From tropos to atropos: 5,5′-bridged 2,2′-bis(diphenylphosphino)biphenyls as chiral ligands for highly enantioselective palladium-catalyzed hydrogenation of α-phthalimide ketones

Article abstract of DOI:10.1016/j.tetlet.2010.02.055

A class of atropisomeric diphosphine ligands with a wide range of dihedral angles has been developed. X-ray study of the Pd(II) complexes of these ligands showed that as the bridge length increased, the dihedral angles and the ligand bite angles increased

Full text of DOI:10.1016/j.tetlet.2010.02.055

Tetrahedron Letters 51 (2010) 2044–2047
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Tetrahedron Letters
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From tropos to atropos: 5,50-bridged 2,20-bis(diphenylphosphino)biphenyls
as chiral ligands for highly enantioselective palladium-catalyzed
hydrogenation of a-phthalimide ketones
*
Changqing Wang, Guoqiang Yang, Jing Zhuang, 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:
A class of atropisomeric diphosphine ligands with a wide range of dihedral angles has been developed.
X-ray study of the Pd(II) complexes of these ligands showed that as the bridge length increased, the dihe-
dral angles and the ligand bite angles increased as well, while an excessive increase in bridge length had a
reverse effect. It was found that there was a correlation between the ligand dihedral angles and the
Received 5 January 2010
Revised 7 February 2010
Accepted 10 February 2010
Available online 13 February 2010
enantioselectivity in Pd-catalyzed asymmetric hydrogenation of
enantioselectivities of up to 99% ee were afforded.
a-phthalimide ketones, and excellent
Ó 2010 Elsevier Ltd. All rights reserved.
Atropisomeric diphosphines are well-known versatile and
indispensable chiral inducers in many enantioselective transfor-
mations.1 Since the development of BINAP,2 many excellent chelat-
ing diphosphines with an atropisomeric biaryl scaffold, such as
MeO-BIPHEP,3 SEGPHOS,1d,4 TunePhos,5 and P-Phos,1e,6 have been
reported. The structural variations of the biaryl backbone are
responsible for the wide diversity of atropisomeric diphosphines.
Despite the extensive design of the biaryl core, the existing atrop-
isomeric biaryl diphosphine ligands possess at least one ortho
substituent at the biaryl skeleton,1f,h and if the substituent is too
small, the ligands become tropos due to the free rotation around
the axis. It is considered that such tropos diphosphine ligands as
dihedral angle can have a significant effect on the reactivity and
selectivity of the reactions. As a result, excellent ligands with high
reactivity and enantioselectivity for particular substrates could be
developed. Moreover, as each of the ligands 1 is restricted by a
bridge with variable length, this new class of ligands should be ri-
gid and have tunable bite angles. These properties provide us a
golden opportunity to study systematically the influence of the
dihedral angle of atropisomeric diphosphines on the reactivity
and selectivity of asymmetric reactions.
Our synthetic approach to enantiopure (R)- and (S)-5,50-alkyldi-
oxy-2,20-bis(diphenylphosphino)biphenyls (1a–e) is depicted in
Scheme 1. Bromination of the commercially available 4-methoxy-
phenol with Br2 furnished 2. Reaction of 2 with (CF3SO2)2O in the
presence of pyridine gave its triflate derivative 3 almost quantita-
tively. Phosphine oxide 4 was obtained by phosphinylation of tri-
flate 3 with the aid of a Pd catalyst. The bis(diphenylphosphine
oxide) 5 was obtained via Ullmann coupling of the phosphine oxide
4. Reaction of 5 with BBr3 provided 6 in high yield. Treatment of 6
with alkyl dihalides in the presence of excess anhydrous K2CO3 in
DMF furnished 7a–e in good yields. The optical resolution of (RS)-
7a–e was by chiral preparative HPLC using Daicel Chiracel AD-H
2,20-bis(diphenylphosphino) biphenyl (BIPHEP) can provide
a
wider range of dihedral angles than atropisomeric ligands due to
the minimal steric hindrance of the ortho hydrogen atoms. In view
of the significant influence of dihedral angles on asymmetric con-
trol,3–7 it is conceptually interesting to design and synthesize a
class of atropisomeric diphosphine ligands while maintaining the
small size of the ortho substituents, as it may ideally provide a
wide range of dihedral angles. To our knowledge, such a class of
ligands remains unexplored in the course of development of atrop-
isomeric diphosphines.
As part of our continued efforts to design new axial chiral ligand
scaffolds,8 we herein present a novel class of diphosphine ligands 1
(Fig. 1), in which the tropos BIPHEP is restricted by a bridge with
variable length at 5,50-positions. Ligands 1 are expected to provide
a wide range of dihedral angles due to the lack of substituents at
6,60-positions. It is well known that a subtle variation of the ligand
O
O
H
H
PPh2
PPh2
H
n H
PPh2
PPh2
PPh2
PPh2
H
H
(CH2)
(CH2)n
O
O
BIPHEP
1
1
(S)
(R)
Tropos
Atropos
* Corresponding author. Tel./fax: +86 21 5474 3265.
E-mail address: wanbin@sjtu.edu.cn (W. Zhang).
Figure 1. Atropisomeric ligands with a bridge across the 5,50-positions of the
biphenyl.
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.02.055

C. Wang et al. / Tetrahedron Letters 51 (2010) 2044–2047
2045
OH
OH
OTf
P(O)Ph2
Br
Br
Br
a
c
b
91%
99%
74%
OMe
OMe
OMe
OMe
2
3
4
MeO
HO
O
O
O
O
PPh2
PPh2
PPh2
PPh2
O
PPh2
PPh2
O
d
e
f
(CH2)n
98%
96%
O
MeO
HO
O
5
6
7a-e
a: n=7 57%
b: n=8 67%
c: n=9 69%
d: n=10 68%
e: n=12 64%
O
O
O
PPh2
PPh2
PPh2
PPh2
O
(CH2)n
(CH2)n
a: n=7 81%
b: n=8 84%
c: n=9 84%
d: n=10 86%
e: n=12 82%
O
O
O
-7a-e
-1a-e
(R)
(R)
g
h
90-95%
O
O
PPh2
PPh2
O
PPh2
PPh2
a: n=7 80%
b: n=8 85%
c: n=9 83%
d: n=10 84%
(CH2)n
(CH2)n
O
O
(S)-7a-e
(S)-1a-e e: n=12 83%
Figure 2. Crystal structures of PdCl2 complexes 8b–e.
a Br2, CH2Cl2. b Tf2O, Py, CH 2Cl2. c Ph2P(O)H, Pd2(dba)3.CHCl3, dppp, DIPEA, PhMe.
d
Cu, DMF. e BBr3, CH2Cl2. f Br(CH2)nBr, K2CO3, DMF. g Prep. Chromatogr. h HSiCl3,
PhNMe2, PhMe.
[(S)-4e]). This is the first study of a series of diphosphine com-
plexes with tunable dihedral angles by X-ray crystal structure
analysis.
Scheme 1. Synthesis of ligands.
Chiral amino alcohols are important compounds as biologically
active molecules and as chiral auxiliaries. Consequently, much ef-
fort has been devoted to the development of efficient methods
for the asymmetric synthesis of this structural motif.12 High
enantioselectivity has been achieved via the key step of Ru-cata-
Column in about 90% yield based on (RS)-7a–e. The target diphos-
phine ligands (R)1a–e and (S)1a–e were easily obtained by the
reduction of their resolved oxides 7a–e with an excess of HSiCl3
in 80–86% yields.9 Noteworthy is the fact that no racemization of
these diphosphines took place even after refluxing in toluene un-
der N2 for 12 h.
To understand the effects of the variable bridge length on metal
coordination and ligand performance in catalysis, the newly syn-
thesized ligands were reacted with a stoichiometric amount of
PdCl2(CH3CN)2 to afford the corresponding palladium dichloride
adducts (Table 1). X-ray crystal structure analysis of (R)-8b, (R)-
8c, (S)-8d, and (S)-8e allowed for a direct comparison with the
known BINAP structure (Fig. 2).10,11 As expected, (R)-8b has almost
the narrowest dihedral angle (59.7°), followed by (R)-8c (64.1°)
and (S)-8d (72.4°). These results are in agreement with our hypoth-
esis. Directly related to these are the ligand bite angles (\P–Pd–P):
91.8° [(R)-4b], 92.8° [(R)-4c], and 95.3° [(S)-4d]. Interestingly, the
further increase of the length of the bridges led to the decrease
of the dihedral angle (65.0° [(S)-4e]) and the bite angle (92.2°
lyzed asymmetric hydrogenation of a
-phthalimide ketones.13 Zhou
and co-workers have recently reported a method for the synthesis
of chiral amino alcohols using homogeneous palladium catalysts,
where up to 92.2% ee was achieved.14 To demonstrate the asym-
metric induction efficiency of chiral ligands 1a–e, the Pd-catalyzed
asymmetric hydrogenation of N-phenacyl-phthalimide (9a) was
employed as a model reaction. Initially, we carried out several
experiments employing a Pd(CF3CO2)2/(R)-1d system in 2,2,2-tri-
fluoroethanol (TFE) to screen optimal conditions for hydrogena-
tion.
A dramatical increase of enantioselectivity upon the
hydrogenation of 9a was observed as increase in H2 pressure
and reaction temperature. For example, 53% ee was obtained
under 35 atm of H2 at room temperature, while up to 98% ee
with more than 99% conversion was observed when high hydro-
gen pressure (100 atm) and high temperature (80 °C) were em-
ployed (Table 2, entry 4). However, by further increasing the
temperature, the enantioselectivity dropped slightly to 96% ee
(entry 5). The effect of solvent was also investigated. As re-
ported by Zhou and co-workers, this reaction was strongly sol-
vent-dependent and only TFE was the most effective in terms
of the conversion and enantioselectivity. Dichloromethane and
other solvents such as acetone, toluene, methanol, ethanol, 2-
propanol, and THF led to low activity.
Under the optimized conditions, ligands (R)-1a–e were em-
ployed to test the effect of the dihedral angle of the chiral biaryl li-
gands on the enantioselectivity of the reaction. The obtained
enantioselectivities were particularly interesting (Table 2, entries
6–9): as the dihedral angles increased, the best result was observed
when (R)-1d was used (98% ee), while the enantioselectivity was
the lowest (90% ee) with (R)-1e.
Table 1
Structural parameters for PdCl2 complexes
O
O
Ph2
P
Cl
Cl
PPh2
PPh2
PdCl2(CH3CN)2
(CH2)n
(CH2)n
Pd
P
(
R
)-8b
)-8c
(R)-1b
Ph2
(
R
(R)-1c
(S)-1d
(S)-1e
O
O
(
S
)-8d
)-8e
(
S
Entry
Phosphine
Dihedral angle (°)
Bite angle (°)
1
2
3
4
5
BINAP
68.4
59.7
64.1
72.4
65.0
92.8
91.8
92.8
95.3
92.2
(R)-1b (n = 8)
(R)-1c (n = 9)
(S)-1d (n = 10)
(S)-1e (n = 12)
With the optimized ligand and reaction conditions, other
a-phthalimide ketones including an alkyl ketone were examined

2046
C. Wang et al. / Tetrahedron Letters 51 (2010) 2044–2047
Table 2
tivities when utilized in the Pd-catalyzed asymmetric hydrogena-
tion of -phthalimide ketones.
Optimization of reaction conditions for Pd-catalyzed hydrogenation of N-phenacyl-
a
phthalimidea
Acknowledgments
O
O
HO
O
Catalyst
solv.
Ph
Ph
N
N
This work was supported by the National Natural Science Foun-
dation of China (No. 20772081), Science and Technology Commis-
sion of Shanghai Municipality (Nos. 08431901700, 09JC1407800),
and Nippon Chemical Industrial Co., Ltd. We thank Prof. Tsuneo
Imamoto for helpful discussion.
Temp.
H2,24h
O
O
9a
10a
Entry
Ligand
Temp. (°C)
H2 (atm)
Conv.b (%)
eec (%)
1
2
3
4
5
6
7
8
9
(R)-1d
(R)-1d
(R)-1d
(R)-1d
(R)-1d
(R)-1a
(R)-1b
(R)-1c
(R)-1e
rt
rt
35
70
70
100
100
100
100
100
100
34
51
83
>99
>99
>99
>99
>99
>99
53
67
81
98
96
93
96
97
90
References and notes
50
80
90
80
80
80
80
1. (a) For representative reviews, see: Asymmetric Catalysis in Organic Synthesis;
Noyori, R., Ed.; Wiley: New York, 1994; (b) Comprehensive Asymmetric Catalysis
I–III; Jacobson, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer: New York, 1999;
(c) Principles and Applications of Asymmetric Synthesis; Lin, G.-Q., Li, Y.-M., Chan,
A. S. C., Eds.; Wiley: New York, 2001; (d) Shimizu, H.; Nagasaki, I.; Saito, T.. In
Phosphorus Ligands in Asymmetric Catalysis; Börner, A., Ed.; Wiley-VCH:
Weinhem, 2008; Vol. 1, pp 207–260; (e) Li, Y.-M.; Yu, W.-Y.; Chan, A. S. C.. In
Phosphorus Ligands in Asymmetric Catalysis; Börner, A., Ed.; Wiley-VCH:
Weinhem, 2008; Vol. 1, pp 260–283; (f) Otero, I.; Börner, A.. In Phosphorus
Ligands in Asymmetric Catalysis; Börner, A., Ed.; Wiley-VCH: Weinhem, 2008;
Vol. 1, pp 307–329; (g) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40,
40; (h) Tang, W.; Zhang, X. Chem. Rev. 2003, 103, 3029; (i) Shimizu, H.;
Nagasaki, I.; Saito, T. Tetrahedron 2005, 61, 5405.
a
b
C
Reaction conditions: Pd(CF3CO2)2 2.0 mol %, (R)-1 2.4 mol %.
Determined by 1H NMR analysis of the crude products.
The enantiomeric excesses were determined by chiral HPLC using a Daicel
Chiralcel OJ-H column. The R absolute configurations were assigned by comparison
of optical rotations with the literature data.13
2. (a) Miyashita, A.; Yasuda, H.; Takaya, H.; Toriumi, K.; Ito, T.; Noyori, R. J. Am.
Chem. Soc. 1980, 102, 7932; (b) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990, 23,
345.
3. (a) Schmid, R.; Cereghetti, M.; Heiser, B.; Schonholzer, P.; Hansen, H.-J. Helv.
Chim. Acta 1988, 71, 897; (b) Schmid, R.; Broger, E. A.; Cereghetti, M.; Crameri,
Y.; Foricehr, J.; Lalonde, M.; Muller, R. K.; Scalone, M.; Schoettel, G.; Zutter, U.
Pure Appl. Chem. 1996, 68, 131.
for possible use in the hydrogenation with Pd-(R)-1d catalyst. Both
electron-deficient and electron-rich aryl ketones could be hydroge-
nated with high conversions and enantioselectivities (Table 3, en-
tries 1–9). For example, hydrogenated products with 98% ee were
obtainedforpara-substituted9b (entry2) and9d(entry4). Thehigh-
est enantioselectivity (99%) was also achieved upon hydrogenation
of m-methoxy-substituted phenyl ketone 9e (entry 5), which was
comparable to the best result obtained with Ru–phosphine com-
plexes.13 Alkyl ketone 9j also worked well, giving high enantioselec-
tivity (entry10). To our knowledge, these enantioselectivities arethe
highest achieved so far for the homogeneous Pd-catalyzed asym-
4. Saito, T.; Yokozawa, T.; Ishizaki, T.; Moroi, T.; Sayo, N.; Miura, T.; Kumobayashi,
H. Adv. Synth. Catal. 2001, 343, 264.
5. (a) Zhang, Z.; Qian, H.; Longmire, J.; Zhang, X. J. Org. Chem. 2000, 65, 6223; (b)
Wu, S.; Wang, W.; Tang, W.; Lin, M.; Zhang, X. Org. Lett. 2002, 4, 4495; (c) Lei,
A.; Wu, S.; He, M.; Zhang, X. J. Am. Chem. Soc. 2004, 126, 1626; (d) Wang, C.-J.;
Sun, X.; Zhang, X. Angew. Chem. 2005, 117, 5013. Angew. Chem., Int. Ed. 2005, 44,
4933; (e) Raghunath, M.; Zhang, X. Tetrahedron Lett. 2005, 46, 7017; (f) Wang,
C.-J.; Sun, X.; Zhang, X. Synlett 2006, 1169.
6. Pai, C.-C.; Lin, C.-W.; Lin, C.-C.; Chen, C.-C.; Chan, A. S. C. J. Am. Chem. Soc. 2000,
122, 11513.
metric hydrogenation of a
-phthalimide ketones.14
7. (a) Duprat de Paule, S.; Jeulin, S.; Ratovelomanana-Vidal, V.; Genêt, J.-P.;
Champion, N.; Dellis, P. Tetrahedron Lett. 2003, 44, 823; (b) Duprat de Paule, S.;
Jeulin, S.; Ratovelomanana-Vidal, V.; Genêt, J.-P.; Champion, N.; Dellis, P. Org.
Proc. Res. Dev. 2003, 7, 399; (c) Jeulin, S.; Duprat de Paule, S.; Ratovelomanana-
Vidal, V.; Genêt, J.-P.; Champion, N.; Dellis, P. Angew. Chem., Int. Ed. 2004, 43,
320; (d) Wu, J.; Ji, J.-X.; Chan, A. S. C. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 3570;
(e) Qiu, L.; Kwong, F. Y.; Wu, J.; Lam, W. H.; Chan, S.; Yu, W.-Y.; Li, Y.-M.; Guo,
R.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. 2006, 128, 5955; (f) Shintani, R.;
Yashio, K.; Nakamura, T.; Okamoto, K.; Shimada, T.; Hayashi, T. J. Am. Chem. Soc.
2006, 128, 2772.
In conclusion, we have developed a new class of atropisomeric
diphosphine ligands with a wide range of dihedral angles. X-ray
study of the Pd(II) complexes of these ligands showed that as the
bridge length increased, the dihedral angles and the ligand bite an-
gles increased as well, while an excessive increase in bridge length
had a reverse effect. These ligands afforded excellent enantioselec-
8. (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; (c) Zhang, Y. J.; Wei, H.; Zhang, J. M.; Zhang, W. Tetrahedron
2009, 65, 1281.
Table 3
Asymmetric hydrogenation of
a
-phthalimide ketonesa
9. 5,50-Heptamethylenedioxy-2,20-bis(diphenylphosphino) biphenyl (1a). 1H NMR
(400 MHz, CDCl3): d = 7.51–7.09 (m, 22H, ArH), 6.82 (dd, J = 3.0, 8.2 Hz, 2H,
ArH), 6.36 (d, J = 8.2 Hz, 2H, ArH), 4.19 (m, 2H, OCH), 3.86 (m, 2H, OCH), 1.93–
1.29 (m, 10H, CH); 13C NMR (100 MHz, CDCl3): d = 157.73, 149.81, 138.99,
138.94, 138.87, 135.92, 134.01, 133.90, 133.79, 133.62, 133.52, 133.42, 128.32,
128.30, 128.27, 128.24, 128.04, 127.03, 117.81, 116.44, 67.45, 26.78, 24.69,
22.13; 31P NMR (162 MHz, CDCl3, 85% H3PO4): d = ꢀ15.3; HRMS (ESI): Calcd for
O
HO
O
O
R
Pd(CF3CO2)2
ligand*
R
N
N
H
2 (100atm)
+
CF3CH2OH
80 oC,24h
O
O
10a- j
9a- j
C43H40O2P2 [M]+ 650.2504, found: 650.2506. For (R)-1a: ½a 2D7
ꢀ131 (c 0.50,
ꢁ
Entry
Substrate
9a (R = Ph)
Conv.b (%)
eec (%)
CHCl3). For (S)-1a: ½ ꢁ
a 2D7 130 (c 0.50, CHCl3). 5,50-Octamethylenedioxy-2,20-
1
2
3
4
5
6
7
8
9
>99
>99
>99
>99
>99
87
>99
>99
93
98
98
93
98
99
88
92
78
94
91
bis(diphenylphosphino)biphenyl (1b). 1H NMR (400 MHz, CDCl3): d = 7.40–7.10
(m, 20H, ArH), 6.96 (dt, J = 2.4, 8.8 Hz, 2H, ArH), 6.76 (dd, J = 3.8, 5.2 Hz, 2H,
ArH), 6.39 (d, J = 3.8 Hz, 2H), 3.89 (dd, J = 1, 2 Hz, 4H, OCH), 1.86–1.15 (m, 12H,
CH); 13C NMR (100 MHz, CDCl3): d = 159.28, 149.28, 149.08, 148.89, 138.73,
138.66, 138.59, 138.54, 138.48, 135.28, 134.22, 134.12, 134.01, 133.72, 133.62,
133.58, 133.51, 128.42, 128.40, 128.37, 128.31, 128.28, 128.24, 128.21, 128.13,
127.44, 127.41, 117.82, 115.23, 115.19, 115.15, 65.98, 28.99, 28.89, 25.25; 31P
NMR (162 MHz, CDCl3, 85% H3PO4): d = ꢀ14.4; HRMS (ESI) Calcd for C44H42O2P2
9b (R = p-CH3C6H4)
9c (R = p-PhC6H4)
9d (R = p-FC6H4)
9e (R = m-CH3OC6H4)
9f (R = p-ClC6H4)
9g (R = m-ClC6H4)
9h (R = o-ClC6H4)
9i (R = 2-naphthyl)
9j (R = Me)
[M]+ 664.2660, found: 664.2664. For (R)-1b: ½a 2D7
ꢀ123 (c 0.50, CHCl3). For (S)-
ꢁ
1b: ½a 2D7
ꢁ
+123 (c 0.50, CHCl3). 5,50-Nonamethylenedioxy-2,20-bis(diphenylphos-
10
>99
phino)biphenyl (1c). 1H NMR (400 MHz, CDCl3): d = 7.74–7.10 (m, 20H, ArH),
6.98 (d, J = 8.4 Hz, 2H, ArH), 6.79 (d, J = 8.4 Hz, 2H, ArH), 6.33 (s, 2H, ArH), 4.00
(m, 2H, OCH), 3.65 (m, 2H, OCH), 1.78–0.83 (m, 14H, CH); 13C NMR (100 MHz,
CDCl3): d = 158.15, 135.31, 134.19, 134.10, 133.67, 133.58, 133.47, 128.60,
128.56, 128.51, 128.37, 128.31, 128.10, 117.54, 117.42, 68.02, 28.34, 28.22,
27.01, 24.51; 31P NMR (162 MHz, CDCl3, 85% H3PO4): d = ꢀ14.8; HRMS (ESI)
a
b
c
Reaction conditions: Pd(CF3CO2)2 2.0 mol %, (R)-1d 2.4 mol %.
Determined by 1H NMR analysis of the crude products.
The enantiomeric excesses were determined by chiral HPLC using a Daicel
Chiralcel OJ-H column. The R absolute configurations were assigned by comparison
of optical rotations with the literature data.13,14

C. Wang et al. / Tetrahedron Letters 51 (2010) 2044–2047
2047
Calcd for C45H44O2P2 [Mꢀ1]+ 677.2738, found: 677.2743. For (R)-1c: ½a 2D7
ꢁ
ꢀ114
Å, b = 16.190(6) Å, c = 23.877(10) Å, b = 90°, V = 4695(3) Å3, Z = 4,
Mg mꢀ3 = 0.725 mmꢀ1
reflections (Rint = 0.0507), Final R indices [I > 2
q
calcd = 1.331
(c 0.50, CHCl3). For (S)-1c: ½a D27
ꢁ
+114 (c 0.50, CHCl3). 5,50-Decamethylenedioxy-
,
l
,
19527 reflections collected, 8191 independent
(I)]: R1 = 0.0483, wR2 = 0.1045.
2,20-bis(diphenylphosphino)biphenyl (1d). Yield 86%; 1H NMR (400 MHz, CDCl3):
d = 7.28–7.18 (m, 20H, ArH), 6.96 (dd, J =1.2, 8.4 Hz, 2H, ArH), 6.78 (dd, J = 2.4,
8.4 Hz, 2H, ArH), 6.37 (s, 2H, ArH), 3.89 (m, 2H, OCH), 3.64 (m, 2H, OCH), 1.70–
1.12 (m, 16H, CH); 13C NMR (100 MHz, CDCl3): d = 158.68, 135.41, 134.22,
134.12, 134.01, 133.69, 133.59, 133,49, 128.37, 128.07, 116.96, 116.18, 116.13,
67.50, 28.78, 28.71, 27.85, 24.91; 31P NMR (162 Hz, CDCl3, 85% H3PO4):
d = ꢀ15.1; HRMS (ESI) Calcd for C46H46O2P2 [M]+ 692.2973, found: 692.3002.
r
Compound (R)-4d: C46H46Cl2O2P2Pd, Mr = 870.07, T = 293(2) K, monoclinic,
P2(1)/c, a = 14.6665(9) Å, b = 12.2499(8) Å, c = 22.8437(14) Å, b = 97.0920(10)°,
V = 4072.8(4) Å3, Z = 4,
q
calcd = 1.419 Mg mꢀ3
,
l
= 0.703 mmꢀ1
,
24152
reflections collected, 9205 independent reflections (Rint = 0.0398), Final
indices [I > 2 (I)]: R1 = 0.0447, wR2 = 0.1006. Compound (R)-4e: C49H58Cl4O5
R
r
P2Pd, Mr = 1037.09, T = 296(2) K, monoclinic, P2(1)/c, a = 18.252(2) Å,
For (R)-1d: ½a 2D7
ꢁ
ꢀ75.7 (c 0.50, CHCl3). For (S)-1d: ½a D27
ꢁ
79.7 (c 0.50, CHCl3). 5,50-
b = 12.7537(14) Å, c = 28.133(2) Å, b = 128.557(4)°, V = 5121.1(9) Å3, Z = 4,
Dodecamethylenedioxy-2,20-bis(diphenyl phosphino)biphenyl (1e). Yield 82%; 1H
NMR (400 MHz, CDCl3): d = 7.31–7.21 (m, 20H, ArH), 6.97 (dt, J = 1.6, 8.8 Hz,
2H, ArH), 6.77 (dd, J = 2.4, 8.4 Hz, 2H, ArH), 6.42 (dd, J = 2.4, 4.0 Hz, 2H, ArH),
3.78(m, 2H, OCH), 3.63(m, 2H, OCH), 1.64–1.15 (m, 20H, CH); 13C NMR
(100 MHz, CDCl3): d = 158.69, 135.62, 134.15, 134.06, 133.96, 133.66, 133.56,
133.46, 128.45, 128.42, 128.38, 128.34, 128.03, 116.34, 116.09, 67.50, 29.18,
28.76, 28.47, 27.78, 24.86; 31P NMR (162 MHz, CDCl3, 85% H3PO4): d = ꢀ15.3;
HRMS (ESI) Calcd for C48H50O2P2 [M]+ 720.3286, found: 720.3272. For (R)-1e:
q
calcd = 1.345 Mg mꢀ3
,
l
= 0.676 mmꢀ1
,
26002 reflections collected, 9021
independent reflections (Rint = 0.0420), Final R indices [I > 2 (I)]: R1 = 0.0561,
r
wR2 = 0.1560. CCDC 749256 (R)-4b, 749257 (R)-4c, 749258 (R)-4d, and 749259
(R)-4e contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
11. Ozawa, F.; Kubo, A.; Matsumoto, Y.; Hayashi, T.; Nishioka, E.; Yanagi, K.;
Moriguchi, K. Organometallics 1993, 12, 4188.
½
a 2D7
ꢁ
ꢀ30.3 (c 0.50, CHCl3). For (S)-1e: ½a D27
ꢁ
30.3 (c 0.50, CHCl3).
12. (a) Bergmeier, S. C. Tetrahedron 2000, 56, 2561; (b) Ager, D. J.; Prakash, I.;
Schaad, D. R. Chem. Rev. 1996, 96, 835; (c) Bogevig, A.; Pastor, I. M.; Adolfsson,
H. Chem. Eur. J. 2004, 10, 394; (d) Petra, D. G. I.; Reek, J. N. H.; Handgraaf, J. W.;
Meijer, E. J.; Dierkes, P.; Kamer, P. C. J.; Brussee, J.; Schoemaker, H. E.; Van
Leeuwen, P. W. N. M. Chem. Eur. J. 2000, 6, 2818.
10. Crystallographic data for (R)-4b: C47H48Cl8O2P2Pd, Mr = 1096.79, T = 296(2) K,
monoclinic, P2(1), a = 13.488(2) Å, b = 12.6229(19) Å, c = 14.890(2) Å,
b = 96.663(2)°, V = 2518.1(6) Å3, Z = 2,
q , l ,
calcd = 1.447 Mg mꢀ3 = 0.893 mmꢀ1
13050 reflections collected, 8669 independent reflections (Rint = 0.0242), Final
R indices [I > 2 (I)]: R1 = = 0.0478, wR2 = 0.1260. Compound (R)-4c: C46H46Cl4
O2P2Pd, Mr = 940.97, T = 293(2) K, Orthorhombic, P2(1)2(1)2(1), a = 12.146(5)
r
13. Hu, A.; Lin, W. Org. Lett. 2005, 7, 455.
14. Wang, Y.-Q.; Lu, S.-M.; Zhou, Y.-G. Org. Lett. 2005, 7, 3235.