Asymmetric addition of diethylzinc to aromatic aldehydes by chiral ferrocene-based catalysts

Article abstract of DOI:10.1016/S0022-328X(02)01139-7

A series of chiral C₁- and C₂-symmetric ferrocenyl Schiff bases (1a-c), ferrocenyl aminoalcohols (2a), ferrocenylphosphinamides (2b-c), 1,1′-ferrocenyl-diol (3), and 1,1′-ferrocenyl-disulfonamide (4) were prepared and employed as bas

Full text of DOI:10.1016/S0022-328X(02)01139-7

Journal of Organometallic Chemistry 649 (2002) 258–267
www.elsevier.com/locate/jorganchem
Asymmetric addition of diethylzinc to aromatic aldehydes by
chiral ferrocene-based catalysts
a,
a
a
a
Tae-Jeong Kim *, Hee-Yeol Lee , Eun-Sook Ryu , Dong-Kyu Park ,
a
a
b,
Chan Sik Cho , Sang Chul Shim , Jong Hwa Jeong *
a
Department of Industrial Chemistry, Kyungpook National Uni6ersity, Taegu 702-701, South Korea
b
Department of Chemistry, Kungpook National Uni6ersity, Taegu 702-701, South Korea
Received 4 June 2001; received in revised form 29 October 2001; accepted 29 November 2001
Abstract
A series of chiral C - and C -symmetric ferrocenyl Schiff bases (1a–c), ferrocenyl aminoalcohols (2a), ferrocenylphosphinamides
1
2
(
2b–c), 1,1%-ferrocenyl-diol (3), and 1,1%-ferrocenyl-disulfonamide (4) were prepared and employed as base catalysts or as ligand
for titanium(IV) complexes in the asymmetric addition of diethylzinc to aromatic aldehydes. High enantioselectivity up to almost
00% ee was achieved for the alkylation of benzaldehyde and p-methoxybenzaldehyde with 1 or 3. In contrast, however, the
1
b-aminoalcohol (2a) and phosphinamides (2b and c) that are ubiquitous classes of base catalysts for this reaction proved inefficient
in our hands, regardless of the types of substrates or reaction conditions. Comparative studies show that there exist various
reaction parameters governing not only chemical yields but also optical yields. These include steric and electronic environment of
the substrate, the solvent, the reaction temperature, and the nature of the ferrocene moieties. © 2002 Published by Elsevier Science
B.V.
Keywords: Chiral ferrocenes; Diethylzinc; Asymmetric addition; Aldehydes
derivatives [13], and ferrocene-based amino alcohols
1. Introduction
[14].
Following the lead by others, and motivated by our
The catalytic asymmetric addition of diorganozinc to
continuing effort to design a new series of chiral fer-
rocenes for use in asymmetric catalysis [15], we have
attempted the preparation of some new chiral fer-
rocenes such as those shown in Schemes 1 and 2 and
investigated their efficiency as base catalysts or as lig-
and for titanium complexes. In this paper their synthe-
sis, characterization including X-ray crystallographic
analysis, and application to asymmetric catalytic addi-
tion of diethylzinc to aldehydes are presented.
various aldehydes is an important method for the
preparation of optically active secondary alcohols, and
has thus attracted a great deal of interest since the first
report in 1984 by Oguni who used (S)-leucinol, a
b-amino alcohol, as base catalyst [1,2]. Upon examina-
tion of literature, it is now well established that enan-
tioselectivity can be accomplished either by Lewis base
catalysis or Lewis acid catalysis. Consequently there
now exist an array of chiral functionalities that have
been successfully used either as base catalysts or as
ligands for transition metal complexes. These include
the well-known b-amino alcohols [3], b-imino alcohol
2
. Results and discussion
[
[
4], piperazine [5], oxazaborolidine [6], aminothiolate
7], aminothiols [8], aminothioester [9], diols [10], disul-
2.1. Synthesis
fonamides [11], diphosphoramides [12], amino acid
The synthetic strategies and reaction conditions
adopted in this work are described in Schemes 1 and 2.
Scheme 1 shows the synthetic routes leading to the
formation of ferrocenyl Schiff bases (1a–c) and ferro-
*
Corresponding authors. Tel.: +82-53-950-5587; fax: +82-53-
9
50-6594.
E-mail address: tjkim@knu.ac.kr (T.-J. Kim).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(02)01139-7

T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
259
Table 1
cenylaminoalcohols (2a–c) to be used as base catalysts.
Their synthesis requires initially the preparation and the
resolution of chiral template, N,N-dimethyl-1-ferro-
cenylethylamine (FA) reported by Ugi and coworkers
Crystal data and structure refinement parameters for (R,S)-1c and
S,R)-2c
(
(
R,S)-1c
(S,R)-2c
[
16]. Ortholithiation of (R)-FA followed by elec-
Empirical formula
Molecular weight
Crystal system
C31H28FeNOP
517.36
Monoclinic
C19H32FeNO PSi
4
453.37
trophilic substitution with Me SiCl and Ph PCl pro-
duces corresponding ortho substituted derivatives with
3
2
Orthorhombic
P2 2 2
Space group
P2 /n
1
1 1 1
Unit cell dimensions
a (A
,
)
)
)
13.212(1)
13.354(1)
15.5670(9)
105.642(6)
2644.9(4)
4
7.8713(9)
11.1017(7)
25.566(2)
b (A
,
c (A
i (°)
,
3
V (A
,
)
2234.1(3)
4
1.348
8.23
Z
Dcalc (g cm−3)
1.299
6.54
−
1
v (cm
Crystal size (mm)
qmax (°)
)
0.30×0.35×0.40 0.45×0.45×0.50
2
50.96
4905
1752
317
0.048
0.078
50.94
2394
1999
245
0.34
0.101
0.52
Unique reflections
Observed (l\2|I)
Parameters
R1
wR2
Scheme 1.
Largest difference peak and 0.28
hole (e A
−
3
,
)
(
R,S)-configuration. These compounds are further con-
verted to the primary amines (C H )Fe(C H E)-
5
5
5
4
CH(Me)NH2 (E=SiMe , PPh ) via acetylation with
3
2
aceticanhydride followed by amination with liquid am-
monia [17].
Simple condensation reaction of salicylaldehyde with
(
R)-(C H )Fe[C H CH(Me)NH ] leads to the forma-
5 5 5 4 2
tion of (R)-1a, and the same reaction with (R,S)-
(
C H )Fe[C H -1-CH(Me)NH -2-SiMe ] and (R,S)-
5 5 5 3 2 3
(
C H )Fe[C H -1-CH(Me)NH -2-PPh ] to (R,S)-1b,
Scheme 2.
5
5
5
3
2
2
and (R,S)-1c, respectively. Their structural confirma-
tion comes from various techniques such as elemental
analysis, NMR spectroscopy, and mass spectrometry.
1
For instance, the H-NMR spectra confirm the pres-
ence of the hydroxy group appearing as a singlet in the
region 7.81–8.34 ppm, and the imino aldehydic proton
as a broad signal at 13.06–13.80 ppm. The presence of
strong infrared CꢀN stretching bands at around 1625
−
1
cm further confirms their structures. As for (R,S)-1c,
31
the P-NMR spectrum exhibits the expected singlet at
−
23.10 ppm. In addition, its X-ray crystal structure is
shown in Fig. 1, and crystal data in Table 1.
The preparation of 2a–c simply takes advantage of
the fact that the NH group in the starting compound
2
with a suitable leaving group such as trimethylammo-
nium undergoes nucleophilic substitution in a stereoten-
tive SN1-type reaction leading to complete retention of
configuration [16a,18]. Thus, treatment of the primary
Fig. 1. The X-ray crystal structure of (R,S)-1c. Selected distances (A)
,
and angles (°): C(6)ꢁC(7) 1.453(5), C(7)ꢁN 1.268(4), NꢁC(8) 1.466(4),
PꢁC(14) 1.821(4), PꢁC(20) 1.832(4), PꢁC(26) 1.845(4), C(6)ꢁC(7)ꢁN
amine (S)-(C H )Fe[C H CH(Me)NH ] with an
122.5(4),
C(7)ꢁNꢁC(8)
119.9(3),
C(14)ꢁPꢁC(20)
101.2(2),
5
5
5
4
2
C(14)ꢁPꢁC(26) 102.7(2), C(20)ꢁPꢁC(26) 100.2(2).
equimolar amount of MeI followed by the reaction

260
T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
which is produced from the acetylation of (R,R)-3
followed by amination.
2.2. Catalysis
2.2.1. Base catalysis
Since benzaldehyde is one of the most extensively
studied substrates in the enantioselective addition of
diethylzinc to aldehydes, we employed this substrate to
find the optimum reaction parameters such as the rela-
tive amount of catalyst, the solvent, and the reaction
temperature.
Table 2 shows the results of our initial investigation.
With (R)-1a as a base catalyst, both the highest chemi-
cal and optical yields are obtained with the combina-
Fig. 2. The X-ray crystal structure of (S,R)-2c. Selected distances (A)
,
and angles (°): NꢁC(11) 1.497(6), NꢁC(13) 1.471(6), NꢁP 1.615(4),
PꢁO(4) 1.467(4), PꢁO(2) 1.571(4), PꢁO(3) 1.568(4), C(11)ꢁNꢁC(13)
1
1
17.6(5), C(13)ꢁNꢁP 119.8(3), C(11)ꢁNꢁP 122.2(3), O(4)ꢁPꢁN
13.7(2), O(3)ꢁPꢁN 105.1(2), O(2)ꢁPꢁN 108.3(2).
tion of the substrate, Et Zn, and the catalyst in an
2
1
:3:0.1 molar ratio in toluene at 0 °C (entry 3). Other
with 2-aminoethanol resulted in the corresponding
aminoalcohol. The ortholithiation with BuLi followed
by treatment with trimethylsilyl chloride yields (S,R)-
solvents such as CH Cl , THF, and Et O give poor to
2
2
2
zero enantiomeric excesses (entries 4–6). Changing the
reaction temperature below or above 0 °C affects ad-
versely both the conversion and the enantiomeric excess
2a. Further substitution at the resulting secondary
amine group with HP(O)(OMe) leads to the formation
2
(
entries 7 and 8). Here it is worth noting the reversal of
of the ferrocenylphosphinamides (S,R)-2c.
The NMR patterns are straightforward and reveal
the absolute configuration of the product on cooling
the temperature below 0 °C.
the signals expected for their structures. For example,
As might be expected, structural and stereochemical
modification of the catalyst affects significantly both
the conversion and the enantiomeric excess as revealed
in Table 3. For instance, the conversion is retarded on
substitution with a bulkier group at the ortho position
of the ferrocene moiety. Thus, of the three catalysts
3
1
P-NMR spectra of (S)-2b and (S,R)-2c confirm the
presence of phosphinamide, and a more definitive evi-
dence comes from the X-ray crystal structure of (S,R)-
2c shown in Fig. 2. Its crystal data are listed in Table 1.
Scheme 2 describes the synthetic routes to the synthe-
sis of (R,R)-3 and (R,R)-4. Both routes employ essen-
tially the Friedel–Crafts acylation of ferrocene followed
by the well-established CBS reduction with (S)-2-
methyl-CBS-oxazaborolidine. By this method the previ-
ously known (R,R)-3 is obtained in an almost
quantitative yield (ꢀ93%) with enantioselectivity of
1
a–c, the highest conversion is achieved with 1a which
is sterically the least crowded (entry 1 vs. entries 3 and
5). As far as the enantiomeric excess is concerned,
however, 1c is the choice of preference, which gives 94%
ee under the standard set of reaction conditions (entry
5). Here, a cooperative interaction of diphenylphos-
phine with zinc in the zincate intermediate may be
accounted for the elevated ee% although the exact role
of phosphine is hard to know. Stereochemically, a
98% ee [19]. The formation of (R,R)-4 can be accom-
plished in high yield (86%) from the reaction of p-tolue-
nesulfonyl chloride with (R,R)-ferrocenyl-1,1%-diamine
Table 2
a
Optimization of asymmetric addition of diethylzinc to benzaldehyde catalyzed by (R)-1a
Entry
[sub]/[Zn]/[cat]
Solvent
Temperature (°C)
Yield (%)
% ee
Configuration
1
2
3
4
5
6
7
8
1.0/2.0/0.05
1.0/3.0/0.05
1.0/3.0/0.1
1.0/3.0/0.1
1.0/3.0/0.1
1.0/3.0/0.1
1.0/3.0/0.1
1.0/3.0/0.1
Toluene
toluene
toluene
CH Cl
THF
Ether
0
0
0
0
0
0
RT
−10
79
99
100
32
0
67
18
28
70
18
0
30
10
18
S
S
S
S
–
S
S
R
2
2
Toluene
Toluene
100
51
a
The stoichiometric amounts of Et Zn and PhCHO are 1.4 and 0.47 mmol, respectively.
2

T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
261
Table 3
The effects of catalyst on enantioselectivity of the addition of Et Zn to PhCHO
a
2
Entry
Catalyst
(R)-1a
Condition b
Yield (%)
% ee
Configuration
1
2
3
4
5
6
7
8
A
B
A
B
B
A
A
A
100
71
63
47
40
55
53
50
70
74
44
52
98
36
5
S
S
S
S
S
R
R
R
(R,S)-1b
(R,S)-1c
(S,R)-2a
(S)-2b
(S,R)-2c
25
a
The reaction was run under the same conditions as described in entry 3, Table 2.
Experimental details for conditions A and B are described in Section 4.
b
matching combination of central and planar chirality in
Very high enantiomeric excesses are accomplished for
the alkylation of benzaldehyde and p-methoxybenzalde-
hyde (entries 1 and 2). These values are comparable
with those obtained with the well-known catalysts in
the literature [1,3–14]. With this catalyst even higher
enantiomeric excess is obtained at temperature below
0 °C (entries 1 and 2). In addition, no change in the
product configuration is observed regardless of the
types of substrate. For the comparative purposes, it can
be stated as a rule of thumb that any substitution at the
aromatic ring lowers the ee% value as compared with
the parent benzaldehyde. Further, both electronic and
steric factors of the substrate affect apparently the
enantiomeric excess. For instance, o- and p-
methoxyaldehydes provide representative examples (en-
tries 3 and 4). While the former leads to higher ee%
than the latter (84% ee vs. 22% ee), the trend in the
chemical yields is reversed (30% vs. 95%). A possible
explanation for the lower ee% with o-methoxybenzalde-
hyde may be given in terms of the fact that the strong
the catalyst for a given product configuration seems to
be (S,R) or (R,S) as judged from the observations that
both (R,S)-1b and (R,S)-1c give the same product
configuration (S) as (R)-1a (entries 1, 3, and 5), while
the catalysts with the (S,R) combination give the
product with an opposite configuration (entries 6–8). It
is rather disappointing to find that the b-aminoalcohol
(
2a) and the phosphinamide catalyts 2b and c give even
lower enantiomeric excesses than their iminoalcohol
counterpart 1a–c. This may prove that the presence of
a b-aminoalcohol moiety in the catalyst as a structural
prerequisite for high enantioslectivity is ungrounded.
An additional feature of Table 3 is that the catalyst,
when it is made pre-formed (condition B), works better
to give higher enantiomeric excess than when it is used
in situ (condition A) (entries 1 and 3 vs. entries 2 and
4). These same observations had already been made by
others [14b] and may be explained partly in terms of the
increased Lewis acidity of the pre-formed zinc catalyst,
which makes the attack of incoming aldehyde to di-
ethylzinc more effective. In fact, chiral Lewis bases are
known to activate diorganozincs by coordinating to the
zinc atom and by forming chiral zincate of the type
Table 4
Base-catalyzed asymmetric addition of diethylzinc to various alde-
a
hydes catalyzed by (R,S)-1c
R Zn-B which, due to the enhanced nucleophilicity of
2
organo moiety of chiral zincate, adds to aldehydes in an
enantioselective fashion (vide infra).
Entry
R
Yield (%)
% ee Configuration
1
2
3
4
5
6
7
Ph
40
30
95
100
97
85
98
84
22
14
72
24
36
S
S
S
S
S
S
S
p-MeOC H
o-MeOC H
p-ClC H
trans-PhCHꢀCH
1-Naphthyl
6
4
4
6
6
4
Having established the optimum reaction conditions
and found that (R,S)-1c exhibits the highest enantiose-
lectivity, we proceeded to the reactions of a series of
aromatic aldehydes employing (R,S)-1c as catalyst. The
results are listed in Table 4.
2-Naphthyl
100
a
Reactions were carried out under the condition B described in
Section 4.

262
T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
Table 5
Optimization of Ti-catalyzed asymmetric alkylation of PhCHO
Entry
[sub]/[Zn]/[L]
L a
Solvent
Temperature (°C)
Yield (%)
% ee
Configuration
1
2
3
4
5
6
7
8
9
1.0/2.0/0.1
1.0/2.0/0.15
1.0/2.0/0.2
1.0/3.0/0.2
3
3
3
3
Toluene
Toluene
Toluene
Toluene
Toluene
THF
RT
RT
RT
RT
0
39
62
97
89
70
76
49
95
23
39
45
100
92
83
42
100
28
30
34
96
96
22
70
6
72
80
52
84
90
96
4
R
R
R
R
R
S
S
R
S
S
S
S
S
S
S
S
RT
0
THF
CH Cl
RT
RT
RT
RT
RT
0
−10
RT
RT
2
2
1.0/2.0/0.2
1.0/2.0/0.15
1.0/2.0/0.2
1.0/3.0/0.15
4
4
4
4
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
CH Cl
10
11
12
13
14
15
16
2
2
1.0/3.0/0.2
4
Toluene
58
a
The absolute configuration of both 3 and 4 is (R,R).
steric hindrance of ortho-substituents weakens the co-
ordination of the substrate to the catalyst thus lower-
ing influence of the chiral environment of the catalyst
on the orientation of the substrate [10c]. Similar obser-
vations are also made in the reaction of naphthalde-
hydes: namely, higher enantioselectivity and lower
conversion with hindered aldehydes (entries 7 and 8).
When only the electronic effects are taken into consid-
eration, electron-donating substituents (i.e. methoxy,
allyl) result in both higher conversion and enantioselec-
tivity than electron-withdrawing groups (entries 3, 5,
and 6).
Based on this rationale, it is tempting to investigate
the efficiency of (R,R)-3 and (R,R)-4 as chiral ligands
for titanium(IV) complexes.
Again, through optimization of various reaction
parameters, both ligands proved to be highly efficient
for the target reaction as shown in Table 5 (entries 4
and 14). The two ligands possessing the same absolute
configurations lead to opposite product configurations.
Here, as in the case of base catalysis, the choice of
solvent is toluene to guarantee high enantiomeric ex-
cess. In other solvents both chemical and optical yields
drop significantly, and in the case of THF reversal in
the product configuration is accompanied (entries 6
and 7). As expected, lowering the reaction temperature
causes increase in ee% with a concomitant drop in the
chemical yield, yet enantioselectivity seems to be more
tolerable toward a change in the reaction temperatures
(entries 4, 5, and 12–14).
Table 6 shows the results of Ti-catalyzed asymmetric
alkylation of various aromatic aldehydes employing
(R,R)-3 and (R,R)-4 as ligands. Very high enantioselec-
tivity is achieved for the reaction of benzaldehyde and
p-methoxybenzaldehyde reaching as high as 100% ee
(entries 1–4). These values are ranked among the
highest in the literature [10–12].
2.2.2. Acid catalysis
In Lewis acid catalysis, aldehydes are activated ini-
tially by coordinating to the metal such as titanium.
The electrophilicity of aldehyde is thus enhanced
enough to be attacked by diorganozinc from one enan-
tioface of the aldehydes. The Lewis acidity may be
further increased by the presence of the electron-with-
drawing ligands such as sulfonamide, as may be de-
duced from the structure of a reaction intermediate
suggested to be present in the catalytic cycle (vide
infra) [11e].
Of the two ligands, the disulfonamide (R,R)-4 gives
higher % ee values throughout all substrates investi-
gated. Here again, any substitution at the aromatic
ring of benzaldehyde drops the % ee values signifi-
cantly regardless of the steric or electronic nature of
the substituent. When the comparison is made among
the

T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
263
substrates, those bearing the electron-donating group
exhibit slightly higher enantioselectivity than their elec-
tron-withdrawing counterparts (entries 3 and 4 vs. en-
tries 7 and 8). This is because the substrate carrying the
electron-donating group bounds through oxygen more
tightly to the Lewis acidic titanium center, thus chiral
environment of the catalyst becoming more influential.
Steric factors also play a role, which can be seen from
the reactions of p- and o-methoxybenzaldehydes (en-
tries 3 and 4 vs. 5 and 6). The same reasoning provided
in the case of base catalysis (vide supra) may be applied
in the acid catalysis as well. In the same vein, the
sterically less-hindered 2-naphthaldehyde gives slightly
higher enantioselectivity than the sterically more de-
manding 1-naphthaldehyde (entries 11 and 13 vs. en-
tries 12 and 14).
cal yields but also optical yields. These include steric
and electronic environment of the substrate, the sol-
vent, the reaction temperature, and the nature of the
ferrocene moieties.
4
. Experimental
4.1. General
All manipulations were carried out under an atmo-
sphere of Ar or N using Schlenk techniques. Solvents
2
were purified by standard methods and were freshly
distilled prior to use. All commercial reagents were used
as received unless otherwise mentioned. Microanalyses
were performed by the Center for Instrumental Analy-
sis, Kyungpook National University. Melting points
were measured using a electrothermal model IA 9100
digital melting point apparatus and are reported with-
3. Conclusions
1
31
out correction. H- and
P-NMR spectra were
We have prepared a series of C - and C -symmetric
ferrocene-based chiral compounds such as Schiff bases
1a–c), aminoalcohols (2a–c), ferrocenyl-1,1%-diol (3),
recorded in a Varian Unity Plus spectrometer operating
1
2
1
at 400 and 121.5 MHz, respectively. H shifts are
31
(
reported relative to internal Me Si and P shifts rela-
4
and ferrocenyl-1,1%-disulfoanamide (4) and used them
as base catalysts or as ligands for titanium complexes in
the enantioselective addition of diethylzinc to aromatic
aldehydes. Except for 2a–c, all these compounds prove
excellent for the alklylation of benzaldehyde and p-
methoxybenzaldehyde to give high ee% values that are
comparable to or in some instances even higher than
those obtained with the well-known catalysts in the
literature. Comparative studies show that there exist
various reaction parameters governing not only chemi-
tive to 85% H PO . High-resolution mass spectra
3
4
(HRMS) were obtained by using a Micromass Quattro
II GC8000 series model with electron energy of 20 or 70
eV. Optical rotations were measured on a JASCO
DIP-360 digital polarimeter at ambient temperature. IR
spectra were run in a Mattson FT-IR Galaxy 6030E
spectrophotometer and Nicolet Magna-IR 550 spec-
trophotometer. HPLC analyses were performed in a
Waters 600E type instrument equipped with a chiral
column (chiralcel OD, Daicel Chemical Industries) and
Table 6
a
Ti-catalyzed asymmetric alkylation of aromatic aldehydes
Entry
R
L
Yield(%)
% ee
Configuration
1
2
3
4
5
6
7
8
9
Ph
3
4
3
4
3
4
3
4
3
4
3
4
3
4
89
83
99
96
99
96
99
25
99
89
98
100
100
100
96
96
46
100
12
20
8
18
4
44
6
R
S
R
S
R
S
R
S
S
S
S
R
S
R
p-MeOC H
6
4
4
o-MeOC H
6
p-ClC H
6
4
trans-PhCHꢀCH
1-Naphthyl
10
11
12
13
14
22
6
24
2-Naphthyl
a
[
Sub]/[Zn]/[(R,R)-3]=1.0/3.0/0.2; [Sub]/[Zn]/[(R,R)-4]=1.0/3.0/0.15.

264
T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
UV detector for determining the optical purity of the
products. The absolute configuration of the products
was assigned by comparing the sign of optical rotation
values with literature data [3m].
4.5. (R)-2-{1-[(S)-2-(Trimethylsilyl)ferrocenylethyl-
imino]methyl}phenol ((R,S)-1b)
The title compound was prepared in the same manner
as described above for (R)-1a by simply replacing (R)-1-
ferrocenylethylamine with (R)-1-[(S)-2-(trimethylsi-
lyl)ferrocenyl]ethylamine (1.4 g, 4.7 mmol). The product
was obtained as orange crystals after recrystallization
from hexane. Yield: 1.8 g, 96%. M.p.: 110–112 °C.
4.2. Structure determinations
Crystal data and details of the structural analysis are
tabulated in Table 1. Intensity data were collected at
room temperature with CAD4 diffractometer using
monochromated Mo–Ka radiation (u=0.71073 A).
,
20
−1
[
1
1
h] = −115.9 (c=0.01, CHCl ). w
(KBr, cm ):
D
3
CꢀN
1
625 (m). H-NMR (CDCl ): 0.19 (s, 9H, Si(CH ) ),
.67 (d, J=6.9 Hz, 3H, CH ), 4.13, 4.39, 4.42 (3H,
3 3 3
3
Lorentz and polarization reflections were applied and
absorption corrections made with 3c scans. The struc-
tures solved by direct methods and refined by full-ma-
C H ), 4.16 (s, 5H, C H ), 4.75 (q, J=6.8 Hz, 1H, CH),
5
3
5
5
6
1
.77–7.27 (m, 4H, C H ), 7.97 (s, 1H, OH), 13.71 (br,
H, NꢀCH). MS; m/z (%): 405 (69, [M ]), 285 (100), 73
6 4
+
2
trix least-squares methods based on F using SHELXS-97
(
39). Anal. Calc. for C H FeNOSi: C, 65.18; H, 6.71;
22 27
and SHELXL-97 [20]. The R values are defined as R =
1
N, 3.46. Found: C, 65.59; H, 6.86; N, 3.37%.
2
o
2 2
ꢀ
(ꢁ ꢁF ꢁ ꢁ−ꢁ ꢁF ꢁꢁ)/ꢀꢁF ꢁ
and
wR =[ꢀ (F −F ) /
o
c
o
2
w
c
2
2 1/2
ꢀ
(F ) ]
.
Non-hydrogen atoms were refined
w
o
anisotropically and hydrogen atoms were included in
calculated positions.
4.6. (R)-2-{1-[(S)-2-(Diphenylphosphino)-
ferrocenylethylimino]methyl}phenol ((R,S)-1c)
4.3. Materials
The title compound was prepared in the same manner
as described above for (R)-1a by replacing (R)-1-ferro-
N,N-Dimethyl-1-ferrocenylethylamine (FA) [16], (R)-
-ferrocenylethylamine [16c], (R)-N,N,dimethyl-1-[(S)-
-(trimethylsilyl)ferrocenyl]ethylamine [17b], (R)-1-[(S)-
cenylethylamine
with
(R)-1-[(S)-2-(diphenylphos-
1
2
2
phino)ferrocenyl]ethylamine (1.0 g, 2.4 mmol).
Recrystallization from Et O gave orange crystals. Yield:
2
2
0
-(trimethylsilyl)ferrocenyl]ethylamine
[17b],
(R)-
1.1 g, 88%. M.p.: 154–155 °C. [h] = −9.3 (c=0.01,
D
−
1
1
N,N,dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]-
ethylamine [17b], (R)-1-[(S)-2-(diphenylphosphino)-
ferrocenyl]ethylamine [17b],. (S)-2-(1-ferrocenylethy-
lamino)ethanol [19] were prepared according to the
literature methods.
CHCl ). w
(KBr, cm ): 1625 (s). H-NMR (CDCl ):
3
CꢀN 3
1.62 (d, J=6.5 Hz, 3H, CH ), 3.67, 4.26, 4.51 (3H,
3
C H ), 4.01 (s, 5H, C H ), 4.64 (q, J=7.4 Hz, 1H, CH),
5
3
5
5
6.53–7.45 (m, 14H, C H and C H ), 7.81 (s, 1H, OH),
6
5
6
4
3
1
13.06 (br, 1H, NꢀCH). P-NMR (CDCl ): −23.10 (s).
MS; m/z (%): 517 (82, [M ]), 452 (89), 398 (100), 212
3
+
(
46). Anal. Calc. for C H FeNOP: C, 71.97; H, 5.45;
31 28
4
.4. (R)-2-[(1-Ferrocenylethylimino)methyl]phenol
N, 2.71. Found: C, 71.62; H, 5.50; N, 2.64%.
(
(R)-1a)
Salicylaldehyde (1.4 ml, 13 mmol) was added to
(
R)-1-ferrocenylethylamine (3.0 g, 13 mmol) dissolved
4.7. (S)-2-1-[(R)-2-Trimethylsilyl]-
in EtOH (30 ml). The solution was stirred for 2 h under
reflux. After cooling the reaction mixture to room
temperature (r.t.), the solvent was removed to leave a
dark residue which was chromatographed on silica gel
ferrocenylethylaminoethanol ((S,R)-2a)
The title compound was prepared in the same manner
as described above for (S)-2-(1-ferrocenylethy-
lamino)ethanol by simply replacing (S)-N,N,N-
with a mixture of hexane and Et O (9:1) as an eluent.
2
The single orange band was collected to give orange
trimethyl-1-ferrocenylethylammonium
iodide
with
crystals after recrystallization from Et O. Yield: 3.9 g,
(S)-N,N,N-trimethyl-1-[(R)-2-(trimethylsilyl)ferrocenyl-
ethyl]ammonium iodide (8.00 g, 17.0 mmol). The
product was obtained as a yellow solid. Yield: 5.00 g,
2
2
0
9
0%. M.p.: 134–135 °C. [h] = −25.3 (c=0.01,
D
−
1
1
CHCl ). w
(KBr, cm ): 1625 (s). H-NMR (CDCl ):
3
3
CꢀN
20
1
.57 (d, J=6.6 Hz, 3H, CH ), 4.09, 4.15 (AB, 4H,
85%. M.p.: 93–94 °C. [h] = −19 (c=0.1, CHCl ).
3
D 3
1
C H ), 4.16 (s, 5H, C H ), 4.30 (q, J=6.5 Hz, 1H, CH),
H-NMR (CDCl ): 0.29 (s, 9H, (CH ) Si), 1.48 (d, 3H,
3 3 3
5
4
5
5
6
1
1
6
4
.87–7.35 (m, 4H, C H ), 8.34 (s, 1H, OH), 13.80 (br,
H, N=CH). MS; m/z (%): 333 (81, [M ]), 213 (100),
J=6.5 Hz, CH ), 2.59–2.71 (m, 2H, CH OH), 3.53 (t,
6
4
3
2
+
J=5.1 Hz, 2H, CH N), 3.70 (q, 1H, CH), 4.05, 4.28 and
2
76 (41), 121 (49). Anal. Calc. for C H FeNO: C,
4.36 (3H, C H ), 4.10 (s, 5H, C H ). HRMS; m/z (%):
19
19
5
3
5
5
+
8.49; H, 5.75; N, 4.20. Found: C, 68.46; H, 5.74; N,
.17%.
Calc. for C H ONSiFe: 345.1211 [M ]. Found:
17 27
345.1212.

T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
265
4
2
.8. N-(O,O-Dimethylphosphoryl)-(S)-
-(1-ferrocenylethylamino)ethanol ((S)-2b)
tion of MeOH (20 ml; caution: gas evolution!). After
the methanolysis had ceased, the mixture was poured
into saturated aq. NH Cl (250 ml) and extracted with
4
To an ice-cold stirred solution of (S)-2-(1-ferro-
CH Cl . The organic layer was washed with water (100
2
2
cenylethylamino)ethanol (4.00 g, 14.6 mmol), dimethyl
ml). The solvents were evaporated to leave a yellow
phosphite (1.61 ml, 17.5 mmol), and Et N (2.44 ml,
solid which was purified by column chromatography on
3
1
7.5 mmol) in CH Cl (30 ml) was added dropwise
silica gel with a mixture of hexane and Et O (1:1) as an
2
2
2
20
CCl (2.96 ml, 30.7 mmol). The resulting solution was
allowed to slowly warm to r.t. and then stirred for 5 h,
after which time the mixture was quenched with aq.
NH Cl. The organic layer was separated, dried over
anhydrous MgSO , and the solvent removed under
eluent. Yield: 5.1 g, 93%. M.p.: 68–69 °C. [h] = −
4
D
1
51.1 (c=0.01, CHCl3). H-NMR (CDCl ): 1.40 (d,
3
J=6.4 Hz, 6H, CH ), 4.12–4.19 (m, 8H, C H ), 4.65
3
5
4
+
(qt, J=6.4 Hz, 2H, CH). MS; m/z (%): 274 (51, [M ]),
256 (46), 164 (100), 92 (76), 91 (62). Anal. Calc. for
C H O Fe: C, 61.34; H, 6.62. Found: C, 61.04; H,
4
4
reduced pressure. The residue was chromatographed on
14
18
2
silica gel (eluent: EtOAc–CH CN, 1:1) to afford orange
6.57%.
3
crystals after crystallization from Et O. Yield: 3.50 g,
2
2
0
6
0%. M.p. 105–106 °C. [h] = +143 (c=0.1, CHCl ).
4.11. (R,R)-1,1%-Bis(1-ferrocenylethylamine)
D
3
1
H-NMR (CDCl ): 1.51 (d, J=6.7 Hz, 3H, CH ),
3
3
2
3
.90–3.02 (m, 3H, CH N) 3.07 (t, J=5.6 Hz, 1H, OH),
The diol (R,R)-2 was converted to the title com-
pound as follows: (R,R)-1,1%-bis(1-ferrocenylethyl ace-
tate) (2.0 g, 5.6 mmol) prepared according to the
literature method [20] was dissolved in MeOH (20 ml)
saturated with NH3 (40 ml) in an autoclave at −
30 °C. The reaction mixture was stirred for 10 h at
2
.27–3.38 (m, 2H, CH OH), 3.73 (d, J=4.4 Hz, 3H,
2
OCH ), 3.76 (d, J=4.4 Hz, 3H, OCH ), 4.59 (q, 1H,
3
3
CH), 4.16 and 4.30 (AB, 4H, C H ), 4.13 (s, 5H, C H ).
5
4
5
5
3
1
P-NMR (CDCl ): 15.3 (s). HRMS; m/z (%): Calc. for
3
+
C H O NFe: 381.0792 [M ]. Found: 381.0793.
1
6
24
4
1
00 °C, after which the mixture was cooled to r.t. The
4.9. N-(O,O-Dimethylphosphoryl)-(S)-2-1-
unreacted NH was released and the remaining solution
3
[(R)-2-tri-methylsilyl]ferrocenylethylaminoethanol
treated with dilute aq. NaOH. The organic layer was
(
(S,R)-2c)
extracted with Et O, the solvents dried over anhydrous
2
MgSO , and evaporated to dryness to give a brown oil.
4
2
0
The title compound was prepared in the same man-
Yield: 1.3 g, 86%. [h] = −33.3 (c=0.01, CHCl ).
H-NMR (CDCl ): 1.33 (d, J=6.5 Hz, 6H, CH ), 1.80
3 3
D
3
1
ner as described above for (S)-2b by replacing (S)-2-(1-
ferrocenylethylamino)ethanol with (S,R)-2a (3.00 g,
(s, 4H, NH ), 3.81 (qt, J=7.0 Hz, 2H, CH), 4.10–4.13
2
+
8
.69 mmol). The product was obtained as orange crys-
(m, 8H, C H ). MS; m/z (%): 272 (29, [M ]), 255 (100),
5
4
2
0
tals. Yield: 2.22 g, 58%. M.p.: 153–154 °C. [h] = +
240 (39), 228 (33). HRMS; m/z (%): Calc. for
D
1
+
5
6 (c=0.1, CHCl ). H-NMR (CDCl ): 0.31 (s, 9H,
C H N Fe: 272.1754 [M ]. Found: 272.0976.
3
3
14 20
2
SiMe ), 1.50 (d, J=5.7 Hz, 3H, CH ), 2.14 (t, J=5.8
3
3
Hz, 1H, OH), 2.92–2.98 (m, 2H, CH N), 3.06–3.14 (m,
4.12. (R,R)-1,1%-Bis[N-(1-ferrocenylethyl)-4-
methylbenzenesulfonamide] ((R,R)-3)
2
2
H, CH OH), 3.72 (d, J=3.6 Hz, OCH ), 3.74 (d,
2
3
J=3.6 Hz, OCH ), 4.74 (qt, 1H, CH), 4.45–4.15
3
31
(
ABC, 3H, C H ), 4.16 (s, 5H, C H ). P-NMR
p-Toluenesulfonyl chloride (2.8 g, 15 mmol) in
CH Cl (20 ml) was added to a solution of (R,R)-1,1%-
5
3
5
5
(CDCl3): 19.3 (s). HRMS; m/z (%): Calc. for
2
2
+
C H O NSiPFe: 453.1188 [M ]. Found: 453.1188.
bis(1-ferrocenylethylamine) (2.0 g, 7.4 mmol) and Et N
1
9
32
4
3
(
2.6 g, 26 mmol) in CH Cl (30 ml) at −30 °C. After
2 2
4.10. (R,R)-1,1%-Bis(1-ferrocenylethanol) ((R,R)-3)
stirring for 10 h at r.t., the reaction mixture was
extracted with CH Cl . The solvent was dried over
2
2
The title compound was obtained according to the
anhydrous MgSO and concentrated to about 2 ml to
4
literature method with a slight modification [19]. The
S)-2-methyl-CBS-oxazaborolidine catalyst (3.3 g, 12
mmol) was dissolved in THF (30 ml) and cooled to
°C. From a syringe charged with borane dimethyl-
be chromatographed on silica gel (eluent: hexane and
(
Et O, 1:2). A yellow solid was obtained after usual
2
2
0
work-up. Yield: 2.5 g, 59%. M.p.: 162–164 °C. [h] =
−27.7 (c=0.01, CHCl ). H-NMR (CDCl ): 1.29 (d,
D
1
0
3
3
sulfide (BMS) (1 M in THF, 40 ml) 20% of the final
amount (8 ml) was added to the catalyst solution. After
stirring 5 min, the remaining BMS and a solution of the
diacetylferrocene (5.4 g, 20 mmol) in THF (50 ml) was
added simultaneously within 20 min. The red color of
ketone turned to yellow on reduction. After 15 min at
J=6.8 Hz, 6H, CHCH ), 2.44 (s, 6H, PhCH ), 3.91–
3
3
4.10 (m, 8H, C H ), 4.15–4.22 (m, 2H, CH), 4.93 (d,
5
4
J=7.6 Hz, 2H, NH), 7.33 (d, J=8.4 Hz, 4H, C H ),
6
2
7.83 (d, J=8.4 Hz, 4H, C H ). MS; m/z (%): 580 (23,
6
2
+
[M ]), 396 (30), 91 (100), 65 (31). Anal. Calc. for
C H N O S Fe: C, 57.93; H, 5.56; N, 4.83; S, 10.05.
2
8
32
2
4 2
0
°C, the excess BMS was quenched by dropwise addi-
Found: C, 58.18; H, 5.59; N, 4.60; S, 10.29%.

266
T.-J. Kim et al. / Journal of Organometallic Chemistry 649 (2002) 258–267
4
4
.13. General procedure for base catalysis
1-(p-Chlorophenyl)-1-propanol (d). (R)-d: t =11.3
R
min; (S)-d: t =10.4 min.
R
(
E)-1-Phenyl-1-(3-pentenol) (e). (R)-e: t =11.9 min;
R
.13.1. Condition A
A toluene solution (1.0 ml) of the base catalyst 1
(
S)-e: t =19.4 min.
R
1
-(1-Naphthyl)-1-propanol (f). (R)-f: t =19.2 min;
R
(
0.047 mmol, 10 mol%) was prepared. After stirring the
(
S)-f: t =12.5 min.
R
solution for 10 min at ambient temperature, 30 molar
excess of diethylzinc (1.4 ml, 1.4 mmol) was added to
the solution. Stirring was continued for additional 30
min. The resulting solution was cooled to 0 °C to
which benzaldehyde (0.048 ml, 0.47 mmol) was added.
The reaction mixture was stirred further for 48 h at
1
-(2-Naphthyl)-1-propanol (g). (R)-g: t =23.8 min;
R
(
S)-g: t =21.9 min.
R
5
. Supplementary material
0
°C, quenched with 5% HCl, and extracted with Et O.
2
Crystallographic data for the structural analysis have
The organic layer was dried over anhydrous MgSO4
and evaporated to dryness. The oily residue was passed
through a short silica gel column to remove catalyst
using a 95:5 hexane–EtOAc mixture as an eluent.
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 172446 and 172447 for com-
pounds (R,S)-1c and (S,R)-2c. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
4.13.2. Condition B
A 1:1 mixture of diethylzinc (0.047 ml, 0.047 mmol, 1
M solution in hexane) and the base catalyst 1 (0.047
mmol, 10 mol%) in toluene (1 ml) was prepared. The
solution was stirred for 30 min at ambient temperature,
after which was cooled to 0 °C and treated with di-
ethylzinc (1.4 ml, 1.4 mmol) and benzaldehyde (0.048
ml, 0.47 mmol). The reaction mixture was further
stirred for 48 h at this temperature. Quenching with 5%
Acknowledgements
We gratefully acknowledge The Korean Research
Foundation (KRF-2000-DP-0217) for the financial
support.
HCl followed by extraction with Et O, drying over
2
anhydrous MgSO , and column chromatogrpahic sepa-
ration gave the product.
4
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(
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