Chirality control of tropos diphenylmethane-derived phosphoramidites by chiral dienes: Its application to asymmetric Michael addition

Article abstract of DOI:10.3987/COM-08-S(F)102

The Rh complex of tropos diphenylmethane-derived phosphoramidite could be chirally controlled to adopt single chiral conformation upon addition of a chiral diene. In the asymmetric Michael addition of α-cyanocarboxylates catalyzed by the Rh complexes, the

Full text of DOI:10.3987/COM-08-S(F)102

HETEROCYCLES, Vol. 77, No. 2, 2009
927
HETEROCYCLES, Vol. 77, No. 2, 2009, pp. 927 - 943. © The Japan Institute of Heterocyclic Chemistry
Received, 25thJuly, 2008, Accepted, 30th September, 2008, Published online, 2nd October, 2008
DOI: 10.3987/COM-08-S(F)102
CHIRALITY CONTROL OF TROPOS DIPHENYLMETHANE-DERIVED
PHOSPHORAMIDITES BY CHIRAL DIENES: ITS APPLICATION TO
ASYMMETRIC MICHAEL ADDITION
Kazuki Wakabayashi, Kohsuke Aikawa, and Koichi Mikami*
Department of Applied Chemistry, Tokyo Institute of Technology, O-okayama,
Meguro-ku, Tokyo 152-8552, Japan. E-mail: mikami.k.ab@m.titech.ac.jp
§In honor of Professor Emeritus Keiichiro Fukumoto on 75th birthday
Abstract – The Rh complex of tropos diphenylmethane-derived phosphoramidite
could be chirally controlled to adopt single chiral conformation upon addition of a
chiral diene. In the asymmetric Michael addition of α-cyanocarboxylates
catalyzed by the Rh complexes, the chiral diene and bisphenylmethane-derived
phosphoramidite functioned to attain higher enantioselectivity and catalytic
activity via asymmetric activation.
INTRODUCTION
Various asymmetric catalysts with atropisomeric (atropos in Greek)1 ligands have been developed to
attain high enantioselectivity.2
For example, Rh complexes with atropos BINOL-derived
phosphoramidites were used as catalytically active and enantioselective catalysts for a variety of
asymmetric reactions.3 On the other hand, we have reported that chirally flexible (tropos)1
benzophenone-derived ligands can be chirally controlled to a single chiral conformation by a chiral
activator to attain higher catalytic activity and enantioselectivity via “asymmetric activation”.2f,g,4
Herein, we report that the Rh complexes with tropos diphenylmethane-derived phosphoramidites 1a-d
can be controlled to a single chiral conformation by a chiral diene (Scheme 1) to attain higher catalytic
activity and enantioselectivity in the asymmetric Michael addition. Chiral dienes5 could not only
control the conformation of Rh complexes with tropos diphenylmethane-derived phosphoramidites but
also increase catalytic activity and enantioselectivity of the resultant Rh-phosphoramidite complexes than
that with achiral ethylene.
In the asymmetric Michael addition, both chiral dienes and
diphenylmethane-derived phosphoramidites in the Rh complexes could function to attain higher
enantioselectivity and catalytic activity via asymmetric activation.2f,g,6

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HETEROCYCLES, Vol. 77, No. 2, 2009
R
R
achiral
phosphoramidite
O
P
O
1a: R = 4-Me, R' = Bn
1b: R = 2-Me, R' = Me
1c: R = 2-tBu, 4-Me, R' = Me
1d: R = 2-tBu, 4-Me, R' = Bn
R'
N
R'
O
P
O
R'
N
R'
R
R
metal
&
+
Xyl
chiral diene
MeO
*
*
chirality
control
R'
R'
Diene C1-D
M
O
M
O
*
N
N
P
X
P
X
Ph
R'
R'
O
O
MeO
R
R
Bn
Diene C2'-D
R
R
Scheme 1
RESULTS AND DISCUSSION
Complexation of achiral diphenylmethane-derived phosphoramidites 1a-d and [RhCl(C1-D)]2 was found
to give single enantiomeric RhCl(C1-D)(phosphoramidite) complex. Even though excess 1a-d was
added, only RhCl(C1-D) complexes with one phosphoramidite were obtained along with an excess
31
amount of phosphoramidite remained. In P NMR analysis of RhCl(C1-D)(1c), one doublet peak was
observed to show that RhCl(C1-D)(1c) possessed a single conformation.
The most stable conformation of RhCl(C1-D)(1c) was deduced by DFT calculation using
RhCl(C1-D’)(1c’) as the model (Figure 1).7 The front view shows that the dimethylamino group of 1c’
stays away from the xylyl group of chiral diene C1-D’ and the phosphoramidite (1c’) exists in the
opposite side of chiral diene C1-D’.
Different from RhCl(C1-D)(1c’), the conformation of
phosphoramidite in RhCl(C2’-D’)(1c’) (the model of RhCl(C2’-D)(1c) complex) is determined by the
steric repulsion between the diphenylmethane group of 1c’ and the benzyl group of C2’-D’. Therefore,
the conformations of phosphoramidite were different between RhCl(C1-D’)(1c’) (upper) and
RhCl(C2’-D’)(1c’) (lower). On the other hand, the top right view shows that the phosphoramidite (1c’)
adopts a chiral C1-symmetric conformation because of the steric interaction between the
diphenylmethane and chiral diene. 1H NMR spectrum of RhCl(C1-D)(1c) indeed showed the
C1-symmetric conformation of 1c; 2-tert-Butyl-4-methylphenyl group in the phosphoramidite (1c)
exhibited two singlets of the tert-butyl group and two singlets of the methyl group.

HETEROCYCLES, Vol. 77, No. 2, 2009
929
N
O
Xyl
N
Rh
P
P
Cl
O
O
O
Rh
P
O
C1
Cl
O
N
RhCl(C1-D')(1c')
Top View
Front View
Ph
N
P
Bn
N
Rh
P
O
Cl
Rh
O
O
O
O
Cl
P
N
O
C1
RhCl(C2'-D')(1c')
Top View
Front View
Figure 1. DFT calculation of RhCl(chiral diene)(phosphoramidite) complex
There are few reports on the complexes with only single phosphoramidite as highly enantioselective
catalysts. For example, the Ir-cod complex with single chiral phosphoramidite has recently been
reported to attain higher catalytic activity and enantioselectivity in the asymmetric hydrogenation.8 On
the other hand, we found that the Rh-chiral diene complexes with diphenylmethane-derived
phosphoramidites attain high catalytic activity in the asymmetric Michael addition of
α-cyanocarboxylate.9 The Rh-diene complexes with single phosphoramidite catalyzed the asymmetric
Michael addition without dissociation of the chiral diene part. Therefore, the diene part increases the
catalytic activity and enantioselectivity. To clarify the effect of the diene part, the asymmetric Michael
additions catalyzed by the Rh catalysts of the chiral phosphoramidite (1e) and several achiral dienes were
examined (Table 1). RhCl(nbd)(1e) catalyzed the Michael addition even at -78 °C to afford product 3a
in 96% yield with 48% ee (entry 1).10 1,5-Cycloocatadiene (cod) and 1,5-dimethylcycloocatadiene
(DM-COD) gave lower enantioselectivities (entries 4 and 5) but 1,2-dibromonorbornadiene (Br-nbd)
provided higher enantioselectivity (entry 3). These results indicate that six-membered bicyclic dienes
attained higher enantioselectivity than eight-membered monocyclic dienes.

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HETEROCYCLES, Vol. 77, No. 2, 2009
Table 1. Asymmetric Michael addition of α-cyanocarboxylate
Phosphoramidite:
O
O
O
[RhCl(diene)]2 (1 mol%)
O
NC
Phosphoramidite 1e (2 mol%)
O
P N
O
Ph
Ph
OEt
OEt
+
iPr2NEt (10 mol%)
CH2Cl2, -78 °C, 3 h
NC
3a
(5 eq.)
2a
Entry
Yield (%)
Ee (%)
Diene
1e
Diene:
96
n.r.
95
96
95
48
-
nbd
nbd
1
Br
Br
2a
nbd
Br-nbd
56
39
2
Br-nbd
cod
3
4
cod
DM-cod
DM-cod
5
a. without iPr2NEt
The Rh complexes with chiral six-membered bicyclic diene C1-D and C2’-D were thus used as
asymmetric catalysts (Table 2). Chiral dienes C1-D and C2’-D controlled the conformation of achiral
phosphoramidite to attain higher enantioselectivity in the asymmetric Michael addition. Low catalytic
activity of RhCl(ethylene)2 (1a) (entry 3) clearly shows that both phosphoramidites and chiral dienes
exert to give higher catalytic activity (entries 4 and 5).
Table 2. Asymmetric Michael addition with RhCl(chiral dienes)(achiral phosphoramidites)
O
O
O
Phosphoramidite:
[RhCl(diene)]2 (1 mol%)
NC
OR1
OR1
*
O
Phosphoramidite (2 mol%)
+
NC
iPr2NEt (10 mol%)
CH2Cl2, -78 °C, 3 h
O
2a: R1 = Et
3a: R1 = Et
Ph
Ph
(5 eq.)
P N
2b: R1 = tBu
3b: R1 = tBu
O
OR1
OEt
OEt
OEt
OEt
OEt
OEt
OEt
OEt
OtBu
OtBu
Diene
Yield (%)
Ee (%)
Entry
Phosphoramidite
1a
C1-D
C2'-D
(C2H4)2
C1-D
92
90
70
95
92
94
95
94
95
81
15 (S)
32 (S)
-
1
2
-
-
O
P N
O
3
1a
1a
1a
1b
1c
1c
1c
1d
54 (S)
43 (R)
38 (S)
63 (S)
41 (R)
86 (S)
78 (S)
4
1b
C2'-D
C1-D
5
tBu
6
R'
P N
O
C1-D
7
O
R'
C2'-D
C1-D
8
tBu
1c (R' = Me)
1d (R' = Bn)
9
C1-D
10

HETEROCYCLES, Vol. 77, No. 2, 2009
931
The Rh-chiral diene (C1-D) complexes with the achiral phosphoramidite (1a) attained higher
enantioselectivity than Rh-chiral diene (C2’-D) complexes (entries 4 vs. 5). The 4-methyl group of the
phosphoramidite (1a) did not affect the enantioselectivity, but the bulky 2-tert-butyl group of the
phosphoramidite (1c) attained higher enantioselectivity (entries 4 vs. 7). Furthermore, the asymmetric
Michael addition of 2-cyanopropionic acid tert-butyl ester catalyzed by RhCl(C1-D)(1c) gave product 3b
in 95% yield with 86% ee (entry 9). However, the phosphoramidite (1d) bearing benzyl amine and
tert-butyl group was too bulky to decrease the catalytic activity and enantioselectivity (entry 10).
The absolute configuration of products could be dictated by the chiral dienes (entries 4 vs. 5 and 7 vs. 8).
Figure 1 shows that the conformation of phosphoramidite (1c) is different between RhCl(C1-D)(1c) and
RhCl(C2’-D)(1c). In the case of the Rh-catalyzed Michael addition of α-cyano carboxylate, the active
intermediate has been reported to be the N-bonded enolate complex of α-cyanocarboxylate.9a,c The
enantioface of the N-bonded enolate complex is reversed (entries 4 vs. 5 and 7 vs. 8) by changing the
chiral dienes from RhCl(C1-D)(1c) to RhCl(C2’-D)(1c) (Figure 2). Both the N-bonded enolate
complexes are attacked by an electrophile from the opposite side of the phosphoramidite (1c);
Therefore, the Rh complex with C1-symmetric chiral diene C1-D gives (S)-enriched products and the Rh
complex with pseudo C2-symmetric chiral diene C2’-D affords (R)-enriched products.
N-bonded enolate of RhCl(C1-D')(1c')
N-bonded enolate of RhCl(C2'-D')(1c')
O
Rh
CN
O-
O
Rh
CN
O-
(R)-product
(S)-product
Figure 2. The conformation of cyanoester in two N-bonded enolate complexes
CONCLUSION
In the Rh complexes, the monodentate diphenylmethane-derived phosphoramidite can be controlled by a
chiral diene to possess a single chiral conformation. The complex with the chirally controlled

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HETEROCYCLES, Vol. 77, No. 2, 2009
phosphoramidite could be used in the asymmetric Michael additions of α-cyanocarboxylates. Both the
chiral diene and achiral diphenylmethane-derived phosphoramidite cooperated to give higher yields and
enantiomeric excesses.
EXPERIMENTAL
13
31
1H NMR, C NMR, and P NMR spectra were measured on Bruker AV300 (300 MHz) spectrometer.
Capillary gas chromatographic analysis (GC) was conducted on Shimadzu GC-14B instrument equipped
with FID detector and capillary column coated with PEG-20 M by using N2 as a carrier gas. Peak area
was calculated by Shimadzu C-R6A as an automatic integrator. CP-Chirasil-Dex CB (i.d. 0.25 mm x 25
m, CHROMPACK; GL Science) was used as chiral column. Optical rotations were measured on a
JASCO DIP-370. TOF Mass spectra were measured on a JEOL JMS-T100LC. Computational
calculations were executed on Sun Fire X4600 (Tokyo Institute of Technology).
All experiments were carried out under an argon atmosphere otherwise noted. Analytical thin layer
chromatography (TLC) was performed on a glass plates pre-coated with silica-gel (Merck Kieselgal 60
F254, layer thickness 0.25 mm). Visualization was accomplished by UV light (254 nm), anisaldehyde,
KMnO4. Column chromatography was performed on KANTO Silica Gel 60N (spherical, neutral) or ICN
Alumina N (neutral, Activity Super I). Dichloromethane (dehydrate) and toluene (dehydrate) were
purchased from Kanto Chemical Co., Inc.
1,5-Dibromocycloocta-1,5-diene11 and 2-cyanopropionic acid tert-butyl ester (2b)12 were prepared by the
reported method. 2,3-Dibromobicyclo[2.2.1]hepta-2,5-diene (Br-nbd),13 (2S,8R)-2-(3,5-dimethylphenyl)-
8-methoxy-1,8-dimethylbicyclo[2.2.2]octa-2,5-diene (C1-D),5 (1S,4S,8S)-5-benzyl-2-phenyl-8-methoxy-
1,8-dimethyl-bicyclo[2.2.2]octa-2,5-diene (C2’-D)5 and [RhCl(C1-D)]26 were also prepared by the
reported method.
(2,10-Dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)dibenzylamine (1a)
To a solution of 2,2’-methylenebis(4-methylphenol) (45.7 mg, 0.2 mmol) in toluene (2 mL) was added
HMPT (hexamethylphosphoric triamide) (45 µL, 0.24 mmol) at rt under an argon atmosphere. After
stirred for 2 h at 100 °C, toluene and excess HMPT were evaporated under reduced pressure. The residue
and 1H-tetrazole (21.1 mg, 0.3 mmol) were dissolved in toluene. To the mixture was added
dibenzylamine (38 µL, 0.2 mmol) at rt. After stirred for 24 h at 100 °C, the reaction mixture was
quenched with H2O three times. The organic layer was dried over K2CO3. After concentration under
reduced pressure, the residue was purified by alumina column chromatography (hexane/CH2Cl2 = 10/1)
to give phosphoramidite 1a (68.9 mg, 76% yield).
1H NMR (CDCl3, 300 MHz) δ 2.32 (s, 6H), 3.54 (d, 1H, J = 12.9 Hz), 4.33 (d, 4H, J = 10.2 Hz), 4.35 (dd,

HETEROCYCLES, Vol. 77, No. 2, 2009
933
1H, J = 12.6, 3.0 Hz), 6.99 (br, 4H), 7.16 (s, 2H), 7.29-7.46 (m, 10H).
13C NMR (CDCl3, 75 MHz) δ 22.78, 34.13, 47.86, 48.14, 122.51, 127.11, 128.40, 128.56, 128.63, 130.40,
133.93, 134.71, 134.74, 138.38, 148.82, 148.88.
31P NMR (CDCl3, 121 MHz) δ 138.18.
TOF-HRMS (ESI), Calcd for C29H29NO2P [M+H]+: 454.1936, Found: 454.1946.
(4,8-Dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)dimethylamine (1b)
To a solution of 2,2’-methylenebis(6-methylphenol) (45.7 mg, 0.2 mmol) in toluene (2 mL) was added
HMPT (45 µL, 0.24 mmol) at rt under an argon atmosphere. After stirred for 2 h at 100 °C, toluene and
excess HMPT were evaporated under reduced pressure. The residue was purified by alumina column
chromatography (hexane/CH2Cl2 = 10/1) to give phosphoramidite 1b (36.8 mg, 61% yield).
1H NMR (CDCl3, 300 MHz) δ 2.27 (s, 6H), 2.97 (d, 6H, J = 10.8 Hz), 3.48 (d, 1H, J = 12.3 Hz), 4.46 (dd,
1H, J = 12.3, 3.0 Hz), 6.93 (t, 2H, J = 7.5 Hz), 7.04 (d, 2H, J = 7.5 Hz), 7.19 (d, 2H, J = 7.5 Hz).
13C NMR (CDCl3, 75 MHz) δ 16.95, 16.99, 33.99, 34.53, 35.16, 35.40, 124.10, 124.12, 127.42, 127.44,
129.01, 131.10, 131.14, 135.71, 135.75, 149.34, 149.40.
31P NMR (CDCl3, 121 MHz) δ 138.72.
TOF-HRMS (ESI), Calcd for C17H21NO2P [M+H]+: 302.1310, Found: 302.1298.
(4,8-Di-tert-butyl-2,10-dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)dimethyl-
amine (1c)
Phosphoramidite 1c was prepared from 2,2’-methylenebis(6-tert-butyl-4-methylphenol) in a similar
manner to phosphoramidite 1b (90% yield).
1H NMR (CDCl3, 300 MHz) δ 1.40 (s, 18H), 2.30 (s, 6H), 2.96 (d, 6H, J = 9.3 Hz), 3.33 (d, 1H, J = 12.3
Hz), 4.35 (dd, 1H, J = 12.3, 3.0 Hz), 7.02 (d, 2H, J = 2.1 Hz), 7.11 (d, 2H, J = 2.1 Hz).
13C NMR (CDCl3, 75 MHz) δ 21.05, 30.75, 30.81, 34.73, 35.60, 35.86, 126.39, 128.56, 132.73, 136.16,
136.20, 141.61, 141.66, 148.30, 148.40.
31P NMR (CDCl3, 121 MHz) δ 144.28.
TOF-HRMS (ESI), Calcd for C25H37NO2P [M+H]+: 414.2562, Found: 414.2561.
(4,8-Di-tert-butyl-2,10-dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)dibenzyl-
amine (1d)
Phosphoramidite 1d was prepared from 2,2’-methylenebis(6-tert-butyl-4-methylphenol) and
dibenzylamine in a manner similar to phosphoramidite 1a (88% yield).
1H NMR (CDCl3, 300 MHz) δ 1.58 (s, 18H), 2.44 (s, 6H), 3.52 (d, 1H, J = 12.6 Hz), 4.53 (d, 4H, J = 7.2

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HETEROCYCLES, Vol. 77, No. 2, 2009
Hz), 4.64 (dd, 1H, J = 12.6, 2.7 Hz), 7.19 (d, 2H, J = 2.1 Hz), 7.28 (d, 2H, J = 2.1 Hz), 7.38-7.56 (m,
10H).
13C NMR (CDCl3, 75 MHz) δ 21.18, 31.40, 31.47, 34.90, 35.11, 48.53, 48.79, 126.72, 127.19, 128.23,
128.59, 129.79, 133.18, 136.75, 136.78, 137.75, 137.82, 141.72, 141.77, 147.56, 147.64.
31P NMR (CDCl3, 121 MHz) δ 137.53.
TOF-HRMS (ESI), Calcd for C37H45NO2P [M+H]+: 566.3194, Found: 566.3188.
(S,S)-N-(2,10-Dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)bis(1-phenylethyl)-
amine (1e)
To a solution of 2,2’-methylenebis(4-methylphenol) (45.7 mg, 0.2 mmol) in toluene (2 mL) was added
HMPT (hexamethylphosphoric triamide) (45 µL, 0.24 mmol) at rt under an argon atmosphere. After
stirred for 2 h at 100 °C, toluene and excess HMPT were evaporated under reduced pressure. The residue
and 1H-tetrazole (21.1 mg, 0.3 mmol) were dissolved in toluene. To the mixture was added
bis[(S)-1-phenylethyl]amine (45 µL, 0.2 mmol) at rt. After stirred for 24 h at 100 °C, the reaction mixture
was quenched with H2O three times. The organic layer was dried over K2CO3. After concentration under
reduced pressure, the residue was purified by alumina column chromatography (hexane/CH2Cl2 = 10/1)
to give phosphoramidite 1e (38.4 mg, 40% yield).
1H NMR (CDCl3, 300 MHz) δ 1.87 (d, 6H, J = 7.2 Hz), 2.32 (s, 3H), 2.33 (s, 3H), 3.48 (d, 1H, J = 12.9
Hz), 4.42 (dd, 1H, J = 12.9, 3.0 Hz), 4.94 (dq, 2H, J = 11.7, 7.2 Hz), 6.64 (d, 1H, J = 8.1 Hz), 6.93 (d, 1H,
J = 8.1 Hz), 6.99 (s, 2H), 7.16-7.30 (m, 12H).
13C NMR (CDCl3, 75 MHz) δ 20.80, 22.08, 22.21, 34.08, 53.00, 53.16, 122.57, 122.61, 122.73, 122.78,
126.58, 127.80, 128.03, 128.07, 128.49, 130.22, 130.38, 133.75, 135.13, 143.55, 143.57, 149.45, 149.54,
149.71, 149.80.
31P NMR (CDCl3, 121 MHz) δ 142.20.
TOF-HRMS (ESI), Calcd for C31H32NO2PNa [M+Na]+: 504.2068, Found: 504.2060.
[α]D27 -66 (c 0.50 in CHCl3).
[RhCl(C2’-D)]2
A mixture of (1S,4S,8S)-5-benzyl-2-phenyl-8-methoxy-1,8-dimethylbicyclo[2.2.2]octa-2,5-diene (chiral
diene C2’-D) (33.0 mg, 0.1 mmol) and [RhCl(ethylene)2] (21.4 mg, 0.055 mmol) in benzene (4.0 mL)
was stirred under an argon atmosphere at rt for 24 h, and then the reaction mixture was filtered through
Celite. After the filtrate was evaporated under reduced pressure, the yellow residue was washed with
Et2O. Prolonged evacuation of the product at 50 °C gave [RhCl(C2’-D)]2 (90% yield). The product was
diastereomeric mixture.

HETEROCYCLES, Vol. 77, No. 2, 2009
935
1H NMR (300 MHz, CDCl3) major diastereomer δ 0.89 (d, J = 13.8 Hz, 1H), 1.09 (d, J = 13.8 Hz, 1H),
1.14 (s, 3H), 1.78 (s, 3H), 2.91 (d, J = 15.9 Hz, 1H), 3.00 (d, J = 15.9 Hz, 1H), 3.07 (s, 3H), 3.30 (s, 1H),
3.40-3.42 (m, 1H), 4.06 (d, J = 5.4 Hz, 1H), 7.22-7.39 (m, 6H), 7.95-8.00 (m, 4H).
1H NMR (300 MHz, CDCl3) minor diastereomer δ 0.85 (d, J = 14.1 Hz, 1H), 1.03 (d, J = 14.1 Hz, 1H),
1.14 (s, 3H), 1.63 (s, 3H), 3.05 (s, 3H), 3.21-3.30 (m, 3H), 3.36 (s, 1H), 4.12 (d, J = 6.3 Hz, 1H),
7.22-7.39 (m, 4H), 7.52-7.47 (m, 2H), 7.79-7.81 (m, 2H), 7.95-8.00 (m, 2H).
13C NMR (75 MHz, CDCl3) major diastereomer δ 21.80, 41.21, 46.22 (d, JRh-C = 10.9 Hz), 47.68, 49.56,
49.76 (d, JRh-C = 3.6 Hz), 53.13 (d, JRh-C = 2.9 Hz), 55.85 (d, JRh-C = 10.8 Hz), 70.84 (d, JRh-C = 12.1 Hz),
71.46 (d, JRh-C = 11.2 Hz), 77.24, 81.10, 126.22, 127.12, 128.15, 130.41, 130.85, 131.12, 137.66, 138.39.
13C NMR (75 MHz, CDCl3) minor diastereomer δ 21.90, 41.31, 44.90 (d, JRh-C = 11.6 Hz), 47.58, 49.46,
54.12, 55.01 (d, JRh-C = 10.1 Hz), 71.74 (d, JRh-C = 11.2 Hz), 81.03, 120.33, 127.20, 130.92, 137.72,
138.49.
Anal. Calcd for C48H52Cl2O2Rh2·2H2O: C, 57.10; H, 5.99. Found: C, 57.10; H, 5.99. H2O was derived
from ether that washed the yellow residue (1H NMR: 1.52 (s, 4H)).
[α]D27 -76 (c 1.2 in CHCl3).
[RhCl(Br-nbd)]2
[RhCl(Br-nbd)]2 was prepared from 2,3-dibromobicyclo[2.2.1]hepta-2,5-diene (Br-nbd) and
[RhCl(ethylene)2] in a similar to manner as [RhCl(C2’-D)]2 (40% yield).
1H NMR (CDCl3, 300 MHz) δ 1.20-1.27 (m, 4H), 1.58 (br, 2H), 1.76 (d, 2H, J = 9.6 Hz), 4.32 (br, 2H),
4.57 (br, 2H).
1,5-Dimethylcycloocta-1,5-diene (DM-cod)
To a suspension of 1,5-dibromocycloocta-1,5-diene (280 mg, 1.05 mmol) and NiCl2(dppp) (23 mg, 0.04
mmol) in dry Et2O (20 mL) was added methyl Grignard reagent (1.59 mmol, 3.0 M in Et2O) under an
argon atmosphere at 0 °C. The reaction mixture was stirred for 30 min at 0 °C, for 1 h at rt and for 2 h at
reflux. H2O (20 mL) was added and the reaction mixture was extracted with Et2O. Combined organic
layer was dried over MgSO4 and solvent was removed under reduced pressure. Crude product was
purified by flash chromatography over silica-gel eluted with pentane to give the product (yield 90%).
1H NMR (300 MHz, CDCl3) δ 0.95 (d, J = 6.9 Hz, 12 H), 2.29-2.38 (m, 10 H), 5.32 (t, J = 6.0 Hz, 2H).
13C NMR (75 MHz, CDCl3) δ 26.3, 33.3, 122.5, 135.8.
[RhCl(dm-cod)]2
[RhCl(dm-cod)]2 was prepared from 1,5-dimethylcycloocta-1,5-diene (DM-cod) and [RhCl(ethylene)2]

936
HETEROCYCLES, Vol. 77, No. 2, 2009
in a similar to manner as [RhCl(C2’-D)]2 (30% yield). The product was diastereomeric mixture.
1H NMR (300 MHz, CDCl3) δ 1.50 (s, 6H, dia. minor), 1.65-1.85 (m, 8H), 1.72 (s, 6H, dia. major),
2.05-2.23 (m, 4H), 2.47-2.64 (m, 4H), 3.79 (d, 2H, J = 7.2 Hz, dia. minor), 3.99 (d, 2H, J = 6.9 Hz, dia.
major).
RhCl(C1-D)(1c)
To a mixture of (4,8-di-tert-butyl-2,10-dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-
yl)dimethylamine (1c) (8.3 mg, 0.02 mmol) and [RhCl(C1-D)]2 (8.0 mg, 0.01 mmol) was added CH2Cl2
(1 mL) at rt under an argon atmosphere. After stirred for 1 h, the reaction mixture was concentrated
under reduced pressure to give RhCl(C1-D)(1c) complex (16.1 mg, 98% yield).
1H NMR (CDCl3, 300 MHz) δ 0.90 (s, 1H), 0.94 (s, 1H), 1.15 (s, 3H), 1.31 (s, 9H), 1.34 (s, 9H), 1.39 (s,
3H), 2.26 (s, 6H), 2.29 (s, 3H), 2.31 (s, 3H), 2.72 (br, 1H), 3.22 (d, 6H, J = 9.0 Hz), 3.27 (s, 3H), 3.57 (br,
1H), 3.90 (d, 1H, J = 15.6 Hz), 4.18 (t, 1H, J = 6.0 Hz), 5.00 (t, 1H, J = 4.8 Hz), 6.83 (s, 1H), 6.98 (br,
2H), 7.01 (br, 2H), 7.07 (br, 2H).
31P NMR (CDCl3, 121 MHz) δ 119.5 (d, JP-Rh = 268.6 Hz).
[α]D27 -65 (c 0.20 in CHCl3).
m/z (ESI): Calcd for Rh(C1-D)(1c) [M-Cl]+: 784.3, 785.3, 786.3. Found: 784.3, 785.3, 786.3.
RhCl(nbd)(1e)
To a mixture of (S,S)-N-(2,10-Dimethyl-12H-5,7-dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)bis(1-
phenylethyl)amine (1e) (9.6 mg, 0.02 mmol) and [RhCl(nbd)]2 (4.6 mg, 0.01 mmol) was added CH2Cl2
(1 mL) at rt under an argon atmosphere. After stirred for 1 h, the reaction mixture was concentrated
under reduced pressure to give RhCl(nbd)(1e) complex (11.8 mg, 98% yield).
1H NMR (CDCl3, 300 MHz) δ 1.22 (s, 2H), 1.73 (d, 6H, J = 7.2 Hz), 2.31 (s, 3H), 2.32 (s, 3H), 2.86 (br,
1H), 3.23 (br, 1H), 3.46 (br, 2H), 3.79 (d, 1H, J = 13.8 Hz), 4.58 (d, 1H, J = 13.8 Hz), 5.13 (br, 1H), 5.22
(br, 1H), 5.34 (dq, 2H, J = 14.1, 7.2 Hz), 6.81 (d, 1H, J = 8.1 Hz), 6.90 (d, 1H, J = 8.1 Hz), 7.01 (dd, 1H,
J = 8.1, 2.1 Hz), 7.08 (d, 1H, J = 2.1 Hz), 7.10 (d, 1H, J = 2.1 Hz), 7.21 (d, 1H, J = 8.1 Hz), 7.30-7.40 (m,
6H), 7.51 (d, 4H, J = 7.5 Hz).
31P NMR (CDCl3, 121 MHz) δ 125.0 (d, JP-Rh = 266.0 Hz).
[α]D27 -2.4 (c 0.25 in CHCl3).
m/z (ESI): Calcd for Rh(nbd)(1e) [M-Cl]+: 676.2, 677.2, 678.2, 679.2, 680.2. Found: 676.2, 677.2, 678.2,
679.2, 680.2.
Typical procedure for Rh-catalyzed Michael addition of α-cyanocarboxylate

HETEROCYCLES, Vol. 77, No. 2, 2009
937
To a mixture of [RhCl(C1-D)]2 (0.8 mg, 0.001 mmol) and (4,8-di-tert-butyl-2,10-dimethyl-12H-5,7-
dioxa-6-phosphadibenzo[a,d]cycloocten-6-yl)dimethylamine 1c (0.8 mg, 0.002 mmol) was added
CH2Cl2 (2.0 mL) under an argon atmosphere. After stirred for 30 min at rt, to the solution was added
2-cyanoproionic acid tert-butyl ester (2b) (15.5 mg, 0.1 mmol). After cooled down to -78 °C, to the
reaction mixture were added acrolein (35 µL, 0.5 mmol) and iPr2NEt (1.7 µL, 0.01 mmol). After stirred
for 3 h at -78 °C, the reaction mixture was evaporated under reduced pressure. The residue was purified
by silica-gel chromatography (hexane/EtOAc = 3/2) to give 2-cyano-2-methyl-5-oxopentanoate acid
tert-butyl ester (3b) (20.0 mg, 95% yield).
2-Cyano-2-methyl-5-oxopentanoate acid ethyl ester (3a)9c
1H NMR (CDCl3, 300 MHz) δ 1.28 (t, J = 7.2 Hz, 3H), 1.57 (s, 3H), 2.05 (ddd, J = 14.4, 10.2, 5.7 Hz,
1H), 2.22 (ddd, J = 14.4, 9.9, 6.0 Hz, 1H), 2.59 (ddd, J = 18.6, 10.2, 6.0 Hz, 1H), 2.69 (ddd, J = 18.6, 9.9,
5.7 Hz, 1H), 4.21 (q, J = 7.2 Hz, 2H), 9.73 (s, 1H).
13C NMR (CDCl3, 121 MHz) δ 13.98, 23.51, 30.02, 39.76, 43.03, 63.09, 119.37, 186.71, 199.12.
[α]D27 +1.3 (c 1.0 in CHCl3) for a sample that is 48% ee (R).
GC (column, CP-Chirasil-Dex CB, i.d. 0.25 mm x 25 m, Chrompack; carrier gas, N2 (75 kPa); column
temp, 110 ºC; injection and detection temp, 140 ºC; split rate, 100:1), tR = 21.2 min (S)/23.9 min (R).
2-Cyano-2-methyl-5-oxopentanoate acid tert-butyl ester (3b)9c
1H NMR (CDCl3, 300 MHz) δ 1.52 (s, 9H), 1.60 (s, 3H), 2.10 (ddd, J = 14.4, 10.2, 5.4 Hz, 1H), 2.23
(ddd, 1H, J = 14.4, 10.5, 5.1 Hz), 2.64 (dddd, 1H, J = 18.3, 10.2, 5.4, 0.9 Hz), 2.77 (dddd, 1H, J = 18.3,
10.5, 5.1, 0.9 Hz), 9.82 (s, 1H).
13C NMR (CDCl3, 121 MHz) δ 23.51, 27.75, 29.96, 39.84, 43.77, 84.37, 119.68, 167.67, 199.26.
[α]D27 -2.4 (c 0.90 in CHCl3) for a sample that is 86% ee (S).
GC (column, CP-Chirasil-Dex CB, i.d. 0.25 mm x 25 m, Chrompack; carrier gas, N2 (75 kPa); column
temp, 115 ºC; injection and detection temp, 150 ºC; split rate, 100:1), tR = 15.7 min (S)/17.1 min (R).
Computational Methods
All the calculations were performed with GAUSSIAN 03 program package. All the structures were
optimized at B3LYP/631SDD (SDD for Rh, 6-31G(d) for others) level. The optimized geometries were
verified as an equilibrium structures having no imaginary frequency.
RhCl(C1-D’)(1c’)
Charge = 0, Multiplicity = 1
SCF Done: E(B3LYP/631SDD) = -2358.51183292 a.u.

938
HETEROCYCLES, Vol. 77, No. 2, 2009
---------------------------------------------------------------------------------------------------------
Center
Atomic
Number
Atomic
Type
Coordinates (Angstroms)
Number
X
Y
Z
---------------------------------------------------------------------------------------------------------
1
2
3
4
5
6
7
8
9
45
17
6
6
6
6
6
6
6
1
6
1
1
6
6
6
6
6
1
6
6
6
8
6
6
1
6
6
6
6
6
8
15
7
6
6
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-0.467484
-0.702947
4.557692
4.122801
3.773662
-2.109814
-0.707117
-0.118831
-2.734195
-0.146096
-3.961428
-2.439387
0.915855
4.144550
3.792825
-1.152354
-2.229070
-2.771180
-0.708602
3.045237
2.669677
3.035147
2.720335
-2.520967
-1.940388
-2.738587
3.608372
3.982770
5.336979
6.302475
5.908820
2.258187
1.495836
1.510175
2.616456
0.269801
-0.055143
-0.525996
0.416190
3.516212
0.226444
0.531228
-0.412179
1.031689
1.851019
1.691030
-0.282779
0.992254
0.477405
-1.142827
0.066959
2.394898
1.194238
3.205293
4.053581
2.107251
-0.262740
-1.678397
3.086599
3.556698
2.215972
1.378719
0.030237
0.660258
2.081054
2.831346
-1.442480
-2.785535
-3.122034
-2.115277
-0.776155
-1.107355
-0.767158
-2.165221
-2.606153
-2.912391
-2.852447
-2.495542
-3.967358
-2.028530
0.110569
2.480094
-1.076132
-1.232357
0.006375
-0.696621
-1.954487
-1.823432
-0.883954
-2.309328
-0.141006
0.061788
-2.083294
0.030181
1.078392
-1.812082
-2.148249
-2.346544
-1.618667
2.147435
2.159519
1.103320
1.248440
-3.384060
-3.159528
-3.121410
-1.000839
-0.982910
-1.017171
-1.067150
-1.104000
-0.974848
0.485250
1.398598
2.247700
1.595245
2.642199
0.973170
1.324994
2.043904
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

HETEROCYCLES, Vol. 77, No. 2, 2009
939
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
1
1
1
1
1
6
6
6
6
6
1
1
1
1
1
1
1
1
1
1
1
6
1
6
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.353841
2.829022
-1.268155
-2.071225
-3.601649
-3.980913
-5.168889
-6.342013
-6.358662
-5.164598
7.358408
4.102193
3.255059
4.919069
4.723954
2.756386
2.077698
3.210555
5.633559
6.661874
-3.061890
-5.159091
-7.266948
-7.647592
-5.176998
-4.491457
-4.797120
-6.159882
-8.075707
-8.405849
-7.492123
-2.601939
-2.253844
-3.842333
-2.483673
-3.666985
2.365955
0.189534
0.701637
-0.092744
-0.418869
-0.576125
-0.410564
-0.093898
-2.370202
5.094425
1.046275
1.567531
3.597663
4.204826
1.795588
-3.547110
-4.167243
0.006052
0.032230
-0.593006
-0.829161
-0.567346
0.059484
-1.409451
0.312451
-0.816366
-1.568714
0.152203
-0.413164
-2.291367
-2.153847
-1.691995
3.307935
2.060658
-3.976981
-4.266663
-3.563534
1.247775
1.921242
1.182630
-0.210606
-0.857905
-1.092534
1.059063
-1.905865
-1.760212
-0.802715
2.969819
2.965196
-0.942597
-1.005102
-1.167487
1.811584
3.422978
1.698560
-0.985684
-1.933582
3.724156
3.924534
3.806933
-0.851202
-0.651973
-2.058417
-1.454610
-3.188538
-2.563111
---------------------------------------------------------------------------------------------------------
RhCl(C2’-D’)(1c’)
Charge = 0, Multiplicity = 1
SCF Done: E(B3LYP/631SDD) = -2550.24063124 a.u.
---------------------------------------------------------------------------------------------------------
Center
Atomic
Number
Atomic
Type
Coordinates (Angstroms)
Number
X
Y
Z
---------------------------------------------------------------------------------------------------------

940
HETEROCYCLES, Vol. 77, No. 2, 2009
1
2
3
4
5
6
7
8
9
45
17
6
6
6
6
6
6
6
1
6
1
6
6
6
6
6
6
1
6
6
6
8
6
6
1
6
6
6
6
6
8
15
7
6
6
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-0.671154
-1.412963
4.029316
2.874107
2.031666
-0.397908
-2.705829
-2.570678
-0.543374
-3.403149
0.551077
0.552126
-3.367285
1.647593
0.814360
-1.694153
-2.040426
-2.345668
-1.529842
0.337384
0.706451
1.545457
1.954328
-2.558364
-2.362987
-1.723377
3.828296
4.893317
6.192150
6.415765
5.340874
2.538982
1.468567
2.038488
3.183695
1.277188
2.207267
3.272278
2.016480
0.542696
-0.316048
0.347716
-3.321094
-3.617541
0.187146
-1.216696
-1.205753
-1.787459
-2.887960
0.897711
1.119696
0.053841
2.021413
1.109902
3.018216
0.682065
-1.244088
-3.980902
-4.989746
0.395771
2.424963
3.568049
-0.476467
-4.923905
-3.855902
-2.855020
-1.888692
2.766087
1.565948
1.835801
-0.123320
0.510266
0.040410
-1.055385
-1.661854
0.360649
-0.308301
0.026035
-0.637924
0.878174
-0.960786
-2.182515
-4.033929
-5.821137
-5.698915
-3.765635
1.231760
3.039951
0.448590
2.237715
-1.180490
-1.971342
-1.337967
-1.536092
-0.095541
-0.954952
-0.683072
0.737014
-0.488349
-2.015772
-0.917662
-2.130611
-1.649714
-2.158961
-0.540608
0.426767
-2.797700
-0.339584
0.474837
-0.020590
0.889926
-1.981394
-2.941797
-3.790416
-0.310760
0.329262
0.130898
-0.704925
-1.357129
-0.127091
0.974052
2.507138
3.128661
3.415796
-2.249110
-2.912307
-3.152634
-2.294243
0.050846
1.494301
-3.357260
-1.910390
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44

HETEROCYCLES, Vol. 77, No. 2, 2009
941
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
1
6
6
6
6
6
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
6
1
6
6
6
1
1
1
6
6
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-2.020662
0.834794
1.851824
2.609354
2.337510
1.318842
4.688562
7.024961
7.424407
5.519543
3.698680
2.846862
3.893425
0.983608
0.363367
1.876909
0.265084
2.917262
3.402039
2.055002
1.111285
-3.463903
-4.748559
-2.778443
-5.859043
-7.133594
-7.316179
-2.052899
-3.423779
-1.831255
-6.217238
-4.942304
-5.725664
-7.983307
-8.307976
-6.350016
-4.087258
3.651807
3.592433
4.534913
4.930531
4.375348
3.432365
1.362651
0.531346
-1.426939
-2.498896
-1.276845
-1.259719
0.108713
0.311618
1.226747
1.745838
3.281990
4.676057
5.665238
4.959110
3.011768
-1.595516
-1.133852
-2.003439
-0.829850
-0.714019
-0.902058
3.318301
3.768530
4.489831
-1.207660
-1.324822
-0.690986
-0.482952
-0.815183
-1.360404
-1.557842
-2.340312
0.762699
0.907883
-0.197235
-1.448052
-1.590287
0.969137
0.626947
-0.862421
-2.028330
2.413130
3.970001
3.509408
4.309063
2.932129
3.725038
1.631989
-2.316939
-0.083843
1.887933
-2.570248
-1.953501
-0.296817
-0.390075
-1.096699
-0.539896
0.831995
1.451767
0.430092
0.138466
1.637137
1.078276
-2.168167
-1.177511
1.268181
2.705216
1.707305
---------------------------------------------------------------------------------------------------------
REFERENCES AND NOTES
1. The word atropos consists of “a” meaning “not” and “tropos” meaning “turn” in Greek. Therefore,
the chirally rigid or flexible nature of a ligand can be called atropos or tropos, respectively. K.

942
HETEROCYCLES, Vol. 77, No. 2, 2009
Mikami, K. Aikawa, Y. Yusa, J. J. Jodry, and M. Yamanaka, Synlett, 2002, 1561. Also see: W.
Kuhn, 'Stereochemie', ed. by K. Freudenberg, Franz Deuticke, Leipzig, 1933, pp. 803-824.
2. a) 'Catalytic Asymmetric Synthesis', Vol. I and II, ed. by I. Ojima, VCH, New York, 1993, 2000. b)
H. Brunner and W. Zettlmeier, 'Handbook of Enantioselective Catalysis', VCH, Weinheim, 1993. c)
R. Noyori, 'Asymmetric Catalysis in Organic Synthesis', Wiley, New York, 1994. d) 'Transition
Metals for Organic Synthesis', ed. by M. Beller and C. Bolm, VCH: Weinheim, 1998. e)
'Comprehensive Asymmetric Catalysis', Vol. 1-3, ed. by E. N. Jacobsen, A. Pfaltz, and H.
Yamamoto, Springer, Berlin, 1999. f) 'New Frontiers in Asymmetric Catalysis', ed. by K. Mikami
and M. Lautens, Wiley, New York, 2007. g) Review on Asymmetric Activation, K. Mikami, M.
Terada, T. Korenaga, Y. Matsumoto, M. Ueki, and R. Angelaud, Angew. Chem. Int. Ed., 2000, 39,
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without increase in the catalytic activity (even with decrease). For the asymmetric synergy (effect),

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see: K. Aikawa, S. Akutagawa, and K. Mikami, J. Am. Chem. Soc., 2006, 128, 12648.
7. All the calculations were performed with GAUSSIAN 03 program package. All the structures were
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Rh(acac)(CO)2
diphosphine
O
O
O
O
Ph2P
Ph2P
NC
+
OMe
OMe
OEt
OR
NC
0 °C: 86%, 73% ee
diphosphine (Ref. 9b)
-78 °C: 0%
10. For deprotonation of cyanocarboxylate, a catalytic amount of iPr2NEt was needed in this Michael
addition (see Table 1: entry 2).
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