Rhodium-catalyzed asymmetric ring-opening reactions of N-Boc-azabenzonorbornadiene with N-substituted piperazine nucleophiles

Article abstract of DOI:10.1002/cjoc.201090059

Asymmetric ring-opening reactions of N-Boc-azabenzonorbornadiene with N-substituted piperazine nucleophilesin the presence of 5 mol% of [Rh(COD)Cl]₂ and 10 mol% of chiral ligand, (R,S)-PPF-P-t-Bu₂, gave the corresponding1,2-diamine p

Full text of DOI:10.1002/cjoc.201090059

FULL PAPER
Rhodium-catalyzed Asymmetric Ring-opening Reactions of
N-Boc-azabenzonorbornadiene with N-Substituted
Piperazine Nucleophiles
Long, Yuhua(龙玉华)
Yang, Dingqiao*(杨定乔)
Zeng, Heping(曾和平)
Xie, Lei(谢磊)
Wu, Lihuan(吴利欢)
Mo, Haihong(莫海洪)
Zuo, Xiongjun(左雄军)
School of Chemistry and Environment, South China Normal University, Guangzhou, Guangdong 510006, China
Asymmetric ring-opening reactions of N-Boc-azabenzonorbornadiene with N-substituted piperazine nucleo-
philes in the presence of 5 mol% of [Rh(COD)Cl]2 and 10 mol% of chiral ligand, (R,S)-PPF-P-t-Bu2, gave the cor-
responding 1,2-diamine product in moderate to excellent yields (up to 95%) with reasonable enantiomeric excesses
(up to 70% ee). The results showed that the nature of ligands had significant influence on the yields and the enan-
tiomeric excesses.
Keywords
rhodium catalyst, N-boc-azabenzonorbornadiene, asymmetric ring-opening reaction, chiral
bisphosphine ligand
Introduction
analgesic agents, with high selectivity to κ-opioid ago-
nists.12 Moreover chiral vicinal 1,2-diamines have been
found to be an important subunit in a large number of
bioactive natural products, such as amimotetralins, the
structure of which contains cyclohexane-1,2-diamine,
and which show a broad range of promising biological
activities.13
The catalytic asymmetric carbon-carbon bond and
carbon-heteroatom bond forming reactions have at-
tracted increasing interests in recent years due to their
great potential to offer new methods for the synthesis of
complicated molecules with bioactivities. Asymmetric
ring-opening of oxabenzonorbornadiene mediated by
rhodium catalyst is particularly remarkable, which of-
fers products with more than one stereocenters in a sin-
gle step.1 In general, this type of reaction was highly
efficient and characterized by low catalyst loading in
high yields and enantioselectivities.2 Lautens’s group
has extensively investigated the rhodium-catalyzed
asymmetric ring-opening reactions of oxabenzonorbor-
nadiene with many nucleophiles including alcohols,3
phenols,4 amines,5 carboxylates,6 1,3-dicarbonyl active
methylene nucleophiles,7 sulfur nucleophiles8 and aryl-
boronic acids,9 which demonstrated the great promise to
provide novel and simple routes by optical active com-
pounds. More recently, they have expanded their find-
ings to the asymmetric ring-opening reactions of aza-
benzonorbornadienes with aliphatic and cyclic amines,
which give the corresponding cyclohexane-1,2-diamine
moieties in good yields and enantioselectivities.10
Figure 1 Analgesic cyclohexylene-1,2-diamine compounds.
Herein, we report the asymmetric synthesis of enan-
tiomerically pure 1,2-diamine scaffolds by using rho-
dium-catalyzed ring-opening reactions of N-Boc-aza-
benzonorbornadiene (1) with N-substituted piperazine
nucleophiles, which give the corresponding cyclo-
hexane-1,2-diamines in high yields with reasonable
enantioselectivities. Under mild conditions, the chiral
1,2-diamine was thought to be originated from the
enantioselective cleavage of a bridgehead carbon nitro-
gen bond in N-Boc-azabenzonorbornadiene followed by
an SN2 nucleophilic attack by the N-substituted
piperazine nucleophiles in this type of reaction. We also
describe here the halide effects on the development of
In addition, it was found that 1,2-diamines were ex-
tensively used as chiral auxiliaries for a variety of
asymmetric reactions and scaffolds for the synthesis of
chiral ligands I, II (Figure 1).11 On the other hand,
cyclohexane-1,2-diamine derivatives I and II are potent
*
E-mail: yangdq@scnu.edu.cn; Tel.: 0086-020-39310068; Fax: 0086-020-39310187
Received January 7, 2009; revised June 15, 2009; accepted October 10, 2009.
Project supported by the National Natural Science Foundation of China (Nos. 20772036 and 20802021) and Natural Science Foundation of Guang-
dong Province (Nos. 8251063101000002 and 7005804).
Chin. J. Chem. 2010, 28, 235— 242
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
235

Long et al.
FULL PAPER
the rhodium-catalyzed asymmetric ring-opening reac-
tions of 1 with N-substituted piperazine nucleophiles.
loading. It was further found that under the conditions
of 1 mol% catalyst [Rh(COD)Cl]2, 2 mol% ligand
1,1'-bis(diphenylphosphino)ferrocene
(DPPF),
the
ring-opening reaction of 1 with ethyl piperazine-
1-carboxylate as the nucleophile did not afford the ex-
pected product after 24 h (Table 1, Entry 1).
Results and discussion
For the catalytic asymmetric synthesis of
1,2-diamine scaffolds, the starting material N-Boc pro-
tected azabenzonorbornadiene, 1 was synthesized in
60%—70% using an improved procedure based on the
literature procedures, in which the benzyne, generated
in situ from the treatment of anthranilic acid with isoa-
myl nitrite, reacted with tert-butyl-1-pyrrolecarboxylate
via a [4＋2] cycloaddition (Scheme 1).14 The compound
1 was purified simply through recrystallization from
hexane.
No product was detected even under 2.5 mol% cata-
lyst loading and 5 mol% DPPF (Table 1, Entry 2). Only
trace amount of the product was found after 24 h in the
presence of 5 mol% [Rh(COD)Cl]2 and 10 mol% ligand
(DPPF) (Table 1, Entry 3). To improve the reaction, we
then tested some additives such as ammonium salts.
Among the tested chemical additives, NH4Cl was first
found to remarkably accelerate the reaction to give the
30% yield after 24 h (Table 1, Entry 4). We further
found that NH4I was even better, which gave the ex-
pected product in 92% yield for 6 h (Table 1, Entry 5).
The reaction yields increased in the order of Cl＜Br＜I,
which were accordant with results reported by Lautens’s
group in the asymmetric ring-opening reaction of oxa-
benzonorbornadienes in terms of the anion in the addi-
tive. Many other solvents were tested besides tetrahy-
dropyran (THP) for the reaction including THF, DMF,
benzene and toluene (Table 1). Having developed suit-
able conditions for the ring-opening reaction of 1, we
then focused our work on finding the best ligands.
(S)-BINAP is a common ligand used in asymmetric hy-
drogenation.15 In our investigation, we chose
(S)-BINAP or (R,S)-PPF-P-t-Bu2 as a ligand to carry out
the ring-opening reaction in the presence of rhodium
catalyst. The results (Table 2) showed that these two
ligands are both excellent choices in terms of product
yields, which indeed gave comparable yields for the
same reaction performed. For example, the ring-opening
Scheme 1 Synthesis of N-Boc-azabenzonorbornadiene (1)
Next we attempted to optimize the reaction condition
of the ring-opening of 1. During the primary trials, we
found the rhodium-catalyzed asymmetric ring-opening
reactions of 1 did not give satisfactory results as com-
pared to that of oxabenzonorbornadienes. Both yields
and enantioselectivities were poor, even under the con-
dition of 1 mol% catalyst and excess amount of catalyst
Table 1 Catalyst loading studies
Entry
Catalyst/mol%
Ligand/mol% Additive (3 equiv. to 1)
Solvent
THP
Time/h
24
Yielda/%
nr
1
2
3
4
5
6
7
8
9
1
2.5
5
2
—
5
—
THP
24
nr
10
10
10
10
10
10
10
—
THP
24
trace
30
5
NH4Cl
NH4I
NH4I
NH4I
NH4Br
NH4I
THP
12
5
THP
6
92
5
THF
12
86
5
DMF
Benzene
Toluene
12
90
5
12
78
5
12
80
a Isolated yield after silica column chromatography.
236
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© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 235— 242

Rhodium-catalyzed Asymmetric Ring-opening Reactions
of 1 with ethyl piperazine-1-carboxylate gave 93% yield
with (R,S)-PPF-P-t-Bu2 (Table 2, Entry 1), and the same
reaction gave 90% yield with (S)-BINAP (Table 2, En-
try 2).
Overall, it was found that (S)-BINAP was not a good
chiral ligand in the asymmetric ring-opening reactions
of N-Boc-azabenzonorbornadiene 1 in the presence of
rhodium catalyst. The ee values of the products using
(R,S)-PPF-P-t-Bu2 as a chiral ligand are better, namely
29% (Table 2, Entry 1), 63% (Table 2, Entry 3), and
51% (Table 2, Entry 5), respectively.
4-phenylpiperazine on the reaction, we chose 12 differ-
ent kinds of N-substituted piperazine derivatives (Table
3). Based on the results shown in Table 3, it could be
concluded that the electric effects of the substituents
played an important role in the reaction. [Strong elec-
tron-withdrawing substituted groups on the phenyl ring,
such as CN and COCH3, resulted no products (Table 3,
Entries 6 and 8). Other groups, such as F, gave low
yield (Table 3, Entry 3)]. However, as an electron-
donating group, methoxy on the phenyl ring afforded a
high yield (95%) and the best enantiomeric selectivity
(70% ee, Table 3, Entry 5).
To examine the impact of the substitution groups of
Table 2 Ring-opening reactions of 1 with N-substituted piperazine nucleophiles in the presence of 5% mol [Rh(COD)Cl]2 and 10% mol
bisphosphine ligand
Entry
Nucleophile (5 equiv. to 1)
Ethyl piperazine-1-carboxylate
Piperazine-1-carboxylic acid ethyl ester
1-Benzyl-piperazine
Ligand/10 mol%
(R,S)-PPF-P-t-Bu2
(S)-BINAP
Product
2a
Yielda/%
eeb/%
29
2
1
2
3
4
5
6
93
90
98
95
74
60
2a
(R,S)-PPF-P-t-Bu2
(S)-BINAP
2b
63
21
51
2
1-Benzyl-piperazine
2b
1-(4-Fluorophenyl)piperazine
(R,S)-PPF-P-t-Bu2
2c
1-(4-Fluorophenyl)piperazine
(S)-BINAP
2c
a Isolated yield after silica column chromatography. b Determined by HPLC analysis on a chiralcel OD column.
Table 3 Development of ring-opening reaction with different N-substituted piperazine nucleophiles
Entry
1
Nucleophile (3 equiv. to 1)
R3＝ F; R1, R2, R4, R5＝
R3＝ CH3; R1, R2, R4, R5＝
Time/h
12
Product
2c
Yielda/%
74
eeb/%
H
51
13
33
39
70
0
2
H
H
12
2d
2e
75
3
R1＝ F; R2, R3, R4, R5＝
H
24
44
4
R1＝ CH3; R2, R3, R4, R5＝
R1＝ OCH3; R2, R3, R4, R5＝
24
2f
51
5
H
6
2g
95
6
R3＝ COCH3; R1, R2, R4, R5＝
R1, R2, R3, R4, R5＝
H
24
2h
2i
nr
7
H
24
65
10
0
8
R1＝ CN; R2, R3, R4, R5＝
R2, R3＝ CH3; R1, R4, R5＝
R1, R4＝ CH3; R2, R3, R5＝
R2, R3＝ Cl; R1, R4, R5＝
H
24
2j
nr
9
H
12
2k
2l
85
16
43
47
65
10
11
12
H
12
72
H
12
2m
84
R1, R3＝ F; R2, R4, R5＝
H
24
2n
62
a Isolated yield after silica column chromatography. b Determined by HPLC analysis on a chiralcel OD column.
Chin. J. Chem. 2010, 28, 235— 242
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
237

Long et al.
FULL PAPER
Lautens16 previously reported that 2-halophenols
were poor nucleophiles in the rhodium-catalyzed
asymmetric ring-opening reaction of oxabenzonorbor-
nadienes. In our investigation, 4-(2-substituted phenyl)-
peperazines also gave the product in low yield and en-
antioselectivity (Table 3, Entry 3). N-Phenyl piperazine
without substitution groups on the phenyl ring gave the
product 2i in 65% yield and low enantiomeric selectiv-
ity (Table 3, Entry 7).
The single crystal of 2k, was obtained by solvent-
evaporation of diffusion saturated dichloromethane so-
lution. The center core, 1,4-diazohetero six-membered
ring, adopts a chair conformation. The absolute con-
figurations of two chiral carbons were determined to be
(1S,2S) by X-ray diffraction analysis (Figure 2).17
Experimental
General methods
All flasks were flame-dried under a stream of nitro-
gen and cooled before use. Solvents and solutions were
transferred with syringes and cannulae using standard
1
inert atmosphere techniques. H NMR spectra were re-
corded using a Varian XL 400 MHz spectrometer with
CDCl3 as reference standard (δ 7.24) or some other
suitable solvent. Spectral features are tabulated in the
following order: chemical shift (δ); multiplicity
(s-singlet, d-doublet, t-triplet, q-quartet, m-complex
multiplet, br-broad); coupling constants (J, Hz); number
of protons. 13C NMR spectra were recorded at 100 MHz
with CDCl3 as reference standard (δ 77.0) or some other
suitable solvent. IR spectra were obtained using a
Perkin-Elmer 1730 FT-IR spectrometer as a KBr pellet.
MS data were obtained using a VGZAB-HS mass spec-
trometer. Melting points were taken on an XT-4 micro-
scopically melting point apparatus and are uncorrected.
HPLC analysis was performed on a Waters 600E with
chiralcel OD-H column. A Brucker Smart CCD Appex
II instrument was used for single crystal X-ray diffrac-
tion. Analytical TLC was performed using EM separa-
tion precoated silica gel 0.2 mm layer UV 254 fluores-
cent sheets. Column chromatography was performed as
“flash chromatography” using (100—200 mesh) Merck
grade silica gel. Diethyl ether, benzene and toluene were
distilled from sodium benzophenone ketyl immediately
prior to use. CH2Cl2 was distilled from calcium hydride.
DME was distilled from sodium benzophenone ketyl
and stored. Dimethoxyethane (DMF) was dried and
stored over activated 4 Å molecular sieves. All other
reagents were obtained from Aldrich and used as re-
ceived unless otherwise stated.
Figure 2 Crystal structure of 2k, the data of which are as fol-
lows: Crystal system is orthorhombic, space group P2(1)2(1)2(1)
with unit cell dimensions of a＝ 9.4106(5) Å, b＝ 11.2799(6) Å,
c＝ 23.7096 Å, α＝ β＝ γ＝ 90°, V＝ 2516.8(2) Å3, Z＝ 4, absorp-
tion coefficient is 0.072 cm－ and crystal size is 0.28 mm× 0.23
1
mm× 0.21 mm.
Conclusion
In conclusion, we have investigated and extended
the rhodium-catalyzed asymmetric ring-opening reac-
tions of 1 with N-substituted piperazine nucleophiles,
which afford cyclohexane-1,2-diamine moieties in a
single step. In our investigation, we chose (S)-BINAP or
(R,S)-PPF-P-t-Bu2 as a ligand to carry out the
ring-opening reaction in the presence of rhodium cata-
lyst. The results have shown that (R,S)-PPF-P-t-Bu2 as a
chiral ligand is better than (S)-BINAP. We further opti-
mized the reaction condition by improving the loading
of catalyst and ligands, and NH4I as an additive, which
afforded the expected ring-opened products in high
yields (up to 98%) and reasonable enantiomeric selec-
tivities (up to 70% ee). The results revealed that the na-
ture of the chiral ligand had a significant impact on the
reactivity of the catalyst and the chiral ligand played an
important role in increasing the enantioselectivity in the
Preparation
of
1,4-dihydro-1,4-epiazano-naph-
thalene-9-carboxylic acid tert-butyl ester (1)
To N-tert-butyl 1-pyrrolecarboxylate (1.67 g, 10
mmol ) in dimethoxyethane (DMF) (4 mL) at 50 ℃ in
a flame dried three necked flask fitted with a reflux
condenser and two addition funnels were simultane-
ously added a solution of anthranilic acid (1.37 g, 10
mmol) in DME (10 mL) and a separate solution of iso-
amyl nitrite (1.68 g, 14 mmol, 10 mL) in DME (5 mL).
The [4＋2] cycloaddition reaction took about 45 min,
which was allowed to stir at 50 ℃ for 30 min until no
further gas was evolved. The crude red solution was
concentrated by rotary evaporation to approximately
half the original volume. The reaction mixture was then
partitioned between Et2O and saturated K2CO3 and the
aqueous layer was extracted 3 times with Et2O (10 mL
×3). The combined organic layers were washed with
brine, dried over MgSO4 and concentrated. The result-
ing dark brown oil was further evaporated under re-
duced pressure to remove the isoamyl alcohol byprod-
ring-opening reactions of
1
with N-substituted
piperazine nucleophiles. Further studies are in progress
in order to expand the application of these chiral ligands
to other catalytic asymmetric reactions in our labora-
tory.
238
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© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 235— 242

Rhodium-catalyzed Asymmetric Ring-opening Reactions
ucts. The crude mixture could be purified by repeated
Following the general procedure, compound 2b was
obtained as a white crystal (82.3 mg, 98%) purified by
chromatography on silica gel. Rf＝0.16 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90 ℃)
＝1∶ 1]. The ee was determined to be 63% using HPLC
analysis on a Chiralcel OD-H column, λ＝254 nm. Re-
tention time in 2% isopropanol in hexane was 9.8 min
(major) and 10.6 min (minor). [α]2D0 －40.0 (c 1.00,
recrystallization from hexane which gives 1 in 68%
1
yield as a white solid, m.p. 71—72 ℃; H NMR
(CDCl3, 400 MHz) δ: 1.37 (s, 9H), 5.48—5.60 (m, 2H),
6.98—6.92 (m, 4H), 7.25 (s, 2H); IR (KBr) ν: 3375 (m),
3042 (s), 3016 (w), 2982 (w), 2934 (w), 1912 (s), 1693
(s), 1459 (m), 1450 (s), 1393 (m), 1365 (s), 1337 (s),
1268 (m), 1－165 (s), 1081 (m), 1059 (s), 943 (s), 857 (s),
1
1
831 (m) cm ; MS (ESI) m/z (%): 243 (14), 217 (3), 187
CHCl3), m.p. 134—135 ℃; H NMR (CDCl3, 400
(81), 143 (67), 116 (73), 89 (11), 57 (100). Anal. calcd
for C15H17NO2: 74.05, H 7.04, N 5.76; found C 74.09, H
7.11, N 5.72.
MHz) δ: 1.37 (s, 9H), 2.31 (br s, 4H), 2.47 (br s, 2H),
2.61—2.57 (m, 2H), 3.38—3.40 (m, 2H), 4.51—4.49
(m, 1H), 4.96—4.94 (m, 1H), 5.91 (dd, J＝9.6, 4.8 Hz,
1H), 6.57 (d, J＝9.6 Hz, 1H), 7.00—6.98 (m, 1H),
7.20—7.14 (m, 8H), 7.27—7.25 (m, 1H); 13C NMR
(CDCl3, 100 MHz) δ: 155.41, 138.28, 135.53, 132.58,
129.74, 129.44, 129.08, 128.42, 128.36, 128.27, 128.10,
127.18, 126.92, 79.97, 63.96, 63.25, 53.66, 48.72, 29.94,
28.69. IR (KBr) ν: 3446 (w), 3001 (m), 2976 (s), 2818
(m), 2385 (w), 1720 (s), 1525 (s), 1450 (s), 1363 (s),
Representative procedure for the asymmetric
ring-opening reaction of 1 with N-substituted
piperazine nucleophiles
The ring opening reactions were carried out in a
flame dried round bottomed flask under a stream of dry
nitrogen. In a round bottomed flask containing the rho-
dium iodide DPPF or (R,S)-PPF-P-t-Bu2 or (S)-BINAP
complex (5 mol% to 1) was added 1 (50 mg, 2 mmol) in
－1
1245 (s), 1163 (s), 1001 (s), 742 (m) cm ; MS (ESI)
m/z: 420.13 (M＋1)＋. Anal. calcd for C26H33N3O2: C
74.43, H 7.93, N 10.02; found C 74.41, H 7.92, N 10.01.
(1S,2S)-{2-[4-(4-Fluoro-phenyl)-piperazin-1-yl]-1,
2-dihydronaphthalen-1-yl}-carbamic acid tert-butyl
ester (2c) Following the general procedure, compound
2c was obtained as a white crystal (60.2 mg, 71%) puri-
fied by chromatography on silica gel. Rf＝0.25 on silica
gel plate [V(diethyl ether)∶V(petroleum ether) (60—90
℃)＝1∶ 2]. The ee was determined to be 51% using
HPLC analysis on a Chiralcel OD-H column, λ＝254
nm. Retention time in 2% isopropanol in hexane was
8.9 min (major) and 11.2 min (minor). [α]2D0 －73.3 (c
1.00, CHCl3), m.p. 130—132 ℃; 1H NMR (CDCl3, 400
MHz) δ: 1.46 (s, 9H), 2.72 (br s, 2H), 2.83—2.80 (m,
2H), 3.08—3.03 (m, 4H), 4.63 (d, J＝7.2 Hz, 1H), 5.08
(br s, 1H), 6.03 (t, J＝4.8 Hz, 1H), 6.70 (d, J＝9.6 Hz,
1H), 6.84—6.79 (m, 2H), 6.96 (t, J＝8.0 Hz, 1H), 7.07
(d, J＝8.8 Hz, 1H), 7.13 (d, J＝7.8 Hz, 1H), 7.29—7.23
(m, 3H), 7.39 (d, J＝6.0 Hz, 1H); 13C NMR (CDCl3,
100 MHz) δ: 155.47, 149.59, 135.44, 132.61, 129.94,
129.80, 129.36, 128.57, 128.53, 128.42, 128.38, 128.10,
128.07, 127.00, 118.09, 116.71, 115.77, 115.56, 79.77,
64.08, 50.86, 50.42, 48.98, 28.70, 20.30; IR (KBr) ν:
3348 (w), 2962 (m), 2840 (m), 1680 (s), 1570 (s), 14－06
anhydrous tetrahydropyran (THP,
3
mL). The
red-brown solution was then heated to reflux followed
by addition of ammonium iodide (3 equiv. to 1) and
stirring for 10 min, and then the N-substituted
piperazine nucleophile (3 equiv. to 1) was added. The
mixture was heated to 100 ℃ until the reaction was
complete judged by thin layer chromatography. The
solvents were removed in vacuo and the crude mixture
was purified by flash chromatography to give product.
The ee% was determined by HPLC analysis on a
Chiralcel OD-H column, λ＝254 nm.
(1S,2S)-Ethyl-4-(1-tert-butoxycarbonylamino-1,2-
dihydronaphthalen-2-yl)-piperazine-1-carboxylate
(2a) Following the general procedure, compound 2a
was obtained as a white crystal (74.7 mg, 93%) purified
by chromatography on silica gel. Rf＝0.22 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90 ℃)
＝1∶1]. The ee was determined to be 29% using HPLC
analysis on a Chiralcel OD-H column, λ＝254 nm. Re-
tention time in 2% isopropanol in hexane (0.5 mL/min)
was 16.7 min (major) and 19.8 min (minor). [α]D20
1
－10.0 (c 1.00, CHCl3). m.p. 141—142 ℃; H NMR
(CDCl3, 400 MHz) δ: 1.26—1.22 (m, 3H), 1.46 (s, 9H),
2.60—2.49 (m, 4H), 3.43—3.40 (m, 4H), 4.13—4.06 (q,
J＝6.0 Hz, 2H), 4.58—4.54 (m, 1H), 5.00—5.10 (m,
1H), 5.94 (dd, J＝9.0, 1.8 Hz, 1H), 6.67 (d, J＝10.2 Hz,
1H), 7.10—7.07 (m, 1H), 7.26—7.22 (m, 3H), 7.30—
7.32 (m, 1H); 13C NMR (CDCl3, 100 MHz) δ: 155.61,
155.40, 135.20, 132.53, 129.96, 128.56, 128.40, 127.98,
127.00, 125.40, 79.77, 64.37, 61.43, 48.73, 44.30, 28.64,
14.85; IR (KBr) ν: 3223 (w), 3010 (m), 2973 (s), 2840
(m), 1700 (s), 1530 (s), 1440－(s), 1365 (s), 1250 (s),
1
(s), 1350 (s), 1238 (s), 1168 (s), 1014 (s), 756 (m) cm ;
MS (ESI) m/z: 424.23 (M ＋ 1) ＋ . Anal. calcd for
C25H30FN3O2: C 70.90, H 7.14, N 9.92; found C 70.88,
H 7.13, N 9.90.
(1S,2S)-{2-[4-p-Tolyl-piperazin-1-yl]-1,2-dihydro-
naphthalen-1-yl}-carbamic acid tert-butyl ester (2d)
Following the general procedure, compound 2d was
obtained as a white crystal (62.9 mg, 75%) purified by
chromatography on silica gel. Rf＝0.23 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90
℃)＝1∶2]. The ee was determined to be 13% using
HPLC analysis on a Chiralcel OD-H column, λ＝254
nm. Retention time in 2% isopropanol in hexane was
9.3 min (major) and 11.8 min (minor). [α]2D0 －66.7 (c
1
1172 (s), 1000 (s), 767 (m) cm ; MS (ESI) m/z: 402.24
(M＋1)＋. Anal. calcd for C22H31N3O4: C 65.81, H 7.78,
N 10.47; found C 65.82, H 7.76, N 10.46.
(1S,2S)-[2-(4-Benzyl-piperazin-1-yl)-1,2-dihydron-
aphthalen-1-yl]-carbamic acid tert-butyl ester (2b)
Chin. J. Chem. 2010, 28, 235— 242
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
239

Long et al.
FULL PAPER
1.00, CHCl3), m.p. 126—128 ℃; 1H NMR (CDCl3, 400
MHz) δ: 1.37 (s, 9H), 2.18 (s, 3H), 2.63—2.61 (m, 2H),
2.73—2.71 (m, 2H), 2.99 (t, J＝4.8 Hz, 4H), 4.54 (d,
J＝8.4 Hz, 1H), 4.99 (br s, 1H), 5.95 (dd, J＝10.0, 4.4
Hz, 1H), 6.61 (d, J＝10.0 Hz, 1H), 6.73 (d, J＝8.8 Hz,
2H), 6.98 (d, J＝8.4 Hz, 2H), 7.05—7.02 (m, 1H),
7.18—7.14 (m, 3H), 7.30 (d, J＝6.4 Hz, 1H); 13C NMR
(CDCl3, 100 MHz) δ: 155.44, 149.57, 135.44, 129.87,
129.76, 129.04, 128.48, 128.33, 128.03, 126.96, 125.54,
116.66, 79.97, 64.05, 50.41, 48.86, 29.90, 28.67, 20.67;
IR (KBr) ν: 3346 (w), 2924 (s), 2850 (m), 1680 (s),
1560 (s), 1408 (s), 1365 (w), 1250 (w), 1174 (m), 1016
48.41, 29.86, 28.62, 18.00; IR (KBr) ν: 3344 (w), 3010
(m), 2974 (s), 2814 (m), 2350 (w), 1690 (s), 1585 (s),
1490 (s), 1330 (s), 1220 (s), 1174 (s),＋1014 (s), 767 (m)
C26H33N3O2: C 74.43, H 7.93, N 10.02; found C 74.40,
H 7.90, N 10.01.
－1
cm ; MS (ESI) m/z: 420.17 (M＋1) . Anal. calcd for
(1S,2S)-{2-[4-(2-Anisyl)-piperazin-1-yl]-1,2-dihy-
dronaphthalen-1-yl}-carbamic acid tert-butyl ester
(2g) Following the general procedure, compound 2g
was obtained as a white crystal (82.8 mg, 95%) purified
by chromatography on silica gel. Rf＝0.23 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90 ℃)
＝1∶ 2]. The ee was determined to be 70% using HPLC
analysis on a Chiralcel OD-H column, λ＝254 nm. Re-
tention time in 2% isopropanol in hexane was 13.2 min
(major) and 16.5 min (minor) (Scheme 1). [α]D20
＋
－1
(m), 650 (m) cm ; MS (ESI) m/z: 420.08 (M＋1) .
Anal. calcd for C26H33N3O2: C 74.43, H 7.93, N 10.02;
found C 74.42, H 7.91, N 10.01.
(1S,2S)-{2-[4-(2-Fluorophenyl)-piperazin-1-yl]-1,2-
dihydronaphthalen-1-yl}-carbamic acid tert-butyl
ester (2e) Following the general procedure, compound
2e was obtained as a white crystal (37.3 mg, 44%) puri-
fied by chromatography on silica gel. Rf＝0.19 on silica
gel plate [V(diethyl ether)∶V(petroleum ether) (60—90
℃)＝1∶2]. The ee was determined to be 33% using
HPLC analysis on a Chiralcel OD-H column, λ＝254
nm. Retention time in 2% isopropanol in hexane was
8.7 min (major) and 11.8 min (minor). [α]2D0 －13.3 (c
1.00, CHCl3), m.p. 138—140 ℃; 1H NMR (CDCl3, 400
MHz) δ: 1.38 (s, 9H), 2.53—2.48 (m, 2H), 2.74—2.72
(m, 2H), 2.98—2.93 (m, 4H), 4.54 (d, J＝6.8 Hz, 1H),
5.00 (br s, 1H), 5.96 (dd, J＝10.0, 4.8 Hz, 1H), 6.61 (d,
J＝10.0 Hz, 1H), 6.97—6.95 (m, 4H), 7.06—7.04 (m,
1H), 7.20—7.16 (m, 3H), 7.31 (d, J＝6.0 Hz, 1H); 13C
NMR (CDCl3, 100 MHz) δ: 155.47, 149.52, 135.51,
129.80, 129.72, 129.10, 128.50, 128.31, 128.02, 126.94,
125.52, 116.63, 79.97, 64.04, 61.90, 50.40, 48.84, 28.64.
IR (KBr) νmax: 3346 (w), 3064 (m), 2954 (s), 2870 (m),
2360 (w), 1680 (s), 1502 (s), 1450 (s), 1365 (s), 1236 (s),
1
－160.5 (c 1.00, CHCl3), m.p. 193—194 ℃; H NMR
(CDCl3, 400 MHz) δ: 1.38 (s, 9H), 2.65 (br s, 2H),
2.77—2.75 (m, 2H), 2.94 (d, J＝11.2 Hz, 4H), 3.75 (s,
3H), 4.55 (d, J＝8.0 Hz, 1H), 5.03—5.01 (br s, 1H),
5.96 (dd, J＝9.6, 4.4 Hz, 1H), 6.61 (d, J＝10.0 Hz, 1H),
6.81—6.74 (m, 3H), 6.91—6.87 (m, 1H), 7.04—7.02
(m, 1H), 7.18—7.15 (m, 3H), 7.30 (d, J＝7.2 Hz, 1H);
13C NMR (CDCl3, 100 MHz) δ: 155.69, 152.68, 141.92,
135.73, 132.89, 130.08, 128.69, 128.57, 128.53, 127.21,
125.92, 123.26, 121.38, 118.64, 110.47, 79.97, 64.34,
55.74, 51.58, 49.26, 48.88, 28.97; IR (KBr) ν: 3344 (w),
3062 (m), 2972 (s), 2816 (m), 2360 (w), 1690 (s), 1525
(s), 144－8 (s), 1367 (s), 1248 (s), 1172 (s),＋1028 (s), 752
1
(m) cm . MS (ESI) m/z: 436.15 (M＋1) . Anal. calcd
for C26H33N3O3: C 71.70, H 7.64, N 9.65; found C 71.69,
H 7.73, N 9.64.
(1S,2S)-[2-(4-Phenylpiperazin-1-yl)-1,2-dihydron-
aphthalen-1-yl]-carbamic acid tert-butyl ester (2i)
Following the general procedure, compound 2i was ob-
tained as a white crystal (51.8 mg, 65%) purified by
chromatography on silica gel. Rf＝0.27 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90 ℃)
＝1∶ 2]. The ee was determined to be 10% using HPLC
analysis on a Chiralcel OD-H column, λ＝254 nm. Re-
tention time in 2% isopropanol in hexane was 12.9 min
(major) and 14.8 min (minor). [α]2D0 －10 (c 1.00,
－1
1170 (s), 1014 (s), 756 (m) cm ; MS (ESI) m/z: 424.11
(M＋). Anal. calcd for C25H30FN3O2: C 70.90, H 7.14, N
9.92; found C 70.88, H 7.12, N 9.91.
(1S,2S)-[2-(4-o-Tolylpiperazin-1-yl)-1,2-dihydron-
aphthalen-1-yl]-carbamic acid tert-butyl ester (2f)
Following the general procedure, compound 2f was ob-
tained as a white crystal (42.8 mg, 51%) purified by
chromatography on silica gel. Rf＝0.21 on silica gel
plate [V(diethyl ether)∶V(petroleum ether) (60—90 ℃)
＝1∶ 2]. The ee was determined to be 39% using HPLC
analysis on a Chiralcel OD-H column, λ＝254 nm. Re-
tention time in 2% isopropanol in hexane was 7.4 min
(major) and 9.8 min (minor). [α]2D0 －32.5 (c 1.00,
1
CHCl3), m.p. 156—158 ℃; H NMR (CDCl3, 400
MHz) δ: 1.38 (s, 9H), 2.64 (br s, 2H), 2.75—2.72 (m,
2H), 3.05 (t, J＝5.2 Hz, 4H), 4.60 (d, J＝7.6 Hz, 1H),
5.05 (br s, 1H), 6.02 (dd, J＝9.6, 4.0 Hz, 1H), 6.68 (d,
J＝10.0 Hz, 1H), 6.94—6.90 (m, 3H), 7.07 (d, J＝6.0
Hz, 1H), 7.14—7.11 (m, 5H), 7.27 (d, J＝7.2 Hz, 1H);
13C NMR (CDCl3, 100 MHz) δ: 155.44, 151.62, 135.36,
129.93, 129.56, 128.53, 128.38, 128.06, 127.27, 125.48,
119.79, 116.39, 116.31, 64.06, 79.97, 53.64, 49.81,
48.86, 28.68, 28.30; IR (KBr) ν: 3439 (w), 3050 (m),
2951 (s), 2825 (m), 1608 (s), 1500 (s), 1450 (s), 1360
1
CHCl3), m.p. 168—170 ℃; H NMR (CDCl3, 400
MHz) δ: 1.39 (s, 9H) 2.18 (s, 3H), 2.49—2.46 (m, 2H),
2.60 (t, J＝4.8 Hz, 2H), 2.78—2.76 (m, 4H), 4.55 (d,
J＝8.0 Hz, 1H), 5.02 (br s, 1H), 5.97 (dd, J＝9.6, 4.4
Hz, 1H), 6.61 (d, J＝9.6 Hz, 1H), 6.93—6.90 (m, 2H),
7.08—7.02 (m, 3H), 7.19—7.16 (m, 3H), 7.33—7.31
(m, 1H); 13C NMR (CDCl3, 100 MHz) δ: 155.45,
152.00, 148.30, 135.48, 129.60, 129.07, 128.48, 128.29,
128.01, 126.92, 125.46, 118.61, 64.02, 79.97, 50.49,
－1
(s), 1242 (s), 1135 (s), 991 (s), 781(m) cm ; MS (ESI)
m/z: 406.09 (M＋1)＋. Anal. calcd for C25H31N3O2: C
74.04, H 7.70, N 10.36; found C 74.02, H 7.69, N 10.34.
(1S,2S)-{2-[4-(3,4-Dimethylphenyl)-piperazin-1-
yl]-1,2-dihydronaphthalen-1-yl}-carbamic acid tert-
240
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© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 235— 242

Rhodium-catalyzed Asymmetric Ring-opening Reactions
butyl ester (2k) Following the general procedure,
compound 2k was obtained as a white crystal (72.8 mg,
85%) purified by chromatography on silica gel. Rf＝
0.24 on silica gel plate [V(diethyl ether)∶V(petroleum
ether) (60—90 ℃)＝1∶ 2]. The ee was determined to
be 16% using HPLC analysis on a Chiralcel OD-H
column, λ＝254 nm. Retention time in 2% isopropanol
in hexane was 10.0 min (major) and 11.8 min (minor).
column, λ＝254 nm. Retention time in 2% isopropanol
in hexane was 11.1 min (major) and 19.8 min (minor).
1
[α]2D0 －56.6 (c 1.00, CHCl3), m.p. 128—129 ℃; H
NMR (CDCl3, 400 MHz) δ: 1.37 (s, 9H), 2.71—2.57 (m,
4H), 3.10 (t, J＝4.8 Hz, 4H), 3.50 (d, J＝8.0 Hz, 1H),
4.54 (d, J＝8.0 Hz, 1H), 4.97—4.99 (m, 1H), 5.91 (dd,
J＝9.6, 4.8 Hz, 1H), 6.60 (dd, J＝9.2, 3.2 Hz, 2H),
6.82—6.80 (m, 1H), 7.04—7.02 (m, 1H), 7.18—7.16
(m, 3H), 7.29 (d, J＝6.8 Hz, 1H); 13C NMR (CDCl3,
100 MHz) δ: 155.45, 150.98, 135.22, 132.87, 130.56,
130.04, 128.99, 128.58, 128.44, 128.02, 127.31, 127.04,
125.32, 117.32, 115.47, 79.97, 64.03, 60.18, 49.30,
48.57, 28.68; IR (KBr) ν: 3240 (w), 3035 (m), 2964 (s),
2800 (m), 1680 (s), 1530 (s), 1440 (s), 1351 (s), 12501
1
[α]2D0 －273.3 (c 1.00, CHCl3), m.p. 148—149 ℃; H
NMR (CDCl3, 400 MHz) δ: 1.48 (s, 9H), 2.19 (s, 3H),
2.23 (s, 3H), 2.73—2.71 (m, 2H), 2.81—2.79 (m, 2H),
3.08 (t, J＝4.8 Hz, 4H), 4.66 (d, J＝8.0 Hz, 1H), 5.09
(br s, 1H), 6.05 (dd, J＝9.2, 4.0 Hz, 1H), 6.64 (d, J＝8.0
Hz, 1H), 6.72—6.66 (m, 2H), 7.02 (d, J＝8.0 Hz, 1H),
7.14—7.12 (m, 1H), 7.29—7.24 (m, 3H), 7.40 (d, J＝
6.8 Hz, 1H); 13C NMR (CDCl3, 100 MHz) δ: 155.51,
150.03, 137.24, 135.52, 132.65, 130.32, 129.90, 128.51,
128.35, 128.15, 128.04, 126.99, 125.61, 117.41, 115.09,
79.97, 64.11, 50.49, 48.94, 28.72, 28.44; IR (KBr) ν:
3388 (w), 3032 (m), 2981 (s), 2810 (m), 2360 (w), 1720
(s), 1530 (s), 1448 (s), 1363 (s), 1251 (s), 1138 (s＋), 1006
－1
(s), 1160 (＋s), 1016 (s), 746 (m) cm ; MS (ESI) m/z:
473.94 (M ). Anal. calcd for C25H29Cl2N3O2: C 63.29,
H 6.16, N 8.86; found C 63.26, H 6.14, N 8.84.
(1S,2S)-{2-[4-(2,4-Difluorophenyl)-piperazin-1-yl]-
1,2-dihydronaphthalen-1-yl}-carbamic acid tert-
butyl ester (2n) Following the general procedure,
compound 2n was obtained as a white crystal (53.9 mg,
62%) purified by chromatography on silica gel. Rf＝
0.20 on silica gel plate [V(diethyl ether)∶V(petroleum
ether) (60—90 ℃)＝1∶2]. The ee was determined to
be 65% using HPLC analysis on a Chiralcel OD-H
column, λ＝254 nm. Retention time in 2% isopropanol
in hexane was 7.8 min (major) and 11.4 min (minor).
－1
(s), 746 (m) cm ; MS (ESI) m/z: 434.18 (M＋1) . Anal.
calcd for C27H35N3O2: C 74.79, H 8.14, N 9.69; found C
74.78, H 8.13, N 9.68.
(1S,2S)-{2-[4-(2,5-Dimethylphenyl)-piperazin-1-
yl]-1,2-dihydronaphthalen-1-yl}-carbamic
acid
tert-butyl ester (2l) Following the general procedure,
compound 2l was obtained as a white crystal (62.4 mg,
72%) purified by chromatography on silica gel. Rf＝
0.25 on silica gel plate [V(diethyl ether)∶V(petroleum
ether) (60—90 ℃)＝1∶ 2]. The ee was determined to
be 43% using HPLC analysis on a Chiralcel OD-H
column, λ＝254 nm. Retention time in 2% isopropanol
in hexane was 6.7 min (major) and 8.2 min (minor).
1
[α]2D0 －213.3 (c 1.00, CHCl3), m.p. 135—136 ℃; H
NMR (CDCl3, 400 MHz) δ: 1.39 (s, 9H), 2.79—2.64 (m,
4H), 2.94—2.91 (m, 4H), 4.56 (d, J＝7.6 Hz, 1H), 5.00
—4.97 (m, 1H), 5.96 (dd, J＝9.2, 4.0 Hz, 1H), 6.60 (d,
J＝9.6 Hz, 2H), 6.79—6.74 (m, 3H), 7.02—7.00 (m,
1H), 7.21—7.19 (m, 2H), 7.28—7.26 (m, 1H); 13C
NMR (CDCl3, 100 MHz) δ: 155.42, 150.17, 135.32,
129.93, 129.26, 128.53, 128.38, 128.13, 127.62, 127.47,
126.99, 125.46, 119.58, 79.97, 64.06, 60.00, 51.65,
48.91, 48.46, 47.02, 29.91, 28.65; IR (KBr) ν: 3230 (w),
3060 (m), 2981 (s), 2840 (m), 1700 (s), 1593 (s), 14－40
1
[α]2D0 －33.3 (c 1.00, CHCl3), m.p. 119—120 ℃; H
NMR (CDCl3, 400 MHz) δ: 1.39 (s, 9H) 2.13 (s, 3H),
2.20 (s, 3H), 2.59 (br s, 2H), 2.77—2.72 (m, 6H), 3.40
(d, J＝9.6 Hz, 1H), 4.56 (d, J＝7.6 Hz, 1H), 5.02 (br s,
1H), 5.97 (dd, J＝9.6, 4.4 Hz, 1H), 6.61 (d, J＝9.6 Hz,
1H), 6.70 (d, J＝8.0 Hz, 2H), 6.96 (d, J＝7.2 Hz, 1H),
7.04—7.02 (m, 1H), 7.19—7.15 (m, 2H), 7.33—7.31
(m, 1H); 13C NMR (CDCl3, 100 MHz) δ: 155.41,
151.65, 136.17, 135.52, 132.59, 130.98, 129.70, 129.50,
128.47, 128.28, 128.07, 126.94, 125.93, 123.77, 119.92,
79.97, 64.16, 52.33, 49.35, 48.63, 28.67, 21.39, 17.70;
IR (KBr) ν: 3346 (w), 3010 (m), 2972 (s), 2814 (m),
2358 (w), 1724 (s), 1523 (s), 1450 (s), 1363 (s), 1250 (s),
1
(s), 1365 (s), 1250 (s), 1172 (s), 1000 (s), 760 (m) cm ;
MS (ESI) m/z: 442.07 (M ＋ 1) ＋ . Anal. calcd for
C25H29F2N3O2: C 68.01, H 6.62, N 9.52; found C 68.00,
H 6.61, N 9.51.
References and notes
1
(a) Ward, R. S. Chem. Soc. Rev. 1990, 19, 1.
(b) Magnuson, S. R. Tetrahedron 1995, 51, 2167.
For reviews on transition metal-catalyzed ring-opening re-
actions, see: (a) Lautens, M.; Fagnou, K.; Hiebert, S. Acc
Chem. Res. 2003, 36, 48.
－1
2
1172 (s), 1018 (s), 781 (m) cm ; MS (ESI) m/z: 434.17
(M＋1)＋. Anal. calcd for C27H35N3O2: C 74.79, H 8.14,
N 9.69; found C 74.48, H 8.13, N 9.68.
(b) Yang, D. Q.; Han, Y. F. Chin. J. Org. Chem. 2006, 26,
1613 (in Chinese).
(c) Han, Y. F.; Yang, D. Q.; Liu, E. C.; Dong, J. X. Chin.
Chem. Lett. 2006, 17, 296.
(d) Liu, E. C.; Yang, D. Q.; Han, Y. F.; Dong, J. X. Chin.
Chem. Lett. 2006, 17, 717.
(e) Yang, D. Q.; Zeng, H. P. Chin. Chem. Lett. 2003, 14,
697.
(1S,2S)-{2-[4-(3,4-Dichlorophenyl)-piperazin-1-yl]-
1,2-dihydronaphthalen-1-yl}-carbamic
acid
tert-butyl ester (2m) Following the general procedure,
compound 2m was obtained as a white crystal (79.7 mg,
84%) purified by chromatography on silica gel. Rf＝
0.22 on silica gel plate [V(diethyl ether)∶V(petroleum
ether) (60—90 ℃)＝1∶ 2]. The ee was determined to
be 47% using HPLC analysis on a Chiralcel OD-H
Chin. J. Chem. 2010, 28, 235— 242
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
241

Long et al.
FULL PAPER
(f) Yang, D. Q.; Long, Y. H.; Wang, H.; Zhang, Z. M. Org.
Lett. 2008, 10, 4723.
(a) Lautens, M.; Fagnou, K.; Rovis, T. J. Am. Chem. Soc.
2000, 122, 5650.
(b) Lautens, M.; Fagnou, K.; Taylor, M. Org. Lett. 2000, 2,
1677.
Lautens, M.; Fagnou, K.; Taylor, M.; Rovis, T. J. Or-
ganomet. Chem. 2001, 624, 259.
36, 2282.
12 Costello, G. F.; James, R.; Shaw, J. S.; Slater, A. M.;
Smtchbury, N. C. J. Med. Chem. 1991, 34, 181.
3
13 Vliet, L. A.; Tepper, P. G.; Dijkstra, D.; Damsma, G.; Wik-
stron, H.; Pugsley, T. A.; Akunme, H. C.; Heffner, T. G.;
Glase, S. A.; Wise, L. D. J. Med. Chem. 1996, 39, 4233.
14 Cho, Y. H.; Fayol, A.; Lautens, M. Tetrahedron: Asymmetry
2006, 17, 416.
4
5
Lautens, M.; Fagnou, K. J. Am. Chem. Soc. 2001, 123,
7170.
Lautens, M.; Fagnou, K. Tetrahedron 2001, 57, 5067.
Lautens, M.; Fagnou, K.; Yang, D. Q. J. Am. Chem. Soc.
2003, 125, 14884.
15 Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.;
Souchi, T.; Noyori, R. J. Am. Chem. Soc. 1980, 102, 7932.
16 Lautens, M.; Rovis, T. J. Org. Chem. 1997, 62, 5246.
17 Crystal data for 2k: C27H34N3O2, Mr＝ 432.57, orthorhombic,
space group P2(1)2(1)2(1), a＝ 9.4106(5) Å, b＝ 11.2799(6)
Å, c＝ 23.7096(13) Å, α＝ β＝ γ＝ 90°, V＝ 2516.8(2) Å3, Z
6
7
8
9
Leong, P.; Lautens, M. J. Org. Chem. 2004, 69, 2194.
Lautens, M.; Dockendorff, C. Org. Lett. 2003, 5, 3695.
＝
4, Dc＝ 1.142 Mg/m3, m＝ 0.072 mm－ 1, F(000)＝ 932.
10 (a) Lautens, M.; Fagnou, K.; Zunic, V. Org Lett. 2002, 4,
3465.
(b) Cho, Y.; Zunic, V.; Senboku, H.; Olsen, M.; Lautens, M.
J. Am. Chem. Soc. 2006, 128, 6837.
11 (a) Lucet, D.; Le Gall, T.; Mioskowski, C. Angew. Chem.,
Int. Ed. 1998, 37, 2580.
30045 reflections were collected, of which 5819 were con-
sidered to be observed with I＞ 2σ (Io). The structure was
determined by direct methods using the SHELXL-97 suite
of program. Hydrogen atoms were placed in calculated po-
sitions. Full-matrix least squares refinement based on F2
with anisotropic thermal parameters for the non-hydrogen
atoms led to agreement factors R1＝ 0.0600 and wR2＝
0.1680.
(b) Bennani, Y. L.; Haenssian, S. Chem. Rev. 1997, 97,
3161.
(c) Hoppe, D.; Hense, T. Angew. Chem., Int. Ed. Engl. 1997,
(E0901071 Zhao, X.; Lu, Z.)
242
www.cjc.wiley-vch.de
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 235— 242