Synthesis of novel ferrocenyl-based p,s ligands (thioclickferrophos) and their use in pd-catalyzed asymmetric allylic substitutions

Article abstract of DOI:10.1002/ejoc.200900766

A series of P,S ligands (ThioClickFerrophos) based on a triazoleferrocenylethyl backbone were synthesized in a fourstep sequence by click chemistry methodology. The new P,S ligands were applied in allylic alkylations, etherifications, and aminations of 1,

Full text of DOI:10.1002/ejoc.200900766

FULL PAPER
DOI: 10.1002/ejoc.200900766
Synthesis of Novel Ferrocenyl-Based P,S Ligands (ThioClickFerrophos) and
Their Use in Pd-Catalyzed Asymmetric Allylic Substitutions
Minoru Kato,[a] Tatsuhito Nakamura,[a] Kenichi Ogata,[a] and Shin-ichi Fukuzawa*[a]
Keywords: Metallocenes / Asymmetric catalysis / Allylic compounds / Palladium / P,S ligands / Allylic substitution
A series of P,S ligands (ThioClickFerrophos) based on a tri-
azoleferrocenylethyl backbone were synthesized in a four-
step sequence by click chemistry methodology. The new P,S
ligands were applied in allylic alkylations, etherifications,
and aminations of 1,3-diphenylprop-2-enyl acetate catalyzed
by Pd complexes. These reactions proceeded smoothly to
give products in good yields and with good enantioselectivi-
ties of up to 90% ee.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
enantioselective metal-catalyzed asymmetric reactions in-
cluding Pd-catalyzed allylic substitution reactions.[6] Chan
and co-workers have synthesized the Bophoz-type P,S li-
gand FerroNPS and have shown that its Pd complexes can
serve as excellent catalysts not only for the more commonly
encountered asymmetric alkylation and amination but also
for difficult allylic etherifications.[7a–7b] Furthermore, they
have also synthesized another type of P,S ligand that was
successfully applied for the allylic alkylation of indoles.[7c]
The planar chirality of the ferrocene core has also been
combined with other P,S ligands.[8]
We have recently reported on a ferrocenyl-1,2,3-triazole-
based 1,5-diphosphane ligand (ClickFerrophos, Figure 1).
This scaffold can be readily prepared by click chemistry
methodology,[9] and possesses beneficial features such as
ease of accessibility and potential for fine-tuning of the ste-
ric and electronic properties of the phosphane group. This
ligand has demonstrated its effectiveness in metal-catalyzed
asymmetric hydrogenations of alkenes and ketones, copper-
catalyzed 1,3-dipolar cycloadditions of azomethine ylide
with electron-deficient alkenes, and reductive aldol reac-
tions of ethyl acrylate with ketones. ClickFerrophos can af-
ford hetero-diphosphanes through the introduction of two
distinct phosphane groups: firstly on its cyclopentadienyl
ring and secondly on its triazole ring. Accordingly, as
shown in Figure 1, a P,S ligand should be preparable either
Introduction
Pd-catalyzed allylic substitution is a powerful tool for
enantioselective carbon–carbon and carbon–heteroatom
bond formation and has accordingly been intensively
studied.[1] For highly enantioselective reactions, C2-symmet-
ric ligands or mixed hetero-donating ligands have typically
been utilized. For mixed-donor ligands, P,N ligands have
been extensively studied, and have been shown to be effec-
tive ligands for Pd-catalyzed asymmetric allylic substitution
reactions.[2] Unlike in the case of P,N ligands, numerous
studies have indicated potential problems with regard to the
use of chiral P,S mixed donors for metal-catalyzed asym-
metric reactions.[3] A sulfur atom is considered a soft atom
that can form strong bonds with soft metals such as Pd and
Cu.
Ferrocene-based chiral phosphanes have been employed
in various important metal-catalyzed asymmetric reac-
tions.[4] The introduction of heteroatom-based functional
groups onto ferrocene systems has significantly improved
the features of the ferrocene scaffold, thus extending its ap-
plicability as an industrial catalytic ligand. Although the
well known ferrocenyl diphosphanes are widely used in
homogeneous catalysis, due to their utility in providing
highly efficient catalysts with soft metals, information relat-
ing to P,S-ferrocene systems has been sparse. Enders and
co-workers have reported on the synthesis and use of ferro-
cenyl P,S ligands derived from ferrocenyl SAMP/RAMP hy-
drazones in Pd-catalyzed allylic substitutions.[5] Recently,
Carretero and co-workers have successfully applied their
original ferrocenyl-based P,S ligands (Fesulphos) for highly
[a] Department of Applied Chemistry, Institute of Science and
Engineering, Chuo University,
1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
Fax: +81-3-3817-1895
E-mail: orgsynth@kc.chuo-u.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900766.
Figure 1. ClickFerrophos and ThioClickFerrophos.
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Ferrocenyl-Based P,S Ligands in Asymmetric Catalysis
by sulfination of the cyclopentadienyl moiety followed by
phosphination of the triazole ring (Type I) or vice versa
(Type II). Here we describe the preparation of novel P,S-
ferrocenyl ligands (ThioClickFerrophos) and their applica-
tions in Pd-catalyzed asymmetric allylic substitution reac-
tions.[10]
Results and Discussion
Preparation of ThioClickFerrophos Ligands
As shown in Scheme 1, (S,Rp)-ortho-bromo-(1-azidoe-
thyl)ferrocene (1) was subjected to a click reaction with
phenylacetylene to afford the triazole backbone 2a in a
good yield (87%). Alternatively, a click reaction with (tri-
methylsilyl)acetylene, followed by removal of the silyl
group, afforded the 4-unsubstituted triazole 2b in a 42%
overall yield.[9c] Subsequently, the 2-ortho-thioferrocenes
3a–3f were obtained by lithium–halogen exchange at the
ortho-position of the cyclopentadienyl ring followed by
treatment with diaryl or dialkyl disulfides (61–81% yields).
Subsequent lithiation at the 5-triazole ring, followed by
trapping with diphenylphosphanyl chloride, afforded Thio-
ClickFerrophos Type I ligands (TCF1–6) in moderate to
good yields. The structure of TCF1 was confirmed by X-
ray crystallography (Figure 2). Type II ligands were simi-
larly obtained by reversal of the order of the reaction –
specifically, phosphination of the cyclopentadienyl ring, fol-
lowed by sulfination of the triazole ring.
Figure 2. X-ray structure of TCF1.
Asymmetric Allylic Alkylation
The Type I and Type II ligands were first evaluated in
the Pd-catalyzed allylic alkylation of (Ϯ)-1,3-diphenylprop-
2-enyl acetate (4) with dimethyl malonate (Scheme 2). For
the representative Type I (TCF1) and Type II ligands, R1,
R2, and R3 were all phenyl groups. The reactions were car-
ried out at room temp. in CH2Cl2 for 15 h in the presence
of the ligand (6 mol-%) and [Pd(η3-C3H5)Cl]2 (2 mol-%),
along with N,O-bis(trimethylsilyl)acetamide (BSA) and a
catalytic amount of KOAc (3 mol-%) as bases. Although
the Type I ligand (with TCF1) was effective in forming the
S-configured product 5 in 97% yield with 70% ee, the
Type II ligand was less effective, resulting in the R-config-
ured product with a lower yield (85%) and enantio-
selectivity (61% ee; Scheme 2). Because the Type I ligand
was more effective than the Type II variant, the Type I li-
gand derivatives (TCF2–6) were screened in the same reac-
tion.[8e]
Scheme 2. Asymmetric allylic alkylations in the presence of Pd/
ThioClickFerrophos.
The yields and enantioselectivities of the Pd-catalyzed al-
lylic alkylations are listed in Table 1. In the cases of ligands
with arylthio groups (TCF1–3, Entries 1–3, respectively),
the products were obtained in high yields (97–99%) with
moderate enantioselectivities (S, 70% ee). No substituent
effects (methyl and chloro groups at the para-position) were
observed in the three reactions. In the cases of ligands with
alkylthio groups (TCF4, cyclohexyl, Entry 4 and TCF5,
ethyl, Entry 5), improved enantioselectivities were obtained.
The importance of a phenyl group at the 5-position of the
triazole was demonstrated by the decreased enantio-
selectivity obtained with the 5-unsubstituted ligand (TCF6,
Entry 6). The use of additives such as Cs2CO3 or Bu4NCl
Scheme 1. Preparation of ThioClickFerrophos (Type I).
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M. Kato, T. Nakamura, K. Ogata, S.-i. Fukuzawa
FULL PAPER
instead of KOAc resulted in lower enantioselectivities (75– Table 2. Optimization of allylic etherification.[a]
76% ee, Entries 7–8). In an attempt to improve the reaction
conditions, the reaction with the most effective ligand
(TCF5) was carried out in other solvents; CH3CN was the
solvent of choice, giving the best % ee value (90% ee, En-
try 9). It should be noted that the reaction in the presence
of the Pd complex of ortho-thioferrocene 3a afforded only
Entry
Ligand
Solvent
Yield [%][b]
ee [%][c]
a trace of the products (Entry 12), suggesting that the P,S-
chelate complex, and not the S,N-chelate complex, was the
active catalyst.
1
2
3
4
TCF5
TCF5
TCF5
TCF5
TCF5
TCF5
TCF5
TCF1
TCF2
TCF3
TCF4
TCF6
CH2Cl2
toluene
CH3CN
THF
95
95
90
27
41
15
36
95
91
82
90
88
69
82
74
62
64
66
75
45
50
55
59
51
Table 1. Asymmetric allylic alkylation.[a]
Yield [%][b]
ee [%][c]
5
Et2O
Entry
Ligand
Solvent
6[d]
7[e]
8
toluene
toluene
toluene
toluene
toluene
toluene
toluene
1
2
3
4
5
6
TCF1
TCF2
TCF3
TCF4
TCF5
TCF6
TCF5
TCF5
TCF5
TCF5
TCF5
3a
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH3CN
THF
97
99
98
99
99
95
97
99
99
96
99
trace
70
67
70
78
84
67
75
76
90
75
75
–
9
10
11
12
7[d]
8[e]
9
[a] Compound 4 (0.5 mmol), benzyl alcohol (1.5 mmol), Cs2CO3
(1.5 mmol), [Pd(η3-C3H5)Cl]2 (0.01 mmol), ligand (0.02 mmol), sol-
vent (3 mL); room temp., 2 h. [b] Isolated yield. [c] Determined by
HPLC (Chiralcel OJ-H). [d] KOAc was used in place of Cs2CO3.
[e] K2CO3 was used in place of Cs2CO3.
10
11
12
toluene
CH2Cl2
[a] Compound 4 (0.5 mmol), dimethyl malonate (1.5 mmol), BSA
(1.5 mmol), KOAc (0.015 mmol), [Pd(η3-C3H5)Cl]2 (0.01 mmol), li-
gand (0.03 mmol), solvent (3 mL); room temp., 15 h. [b] Deter-
mined by 1H NMR spectroscopy. [c] Determined by HPLC (Chi-
ralpak AD-H). [d] Cs2CO3 was used in place of KOAc. [e] Bu4NCl
was used in place of KOAc.
Table 3. Asymmetric allylic etherification.[a]
Asymmetric Allylic Etherification
Unlike allylic alkylation, allylic etherification remains a
challenge for synthetic chemists, and accordingly has yet to
be widely reported. In view of the encouraging results ob-
tained with the [Pd(η3-C3H5)Cl]2/TCF5 complex, we under-
took the asymmetric allylic etherification between benzyl
alcohol and 4 (chosen as a model substrate) in the presence
of the catalyst (4 mol-%) and Cs2CO3 as the base, as shown
in Table 2. In CH2Cl2, the reaction was complete within
2 h at room temp., the R-configured benzyl ether 6 being
obtained quantitatively with 69% ee. Subsequently, the ben-
zyl ether was obtained with 82% ee under optimized reac-
tion conditions with toluene as the solvent and Cs2CO3 as
the base (Table 2, Entries 1–6). Unlike in the allylic alky-
lation, the other ThioClickFerrophos ligands (Entries 9–12;
R, 45–59% ee) were not as effective as TCF5 (Entry 8) for
the allylic etherifications.
As shown in Table 3, the asymmetric allylic etherification
reaction was further evaluated with a substituted benzyl
alcohol. Under optimized reaction conditions, the etherifi-
cations proceeded smoothly to give the corresponding ben-
zylic ethers 6a–e in high yields and with moderate to good
enantioselectivities. The effects of the substituents on the
enantioselectivities were similar to those seen in Chan’s
studies on allylic etherification in the presence of the
FerroNPS ligand – benzylic alcohols bearing electron-with-
drawing groups correspond to lower % ee values.[7a]
Entry
Ar in Alcohol
Yield [%][b]
ee [%][c]
1
2
3
4
5
Ph
99
99
99
85
91
82
80
80
74
74
pMeC6H4
pMeOC6H4
pClC6H4
pFC6H4
[a] Compound 4 (0.5 mmol), benzyl alcohol (1.5 mmol), Cs2CO3
(1.5 mmol), [Pd(η3-C3H5)Cl]2 (0.01 mmol), TCF5 (0.02 mmol), tol-
uene (3 mL); room temp., 5 h. [b] Determined by 1H NMR spec-
troscopy. [c] Determined by HPLC (Chiralcel OJ-H, OD-H).
The Pd/TCF5 complex was also applied to the allylic am-
ination of 4 with benzylamine (Scheme 3). The reaction
proceeded in CH2Cl2 at room temp. over 72 h in the pres-
ence of tetrabutylammonium fluoride (TBAF) to give the
benzylic amine 7 in 91% yield with 66% ee (R).
Scheme 3. Asymmetric allylic amination by Pd/TCF5.
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Eur. J. Org. Chem. 2009, 5232–5238

Ferrocenyl-Based P,S Ligands in Asymmetric Catalysis
1.0, CHCl3). 1H NMR (300 MHz, CDCl3): δ = 0.88 (t, J = 7.3 Hz,
3 H, CH3CH2), 1.90 (dq, J = 7.2, 12.5 Hz, 1 H, one of CH2), 2.00
(d, J = 7.0 Hz, 3 H, CH3CH), 2.0–2.1 (m, 1 H), 4.23 (s, 5 H, Cp),
4.38 (t, J = 2.4 Hz, 1 H), 4.49 (m, 1 H), 4.57 (m, 1 H), 6.13 (q, J
= 7.0 Hz, 1 H, CH3CH), 7.27–7.39 (m, 3 H), 7.51 (s, 1 H, TzH),
7.74 (d, J = 8.2 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
14.5 (CH3), 21.5 (CH3), 30.8 (CH2), 54.8 (CH), 67.5, 68.7, 70.5
(Cp), 76.3, 79.1, 89.0, 117.5, 125.5, 127.9, 128.7, 130.7, 146.9 ppm.
HRMS: calcd. for C22H23FeN3S [M + Na+] 440.0860; found
440.0980.
Compound 3a (R1 = R3 = Ph): Yield 259 mg, 77%, yellow solid,
m.p. 168–170 °C. [α]2D5 = +77.4 (c = 0.5, CHCl3). 1H NMR
(300 MHz, CDCl3): δ = 2.04 (d, J = 7.0 Hz, 3 H, CH3), 4.31 (s, 5
H, Cp), 4.50 (t, J = 1.3 Hz, 1 H), 4.60 (m, 1 H), 4.73 (m, 1 H),
5.95 (q, J = 7.0 Hz, 1 H, CH), 6.68–6.87 (m, 5 H, Ph), 7.03 (s, 1 H,
TzH), 7.24–7.40 (m, 5 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ
= 21.1 (CH3), 54.4 (CH), 68.7, 69.6, 70.7 (Cp), 75.9, 76.7, 90.0,
118.5, 125.3, 125.5, 125.7, 127.5, 128.3, 128.4, 130.7, 138.4,
146.3 ppm. HRMS: calcd. for C26H23FeN3S [M + Na+] 488.0860;
found 488.0862.
Conclusions
In conclusion, we have successfully synthesized novel
ferrocenyl P,S ligands with a triazole backbone (ThioClick-
Ferrophos), which allows the fine-tuning of various steric
and electronic properties of the donor atoms. The Pd com-
plexes of the ThioClickFerrophos ligands were effectively
employed in asymmetric allylic alkylation, etherification,
and amination of (Ϯ)-1,3-diphenylprop-2-enyl acetate (4).
Our results demonstrate that the novel ligand is highly ef-
fective for the reactions, especially for asymmetric allylic
etherifications, and should, with continued fine-tuning of
the framework’s electronic and steric factors, be a promising
ligand.
Experimental Section
1
General: The H and 13C NMR spectra were recorded as solutions
in CDCl3 with a Varian Mercury 300 NMR (300 MHz) spectrome-
ter. The chemical shifts are reported in δ units downfield from the
Me4Si internal reference. The optical rotations were determined
with a JASCO P-2200 instrument. The HPLC analyses were carried
out on chiral columns (Chiralcel AD-H, OJ-H) with a JASCO PU-
1580 apparatus fitted with a multi-wavelength detector (MD 2010).
Preparative TLC was conducted with a 20ϫ20 cm glass sheet
coated with a 2 mm thick layer of Merck Kieselgel 60 PF254. All
products of asymmetric reactions were reported compounds and
were characterized by spectroscopic methods by reference to the
literature.
Compound 3b (R1 = pTol, R3 = Ph): Yield 218 mg, 63%, yellow
solid, m.p. 184–185 °C. [α]2D5 = +74.6 (c = 0.5, CHCl3). H NMR
1
(300 MHz, CDCl3): δ = 1.75 (s, 3 H, CH3), 2.02 (d, J = 7.0 Hz, 3
H, CH3CH), 4.30 (s, 5 H, Cp), 4.48 (t, J = 2.6 Hz, 1 H), 4.61 (m,
1 H), 4.69 (m, 1 H), 5.96 (q, J = 7.0 Hz, 1 H, CH3CH2), 6.62 (s, 4
H), 6.89 (s, 1 H, TzH), 7.18–7.41 (m, 5 H, Ph) ppm. 13C NMR
(75 MHz, CDCl3): δ = 20.3 (CH3), 21.1 (CH3), 54.5 (CH), 68.6,
69.4, 70.7 (Cp), 76.8, 76.9, 89.8, 118.4, 125.3, 126.3, 127.4, 128.3,
129.2, 130.7, 134.5, 135.5, 146.0 ppm. HRMS: calcd. for
C27H25FeN3S [M + Na+] 502.1016; found 502.1006.
Compound 3c (R1 = p-ClC6H4, R3 = Ph): Yield 219 mg, 61%, yel-
low solid, m.p. 194–195 °C. [α]2D5 = +89.0 (c = 0.5, CHCl3). 1H
NMR (300 MHz, CDCl3): δ = 2.01 (d, J = 7.0 Hz, 3 H, CH3), 4.31
(s, 5 H, Cp), 4.50 (t, J = 2.5 Hz, 1 H), 4.58 (m, 1 H), 4.75 (m, 1
H), 5.96 (q, J = 6.8 Hz, 1 H, CH), 6.58 (d, J = 8.2 Hz, 2 H), 6.79
(d, J = 8.2 Hz, 2 H), 7.05 (s, 1 H, TzH), 7.28–7.42 (m, 5 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 21.0 (CH3), 54.5 (CH), 68.8, 69.7,
70.7 (Cp), 75.4, 76.7, 89.9, 118.1, 125.4, 126.8, 127.6, 128.5, 130.3,
131.2, 137.0, 146.5 ppm. HRMS: calcd. for C26H22ClFeN3S [M +
Na+] 522.0470; found 522.0467.
Crystallography: The diffraction data were collected at –150 °C
with a Mercury CCD area detector with use of graphite monochro-
mated Mo-Kα radiation and the ω-2θ scan technique to a maxi-
mum 2θ value of 55°. The structure solution and refinements were
carried out with the aid of the Crystal Structure crystallographic
software packages. The structure was solved by direct methods
(SHELX97) and expanded by Fourier techniques (DIRDIF99).
The non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were refined by use of the riding model.
CCDC-734593 (for TCF1) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Compound 3d (R1 = Cy, R3 = Ph): This compound could not be
isolated in pure form and so was used for the synthesis of TCF4 in
1
the crude state. H NMR (300 MHz, CDCl3): δ = 0.6–1.55 (m, 11
H), 1.97 (d, J = 7.0 Hz, 3 H, CH3), 4.22 (s, 5 H, Cp), 4.38 (m, 1
H), 4.45 (m, 1 H), 4.58 (m, 1 H), 6.15 (q, J = 7.0 Hz, 1 H, CH),
7.28–7.38 (m, 3 H), 7.48 (s, 1 H, TzH), 7.73 (d, J = 7.1 Hz, 2
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 21.6 (CH3), 25.4, 25.5,
25.9, 32.6, 33.6, 47.7, 54.9, 67.5, 68.6, 70.4 (Cp), 77.2, 78.0, 89.2,
111.5, 125.5, 127.8, 128.6, 130.7, 146.9 ppm. HRMS: calcd. for
C26H29FeN3S [M + Na+] 494.1329; found 494.1369.
Preparation of the (S,Rp)-ortho-Thioferrocene: The following pro-
vides a typical experimental procedure for preparation of the ortho-
thioferrocenes. The (S,Rp)-ortho-bromotriazole ferrocene 2a
(300 mg, 0.69 mmol)[9] and dry diethyl ether (30 mL) were placed
under a slight pressure of nitrogen in a 50 mL Schlenk tube con-
taining a magnetic stirring bar. The flask was cooled to –78 °C,
and a hexane solution of nBuLi (0.5 mL, 0.8 mmol, 1.6 ) was then
added by syringe through a septum with magnetic stirring. After
2 h, diethyl disulfide (120 µL, 0.96 mmol) was injected into the mix-
ture at –78 °C. When the addition was complete, the mixture was
stirred at the same temperature for 10 min, and was then allowed
to warm to room temp. and stirred for 24 h. The reaction was
quenched with saturated NH4Cl, and the solution was then ex-
tracted with diethyl ether (3ϫ30 mL). The combined extracts were
washed (brine), dried (MgSO4), and filtered, and the solvent was
removed on a rotary evaporator to leave an orange solid. The crude
product was purified by PTLC (hexane/diethyl ether/dichlorometh-
ane 4:2:1) to give pure 3e (R1 = Et, R3 = Ph). Yield 232 mg,
0.56 mmol, 81%, orange solid, m.p. 52–54 °C. [α]2D5 = +137 (c =
Compound 3f (R1 = Et, R3 = H): Yield 195 mg, 78%, orange oil.
1
[α]2D5 = +132 (c = 0.7, CHCl3). H NMR (300 MHz, CDCl3): δ =
0.88 (t, J = 7.6 Hz, 3 H, CH3CH2), 1.78 (dq, J = 7.3, 12.6 Hz, 1
H, CH3CH2), 1.95 (d, J = 7.0 Hz, 1 H, CH3CH), 1.9–2.03 (m, 1
H), 4.22 (s, 5 H), 4.36 (t, J = 2.6 Hz, 1 H), 4.47 (m, 1 H), 4.56 (m,
1 H), 6.12 (q, J = 7.0 Hz, 1 H, CH3CH), 7.33 (s, 1 H), 7.55 (s, 1
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.4 (CH3), 21.5 (CH3),
30.6 (CH2), 54.6 (CH), 67.4, 68.6, 70.4 (Cp), 76.2, 79.0, 88.9, 121.3
(Tz), 133.0 (Tz) ppm. HRMS: calcd. for C16H19FeN3S [M + Na+]
364.0547; found 364.0520.
Preparation of ThioClickFerrophos: The following provides a typi-
cal experimental procedure for the preparation of ThioClickFer-
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M. Kato, T. Nakamura, K. Ogata, S.-i. Fukuzawa
FULL PAPER
rophos. Compound 3e (150 mg, 0.36 mmol) and dry THF (3.0 mL)
were placed under a slight pressure of nitrogen in a 20 mL Schlenk
tube containing a magnetic stirring bar. The flask was cooled to
–78 °C and a hexane solution of nBuLi (0.24 mL, 0.40 mmol, 1.6 )
was then added by syringe through the septum with magnetic stir-
ring. After 10 min, Ph2PCl (77 µL, 0.43 mmol) was injected into
the mixture at –78 °C and the mixture was stirred for 10 min. The
mixture was allowed to warm to room temp. and was then stirred
for an additional 3 h. The reaction was quenched with saturated
NH4Cl, and the solution was then extracted with diethyl ether
(10 mLϫ3). The combined extracts were washed (brine), dried
(MgSO4), and filtered, and the solvent was removed on a rotary
evaporator to leave a yellow residue. The crude product was puri-
fied by PTLC (hexane/diethyl ether/dichloromethane 4:2:1) to give
pure TCF5. Yield 168 mg, 0.28 mmol, 75%, yellow solid, m.p. 111–
113 °C. [α]2D5 = +155 (c = 0.1, CHCl3). 1H NMR (300 MHz,
CDCl3): δ = 0.90 (t, J = 7.3 Hz, 3 H, CH3CH2), 1.72 (dq, J = 7.0,
12.5 Hz, 1 H, one of CH3CH2), 1.83 (d, J = 6.7 Hz, 3 H, CH3CH),
1.95 (dq, J = 7.3, 12.5 Hz, 1 H, one of CH3CH2), 4.17 (s, 5 H, Cp),
4.30 (t, J = 2.5 Hz, 1 H), 4.42 (m, 1 H), 4.63 (m, 1 H), 6.35 (quint,
J = 7.0 Hz, 1 H, CH3CH), 6.92–7.16 (m, 10 H, Ph), 7.32–7.34 (m,
5 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.6 (CH3), 21.5
(CH3), 30.7 (CH2), 54.5 (d, J = 14.4 Hz, CH), 68.4, 69.2, 70.2 (Cp),
75.9, 78.9, 89.4, 126.6, 127.0, 127.4, 127.5, 128.2 (d, J = 7.1 Hz),
128.7 (d, J = 6.7 Hz), 128.8, 129.2, 131.4, 132.3 (d, J = 6.1 Hz),
132.5 (d, J = 19.6 Hz), 132.7 (d, J = 6.4 Hz), 133.0 (d, J = 19.8 Hz),
152.7 ppm. 31P NMR (121.5 MHz, CDCl3): δ = –34.2 (s) ppm.
HRMS: calcd. for C34H32FeN3PS [M + Na+] 624.1302; found
624.1309.
= 21.6 (CH3), 53.3 (d, J = 16.1 Hz, CH), 70.1, 70.51, 70.52 (Cp),
73.4, 76.2, 90.0, 125.2, 126.4, 126.7, 127.1, 127.8 (d, J = 6.8 Hz),
128.3, 128.4, 128.8 (d, J = 7.9 Hz), 128.9, 129.4, 130.0, 130.9, 131.3
(d, J = 5.0 Hz), 131.8 (d, J = 19.2 Hz), 132.7 (d, J = 7.2 Hz), 133.3
(d, J = 20.3 Hz), 138.6, 151.9 ppm. 31P NMR (121.5 MHz, CDCl3):
δ = –33.6 (s) ppm. HRMS: calcd. for C38H31ClFeN3PS [M + Na+]
706.0912; found 706.0953.
Compound TCF4: Yield 88 mg, 36%, yellow solid, m.p. 62–63 °C.
1
[α]2D5 = +118 (c = 0.1, CHCl3). H NMR (300 MHz, CDCl3): δ =
0.91–1.60 (m, 11 H, Cy), 1.79 (d, J = 7.0 Hz, 3 H, CH3CH), 4.13
(s, 5 H, Cp), 4.27 (t, J = 2.6 Hz, 1 H), 4.40 (m, 1 H), 4.59 (m, 1
H), 6.32 (quint, J = 6.4 Hz, 1 H, CH3CH), 6.94–7.16 (m, 10 H,
Ph), 7.34–7.36 (m, 5 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ
= 21.7 (CH3), 25.6, 25.8, 26.1, 32.8, 33.4, 47.3, 54.6 (d, J = 12.7 Hz,
CH), 68.4, 69.5, 70.3 (Cp), 76.7, 89.5, 126.4, 126.8, 127.4, 128.1 (d,
J = 6.9 Hz), 128.7, 128.8 (d, J = 6.3 Hz), 129.1, 129.2, 131.5, 132.3
(d, J = 5.5 Hz), 132.6 (d, J = 20.7 Hz), 132.7 (d, J = 7.0 Hz), 133.2
(d, J = 19.8 Hz), 152.8 ppm. 31P NMR (121.5 MHz, CDCl3): δ =
–34.1 (s) ppm. HRMS: calcd. for C38H38FeN3PS [M + Na+]
678.1771; found 678.1773.
Compound TCF6: Yield 146 mg, 74%, yellow solid, m.p. 40–42 °C.
[α]2D5 = +106 (c = 0.5, CHCl3). H NMR (300 MHz, CDCl3): δ =
1
0.84 (t, J = 7.3 Hz, 3 H, CH3CH2), 1.54 (dq, J = 7.3, 12.6 Hz, 1
H, one of CH3CH2), 1.74 (d, J = 7.0 Hz, 3 H, CH3CH), 1.83 (dq,
J = 7.3, 12.5 Hz, 1 H, one of CH3CH2), 4.19 (s, 5 H, Cp), 4.28 (t,
J = 2.7 Hz, 1 H), 4.39 (m, 1 H), 4.64 (m, 1 H), 6.29 (dq, J = 2.5,
7.0 Hz, 1 H, CH3CH), 7.16–6.93 (m, 10 H, Ph), 7.36 (s, 1 H,
Tz) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.5 (CH3), 21.1 (CH3),
30.7 (CH2), 54.4 (d, J = 10.3 Hz, CH), 68.4, 69.2, 70.3 (Cp), 76.0,
78.9, 89.0, 128.7 (d, J = 6.4 Hz), 128.8, 128.9, 129.6 (d, J = 7.3 Hz),
133.1, 133.3 (d, J = 16.2 Hz), 133.4, 133.7, 133.8 (d, J = 6.5 Hz),
139.8 ppm. 31P NMR (121.5 MHz, CDCl3): δ = –40.3 (s) ppm.
HRMS: calcd. for C28H28FeN3PS [M + Na+] 548.0989; found
548.1082.
Compound TCF1: Yield 95 mg, 39%, yellow solid, m.p. 202–204 °C.
1
[α]2D5 = +97.7 (c = 0.5, CHCl3). H NMR (300 MHz, CDCl3): δ =
1.74 (d, J = 7.3 Hz, 3 H, CH3), 4.28 (s, 5 H, Cp), 4.51–4.52 (m, 2
H), 4.89 (m, 1 H), 6.35 (quint, J = 7.1 Hz, 1 H, CH), 6.36–6.55 (m,
4 H, Ph), 6.71–7.02 (m, 11 H, Ph), 7.32–7.38 (m, 5 H, Ph) ppm.
13C NMR (75 MHz, CDCl3): δ = 21.7 (CH3), 53.4 (d, J = 16.5 Hz,
CH), 70.0, 70.3, 70.5 (Cp), 74.3, 76.4, 90.9, 124.2, 127.0, 127.1,
127.8 (d, J = 6.5 Hz), 128.1, 128.5, 128.8 (d, J = 7.2 Hz), 129.0,
129.3, 131.2, 131.6 (d, J = 4.9 Hz), 131.9 (d, J = 18.9 Hz), 132.7
(d, J = 6.9 Hz), 133.3 (d, J = 20.3 Hz), 140.1, 151.9 ppm. 31P NMR
(121.5 MHz, CDCl3): δ = –34.1 (s) ppm. HRMS: calcd. for
C38H32FeN3PS [M + Na+] 672.1302; found 672.1303. Crystals suit-
able for X-ray analysis was obtained by recrystallization from
CHCl3/hexane (CCDC-734593).
Type II (R1 = R2 = R3 = Ph): Yield 176 mg, 73%, yellow solid,
m.p. 218–221 °C. [a]2D5 = +224 (c = 0.5, CHCl3). 1H NMR
(300 MHz, CDCl3): δ = 1.70 (d, J = 6.8 Hz, 3 H, CH3CH), 3.68
(m, 1 H), 4.14 (s, 5 H, Cp), 4.41 (m, 1 H), 4.90 (m, 1 H), 6.26 (dq,
J = 3.0, 6.8 Hz, 1 H, CH3CH), 6.70–6.97 (m, 7 H), 7.13–7.47 (m,
11 H), 7.70–7.73 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
21.4 (CH3), 52.0 (d, J = 8.1 Hz, CH), 69.8, 69.9 (Cp), 71.0 (d, J =
2.9 Hz), 71.9 (d, J = 4.0 Hz), 76.1 (d, J = 6.3 Hz), 91.8 (d, J =
24.2 Hz), 121.3, 126.4, 126.7, 127.0, 127.8 (d, J = 6.9 Hz), 127.9,
128.0 (d, J = 5.2 Hz), 128.1, 129.1, 129.3, 130.1, 131.7 (d, J =
19.0 Hz), 134.6, 134.8 (d, J = 20.7 Hz), 136.3 (d, J = 8.6 Hz), 137.3
(d, J = 8.1 Hz), 148.9 ppm. 31P NMR (121.5 MHz, CDCl3): δ =
–25.6 (s) ppm. HRMS: calcd. for C38H32FeN3NaPS [M + Na+]
672.1302; found 672.1332.
Compound TCF2: Yield 165 mg, 67%, yellow solid, m.p. 80–82 °C.
1
[α]2D5 = +74.2 (c = 0.3, CHCl3). H NMR (300 MHz, CDCl3): δ =
1.71 (d, J = 7.0 Hz, 3 H, CH3CH), 2.15 (s, 3 H, CH3), 4.26 (s, 5
H, Cp), 4.50 (m, 2 H), 4.88 (m, 1 H), 6.34 (quint, J = 7.0 Hz, 1 H,
CH3CH), 6.39–6.44 (m, 4 H, tolyl), 6.70–6.98 (m, 10 H, Ph), 7.34–
7.40 (m, 5 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ = 20.6
(CH3), 21.6 (CH3), 53.4 (d, J = 16.1 Hz, CH), 69.9, 70.2, 70.5 (Cp),
74.5, 76.4, 91.0, 124.1, 126.9, 127.0, 127.7 (d, J = 6.7 Hz), 128.1,
128.9 (d, J = 7.2 Hz), 129.0, 129.2, 129.4, 131.2, 131.5 (d, J =
5.2 Hz), 132.0 (d, J = 19.0 Hz), 132.8 (d, J = 7.8 Hz), 133.6 (d, J
= 20.3 Hz), 133.8, 136.5, 151.8 ppm. 31P NMR (121.5 MHz,
CDCl3): δ = –34.1 (s) ppm. HRMS: calcd. for C39H34FeN3OPS [M
+ Na+] 686.1458; found 686.1428.
Allylic Alkylation of (؎)-1,3-Diphenylprop-2-enyl Acetate (4) Cata-
lyzed by a Palladium/TCF Complex: [Pd(η3-C3H5)Cl]2 (3.8 mg,
0.01 mmol, 2 mol-%) and ligand TCF5 (18 mg, 0.03 mmol, 6 mol-
%) dissolved in CH3CN (3.0 mL) were placed in a Schlenk tube
containing a stirring bar. The mixture was stirred under nitrogen at
room temp. for 30 min. Compound 4 (126 mg, 0.5 mmol), dimethyl
malonate (170 µL,1.5 mmol), BSA (370 µL,1.5 mmol), and KOAc
(1.5 mg, 0.015 mmol) were successively added to this solution. The
mixture was stirred at room temp. and monitored by TLC. After
completion (15 h), the mixture was diluted with CH2Cl2 (20 mL),
washed with saturated aqueous NH4Cl, dried (MgSO4), and fil-
tered. The solvent was removed under reduced pressure, and the
brown residue was subjected to PTLC (hexane/ethyl acetate 40:3) to
Compound TCF3: Yield 173 mg, 68%, yellow solid, m.p. 78–80 °C.
[α]2D5 = +55.7 (c = 0.3, CHCl3). H NMR (300 MHz, CDCl3): δ =
1
1.71 (d, J = 7.0 Hz, 3 H, CH3CH), 4.27 (s, 5 H, Cp), 4.49 (m, 1
H), 4.54 (t, J = 2.6 Hz, 1 H), 4.90 (m, 1 H), 6.30 (quint, J = 7.0 Hz,
1 H, CH3CH), 6.44–6.46 (m, 4 H, pClC6H4), 6.78–6.97 (m, 10 H,
Ph), 7.33–7.41 (m, 5 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ
1
give pure 5 (160 mg, 0.49 mmol, 97% yield). H NMR (300 MHz,
5236
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5232–5238

Ferrocenyl-Based P,S Ligands in Asymmetric Catalysis
CDCl3): δ = 3.51 (s, 3 H, CH3), 3.70 (s, 3 H, CH3), 3.96 (d, J = Allylic Amination Catalyzed by Palladium/TCF Complex: [Pd(η3-
10.9 Hz, 1 H, CHCO), 4.26 (dd, J = 8.7, 10.9 Hz, 1 H, CHPh),
6.33 (dd, J = 8.7, 15.7 Hz, 1 H, =CHCH), 6.46 (d, J = 15.7 Hz, 1
H, PhCH=), 7.2–7.3 (m, 10 H) ppm. 13C NMR (7MHz, CDCl3): δ
C3H5)Cl]2 (3.8 mg, 0.01 mmol, 2 mol-%) and TCF5 (18 mg,
0.03 mmol, 6 mol-%) dissolved in dry CH2Cl2 (2.0 mL) were placed
in a Schlenk tube containing a stirring bar, and the mixture was
= 49.0 (CHPh), 52.3 (CH3), 52.5 (CH3), 57.5 (CHCO), 126.3, stirred under nitrogen at room temp. for 30 min. Compound 4
127.1, 127.5, 127.6, 127.7, 127.8, 128.1, 128.4, 128.5, 128.6, 129.0,
131.7, 136.7, 140.0, 167.5 (CO), 168.1 (CO) ppm. The enantiomeric
excess of the product (90% ee) was determined by HPLC [Chi-
(126 mg,0.5 mmol), benzylamine (0.43 g,4.0 mmol), and TBAF
(1  in THF, 1.0 mL, 1.0 mmol) were successively added to this
solution. The mixture was stirred at room temp. and monitored by
ralpack AD-H, 25 cm, hexane/iPrOH 90:10, 1.0 mLmin–1, tR (R) = TLC. After completion (72 h), the mixture was diluted with diethyl
12.9 min, tR (S) = 14.1 min].
ether (20 mL), washed with saturated aqueous NH4Cl, dried
(MgSO4), and filtered. The solvent was removed under reduced
pressure. The brown residue was subjected to PTLC (hexane/ethyl
acetate 40:3) to give pure product (135 mg, 0.45 mmol, 91% yield).
1H NMR (300 MHz, CDCl3): δ = 1.74 (br. s, 1 H), 3.74 (d, J =
13.3 Hz, 1 H, one of PhCH2), 3.78 (d, J = 13.3 Hz, 1 H, one of
PhCH2), 4.37 (d, J = 7.4 Hz, 1 H, CHN), 6.30 (dd, J = 7.4, 15.9 Hz,
1 H, =CH), 6.56 (d, J = 15.9 Hz, 1 H, PhCH=), 7.2–7.4 (m, 15
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 51.3 (CH2), 64.5 (CH),
126.4, 126.9, 127.3, 127.4, 128.1, 128.4, 128.5, 128.6, 130.3, 132.5,
136.8, 140.3, 142.8 ppm. The ee of the product (66%) was deter-
mined by HPLC [Chiracel OJ-H, 25 cm, hexane/iPrOH/
diethylamine 90:10:1, 0.60 mLmin–1, tR (S) = 14.5 min, tR (R) =
17.6 min].
Allylic Etherification Catalyzed by Palladium/TCF Complex:
[Pd(η3-C3H5)Cl]2 (3.8 mg, 0.01 mmol, 2 mol-%) and TCF5 (12 mg,
0.02 mmol, 4 mol-%) dissolved in dry toluene (5.0 mL) were placed
in a Schlenk tube containing a stirring bar, and the mixture was
stirred under nitrogen at room temp. for 30 min. Compound 4
(126 mg,
0.5 mmol),
(p-methoxyphenyl)methanol
(210 µL,
1.5 mmol), and Cs2CO3 (488 mg, 1.5 mmol) were successively
added to this solution. The mixture was stirred at room temp. and
monitored by TLC. After completion (5 h), the mixture was diluted
with ethyl acetate (20 mL), washed with saturated aqueous NH4Cl,
dried (MgSO4), and filtered. The solvent was removed under re-
duced pressure. The brown residue was subjected to PTLC (hexane/
ethyl acetate 95:5) to give pure product 6c (165 mg, 0.50 mmol,
Ͼ99% yield). The enantiomeric excess of the product (80% ee) was
determined by HPLC [Chiralcel OJ-H, 25 cm, hexane/iPrOH 86:14,
0.75 mLmin–1, tR (S) = 13.3 min, tR (R) = 15.4 min]. 1H NMR
(300 MHz, CDCl3): δ = 3.80 (s, 3 H, OCH3), 4.50 (s, 2 H, ArCH2),
4.99 (d, J = 7.0 Hz, 1 H, CHO), 6.33 (dd, J = 7.0, 15.9 Hz, 1 H,
=CH), 6.61 (d, J = 15.9 Hz, 1 H, PhCH=), 6.89 (d, J = 8.5 Hz, 2
H), 7.15–7.42 (m, 12 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
55.2, 69.7, 81.2, 113.8, 126.5, 127.0, 127.7, 128.5, 129.3, 130.3,
130.4, 131.4, 136.5, 141.1, 159.1 ppm.
Supporting Information (see also the footnote on the first page of
1
this article): Copies of H and 13C NMR spectra of ferrocenyl sul-
fide 3a–3f, ThioClickFerrophos TCF1–TCF6, and Type II P,S li-
gand, products of allylic substitutions, 5, 6a–6d, 7, and copies of
their chiral HPLC chart.
Acknowledgments
This study was financially supported by Chuo University (grant for
Special Research).
Compound 6a: 1H NMR (300 MHz, CDCl3): δ = 4.54 (d, J =
12.5 Hz, 1 H, one of PhCH2), 4.60 (d, J = 12.5 Hz, 1 H, one of
PhCH2), 5.00 (d, J = 7.0 Hz, 1 H, CHO), 6.32 (dd, J = 7.6, 15.8 Hz,
1 H, =CH), 6.61 (d, J = 15.8 Hz, 1 H, PhCH=), 7.21–7.44 (m,
15 H) ppm. The enantiomeric excess of the product (81% ee) was
determined by HPLC [Chiralcel OJ-H, 25 cm, hexane/iPrOH 98:2,
0.75 mLmin–1, tR (R) = 17.2 min, tR (S) = 19.6 min].
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Compound 6b: 1H NMR (300 MHz, CDCl3): δ = 2.35 (s, 3 H, CH3),
4.53 (s, 2 H, PhCH2), 5.00 (d, J = 7.0 Hz, 1 H, CHO), 6.33 (dd, J
= 7.0, 15.9 Hz, 1 H, =CH), 6.61 (d, J = 15.9 Hz, 1 H, PhCH=),
7.17–7.44 (m, 15 H) ppm. The enantiomeric excess of the product
(80% ee) was determined by HPLC [Chiralcel OJ-H, 25 cm, hex-
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22.8 min].
= 16.6 min, tR (R) =
ˇ
[4] a) P. Steˇpnicˇka, in: Ferrocenes: Ligands, Materials and Biomole-
Compound 6d: 1H NMR (300 MHz, CDCl3): δ = 4.50 (d, J =
12.4 Hz, 1 H, one of ArCH2), 4.56 (d, J = 12.4 Hz, 1 H, one of
ArCH2), 4.99 (d, J = 7.0 Hz, 1 H, CHO), 6.32 (dd, J = 7.0, 15.9 Hz,
1 H, =CHCH), 6.63 (d, J = 15.9 Hz, 1 H, PhCH=), 7.23–7.43 (m,
15 H) ppm. The enantiomeric excess of the product (74% ee) was
determined by HPLC [Chiralcel OJ-H, 25 cm, hexane/iPrOH 96:4,
0.4 mLmin–1, tR (S) = 17.2 min, tR (R) = 19.6 min].
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Compound 6e: 1H NMR (300 MHz, CDCl3): δ = 4.50 (d, J =
12.6 Hz, 1 H, one of ArCH2), 4.56 (d, J = 12.6 Hz, 1 H, one of
ArCH2), 5.00 (d, J = 7.0 Hz, 1 H, CHO), 6.33 (dd, J = 7.0, 15.9 Hz,
1 H, =CH), 6.61 (d, J = 15.9 Hz, 1 H, PhCH=), 7.04 (t, J = 8.6 Hz,
2 H), 7.20–7.43 (m, 12 H) ppm. The enantiomeric excess of the
product (74% ee) was determined by HPLC [Chiralcel OD-H,
25 cm, hexane/iPrOH 98:2, 0.2 mLmin–1, tR (S) = 21.1 min, tR (R)
= 29.2 min].
Eur. J. Org. Chem. 2009, 5232–5238
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5237

M. Kato, T. Nakamura, K. Ogata, S.-i. Fukuzawa
FULL PAPER
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A chiral ferrocenyl P,S ligand bearing a 1,2,4-triazole group has
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[10]
Received: July 10, 2009
Published Online: September 8, 2009
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5232–5238