Iridium-catalyzed asymmetric ring opening of azabicyclic alkenes by amines

Article abstract of DOI:10.1021/jo101470r

The enantioselective ring-opening reactions of azabicyclic alkenes with primary and secondary aromatic amine nucleophiles are reported using an iridium catalyst generated in situ from 1.5 mol % of [Ir(COD)Cl]₂ and 3 mol % of (S)-BINAP. The reac

Full text of DOI:10.1021/jo101470r

pubs.acs.org/joc
Iridium-Catalyzed Asymmetric Ring Opening of Azabicyclic
Alkenes by Amines
Yuhua Long,† Dingqiao Yang,*,† Zhenming Zhang,† Yujuan Wu,† Heping Zeng,† and
Yu Chen*,‡
†School of Chemistry and Environment, South China Normal University, Guangzhou 510006,
People’s Republic of China, and ‡Department of Chemistry and Biochemistry, Queens College,
City University of New York, 65-30 Kissena Boulevard, Flushing, New York 11367, United States
yangdq@scnu.edu.cn; yu.chen1@qc.cuny.edu
Received July 30, 2010
The enantioselective ring-opening reactions of azabicyclic alkenes with primary and secondary
aromatic amine nucleophiles are reported using an iridium catalyst generated in situ from 1.5 mol %
of [Ir(COD)Cl]2 and 3 mol % of (S)-BINAP. The reaction affords the corresponding trans-1,2-diamine
derivatives in moderate to good yields with moderate to high enantioselectivities (up to 97% ee). The
trans-configuration of the 1,2-diamino product 2g was confirmed by X-ray crystallography.
Introduction
alkynes,8 organic halides,9 amines,10 Grignard reagents,11
methanol,12 and others.13 Iridium-catalyzed allylic substitution
is an efficient protocol for the construction of both carbon-
carbon bonds and carbon-heteroatom bonds providing a
feasible way to generate multifunctional chiral building
blocks.14,15 Ring-opening reaction of azabenzonorbornadienes
Ring-opening reactions of oxa- and azabicyclic olefins are
exceedingly important methods of great utility in synthetic
chemistry. Recently, this area has been paid increasing
attention and extensively investigated.1 Many parameters
have been examined for these reactions, including a variety
of metal catalysts such as Rh,2 Pd,3 Cu,4 and Ni5 etc., and
nucleophiles such as dialkylzincs,2a,6 organoboronic acids,7
(9) Hen, C. L.; Martin, S. F. J. Org. Chem. 2006, 71, 4810–4817.
(10) Cho, Y. H.; Zunic, V.; Senboku, H.; Olsen, M.; Lautens, M. J. Am.
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Yoshida, K.; Yanagisawa, A.; Imamoto, T. Org. Lett. 2009, 11, 2245–2248.
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444–445.
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Cheng, C. H. J. Org. Chem. 2004, 69, 8407–8412.
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2002, 124, 15164–15165. (b) Alexakis, A.; Hajjaji, S. E.; Polet, D.; Rathgeb,
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Hartwig, J. F. J. Am. Chem. Soc. 2007, 129, 7508–7509. (d) Kanayama, T.;
Yoshida, K.; Miyabe, H.; Kimachi, T.; Takemoto, Y. J. Org. Chem. 2003, 68,
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7, 1621–1624. (i) Kanayama, T.; Yoshida, K.; Miyabe, H.; Kimachi, T.;
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DOI: 10.1021/jo101470r
r
Published on Web 10/13/2010
J. Org. Chem. 2010, 75, 7291–7299 7291
2010 American Chemical Society

Long et al.
JOCArticle
represents a type of allylic substitution reaction in which the
reaction proceeds under relatively mild conditions, leading to a
variety of 1,2-diamino compounds in both high yields and
excellent enantioselectivities. Lautens and co-workers16 have
extensively investigated Rh-catalyzed asymmetric ring-opening
reactions of azabenzonorbornadienes with amines (up to 99%
ee) and successfully employed them in the preparation of new
chiral ligands17 and analgesic compounds.18 Recently, we have
reported Rh-19 and Ir-catalyzed20 asymmetric ring-opening
reactions of N-Boc-azabenzonorbornadiene with N-substi-
tuted piperazine nucleophiles in high yields and high enantio-
selectivities. Our interest in generating carbon-nitrogen bonds
has prompted us to expand the scope of the reaction to include
primary aromatic amine as well as cyclic and acyclic secondary
amine-induced ring openings of azabicyclic alkenes for an
efficient access to trans-1,2-diamine moieties with high regio-,
diastereo-, and enantioselectivities. These methods offer poten-
tially useful synthetic routes to trans-1,2-diamines which are the
scaffolds for chiral ligands21 and valuable intermediates for
total synthesis of bioactive compounds.22
TABLE 1. Ligand Optimization for Iridium-Catalyzed Asymmetric
Ring-Opening of N-Boc-Azabenzonorbornadiene 1 with N-Methylanilinea
In this paper, we report the full details of the catalytic asym-
metric ring-opening reactions of N-substituted azabenzonorbor-
nadienes 1, 3, and 5 with a wide variety of amines in the presence
of iridium catalysts. The reaction affords the corresponding
trans-1,2-diamine derivatives in moderate to good yields with
moderate to excellent enantioselectivities (up to 97% ee).
entry [Ir(COD)Cl]2
ligand
yieldb (%) eec (%)
1
2
3
4
5
1.0 mol % 2 mol % DPPF
1.5 mol % 3 mol % DPPF
71
86
83
10
nr
0
0
0
20
2.0 mol % 4 mol % DPPF
1.5 mol % 3 mol % (R)-(S)-PPF-PtBu2
1.5 mol % 3 mol % (S)-(R)-NMe2-
PPh2-Mandyphos
6
7
8
9
10
1.5 mol % 3 mol % (S)-BINAP
1.5 mol % 3 mol % (S)-p-Tol-BINAP
1.5 mol % 3 mol % L1
1.5 mol % 1.5 mol % (S)-BINAP
1.5 mol % 4.5 mol % (S)-BINAP
56
10
nr
6
84
70
Results and Discussion
The substrates 1, 3, and 5 were prepared according to the
literature procedures.20a,7,16b An achiral ligand 1,10-bis(diphenyl-
phosphino)ferrocene (DPPF) was first chosen to validate the
43
62
30
aThe reaction was carried out with 1 (0.21 mmol) and 3.0 equiv of
N-methylaniline (0.63 mmol) in THF (2.0 mL) at 80 °C (oil bath
temperature). bIsolated yield after silica gel column chromatography.
cDetermined by HPLC with a Chiralcel AD-H column.
(15) For selected recent examples on iridium-catalyzed allylations, see:
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Helmchen, G. Chem.;Eur. J. 2010, 16, 6601–6615. (b) Spiess, S.; Raskatov,
J. A.; Gnamm, C.; Broedner, K.; Helmchen, G. Chem.;Eur. J. 2009, 15,
11087–11090. (c) Spiess, S.; Welter, C.; Franck, G.; Taquet, J.-P.; Helmchen,
G. Angew. Chem., Int. Ed. 2008, 47, 7652–7655. (d) Helmchen, G.; Dahnz, A.;
Duebon, P.; Schelwies, M.; Weihofen, R. Chem. Commun. 2007, 675–691.
(16) (a) Cho, Y. H.; Fayol, A.; Lautens, M. Tetrahedron: Asymmetry
2006, 17, 416–427. (b) Lautens, M.; Fagnou, K.; Zunic, V. Org. Lett. 2002, 4,
3465–3468. (c) McManus, A. H.; Fleming, M. J.; Lautens, M. Angew. Chem.,
Int. Ed. 2007, 46, 433–436.
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37, 2580–2627. (b) Hoppe, D.; Hense, T. Angew. Chem., Int. Ed. Engl. 1997, 36,
2282–2316. (c) Beak, P.; Basu, A.; Gallagher, D. J.; Park, Y. S.; Thayumanavan,
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Chem. Rev. 1996, 96, 395–422. (e)Trost,B.M.;VanVranken,D. L.;Bingel, C.J.
Am. Chem. Soc. 1992, 114, 9327–9343. (f) Trost, B. M.; Bunt, R. C.; Lemoine,
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1981, 24, 1230–1236. (b) Cowan, A.; Gmerek, D. E. Trends Pharmacol. Sci. 1986,
7, 69–72. (c) Millan, M. J. Trends Pharmacol. Sci. 1990, 11, 70–76.
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Y. F.; Dong, J. X. Chin. Chem. Lett. 2006, 17, 717–719.
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2008, 10, 4723–4726. (b) Long, Y.-H.; Zhao, S.-Q.; Zeng, H.-P.; Yang, D.-Q.
Catal. Lett. 2010, 138, 124–133. (c) Long, Y.-H.; Yang, D.-Q.; Zeng, H.-P.;
Xie, L.; Wu, L.-H; Mo, H.-H.; Zuo, X.-J. Chin. J. Chem. 2010, 28, 235–242.
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catalytic activity of the iridium complex in the ring-opening
reactions of N-Boc-azabenzonorbornadiene with N-methylani-
line. In the presence of 1 mol % of [Ir(COD)Cl]2 and 2 mol % of
DPPF, the desired ring-opening product was obtained in a 71%
yield (Table 1, entry 1). The yield was increased to 86% when 1.5
mol % of [Ir(COD)Cl]2 and 3 mol % of DPPF were employed
(Table 1, entry 2). However, further increase of the catalyst
loading did not improve the yield (Table 1, entry 3). Several
chiral ligands such as (R)-(S)-PPF-PtBu2, (S)-(R)-NMe2-PPh2-
Mandyphos, (S)-BINAP, (S)-p-Tol-BINAP, and L1 were then
examined. From Table 1, we can see that (S)-BINAP gave
the best yield and enantioselectivity when the molar ratio of
(S)-BINAP to iridium was 2:1 (Table 1, entry 6). While the
molar ratio of (S)-BINAP to iridium changed to 1:1 or 3:1, the
ring-opening reaction gave a lower yield and enantioselectivity
(Table 1, entries 9 and 10). Other ligands such as (R)-(S)-PPF-
PtBu2, (S)-(R)-NMe2-PPh2-Mandyphos, (S)-p-Tol-BINAP,
and L1 gave either unsatisfactory results (Table 1, entries 4
and 7) or no reaction (Table 1, entries 5 and 8).
In order to obtain better yields and higher enantioselec-
tivities for the asymmetric ring-opening reaction of aza-
benzonorbornadiene with amine nucleopiles, a number of
parameters including solvents, temperature, and additives
have therefore been investigated. It was found that solvents
played a significant role in improving both reactivity
and enantioselectivity. The optimal solvent turned out to
be tetrahydrofuran (THF). Iridium-catalyzed asymmetric
(22) (a) Alexander van Vliet, L.; Tepper, P. G.; Dijkstra, D.; Damsma, G.;
Wikstrom, H.; Pugsley, T. A.; Akunne, H. C.; Heffner, T. G.; Glase, S. A.;
Wise, L. D. J. Med. Chem. 1996, 39, 4233–4237. (b) Degnan, A. P.; Meyers,
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Antibiot. Ser. A 1996, 19, 200–209.
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TABLE 2. Condition Screening for Iridium-Catalyzed Asymmetric
Ring-Opening Reaction of N-Boc-Azabenzonorbornadiene 1 with
N-Methylanilinea
TABLE 3. Iridium-Catalyzed Asymmetric Ring-Opening of 1 with
Secondary Amine Nucleophilesa
entry
solvent
additive
time (h)
yieldb (%)
eec (%)
1
2
3
4
5
6
7
8
9
CH3CN
toluene
CH2Cl2
dioxane
THP
48
48
48
48
48
48
48
48
48
48
48
48
79
19
21
39
68
56
trace
52
56
43
87
61
64
84
THF
THFd
THFe
THF
78
60
NH4I
12.5
trace
78
10
11
12
THF
THF
THF
NH4Br
Bu4NI
Et3NHCl
62
80
13
aThe reaction was carried out with 1 (0.21 mmol) and 3.0 equiv of
N-methylaniline (0.63 mmol) in solvent (2.0 mL) at 80 °C (oil bath
temperature) in the presence of [Ir(COD)Cl]2 (1.5 mol %) and (S)-BINAP
(3 mol %). bIsolated yield after silica gel column chromatography.
cDetermined by HPLC with a Chiralcel AD-H column. dOil bath tempera-
ture is 60 °C. eOil bath temperature is 100 °C.
ring-opening reaction of N-Boc-azabenzonorbornadiene 1
with N-methylaniline afforded the corresponding product
2a in a 56% yield and 84% ee in THF (Table 2, entry 6). The
same reaction afforded the expected product 2a in a 79%
yield and 56% ee in CH3CN (Table 2, entry 1). In CH2Cl2,
the desired product 2a was obtained only in a low yield
(21%) though with a high enantioselectivity (87% ee)
(Table 2, entry 3). In addition, both modest yields and
enantioselectivities were obtained when other solvents such
as toluene, dioxane, and THP were employed (Table 2,
entries 2, 4, and 5). Temperature also plays a crucial role
in this ring-opening reaction. Although a 56% yield and
an 84% ee were obtained at 80 °C (Table 2, entry 6), only
a trace amount of ring-opening product was obtained at
60 °C after 48 h (Table 2, entry 7). On the other hand, the
reaction afforded the desired product in a lower yield and
enantioselectivity when the temperature was increased to
100 °C (Table 2, entry 8). The role of ammonium halide
additives was also explored. It turned out they were not
necessary in this reaction (Table 2, entries 9-12).
aThe reaction was carried out with 1 (0.21 mmol) and 3.0 equiv of
amine (0.63 mmol) in THF (2 mL) at 80 °C (oil bath temperature) in the
presence of [Ir(COD)Cl]2 (1.5 mol %) and (S)-BINAP (3 mol %).
bIsolated yield after silica gel column chromatography. cDetermined
by HPLC with a chiral stationary column (Chiralcel AD-H column for
2a, 2b, 2c, 2f, and 2g; Chiralcel OD-H column for 2h, 2i, 2j, and 2k). dThe
reaction solvent is THP at 100 °C (oil bath temperature).
On the basis of these studies, the asymmetric ring opening of
1 with a variety of N-alkylanilines and aliphatic amines was
explored under the optimal reaction conditions: 1.5 mol % of
[Ir(COD)Cl]2 and 3 mol % of (S)-BINAP in THF at 80 °C. In
general, N-alkylanilines reacted with 1 to give the correspond-
ing products in higher yields and enantioselectivities (Table 3,
entries 1-8) than substituted aliphatic amines (Table 3, entries
9-11). The substituent on the aniline nitrogen has a significant
impact on both the chemical yield and enantioselectivity
(Table 3, entries 1-4). Due to the steric bulkiness of the cyclo-
hexyl group, the ring-opening reaction by N-cyclohexylaniline
did not afford any desired product (Table 3, entry 4). A similar
result was observed when 2-chloro-N-methylaniline was used
as the nucleophile in the ring opening (Table 3, entry 5). The
yields decreased in the case of 4-nitro- or 4-bromo-N-methyl-
aniline nucleophiles, presumably due to the effect of the electron-
withdrawing substitutents (Table 3, entries 6 and 7).
In order to extend the scope of this reaction to other sub-
strates, we then examined the ring opening of 6,7-dimethoxy-
N-Boc-azabenzonorbornadiene (3) by amines. An obvious
increase in terms of enantioselectivity was observed when
N-methylaniline instead of N-ethylaniline was used as the
nucleophile (Table 4, entries 1 and 2). Only moderate
enantioselectivities were obtained when secondary aliphatic
amines such as 1,2,3,4-tetrahydroquinoline and 1-phenylpiper-
azine were employed (Table 4, entries 3 and 4). No ring-opening
product of substrate 3 was observed when piperidine was used
as the nucleophile (Table 4, entry 5).
The asymmetric ring-opening reactions of N-Ts-azaben-
zonorbornadiene 5 with secondary amines were also inves-
tigated. It was known that these ring-opening reactions
afforded the products in high yield (90%) but low enantio-
selectivity (10% ee) in the presence of a rhodium catalyst
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Long et al.
JOCArticle
TABLE 4. Iridium-Catalyzed Asymmetric Ring Opening of 3 with
Secondary Amine Nucleophilesa
TABLE 5. Iridium-Catalyzed Asymmetric Ring-Opening of 5 with
Secondary Amine Nucleophilesa
aThe reaction was carried out with 5 (0.20 mmol) and 3.0 equiv of
amine (0.60 mmol) in THF (2.0 mL) at 80 °C (oil bath temperature) in
the presence of [Ir(COD)Cl]2 (1.5 mol %) and (S)-BINAP (3 mol %).
bIsolated yield after silica gel column chromatography. cDetermined by
HPLC with a chiral stationary column (Chiralcel AD-H column for 6c;
Chiralcel OD-H column for 6a and 6b).
aThe reaction was carried out with 3 (0.20 mmol) and 3.0 equiv
of amine (0.60 mmol) in THF (2 mL) at 80 °C (oil bath temperature) in
the presence of [Ir(COD)Cl]2 (1.5 mol %) and (S)-BINAP (3 mol %).
bIsolated yield after silica gel column chromatography. cDetermined by
HPLC with a chiral stationary column (Chiralcel AD-H column for 4a;
Chiralcel OD-H column for 4b, 4c and 4d). dThe reaction solvent is THP
at 100 °C (oil bath temperature).
TABLE 6. Iridium-Catalyzed Asymmetric Ring-Opening of Azabicyc-
lic Alkenes with Primary Aromatic Amine Nucleophilesa
system.10 To our delight, the ring opening of 5 with N-methyl-
aniline afforded the corresponding product 6a not only in a high
yield (92%) but also in a higher enantioselectivity (70% ee)
in the presence of 1.5 mol % of [Ir(COD)Cl]2 and 3 mol % of
(S)-BINAP (Table 5, entry 1). The enantioselectivity is even
better when N-ethylaniline is used as the nucleophile compared
to N-methylaniline though with a slightly lower yield (Table 5,
entry 2). The best results of 88% yield and 86% ee were obtained
when 3-methyl-N-methylaniline was used as the nucleophile
(Table 5, entry 3). However, the reaction with an aliphatic
amine nucleophile, N-phenylpiperazine, did not afford any ring-
opening product (Table 5, entry 4).
Both aniline and 1-aminonaphthalene proved to be effi-
cient nucleophiles in the rhodiun-catalyzed asymmetric ring-
opening reaction of azabicyclic alkenes.10 This encouraged
us to screen primary aromatic amine nucleophiles, as well.
The results summarized in Table 6 show that the nature of
the substituent group on the nitrogen in the azabicyclic
alkene substrate plays a significant role in the enantioselec-
tivity of the products. For example, the ee value of the
products decreased when a Boc group was present in sub-
strate 1, while the presence of a Ts group in substrate 5
enhanced the ee value (Table 6, entries 2 and 3). It was
observed that both the substituted groups on nitrogen of the
azabicyclic alkenes and the electronic effect of nucleophiles
were found to have remarkable impacts on the enantioselec-
tivity of the ring-opening reaction. Nucleophiles with elec-
tron-rich functional groups on the benzene ring such as
2,4-dimethoxyaniline and 4-propylaniline gave moderate
yields with excellent enantioselectivities (up to 97% ee)
(Table 6, entries 4 and 5). On the other hand, when a slightly
aThe reaction was carried out with 1 or 5 (0.20 mmol) and 3.0 equiv of
amine (0.60 mmol) in THF (2.0 mL) at 100 °C (oil bath temperature) in
the presence of [Ir(COD)Cl]2 (1.5 mol %) and (S)-BINAP (3 mol %).
bIsolated yield after silica gel column chromatography. cDetermined by
HPLC with a chiral stationary column (Chiralcel AD-H column for 2l,
6f, 6g, and 6h; Chiralcel OD-H column for 2m and 6e).
electron-withdrawing Br group was present on the aniline
benzene ring, both chemical yield and enantioselectivity
decreased dramatically (Table 6, entry 6).
7294 J. Org. Chem. Vol. 75, No. 21, 2010

Long et al.
JOCArticle
trans-1,2-diamino product 2 is subsequently released and
the iridium complex A is regenerated.
Conclusions
We have developed an asymmetric ring-opening reaction of
N-subsitituted azabicyclic alkenes by a number of primary and
secondary amine nucleophiles in the presence of [Ir(COD)Cl]2/
(S)-BINAP catalyst. It provides an efficient and practical access
to the optically active 1,2-diamine derivatives in moderate to
good yields and enantioselectivities under mild conditions. Our
results further reveal that the nature of the chiral ligand has a
significant impact on this ring-opening reaction. The new
method is significant in terms of the low cost for the ligands
and facile manipulation compared to literature precedents. An
investigation on the biological and pharmaceutical activities of
the products is in progress. Studies on further expansion of the
scope and synthetic utility of this Ir-catalyzed reaction are also
being pursued in our laboratory.
FIGURE 1. ORTEP plot for 2g.
SCHEME 1. Working Hypothesis for the Asymmetric Ring
Opening of N-Boc-Azabenzonorbornadiene 1 with a Secondary
Amine Nucleophile
Experimental Section
General. THF, THP, dioxane, and toluene were distilled from
sodium benzophenone ketyl immediately prior to use. CH3CN
and CH2Cl2 were distilled from calcium hydride. Azabenzonor-
20a
bornadienes 1,20a 3,7 5,16b and [Ir(COD)Cl]2 were prepared
according to the reported procedures. All flasks were flame-
dried under a stream of nitrogen and cooled to room tempera-
ture before use. Solvents and solutions were transferred with
syringes and cannulae using standard inert atmosphere tech-
niques. All 1H and 13C NMR spectra were recorded at 400 and
100 MHz, respectively, using CDCl3 as a solvent. The chemical
shifts of all 1H and 13C NMR spectra are referenced to the
1
residual signal of CDCl3 (δ 7.27 ppm for the H NMR spectra
and δ 77.23 ppm for the 13C NMR spectra). Spectral features are
tabulated in the following order: chemical shift (δ, ppm); multi-
plicity (s-singlet, d-doublet, t-triplet, q-quadruplet, m-complex
multiplet, br-broad); coupling constants (J, Hz); number of pro-
tons. IR spectra were obtained using a KBr pellet or using a
neat film on a NaCl plate. MS spectra were recorded using ESI.
The melting points are uncorrected.
General Procedure (I) for the Asymmetric Ring-Opening Reac-
tions of N-Boc-Azabenzonorbornadiene 1 with Secondary Amine
Nucleophiles. A 5 mL round-bottom flask fitted with a reflux
condenser was flame-dried under a stream of nitrogen and cooled
to room temperature. [Ir(COD)Cl]2 (2.1 mg, 1.5 mol %) and
(S)-BINAP (3.9 mg, 3 mol %) were added, followed by the addi-
tion of anhydrous THF (2.0 mL). After the mixture was stirred
for 10 min at room temperature, N-Boc-azabenzonorbornadiene
1 (50 mg, 0.21 mmol) was added and the temperature of the oil
bath was increased to 80 °C. On the first sign of reflux, nucleo-
phile (3-5 equiv to 1) was added. The reaction was stirred at
80 °C until completion as monitored by thin layer chromatogra-
phy. After the reaction mixture was cooled to room temperature,
the solvent was removed in vacuo and the residue was purified by
column chromatography on silica gel (200-300 mesh) to give the
desired product.
The absolute configuration of ring-opened product 2g was
demonstrated by X-ray crystallography. The single crystal
was obtained by solvent evaporation from a solution con-
sisting of dichloromethane, petroleum ether, and ethyl ace-
tate. Its configuration was assigned as (1R,2R) and confirmed
as 1,2-trans-configuration, as shown in Figure 1. It is obvious
that the reaction favors the formation of trans-1,2-diamino
products.
On the basis of our studies, a working hypothesis is shown in
Scheme 1. First, the chiral dimeric iridium complex Ais formed.
The nitrogen atom and the double bond of N-Boc-azabenzo-
norbornadiene 1 are then reversibly coordinated to the iridium
center of the catalyst to give the intermediate B. In this step,
the intermediate B containing a larger Boc group is less
stable than the counterpart containing a relatively smaller
Ts group. Insertion of the iridium into the C-N bond of
B forms C. Nucleophilic attack of C by an amine nucleo-
phile occurs in an SN20 displacement of the iridium catalyst
with an inversion of configuration. Electron-rich amine
nucleophiles are beneficial for the nucleophilic attack. The
(1R,2R)-[2-(Methylphenylamino)-1,2-dihydronaphthalen-1-yl]-
carbamic acid tert-butyl ester (2a). Following the general proce-
dure (I), 2a was obtained as a white solid (40.2 mg, 56%): Rf =
0.24 on silica gel (ethyl acetate/petroleum ether = 1:20, v/v); mp
160-161 °C; ee was determined to be 84% using HPLC analysis
on a Chiralcel AD column (hexane/2-propanol = 90/10, 0.5 mL/
min, λ = 254 nm); retention times were 11.4min (minor) and 12.5
min (major); [R]20D = -31.8 (c = 1.00, CHCl3); IR (KBr, cm-1
)
3380(s), 3063(w), 2976(w), 2819(w), 1688(s), 1575 (s), 1525(m),
1406(m), 1178(s), 1050(w), 745(m); 1H NMR (400 MHz, CDCl3)
J. Org. Chem. Vol. 75, No. 21, 2010 7295

Long et al.
JOCArticle
δ 7.34 (d, J = 6.4 Hz, 1H), 7.21 (t, J = 7.6 Hz, 3H), 7.10 (d, J =
5.2 Hz, 1H), 6.85 (d, J = 7.6 Hz, 2H), 6.72 (t, J = 6.0 Hz, 1H),
6.61 (d, J = 5.2 Hz, 1H), 5.93 (d, J = 9.6 Hz, 1H), 5.20 (t, J =
10.0 Hz, 1H), 4.79 (d, J = 10.0 Hz, 1H), 4.51 (d, J = 9.2 Hz, 1H),
2.83 (s, 3H), 1.34 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 155.4,
150.1, 135.8, 130.0, 129.1, 128.0, 127.9, 126.6, 125.8, 121.0, 117.1,
114.8, 113.6, 79.5, 60.7, 52.4, 33.0, 28.3; MS (ESI) calcd m/z for
C22H26N2O2 (Mþ) 350.20, found 351.03 (M þ H)þ. Anal. Calcd
for C22H26N2O2: C, 75.40; H, 7.48; N, 7.99. Found: C, 75.69;
H, 7.20; N, 8.23.
(d, J=9.2 Hz, 1H), 2.95 (s, 3H), 1.27 (s, 9H); 13C NMR (100 MHz,
CDCl3) δ 155.2, 154.4, 137.3, 134.3, 132.3, 131.0, 128.5, 128.4,
127.3, 127.1, 126.3, 126.0, 111.2, 79.9, 60.5, 52.3, 33.8, 28.2;
MS (ESI) calcd m/z for C22H25N3O4 (Mþ) 395.18, found 418.24
(M þ Na)þ. Anal. Calcd for C22H25N3O4: C, 66.82; H, 6.37; N,
10.63. Found: C, 66.69; H, 6.20; N, 10.33.
(1R,2R)-{2-[(4-Bromophenyl)methylamino]-1,2-dihydronaphtha-
len-1-yl}carbamic acid tert-butyl ester (2g). Following the general
procedure (I), 2g was obtained as a white solid (25.6 mg, 29%):
Rf = 0.16 on silica gel (ethyl acetate/petroleum ether = 1:25, v/v);
mp 179-181 °C; ee was determined to be 65% using HPLC
analysis on a Chiralcel AD column (hexane/2-propanol = 90/10,
0.5 mL/min, λ = 254 nm); retention times were 10.6 min (minor)
and11.6 min (major)l [R]20D = -78.3 (c = 1.00, CHCl3); IR (KBr,
cm-1) 3374(m), 3043(m), 2963(m), 2920(w), 1682(s), 1520 (s),
1495(s), 1366(m), 1108(m), 783(m); 1H NMR (400 MHz, CDCl3)
δ 7.32-7.21 (m, 4H), 7.11 (d, J = 6.0 Hz 1H), 6.73 (d, J = 8.8 Hz,
2H), 6.61 (dd, J = 12.0 Hz, 7.6 Hz, 1H), 5.87 (dd, J=12.4 Hz,
6.8 Hz, 1H), 5.16 (t, J = 9.6 Hz, 1H), 4.67 (d, J = 9.6 Hz, 1H), 4.52
(d, J= 8.8 Hz, 1H), 2.78 (s, 3H), 1.34 (s, 9H); 13C NMR (100 MHz,
CDCl3) δ 155.2, 149.0, 135.4, 132.6, 131.7, 130.2, 129.0, 128.1,
128.0, 126.8, 125.9, 115.1, 108.8, 79.6, 60.8, 52.2, 33.2, 28.2; MS
(ESI) calcd m/z for C22H25BrN2O2 (Mþ) 428.11, found 429.03
(M þ H)þ. Anal. Calcd for C22H25BrN2O2: C, 61.54; H, 5.87; N,
6.52. Found: C, 61.23; H, 5.62; N, 6.86.
(1R,2R)-[2-(3,4-Dihydro-2H-quinolin-1-yl)-1,2-dihydronaphtha-
len-1-yl]carbamic acid tert-butyl ester (2h). Following the general
procedure (I), 2h was obtained as a white solid (51.4 mg, 65%):
Rf = 0.25 on silica gel (ethyl acetate/petroleum ether = 1:25, v/v);
mp 120-121 °C; ee was determined to be 75% using HPLC
analysis on a Chiralcel OD-H column (hexane/2-propanol = 90/
10, 0.5 mL/min, λ = 254 nm); retentiontimes were9.5 min (major)
and 12.8 min (minor); [R]20D = -56.4 (c = 1.00, CHCl3); IR (KBr,
cm-1) 3372(s), 2927(w), 1688(w), 2898(m), 1600(w), 1499(m),
1365(w), 1301(w), 1250(w), 1169(m), 1048(w), 783(w), 742(w); 1H
NMR (400 MHz, CDCl3) δ7.36(d, J= 6.4 Hz, 1H), 7.24-7.21 (m,
1H), 7.10 (d, J = 6.8 Hz, 1H), 7.02 (t, J = 7.8 Hz, 1H), 6.96 (d, J =
7.2 Hz, 1H), 6.78 (d, J = 8.0 Hz, 1H), 6.63-6.56 (m, 2H), 5.91 (d,
J = 9.6 Hz, 1H), 5.28 (t, J = 9.8 Hz, 1H), 4.80 (d, J = 9.6 Hz, 1H),
4.62 (s, 1H), 3.22 (s, 2H), 2.72 (t, J = 6.4 Hz, 2H), 1.94-1.80 (m,
2H), 1.35 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 155.5, 145.4,
136.0, 132.8, 130.1, 129.5, 128.0, 127.8, 126.9, 126.6, 126.3, 125.9,
123.6, 116.1, 111.2, 79.5, 58.3, 51.7, 43.5, 28.3, 28.2, 22.3; MS (ESI)
calcd m/z for C24H28N2O2 (Mþ) 376.22, found 399.33 (M þ Na)þ;
Anal. Calcd for C24H28N2O2: C, 76.56; H, 7.50; N, 7.44. Found: C,
76.31; H, 7.18; N, 7.63.
(1R,2R)-[2-(3,4-Dihydro-1H-isoquinolin-2-yl)-1,2-dihydro-
naphthalen-1-yl]carbamic acid tert-butyl ester (2i). Following the
general procedure (I), 2i was obtained as colorless oil (22.9 mg,
29%): Rf=0.37 on silica gel (ethyl acetate/petroleum ether=1:6,
v/v); ee was determined to be 64% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol = 90/10, 0.5 mL/
min, λ = 254 nm); retention times were 10.2 min (major) and
12.5 min (minor); [R]20D=-84.5 (c = 1.00, CHCl3); IR (KBr,
cm-1) 3346(m), 3065(m), 2976 (m), 2926(m), 2803(w), 1707(s),
1496(s), 1453(m), 1365(m), 1248(m), 1167(s), 1093(w), 1044(w),
1022(w), 934(w), 780(w), 741(m); 1H NMR (400 MHz, CDCl3) δ
7.34 (d, J = 7.2 Hz, 1H), 7.28-7.21 (m, 1H), 7.12 (d, J = 6.8 Hz,
1H), 7.05 (d, J = 7.2 Hz, 3H), 6.94 (d, J = 6.8 Hz, 1H), 6.68
(d, J = 9.6 Hz,1H), 6.30 (dd, J = 12.8 Hz, 5.2 Hz, 1H), 5.10 (br s,
1H), 4.65 (dd, J = 10.0 Hz, 2.0 Hz, 1H), 3.90 (d, J=14.8 Hz, 1H),
3.73 (d, J = 15.2 Hz, 1H), 3.60 (t, J=4.8 Hz, 1H), 2.87-2.80
(m, 4H), 1.43 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 155.2,
135.3, 135.2, 134.5, 132.4, 129.7, 128.7, 128.3, 128.1, 127.7, 126.8,
126.6, 125.8, 125.8, 125.4, 79.5, 63.5, 51.4, 48.5, 46.6, 29.9, 28.4;
MS (ESI) calcd m/z for C24H28N2O2 (Mþ) 376.22, found 399.03
(M þ Na)þ. Anal. Calcd for C24H28N2O2: C, 76.56; H, 7.50; N,
7.44. Found: C, 76.69; H, 7.20; N, 7.63.
(1R,2R)- [2-(Ethylphenylamino)-1,2-dihydronaphthalen-1-yl]-
carbamic acid tert-butyl ester (2b). Following the general proce-
dure (I), 2b was obtained as a white solid (34.4 mg, 45%): Rf =
0.19 on silica gel (ethyl acetate/petroleum ether = 1:25, v/v); mp
128-129 °C; ee was determined to be 76% using HPLC analysis
on a Chiralcel AD-H column (hexane/2-propanol = 95/5, 0.5
mL/min, λ=254 nm); retention times were 14.4 min (minor)
and 21.3 min (major); [R]20 = -56.5 (c = 1.00, CHCl3); IR
D
(KBr, cm-1) 3355(w), 3248(w), 2975 (w), 2927(w), 1696(s),
1596(s), 1505(s), 1365(m), 1249(w), 1116(s), 987(m), 781(w),
1
745(m), 642(w); H NMR (400 MHz, CDCl3) δ 7.35 (d, J =
6.8 Hz, 1H), 7.26 (t, J = 8. 0 Hz, 3H), 7.13 (d, J = 6.4 Hz, 1H),
6.91 (d, J = 8.4 Hz, 2H), 6.75 (t, J = 7.2 Hz, 1H), 6.65 (dd, J =
11.6 Hz, 8.0 Hz, 1H), 6.00 (dd, J = 12.0 Hz, 6.8 Hz, 1H), 5.20 (t,
J = 9.2 Hz, 1H), 4.74 (d, J = 8.4 Hz, 1H), 4.63 (d, J = 8.8 Hz,
1H), 3.32 (q, 2H), 1.43 (s, 9H), 1.11 (t, J = 6.8 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 155.2, 148.3, 135.5, 132.6, 130.2,
129.2, 128.8, 128.1, 128.0, 126.8, 125.9, 121.7, 116.9, 114.7, 79.6,
61.0, 33.2, 28.3, 13.9; MS (ESI) calcd m/z for C23H28N2O2 (Mþ)
364.22, found 364.97. Anal. Calcd for C23H28N2O2: C, 75.79; H,
7.74; N, 7.69. Found: C, 75.69; H, 7.71; N, 7.92.
(1R,2R)-[2-(Allylphenylamino)-1,2-dihydronaphthalen-1-yl]-
carbamic acid tert-butyl ester (2c). Following the general pro-
cedure (I), 2c was obtained as a white solid (22.2 mg, 28%):
Rf = 0.19 on silica gel (ethyl acetate/petroleum ether = 1:25, v/v);
mp 111-113 °C; ee was determined to be 69% using HPLC
analysis on a Chiralcel AD column (hexane/2-propanol = 95/5,
0.5 mL/min, λ = 254 nm); retention times were 14.7 min (minor)
and 18.9 min (major); [R]20D =-56.1 (c=1.00, CHCl3);IR(KBr,
cm-1) 3356(w), 2975(m), 2927(m), 1709(s), 1597(m), 1503(m),
1456(w), 1367(s), 1332(s), 1252(s), 1168(s), 1074(m), 858(w),
1
782(w), 747(m), 694(w), 542(w); H NMR (400 MHz, CDCl3)
δ 7.31 (d, J = 7.2 Hz, 1H), 7.27-7.18 (m, 3H), 7.11 (d, J = 6.4 Hz,
1H), 6.88 (d, J = 7.6 Hz, 2H), 6.72 (t, J = 7.0 Hz, 1H), 6.61 (d, J =
9.6 Hz, 1H), 5.98 (d, J = 9.2 Hz, 1H), 5.78-5.73 (m, 1H), 5.16 (d,
J = 8.4 Hz, 1H), 5.12 (d, J = 6.0 Hz, 1H), 5.07 (d, J = 10.0 Hz,
1H), 4.81 (d, J = 6.4 Hz, 1H), 4.58 (d, J = 6.8 Hz, 1H), 3.84 (s,
2H), 1.37 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 155.2, 148.4,
135.7, 135.4, 132.5, 130.0, 129.0, 128.7, 128.1, 128.0, 126.7, 124.8,
117.1, 115.7, 114.2, 79.5, 59.7, 52.3, 29.7, 28.3; MS (ESI) calcd m/z
for C24H28N2O2 (Mþ) 376.22, found 399.24 (M þ Na)þ. Anal.
Calcd for C24H28N2O2: C, 76.56; H, 7.50; N, 7.44. Found: C, 76.69;
H, 7.80; N, 7.23.
(1R,2R)-{2-[Methyl-(4-nitrophenyl)amino]-1,2-dihydronaphtha-
len-1-yl}carbamic acid tert-butyl ester (2f). Following the general
procedure (I), 2f was obtained as a yellow solid (20.7 mg, 25%):
Rf = 0.39 on silica gel (ethyl acetate/petroleum ether = 1:4, v/v);
mp 151-152 °C; ee was determined to be 61% using HPLC
analysis on a Chiralcel AD-H column (hexane/2-propanol = 90/
10, 0.5 mL/min, λ = 254 nm); retention times were 30.4 min
(minor) and36.5min(major); [R]20D =-124.3 (c = 1.00, CHCl3);
IR (KBr, cm-1) 3353(m), 3065(w), 2976(w), 2920(w), 1686(s),
1595(s), 1510(s), 1392(m), 1366(w), 1316(s), 1166(m), 1104(m),
1008(w), 938(w), 825(w), 784(m), 751(m), 616(w), 562(m); 1H
NMR (400 MHz, CDCl3) δ 8.01 (d, J = 7.6 Hz, 2H), 7.34 (d,
J = 7.2 Hz, 1H), 7.29-7.22 (m, 1H), 7.13 (d, J = 6.8 Hz, 1H),
6.81 (d, J = 7.6 Hz, 2H), 6.67 (d, J = 9.6 Hz, 1H), 5.85 (d, J= 10.0
Hz, 1H), 5.17 (t, J = 9.6 Hz, 1H), 4.97 (d, J = 9.2 Hz, 1H), 4.62
7296 J. Org. Chem. Vol. 75, No. 21, 2010

Long et al.
JOCArticle
(1R,2R)-(2-Piperidin-1-yl-1,2-dihydronaphthalen-1-yl)carbamic
acid tert-butyl ester (2j). Following the general procedure (I), 2j
was obtained as a white solid (8.3 mg, 12%): Rf = 0.31 on silica
gel (ethyl acetate/petroleum ether = 1:4, v/v); mp 115-118 °C; ee
was determined to be 19% using HPLC analysis on a Chiralcel
OD-H column (hexane/2-propanol = 90/10, 0.5 mL/min, λ =
254 nm); retention times were 7.4 min (major) and 7.7 min
(m, 2H), 7.16 (d, J = 7.2 Hz, 1H), 7.04 (d, J = 7.6 Hz, 2H), 6.67
(d, J = 7.6 Hz, 2H), 6.57 (d, J = 9.2 Hz, 1H), 6.11 (dd, J = 4.4 Hz,
5.2 Hz, 1H), 5.08 (t, J = 7.2 Hz, 1H), 4.87 (d, J = 8.8 Hz, 1H), 4.27
(s, 1H), 3.75 (s, 1H), 2.29 (s, 3H), 1.51 (s, 9H);13C NMR (100 MHz,
CDCl3) δ155.9, 145.8, 133.6, 132.3, 132.1, 128.9, 128.6, 128.4, 128.1,
127.8, 127.0, 114.8, 109.1, 80.0, 53.4, 52.1, 28.4; MS (ESI) calcd m/z
for C22H26N2O2 (Mþ) 350.45, found 373.27 (M þ Na)þ. Anal.
Calcd for C22H26N2O2: C, 75.40; H, 7.48; N, 7.99. Found: C, 75.09;
H, 7.88; N, 7.47.
General Procedure (II) for the Asymmetric Ring-Opening
Reactions of N-Boc-6,7-dimethoxy Azabenzonorbornadiene 3
with Secondary Amine Nucleophiles. A 5 mL round-bottom flask
fitted with a reflux condenser was flame-dried under a stream
of nitrogen and cooled to room temperature. [Ir(COD)Cl]2
(2.0 mg, 1.5 mol %) and (S)-BINAP (3.7 mg, 3 mol %) were
simultaneously added and followed by the addition of anhy-
drous THF (2 mL). After the reaction mixture was stirred for
10 min at room temperature, N-Boc-6,7-dimethoxy azabenzo-
norbornadiene 3 (60 mg, 0.20 mmol) was added and the
temperature of the oil bath was increased to 80 °C. On the first
sign of reflux, nucleophile (3-5 equiv to 3) was added. The
reaction was stirred at 80 °C until completion as monitored by
thin layer chromatography. After the reaction mixture was
cooled to room temperature, the solvent was removed in vacuo
and the residue was purified by column chromatography on
silica gel (200-300 mesh) to give the desired product.
(minor); [R]20 = -44.9 (c = 1.00, CHCl3); IR (KBr, cm-1
)
D
3353(m), 2930 (s), 2854(w), 1714(s), 1494 (s), 1366(w), 1305(w),
1248(m), 1172(s), 745(m), 1119(w), 1045(w), 861(w), 779(w),
1
745(w), 613(w); H NMR (400 MHz, CDCl3) δ 7.18-7.13 (m,
2H), 7.02-6.99 (m, 1H), 6.56 (dd, J = 10.8 Hz, 8.8 Hz, 1H), 5.92
(dd, J = 14.4 Hz, 4.8 Hz, 1H), 4.96 (br s, 1H), 4.53 (br s, 1H),
3.32-3.29 (m, 1H), 2.57-2.49 (m, 2H), 2.39-2.34 (m, 2H),1.45-
1.41 (m, 4H), 1.38 (s, 9H), 1.33-1.27 (m, 2H); 13C NMR (100
MHz, CDCl3) δ 155.1, 135.6, 132.4, 129.2, 128.1, 127.9, 127.7,
126.6, 126.1, 64.7, 49.9, 48.0, 29.7, 28.4, 26.4, 24.5; MS (ESI) calcd
m/z for C20H28N2O2 (Mþ) 328.22, found 329.24 (M þ H)þ; Anal.
Calcd for C20H28N2O2: C, 73.14; H, 8.59; N, 8.53. Found: C,
73.49; H, 8.30; N, 8.23.
(1R,2R)-[2-(4-Phenylpiperazin-1-yl)-1,2-dihydronaphthalen-1-yl]-
carbamic acid tert-butyl ester (2k). Following the general procedure
(I), 2k was obtained as a white solid (35.2 mg, 40%): Rf = 0.36 on
silica gel (ethyl acetate/petroleum ether = 1:4, v/v); mp 164-
165 °C; ee was determined to be 37% using HPLC analysis on a
Chiralcel OD-H column (hexane/2-propanol = 90/10, 0.5 mL/min,
λ = 254 nm); retention times were 13.7 min (major) and 15.0 min
(1R,2R)-[6,7-Dimethoxy-2-(methylphenylamino)-1,2-dihydro-
naphthalen-1-yl]carbamic acid tert-butyl ester (4a). Following
the general procedure (II), 4a was obtained as a white solid
(45.1 mg, 55%): Rf = 0.37 on silica gel (ethyl acetate/petroleum
ether = 1:4, v/v); mp 137-140 °C; ee was determined to be 83%
using HPLC analysis on a Chiralcel AD column (hexane/
2-propanol = 98/2, 1.0 mL/min, λ = 254 nm); retention times
(minor); [R]20 = -80.2 (c = 1.00, CHCl3); IR (KBr, cm-1
)
D
3333(s), 3036(w), 2963(m), 2824(m), 1679(s), 1601(m), 1497(m),
1368(m), 1231(m), 1173(s), 758(m); 1H NMR (400 MHz, CDCl3)
δ 7.35 (d, J = 7.6 Hz, 1H), 7.27-7.20 (m, 3H), 7.11-7.09 (m, 1H),
6.86 (d, J = 8.0 Hz, 2H), 6.82 (t, J = 7.2 Hz, 1H), 6.67 (d, J = 10.0
Hz, 1H), 6.01 (dd, J = 7.2 Hz, 4.8 Hz, 1H), 5.06 (br s, 1H), 4.62 (br
d, J = 6.8 Hz, 1H), 3.48 (t, J = 4.4 Hz, 1H), 3.11 (t, J = 4.8 Hz,
4H), 2.83-2.77 (m, 2H), 2.71-2.68 (m, 2H), 1.44 (s, 9H); 13C
NMR (100 MHz, CDCl3) δ 155.4, 151.6, 135.5, 132.6, 129.9, 129.2,
128.5, 128.3, 128.0, 126.9, 125.6, 119.7, 116.3, 79.7, 64.1, 49.8, 48.9,
29.7, 28.4; MS (ESI) calcd m/z for C25H31N3O2 (Mþ) 405.24, found
406.12 (M þ H)þ. Anal. Calcd for C25H31N3O2: C, 74.04; H, 7.70;
N, 10.36. Found: C, 74.09; H, 8.00; N, 10.47.
were 25.2 min (minor) and 28.1 min (major); [R]20 = -49.3
D
(c = 1.00, CHCl3); IR (KBr, cm-1) 3369(m), 3069(w), 2971(m),
2972(m), 1717(s), 1595(m), 1506(s), 1385(m), 1278(m), 1161(m),
1
1100(m), 944(m), 908(m), 866(m), 742(m), 575(m); H NMR
(400 MHz, CDCl3) δ 7.26-7.21 (m, 1H), 6.89 (d, J = 8.8 Hz,
3H), 6.73 (t, J = 7.2 Hz, 1H), 6.66 (s, 1H), 6.57 (dd, J = 1.6 Hz,
1.2 Hz, 1H), 5.84 (dd, J = 13.6 Hz, 6.0 Hz, 1H), 5.07 (t, J =
8.8 Hz, 1H), 4.71 (d, J = 7.6 Hz, 1H), 4.55 (d, J = 8.4 Hz, 1H),
3.88 (s, 3H), 3.87 (s, 3H), 2.76 (s, 3H), 1.37 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ 155.3, 149.9, 148.6, 148.4, 129.7, 129.1,
128.3, 126.6, 125.4, 124.1, 117.1, 113.7, 110.3, 79.5, 60.2, 56.0,
56.0, 52.0, 33.0, 28.2; MS (ESI) calcd m/z for C24H30N2O4 (Mþ)
410.22, found 433.27 (M þ Na)þ. Anal. Calcd for C24H30N2O4:
C, 70.22; H, 7.37; N, 6.82. Found: C, 70.60; H, 7.60; N, 6.79.
(1R,2R)-[2-(Ethylphenylamino)-6,7-dimethoxy-1,2-dihydro-
naphthalen-1-yl]carbamic acid tert-butyl ester (4b). Following the
general procedure (II), 4b was obtained as a white solid (38.2 mg,
45%): Rf = 0.29 on silica gel (ethyl acetate/petroleum ether = 1:4,
v/v); mp 130-135 °C; ee was determined to be 53% using HPLC
analysis on a Chiralcel AD column (hexane/2-propanol = 98/2,
1.0 mL/min, λ = 254 nm); retention times were 26.2 min (major)
and 28.4 min (minor); [R]20D =-59.7 (c= 1.00, CHCl3);IR(KBr,
cm-1) 3347(w), 3046(w), 2971(w), 29279(w), 1709(s), 1062(m),
1502(s), 1371(w), 1256(s), 1159(s), 1085(m), 988(m), 840(m),
746(m), 688(m), 515(m); 1H NMR (400 MHz, CDCl3) δ 7.24 (t,
J = 7.6 Hz, 1H), 6.89 (d, J = 7.2 Hz, 2H), 6.86 (s, 1H), 6.72 (t, J =
6.8 Hz, 1H), 6.66 (s, 1H), 6.57 (d, J = 9.6 Hz, 1H), 5.85 (dd, J =
12.8 Hz, 6.0 Hz, 1H), 5.01 (t, J = 8.2 Hz, 1H), 4.60 (br s, 1H), 3.89
(s, 3H), 3.86 (s, 3H), 3.21 (q, 2H), 1.41 (s, 9H), 1.03 (t, J = 6.8 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 155.3, 149.5, 148.6, 148.5,
130.1, 129.2, 128.3, 126.2, 125.2, 124.1, 116.8, 114.0, 110.8, 80.5,
59.5, 56.0, 56.0, 51.9, 39.9, 28.3, 14.1; MS (ESI) calcd m/z for
C25H32N2O4 (Mþ) 424.24, found 447.26 (M þ Na)þ. Anal. Calcd
for C25H32N2O4: C, 70.73; H, 7.60; N, 6.60. Found: C, 70.93; H,
7.50; N, 6.43.
(1R,2R)-[2-(4-Bromophenylamino)-1,2-dihydronaphthalen-1-yl]-
carbamic acid tert-butyl ester (2l). Following the general procedure
(I), 2l was obtained as a white solid (65.6 mg, 79%): Rf = 0.31 on
silica gel (ethyl acetate/petroleum ether = 1:8, v/v); mp 93-95 °C;
ee was determined to be 83% using HPLC analysis on a Chiralcel
AD-H column (hexane/2-propanol = 90/10, 0.5 mL/min, λ = 254
nm); retention times were 16.6 min (major) and 31.2 min (minor);
[R]20 = -132.1 (c = 1.00, CHCl3); IR (KBr, cm-1) 3398(w),
D
2976(w), 1702(s), 1593(m), 1496(s), 1453(w), 1367(w), 1319(w),
1248(m), 1168(s), 814(m), 782(m); 1H NMR (400 MHz, CDCl3)
δ 7.29-7.19 (m, 4H), 7.12 (d, J = 7.2 Hz, 1H), 6.58 (q, J = 7.2 Hz,
3H), 6.03 (q, J= 5.2 Hz, 1H), 4.97 (t, J = 6.8 Hz, 1H), 4.68 (d, J =
8.4 Hz, 1H), 4.21 (s 1H), 3.85 (s, 1H), 1.44 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 155.9, 145.8, 133.6, 132.3, 132.1, 128.9, 128.6,
128.4, 128.1, 127.8, 127.0, 114,8, 109.1, 80.0, 53.4, 52.1, 28.4; MS
(ESI) calcd m/z for C21H23BrN2O2 (Mþ) 415.32, found 416.94
(M þ H)þ. Anal. Calcd for C21H23BrN2O2: C, 60.73; H, 5.58; N,
6.74. Found: C, 60.42; H, 5.72; N, 6.32.
(1R,2R)-[2-(p-Toluidino)-1,2-dihydronaphthalen-1-yl]carbamic
acid tert-butyl ester(2m). Following the general procedure (I), 2m
was obtained as a white solid (40.6 mg, 58%): Rf = 0.38 on silica
gel (ethyl acetate/petroleum ether = 1:8, v/v); mp 80-82 °C; ee
was determined to be 86% using HPLC analysis on a Chiralcel
OD column (hexane/2-propanol=90/10, 0.5 mL/min, λ=254 nm);
retention times were 10.1 min (major) and 12.3 min (minor);
[R]20D = -24.5 (c = 1.00, CHCl3); IR (KBr, cm-1) 3386(w),
2976(w), 1706(s), 1616(w), 1519(s), 1366(w), 1299(w), 1245(w),
1166(s), 808(m), 782(m); 1H NMR (400 MHz, CDCl3) δ 7.35-7.23
J. Org. Chem. Vol. 75, No. 21, 2010 7297

Long et al.
JOCArticle
(1R,2R)-[2-(3,4-Dihydro-2H-quinolin-1-yl)-6,7-dimethoxy-1,2-
dihydronaphthalen-1-yl]carbamic acid tert-butyl ester (4c). Fol-
lowingthe general procedure (II), 4c was obtained as a white solid
(50.6 mg, 58%): Rf = 0.3 on silica gel (ethyl acetate/petroleum
ether = 1:4, v/v); mp 140-145 °C; ee was determined to be 44%
using HPLC analysis on a Chiralcel OD-H column (hexane/
2-propanol = 90/10, 0.5 mL/min, λ = 254 nm); retention times
were 18.3 min (major) and 25.0min (minor);[R]20D = -72.2 (c =
1.00, CHCl3); IR (KBr, cm-1) 3363(m), 2971(m), 2932(m),
2833(w), 1710(s), 1600(m), 1504(s), 1455(m), 1390(w), 1366(w),
1274(m), 1227(w), 1160(m), 1108(w), 1015(w), 867(w), 742(m),
604(w); 1H NMR (400 MHz, CDCl3) δ 6.96 (d, J = 7.2 Hz, 1H),
6.87 (t, J =8.6Hz, 2H), 6.66(s, 1H), 6.61-6.55(m, 2H), 5.82(dd,
J = 12.8Hz, 6.0 Hz, 1H), 5.12(q, 1H), 4.72(dd, J = 36.0 Hz, 21.2
Hz, 2H), 3.88 (s, 3H), 3.87 (s, 3H),3.22-3.17 (m, 1H), 3.07 (s,
1323(s), 1156(s), 1093(m), 1030(w), 919(w), 811(w), 1030(w),
747(m), 663(m), 546(m); H NMR (400 MHz, CDCl3) δ 7.61
1
(d, J = 8.0 Hz, 2H), 7.25-7.16 (m, 5H), 7.11 (d, J = 7.6 Hz,
2H), 6.93 (d, J = 7.6 Hz, 1H), 6.75 (t, J = 7.8 Hz, 3H), 6.69
(dd, J = 10.8 Hz, 8.4 Hz, 1H), 5.85 (dd, J = 14.4 Hz, 4.8 Hz,
1H), 4.78 (d, J = 8.0 Hz, 1H), 4.70-4.67 (m, 1H), 4.57 (dd,
J = 13.2 Hz, 2.0 Hz, 1H), 2.40 (s, 3H), 2.34 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 148.9, 143.3, 137.6, 133.8, 132.2, 130.4,
129.6, 129.1, 128.7, 128.4, 127.6, 127.2, 127.0, 126.1, 117.6,
113.9, 59.1, 54.6, 32.4, 21.6; MS (ESI) calcd m/z for C24H24
-
N2O2S (Mþ) 404.16, found 427.30 (M þ Na)þ. Anal. Calcd for
C24H24N2O2S: C, 71.26; H, 5.98; N, 6.93. Found: C, 71.29; H,
6.28; N, 6.78.
(1R,2R)-N-[2-(Ethylphenylamino)-1,2-dihydronaphthalen-1-yl]-
4-methylbenzenesulfonamide (6b). Following the general proce-
dure (III), 6b was obtained as a white solid (66.8 mg, 79%): Rf =
0.35 on silica gel (ethyl acetate/petroleum ether = 1:4, v/v); mp
134-135 °C; ee was determined to be 80% using HPLC anal-
ysis on a Chiralcel OD-H column (hexane/2-propanol=90/10,
0.5 mL/min, λ = 254 nm); retention times were 10.6 min (major)
1H), 2.72 (t, J = 6.4 Hz, 2H), 1.87-1.78 (m, 2H), 1.38 (s, 9H); 13
C
NMR (100 MHz, CDCl3) δ 155.4, 148.5, 148.4, 145.2, 129.8,
129.5, 128.5, 127.0, 126.2, 125.5, 123.7, 116.1, 111.3, 110.3, 110.2,
79.5, 57.9, 56.0, 56.0, 51.4, 43.3, 28.3, 28.2, 22.4; MS (ESI) calcd
m/z for C26H32N2O4 (Mþ) 436.24, found 459.35 (M þ Na)þ.
Anal. Calcd for C26H32N2O4: C, 71.53; H, 7.39; N, 6.42. Found:
C, 71.22; H, 7.60; N, 6.49.
and 13.1 min (minor); [R]20 = -119.8 (c = 1.00, CHCl3); IR
D
(KBr, cm-1) 3268(m), 3053(w), 2956(w), 2924(m), 1595(s), 1501(s),
1323(m), 1262(m), 1156(s), 1092(w), 914(m), 813(m), 748(m),
663(m), 564(m); 1H NMR (400 MHz, CDCl3) δ 7.55 (d, J = 8.4
Hz, 2H), 7.16-7.09 (m, 5H), 7.04 (dd, J = 8.4 Hz, 6.4 Hz, 1H), 6.96
(ddd, J = 16.4 Hz, 14.0 Hz, 1.2 Hz, 1H), 6.70 (d, J = 8.4 Hz, 2H),
6.66 (t, J= 3.6 Hz, 2H), 6.63 (d, J = 1.2 Hz, 1H), 5.88 (dd, J =14.8
Hz, 4.4 Hz, 1H), 4.73 (d, J = 8.0 Hz, 1H), 4.51-4.49 (m, 1H), 4.46
(dd, J = 11.6 Hz, 4.4 Hz, 1H), 2.85 (q, 2H), 2.33 (s, 3H), 0.71 (t, J =
7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 146.8, 143.3, 137.7,
133.5, 132.2, 130.4, 129.6, 129.2, 128.8, 128.4, 128.2, 127.3, 127.1,
126.1, 116.9, 113.8, 58.2, 54.1, 39.8, 21.6, 14.1; MS (ESI) m/z calcd
for C25H26N2O2S (Mþ) 418.17, found 441.23 (M þ Na)þ. Anal.
Calcd for C25H26N2O2S: C, 71.74; H, 6.26; N, 6.69. Found: C, 71.51;
H, 6.48; N, 6.91.
(1R,2R)-[6,7-Dimethoxy-2-(4-phenylpiperazin-1-yl)-1,2-dihy-
dronaphthalen-1-yl]carbamic acid tert-butyl ester (4d). Following
the general procedure (II), 4d was obtained as a white solid
(29.8 mg, 32%): Rf = 0.29 on silica gel (ethyl acetate/petroleum
ether = 1:3, v/v); mp 184-185 °C; ee was determined to be 56%
using HPLC analysis on a Chiralcel OD-H column (hexane/
2-propanol = 90/10, 0.5 mL/min, λ = 254 nm); retention times
were 19.0 min (minor) and 25.9 min (major); [R]20 = -37.1
D
(c = 1.00, CHCl3); IR (KBr, cm-1) 3347(m), 2928(m), 2826(w),
1702(s), 1599(s), 1501(s), 1446(m), 1309(w), 1232(s), 1164(m),
1
993(m), 758(m), 593(m), 605(w); H NMR (400 MHz, CDCl3)
δ 7.24-7.18 (m, 2H), 6.84(d, J = 8.4Hz, 3H), 6.80(t, J = 7.4 Hz,
1H), 6.62 (s, 1H), 6.58 (d, J = 10.0 Hz, 1H), 5.85 (dd, J = 14.4
Hz, 4.4 Hz, 1H), 4.94 (br s, 1H), 4.58 (br s, 1H), 3.87 (s, 3H), 3.86
(s, 3H), 3.41 (s, 1 H), 3.08 (d, J = 4.4 Hz, 4H), 2.79 (t, J = 10.8
Hz, 2H), 2.62 (t, J = 10.4 Hz, 2H), 1.43 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 155.1, 151.4, 148.8, 148.6, 129.3, 129.0, 127.6,
125.1, 122.9, 119.5, 116.0, 111.4, 110.0, 79.5, 63.5, 56.1, 56.0, 49.6,
48.6, 47.9, 28.4; MS (ESI) calcd m/z for C27H35N3O4 (Mþ)
465.26, found 466.18 (M þ H)þ. Anal. Calcd for C27H35N3O4:
C, 69.65; H, 7.58; N, 9.03. Found: C, 69.99; H, 7.22; N, 9.40.
General Procedure (III) for the Asymmetric Ring-Opening
Reactions of N-Ts-Azabenzonorbornadiene 5 with Secondary
Amine Nucleophiles. A 5 mL round-bottom flask fitted with a
reflux condenser was flame-dried under a stream of nitrogen and
cooled to room temperature. [Ir(COD)Cl]2 (2.0 mg, 1.5 mol %)
and (S)-BINAP (3.7 mg, 3 mol %) were simultaneously added
and followed by the addition of anhydrous THF (2 mL). After
the reaction mixture was stirred for 10 min at room temperature,
N-Ts-azabenzonorbornadiene 5 (60 mg, 0.20 mmol) was added
and the temperature of the oil bath was increased to 100 °C. On
the first sign of reflux, nucleophile (3-5 equiv to 5) was added.
The reaction was stirred at 100 °C until completion as monitored
by thin layer chromatography. After the reaction mixture was
cooled to room temperature, the solvent was removed in vacuo
and the residue was purified by column chromatography on
silica gel (200-300 mesh) to give the desired product.
(1R,2R)-N-[2-(Methyl-m-tolylamino)-1,2-dihydronaphthalen-
1-yl]-4-methylbenzenesulfonamide (6c). Following the general
procedure (III), 6c was obtained as a white solid (73.6 mg,
88%): Rf = 0.20 on silica gel (ethyl acetate/petroleum ether =
1:6, v/v); mp 120-124 °C; ee was determined to be 86%
using HPLC analysis on a Chiralcel AD column (hexane/
2-propanol = 90/10, 1.0 mL/min, λ = 254 nm); retention times
were 12.2 min (minor) and 14.0 min (major)l [R]20 = -93.4
D
(c = 1.00, CHCl3); IR (KBr, cm-1) 3271(m), 3028(w), 2917(w),
1598(s), 1494(s), 1450(m), 1323(s), 1302(s), 1155(s), 1092(m),
1081(w), 949(w), 782(m), 664(s), 616(w), 564(s); 1H NMR (400
MHz, CDCl3) δ 7.54 (d, J = 8.0 Hz, 2H), 7.16 (t, J = 7.4 Hz,
1H), 7.11 (d, J = 8.2 Hz, 2H), 7.02 (t, J = 7.8 Hz, 3H), 6.83 (d,
J = 6.8 Hz, 1H), 6.60 (d, J = 9.6 Hz, 1H), 6.56 (s, 1H), 6.52 (d,
J = 7.6 Hz, 1H), 6.50 (dd, J = 10.8 Hz, 6.0 Hz, 1H), 5.79 (dd,
J = 14.4 Hz, 4.8 Hz, 1H), 4.64-4.61 (m, 1H), 4.58-4.49 (m,
2H), 2.37 (s, 3H), 2.26 (s, 3H), 2.25 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 149.0, 143.2, 138.9, 137.6, 133.8, 132.3, 130.3, 129.5,
129.0, 128.7, 128.3, 127.7, 127.2, 127.0, 126.2, 118.6, 114.7,
111.1, 59.0, 54.6, 32.4, 21.8, 21.5; MS (ESI) calcd m/z for
C25H26N2O2S (Mþ) 418.17, found 441.20 (M þ Na)þ. Anal.
Calcd for C25H26N2O2S: C, 71.74; H, 6.26; N, 6.69. Found: C,
71.50; H, 6.50; N, 6.91.
(1R,2R)-N-[2-(p-Toluidino)-1,2-dihydronaphthalen-1-yl]-4-methyl-
benzenesulfonamide (6e). Following the general procedure
(III), 6e was obtained as a white solid (77.6 mg, 96%): Rf =
0.25 on silica gel (ethyl acetate/petroleum ether = 1:4, v/v); mp
56-58 °C; ee was determined to be 94% using HPLC analysis
on a Chiralcel OD-H column (hexane/2-propanol = 90/10,
0.5 mL/min, λ = 254 nm); retention times were 27.3 min (major)
(1R,2R)-4-Methyl-N-[2-(methylphenylamino)-1,2-dihydro-
naphthalen-1-yl]-benzenesulfonamide (6a). Following the general
procedure (III), 6a was obtained as a white solid (74.3 mg, 92%):
Rf = 0.36 on silica gel (ethyl acetate/petroleum ether = 1:4, v/v);
mp 130-132 °C; ee was determined to be 70% using HPLC analysis
on a Chiralcel OD-H column (hexane/2-propanol = 90/10, 0.5 mL/
min, λ = 254 nm); retention times were 23.0 min (minor) and
29.6 min (major); [R]20D = -102.6 (c = 1.00, CHCl3); IR (KBr,
cm-1) 3277(m), 3063(w), 2925(w), 1596(s), 1503(s), 1451(w),
and 34.9 min (minor); [R]20 = -91.1 (c = 1.00, CHCl3); IR
D
(KBr, cm-1) 3277(w), 3026(w), 2920(w), 1615(m), 1518(s),
1407(w), 1328(s), 1158(s), 1093(m), 1041(w), 922(w), 811(m),
7298 J. Org. Chem. Vol. 75, No. 21, 2010

Long et al.
JOCArticle
762(w), 664(m), 565(m), 547(m); 1H NMR (400 MHz, CDCl3)
δ 7.71 (dd, J = 2.0 Hz, 6.0 Hz, 2H), 7.26 (d, J = 8.0 Hz, 2H),
7.21 (t, J = 6.8 Hz, 1H), 7.08 (d, J = 8.0 Hz, 1H), 7.01 (d, J =
7.2 Hz, 1H), 6.96 (d, J = 8.4 Hz, 2H), 6.60 (d, J = 7.6 Hz, 1H),
6.55 (d, J = 9.6 Hz, 1H), 6.48 (dd, J = 2.0 Hz, 6.4 Hz, 2H),
6.05-6.01 (m, 1H), 5.13 (d, J = 7.6 Hz, 1H), 4.46-4.44 (m,
1H), 4.28 (s, 1H), 3.26 (s, 1H), 2.44 (s, 3H), 2.25 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 140.9, 134.9, 129.5, 129.3, 127.3,
127.2, 126.6, 126.4, 125.7, 124.8, 124.6, 124.4, 124.2, 110.9,
50.9, 49.8, 19.0, 17.9; MS (ESI) calcd m/z for C24H24N2O2S
(Mþ) 404.52, found 427.38 (M þ Na)þ. Anal. Calcd for
C24H24N2O2S: C, 71.26; H, 5.98; N, 6.93. Found: C, 71.65;
H, 6.35; N, 6.60.
1043(m), 923(w), 796(m), 665(m), 567(m), 548(m); 1H NMR
(400 MHz, CDCl3) δ 7.73 (d, J = 8.4 Hz, 2H), 7.28 (d, J =
8.0 Hz, 2H), 7.21 (t, J = 7.2 Hz, 1H), 7.09 (d, J = 7.2 Hz, 1H),
7.02-6.96 (m, 3H), 6.57 (t, J = 6.8 Hz, 2H), 6.51 (d, J = 8.0 Hz,
2H), 6.04 (q, J = 4.0 Hz, 1H), 4.91 (t, J = 8.0 Hz, 1H), 4.44 (dd,
J = 3.2 Hz, 4.4 Hz, 1H), 4.30 (t, J = 4.8 Hz, 1H), 3.35 (s, 1H),
2.47 (q, J = 8.0 Hz, 4H), 1.64-1.55 (m, 2H), 1.26 (s, 1H), 0.94 (t,
J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 143.7, 143.5,
137.5, 132.1, 131.8, 129.8, 129.3, 129.2, 129.0, 128.9, 128.3,
127.4, 127.2, 126.8, 113.3, 53.5, 52.4, 37.2, 24.9, 21.6, 13.9; MS
(ESI) calcd m/z for C26H28N2O2S (Mþ) 432.58, found 455.36
(M þ Na)þ. Anal. Calcd for C26H28N2O2S: C, 72.19; H, 6.52; N,
6.48. Found: C, 72.45; H, 6.89; N, 6.87.
(1R,2R)-N-[2-(2,4-Dimethoxyphenylamino)-1,2-dihydronaphtha-
len-1-yl]-4-methylbenzenesulfonamide (6f). Following the general
procedure (III), 6f was obtained as a white solid (52.2 mg, 58%):
Rf = 0.26 on silica gel (ethyl acetate/petroleum ether = 1:4, v/v);
mp 140-142 °C; ee was determined to be 97% using HPLC analysis
on a Chiralcel AD-H column (hexane/2-propanol = 90/10, 0.5 mL/
min, λ= 254 nm); retention times were 102.3 min (major) and 116.0
(1R,2R)-N-[2-(4-Bromophenylamino)-1,2-dihydronaphthalen-
1-yl]-4-methylbenzenesulfonamide (6h). Following the general
procedure (III), 6h was obtained as a white solid (78.8 mg,
84%): Rf = 0.15 on silica gel (ethyl acetate/petroleum ether =
1:6, v/v); mp 165-167 °C; ee was determined to be 22% using
HPLC analysis on a Chiralcel AD-H column (hexane/2-propa-
nol = 90/10, 0.5 mL/min, λ = 254 nm); retention times were
min (minor); [R]20D = -108.4 (c = 1.00, CHCl3); IR (KBr, cm-1
)
67.2 min (major) and 88.5 min (minor); [R]20 = -51.6 (c =
D
3258(w), 2924 (m), 1596(w), 1514(s), 1453(m), 1416(m), 1497(m),
1289(m), 1205(m), 1156(s), 1093(w), 1032(m), 796(m), 664(m),
1.00, CHCl3); IR (KBr, cm-1) 3276(w), 3028(w), 2848(w),
1592(s), 1493(s), 1402(m), 1317(s), 1156(s), 1092(m), 812 (s),
663(m), 571(m), 547(m); 1H NMR (400 MHz, CDCl3) δ 7.73 (d,
J = 8.0 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 7.15 (t, J = 8.0 Hz,
2H), 7.10 (d, J = 7.6 Hz, 1H), 7.01 (t, J = 7.2 Hz, 1H), 6.71 (t,
J = 7.6 Hz, 1H), 6.59-6.56 (m, 4H), 6.05 (q, J = 4.0 Hz, 1H),
4.87 (d, J = 7.6 Hz, 1H), 4.45 (dd, J = 3.6 Hz, 4.4 Hz, 1H), 4.33
(t, J = 4.0 Hz, 1H), 3.46 (s, 1H), 2.44 (s, 3H); 13C NMR (100
MHz, CDCl3) δ 144.9, 143.7, 137.3, 132.1, 131.8, 131.7, 129.8,
129.3, 129.2, 129.0, 128.5, 127.3, 126.2, 114.9, 109.4, 53.3, 52.3,
21.6; MS (ESI) calcd m/z for C23H21BrN2O2S (Mþ) 469.39,
found 491.30 (M þ Na)þ. Anal. Calcd for C23H21BrN2O2S: C,
58.85; H, 4.51; N, 5.97. Found: C, 58.49; H, 4.90; N, 6.25.
1
566(m); H NMR (400 MHz, CDCl3) δ 7.73 (d, J = 8.0 Hz,
2H), 7.28 (d, J = 8.0 Hz, 2H), 7.22 (t, J = 6.4 Hz, 1H), 7.10 (d, J =
7.6 Hz, 1H), 7.00 (t, J = 7.2 Hz, 1H), 6.81 (d, J = 8.4 Hz, 1H), 6.59
(d, J = 9.6 Hz, 1H), 6.54 (d, J = 7.2 Hz, 1H), 6.46 (dd, J = 2.4 Hz,
6.0 Hz, 1H), 6.38 (d, J = 2.4 Hz, 1H), 6.08 (q, J = 4.0 Hz, 1H), 4.95
(s, 1H), 4.47 (dd, J = 2.4 Hz, 5.2 Hz, 1H), 4.28 (q, J = 2.4 Hz, 1H),
3.78 (s, 3H), 3.63 (s, 3H), 2.45 (s, 3H), 1.28 (s, 1H); 13C NMR
(100 MHz, CDCl3) δ 149.6, 145.5, 140.9, 134.9, 129.5, 129.2, 127.2,
127.1, 126.7, 126.3, 125.6, 124.8, 124.6, 124.1, 108.6, 101.3, 96.7,
53.2, 52.7, 50.8, 50.2, 19.0; MS (ESI) calcd m/z for C25H26N2O4S
(Mþ) 450.55, found 473.30 (M þ Na)þ. Anal. Calcd for C25H26-
N2O4S: C, 66.64; H, 5.82; N, 6.22. Found: C, 66.34; H, 6.12; N, 6.62.
(1R,2R)-N-[2-(4-Propylphenylamino)-1,2-dihydronaphthalen-
1-yl]-4-methylbenzenesulfonamide (6g). Following the general
procedure (III), 6g was obtained as colorless oil (48.4 mg, 56%):
Rf = 0.15 on silica gel (ethyl acetate/petroleum ether = 1:6,
v/v); ee was determined to be 94% using HPLC analysis on a
Chiralcel AD-H column (hexane/2-propanol = 90/10, 0.5 mL/
min, λ = 254 nm); retention times were 40.9 min (major) and
43.9 min (minor); [R]20D = -116.4 (c = 1.00, CHCl3); IR (KBr,
cm-1) 3394(w), 3276(m), 3037 (w), 2957(m), 2927(m), 2870(w),
1615 (m), 1518(s), 1454(w), 1412(m), 1329(m), 1160(s), 1094(m),
Acknowledgment. We are grateful to the National Natural
Science Foundation of China (Nos. 20772036 and 20802021)
and the Natural Science Foundation of Guangdong Province
(Nos. 8251063101000002 and 7005804) for financial support.
1
Supporting Information Available: Copies of H and 13C
NMR spectra of compounds 2a-2m, 4a-4d, and 6a-6h, and
X-ray structure data for compound 2g. This material is available
free of charge via the Internet at http://pubs.acs.org.
J. Org. Chem. Vol. 75, No. 21, 2010 7299