Synthesis of atropisomeric 5,5′-linked biphenyl bisaminophosphine ligands and their applications in asymmetric catalysis

Article abstract of DOI:10.1016/j.tet.2008.12.056

Atropisomeric 5,5′-linked biphenyl bisaminophosphine ligands 2 has been synthesized. The axial chirality of this type of ligands can be retained by macro-ring strain produced from 5,5′-linkage of biphenyl even without 6,6′-substituents on biphenyls. The Rh complex of bisaminophosphine 2a as a catalyst is effectively working in the asymmetric hydrogenation of methyl (Z)-2-acetamido-3-arylacrylates, however, for hydrogenation of arylenamide, the low enantioselectivity was observed. When the ligands applied to Pd-catalyzed allylic alkylation, it is found that ligand 2b having a longer backbone linkage is a better ligand for enantioselection in the reaction.

Full text of DOI:10.1016/j.tet.2008.12.056

Tetrahedron 65 (2009) 1281–1286
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Tetrahedron
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Synthesis of atropisomeric 5,50-linked biphenyl bisaminophosphine ligands
and their applications in asymmetric catalysis
,
Yong Jian Zhang a, Hao Wei b, Wanbin Zhang a
*
a School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
b Institute of Micro/Nano Science and 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
Atropisomeric 5,50-linked biphenyl bisaminophosphine ligands 2 has been synthesized. The axial chi-
rality of this type of ligands can be retained by macro-ring strain produced from 5,50-linkage of biphenyl
even without 6,60-substituents on biphenyls. The Rh complex of bisaminophosphine 2a as a catalyst is
effectively working in the asymmetric hydrogenation of methyl (Z)-2-acetamido-3-arylacrylates, how-
ever, for hydrogenation of arylenamide, the low enantioselectivity was observed. When the ligands
applied to Pd-catalyzed allylic alkylation, it is found that ligand 2b having a longer backbone linkage is
a better ligand for enantioselection in the reaction.
Article history:
Received 9 September 2008
Received in revised form 15 December 2008
Accepted 16 December 2008
Available online 24 December 2008
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
coordinating groups next to the axis, and the axial chirality of the
ligand can be retained by steric hindrance of two bulky co-
Chiral ligands have played a dominant role in the development
of efficient transition metal-catalyzed asymmetric reactions.
Thousands of chiral ligands have been developed and applied in
various catalytic asymmetric reactions to produce enantiomerically
pure compounds.1 Among them, atropisomeric biaryl ligands, such
as BINAP,2 BINOL,3 and boxax,4 have been explored as effective
skeletons for many transition metal-catalyzed asymmetric re-
actions.5 Encouraged by great success of axially chiral bisphosphine
ligand BINAP in asymmetric hydrogenation reactions, many
bisphosphine ligands supported by an atropisomeric scaffold have
been developed.5 It was found that modulation of the steric and
electronic properties of atropisomeric scaffold of the ligand could
remarkably influence on their efficiency in asymmetric catalytic
reactions. Recently, the steric design of the biaryl core has been
extensively explored such as BIPHEMP,6 MeO-BIPHEP,6 TunePhos,7
SEGPHOS,8 SYNPHOS,9 and DIFLUORPHOS.10 In Ru-catalyzed
ordinating groups and macro-ring strain produced from 5,50-link-
age of biphenyls even without 6,60-substituents. The modulation of
the length of the backbone carbon chain could control the confor-
mational flexibility of the metal chelate rings formed with atrop-
isomeric ligands to provide more suitable chiral environment for
asymmetric catalysis. In our initial study, we found that the
bisoxazolines13a and bismethylenephosphines13b with atropiso-
meric framework 1 are provided with stable axial chirality at
appropriate temperature, and they can be effectively applied in
Pd(II)-catalyzed asymmetric Wacker-type cyclization of 2-allyl-
phenols and Rh(I)-catalyzed asymmetric hydrogenation of dehy-
droamino acids, respectively.
Most effort on asymmetric catalysis has been focused on the use
of transition-metal catalysts containing chiral phosphine ligands
over the last three decades.1 Recently, it has been shown that some
of the results obtained with chiral phosphinite,14 phosphite,15
phosphonite16 or phosphoramidite17 ligand can match those
asymmetric hydrogenation of b-keto esters, it was demonstrated
that the ligand displayed a narrow dihedral angel of biaryl back-
bone showed better enantioselectivity.11 However, the better
enantioselectivity was obtained with increasing dihedral angel of
biaryl core in Pd-catalyzed asymmetric allylic alkylation.12 It is
obvious that subtle changes in steric property of chiral ligands can
lead to dramatic variations in efficiency for different asymmetric
reactions. Most recently, we developed novel atropisomeric
framework 1 (Fig. 1),13 in which the biphenyl has only two
O
O
H
H
L
L
L
L
H
H
(CH2)n
(CH2)n
O
O
1 (aR)
L = Coordination Group
Figure 1. Atropisomeric ligands with a 5,50-linkage of biphenyl.
1 (aS)
* Corresponding author. Tel./fax: þ86 21 5474 3265.
E-mail address: wanbin@sjtu.edu.cn (W. Zhang).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.12.056

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Y.J. Zhang et al. / Tetrahedron 65 (2009) 1281–1286
dehydroamino acid derivatives and arylenamide, and Pd-catalyzed
O
O
asymmetric allylic alkylation.
Bn
Bn
NHPPh2
N
Ph2P
N
PPh2
Ph2PHN
2. Results and discussion
O
Bisaminophosphine ligands 2 could be readily prepared from
2,20-dinitro-5,50-dimethoxybiphenyl (5) as illustrated in Scheme 1.
For synthesis of biphenyl compound 5, 3-bromoanisole (3) was
initially chosen as a starting material. Nitration of 3-bromoanisole
afforded a mixture of desired 3-bromo-4-nitroanisole (4) and
byproduct 5-bromo-2-nitroansole. Compound 4 can be isolated by
column chromatography in only 32% yield. Ullman coupling of 4
with activated copper powder furnished the biphenyl skeleton 5 in
78% yield. To more effectively prepare compound 5, the synthetic
route was modified from commercially available compound, 4-
methoxy-2-nitrobenzoic acid (6) as a starting material. Curtius
rearrangement of benzoic acid 6 furnished 5-methoxy-2-nitroani-
line (7) in 97% yield. Diazotization of compound 7 followed by io-
dination with potassium iodide gave 3-iodo-4-nitroanisole (8) (93%
yield), which was then converted to biphenyl compound 5 by Ull-
man coupling in 90% yield. Demethylation of 5 with aluminum
chloride and 1-dodecanethiol afforded biphenol compound 9 in
79% yield. Cyclization of biphenol 9 with 1,8-dibromooctane and
1,10-dibromodecane in the presence of potassium carbonate in
DMF led to the key intermediates 10a and 10b in 58% and 55%
yields, respectively. Straightforward reduction of 10a with Pd–C
under 5 atm of hydrogen gave quantitatively biphenyldiamine 11a.
Then, we tried optical resolution of biphenyldiamine 11a to obtain
optically pure diamine compound, however, all attempts in
H
H
NHPPh2
NHPPh2
NHPPh2
NHPPh2
(CH2)n
O
2
BDPAB
Figure 2. Bisaminophosphine ligands.
obtained by using phosphine ligands in catalytic asymmetric
hydrogenation. Chiral aminophosphines, which can easily synthe-
size from chiral amines, have been widely used as ligands in the
preparation of metallic complexes and application in catalytic
asymmetric reactions.18 Among them, the easily prepared C2-
symmetric bisaminophosphine ligands (Fig. 2) were also found to
be effective ligands for transition metal-catalyzed asymmetric
reactions.19 For example, bisaminophosphines (BDPAB) with
binaphthyl have effectively been applied in asymmetric hydroge-
nation of dehydroamino acid derivatives19b and enamides.19d
Herein we wish to report synthesis of novel bisaminophosphine
ligands with our atropisomeric framework 1, 2,20-bis(diphenyl-
phosphinoamino)-5,50-(polymethylenedioxy)-1,10-biphenyls 2,20
and their application in Rh-catalyzed asymmetric hydrogenation of
MeO
MeO
MeO
b
a
NO2
NO2
NO2
Br
Br
MeO
MeO
3
4
5
e
MeO
MeO
c
d
NO2
COOH
6
NO2
NO2
NH2
7
I
8
HO
O
O
g
f
h
NO2
NO2
H
H
NO2
NO2
H
H
NH2
NH2
(CH2)n
(CH2)n
5
HO
O
O
O
9
11a-b
10a, n = 8
10b, n = 10
i
O
H
O
j
NHPPh2
NHPPh2
H
H
NHPPh2
NHPPh2
H
H
NHPPh2
NHPPh2
+
(CH2)n
(CH2)n
(CH2)n
H
O
O
O
2a-b
(S)-2a n = 8
(S)-2b n = 10
(R)-2a n = 8
(R)-2b n = 10
Scheme 1. Reagents and conditions: (a) HNO3–H2SO4, 32%; (b) Cu, 78%; (c) (i) SOCl2, (ii) NaN3, (iii) AcOH, 97%; (d) 50% H2SO4, NaNO2, then KI, 93%; (e) Cu, 90%; (f) AlCl3, 1-do-
decanethiol, CH2Cl2, 79%; (g) Br(CH2)nBr, K2CO3, DMF; for 10a, 58%; for 10b, 55%; (h) H2, Pd–C, EtOAc; for 11a, 100%; for 11b, 99%; (i) ClPPh2, Et3N, CH2Cl2; for 2a, 81%; for 2b, 79%; (j)
chiral preparative HPLC, a Daicel Chiralcel AD-H column, for 2a, 42%; for 2b, 39%.

Y.J. Zhang et al. / Tetrahedron 65 (2009) 1281–1286
1283
resolution of 11a failed. The reaction of racemic biphenyldiamine
11a with chlorodiphenylphosphine in the presence of triethylamine
furnished racemic bisaminophosphine 2a in 81% yield. The optical
separation of racemic 2a by chiral preparative HPLC using a Daicel
Chiralcel AD-H column afforded, respectively, enantiomerically
pure (>99% ee) (þ)-2a and (ꢀ)-2a in 42% yield. In the same way, the
optically pure aminophosphine ligand 2b was prepared from 5,50-
decamethylenedioxy-biphenyl-2,20-dinitrate (10b) in 31% overall
yield. The sense of axial chirality of 2a was determined by the major
Cotton effects (CEs) in the CD spectra. The CD curve of (ꢀ)-2a dis-
played negative CE at 237.0 nm. This signed feature is the charac-
teristic of (R)-configuration at chiral axis, which was in contrast
with the spectra in the literature of axially chiral biphenyl
compounds.21
asymmetric hydrogenations of various methyl (Z)-2-acetamido-3-
arylacrylates 12 catalyzed by Rh(I)–(R)-2a complex. A variety of
substrates 12 can be hydrogenated to produce the corresponding a-
amino ester derivatives 13 in quantitative conversions with high
enantioselectivities (entries 10–16). The electronic and steric na-
ture of the phenyl ring of the substrate had a little influence on the
catalytic activity and enantioselectivity in the hydrogenation re-
actions (91.3–95.3% ee).
Inspired by initial success in hydrogenation reaction, our next
goal was to extend the scope of atropisomeric bisaminophosphine
ligands to arylenamide as a hydrogenated substrate.23 The hydro-
genation reaction of N-acetyl-a-phenylenamide (14) was catalyzed
by 1 mol % of the Rh(I)–(S)-2a complex generated in situ by mixing
Rh(COD)2BF4 with bisaminophosphine (S)-2a in methylene chlo-
ride at room temperature for 24 h. As shown in Table 2, it was found
that the reaction required correspondingly high hydrogen press to
accomplish well (entries 1–4), and low enatioselectivity (45.3% ee)
was obtained. Using decamethylenedioxy linked bisaminophos-
phine 2b as a ligand, the enantioselectivity was slightly decreased
(entry 4). Further optimization with varying reaction solvent, the
enantioselectivity could not be improved significantly (entries
6–9).
To evaluate the effectiveness of our atropisomeric bisamino-
phophine ligands 2 in catalytic asymmetric reactions, we first chose
Rh-catalyzed asymmetric hydrogenation of methyl (Z)-a-acet-
amidocinnamate (12a) as standard test reaction. The hydrogena-
tion reaction was catalyzed by 1 mol % of the Rh(I)–(R)-2a complex
generated in situ by mixing Rh(COD)2BF4 with bisaminophosphine
(R)-2a in methanol at room temperature. It was found that the
catalytic efficiency largely depended on the hydrogen pressure. As
shown in Table 1, the hydrogenation reaction showed higher cat-
alytic activity with enhancement of the hydrogen pressure (entries
1–4). The enantioselectivity also enhanced with the hydrogen
pressure increasing from 1 to 3 atm (from 91.4% to 92.1% ee, entries
1 and 2). However, further raising the hydrogen pressure, the
enantioselectivity remarkably decreased (entries 3 and 4). With
(R)-2b as a ligand, which had decamethylenedioxy bridge, the
enantioselectivity decreased to 87.1% ee under 3 atm of hydrogen
pressure (entry 5). It may demonstrate that the shorter 5,50-linkage
of the ligand backbone could improve conformational rigidity,
which may be beneficial to enantioselection for the hydrogenation
reaction. The reaction medium also affects the catalytic activity and
enantioselectivity in the hydrogenation reaction (entries 6–9). The
highest enantioselectivity (94.4% ee) was obtained in methylene
chloride under 3 atm of hydrogen pressure (entry 7). With opti-
mization reaction conditions in hands, we have performed
Finally, the atropisomeric bisaminophosphine ligands 2 were
applied in Pd-catalyzed asymmetric allylic alkylation, which is one
of the most important asymmetric C–C bond forming reactions.24
We chose the reaction of 1,3-diphenylpropenyl acetate 16 with
dimethyl malonate, the standard test reaction for asymmetric al-
lylic alkylation. Under the standard reaction conditions: catalyst
generated in situ by mixing 2.5 mol % of [Pd(h
3-C3H5)Cl]2 and
6.0 mol % of ligand (S)-2; a mixture of N,O-bis(trimethylsilyl)-
acetamide (BSA) and LiOAc in methylene chloride, the alkylated
product 17 was afforded in high yields (>95%). As shown in Table 3,
in contrast with hydrogenation reaction, the better enantiose-
lectivity was observed using ligand (S)-2b, which has longer
backbone linkage (entries 1 and 2). Indeed, it was found by Trost
and Van Vranken that Pd–bisphosphine catalyst having the larger
P–Pd–P bite angle lead to better enantioselectivity in asymmetric
allylic alkylation.25 It could be rationalized that, therefore, the
catalyst Pd–(S)-2b, which having a larger P–Pd–P bite angle com-
paring with that of Pd–(S)-2a due to its longer backbone linkage, is
conducive to enantioselection in alkylation reaction. The reaction
solvent also affects the enantioselectivity in the reaction (entries 2–
Table 1
Rh-catalyzed asymmetric hydrogenation of methyl (Z)-
bisaminophosphines (R)-2 as ligandsa
a
-acetamidocinnamate using
H2
NHAc
NHAc
R
Rh(COD)2BF4/(R)-2
R
COOMe
COOMe
rt, 20 h,
13
12
Table 2
Rh-catalyzed asymmetric hydrogenation of N-acetyl-
nophosphines (S)-2 as ligandsa
a
-phenylamide using bisami-
Entry
Ligand
12, R
H2 press (atm)
Solvent
Conv.b (%)
eec (%)
1
2
3
4
5
6
7
8
2a
2a
2a
2a
2b
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
2a
12a, H
12a, H
12a, H
12a, H
12a, H
12a, H
12a, H
12a, H
1
3
5
10
3
3
3
3
3
3
3
3
3
3
3
3
MeOH
MeOH
MeOH
MeOH
MeOH
IPA
85
99
91.4
92.1
83.8
84.3
87.1
92.4
94.1
94.4
84.0
94.4
95.3
95.1
94.3
93.4
92.1
91.3
Rh(COD)2BF4/(S)-2
NHAc
NHAc
100
100
100
100
100
100
91.7
100
100
100
100
100
100
100
rt, 24 h
15
14
Entry
Ligand
H2 press (atm)
Solvent
Conv.b (%)
eec (%)
THF
CH2Cl2
Acetone
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
1
2
3
4
5
6
7
8
9
2a
2a
2a
2a
2b
2a
2a
2a
2a
1
5
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
MeOH
IPA
69.4
86.9
97.1
100
100
100
100
100
100
44.7
43.2
45.3
39.1
43.9
41.7
43.1
48.7
33.2
9
12a, H
10
11
12
13
14
15
16
12b, p-Me
12c, p-OMe
12d, p-Cl
12e, p-F
12f, p-Br
12g, o-Cl
12h, m-Cl
10
40
10
10
10
10
10
THF
Acetone
a
a
All reactions were carried out at room temperature for 20 h. The catalyst was
All reactions were carried out at room temperature for 24 h. The catalyst was
prepared in situ from Rh(COD)2BF4 and ligand (substrate/Rh/ligand¼100:1:1.1).
prepared in situ from Rh(COD)2BF4 and ligand (substrate/Rh/ligand¼100:1:1.1).
b
b
Determined by 1H NMR analysis.
Determined by 1H NMR analysis.
c
c
The enantiomeric excesses were determined by chiral HPLC using a Daicel
The enantiomeric excesses were determined by chiral HPLC using a Daicel
Chiralcel OD-H column. The S absolute configurations were assigned by comparison
Chiralcel AD-H column. The R absolute configurations were assigned by comparison
of optical rotations with the known reported data.22
of optical rotations with the known reported data.23

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Y.J. Zhang et al. / Tetrahedron 65 (2009) 1281–1286
Table 3
4.2. 3-Bromo-4-nitroanisole (4)
Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylpropenyl acetate with
dimethyl malonatea
Concentrated sulfuric acid (4 mL) was added dropwise to nitric
acid (70%, 5 mL) at 0 ꢁC. To this cooled solution, 3-bromoanisole
(4.1 g, 21.8 mmol) was added dropwise. The reaction mixture was
then stirred at 40 ꢁC for 5 h. After cooling, the mixture was poured
into 100 mL of cooled water and extracted with ethyl acetate
(50 mLꢂ3). The organic layer was washed with brine, dried over
Na2SO4, and concentrated in vacuo. The crude product was purified
by column chromatography to give white solid 426 (1.6 g, 32%). Mp
H3COOC
COOCH3
OAc
Pd/(S)-2
+ H2C(CO2CH3)2
Ph
Ph
Base, 24 h, rt
Ph
Ph
16
17
Entry
Ligand
Solvent
Base/additive
eeb (%)
1
2
3
4
5
6
7
8
9
2a
2b
2b
2b
2b
2b
2b
2b
2b
CH2Cl2
CH2Cl2
THF
BSA/LiOAc
BSA/LiOAc
BSA/LiOAc
BSA/LiOAc
BSA/LiOAc
BSA/LiOAc
BSA/NaOAc
BSA/KOAc
NaH
54.1
58.4
61.7
34.7
51.9
52.8
53.3
55.6
51.4
43–45 ꢁC; 1H NMR (CDCl3, 400 MHz):
d 3.89 (3H, s), 6.91 (1H, dd,
J¼9.1, 2.7 Hz), 7.21 (1H, d, J¼2.7 Hz), 7.98 (1H, d, J¼9.1 Hz).
Toluene
DMF
Et2O
4.3. 5,50-Dimethoxy-2,20-dinitrobiphenyl (5)
THF
THF
THF
The mixture of compound 4 (13.2 g, 56.9 mmol) and activated
copper powder (18.2 g, 284.4 mmol) was stirred at 170 ꢁC for 12 h.
The residue was cooled, and CH2Cl2 (250 mL) was added. Filtered
and washed with CH2Cl2 (50 mLꢂ4) and the filtrate was concen-
trated. The obtained residue was recrystallized with acetonitrile to
give yellow solid 5 (6.8 g, 78%). Mp 142–144 ꢁC; 1H NMR (CDCl3,
a
Molecular ratio: [Pd(
h
3-C3H5)Cl]2/ligand/substrate/BSA/H2C(CO2Me)2¼2.5:6.0:
100:300:300. Reactions were conducted at room temperature. The catalyst was
prepared by mixing [Pd(h
3-C3H5)Cl]2 with ligands in solvent at room temperature
for 1 h before use. All reactions gave above 95% isolated yields.
The enantiomeric excesses were determined by chiral HPLC using a Daicel
Chiralcel OD-H column. The S absolute configurations were assigned by comparison
b
of optical rotations with the known reported data.26
400 MHz):
d
8.28 (d, J¼8.8 Hz, 2H), 7.00 (dd, J¼8.8, 2.8 Hz, 2H), 6.70
(d, J¼2.8 Hz, 2H), 3.90 (s, 6H); 13C NMR (100 MHz, CDCl3):
d 163.46,
140.17, 137.57, 127.60, 115.87, 113.45, 56.17. HRMS (Micromass LCT)
calcd for C14H13N2O6 (MþH)þ: 305.0774; found: 305.0779.
6). Highest enantioselectivity (61.7% ee) was obtained in THF (entry
3). The reaction enantioselectivities could not be improved by al-
tering other reaction parameters such as base or additive (entries
7–9).
4.4. 5-Methoxy-2-nitroaniline (7)
A solution of 5-methoxy-2-nitrobenzoic acid (5.0 g, 25.4 mmol)
and thionyl chloride (10 mL) in benzene (20 mL) was refluxed for
5 h. The solution was concentrated and then dissolved in acetone
(50 mL). A solution of NaN3 (10.0 g, 154.0 mmol) in water (30 mL)
was added dropwise at 0 ꢁC. The mixture was stirred at the same
temperature for 2 h, and poured into cooled water (300 mL) and
extracted with CH2Cl2 (100 mLꢂ4). The solvent was concentrated
and the obtained residue was dissolved in acetic acid (30 mL) and
water (10 mL). The reaction mixture was refluxed overnight. To this
mixture, saturated aqueous NaHCO3 (80 mL) was added dropwise
at room temperature and stirred for 1 h. The obtained precipitate
was filtered, and washed with water and dried under vacuum to
give 727 (4.1 g, 97%) as a yellow solid. Mp 128–130 ꢁC; 1H NMR
3. Conclusion
In summary, a new type of atropisomeric 5,50-linked biphenyl
bisaminophosphine ligands 2 has been synthesized. It was dem-
onstrated that the axial chirality of this type of ligands can be
retained by macro-ring strain produced from 5,50-linkage of bi-
phenyl. The Rh complex of bisaminophosphine 2a as a catalyst is
effectively working in the asymmetric hydrogenation of methyl (Z)-
2-acetamido-3-arylacrylates 12, however, for hydrogenation of
arylenamide, the low enantioselectivity was observed. When the
ligands applied to Pd-catalyzed allylic alkylation, it is found that
ligand 2b having a longer backbone linkage is a better ligand for
enantioselection in the reaction. Further study of development and
application of this type of atropisomeric ligands are in progress.
(CDCl3, 400 MHz):
d
8.07 (d, J¼9.5 Hz, 1H), 6.28 (dd, J¼9.5, 2.6 Hz,
1H), 6.21 (br s, 2H), 6.15 (d, J¼2.6 Hz, 1H), 3.83 (s, 3H).
4.5. 3-Iodo-4-nitroanisole (8)
4. Experimental
To a solution of 5-methoxy-2-nitroaniline (0.3 g, 1.8 mmol) in
sulfuric acid (50%, 10 mL), a solution of NaNO2 in concentrated
sulfuric acid (4 mL) was added at 0 ꢁC and stirred at the same
temperature for 2 h. The diazonium salt solution was added drop-
wise to an ice-water solution of KI (0.45 g, 2.7 mmol) at 0 ꢁC, and
the resulting mixture was stirred overnight. The solution was made
basic with NaOH (aq, 10%), and extracted with CH2Cl2 (30 mLꢂ3)
and washed with brine (50 mL). The organic layer was dried over
MgSO4, filtered, and the solvent was removed at reduced pressure
to give 828 (0.47 g, 93%) as a yellow solid. Mp 65 ꢁC; 1H NMR (CDCl3,
4.1. General experimental conditions
All air- and moisture-sensitive manipulations were carried out
with standard Schelenk techniques under nitrogen. The reaction
solvents were distilled prior to use (toluene and dichloromethane
were distilled from CaH2, THF was distilled from Na). The com-
mercially available reagents were used without further purification.
Column chromatography was run on silica gel (100–200 mesh).
Melting points are uncorrected. 1H NMR spectra and 13C NMR
spectra were recorded on a Varian MERCURY plus-400 spectro-
meter. The ee values were determined by HPLC using a Daicel
Chiralcel OD-H column and a Daicel Chiralpak AD-H column.
Optical rotation (concentration c given as g/100 mL) and CD spec-
trum were measured at the Shanghai Institute of Organic Chemis-
try, Chinese Academic of Science. Elemental analysis was
performed at the Instrumental Analysis Center of Shanghai Jiao
Tong University. HRMS was performed on a Micromass LCTTM at
the Analysis and Research Center of East China University of Science
and Technology.
400 MHz):
J¼9.0, 2.5 Hz, 1H), 3.85 (s, 3H).
d
7.96 (d, J¼9.0 Hz, 1H), 7.52 (d, J¼2.5 Hz, 1H), 6.97 (dd,
4.6. 5,50-Dihydroxy-2,20-dinitrobiphenyl (9)
A solution of compound 5 (6.8 g, 22.4 mmol) in CH2Cl2 (150 mL)
was added dropwise to the mixture prepared from 1-dodecanethiol
(54.3 g, 268.2 mmol) and aluminum trichloride (17.9 g,
134.1 mmol) in CH2Cl2 (150 mL) at room temperature. The mixture
was stirred overnight at room temperature, and then poured into

Y.J. Zhang et al. / Tetrahedron 65 (2009) 1281–1286
1285
ice-water, extracted with CH2Cl2. The organic layer was washed
4.11. 2,20-Bis(diphenylphosphinoamino)-5,50-
(octamethylenedioxy)-1,10-biphenyl (2a)
with water and brine, dried over MgSO4, and concentrated in vacuo.
Finally, the obtained residue was purified by column chromatog-
raphy (eluent: ethyl acetate and petroleum ether) to give brown
solid 9 (4.9 g, 79%). Mp 214–215 ꢁC; 1H NMR (DMSO-d6, 400 MHz):
Chlorodiphenylphosphine (3.0 mL, 16.8 mmol) and Et3N
(8.9 mL, 61.6 mmol) were added to a solution of compound 11a
(2.5 g, 7.7 mmol) in anhydrous CH2Cl2 (50 mL), and the mixture was
stirred for 24 h under reflux. The solution was cooled, concentrated
under reduced pressure, and EtOAc (50 mL) was added. The pre-
cipitate was filtered and washed with EtOAc (50 mL). The solvent
was removed in vacuo and the crude residue was purified by
chromatography on silica gel to give product 2a as a white solid
d
11.10 (s, 2H), 8.12 (d, J¼8.8 Hz, 2H), 6.93 (dd, J¼8.8, 2.4 Hz, 2H),
6.61 (d, J¼2.4 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d 163.25, 138.96,
138.20, 128.28, 117.53, 115.88. HRMS (Micromass LCT) calcd for
C12H9N2O6 (MþH)þ: 277.0461; found: 277.0470.
4.7. 2,20-Dinitro-5,50-(octamethylenedioxy)-1,10-
biphenyl (10a)
(4.3 g, 81%). Mp 217–218 ꢁC; 1H NMR (CDCl3, 400 MHz):
d 7.23 (m,
22H), 6.86 (dd, J¼8.8, 2.8 Hz, 2H), 6.75 (d, J¼9.2, 2.8 Hz, 2H), 4.55 (d,
JP–H¼6 Hz, 2H), 4.20 (m, 2H), 4.05 (m, 2H), 1.89 (m, 2H), 1.62 (m,
To a suspension of anhydrous potassium carbonate (12.3 g,
88.7 mmol) in DMF (100 mL), a solution of compound 9 (4.9 g,
17.7 mmol) and 1,8-dibromooctane (4.8 g, 17.7 mmol) in DMF
(50 mL) was added dropwise at 80 ꢁC for 5 h. The mixture was
stirred further at 80 ꢁC for 24 h. The reaction mixture was filtered,
and the filtrate was concentrated in vacuo. The resulting residue
was dissolved in CH2Cl2 (50 mL), washed with water and brine,
dried over MgSO4, concentrated in vacuo, then purified by chro-
matography on silica gel to give product 10a as a brown solid (4.0 g,
2H), 1.48–1.29 (m, 8H); 13C NMR (100 MHz, CDCl3):
d 152.33, 137.55,
137.40, 131.34, 131.13, 130.88, 130.67, 128.91, 128.89, 128.54, 128.49,
128.47, 128.43, 119.08, 118.74, 118.55, 116.15, 67.16, 28.32, 27.99,
24.95; 31P NMR (CDCl3, 161 MHz)
d 34.27. HRMS (Micromass LCT)
calcd for C44H43N2O2P2 (MþH)þ: 693.2800; found: 693.2808.
4.12. (R)-(L)-2,20-Bis(diphenylphosphinoamino)-5,50-
(octamethylenedioxy)-1,10-biphenyl [(R)-(L)-2a]
58%). Mp 192–196 ꢁC; 1H NMR (CDCl3, 400 MHz):
d 8.22 (d,
25
[
a
]
ꢀ32.8 (c 1, CHCl3); all other analytical data were identical
D
J¼9.2 Hz, 2H), 7.00 (dd, J¼9.2, 2.8 Hz, 2H), 6.75 (d, J¼2.8 Hz, 2H),
to those of 2a.
4.39 (m, 2H), 4.20 (m, 2H), 1.95 (m, 2H), 1.64 (m, 2H), 1.42–1.30 (m,
8H); 13C NMR (100 MHz, CDCl3):
d 163.10, 139.73, 138.16, 127.53,
4.13. (S)-(D)-2,20-Bis(diphenylphosphinoamino)-5,50-
(octamethylenedioxy)-1,10-biphenyl [(S)-(D)-2a]
118.05, 113.36, 66.73, 28.78, 28.62, 24.76. HRMS (Micromass LCT)
calcd for C20H23N2O6 (MþH)þ: 387.1556; found: 387.1558.
25
[
a
]
þ31.9 (c 1, CHCl3); all other analytical data were identical to
D
4.8. 2,20-Dinitro-5,50-(decamethylenedioxy)-1,10-
biphenyl (10b)
those of 2a.
4.14. 2,20-Bis(diphenylphosphinoamino)-5,50-
(decamethylenedioxy)-1,10-biphenyl (2b)
Product 10b was obtained as a brown solid in 55% yield fol-
lowing the procedure for synthesis of 10a. Mp 153–156 ꢁC; 1H NMR
(CDCl3, 400 MHz):
d
8.19 (d, J¼9.6 Hz, 2H), 6.96 (dd, J¼9.6, 2.0 Hz,
Product 2b was obtained as a white solid in 79% yield following
2H), 6.71 (d, J¼2.0 Hz, 2H), 4.23 (m, 2H), 4.13 (m, 2H), 1.81 (m, 2H),
the procedure for synthesis of 2a. 1H NMR (CDCl3, 400 MHz):
d 7.25
1.66 (m, 2H), 1.36–1.24 (m, 12H); 13C NMR (100 MHz, CDCl3):
(m, 22H), 6.87 (dd, J¼8.8, 2.8 Hz, 2H), 6.73 (d, J¼9.2, 2.8 Hz, 2H),
4.44 (d, JP–H¼6.4 Hz, 2H), 4.12 (m, 2H), 4.00 (m, 2H), 1.85 (m, 2H),
1.61 (m, 2H), 1.41–1.29 (m, 12H); 13C NMR (100 MHz, CDCl3):
d
162.74, 139.50, 137.91, 127.28, 115.69, 115.55, 68.71, 28.48, 28.36,
27.32, 24.91. HRMS (Micromass LCT) calcd for C22H27N2O6 (MþH)þ:
415.1869; found: 415.1870.
d
152.44, 137.98, 137.80, 131.14, 130.93, 130.91, 130.71, 128.93,
128.85, 128.52, 128.45, 118.36, 118.07, 117.87, 117.10, 68.96, 28.71,
4.9. 2,20-Diamino-5,50-(octamethylenedioxy)-1,10-
biphenyl (11a)
28.65, 28.02, 25.10; 31P NMR (CDCl3, 161 MHz):
d 32.86. HRMS
(Micromass LCT) calcd for C46H47N2O2P2 (MþH)þ: 721.3113; found:
721.3152.
The mixture of compound 10a (3.4 g, 8.8 mmol) and Pd (10% on
carbon, 0.4 g) was suspended in ethyl acetate (50 mL), and was
stirred at room temperature under H2 (5 atm) for 12 h. The solution
was filtered through a bed of Celite to remove the catalyst and the
filtrate was evaporated to dryness to afford product 11a (2.9 g,
4.15. (R)-(L)-2,20-Bis(diphenylphosphinoamino)-5,50-
(decamethylenedioxy)-1,10-biphenyl [(R)-(L)-2b]
25
[
a
]
ꢀ37.5 (c 1, CHCl3); all other analytical data were identical to
D
100%). Mp 161–163 ꢁC; 1H NMR (CDCl3, 400 MHz):
d
6.82–6.75 (m,
6H), 4.20 (m, 2H), 4.00 (m, 2H), 1.89 (m, 2H), 1.62 (m, 2H), 1.52–1.32
(m, 8H); 13C NMR (100 MHz, CDCl3):
151.81, 137.12, 126.51, 118.99,
those of 2b.
4.16. (S)-(D)-2,20-Bis(diphenylphosphinoamino)-5,50-
(decamethylenedioxy)-1,10-biphenyl [(S)-(D)-2b]
d
118.09, 116.69, 67.72, 28.77, 27.85, 24.90. HRMS (Micromass LCT)
calcd for C20H27N2O2 (MþH)þ: 327.2073; found: 327.2074.
25
[
a
]
þ39.7 (c 1, CHCl3); all other analytical data were identical
D
4.10. 2,20-Diamino-5,50-(decamethylenedioxy)-1,10-
biphenyl (11b)
to those of 2b.
4.17. General procedure for Rh(I)-catalyzed asymmetric
Product 11b was obtained in 99% yield following the procedure
for synthesis of 11a. Mp 138–139 ꢁC; 1H NMR (CDCl3, 400 MHz):
hydrogenation (Z)-acetamido-3-arylacrylic acid derivatives
d
6.81–6.69 (m, 6H), 4.14 (m, 2H), 3.97 (m, 2H),1.82 (m, 2H),1.63 (m,
[Rh(COD)2]BF4 (0.01 mmol) and (R)-2a (0.012 mmol) were dis-
solved in degassed MeOH (2 mL) and stirred for 30 min to form
a solution of [Rh(COD)(R)-2a]BF4 catalyst for the asymmetric
hydrogenation. Then a solution of substrate (1 mmol) in MeOH
(2 mL) was added to a catalyst solution prepared above. The
2H), 1.43–1.24 (m, 12H); 13C NMR (100 MHz, CDCl3):
d
151.89,
137.53, 126.37, 117.94, 117.76, 117.44, 69.22, 28.65, 28.44, 28.01,
25.18. HRMS (Micromass LCT) calcd for C22H30N2O2: 354.2307;
found: 354.2307.

1286
Y.J. Zhang et al. / Tetrahedron 65 (2009) 1281–1286
Chan, S.-S.; Chan, A. S. C. Adv. Synth. Catal. 2003, 345, 537; (d) Shimizu, H.;
Nagasaki, I.; Saito, T. Tetrahedron 2005, 61, 5405.
hydrogenation was performed in stainless steel autoclave at room
temperature under 3 atm of hydrogen for 20 h. The resulting so-
lution was passed through a short silica gel column to remove the
catalyst. The ee value and conversion of the product were measured
by chiral HPLC and 1H NMR spectroscopy without any further pu-
rification. The products of (Z)-acetamido-3-arylacrylic acid were
converted to corresponding methyl ester for the determination of
their ee value using chiral HPLC (a Daicel Chiralcel OD-H column,
flow rate¼0.5 mL/min, hexane/2-propanol (75:25), UV detector,
254 nm: tR (R)¼10.45 min, tR (S)¼12.31 min).
6. (a) Schmid, R.; Cereghetti, M.; Heiser, B.; Scho¨nholzer, P.; Hansen, H.-J. Helv.
Chim. Acta 1988, 71, 897; (b) Schmid, R.; Foricher, J.; Cereghetti, M.; Scho¨nho-
izer, P. Helv. Chim. Acta 1991, 74, 370; (c) Schmid, R.; Broger, E. A.; Cereghetti,
M.; Crameri, Y.; Foricher, J.; Lalonde, M.; Mu¨ller, R. K.; Scalone, M.; Schoettel, G.;
Zutter, U. Pure Appl. Chem. 1996, 68, 131.
7. Zhang, Z.; Qian, H.; Longmire, J.; Zhang, X. J. Org. Chem. 2000, 65, 6223.
8. Saito, T.; Yokozawa, T.; Ishizaki, T.; Moroi, T.; Sayo, N.; Miura, T.; Kumobayashi,
H. Adv. Synth. Catal. 2001, 343, 264.
9. (a) Pai, C. C.; Li, Y. M.; Zhou, Z. Y.; Chan, A. S. C. Tetrahedron Lett. 2002, 43, 2789;
(b) Paule, S.; Jeulin, S.; Ratovelomanana-Vidal, V.; Geneˆt, J. P.; Champion, N.;
Dellis, P. Eur. J. Org. Chem. 2003, 1931.
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10. Jeulin, S.; Paule, S.; Ratovelomanana-Vidal, V.; Genet, J. P.; Champion, N.; Dellis,
P. Angew. Chem., Int. Ed. 2004, 43, 320.
4.18. General procedure for Rh(I)-catalyzed asymmetric
hydrogenation arylenamides
ˆ
11. Genet, J.-P. Acc. Chem. Res. 2003, 36, 908.
12. Raghunath, M.; Zhang, X. Tetrahedron Lett. 2005, 46, 8213.
13. (a) Wang, F.; Zhang, Y. J.; Wei, H.; Zhang, J.; Zhang, W. Tetrahedron Lett. 2007, 48,
4083; (b) Wei, H.; Zhang, Y. J.; Wang, F.; Zhang, W. Tetrahedron: Asymmetry
2008, 19, 482.
14. (a) For review, see: Agbossou-Niedercorn, F.; Suisse, I. Coord. Chem. Rev. 2003,
242, 145; For recent examples, see: (b) Lam, K. H.; Xu, L.; Feng, L.; Fan, Q.-H.;
Lam, F. L.; Lo, W.-H.; Chan, A. S. C. Adv. Synth. Catal. 2005, 347, 1755; (c) Zhou,
Y.-G.; Tang, W.; Wang, W.-B.; Li, W.; Zhang, X. J. Am. Chem. Soc. 2002, 124, 4953;
(d) Chan, A. S. C.; Hu, W. H.; Pai, C. C.; Lau, C. P.; Jiang, Y. Y.; Mi, A. Q.; Yan, M.;
Sun, J.; Lou, R. L.; Deng, J. G. J. Am. Chem. Soc. 1997, 119, 9570.
15. For recent examples, see: (a) Huang, H.; Liu, X.; Chen, H.; Zheng, Z. Tetrahedron:
Asymmetry 2005, 16, 693; (b) Hua, Z.; Vassar, V. C.; Ojima, I. Org. Lett. 2003, 5,
3831; (c) Hannen, P.; Militzer, H.-C.; Vogl, E. M.; Rampf, F. A. Chem. Commun.
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Reetz, M. T.; Neugebauer, T. Angew. Chem., Int. Ed. 1999, 38, 179.
16. For recent examples, see: (a) Gridnev, I. D.; Fan, C.; Pringle, P. G. Chem. Commun.
2007, 1319; (b) Hou, G.-H.; Xie, J.-H.; Wang, L.-X.; Zhou, Q.-L. J. Am.
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[Rh(COD)2]BF4 (0.01 mmol) and (R)-2a (0.012 mmol) were dis-
solved in degassed MeOH (2 mL) and stirred for 30 min to form
a solution of [Rh(COD)(R)-2a]BF4 catalyst for the asymmetric hy-
drogenation. Then a solution of substrate (1 mmol) in MeOH (2 mL)
was added to a catalyst solution prepared above. The hydrogena-
tion was performed in stainless steel autoclave at room tempera-
ture under 3 atm of hydrogen for 24 h. The resulting solution was
passed through a short silica gel column to remove the catalyst. The
ee value and conversion of the product were measured by chiral
HPLC and 1H NMR spectroscopy without any further purification.
The products ee value using chiral HPLC (a Daicel Chiralcel AD-H
column, flow rate¼0.5 mL/min, hexane/2-propanol (90:10), UV
detector, 254 nm: tR (S)¼10.45 min, tR (R)¼12.91 min).
4.19. General procedure for the palladium-catalyzed allylic
alkylation of 1,3-diphenyl-2-propen-1-yl acetate
17. (a) For review, see: Minnaard, A. J.; Feringa, B. L.; Lefort, L.; de Vries, J. G. Acc.
Chem. Res. 2007, 40, 1267; For recent examples, see: (b) Huo, X.-H.; Xie, J.-H.;
Wang, Q.-S.; Zhou, Q.-L. Adv. Synth. Catal. 2007, 349, 2477; (c) Giacomina, F.;
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Asymmetry 2003, 14, 2687; (g) Pena, D.; Minnaard, A. J.; de Vries, J. G.; Feringa,
B. L. J. Am. Chem. Soc. 2002, 124, 14552; (h) Hu, A.-G.; Fu, Y.; Xie, J.-H.; Zhou, H.;
Wang, L.-X.; Zhou, Q.-L. Angew. Chem., Int. Ed. 2002, 41, 2348.
[Pd(h mmol) and (S)-2 (60 mmol) were dis-
3-C3H5)Cl]2 (25.0
solved in degassed CH2Cl2 (2 mL) and stirred for 60 min to form
a solution of [Pd–(S)-2] catalyst for allylic alkylation. Then a solu-
tion of substrate (1 mmol) and LiOAc (20 mmol) in CH2Cl2 (2 mL)
added a catalyst solution prepared above. Then added 1,3-diphenyl-
2-propen-1-yl acetate (3.00 mmol) and BSA (3.00 mmol). The re-
action was conducted under nitrogen in solvent at room temper-
ature for 24 h. The resulting solution was passed through a silica gel
column to calculate yield. The ee value of the product was mea-
sured by chiral HPLC (a Daicel Chiralcel OD-H column, flow
rate¼0.5 mL/min, hexane/2-propanol (98:2), UV detector, 254 nm:
tR (R)¼20.31 min, tR (S)¼21.78 min).
18. For recent reviews, see: (a) Bento-Garagorri, D.; Kirchner, K. Acc. Chem. Res.
2008, 41, 201; (b) Alajarı´n, M.; Lo´pez-Leonardo, C.; Llamas-Lorente, P. Top. Curr.
Chem. 2005, 250, 77.
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Acknowledgements
This work was supported by the National Natural Science
Foundation of China (grant nos. 20572070 and 20502015), and
Nippon Chemical Industrial Co., Ltd.
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