Asymmetric synthesis of planar-chiral paracyclophanes by double C-S bond formation: Comparison of catalytic activity and enantioselectivity of Pd and Rh catalysts

Article abstract of DOI:10.1016/j.tetasy.2010.04.008

We have determined that a cationic palladium(II)/(R)-BINAP complex is able to catalyze enantioselective double C-S bond-forming reactions between dithiols and dibenzyl dibromides leading to planar-chiral dithiaparacyclophanes. Although the yields and ee v

Full text of DOI:10.1016/j.tetasy.2010.04.008

Tetrahedron: Asymmetry 21 (2010) 1303–1306
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Asymmetric synthesis of planar-chiral paracyclophanes by double C–S bond
formation: comparison of catalytic activity and enantioselectivity of Pd and
Rh catalysts
Tomoko Hori, Yu Shibata, Ken Tanaka *
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We have determined that a cationic palladium(II)/(R)-BINAP complex is able to catalyze enantioselective
double C–S bond-forming reactions between dithiols and dibenzyl dibromides leading to planar-chiral
dithiaparacyclophanes. Although the yields and ee values of the palladium(II)-catalyzed syntheses of
dithiaparacyclophanes did not exceed our previously reported cationic rhodium(I)/(S)-BINAPHANE com-
plex-catalyzed ones, the palladium(II)-catalyzed reactions allowed the use of commercially available and
inexpensive (R)-BINAP as a ligand. On the other hand, an almost racemic product was obtained by using a
cationic rhodium(I)/(R)-BINAP complex as a catalyst.
Received 22 February 2010
Accepted 1 April 2010
Available online 11 May 2010
Dedicated to Professor Henri Kagan on the
occasion of his 80th birthday
Ó 2010 Elsevier Ltd. All rights reserved.
1
. Introduction
using dithiols and dibenzyl dibromides as coupling partners and
a
cationic rhodium(I)/(S)-BINAPHANE complex as a catalyst
1
3
Planar-chiral paracyclophanes have attracted much attention as
(Scheme 3). Recently, Shibata et al. have reported the enantiose-
lective synthesis of planar-chiral paracyclophanes by palladium-
catalyzed Sonogashira coupling. In this paper, we report double
useful structures for chiral ligands, catalysts, and functional materi-
1
14
als. However, the redundant resolution of racemic compounds has
long been employed for their syntheses.2 Recently, crystallization-
induced or adsorption-induced dynamic resolution of diastereo-
meric mixtures of paracyclophanes was reported for the asymmetric
synthesis of paracyclophanes possessing thermodynamically flexi-
,3
C–S bond formation leading to planar-chiral dithiaparacyclophanes
catalyzed by a cationic palladium(II)/(R)-BINAP complex instead of
the cationic rhodium(I)/(S)-BINAPHANE complex, and a compari-
son of the catalytic activity and enantioselectivity of palladium(II)
and rhodium(I) catalysts.
4
ble ansa chains. However, the straightforward catalytic enantiose-
lective synthesis is more attractive. In 2004 our research group
reported that paracyclophanes can be obtained in good yields by cat-
2
. Results and discussion
alytic aromatization through the cationic rhodium(I)/H
8
-BINAP
complex-catalyzed [2+2+2] cycloaddition (Scheme 1).5
,6
In 1988 Page et al. reported the platinum(II)/dppm complex-cat-
In 2007 we successfully applied this methodology to the first
enantioselective synthesis of planar-chiral metacyclophanes
alyzed coupling reaction of thiols with diiodomethane in refluxing
1
5
acetone using sodium carbonate as a base, while the correspond-
ing reaction using palladium(II) catalyst has not been reported. On
the other hand, we demonstrated that a rhodium(I) complex showed
significantly higher catalytic activity than an iridium(I) complex for
the coupling reaction of thiols and dichloromethane.1 Therefore
we anticipated that a palladium(II) complex would show higher cat-
7
,8
(
Scheme 2). Recently, Shibata et al. applied the rhodium-cata-
lyzed [2+2+2] cycloaddition to the enantioselective synthesis of
chiral cage compounds possessing planar-chirality.9 However,
application to the enantioselective synthesis of planar-chiral para-
cyclophanes has not been reported.
2a
An alternative approach to the synthesis of paracyclophanes is
3 2 2
alytic activity than a platinum(II) complex. Indeed, Pd(PPh ) Cl was
construction of the ansa chain, such as double C–S bond formation
able to catalyze the coupling reaction of arenethiol 1a with less reac-
tive dichloromethane at room temperature to yield the correspond-
ing formaldehyde dithioacetal 2a in 78% yield, which is comparable
leading to dithiaparacyclophanes.3
g,10,11
Our research group re-
3 3
ported the RhCl(PPh ) -catalyzed C–S bond formation of thiols
and polychloroalkanes or alkyl bromides in the presence of
to that using RhCl(PPh
The reaction of less nucleophilic alkanethiol 1b with dichloro-
methane was effectively catalyzed by RhCl(PPh , while Pd
PPh Cl failed to catalyze this reaction. Fortunately, a cationic pal-
3 3
) as a catalyst (Scheme 4).
1
2
Et
3
N. We successfully applied this reaction to the first catalytic
enantioselective synthesis of planar-chiral paracyclophanes by
3 3
)
(
3
)
2
2
ladium(II)/rac-BINAP complex was able to catalyze this reaction,
*
Corresponding author. Tel./fax: +81 42 388 7037.
E-mail address: tanaka-k@cc.tuat.ac.jp (K. Tanaka).
although the product yield was low (Scheme 5).
0
957-4166/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2010.04.008

1
304
T. Hori et al. / Tetrahedron: Asymmetry 21 (2010) 1303–1306
mol %
5
Y
Y
Y
CO Me
[Rh(cod) ]BF /
2
4
2
Z
H -BINAP
8
Z
+
CO Me
CH Cl , rt
2
2
2
Y
CO Me
CO Me
2
2
Y = CH ,O
2
Z = (CH ) (n = 1–6), (CH OCH ) (n = 1–5)
2
n
2
2 n
Scheme 1. Synthesis of paracyclophanes by cationic rhodium(I)/H
8
-BINAP complex-catalyzed [2+2+2] cycloaddition.
Me
Y
5
mol %
S(CH ) CH3
2 11
5
mol % catalyst
O
[
Rh(cod) ]BF /
O
2
4
CH (CH ) SH
3
2 11
O
(R)-H -BINAP
Me
CH Cl -Et N [4:1 (v/v)]
8
2
2
3
S(CH ) CH3
Z
2 11
1
b
rt, 24 h
Y
Z
2b
CH Cl , rt
2
2
O
O
MeO
RhCl(PPh ) : 80% (ref. 12a)
3
3
O
Pd(PPh ) Cl : 2%
3
2
2
OMe
Pd(CH CN) (BF ) /rac-BINAP: 24%
3
4
4 2
Y = CH ,CO
2
Z = (CH ) (n = 1–4), CH OCH
2
n
2
2
Scheme 5. Coupling reaction of alkanethiol 1b with dichloromethane using
rhodium(I) and palladium(II) catalysts.
Scheme 2. Enantioselective synthesis of planar-chiral metacyclophanes by cationic
8
rhodium(I)/(R)-H -BINAP complex-catalyzed [2 + 2 + 2] cycloaddition.
O
Br
O
O
1
0 mol %
PAr2
PPh2
PPh2
PAr2
PAr2
[
Rh(cod) ]BF /
S
2
4
PAr2
SH
R
Z
(
S)-BINAPHANE
R
Z
+
O
SH
THF-Et3N [5:1 (v/v)]
rt
R
S
(R)-BINAP (Ar = Ph) (R)-Segphos (Ar = Ph)
(R)-H -BINAP
8
R
(
(
R)-xyl-BINAP
(R)-DTBM-Segphos
(Ar = 4-MeO-3,5-t-Bu C H )
Br
Ar = 3,5-Me C H )
2
6
3
2 6 2
Scheme 3. Enantioselective synthesis of planar-chiral dithiaparacyclophanes by
cationic rhodium(I)/(S)-BINAPHANE complex-catalyzed double C–S bond
formation.
P
P
Next, we investigated the asymmetric variant of this reaction by
using chiral palladium(II)/axially chiral biaryl bisphosphine (Fig. 1)
complexes as catalysts. Table 1 shows a comparison of catalytic
activity and enantioselectivity between palladium(II) and rho-
dium(I) complexes with axially chiral biaryl bisphosphine ligands
for the reaction of dithiol 3a with dibromide 4a leading to
dithia[9]paracyclophane 5aa. In the rhodium(I) catalysis, the use
of bisphosphine ligands possessing sterically demanding substitu-
ents on the phosphorus showed significantly higher enantioselec-
tivity than the use of bisphosphine ligands possessing sterically
less demanding substituents (phenyl) on the phosphorus (entries
(
S)-BINAPHANE
Figure 1. Structures of axially chiral biaryl bisphosphine ligands.
and small substituents (phenyl) on the phosphorus showed high
enantioselectivities (entries 1 and 2) in the palladium(II) catalysis.
The highest enantioselectivity was obtained by using (R)-BINAP as
a ligand (entry 1).
4
–6 vs entries 1–3), and the use of (S)-BINAPHANE showed the
The scope of the enantioselective dithiparacyclophane synthesis
highest enantioselectivity (entry 6). Dihedral angles of the ligands
also have a small impact on enantioselectivity (entries 1–3), and
using the [Pd(MeCN)
4 4 2
](BF ) /(R)-BINAP complex or the
[Rh(cod) ]BF /(S)-BINAPHANE complex as a catalyst (10 mol %) is
2
4
the use of H
8
-BINAP possessing a large dihedral angle slightly im-
shown in Table 2. In both catalyst systems, the reactions of 1,5-
pentanedithiol 3a with dimethyl-substituted dibenzyl dibromide
4a leading to dithia[9]paracyclophane 5aa proceeded in higher
enantioselectivities than the reactions of 1,6-hexanedithiol 3b
and 1,8-octanedithiol 3c with 4a leading to dithia[10] and
proved the ee value (entry 3). Contrary to rhodium(I) catalysis, the
use of (R)-BINAP and (R)-Segphos possessing small dihedral angles
OMe
[
12]paracyclophanes 5ba and 5ca (entry 1 vs entries 3 and 4). With
S
S
5
mol % catalyst
respect to dibenzyl dibromides, dibromo-substituted dibenzyl
dibromide 4b could also react with 3a, while the ee values of the
corresponding cyclophane 5ab (entry 5) were lower than those
of cyclophane 5aa (entry 1). On the contrary, the reactions of
dithiol 3d with dibromo-substituted dibenzyl dibromide 4b lead-
ing to dithia[3.3]paracyclophane 5db proceeded in higher yields
and enantioselectivities than the reactions of dithiol 3d
with dimethyl-substituted dibenzyl dibromide 4a leading to
dithia[3.3]paracyclophane 5da (entry 6 vs entry 7). Importantly,
the catalyst loadings could be reduced to 2 mol % without erosion
MeO
SH
CH Cl -Et N [4:1 (v/v)]
2
2
3
rt, 24 h
1
a
OMe
2
a
RhCl(PPh ) : 88%
3
3
Pd(PPh ) Cl : 78%
3
2
2
Scheme 4. Coupling reaction of arenethiol 1a with dichloromethane by using
rhodium(I) and palladium(II) catalysts.

T. Hori et al. / Tetrahedron: Asymmetry 21 (2010) 1303–1306
1305
Table 1
Effect of ligands for palladium(II)- and rhodium(I)-catalyzed enantioselective coupling reaction of dithiol 3a with dibromide 4a
a
1
0 mol %
Br
[
Pd(CH CN) ](BF ) /Ligand
3
4
4 2
S
or
[Rh(cod) ]BF /Ligand
Z
Me
Me
SH
SH
2
4
Z
THF-Et N [5:1 (v/v)]
3
Me
S
rt, 16 h
Me
3
a
Br
5aa
[
Z = (CH ) ]
2 3
4
a
Entry
Ligand
Pd catalysis yieldb (%)
ee (%)
Rh catalysis yieldb (%)
ee (%)
1
2
3
4
5
6
(R)-BINAP
(R)-Segphos
43
47
48
42
54
40
43 (ꢀ)
40 (ꢀ)
22 (ꢀ)
28 (ꢀ)
33 (+)
15 (+)
38
45
41
59
53
45
<2
<2
8 (+)
32 (+)
32 (+)
49 (ꢀ)
(R)-H
8
-BINAP
(R)-xyl-BINAP
(R)-DTBM-Segphos
(S)-BINAPHANE
a
[
Pd(CH
3 4 4 2 2 4 3
CN) ](BF ) or [Rh(cod) ]BF (0.025 mmol), ligand (0.025 mmol), 3a (0.25 mmol), 4a (0.25 mmol), Et N (0.8 mL), and THF (4.2 mL) were employed.
b
Isolated yield.
Table 2
Palladium(II)/(R)-BINAP- or rhodium(I)/(S)-BINAPHANE-catalyzed enantioselective coupling reactions of dithiols 3a–d with dibromides 4a,ba
Entry
3 (Z)
4 (R)
5
Catalyst (mol %)
Pd catalysis yieldb (%)
ee (%)
Rh catalysis yieldb (%)
ee (%)
SH
SH
Br
S
Z
R
Z
R
S
R
R
Br
Br
c
1
2
3
4
5
3a [(CH
3a [(CH
3b [(CH
2
)
)
3
]
]
4a (Me)
4a (Me)
4a (Me)
4a (Me)
4b (Br)
5aa
5aa
5ba
5ca
5ab
10
2
10
10
10
43
39
41
33
43
43 (ꢀ)
40 (ꢀ)
8 (ꢀ)
45c
51
49 (ꢀ)
2
3
52 (ꢀ)
c
c
2
)
4
]
39
<2
c
c
3c [(CH
3a [(CH
2
)
6
]
]
17 (+)
6 (+)
11
11 (ꢀ)
c
c
)
2 3
43
27 (ꢀ)
SH
R
S
S
R
R
R
SH
Br
6d
7
3d
3d
4a (Me)
4b (Br)
5da
5db
10
10
6
21
10 (+)
44 (ꢀ)
9c
43
30 (ꢀ)
c
d
c
c
60 (ꢀ)
a
3 4 4 2 2 4 3
Reactions were conducted using [Pd(CH CN) ](BF ) /(R)-BINAP or [Rh(cod) ]BF /(S)-BINAPHANE (0.025 or 0.0050 mmol), 3a–d (0.25 mmol), 4a,b (0.25 mmol), Et N
(
0.8 mL), and THF (4.2 mL) at rt for 16 h.
b
Isolated yield.
Data of Ref. 13.
c
d
3
Reactions were conducted using catalyst (0.025 mmol), 3d (0.25 mmol), 4a,b (0.25 mmol), Et N (1.6 mL), and THF (8.4 mL) at rt for 16 h.
of the product yields and ee values in both palladium(II)- and rho-
dium(I)-catalyzed reactions (entry 2). Although the yields and ee
values of the palladium(II)-catalyzed syntheses of dithiaparacyclo-
phanes did not exceed our previously reported cationic rho-
dium(I)/(S)-BINAPHANE complex-catalyzed ones, the use of the
commercially available and inexpensive BINAP ligand is advanta-
geous than the use of the expensive BINAPHANE ligand.
cationic rhodium(I)/(S)-BINAPHANE complex-catalyzed ones, the
palladium(II)-catalyzed reaction allowed us to use commercially
available and inexpensive (R)-BINAP as a ligand. On the other hand,
an almost racemic product was obtained by using a cationic
rhodium(I)/(R)-BINAP complex as a catalyst.
4
. Experimental
3
. Conclusion
4.1. General
In conclusion, it was found that a cationic palladium(II)/(R)-BIN-
1H NMR spectra were recorded on 300 MHz (JEOL AL 300). 13
C
AP complex is able to catalyze enantioselective double C–S bond-
forming reactions between dithiols and dibenzyl dibromides
leading to planar-chiral dithiaparacyclophanes. Although the
yields and ee values of the palladium(II)-catalyzed syntheses of
dithiaparacyclophanes did not exceed our previously reported
NMR spectra were obtained with complete proton decoupling on
75 MHz (JEOL AL 300). All reactions were carried out under an atmo-
sphere of argon in oven-dried glassware with magnetic stirring.
CH
2 2 3
Cl (No. 27,099-7), THF (No. 18656-2), and Et N (No. 471283)
16
were obtained from Aldrich and used as received. Dibromides 4a

1
306
T. Hori et al. / Tetrahedron: Asymmetry 21 (2010) 1303–1306
and 4b17 were prepared according to the literature. All other re-
Acknowledgments
agents were obtained from commercial sources and used as received
(
without degassing and dehydrating). Dithioacetal 2b was charac-
This work was partly supported by a Grants-in-Aid for Scientific
Research (No. 20675002) from the Ministry of Education, Culture,
Sports, Science, and Technology, Japan. We thank Takasago Interna-
12a
terized in a previous report.
Cyclophanes 5aa, 5ba, 5ca, 5ab,
and 5db were also characterized in a previous report.13
8
tional Corporation for the gift of Segphos, H -BINAP, xyl-BINAP, and
DTBM-Segphos, and Umicore for generous support in supplying a
rhodium complex.
4
.2. General procedure for rhodium(I)-catalyzed coupling
reaction of thiol 1 with dichloromethane (Schemes 4 and 5)
A CH
added to a CH
Et N (0.5 mL). The mixture was stirred at rt for 24 h. The resulting
solution was concentrated and purified by preparative TLC.
2
Cl
2
(0.5 mL) solution of RhCl(PPh
3
)
3
(0.025 mmol) was
References and notes
2
Cl (1.5 mL) solution of thiol 1 (0.500 mmol) and
2
1.
For reviews of cyclophanes, see: (a) Modern Cyclophane Chemistry; Gleither, R.,
Hopf, H., Eds.; Wiley: Chichester, 2004; (b) Cyclophane Chemistry; Vögtle, F.,
Ed.; Wiley: Chichester, 1993.
3
2
.
.
For a review of the cyclophane synthesis, see: Kane, V. V.; De Wolff, W. H.;
Bickelhaupt, F. Tetrahedron 1994, 50, 4574.
For selected recent examples of synthesis of planar-chiral paracyclophanes,
see: (a) Kanomata, N.; Suzuki, J.; Kubota, H.; Nishimura, K.; Enomoto, T.
Tetrahedron Lett. 2009, 50, 2740; (b) Kanomata, N.; Yamada, S.; Ohhama, T.;
Fusano, A.; Ochiai, Y.; Oikawa, J.; Yamaguchi, M.; Sudo, F. Tetrahedron 2006, 62,
4
.3. General procedure for palladium(II)-catalyzed coupling
3
reaction of thiol 1 with dichloromethane (Schemes 4 and 5)
Pd(PPh
0.025 mmol) was added to a CH
0.500 mmol) and Et N (0.5 mL). The mixture was stirred at rt for
4 h. The resulting solution was concentrated and purified by a
preparative TLC.
Pd(CH CN) ](BF
tion of rac-BINAP (0.025 mmol) was added to a CH
solution of [Pd(CH CN) ](BF (0.025 mmol). The mixture was
stirred at rt for 1 h. The resulting solution was added to a CH Cl
1.0 mL) solution of thiol 1 (0.500 mmol) and Et N (0.5 mL). The
3
)
2
Cl
2
catalysis: A CH
2
Cl
2
(0.5 mL) solution of Pd(PPh
3 2 2
) Cl
4
128; (c) Bringmann, G.; Gulder, T. A. M.; Maksimenka, K.; Kuckling, D.;
(
(
2
2
2
Cl (1.5 mL) solution of thiol 1
Tochtermann, W. Tetrahedron 2005, 61, 7241; (d) Kanomata, N.; Nakata, T. J.
Am. Chem. Soc. 2000, 122, 4563; (e) Sato, M.; Uehara, F.; Sato, K.; Yamaguchi,
M.; Kabuto, C. J. Am. Chem. Soc. 1999, 121, 8270; (f) Kanomata, N.; Nakata, T.
Angew. Chem., Int. Ed. 1997, 36, 1207; (g) Pischel, I.; Nieger, M.; Archut, A.;
Vögtle, F. Tetrahedron 1996, 52, 10043. and references therein.
(a) Kanomata, N.; Mishima, G.; Onozato, J. Tetrahedron Lett. 2009, 50, 409; (b)
Ueda, T.; Kanomata, N.; Machida, H. Org. Lett. 2005, 7, 2365; (c) Kanomata, N.;
Oikawa, J. Tetrahedron Lett. 2003, 44, 3625; (d) Kanomata, N.; Ochiai, Y.
Tetrahedron Lett. 2001, 42, 1045.
3
[
3
4
4 2
) /rac-BINAP catalysis: A CH
2
Cl
2
(0.5 mL) solu-
Cl (0.5 mL)
4
.
.
2
2
3
4
4 2
)
2
2
5
8
For our synthesis of cyclophanes by cationic rhodium(I)/H -BINAP complex-
(
3
catalyzed [2+2+2] cycloaddition, see: (a) Tanaka, K.; Sagae, H.; Toyoda, K.;
Noguchi, K. Eur. J. Org. Chem. 2006, 3575; (b) Tanaka, K.; Toyoda, K.; Wada, A.;
Shirasaka, K.; Hirano, M. Chem. Eur. J. 2005, 11, 1145; (c) Tanaka, K.; Shirasaka,
K. Org. Lett. 2003, 5, 4697.
mixture was stirred at rt for 24 h. The resulting solution was con-
centrated and purified by a preparative TLC.
6.
For syntheses of cyclophanes via transition-metal-catalyzed or mediated
macrocyclization, see: Cobalt-catalyzed [2+2+2] cycloaddition: (a) Boñaga, L.
V. R.; Zhang, H.-C.; Moretto, A. F.; Ye, H.; Gautheir, D. A.; Li, J.; Leo, G. C.;
Maryanoff, B. E. J. Am. Chem. Soc. 2005, 127, 3473; (b) Boñaga, L. V. R.; Zhang, H.-
C.; Maryanoff, B. E. Chem. Commun. 2004, 2394; (c) Boñaga, L. V. R.; Zhang, H.-
C.; Gautheir, D. A.; Reddy, I.; Maryanoff, B. E. Org. Lett. 2003, 5, 4537; (d)
Moretto, A. F.; Zhang, H.-C.; Maryanoff, B. E. J. Am. Chem. Soc. 2001, 123, 3157;
4
.4. 1-(4-Methoxyphenyl)sulfanylmethylsulfanyl-4-methoxy-
1
8
benzene 2a
1H NMR (CDCl
J = 8.7 Hz, 4H), 4.15 (s, 2H), 3.79 (s, 6H);
, 300 MHz): d = 7.40 (d, J = 8.7 Hz, 4H), 6.85 (d,
3
13
C NMR (CDCl
3
,
3 3
RhCl(PPh ) -catalyzed [2+2+2] cycloaddition: (e) Kinoshita, H.; Shinokubo, H.;
Oshima, K. J. Am. Chem. Soc. 2003, 125, 7784; Palladium-catalyzed coupling of
enynes: (f) Weibel, D.; Gevorgyan, V.; Yamamoto, Y. J. Org. Chem. 1998, 63,
7
5 MHz): d = 159.5, 134.4, 125.2, 114.5, 55.3, 44.5.
1
217; (g) Saito, S.; Tsuboya, N.; Yamamoto, Y. J. Org. Chem. 1997, 62, 5042;
4
.5. General procedure for palladium(II)-catalyzed enantio-
Cycloaddition of Fischer chromium carbenes with alkynes: (h) Wang, H.; Wulff,
D. W.; Rheingold, L. A. J. Am. Chem. Soc. 2003, 125, 8980; (i) Wang, H.; Wulff, D.
W.; Rheingold, L. A. J. Am. Chem. Soc. 2000, 122, 9862; (j) Dötz, H. K.; Gerhardt,
A. J. Organomet. Chem. 1999, 578, 223; Intramolecular addition of rhodium
carbenes: (k) Doyle, M. P.; Hu, W. Synlett 2001, 1364; (l) Doyle, M. P.; Hu, W.;
Chapman, B.; Marnett, A. B.; Peterson, C. S.; Viatale, P. J.; Stanley, S. A. J. Am.
Chem. Soc. 2000, 122, 5718; Heck reaction: (m) Dyker, G.; Kadzimirsz, D.;
Henkel, G. Tetrahedron Lett. 2003, 44, 7905; (n) Geng, X.; Miller, M. L.; Lin, S.;
Ojima, I. Org. Lett. 2003, 5, 3733.
Tanaka, K.; Sagae, H.; Toyoda, K.; Noguchi, K.; Hirano, M. J. Am. Chem. Soc. 2007,
129, 1522.
For a review of transition-metal-catalyzed synthesis of compounds with non-
centrochirality, see: Ogasawara, M.; Watanabe, S. Synthesis 2009, 1761.
Shibata, T.; Uchiyama, T.; Endo, K. Org. Lett. 2009, 8, 1331.
selective coupling reaction of dithiol 3 with dibromide 4
Table 2)
(
A THF (1.0 mL) solution of (S)-BINAP (0.025 mmol) was added
to a THF (1.0 mL) solution of [Pd(CH CN) ](BF (0.025 mmol).
The mixture was stirred at rt for 1 h. To the mixture was added a
3
4
4 2
)
THF (2.2 mL) solution of dithiol 3 (0.250 mmol) and dibromide 4
7.
8.
9.
(
3
0.250 mmol). Then, Et N (0.8 mL) was added to the mixture. The
mixture was stirred at rt for 16 h. The resulting mixture was con-
centrated and purified by preparative TLC.
1
0. For selected examples, see: (a) Pechlivanidis, Z.; Hopf, H.; Ernst, L. Eur. J. Org.
Chem. 2009, 223; (b) Grimme, S.; Pischel, F.; Vögtle, F.; Nieger, M. J. Am. Chem.
Soc. 1995, 117, 157; (c) Chiu, J.-J.; Hart, H.; Ward, D. L. J. Org. Chem. 1993, 58,
4
.6. General procedure for rhodium(I)-catalyzed enantio-
selective coupling reaction of dithiol 3 with dibromide 4 (Table 2)
9
2
64; (d) Takeshita, M.; Tsuzuki, H.; Tashiro, M. Bull. Chem. Soc. Jpn. 1992, 65,
076; (e) Rossa, L.; Vögtle, F. Top. Curr. Chem. 1983, 113, 1. and references therein.
A THF (1.0 mL) solution of (S)-BINAPHANE (0.025 mmol) was
added to a THF (1.0 mL) solution of [Rh(cod) ]BF (0.025 mmol).
2 4
The mixture was stirred at rt for 1 h. To the mixture was added a
THF (2.2 mL) solution of dithiol 3 (0.250 mmol) and dibromide 4
0.250 mmol). Then, Et N (0.8 mL) was added to the mixture. The
3
mixture was stirred at rt for 16 h. The resulting mixture was con-
centrated and purified by a preparative TLC.
11. For the synthesis of dithiaparacyclophanes by transacetalization, see: (a) Ellis-
Holder, K. K.; Peppers, B. P.; Kovalevsky, A. Y.; Diver, S. T. Org. Lett. 2006, 8,
2511; (b) Ellis, K. K.; Wilke, B.; Zhang, Y.; Diver, S. T. Org. Lett. 2000, 2, 3785.
1
2. (a) Tanaka, K.; Ajiki, K. Org. Lett. 2005, 7, 1537; For our rhodium(I)-catalyzed C–
S and S–S bond-forming reactions, see: (b) Ajiki, K.; Hirano, M.; Tanaka, K. Org.
Lett. 2005, 7, 4193; (c) Tanaka, K.; Ajiki, K. Tetrahedron Lett. 2004, 45, 5677; (d)
Tanaka, K.; Ajiki, K. Tetrahedron Lett. 2004, 45, 25.
(
13. Tanaka, K.; Hori, T.; Osaka, T.; Noguchi, K.; Hirano, M. Org. Lett. 2007, 9, 4881.
14. Kanda, K.; Koike, T.; Endo, K.; Shibata, T. Chem. Commun. 2009, 1870.
1
5. (a) Page, P. C. B.; Klair, S. S.; Brown, M. P.; Smith, C. S.; Maginn, S. J.; Mulley, S.
Tetrahedron 1992, 48, 5933; (b) Page, P. C. B.; Klair, S. S.; Brown, M. P.; Harding,
M. M.; Smith, C. S.; Maginn, S. J.; Mulley, S. Tetrahedron Lett. 1988, 29, 4477.
4
(
.7. (ꢀ)-12,15-Dimethyl-2,9-dithia[10]paracyclophane [(ꢀ)-5ba]
13
Table 2, entry 3)
16. Dahrouch, M.; Jara, P.; Mendez, L.; Portilla, Y.; Abril, D.; Alfonso, G.; Chavez, I.;
Manriquez, J. M.; Riviere-Baudet, M.; Riviere, P.; Castel, A.; Rouzaud, J.;
Gornitzka, H. Organometallics 2001, 20, 5591.
2
D
5
½
aꢁ
¼ ꢀ3:7 (c 1.88, CHCl
3
) 8% ee; CHIRALCEL OD-H, hexane/2-
17. Otsubo, T.; Kohda, T.; Misumi, S. Bull. Chem. Soc. Jpn. 1980, 53, 512.
PrOH = 97:3, 0.7 mL/min, retention times: 19.6 min (major isomer)
18. Cao, Y.-J.; Lai, Y.-Y.; Cao, H.; Xing, X.-N.; Wang, X.; Xiao, W.-J. Can. J. Chem. 2006,
84, 1529.
and 21.9 min (minor isomer).