Phosphine-oxazoline ligands with an axial-unfixed biphenyl backbone: the effects of the substituent at oxazoline ring and P phenyl ring on Pd-catalyzed asymmetric allylic alkylation

Article abstract of DOI:10.1016/j.tet.2009.09.053

A novel kind of chiral phosphine-oxazoline ligands 3 with an axial-unfixed biphenyl backbone bearing different substituent on oxazoline ring and P phenyl ring was prepared. These ligands exist as a mixture of two diastereomers in equilibrium in solution.

Full text of DOI:10.1016/j.tet.2009.09.053

Tetrahedron 65 (2009) 9609–9615
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Phosphine-oxazoline ligands with an axial-unfixed biphenyl backbone: the effects
of the substituent at oxazoline ring and P phenyl ring on Pd-catalyzed asymmetric
allylic alkylation
*
Fengtao Tian, Dongmei Yao, Yong Jian Zhang, Wanbin Zhang
School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2009
Received in revised form 8 September 2009
Accepted 11 September 2009
Available online 17 September 2009
A novel kind of chiral phosphine-oxazoline ligands 3 with an axial-unfixed biphenyl backbone bearing
differentsubstituentonoxazolinering and P phenyl ringwasprepared. Theseligandsexistasa mixtureof two
diastereomers in equilibrium in solution. Upon coordinated to Pd(II), however, only one of the two possible
kindsofdiastereomercomplexeswithdifferentaxialchirality wasformed.Thesecompoundsaschiralligands
were applied in Pd-catalyzed asymmetric allylic alkylation with high reaction activity and enantioselectivity.
Meanwhile, theasymmetriccatalyticbehavior wasaffectedobviously by thesubstituentatoxazolinering and
P phenylring. Thebest result, upto 92.3% eeand99%yield, wasobtained withthe ligand3chavingtwo phenyl
groups on P and a phenyl group on oxazoline ring in this asymmetric catalysis reaction.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
possible diastereomeric complexes were formed and showed excel-
lent enantioselectivities in metal-catalyzed asymmetric reactions.
Transition metal-catalyzed asymmetric synthesis is one of the
most interesting and challenging fields in the modern organic
chemistry.1 Since chiral ligand is one of the origins of asymmetric
induction, the design and synthesis of novel chiral ligands are always
the key issues in the development of efficient catalysis systems.2
Among the various chiral ligands, axially chiral biaryl ligands draw
much attention because they exhibit excellent chirality transfer
properties.3 In view of atom economy, traditional axial-fixed ligands
require inconvenient enantiomer resolution or diastereomer
separation in their synthetic processes, and generally, only one
enantiomeric or diastereomeric pure form of the ligands works
effectively in catalytic asymmetric reactions for industrial uses.
Whereas the axial flexible ligands can afford completely a single en-
antiomeric or diastereomeric metal catalyst on complexing process
without any ligand wasting.4 Chiral oxazoline ligands derived from
readily available amino acids have found widespread use in metal-
catalyzed asymmetric reactions, and extensive efforts have been
devoted to the preparation of their efficient structural derivatives.5
Recently, we had reported a novel C2-symmetricbisoxazolineligand 1
bearing an axial-unfixed biphenyl backbone (Fig. 1).6 These ligands
existasanequilibriummixtureofdiastereomersinsolutionasaresult
of rotation around the internal bond of the biphenyl. When these
ligands coordinated to metal, interestingly, only one of the two
R
R
O
R
Ar2P
N
Ph2P
N
N
N
O
O
O
R
3
1
2
Figure 1. Chiral axial oxazoline ligands.
EversincePHOXligandswereintroducedbyPflatz,Helmchen, and
Williams,7 which showed excellent reactivity and enantioselectivity
inmanyasymmetricreactions, structuremodificationoftheseligands
has been continuing by introducing chiral elements into the ligand
backbone.5i,l Several groups including us had independently
developed a novel kind of chiral phosphino-oxazoline ligands 2 with
anaxial-fixed binaphthyl backbone(Fig.1).8,9 These chiralP,N-ligands
were successfullyemployed in metal-catalyzed asymmetric reactions
and showed excellent enantioselectivities. Taking into account of the
advantages of chiral P,N-chelating binaphthyl ligands 2 and axial-
unfixed biphenyl ligand 1 with high usage efficiencyand unnecessary
resolution process, we designed a novel kind of chiral phosphine-
oxazoline ligands 3 (R¼i-Pr, t-Bu, Ar¼Ph) with an axial-unfixed
biphenyl backbone (Fig. 1), which showed excellent reactivity and
enantioselectivity in Pd-catalyzed allylic alkylation.10 In order to
furtherexplore theeffectof thesubstituentattheoxazolineringand P
* Corresponding author. Tel./fax: þ86 21 54743265.
E-mail address: wanbin@sjtu.edu.cn (W. Zhang).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.09.053

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F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
Pd(OAc)2
DPPB
Tf2O
Ar2P(O)H
OTf
O
OTf
OH
Ar2P
HO
TfO
pyridine
100%
i-Pr2NEt
5
4
5a:Ar=Ph, 83%
5b:Ar=4-MeOPh, 65%
5c:Ar=3,5-t-Bu2Ph, 76%
5d:Ar=3,5-t-Bu2-4-MeOPh, 81%
Pd(OAc)2
DPPP
H
N
R
CO(1 atm)
O
Ar2P
COOMe
O
Ar2P
NaH,aminoalchol
O
HO
i-Pr2NEt,MeOH
6
7
6a:Ar=Ph, 84%
7a:R=i-Pr,Ar=Ph, 79%
7b:R=t-Bu,Ar=Ph, 62%
7c:R=Ph,Ar=Ph, 76%
6b:Ar=4-MeOPh, 67%
6c:Ar=3,5-t-Bu2Ph, 79%
6d:Ar=3,5-t-Bu2-4-MeOPh, 78%
7d:R=Ph,Ar=4-MeOPh, 73%
7e:R=Ph,Ar=3,5-t-Bu2Ph, 77%
7f :R=Ph,Ar=3,5-t-Bu2-4-MeOPh, 75%
O
O
HSiCl3
Et3N
MesCl
Et3N
O
Ar2P
N
Ar2P
N
R
R
8
3
3a:R=i-Pr,Ar=Ph, 67%
3b:R=t-Bu,Ar=Ph, 80%
3c:R=Ph,Ar=Ph, 77%
8a:R=i-Pr,Ar=Ph, 93%
8b:R=t-Bu,Ar=Ph, 97%
8c:R=Ph,Ar=Ph, 96%
3d:R=Ph,Ar=4-MeOPh, 73%
3e:R=Ph,Ar=3,5-t-Bu2Ph, 71%
8d:R=Ph,Ar=4-MeOPh, 90%
8e:R=Ph,Ar=3,5-t-Bu2Ph, 93%
3f :R=Ph,Ar=3,5-t-Bu2-4-MeOPh, 78%
8f :R=Ph,Ar=3,5-t-Bu2-4-MeOPh, 96%
Scheme 1. Synthesis of axial-unfixed biphenyl phosphine-oxazoline ligands.
phenyl ring, we report here the synthesis and complexation of 3a–f,
and their application in the Pd-catalyzed asymmetric allylic
alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malo-
nate with excellent reaction activity and enantioselectivity.
Table 1
Diastereomeric ratio of ligands and complexes
a
b
c
d
e
f
(aS)-3:(aR)-3
(aS)-10:(aR)-10
52:48
100:0
53:47
100:0
51:49
100:0
53:47
100:0
55:45
100:0
56:44
100:0
Determined by 1H NMR and 31P NMR in CDCl3 at 24 ꢀC.
2. Results and discussions
2.1. Ligands preparation
according to their 1H NMR and 31P NMR in CDCl3. If the temperature
was changed, the ratio of the two diastereomers was also changed. This
indicated that the ligands exist in an equilibrium due to the rotation
around the internal bond of the biphenyl backbone (Scheme 2). It was
also found that either the bulkiness of the substituents on the oxazoline
ring or the substituent on the P phenyl ring had little effect on the ratio
of the two diastereomers for the derivatives 3a–3f.
Ligands were prepared from 2,20-dihydroxyl biphenyl as illustrated
in Scheme 1. 2,20-Dihydroxyl biphenyl was treated with tri-
fluoromethanesulfonic anhydride (Tf2O) in the presence of pyridine to
give triflate 4 in quantitative yield. Then Pd-catalyzed insertion re-
actions of 4 with different diarylphosphine oxides were carried out
smoothly to afford compounds 5 in 65–83% yield. Next, in the presence
of methanol, Pd-catalyzed carboxylation reactions of 5 with CO gave
monocarboxylic acid esters 6 in 67–84% yield. In the presence of
a catalytic amount of sodium hydride, the reaction of compounds 6
with amino alcohol afforded amide compounds 7 in 62–79% yield.
Then, compounds 7 were treated with methanesulfonyl chloride in the
presence of triethylamine to give cyclic chiral monooxazoline com-
pounds 8 in 90–97% yield. Finally, the reduction of 8 with tri-
chlorosilane afforded the novel chiral ligands 3 in 67–80% yield, which
are stable enough to be purified by silica gel column chromatography.
The final ligands were obtained in 21–39% overall yield after six steps.
2.3. Complexation behavior of ligands with Pd(II)
The complexation behavior of ligands 3a–3f with Pd(II) using
complex [Pd(h
3-1,3-diphenylallyl)Cl]2 in solution was then ex-
amined. Upon coordinated to the Pd complex, interestingly, all of
the ligands gave only one of the two possible diastereomer
complexes 9a–f with different axial chirality in CDCl3, re-
spectively, according to their 1H NMR and 31P NMR spectra
(Scheme 2 and Table 1).
It was reported that the absolute configuration of 2,20-bridged
biphenyl compounds could be determined by their CD spectrum.11
We chose 9a and 9b as representatives to determine their absolute
axial chirality configuration by CD spectrum. Both 9a and 9b dis-
played negative Cotton effect at 260 nm. The results suggested that
2.2. Behavior of the ligands in solution
The behavior of ligands 3 in solution was then investigated. As
showninTable 1, allof theligandsexist as twodiastereomers in solution

F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
9611
O
O
Ar2P
N
N
PAr2
R
R
(aR)-3a-f
(aS)-3a-f
Pd (II)
Pd (II)
O
O
N
Pd
Pd
Ar2P
N
PAr2
R
R
(aS)-9a-f
(aR)-9a-f
not found
P
N
Pd
Ph
Ph
9a-f
Scheme 2. Complexation behavior of ligands 3a–f.
Figure 2. ORTEP view of complex (aS)-10.
the axial chirality of both 9a and 9b was characterized as S con-
figuration, which were in contrast with the spectra in the literature
of axially chiral biphenyl compounds. The axial configurations of
9c–f were assigned by comparison of their 1H NMR spectrum with
that of 9a and 9b.
We also attempted to confirm the complex configuration by
single-crystal X-ray analysis. Unfortunately, we could not obtain
crystals of 9a–f suitable for X-ray diffraction analysis. So, the
complex 10 was obtained by complexing ligand 3c with
Pd(CH3CN)2Cl2 in CH2Cl2 (Scheme 3), which could be easily crys-
tallized from CH2Cl2/hexane and afforded crystals suitable for
X-ray diffraction analysis. The X-ray diffraction analysis revealed
that the ligand 3c coordinated Pd(II) with phosphorus and nitro-
gen atoms, as illustrated in Figure 2, and the complex 10 has an S
configuration. This result was in accord with that determined by
CD spectrum.
O
R
O
N
N
Ph2P
Ph2P
Ph
Pd
Pd
R
Ha
Ph
Ph
Ph
Ha
W-type
Major
M-type
Minor
No NOE
NOE: 9a 0.4%
9b 2.8%
Scheme 4. NOE model of 9a–b.
reaction was carried out by using 1,3-diphenyl-2-propenyl acetate
as a typical substrate, bis(trimethylsilyl)acetamide (BSA) as a base,
and dimethyl malonate as a nucleophile. The results are summa-
rized in Table 2.
O
O
Cl
Pd(CH3CN)2Cl2
CH2Cl2
Pd
Ph2P
N
Ph2P
N
Initially, screening of solvents and additives was carried out.
Although THF afforded the highest ee in the reactions without any
additives (entries 1–3), CH2Cl2 was the suitable solvent when ad-
ditive was added (entry 5 vs entries 3, 4). The results also showed
that LiOAc was better than NaOAc or KOAc (entries 5–7), NaBArF
(sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate) was also an
efficient additive in this reaction (entry 8), while Cs2CO3 gave good
yield and moderate enantioselectivity (entry 9). From the above
results, it is obvious that CH2Cl2 was the suitable solvent and LiOAc
was the suitable additive.
Then, the temperature effect was investigated. Whether the
temperature rised (entry 10) or decreased (entries 11, 12), the re-
action activity and enantioselectivity changed dramatically. When
the temperature decreased to ꢁ20 ꢀC (entry 12), the reaction al-
most ceased. The results showed that the suitable reaction tem-
perature was 20 ꢀC.
Cl
Ph
Ph
(aS)-10
3c
Scheme 3. Synthesis of complex 10.
Furthermore, we found that all of the complexes 9a–f exist in
two diastereomeric intermediates with W- and M-types observed
in their 1H and 31P NMR spectra. With 9a–b as representatives, two
diastereomeric intermediates with W- and M-type were observed
in the ratio of 54:46, and 58:42, respectively (Scheme 4). According
to their NOE spectrum, the major was assigned as W-type because
there are NOE observations between the proton of the substituent
on oxazoline and Ha, and the minor was assigned as M-type
because there are no NOE observations (Scheme 4).
2.4. Application in Pd-catalyzed asymmetric alkylation
Next, the phosphine-oxazoline ligands bearing different sub-
stituents on the oxazoline ring and different aryl groups on P atom
were investigated. Almost all of the ligands afforded full conver-
sion. Ligand 3c led to the highest enatioselectivity (92.3% ee, entry
14), whereas ligand 3a with i-Pr (entry 5) or ligand 3b with t-Bu
Pd-catalyzed asymmetric allylic alkylation as one of the im-
portant C–C bond forming asymmetric reactions has been in-
vestigated using various chiral phosphine-oxazoline ligands.12,13
We also chose this reaction as the model reaction in this paper. The

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F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
Table 2
oxazoline ring, which afforded 92.3% ee. Furthermore, the stability
and reactivity of intermediates 9 were discussed.
Pd-catalyzed asymmetric allylic alkylationa
CH2(CO2Me)2/BSA
OAc
Ph
MeO2C
Ph
CO2Me
Ph
4. Experimental
Ph
3
[Pd( -C3H5)Cl]2
Ligand
4.1. General
Entry Ligand Additive Solvent T (ꢀC) Time (h) Yieldb (%) %eec (config)d
All air- and moisture-sensitive manipulations were carried out
with standard Schlenk techniques under nitrogen. The reaction
solvents were distilled prior to use (toluene and dichloromethane
were distilled from CaH2, THF was distilled from Na). The commer-
cially available reagents were used without further purification.
Column chromatography was run on silica gel (100–200 mesh).
Melting points were measured on an X-4 microscopic melting point
apparatus and are uncorrected. 1H, 13C, and 31P NMR spectra were
recorded on a Varian MERCURYplus-400 spectrometer. The ee values
were determined by HPLC using a Daicel Chiralcel OD-H column.
HRMS was performed on a Micromass LCTTM at the Analysis and
Research Center of East China University of Science and Technology.
1
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3b
3c
3d
3e
3f
None
None
None
LiOAc
LiOAc
NaOAc
KOAc
CH2Cl2
Toluene
THF
20 48
20 48
20 48
20 24
20 24
20 24
20 24
68
62
76
99
99
99
99
99
99
99
80
Trace
99
99
99
99
99
85.7 (S)
83.7 (S)
86.3 (S)
85.5 (S)
86.5 (S)
81.5 (S)
83.2 (S)
83.7 (S)
53.0 (S)
56.0 (S)
60.5 (S)
Nde
2
3
4
THF
5
6
7
CH2Cl2
CH2Cl2
CH2Cl2
8
9
NaBARF CH2Cl2
20
20
3
3
Cs2CO3
LiOAc
LiOAc
LiOAc
LiOAc
LiOAc
LiOAc
LiOAc
LiOAc
CH2Cl2
CH2Cl2
CH2Cl2
10
11
12
13
14
15
16
17
35 24
24
0
CH2Cl2 ꢁ20 24
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
20 24
20 24
20 24
20 24
20 24
90.0 (S)
92.3 (S)
67.7 (S)
75.5 (S)
85.3 (S)
4.2. Synthesis of biphenyl-2,20-diyl bis(trifluoro
methanesulfonate) 4
2,20-Dihydroxyl biphenyl (4.30 g, 23 mmol) was dissolved in
a solution of dry pyridine (7.0 mL) in dry CH2Cl2 (70 mL) under N2.
To this solution was added Tf2O (13.0 g, 46 mmol) slowly at 0 ꢀC.
The reaction was carried out at 0 ꢀC for 3 h, at which time TLC in-
dicated that the reaction was completed. The reaction mixture was
diluted with CH2Cl2 and washed subsequently with 1 M HCl, 1 M
NaHCO3, and brine. The CH2Cl2 solution was dried over anhydrous
Na2SO4 and the solvent was removed under reduced pressure. The
residue was purified by column chromatography with ethyl acetate
and petroleum ether (1:9) as eluent to afford biphenyl-2,20-diyl
bis(trifluoro methanesulfonate) (10.3 g, 100%, white solid). Mp
a
Conducted with 1,3-diphenyl-2-propenyl acetate (1 mmol), dimethyl malonate
mol) in 3 mL of solvent under nitrogen in
the presence of the catalyst, which was prepared from ligand (30
mol) and [Pd(h3
C3H5)Cl]2 (13 mol) in 1 mL solvent for 1 h before use.
(3 mmol), BSA (3 mmol), and LiOAc (20
m
m
-
m
b
Isolated yield.
Determined by HPLC (Chiralcel OD).
Determined by comparing the sign of its optical rotation with literature data.
Not determined.
c
d
e
(entry 13) gave 86.5% ee and 90.0% ee, respectively. Notably, the
different aryl groups on P have great influence on the enatiose-
lectivity, ligand 3d–f gave 67.7% ee, 75.5% ee and 85.% ee, re-
spectively (entries 15–17). The results showed that the substituents
on oxazoline ring have a slight effect on the enantioselectivity,
whereas the substituents on the P phenyl ring have a significant
effect on this reaction.
35–36 ꢀC. 1H NMR (400 MHz, CDCl3):
d
7.44 (dd, J¼1.5, 8.1 Hz, 2H),
7.48 (dd, J¼2.2, 7.3 Hz, 2H), 7.51 (td, J¼1.5, 7.3 Hz, 2H), 7.56 (ddd,
J¼2.2, 8.1, 7.3 Hz, 2H).
4.3. General procedure for the synthesis of 5
Finally, the reactivities of the two diastereomers of intermediate
9 were discussed. For the asymmetric allylic alkylation, it is known
that, the W-type intermediate leads to the product of R configu-
ration and the M-type one leads to the product of S configuration,
because the trans effect directs nucleophilic attack to the allylic
terminus trans to phosphorus atom.14 In the present case, the S
configured product was obtained with all of the ligands 3. This
result suggested that the two conformers may have different re-
activity with the nucleophile. The minor M-type diastereomer of 9
has much more reactivity than the major W-type one (Scheme 4),
due to the position trans to the phosphorus atom becoming more
cationic caused by the steric repulsion between the substituent on
oxazoline ring and phenyl group.
Biphenyl-2,20-diyl bis(trifluoromethanesulfonate) (4) (1.9 g,
4.1 mmol), Pd(OAc)2, DPPB (88 mg, 0.21 mmol), and diaryl-
phosphine oxide (4.8 mmol) were added to a two-neck flask under
N2. To this flask were added dry DMSO (20 mL) and DIPEA (2.9 mL,
16 mmol). The reaction mixture was heated to 100 ꢀC for 8 h, at
which time TLC indicated that the reaction was completed. The
reaction mixture was diluted with CH2Cl2 and washed sub-
sequently with 1 M HCl, 1 M NaHCO3, and brine. The CH2Cl2 solu-
tion was dried over anhydrous Na2SO4 and the solvent was
removed under reduced pressure. The residue was purified by
column chromatography with ethyl acetate and petroleum ether as
eluent to afford compound 5.
4.3.1. Compound 5a. 83% yield, white powder. Mp 120–122 ꢀC. 1H
3. Conclusions
NMR (400 MHz, CDCl3): d 6.90–6.93 (m, 1H), 7.23–7.26 (m, 2H),
7.28–7.32 (m, 2H), 7.37–7.56 (m, 10H), 7.58–7.64 (m, 1H), 7.65–7.71
(m, 2H).
In conclusion, we have developed a novel chiral phosphine-
oxazoline ligand 3 with an axial-unfixed biphenyl backbone bear-
ing different substituents on oxazoline ring and P phenyl ring.
These ligands exist as a mixture of two diastereomers in equilib-
rium in solution. Upon coordinated to Pd(II), only one of the two
possible kinds of diastereomer complexes with different axial chi-
rality was formed. These compounds were applied as chiral ligands
in Pd-catalyzed asymmetric allylic alkylation and the effects of the
substituents were examined. The best result was obtained with the
ligand 3c having two phenyl groups on P and a phenyl group on
4.3.2. Compound 5b. 65% yield, pale yellow solid. Mp 106–108 ꢀC.
1H NMR (400 MHz, CDCl3):
d 3.79 (s, 3H), 3.84 (s, 3H), 6.77–6.83
(m, 2H), 6.90–6.98 (m, 3H), 7.22–7.27 (m, 2H), 7.32–7.48 (m, 6H),
7.50–7.60 (m, 3H). HRMS (Micromass LCT) calcd for C27H22F3O6PS
(MþH)þ: 563.0905; found: 563.0893.
4.3.3. Compound 5c. 76% yield, white powder. Mp 147–149 ꢀC. 1H
NMR (400 MHz, CDCl3):
d 1.24 (s, 18H), 1.28 (s, 18H), 6.90–6.94

F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
9613
(m, 1H), 7.15–7.24 (m, 2H), 7.33–7.46 (m, 7H), 7.50–7.60 (m, 4H).
HRMS (Micromass LCT) calcd for C41H50F3O4PS (MþH)þ: 727.3198;
found: 727.3170.
6.62–6.68 (m, 2H), 7.17–7.62 (m, 25H), 7.68 (dd, J¼0.7, 7.7 Hz, 1H),
7.70–7.77 (m, 4H), 8.40 (dd, J¼0.7, 9.2 Hz,1H), 8.83 (d, J¼8.4 Hz,1H).
4.5.2. Compound 7b. 62% yield, viscous oil. 1H NMR (400 MHz,
4.3.4. Compound 5d. 81% yield, white powder. Mp 114–115 ꢀC. 1H
CDCl3) (major/minor¼58:42 in CDCl3):
d 0.61 (s, 9H), 1.03 (s, 9H),
NMR (400 MHz, CDCl3):
d
1.32 (s, 18H), 1.35 (s, 18H), 3.66 (s, 3H),
3.28–3.35 (m, 1H), 3.50–3.57 (m, 1H), 3.72–3.90 (m, 4H), 6.12 (dd,
J¼1.1, 7.3 Hz, 1H), 6.15 (dd, J¼0.7, 7.7 Hz, 1H), 6.60 (d, J¼1.1, 7.7 Hz,
1H), 6.68 (td, J¼1.1, 7.3 Hz, 1H), 7.18–7.81 (m, 30H), 8.13 (d, J¼9.9 Hz,
1H), 8.44 (d, J¼8.8 Hz, 1H).
3.70 (s, 3H), 7.00–7.03 (m, 1H), 7.18–7.25 (m, 1H), 7.35–7.47 (m, 9H),
7.55–7.60 (m, 1H). HRMS (Micromass LCT) calcd for C43H54F3O6PS
(MþH)þ: 787.3409; found: 787.3397.
4.4. General procedure for the synthesis of 6
4.5.3. Compound 7c. 76% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼56:44 in CDCl3):
d 3.32–3.41 (m, 3H),
A
mixture of triflates
5
(11.3 mmol), Pd(OAc)2 (381.7 mg,
3.47–3.57 (m, 2H), 3.72–3.90 (m, 1H), 6.64 (d, J¼7.7 Hz, 1H), 6.72
(d, J¼7.3 Hz, 1H), 7.18–7.81 (m, 42H), 8.18 (d, J¼9.9 Hz, 1H), 8.48
(d, J¼8.8 Hz, 1H).
1.70 mmol), DPPP (701.1 mg, 1.70 mmol), MeOH (60 mL), DMSO
(90 mL), and Et3N (24 mL) was saturated with CO and freeze-
pumped for three times, and then stirred under a CO atmosphere at
70 ꢀC. The reaction mixture was monitored by TLC for full conver-
sion. After cooling to room temperature, the mixture was concen-
trated at reduced pressure. The residue was diluted with CH2Cl2
and washed with 1 M HCl and brine. The organic phase was dried
over anhydrous Na2SO4 and the solvent was removed under re-
duced pressure. The residue was chromatographed on silica gel
eluted with ethyl acetate and petroleum ether to afford esters 6.
4.5.4. Compound 7d. 73% yield, viscous oil. 1H NMR (400 MHz,
CDCl3) (major/minor¼62:38 in CDCl3):
d 3.83 (s, 3H), 3.84 (s, 3H),
3.88 (s, 3H), 3.89 (s, 3H), 4.95–5.03 (m, 1H), 6.15 (d, J¼7.8 Hz, 1H),
6.21 (dd, J¼7.8, 17.6 Hz, 1H), 6.54 (d, J¼8.0 Hz, 1H), 6.73 (dt, J¼1.2,
8.0 Hz, 1H), 6.83 (dt, J¼1.2, 8.0 Hz, 1H), 6.89–7.69 (m, 42H).
4.5.5. Compound 7e. 77% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼55:45 in CDCl3):
d 1.19 (s, 18H), 1.22 (s, 18H),
1.24 (s, 18H), 1.28 (s, 18H), 3.28–3.35 (m, 3H), 3.50–3.57 (m, 2H),
4.95–5.10 (m, 1H), 5.98–6.04 (m, 1H), 6.46–6.59 (m, 2H), 6.91–7.85
4.4.1. Compound 6a. 84% yield, white powder. Mp 93–95 ꢀC. 1H
NMR (400 MHz, CDCl3):
(m, 12H).
d 3.64 (s, 3H), 7.18–7.27 (m, 6H), 7.33–7.65
(m, 34H), 8.56–9.72 (m, 1H). 31P NMR (161 MHz, CDCl3):
33.9.
d 35.2,
4.4.2. Compound 6b. 67% yield, pale yellow powder. Mp 60–64 ꢀC.
1H NMR (400 MHz, CDCl3):
3.56 (s, 3H), 3.78 (s, 3H), 3.79 (s, 3H),
d
4.5.6. Compound 7f. 75% yield, white foam. 1H NMR (400 MHz,
1.26 (s, 18H), 1.30 (s, 18H),
6.78–6.84 (m, 4H), 6.92–6.95 (m, 1H), 7.04–7.18 (m, 6H), 7.24–7.38
(m, 4H), 7.92–7.96 (m, 1H). HRMS (Micromass LCT) calcd for
C28H25O5P (MþH)þ: 473.1518; found: 473.1527.
CDCl3) (major/minor¼52:48 in CDCl3):
d
1.32 (s, 18H), 1.35 (s, 18H), 3.26–3.37 (m, 3H), 3.51–3.56 (m, 2H),
3.72 (s, 3H), 3.75 (s, 3H), 4.93–5.10 (m, 1H), 5.98–6.04 (m, 1H),
6.46–6.59 (m, 2H), 7.16–7.71 (m, 36H), 9.56–9.72 (m, 1H). 31P NMR
4.4.3. Compound 6c. 79% yield, white powder. Mp 69–72 ꢀC. 1H
(161 MHz, CDCl3): d 35.4, 34.3.
NMR (400 MHz, CDCl3):
d 1.24 (s, 18H), 1.25 (s, 18H), 3.68 (s, 3H),
7.05–7.21 (m, 4H), 7.32–7.54 (m, 9H), 7.73–7.77 (m, 1H). HRMS
(Micromass LCT) calcd for C42H53O3P (MþH)þ: 637.3811; found:
637.3804.
4.6. General procedure for the synthesis of compound 8
To a solution of 7 (0.9 mmol), triethylamine (0.44 mL, 3.1 mmol)
in dichloromethane (6.0 mL) was added methanesulfonyl chloride
(90 m
L) at 0 ꢀC. The mixture was stirred for 30 min and then the
4.4.4. Compound 6d. 78% yield, white powder. Mp 75–78 ꢀC. 1H
NMR (400 MHz, CDCl3):
d
1.32 (s, 18H), 1.35 (s, 18H), 3.64 (s, 3H),
resulting mixture was warmed to room temperature. The reaction
was monitored with TLC for a full conversion. The reaction was
quenched with water and diluted with CH2Cl2 and washed with
1 M HCl and brine. The organic phase was dried over Na2SO4 and
the solvent was removed under reduced pressure. The residue was
chromatographed on silica gel eluted with ethyl acetate/petroleum
ether to afford ligands 8.
3.65 (s, 3H), 3.67 (s, 3H), 7.09–7.18 (m, 4H), 7.33–7.52 (m, 7H),
7.77–7.81 (m, 1H). HRMS (Micromass LCT) calcd for C44H57O5P
(MþH)þ: 697.4022; found: 697.4017.
4.5. General procedure for the synthesis of 7
A solution of L-amino alcohol (3.0 mmol) in THF (8.0 mL) was
added to a two-neck flask, which charged with NaH (60 mg,
1.5 mmol) at 0 ꢀC. After stirring at rt for 1 h, at which time white
precipitate emerged, the mixture was cooled to 0 ꢀC again and
a solution of 6 (1.0 mmol) in THF (8.0 mL) was added. The reaction
mixture was stirred at rt overnight and monitored by TLC for full
conversion. The reaction was quenched with water and concen-
trated at reduced pressure. The residue was diluted with CH2Cl2
and washed with 1 M HCl and brine. The organic phase was dried
over anhydrous Na2SO4 and the solvent was removed under re-
duced pressure. The residue was chromatographed on silica gel
eluted with ethyl acetate and petroleum ether to afford esters 7.
4.6.1. Compound 8a. 93% yield, viscous oil. 1H NMR (400 MHz,
CDCl3): (major/minor¼52:48 in CDCl3):
d
0.81 (d, J¼1.5 Hz, 3H),
0.83 (d, J¼1.5 Hz, 3H), 0.84 (d, J¼3.7 Hz, 3H), 0.85 (d, J¼3.7 Hz, 3H),
1.55–1.64 (m, 1H), 1.66–1.77 (m, 1H), 3.74 (t, J¼8.4 Hz, 1H),
3.79–3.88 (m, 3H), 4.01 (dd, J¼11.9, 12.8 Hz, 1H), 4.15 (t, J¼8.5 Hz,
1H), 7.10–7.18 (m, 5H), 7.18–7.65 (m, 29H), 7.69–7.75 (m, 2H). 31P
NMR (161 MHz, CDCl3):
d 28.6, 29.3.
4.6.2. Compound 8b. 97% yield, viscous oil. 1H NMR (400 MHz,
CDCl3) (major/minor¼55:45 in CDCl3):
d 0.77 (s, 9H), 0.82 (s, 9H),
3.78–3.85 (m, 3H), 3.95 (d, J¼7.7 Hz, 1H), 3.96 (d, J¼9.9 Hz, 1H), 4.11
(t, J¼13.6 Hz, 1H), 7.05–7.64 (m, 34H), 7.71 (dd, J¼1.5, 11.4 Hz, 1H),
4.5.1. Compound 7a. 79% yield, viscous oil. 1H NMR (400 MHz,
7.73 (dd, J¼1.1, 11.4 Hz, 1H). 31P NMR (161 MHz, CDCl3):
d 28.3, 29.0.
CDCl3) (major/minor¼55:45 in CDCl3): 0.40 (d, J¼7.0 Hz, 3H), 0.75
d
(d, J¼6.6 Hz, 3H), 0.98 (d, J¼7.0 Hz, 3H), 1.01 (d, J¼7.0 Hz, 3H), 1.52–
1.67 (m, 1H), 1.89–2.00 (m, 1H), 2.44 (t, J¼6.6 Hz, 1H), 3.23–3.35 (m,
2H), 3.60–3.74 (m, 3H), 6.11 (d, J¼7.7 Hz, 1H), 6.14 (d, J¼7.7 Hz, 1H),
4.6.3. Compound 8c. 96% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼56:44 in CDCl3): 3.90 (t, J¼8.0 Hz, 1H), 3.93
(t, J¼8.0 Hz, 1H), 4.39 (dd, J¼8.0, 10.4 Hz, 1H), 4.54 (dd, J¼8.0,
d

9614
F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
10.4 Hz, 1H), 5.17 (t, J¼4.0 Hz, 1H), 5.20 (t, J¼4.0 Hz, 1H), 7.07–7.72
1H), 3.59 (dd, J¼4.8, 11.2 Hz, 1H), 3.71 (dd, J¼6.0, 11.2 Hz, 1H), 3.80
(dd, J¼4.8, 11.2 Hz, 1H), 5.28–5.37 (m, 2H), 6.15 (d, J¼6.8, 1H), 6.29
(d, J¼6.8,1H), 6.65 (t, J¼8.0 Hz, 2H), 6.77 (d, J¼8.0 Hz, 2H), 6.91–7.47
(m, 46H). 31P NMR (161 MHz, CDCl3):
d 28.1, 28.7. HRMS (Micromass
LCT) calcd for C33H26NO2P (MþH)þ: 500.1779; found: 500.1764.
(m, 38H), 7.81 (dd, J¼1.6, 8.0 Hz, 1H), 7.91 (dd, J¼1.6, 8.0 Hz, 1H). 31
P
4.6.4. Compound 8d. 90% yield, viscous oil. 1H NMR (400 MHz,
NMR (161 MHz, CDCl3):
d
ꢁ12.69, ꢁ12.85. HRMS (Micromass LCT)
CDCl3) (major/minor¼66:34 in CDCl3):
d
3.84 (s, 3H), 3.85 (s, 3H),
calcd for C33H26NOP (MþH)þ: 484.1830; found: 484.1833.
3.87 (s, 3H), 3.88 (s, 3H), 3.88–3.97 (m, 2H), 4.84–4.90 (m, 2H),
5.21–5.28 (m, 2H), 6.10 (dd, J¼1.2, 7.6 Hz,1H), 6.16 (dd, J¼1.2, 7.6 Hz,
1H), 6.68–7.60 (m, 38H), 9.70 (dd, J¼1.6, 8.0 Hz, 1H), 9.80 (dd, J¼1.6,
4.7.4. Compound 3d. 73% yield, viscous oil. 1H NMR (400 MHz,
3.73 (s, 3H), 3.75 (s, 3H),
CDCl3) (major/minor¼53:47 in CDCl3):
d
8.0 Hz, 1H). 31P NMR (161 MHz, CDCl3):
d
32.17, 32.19. HRMS
3.78 (s, 3H), 3.80 (s, 3H), 3.92 (t, J¼8.8 Hz, 1H), 4.01 (t, J¼8.8 Hz, 1H),
4.48 (dd, J¼7.8, 17.6 Hz, 1H), 4.61 (dd, J¼7.8, 17.6 Hz, 1H), 5.21 (t,
J¼9.2 Hz, 1H), 5.26 (t, J¼9.2 Hz, 1H), 6.57 (dd, J¼2.4, 8.8, 2H), 6.65
(dd, J¼2.4, 8.8, 2H), 6.78 (d, J¼8.8, 4H), 7.07–7.81 (m, 34H). 31P NMR
(Micromass LCT) calcd for C35H30NO4P (MþH)þ: 560.1991; found:
560.1990.
4.6.5. Compound 8e. 93% yield, white foam. 1H NMR (400 MHz,
(161 MHz, CDCl3):
d
ꢁ13.78, ꢁ13.92. HRMS (Micromass LCT) calcd
CDCl3) (major/minor¼58:42 in CDCl3):
d
1.18 (s, 18H), 1.22 (s, 18H),
for C35H30NO3P (MþH)þ: 544.2042; found: 544.2048.
1.23 (s, 18H), 1.24 (s, 18H), 3.82 (t, J¼9.2 Hz, 1H), 4.00 (t, J¼9.2 Hz,
1H), 4.58 (dd, J¼7.8, 17.6 Hz, 1H), 4.65 (dd, J¼7.8, 17.6 Hz,1H), 5.18 (t,
J¼9.2 Hz, 1H), 5.29 (t, J¼9.2 Hz, 1H), 7.05–7.56 (m, 36H), 7.71 (dd,
J¼1.6, 8.0 Hz, 1H), 7.75 (dd, J¼1.6, 8.0 Hz, 1H). 31P NMR (161 MHz,
4.7.5. Compound 3e. 71% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼55:45 in CDCl3):
d 1.12 (s, 18H), 1.17 (s, 18H),
1.21 (s, 18H), 1.22 (s, 18H), 3.82 (t, J¼9.2 Hz, 1H), 3.96 (t, J¼9.2 Hz,
1H), 4.43 (dd, J¼7.8,17.6 Hz,1H), 4.55 (dd, J¼7.8,17.6 Hz,1H), 5.21 (t,
J¼9.2 Hz,1H), 5.24 (t, J¼9.2 Hz,1H), 6.72 (dd, J¼3.2, 8.0 Hz, 2H), 6.91
(d, J¼3.2 Hz, 1H), 7.00–7.46 (m, 33H), 7.91 (dd, J¼1.6, 8.0 Hz, 1H),
CDCl3): d 28.46, 29.67. HRMS (Micromass LCT) calcd for C49H58NO2P
(MþH)þ: 724.4283; found: 724.4299.
4.6.6. Compound 8f. 96% yield, white foam. 1H NMR (400 MHz,
8.00 (dd, J¼1.6, 8.0 Hz, 1H). 31P NMR (161 MHz, CDCl3):
d
ꢁ9.35,
CDCl3) (major/minor¼66:34 in CDCl3):
d
1.27 (s, 18H), 1.32 (s, 18H),
ꢁ9.97. HRMS (Micromass LCT) calcd for C49H58NOP (MþH)þ:
1.33 (s, 18H), 1.34 (s, 18H), 3.60 (s, 3H), 3.65 (s, 3H), 3.66 (s, 3H), 3.66
(s, 3H), 3.83 (t, J¼8.8 Hz, 1H), 4.03 (t, J¼8.8 Hz, 1H), 4.60 (dd, J¼7.8,
17.6 Hz, 1H), 4.70 (dd, J¼7.8, 17.6 Hz, 1H), 5.15 (t, J¼9.2 Hz, 1H), 5.29
(t, J¼9.2 Hz, 1H), 7.04–7.56 (m, 32H), 7.70 (dd, J¼1.6, 8.0 Hz, 1H),
708.4334; found: 708.4344.
4.7.6. Compound 3f. 78% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼56:44 in CDCl3):
d 1.21 (s, 18H), 1.26 (s, 18H),
7.75 (dd, J¼1.6, 8.0 Hz, 1H). 31P NMR (161 MHz, CDCl3):
d
28.57,
1.29 (s, 18H), 1.30 (s, 18H), 3.63 (s, 3H), 3.64 (s, 3H), 3.65 (s, 3H), 3.66
(s, 3H), 3.83 (t, J¼8.8 Hz, 1H), 3.94 (t, J¼8.8 Hz, 1H), 4.43 (dd, J¼7.8,
17.6 Hz, 1H), 4.56 (dd, J¼7.8, 17.6 Hz, 1H), 5.21 (t, J¼9.2 Hz, 1H), 5.24
(t, J¼9.2 Hz, 1H), 6.68 (d, J¼3.2, 2H), 6.97–7.36 (m, 30H), 7.90 (dd,
J¼1.6, 8.0 Hz, 1H), 8.00 (dd, J¼1.6, 8.0 Hz, 1H). 31P NMR (161 MHz,
29.56. HRMS (Micromass LCT) calcd for C51H62NO4P (MþH)þ:
784.4495; found: 784.4489.
4.7. General procedure for the synthesis of compound 3
CDCl3):
d
ꢁ12.01, ꢁ12.07. HRMS (Micromass LCT) calcd for
HSiCl3 (4.2 mL, 39.6 mmol) was added to a solution of 8 (1.3 g,
1.98 mmol) and Et3N (9.4 mL, 39.6 mmol) in dried and degassed
toluene (25 mL) under nitrogen atmosphere, and the mixture was
heated under reflux overnight. After cooling to 0 ꢀC, 30% NaOH aq
(60 mL) was added, and the mixture was stirred at 60 ꢀC until the
organic and aqueous layers became clear. The organic product was
extracted with degassed EtOAc (3ꢂ30 mL), and the combined or-
ganic layer was washed with water (2ꢂ20 mL), brine successively
and dried over anhydrous Na2SO4. The organic layer was concen-
trated under reduced pressure. The residue was purified by flash
chromatography on silica gel eluting with EtOAc/hexane¼20:1 to
afford ligands 3.
C51H62NO3P (MþH)þ: 768.4546; found: 768.4537.
4.8. General procedure for the synthesis of complex 9
Ligand
3 (0.030 mmol) and complex [Pd(h
3-1,3-diphenyl-
allyl)Cl]2 (9) (0.017 mmol) were dissolved in CD2Cl2 (0.75 mL)
under N2. After stirring at rt for 30 min, the mixture was transferred
to NMR tube and analyzed by 1H NMR and 31P NMR.
4.8.1. Complex 9a. 1H NMR (400 MHz, CD2Cl2) (major/minor¼
54:46 in CD2Cl2):
d
0.08 (d, J¼6.9 Hz, 3H), 0.38 (d, J¼7.0 Hz, 3H), 0.51
(d, J¼7.0 Hz, 3H), 0.71 (d, J¼7.0 Hz, 3H), 1.40–1.50 (m, 1H), 1.77–1.86
(m, 1H), 2.38–2.48 (m, 1H), 3.34 (t, J¼9.4 Hz, 1H), 3.80–3.97 (m, 4H),
4.85 (d, J¼12.3 Hz, 1H), 4.94 (d, J¼10.9 Hz, 1H), 5.68–5.80 (m, 2H),
5.88 (d, J¼7.7 Hz, 1H), 5.91 (d, J¼8.0 Hz, 1H), 6.53–7.86 (m, 58H). 31P
4.7.1. Compound 3a. 67% yield, viscous oil. 1H NMR (400 MHz,
CDCl3) (major/minor¼52:48 in CDCl3): 0.79 (d, J¼6.6 Hz, 3H), 0.80
d
(d, J¼7.0 Hz, 3H), 0.81 (d, J¼7.0 Hz, 3H), 0.84 (d, J¼7.0 Hz, 3H), 1.52–
1.61 (m, 1H), 1.62–1.71 (m, 1H), 3.69 (t, J¼8.4 Hz, 1H), 3.80–3.90 (m,
3H), 4.01 (dd, J¼6.6, 8.1 Hz, 1H), 4.09 (dd, J¼8.4, 9.5 Hz, 1H), 6.87 (d,
J¼7.7 Hz, 1H), 6.89 (d, J¼7.7 Hz, 1H), 7.07–7.38 (m, 32H), 7.88 (dd,
J¼1.5, 7.7 Hz, 1H), 7.89 (dd, J¼1.5, 7.7 Hz, 1H). 31P NMR (161 MHz,
NMR (161 MHz, CD2Cl2): d 24.80, 28.80.
4.8.2. Complex 9b. 1H NMR (400 MHz, CD2Cl2) (major/minor¼58:42
in CD2Cl2):
d
0.43 (s, 9H), 0.64 (s, 9H), 2.2 (br s, 1H), 3.09 (t, J¼9.4 Hz,
3H), 3.68 (dd, J¼5.4, 10.5 Hz, 1H), 3.87 (dd, J¼9.1, 10.5 Hz, 1H), 3.96–
4.03 (m, 2H), 4.80 (d, J¼12.3 Hz, 1H), 4.94 (d, J¼11.2 Hz, 1H), 5.53
(t, J¼10.9 Hz, 1H), 5.83–5.93 (m, 3H), 6.54 (dd, J¼11.2, 13.1 Hz, 1H),
CDCl3):
found: 449.1905.
d
ꢁ14.87, ꢁ14.96. HRMS (EI) calcd for C30H28NOP: 449.1910;
6.58–7.87 (m, 55H). 31P NMR (161 MHz, CD2Cl2):
d 25.21, 29.10.
4.7.2. Compound 3b. 80% yield, viscous oil. 1H NMR (400 MHz,
CDCl3) (major/minor¼53:47 in CDCl3):
d
0.73 (s, 9H), 0.81 (s, 9H),
4.9. General procedure for palladium-catalyzed asymmetric
allylic alkylation
3.75–3.89 (m, 3H), 3.93–4.06 (m, 3H), 6.83 (d, J¼8.0 Hz,1H), 6.88 (d,
J¼8.0 Hz, 1H), 7.07–7.39 (m, 32H), 7.88 (dd, J¼1.5, 7.7 Hz, 1H), 7.89
(dd, J¼1.5, 7.7 Hz, 1H). 31P NMR (161 MHz, CDCl3):
d
ꢁ14.95, ꢁ15.02.
A mixture of ligand (30 mmol) and [Pd-(h
3-C3H5)Cl]2 (4.60 mg,
´
HRMS (EI) calcd for C31H30NOP: 463.2067; found: 463.2064.
12.5 ımol) in dry dichloromethane (1 mL) was stirred at room
temperature under nitrogen for 1 h, and the resulting green solu-
tion was added to a mixture of 1,3-diphenyl-2-propenyl acetate
4.7.3. Compound 3c. 77% yield, white foam. 1H NMR (400 MHz,
CDCl3) (major/minor¼51:49 in CDCl3):
d
3.39 (dd, J¼6.0, 11.2 Hz,
(0.252 g, 1.00 mmol) and lithium acetate (0.0020 g, 20 mmol) in dry

F. Tian et al. / Tetrahedron 65 (2009) 9609–9615
9615
Zhang, Y. J.; Dai, Y.; Zhang, J.; Zhang, W. TetrahedronLett. 2008, 49, 4106; (n)Zhang,
Y. J.; Wei, H.; Zhang, W. Tetrahedron 2009, 65, 1281.
4. For selected reviews: (a) Mikami, K.; Aikawa, K.; Yusa, Y.; Jodry, J.; Yamanaka,
M. Synlett 2002, 1561; (b) Dai, Y.; Yang, G.; Zhang, Y. J.; Wang, F.; Zhang, W. Chin.
J. Org. Chem. 2008, 28, 1169.
dichloromethane (2 mL) via a cannula, followed by the addition of
dimethyl malonate (0.396 g, 3.00 mmol) and BSA (0.613 g,
3.00 mmol). The reactions were carried out at room temperature
and monitored by TLC for the disappearance of 1,3-diphenyl-2-
propenyl acetate. Then the solvent was evaporated and the
resulting mixture was extracted with ether (20 mL). The extract
was washed twice with ice-cold saturated NH4Cl aqueous solution
(25 mL) and then dried over anhydrous Na2SO4. After removal
of the ether, the residue was purified on silica gel column chro-
matography with hexane/ethyl acetate (8:1) to afford pure product.
5. For selected reviews: (a) Bolm, C. Angew. Chem., Int. Ed. Engl. 1991, 30, 542;
(b) Pfaltz, A. Acc. Chem. Res. 1993, 26, 339; (c) Togni, A.; Venanzi, L. M. Angew.
Chem., Int. Ed. Engl. 1994, 33, 497; (d) Williams, J. M. J. Synlett 1996, 705;
(e) Ghosh, A. K.; Mathivanan, P.; Cappiello, J. Tetrahedron: Asymmetry 1998, 9, 1;
(f) Pfaltz, A. Synlett 1999, 835; (g) Rechavi, D.; Lemaire, M. Chem. Rev. 2002, 102,
3467; (h) Desimoni, G.; Faita, G.; Quadrelli, P. Chem. Rev. 2003, 103, 3119;
(i) McManus, H. A.; Guiry, P. J. Chem. Rev. 2004, 104, 4151; (j) Meyers, A. I. J. Org.
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6. (a) Imai, Y.; Zhang, W.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Tetrahedron Lett. 1997, 38,
2681; (b) Imai, Y.; Zhang, W.; Kida, T.; Nakatsuji, Y.; Ikeda, I. J. Org. Chem. 2000,
65, 3326; (c) Zhang, W.; Xie, F.; Matsuo, S.; Imahori, Y.; Kida, T.; Nakatsuji, Y.;
Ikeda, I. Tetrahedron: Asymmetry 2006, 17, 767; (d) Wang, F.; Zhang, Y. J.; Yang,
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Viscous oil. 1H NMR (400 MHz, CDCl3):
d 3.51 (s, 3H), 3.69 (s, 3H),
3.94 (d, J¼10.8 Hz, 1H), 4.25 (dd, J¼8.8, 10.8 Hz, 1H), 6.32 (dd, J¼8.4,
15.6 Hz, 1H), 6.46 (d, J¼15.6 Hz, 1H), 7.17–7.32 (m, 10H). The en-
antiomeric excess was determined by HPLC on a Chiralpak OD-H
column, hexane/2-propanol¼98:2, flow rate¼0.5 mL/min.
7. (a) VonMatt, P.; Pfaltz, A. Angew. Chem., Int. Ed. Engl. 1993, 32, 566; (b) Sprinz, J.;
Helmchen, G. Tetrahedron Lett. 1993, 34, 1769; (c) Dawson, G. L.; Frost, C. G.;
Williams, J. M. J.; Coote, S. J. Tetrahedron Lett. 1993, 34, 3149.
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This work was partially supported by the National Natural Sci-
ence Foundation of China (Grant No. 772081), Nippon Chemical
Industrial Co., Ltd. We thank Instrumental Analysis Center of
Shanghai Jiao Tong University for NMR analysis.
Supplementary data
Supplementary data associated with this article can be found in
online version, at doi:10.1016/j.tet.2009.09.053.
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