Reversal in enantioselectivity for the palladium-catalyzed asymmetric allylic substitution with novel metallocene-based planar chiral diphosphine ligands

Article abstract of DOI:10.1016/j.tetlet.2007.12.009

The novel C₂-symmetric metallocene-based ligands with only planar chirality were synthesized easily and applied in palladium-catalyzed asymmetric allylic substitution with excellent enantioselectivity and high catalytic activity. When two ester groups on Cp rings of the metallocene were replaced by hydroxymethyl groups, opposite configuration of the product was obtained with high catalytic activity and excellent enantioselectivity. The opposite configuration of products was also obtained when the hydroxyl groups were protected as esters or ethers. These results might be attributed to the different configuration of the diphosphine ligands-Pd(II) complexes.

Full text of DOI:10.1016/j.tetlet.2007.12.009

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 1012–1015
Reversal in enantioselectivity for the palladium-catalyzed
asymmetric allylic substitution with novel metallocene-based
planar chiral diphosphine ligands
Fang Xie, Delong Liu, Wanbin Zhang *
School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
Received 30 September 2007; revised 1 December 2007; accepted 4 December 2007
Available online 4 January 2008
Abstract
The novel C2-symmetric metallocene-based ligands with only planar chirality were synthesized easily and applied in palladium-
catalyzed asymmetric allylic substitution with excellent enantioselectivity and high catalytic activity. When two ester groups on Cp rings
of the metallocene were replaced by hydroxymethyl groups, opposite configuration of the product was obtained with high catalytic
activity and excellent enantioselectivity. The opposite configuration of products was also obtained when the hydroxyl groups were
protected as esters or ethers. These results might be attributed to the different configuration of the diphosphine ligands–Pd(II) complexes.
Ó 2007 Elsevier Ltd. All rights reserved.
The steric properties of ligands employed in asymmetric
metal catalysis are crucial for efficient transfer of chirality
and control of the absolute configuration of newly formed
stereocenters in the reaction. The preparation of two enan-
tiomers generally requires access to the ligands with oppo-
site absolute configurations. If a chiral ligand from a
natural product exists in only one enantiomeric form,
access to compounds derived from the opposite enantiomer
may be limited. To obtain products of opposite configura-
tion, one promising strategy would be the ability to prepare
ligands from the same chiral starting material via simple
modification of the structure. This means to prepare oppo-
site enantiomers with the ligands possessing identical chiral
scaffolds. There are some reports related to this strategy.1
But to the best of our knowledge, there has not been any
report on the reversal in enantioselectivity with modified
ligands with planar chirality.
C2-symmetric chiral metallocene-based ligands, 1,10-
bis(oxazolinyl)-2,20-diphenylphosphino metallocene (1,
Fig. 1), and their application for Pd-catalyzed asymmetric
allylic alkylation with excellent enantioselectivity (up to
99% ee).3 This type of ligands afford a C2-symmetric 1:2
P,N-chelation complex with palladium(II). Subsequently,
the oxazoline moiety was removed by ring-opening
followed by ester transformation to give C2-symmetric
metallocene with only planar chirality (2, Fig. 1).4 It was
shown that the twist angle in the complexes of these metal-
locene diphosphine ligands with palladium(II), which could
be adjusted by changing M and/or R0 group on Cp rings,
CO2R
M
O
R
R
R'
R'
Ph2
P
PPh2
PPh2
N
PPh2
PPh2
θ
Pd
M
M
Metallocene-based chiral ligands designed for asymmet-
ric synthesis have attracted much scientific attention over
the past decades.2 We had reported the synthesis of
P
N
Ph2
CO2R
O
1
2
3
M: (a=Fe, b=Ru)
*
Corresponding author. Tel./fax: +86 21 54743265.
Fig. 1.
E-mail address: wanbin@sjtu.edu.cn (W. Zhang).
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.12.009

F. Xie et al. / Tetrahedron Letters 49 (2008) 1012–1015
1013
had a pivotal influence on the asymmetric allylic substitu-
tions (3, Fig. 1).4c
scaffold. Then, we studied this reaction in details and the
results are summarized in Table 1.
To further explore the effects of twist angle on asymmet-
ric catalysis, novel metallocene-based diphosphine ligands
(4–6, Fig. 2) with different kind of substituents adjacent
to diphenylphosphine group were synthesized. Further-
more, their application in Pd-catalyzed asymmetric allylic
substitution was studied.
As shown in Table 1, ligands 2 gave excellent enantio-
selectivity (99% ee, S-configuration) in this reaction (Table
1, entries 1–4). When 4 was used as chiral ligands, high
catalytic activity and moderate enantioselectivity were
obtained (Table 1, entries 5 and 6). However, to our sur-
prise, the opposite R-configuration of the product was
obtained as the major isomer. To optimize the reaction
conditions, the effect of solvents was taken into account
first of all. Improved results were obtained with both tolu-
ene and THF (Table 1, entries 7–12), and 4a showed better
ee than 4b in these two solvents. Temperature affected the
enantioselectivity as well. The ee values were increased
(81% ee in THF and 76% ee in toluene) at 0 °C with 4a
as the ligands (Table 1, entries 13 and 14). The enantio-
selectivity was further improved in THF and up to 88%
ee was obtained at ꢀ78 °C with 4a (Table 1, entries 15–
17). However, the enantioselectivity was somewhat reduced
at lower temperature in toluene with 4b (Table 1, entry 18).
It was reported that the hydroxyl group in the ligands
was interacting via a hydrogen bond with the nucleo-
phile.13 To explain the results mentioned above, the hydro-
xyl groups in 4 were converted to ether and ester groups to
give the corresponding ligands 5 and 6, respectively. The
absolute configuration of product remains R-configuration
Ligands 4–6 were synthesized easily via the reduction
of ester amide 74 followed by protecting the hydroxyl
group as shown in Scheme 1. Thus, treating 7 with LiAlH4
in THF afforded 1,10-dihydroxymethyl-2,20-diphenylphos-
phino metallocene (4).5,6 Alcohol 4 could be converted to
5 and 6 via esterification and etherification, respec-
tively.7–10 They have identical chiral scaffold but different
substituents adjacent to diphenylphosphine group with 2.
The transition-metal-catalyzed asymmetric allylic
amination has become an invaluable tool for synthetic
chemists, as these types of amines are otherwise difficult
to prepare.11 Because of the ubiquity of the chiral amine
unit in biologically active compounds, we studied the
palladium-catalyzed asymmetric allylic amination using
ligands 4 as chiral ligands. To our surprise, the reversal
in enantioselectivity in this reaction was observed compar-
ing to that resulted by 2, though they have identical chiral
CH2OH
PPh2
CH2OAc
PPh2
CH2OMe
PPh2
Table 1
Asymmetric allylic amination of 1,3-diphenyl-2-propenyl acetate with
benzylaminea
M
M
M
PPh2
PPh2
PPh2
NHBn
Ph
OAc
Ph
NH2Bn / L*
CH2OH
CH2OAc
CH2OMe
Ph
Ph
4
5
6
(R or S)
rac-
M: (a=Fe, b=Ru)
Entry
Ligands
Solvent
T (°C)
Time (min)
eeb,c (%)
1d
2d
3d
4d
5
6
7
8
9
2aa0
2ab0
2ba0
2bb0
4a
Toluene
Toluene
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
Toluene
Toluene
THF
THF
DMF
DMF
THF
0
0
ꢀ25
ꢀ25
20
20
20
20
20
20
20
20
0
240
240
90
180
20
20
20
20
20
20
20
20
30
99 (S)
99 (S)
99 (S)
99 (S)
55 (R)
60 (R)
70 (R)
69 (R)
70 (R)
67 (R)
28 (R)
46 (R)
81 (R)
76 (R)
86 (R)
87 (R)
88 (R)
61 (R)
Fig. 2.
O
CH2OH
NHAc
i-Pr
i-Pr
NHAc
PPh2
O
4b
4a
LiAlH4
PPh2
PPh2
M
M
4b
4a
PPh2
O
CH2OH
4
O
10
11
12
13
14
15
16
17
18
a
4b
4a
7
4b
4a
Ac2O / Pyr.
RONa / ROH
Me2SO4 / KOBu-t
4a
4a
Toluene
THF
THF
THF
Toluene
0
30
ꢀ10
ꢀ25
ꢀ78
ꢀ10
120
8 h
72 h
60
4a
4a
CH2OAc
PPh2
CH2OMe
PPh2
CO2R
4a
PPh2
PPh2
Molecular ratio: [Pd(g3-C3H5)Cl]2/ligand/substrate/benzylamine = 1/
2.2/200/600; reactions were conducted under nitrogen with more than 95%
yield; the catalysts were prepared by treating [Pd(g3-C3H5)Cl]2 with
ligands in suitable solvent at 20 °C for 1 h before use.
M
M
M
PPh2
CH2OAc
5
PPh2
CH2OMe
CO2R
b
Determined by the HPLC using chiral OJ-H column.
The absolute configuration was determined according to the
2
6
c
M: (a=Fe, b=Ru) R: (a'=Me, b'=Et)
literature.12
d
Scheme 1.
See Ref. 4.

1014
F. Xie et al. / Tetrahedron Letters 49 (2008) 1012–1015
even if 5 and 6 were used as chiral ligands (Table 2, entries
1–4). These results indicated that the hydroxyl group in 4
was not crucial for the reversal in configuration of the
products.
Furthermore, to investigate if the reversal was caused by
the hydrogen bond between the nucleophile (NH2Bn) and
the oxygen atom in ligands 4–6, we also carried out the
Pd-catalyzed asymmetric allylic alkylation with dimethyl
malonate as a nucleophile. The results were shown in
Table 3.
R'
M
R'
R'
Ph2
P
θ
Ph2
P
θ
Pd
Pd
M
P
P
Ph2
Ph2
R'
8
3
(M=Fe, Ru)
Fig. 3.
Pd(II) after much effort. It was known that the complex of
2 with Pd(II) existed as the configuration 3 by X-ray anal-
ysis of the single crystal in our previous research.4c It was
deduced that the configuration of the complexes of 4–6
with Pd(II) might exist as 8 (Fig. 3). This is possible
because the steric interaction between the phenyl group
and methylene group in R0 in complex 8 for ligands 4,
5 and 6 is much smaller than that between the phenyl group
and the carbonyl group in R0 for ligand 2, which would
make the formation of complex 8 easier than that of com-
plex 3 for 4–6. The opposite configuration of 8 from 3
might be responsible for the reversed configuration of the
product.
As shown in Table 3, the reversal in enantioselectivity
was still observed when chiral ligands 4 and 5 were used.
Up to 73% ee value was obtained when 5b was used as
the ligand at ꢀ78 °C. These results indicated that the pos-
sible hydrogen bond between the nucleophile and the
ligands was not crucial for the reversal in configuration
either.
We tried to find an explanation by X-ray analysis, but
failed to obtain a single crystal of any of these ligands with
Table 2
Asymmetric allylic amination of 1,3-diphenyl-2-propenyl acetate with
benzylaminea
In summary, novel C2-symmetric metallocene-based
ligands with only planar chirality were synthesized and
applied in the palladium-catalyzed asymmetric allylic
amination. Modification of the substituents adjacent to
the diphenylphosphine group on the Cp rings can switch
the configuration of the product in this amination with
excellent enantioselectivity and high catalytic activity. This
phenomenon of the reversal was also observed in the
asymmetric allylic alkylation. These results might be attri-
buted to the different configuration of the complexes of the
diphosphine ligands with Pd(II).
NHBn
Ph
OAc
Ph
NH2Bn / L*
Ph
Ph
(R)
rac-
Entry
Ligands
Solvent
T (°C)
Time (min)
eeb,c (%)
1
2
3
4
a
5a
5b
6a
6b
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
20
20
20
20
20
20
20
20
33 (R)
42 (R)
22 (R)
44 (R)
Molecular ratio: [Pd(g3-C3H5)Cl]2/ligand/substrate/benzylamine = 1/
2.2/200/600; reactions were conducted under nitrogen with more than 95%
yield; the catalysts were prepared by treating [Pd(g3-C3H5)Cl]2 with
ligands in suitable solvent at 20 °C for 1 h before use.
Acknowledgments
b
Determined by the HPLC using chiral OJ-H column.
c
The absolute configuration was determined according to the
literature.12
This work was partly supported by the National Natural
Science Foundation of China (No. 20572070) and Nippon
Chemical Industrial Co., Ltd.
Table 3
Asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with
dimethyl malonatea
References and notes
CH(CO2Me)2
Ph
OAc
Ph
H2C(CO2Me)2 / L*
1. (a) Kimura, K.; Sugiyama, E.; Ishizuka, T.; Kunieda, T. Tetrahedron
Lett. 1992, 33, 3147–3150; (b) Hoarau, O.; Ait-Haddou, H.; Daran,
J.-C.; Cramailere, D.; Balavoine, G. G. A. Organometallics 1999, 18,
4718–4723; (c) Evans, D. A.; Johnson, J. S.; Burgey, C. S.; Campos,
K. R. Tetrahedron Lett. 1999, 40, 2879–2882; (d) Sibi, M. P.; Chen, J.;
Cook, G. R. Tetrahedron Lett. 1999, 40, 3301–3304; (e) Chelucci, G.;
Pinna, G. A.; Saba, A.; Valenti, R. Tetrahedron: Asymmetry 2000, 11,
4027–4036; (f) Li, X.-G.; Cheng, X.; Ma, J.-A.; Zhou, Q.-L. J.
Organomet. Chem. 2001, 640, 65–71; (g) Sibi, M. P.; Liu, M. Curr.
Org. Chem. 2001, 5, 719–755; (h) Cobb, A. J. A.; Marson, C. M.
Tetrahedron: Asymmetry 2001, 12, 1547–1550; (i) Cobb, A. J. A.;
Marson, C. M. Tetrahedron 2005, 61, 1269–1279; (j) Frolander, A.;
Lutsenko, S.; Privalov, T.; Moberg, C. J. Org. Chem. 2005, 70, 9882–
9891.
Ph
Ph
Entry
(R)
rac-
Ligands
Solvent
T (°C)
Time (min)
eeb,c (%)
1
2
3
4
5
4a
4b
5a
5b
5b
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
rt
rt
rt
rt
20
20
20
8 (R)
22 (R)
2 (R)
45 (R)
73 (R)
20
ꢀ78
8 h
Molecular ratio: [Pd(g3-C3H5)Cl]2/ligand/substrate/benzylamine =
2.5/6.0/200/600; reactions were conducted under nitrogen with more than
95% yield; The catalysts were prepared by treating [Pd(g3-C3H5)Cl]2 with
ligands in CH2Cl2 solvent at 20 °C for 1 h before use.
a
b
Determined by the HPLC using chiral OD-H column.
The absolute configuration was determined according to the
2. (a) Selected reviews: Ferrocenes; Hayashi, T., Togni, A., Eds.; Wily-
VCH: Weinheim, Germany, 1995; (b) Metallocenes; Togni, A.,
Haltermann, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998;
c
literature.14

F. Xie et al. / Tetrahedron Letters 49 (2008) 1012–1015
1015
(c) Dai, L.-X.; Tu, T.; You, S. L.; Deng, W. P.; Hou, X.-L. Acc.
Chem. Res. 2003, 36, 659–667; (d) Colacot, T. J. Chem. Rev. 2003,
103, 3101–3118; (e) Arrays, R. G.; Adrio, J.; Carretero, J. C. Angew.
Chem., Int. Ed. 2006, 45, 7674–7715. Selected papers: (f) Zhang, W.;
Yoneda, Y.-I.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Tetrahedron:
Asymmetry 1998, 9, 3371–3380; (g) Zhang, W.; Yoneda, Y.-I.; Kida,
T.; Nakatsuji, Y.; Ikeda, I. J. Organomet. Chem. 1999, 574, 19–23; (h)
Imai, Y.; Zhang, W.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Chem. Lett.
1999, 243–244; (i) Zhang, W.; Yoshinaga, H.; Imai, Y.; Kida, T.;
Nakatsuji, Y.; Ikeda, I. Synlett 2000, 1512–1514; (j) Zhang, W.; Xie,
F.; Yoshinaga, H.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Tetrahedron
2006, 62, 9038–9042; (k) Hua, G. H.; Liu, D. L.; Xie, F.; Zhang, W.
Tetrahedron Lett. 2007, 48, 385–388; (l) Zheng, W.-H.; Zheng, B.-H.;
Zhang, Y.; Hou, X.-L. J. Am. Chem. Soc. 2007, 129, 7718–7719.
3. (a) Zhang, W.; Adachi, Y.; Hirao, T.; Ikeda, I. Tetrahedron:
Asymmetry 1996, 7, 451–460; (b) Zhang, W.; Hirao, T.; Ikeda, I.
Tetrahedron Lett. 1996, 37, 4545–4548; (c) Liu, D. L.; Xie, F.; Zhang,
W. Tetrahedron Lett. 2007, 48, 585–588; (d) Liu, D. L.; Xie, F.;
Zhang, W. Tetrahedron Lett. 2007, 48, 7591–7594; (e) Liu, D, L.; Xie,
F.; Zhang, W. Tetrahedron, submitted for publication.
132.43, 132.61, 134.78, 134.99, 136.39, 136.48, 139.35, 139.45, 170.71;
31P NMR (CDCl3, 162 Hz, 85% H3PO4): d ꢀ23.71; MS (MALDI):
m/z 699 [M+1+] (100); HRMS calcd for C40H36O4P2Fe 698.1457,
found 698.14328.
D
8. 5b mp 139–140 °C. ½aꢁ27 ꢀ390.5 (c 0.28, CHCl3); 1H NMR (CDCl3,
400 Hz): d 1.66 (s, 6H), 3.84 (br s, 2H), 4.43 (t, J = 2.4 Hz, 2H), 4.78
(d, J = 12.4 Hz, 2H), 4.93 (br s, 2H), 4.96 (dd, J = 2.4, 12.4 Hz, 2H),
7.20–7.30 (m, 20H); 13C NMR (CDCl3, 100 Hz): d 20.68, 61.01, 61.10,
75.35, 76.80, 76.84, 78.18, 78.21, 83.47, 83.60, 91.23, 91.50, 128.13,
128.20, 128.25, 128.31, 129.27, 132.56, 132.74, 134.50, 134.71, 136.87,
136.94, 139.45, 139.56, 170.69; 31P NMR (CDCl3, 162 Hz, 85%
H3PO4): d ꢀ23.10; MS (MALDI): m/z 745 [M+1+] (100); HRMS
calcd for C40H36O4P2Ru 744.1139, found 744.11269.
D
1
9. 6a mp 144–146 °C. ½aꢁ27 ꢀ412.5 (c 0.885, CHCl3); H NMR (CDCl3,
400 Hz): d 3.17 (s, 6H), 3.28 (br s, 2H), 4.11 (t, J = 2.4 Hz, 2H), 4.28
(d, J = 11.2 Hz, 2H), 4.41 (dd, J = 2.8, 11.2 Hz, 2H), 4.47 (br s, 2H),
7.07–7.11 (m, 4H), 7.19–7.25 (m, 10H), 7.28–7.32 (m, 2H), 7.35–7.39
(m, 4H); 13C NMR (CDCl3, 100 Hz): d 58.26, 69.27,69.37, 72.67,
72.70, 72.84, 72.87, 75.08, 75.12, 90.49, 90.74, 127.82, 128.07, 128.13,
128.27, 128.36, 129.40, 132.16, 132.33, 135.02, 135.23, 137.14, 137.22,
139.97, 140.06; 31P NMR (CDCl3, 162 Hz, 85% H3PO4): d ꢀ22.75;
MS (MALDI): m/z 643 [M+1+] (100); HRMS calcd for
C38H36O2P2Fe 642.1556, found 642.15345.
4. (a) Zhang, W.; Kida, T.; Nakatsuji, Y.; Ikeda, I. Tetrahedron Lett.
1996, 37, 7995–7998; (b) Zhang, W.; Shimanuki, T.; Kida, T.;
Nakatsuji, Y.; Ikeda, I. J. Org. Chem. 1999, 64, 6247–6251; (c) Liu, D.
L.; Xie, F.; Zhang, W. J. Org. Chem. 2007, 72, 6992–6997.
D
1
10. 6b mp 166–167 °C. ½aꢁ27 ꢀ438.3 (c 0.545, CHCl3); H NMR (CDCl3,
400 Hz): d 3.18 (s, 6H), 3.84 (br s, 2H), 4.07 (d, J = 11.2 Hz, 2H), 4.27
(t, J = 2.4 Hz, 2H), 4.33 (dd, J = 2.4, 11.2 Hz, 2H), 4.85 (m, 2H),
7.22–7.28 (m, 16H), 7.32–7.36 (m, 4H); 13C NMR (CDCl3, 100 Hz): d
58.15, 68.93, 69.02, 74.98, 76.28, 76.32, 77.92, 77.95, 82.23, 82.35,
93.56, 93.83, 127.94, 128.07, 128.15, 128.18, 128.22, 129.21, 132.30,
132.47, 134.77, 134.99, 137.73, 137.80, 140.05, 140.15; 31P NMR
(CDCl3, 162 Hz, 85% H3PO4): d ꢀ22.48; MS (MALDI): m/z 689
[M+1+] (100); HRMS calcd for C38H36O2P2Ru 688.1234, found
688.12286.
D
1
5. 4a mp 136–137 °C. ½aꢁ27 ꢀ444.3 (c 0.825, CHCl3); H NMR (CDCl3,
400 Hz): d 3.46 (br s, 2H), 3.55 (s, 2H), 3.97 (br s, 2H), 4.27 (d,
J = 13.6 Hz, 2H), 4.56 (d, J = 13.2 Hz, 2H), 4.62 (br s, 2H), 7.09–7.13
(m, 4H), 7.22–7.34 (m, 12H), 7.39–7.43 (m, 4H); 13C NMR (CDCl3,
100 Hz): d 59.63, 59.72, 71.74, 71.76, 72.22, 72.26, 72.77, 72.79, 72.81,
72.83, 74.89, 74.96, 96.08, 96.30, 128.39, 128.48, 128.56, 128.61,
129.58, 132.27, 132.45, 134.83, 135.04, 136.31, 136.39, 138.77, 138.86;
31P NMR (CDCl3, 162 Hz, 85% H3PO4): d ꢀ22.47; MS (MALDI):
m/z 615 [M+1+] (100); HRMS calcd for C36H32O2P2Fe 614.1231,
found 614.12215.
11. For reviews: (a) Trost, B. M. Chem. Pharm. Bull. 2002, 50, 1–14; (b)
Trost, B. M.; Crawley, M. L. Chem. Rev. 2003, 103, 2921–2943. For
papers: (a) Hayashi, T.; Yamamoto, A.; Ito, Y.; Nishioka, E.; Miura,
H.; Yanagi, K. J. Am. Chem. Soc. 1989, 111, 6301–6311; (b) Trost, B.
M.; Bunt, R. C. J. Am. Chem. Soc. 1994, 116, 4089–4090; (c) Evans,
D. A.; Campos, K. R.; Tedrow, J. S.; Michael, F. E.; Gagne, M. R.
J. Org. Chem. 1999, 64, 2994–2995; (d) You, S.-L.; Zhu, X.-Z.; Lou,
Y.-M.; Hou, X.-L.; Dai, L.-X. J. Am. Chem. Soc. 2001, 123, 7471–
7472; (e) Mori, M.; Nakanishi, M.; Kajishima, D.; Sato, Y. J. Am.
Chem. Soc. 2003, 125, 9801–9807; (f) Uozumi, Y.; Tanaka, H.;
Shibatomi, K. Org. Lett. 2004, 6, 281–283; (g) Takahashi, K.;
Nakano, H.; Fujita, R. Tetrahedron Lett. 2005, 46, 8927–8930.
12. Hayashi, T.; Yamamoto, A.; Ito, Y.; Nishioka, E.; Miura, H.;
Yanagi, K. J. Am. Chem. Soc. 1989, 111, 6301–6311.
D
6. 4b mp 155–157 °C. ½aꢁ27 ꢀ488.1 (c 1.08, CHCl3); 1H NMR (CDCl3,
400 Hz): d 3.23 (br s, 2H), 3.92 (br s, 2H), 4.23 (br s, 2H), 4.23 (d,
J = 13.2 Hz, 2H), 4.49 (dd, J = 1.6, 13.6 Hz, 2H), 4.99 (br s, 2H),
7.22–7.26 (m, 6H), 7.28–7.31 (m, 10H), 7.34–7.38 (m, 4H); 13C NMR
(CDCl3, 100 Hz): d 58.87, 58.95, 73.94, 75.36, 75.38, 75.72, 75.74,
75.77, 75.78, 79.94, 80.03, 99.47, 99.70, 128.23, 128.31, 128.58, 128.63,
128.69, 129.43, 132.31, 132.50, 134.64, 134.83, 136.49, 136.55, 138.80,
138.89; 31P NMR (CDCl3, 162 Hz, 85% H3PO4): d ꢀ21.67; MS
(MALDI): m/z 661 [M+1+] (100); HRMS calcd for C36H32O2P2Ru
660.0915, found 660.09156.
D
1
7. 5a mp 140–142 °C. ½aꢁ27 ꢀ306.0 (c 0.415, CHCl3); H NMR (CDCl3,
400 Hz): d 1.64 (s, 6H), 3.32 (br s, 2H), 4.27 (br s, 2H), 4.54 (br s, 2H),
4.95 (d, J = 12 Hz, 2H), 5.11 (d, J = 11.6 Hz, 2H), 7.06–7.10 (m, 4H),
7.20–7.23 (m, 10H), 7.27–7.35 (m, 6H); 13C NMR (CDCl3, 100 Hz): d
20.61, 61.39, 61.49, 73.14, 73.17, 73.56, 73.60, 75.33, 75.36, 78.81,
78.92, 87.77, 88.02, 128.14, 128.16, 128.22, 128.34, 128.42, 129.52,
13. Ait-Haddou, H.; Hoarau, O.; Cramailere, D.; Pezet, F.; Daran, J.-C.;
Balavoine, G. G. A. Chem. Eur. J. 2004, 10, 699–707.
14. Wimmer, P.; Widhalm, M. Tetrahedron: Asymmetry 1995, 6, 657–660.