ZnCl e
various Ni, Pd
Pd(dppf)Cl2
Pd(dppf)Cl2
Pd(dppf)Cl2
Pd(dppf)Cl2
various
THF
THF
reflux/6
r.t./3
r.t./3
5–10
100
–
35
10–15
26
2
8
12
–
–
11
–
–
2
5
1.5
10–40
B2
–
–
–
–
–
–
–
–
–
2a X=I
3a e
2a
2a
2a
2a
2a
2a
2a
3a f
100
100
85
40
50
5
100
95
5
3a g
THF
r.t./3
3b M=B(OH)2
3b
3c M=B(OR)2
3d M=SnBu3
3d
DME–H2O/NaOH reflux/6
38/9 (a)
–
–
–
50/8 (b)
46/6 (c)
–
–
–
h
Pd(dba)2
Pd(dba)2
THF/K3PO4
THF/K3PO4
various
reflux/1
reflux/1
reflux/3
100 °C/0.5
reflux/2
r.t./1
h
various Pd
Pd(dppf)Cl2/CuO DMF
Pd(dba)2/4 PPh3 THF/LiCl
10 2a
11 2a
3e M=SnMe3
3f M=Cu·SMe2 no or various Pd THF
3g M=HgCl
3h M=H
–
92 i
–
12 2a
Pd(dba)2/4 PPh3
–
Me2CO–THF/NaI reflux/1
50% H2SO4 aq. 0 °C/1
5
100
13 2d X=N+2
–
a Two equivalents to 2.
b 10 mol% to 2 (5 mol% to C–X).
c Based on isolated 2.
d Accompanied with 4, yield of pure 1 is given.
e Prepared from FcH/2.25 equivalents BuLi/2.25 equivalents of commercial TMEDA, then 2.25 equivalents ZnCl2.
f Prepared from FcH/2.25 equivalents BuLi/2.25 equivalents dried and distilled TMEDA, then 2.25 equivalents ZnCl2, thoroughly dried.
g Prepared from 1,1%-dibromoferrocene/three equivalents BuLi, then two equivalents ZnCl2.
h Black precipitate of Pd(0) was formed during the reaction.
i Including 5b.

P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
321
Scheme 1.
bad separation) and they do not significantly contribute
to the scope of the present work. Yet the formation of
certain amount of oligomers 4 is understandable since
the product 1, in contrast to oligomers 4, contains
internal strain (both binaphthyl and ferrocene frag-
ments are distorted in the molecular structure of 1 [3c])
(Scheme 1).
Product (S)-1 is oxidized easily by either silver triflate
or nitrosonium tetrafluoroborate, affording corre-
sponding nonracemic ferrocenium salt (S)-9 in a high
yield.
2.3. Proposed mechanism for cross-coupling reaction
from 2a and palladium intermediates
2.2. Synthesis of nonracemic 1
There have to be different pathways considering that
the stereochemical results of Negishi versus Suzuki and
Stille coupling yielding 1 are so different. If we consider
methylation to 6c (stereoconservative in Grignard cou-
pling [5] and with complete racemization in Stille cou-
pling by us), there is an apparent connection between
the reactivity of the organometallic counterpart (Mg\
Zn\SnꢀB) and the stereochemical result. Thus, the
following mechanism can be proposed (Scheme 3). The
first step is common-an oxidative addition of 2a to the
palladium complex (insertion of palladium to C–I bond
of 2a in position 2) giving palladium(II) complex 10,
analogous to usual intermediates in cross-coupling reac-
tion from aryl halides [26]. If the 1,1%-dimetallofer-
rocene is sufficiently reactive (dizinc 3a), trans-
metallation can take a place and the first C–C bond is
formed. A C–C bond in position 2% is formed
analogously. In such a mechanism there is no reason
for racemization, and product 1 is obtained enantiop-
ure-with complete conservation of stereogenic informa-
tion from substrate.
If the organometallics are less reactive (e.g. B 3b and
3c, and Sn 3e), transmetallation is slower than insertion
of palladium in 10 to C–I bond in the position 2% to
form a palladacyclic complex 11 containing palladiu-
m(IV). It is known that 1,1%-binapthalene derivatives
having positions 2 and 2% bridged with one-atom linker
have a low racemization barrier (between 45 and 65 kJ
mol−1 [27]) because there are not nonbonding interac-
tions in positions 2 and 2% (ring flipping of fused
unsaturated five-membered ring requires only low acti-
We examined the conservation of the stereogenic
information (stereoconservativity) from the binaphthyl
precursor 2 to product 1 for all synthetic approaches
that succeed to give 1. While Negishi cross-coupling
reaction of (S)-2a with 3a afforded enantiopure (S)-1
(\95% e.e., determined by HPLC), Suzuki and Stille
couplings with corresponding 1,1%-dimetalloferrocenes
3b, 3c and 3e yielded practically racemic 1. Also the
dimethyl derivative 6c obtained as a main product in
Stille cross-coupling with 3e was found to be racemic.
The same stereochemical result of Suzuki coupling
(complete racemization of binaphthyl moiety during the
reaction) was observed when this reaction was run at
room temperature (as was Negishi coupling) or in the
presence of the phosphine ligand (PPh3), although the
yields were lower.
An approach using the bisdiazonium salt 2d and
ferrocene 3h gave product 1 with partial conservation
of stereogenic information from 2d. This stereochemical
result together with the observed predominance of
oligomers 4 over monomer 1 in this reaction, in our
opinion, supports a free radical mechanism for aryla-
tion of ferrocene by arenediazonium salts [15m]. Con-
sidering an alternative mechanism based on primary
orbital interaction of diazonium salt with ferrocene iron
[15k], we see no apparent reason for which partial
racemization of the binaphthyl moiety occurs. The for-
mation of the desired product 1 should be especially
disfavored over oligomers 4 (Scheme 2).

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P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
Scheme 2.
Scheme 3.
vation energy) and also nonbonding interactions in
positions 8 and 8% are decreased (the outer benzene
rings of naphthalene units are dragged away). Thus, the
binaphthyl moiety is easily racemized in this step. The
palladacyclic complex 11 is not necessary an intermedi-
ate, this can be also considered as an activated com-
plex, through which either reversible migration of
palladium from position 2 to 2% accompanied by racem-
ization can occur or the reactivity of binaphthyl–palla-
dium species towards transmetalation can be increased.
Then, after transmetallation and formation of C–C
bonds in the both 2 and 2% positions, racemic products
1 and 6c are formed.
We gained additional information about palladium
intermediates from the reaction of diiodide 2a with
Pd(dba)2 and dppf (1:1:1) in dioxane. When the reac-
tion was run at room temperature, we isolated a com-
plex with proposed structure 10. It exhibits two broad
signals in 31P-NMR spectrum (C1-symmetry) at 28.3
and 24.9 ppm in CDCl3 (possibly 10a) or 34.6 and 28.7
in dioxane/CDCl3 mixture (possibly 10b). The observed
values are comparable to those of other Pd(dppf)Ar(I)
complexes (8–30 ppm [28]). Also the signals in 1H-
NMR spectrum were broad, probably due to fluxional
behavior of this complex. hx-Coordination (x=2 or
more) of palladium to the neighboring naphthalene unit
(as shown in 10a) was observed in some palladium [29]
and ruthenium [30] binaphthyl complexes. Additional
stabilization of coordinationally unsaturated palladiu-
m(II) intermediates of cross-coupling reactions by sol-
vent (as in 10b) was reported in recent mechanism
revising study [26a].
When the reaction mentioned above was performed
in boiling dioxane, it resulted in another palladium
complex, quite unstable under inert conditions, most
probably 11. It exhibits C2-symmetry—a single signal
in 31P-NMR spectrum (27.1 ppm). Another alternative
C2 - symmetric structure that should be considered as a
possible intermediate is 12. The formation of complex
12 instead of 11 is less probable especially in the course
of a catalytic reaction, if the high ratio of C–I bonds
(in 2a) to palladium precursor 20:1 in the reaction

P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
323
3.1. 1,1%-bis(1,3,2-Dioxaborolane-2-yl)ferrocene (3c)
mixture is taken into account. An additional factor in
favor of structure 11 over 12 is the expected higher
difference of its activity towards transmetallation
compared to 10. At the same time, complex 11
should be less configurationally stable than 12 (its
structure gives a more acceptable explanation for the
observed complete racemization of the binaphthyl
moiety). All known examples of lowered configura-
tional stability of 2,2%-substituted 1,1%-binaphthyl
derivatives are limited to those that have a bonding
interaction between the positions 2 and 2% [4]. In any
case, organopalladium(IV) complexes are accepted as
possible intermediates in some palladium-catalyzed
processes [31], for instance in Heck couplings [32].
Some arylpalladium(IV) complexes stabilized with
dinitrogen ligand were isolated [33]. The first Pd–
arylphosphapalladacycle containing palladium(IV) was
characterized recently [31b], but NMR data were not
given. Further characterization of complexes 10 and
11 is under way and will be reported later.
A mixture of ferrocene-1,1%-diboronic acid (3b, 2.75
g, 10 mmol) and ethane-1,2-diol (1.25 ml, 22 mmol) in
benzene (30 mol) was heated to reflux with azeotropic
removal of water for 20 h. The solvent was evaporated
and the residue crystallized from toluene/hexanes mix-
ture. Product 3b was obtained as an orange crystalline
solid (3.08 g, 95%), m.p. 160–163 °C. Anal. Calc.: C,
51.80; H, 4.93; Found: C, 51.52; H, 4.90%. H-NMR
(CDCl3), l: 4.42 (br s, 4H, Cp-a), 4.40 (br s, 4H, Cp-b),
4.36 (s, 8H, OCH2) ppm.
1
3.2. (S)-1,1%-(1,1%-Binaphthyl-2,2%-diyl)ferrocene (1)
3.2.1. Negishi coupling (Table 1, entry 2)
A solution of 1,1%-bis(chlorozincio)ferrocene (3a, 4.5
mmol, prepared as in Ref. [3c]) in THF (20ml) was
added to a suspension of (S)-2,2%-diiodo-1,1%-binaphthyl
((S)-2a, 0.984 g, 1.94 mmol) and Pd(dppf)Cl2 (0.146 g,
0.2 mmol) in THF (10 ml). The resulting dark red–
brown reaction mixture was stirred for 72 h at room
temperature (r.t.), then poured into 10% aqueous HCl
(100 ml), and extracted twice with dichloromethane
(2×100 ml). The combined extracts were washed with
water and dried over anhydrous magnesium sulfate.
After removal of the solvent under vacuum, the residue
was purified by flash chromatography on silica gel,
eluted first with isohexane up to elution of ferrocene.
Following elution with isohexane:dichloromethane mix-
ture 9:1 (v/v) gave (S)-1 together with a small amount
of 5a (orange, the second colored band). Crystallization
from hexane gave pure (S)-1 (0.297 g, 35% yield,
\95% e.e.) as an orange crystalline solid.
3. Experimental
All cross-coupling experiments were performed in
dried deoxygenated solvents under argon atmosphere
using Schlenk technique, protected from the light.
Pd(dba)2 [34], Pd(dppf)Cl2 [35], palladacycle 8 [36],
(RS)- and (S)-2,2%-diamino-1,1%-binaphthyl [23], (RS)-
2a and (S)-2a [23]; (RS)-2b [20], 1,1%-dibromofer-
rocene [37], 3a from ferrocene/BuLi/TMEDA [3c] and
1,1%-dibromoferrocene/BuLi [8h], 3b [11a], 3d [38], 3e
[39], 3f [40], and 3g [41] were prepared according to
the literature procedures. LiCl, NaI, KF, K3PO4, and
ZnCl2 were dried prior to use.
Melting points were measured on a Kofler block
and are uncorrected. IR spectra were recorded on a
Specord M 80 spectrophotometer, UV–vis spectra on
a Hewlett Packard 8452A instrument. NMR spectra
were measured on a Varian Gemini 300 instrument:
1H-NMR (300 MHz) and 13C-NMR (75.5 MHz) in
CDCl3 with tetramethylsilane as an internal standard,
31P-NMR (121.5 MHz) with conc. H3PO4 as an exter-
nal standard. Flash column chromatography was per-
formed on 30–60 mm silica gel and thin-layer
chromatography (TLC) on Silufol UV 254 foils.
HPLC separation was done on a Chiracel OJ (Diacel)
column with 1% propane-2-ol in methanol as an elu-
ent, with UV detection at 254 nm. Specific optical
rotation was measured on a Perkin–Elmer 241 polar-
imeter at 22 °C. Elemental analysis was determined
on an Erba Science 1106 instrument, atomic ab-
sorbance spectroscopy (AAS) on a Perkin–Elmer
1100 instrument.
The value of specific rotation corrected with respect
to the contents of 1 in its mixture with 5a after chro-
matography before crystallization (found from 1H-
NMR spectrum) compared with that of crystallized
pure 1 showed that e.e. of 1 was not affected by the
crystallization.
3.2.2. Suzuki coupling (Table 1, entry 7)
A suspension of (S)-2a (0.253 g, 0.5 mmol), 1,1%-
bis(1,3,2-dioxaborolane-2-yl)ferrocene (3c, 0.325 g, 1
mmol), Pd(dba)2 (0.029 g, 0.05 mmol), K3PO4 (1.06 g, 5
mmol) in THF (5 ml) was heated to reflux for 24 h.
Reaction mixture cooled to r.t. was diluted with
dichloromethane (25 ml), extracted with 10% aqueous
NaHCO3, washed with water and brine, and dried over
anhydrous magnesium sulfate. After removal of the
solvent under vacuum, the residue was chro-
matographed on flash silica gel. Elution with isohex-
ane:dichloromethane 19:1 allowed isolation of
unreacted (S)-2a (0.251 g, 50%). Following elution with
isohexane:dichloromethane 9:1 gave, after evaporation,
racemic 1 (orange, the first colored band; 0.026 g, 12%
yield, B1% e.e.).

324
P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
ing). Polarimetry, (S)-1: [h]D= −1165930° cm2 g−1
dm−1 (c=0.15, CHCl3).
3.2.3. Stille coupling (Table 1, entry 10)
A solution of 1,1%-bis(trimethylstannyl)ferrocene (3e,
1.022 g, 2 mmol) in THF (10 ml) was added via syringe
to the suspension of (S)-2a (0.506 g, 1 mmol), Pd(dba)2
(0.058 g, 0.1 mmol), PPh3 (0.104 g, 0.4 mmol) and LiCl
(0.133 g, 3 mmol) in THF (5 ml) and the reaction
mixture was heated to reflux for 48 h. Subsequently, it
was cooled to r.t., diluted with dichloromethane (50
ml), washed with 10% aqueous HCl, twice with water,
then with brine, and finally dried over magnesium
sulfate. After removal of the solvent under vacuum, the
residue was chromatographed on flash silica gel. Elu-
tion with isohexane allowed isolation of racemic 2,2%-
dimethyl-1,1%-binaphthyl (6c, 0.129 g, 46%, 0% e.e.),
2-iodo-2%-methyl-1,1%-binaphthyl (7c, 0.24 g, 6%), unre-
acted (S)-2a (0.024 g, 5%). Following elution with
isohexane:dichloromethane 9:1 gave after evaporation
racemic 1 (orange, the first colored band; 0.048 g, 11%
yield, 0% e.e.).
3.3. (S)-1,1%-(1,1%-Binaphthyl-2,2%-diyl)ferrocenium
tetrafluoroborate (9)
A solution of (S)-1 (0.078 g, 0.18 mmol) in
dichloromethane (2 ml) was added to the solution of
NOBF4 (0.021 g, 0.18 mmol) in dichloromethane (3
ml). The reaction mixture turned brown immediately;
the reaction was accompanied with gas evolution. The
reaction mixture was stirred for 1.5 h at r.t., filtered,
and the solvent was evaporated. The residue was
washed with methanol, ether, and dried in vacuum.
Ferrocenium salt (S)-9 was obtained as a dark brown
powder (0.083 mg, 88% yield). M.p. 267–268 °C with
decomposition. Anal. Calc.: Fe, 10.68; Found: Fe,
10.22%. UV–vis (CHCl3), u (log m): 248 (1.85), 293
shoulder, 332 shoulder nm (log m2 mol−1). IR
(CHCl3), w: 1635, 1610, 1520, 1480, 1390, 1080 br, 880,
845, 765 cm−1. Polarimetry (S)-9: [h]D= −865950°
deg cm2 g−1 dm−1 (c=0.1, CHCl3).
3.2.4. Free radical arylation (Table 1, entry 13)
A solution of NaNO2 (0.37 g, 5.37 mmol) in water
(2.5 ml) was slowly added to the solution of (S)-2,2%-di-
amino-1,1%-binaphthyl (0.51 g, 1.79 mmol, 91% e.e.) in
50% aqueous H2SO4 (10 ml) at −10 °C and the result-
ing mixture was stirred for 45 min bellow −5 °C.
Then, saturated aqueous solution of urea (0.107 g, 1.79
mmol) was added. This mixture was stirred for addi-
tional 30 min bellow −5 °C and added at once to the
ice-cooled dark blue solution of ferrocene (3h, 0.667 g,
3.58 mmol) in 50% aqueous H2SO4 (prepared as fol-
lows: a mixture of ferrocene in conc. H2SO4 (1.5 ml)
was left standing overnight at r.t. and then poured into
water (1.5 ml). The reaction mixture turned green–
brown, and formation of dinitrogen was observed
(foaming). The reaction mixture was stirred for 2 h at
0 °C, then allowed to warm to r.t. and stirred
overnight. Afterwards, the solution of K2S2O5 (0.89 g, 4
mmol) in water (10 ml) was added. The resulting mix-
ture was stirred for 30 min, and extracted with
dichloromethane (2×50 ml). The combined organic
extracts were washed with 10% aqueous NaHCO3 solu-
tion, water, dried over magnesium sulfate. After evapo-
ration of the solvent, the residue was chromatographed
on flash silica gel, eluted first with isohexane:
dichloromethane mixture 19:1 (v/v), after elution of 1
(second colored band) with dichloromethane. Unre-
acted ferrocene (3h, 0.092 g, 14%), (S)-1 (0.016 g, 2%,
24% e.e.), and mixture of oligomers 4 (0.420 g) were
obtained one after the other.
3.4. Palladium complexes
3.4.1. Compound 10a (assumed as)
A solution of 2a (12.6 mg, 0.025 mmol) in dioxane
(0.5 ml) was added to a solution of Pd(dba)2 (14.4 mg,
0.025 mmol) and dppf (13.8 mg, 0.025 mmol) in diox-
ane (0.5 ml) and the resulting solution was stirred for 5
h at r.t. The solution was concentrated under vacuum
and hexane was allowed to diffuse into it. Mother
liquor was removed, the residue was washed with hex-
1
ane and dried under vacuum. H-NMR (CDCl3): broad
multiplets in Ar and Fc regions. 31P-NMR (CDCl3), l:
28.3, 24.9 ppm (broad singlets).
3.4.2. Compound 10b (assumed as)
A solution of 2a (12.6 mg, 0.025 mmol) in dioxane
(0.3 ml) was added to a solution of Pd(dba)2 (14.4 mg,
0.025 mmol) and dppf (13.8 mg, 0.025 mmol) in diox-
ane (0.2 ml) in a NMR tube and left for 5 h at r.t. Then
CDCl3 was added (0.5 ml). 31P-NMR (dioxane/CDCl3,
1:1), l: 34.6, 28.7 ppm (broad singlets).
3.4.3. Compound 11 (assumed as)
A solution of 2a (12.6 mg, 0.025 mmol) in dioxane
(0.3 ml) was added to a solution of Pd(dba)2 (14.4 mg,
0.025 mmol) and dppf (13.8 mg, 0.025 mmol) in diox-
ane (0.2 ml) and the resulting solution was heated 5 h
to reflux. Then it was transferred to a NMR tube and
CDCl3 was added (0.5 ml) to it. 31P-NMR (diox-
ane:CDCl3, 1:1), l: 27.1 ppm (broad singlet).
1: 1H- and 13C-NMR spectra were in good agreement
with Ref. [3c], elemental analysis was satisfactory. TLC:
RF=0.47 (isohexane:dichloromethane 9:1). HPLC sep-
aration (retention times, flow 0.70 ml min−1): 13.9 min.
(−)-(S)-1, 18.7 (+)-(R)-1 (peaks were partially tail-

P. Kasa´k et al. / Journal of Organometallic Chemistry 637–639 (2001) 318–326
325
(d) B.M. Foxman, D.A. Gronbeck, M. Rosenblum, J.
Organomet. Chem. 413 (1991) 287;
Acknowledgements
(e) Ref. 3b;
(f) Ref. 3c;
This work was partially supported by the Slovak
National Grant Agency, grant no. 1/4167/97 and 1/
7013/20, and by the Comenius University, Grant for
Young Scientists, no. UK/1528/97, /3904/98, /3724/99,
(g) J.G.P. Delis, P.W.N.M. van Leeuwen, K. Vrieze, N. Veld-
man, A.L. Spek, J. Fraanje, K. Goubitz, J. Organomet. Chem.
514 (1996) 125;
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K.M.A. Malik, J. Organomet. Chem. 540 (1997) 27;
(i) M. Iyoda, T. Kondo, T. Okabe, H. Matsuyama, S. Sasaki, Y.
Kuwatani, Chem. Lett. (1997) 35;
&
/79/2000, /80/2000. The authors are thankful to Dr S.
Vyskocˇil (Charles University, Prague, Czech Republic)
for performing the HPLC analysis.
(j) C.D. Hall, N. Sachsinger, S.C. Nyburg, J.W. Steed, J.
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