Asymmetric conjugate addition of cis-2-arylethenylboronic acids catalyzed by chiral diene/rhodium complexes: 1,4-rhodium shift from alkenylrhodium to arylrhodium intermediates

Article abstract of DOI:10.1016/j.tetasy.2012.03.004

The reaction of (E)-1,2-diphenylethenylboronic acid 1 with 2-cyclohexenone in the presence of a chiral diene/rhodium catalyst (5 mol %) gave 3-[2-((E)-2-phenylethenyl)phenyl]cyclohexanone in 99% yield with 98.7% ee; the catalytic cycle involves a 1,4-rhodium shift from a 2-phenylethenylrhodium to an ortho-alkenylphenylrhodium intermediate. In the reaction of 1 with (E)-1-phenyl-2-buten-1-one, either the tandem 1,4-shift/arylation product or the direct alkenylation product is formed selectively by an appropriate choice of chiral diene ligand.

Full text of DOI:10.1016/j.tetasy.2012.03.004

Tetrahedron: Asymmetry 23 (2012) 373–380
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Asymmetric conjugate addition of cis-2-arylethenylboronic acids catalyzed
by chiral diene/rhodium complexes: 1,4-rhodium shift from alkenylrhodium
to arylrhodium intermediates
Keigo Sasaki a, Tamio Hayashi a,b,
⇑
a Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
b Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589, Saudi Arabia
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of (E)-1,2-diphenylethenylboronic acid 1 with 2-cyclohexenone in the presence of a chiral
diene/rhodium catalyst (5 mol %) gave 3-[2-((E)-2-phenylethenyl)phenyl]cyclohexanone in 99% yield
with 98.7% ee; the catalytic cycle involves a 1,4-rhodium shift from a 2-phenylethenylrhodium to an
ortho-alkenylphenylrhodium intermediate. In the reaction of 1 with (E)-1-phenyl-2-buten-1-one, either
the tandem 1,4-shift/arylation product or the direct alkenylation product is formed selectively by an
appropriate choice of chiral diene ligand.
Received 9 February 2012
Accepted 6 March 2012
Available online 5 April 2012
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
O
O
The rhodium-catalyzed asymmetric conjugate addition of orga-
noboron reagents to electron-deficient olefins provides a powerful
method for creating a new stereogenic carbon center.1 Since its
first report in 1998,2 this catalytic asymmetric reaction has at-
tracted considerable attention due to its great synthetic utility.
The substrate scope is very broad, with high catalytic activity
and high enantioselectivity being observed for the asymmetric
addition of aryl- and alkenylboronic acids, and their derivatives,
to olefins bearing electron-deficient groups under mild and envi-
ronmentally friendly reaction conditions.3 The rhodium-catalyzed
asymmetric conjugate addition has been modified to a variety of
asymmetric carbon–carbon bond forming reactions.1 One of the
interesting variations is the reaction which involves a 1,4-rhodium
shift from alkenylrhodium to arylrhodium intermediates in the
catalytic cycle.4 Multiple carbon–carbon bonds are formed by
way of the 2-arylethenylrhodium complex as a key intermediate,
which is generated by the arylrhodation of alkynes and is isomer-
ized into the ortho-alkenylphenylrhodium intermediate by the 1,
4-rhodium shift. A typical example of the rhodium-catalyzed
asymmetric carbon–carbon bond forming reactions involving the
1,4-rhodium shift, the asymmetric synthesis of spirocarbocycles,5
is shown in Scheme 1. The 1,4-shift of rhodium from alkyl to aryl
has also been reported to play a key role in several types of reac-
tions represented by the asymmetric isomerization of 3-arylcyclo-
butanols to indane derivatives.6
[RhCl((R,R)-Bn-bod*)]2
(5 mol % Rh)
+
Ph4BNa
Ph
H
H2O (2.0 equiv)
THF, 65°C
Ph
73% yield
97% ee
Rh Ph
Ph
Ph
O
Rh
O
(R,R)-Bn-bod*
H
H
Ph
Rh
O
Ph
1,4-addition
1,4-shift
Rh
Ph
H
Scheme 1. Rhodium-catalyzed asymmetric synthesis of spirocarbocycles involving
the 1,4-rhodium shift.
We have been interested in the chemical behavior of the 2-aryl-
ethenylrhodium intermediate, particularly its reactivity toward the
1,4-shift forming the ortho-alkenylphenylrhodium intermediate
and the addition of both 2-arylethenyl- and ortho-alkenylphenyl-
rhodium intermediates to electron-deficient olefins. We have
studied the rhodium-catalyzed reactions of (E)-1,2-diph-
enylethenylboronic acid 1, which generates a 2-arylethenylrhodi-
⇑
Corresponding author. Tel.: +81 75 753 3983; fax: +81 75 753 3988.
E-mail address: thayashi@kuchem.kyoto-u.ac.jp (T. Hayashi).
0957-4166/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetasy.2012.03.004

374
K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
um intermediate by transmetallation of the alkenyl group, and
very recently we reported7 that the reaction of the boronic acid 1
with 2-cyclohexenone 2a in the presence of a diene/rhodium
catalyst gives 3-[2-((E)-2-phenylethenyl)phenyl]cyclohexanone
3a in a high yield (Scheme 2). The formation of rearranged product
3a is visualized by the catalytic cycle, which involves the 1,4-shift
of rhodium from 1,2-diphenylethenylrhodium(I) intermediate A to
2-(2-phenylethenyl)phenylrhodium(I) C via rhodium(III) interme-
diate B. The conjugate addition product 3-((E)-1,2-diphenylethe-
nyl)cyclohexanone 4a was not formed in this reaction.8 This
tandem 1,4-shift/conjugate addition of 1 was extended to asym-
metric reactions by using a chiral diene ligand and some of the
preliminary results have been also reported.7
Herein we report a full description of the asymmetric reaction
of cis-2-arylethenylboronic acids with ,b-unsaturated carbonyl
compounds catalyzed by chiral diene–rhodium complexes, where
ortho-alkenylphenyl groups are introduced with high enantioselec-
tivity by the tandem 1,4-shift/conjugate addition.
a
2. Results and discussion
We first examined (E)-1,2-diphenylethenylboronic acid 1,
which was readily prepared by a single step reaction from (Z)-stil-
bene according to procedures reported by O’Shea,9 for the addition
to 2-cyclohexenone 2a in the presence of a rhodium catalyst
(5 mol % Rh) in dioxane/H2O (20/1) (Table 1), which is a solvent
system often used for rhodium-catalyzed 1,4-addition reactions.1c
The use of [Rh(OH)(binap)]2, which is one of the most effective cat-
alysts for the asymmetric 1,4-addition,10 gave no addition products
in the reaction at 70 °C for 4 h. Enone 2a was recovered and boro-
nic acid 1 was hydrolyzed into (E)-stilbene (entry 1). The reaction
in the presence of rhodium/diene catalyst [Rh(OH)(cod)]2
(cod = 1,5-cyclooctadiene) gave the 1,4-shift/addition product 3a
as the major component over the direct addition product 4a (3a/
4a = 95/5) (entry 2). The 1,4-addition reaction was accelerated by
the addition of Cs2CO3 (1.5 equiv)11 to improve the yield of the
products (entry 3). The combination of [RhCl(cod)]2 and Cs2CO3
was also effective in the present reaction to give 3a+4a in 99% yield
and with high selectivity (3a/4a = 98/2) (entry 4). The rhodium
complexes coordinated with bicyclo[2.2.2]octa-2,5-diene (bod),
[RhCl(bod)]2, showed high catalytic activity and selectivity (98%
yield, 3a/4a = >99/1). Although the reactivity was decreased, high
selectivity was also observed with [RhCl(nbd)]2 (nbd = bicy-
clo[2.2.1]hepta-2,5-diene) and [RhCl(tfb)]2 (tfb = tetrafluoroben-
zobarrelene) (entries 6 and 7). Since the reaction was found to be
catalyzed effectively by rhodium/diene complexes, we began to
study the asymmetric variant of the tandem 1,4-shift/conjugate
addition using chiral diene ligands.12 The C2 symmetric dienes with
a bicyclo[2,2,2]octa-2,5-diene backbone (bod⁄),13 (R,R)-Ph-bod⁄
and (R,R)-Bn-bod⁄, gave 3a in a quantitative yield with excellent
(3a/4a = >99/1) selectivity. The enantioselectivity was high (95–
96% ee) with the bod⁄ ligands (entries 8 and 9). The reaction giving
3a also proceeded with high selectivity in the presence of rhodium
catalysts coordinated with the chiral dienes, (R)-L1, L2, and L3,
which are readily accessible from (R)-phellandrene7,14 (entries
10–12). The highest enantioselectivity (98.7% ee) was observed
O
O
[RhCl(bod)]2
(5 mol % Rh)
(HO)2B
Ph
+
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C, 4 h
Ph
1
2a
3a
98% yield
O
O
Rh OH
bod
Ph
4a
H
4
H
Rh
Rh
Rh
H
3
1
Ph
Ph
Ph
2
A
B
C
Scheme 2. A plausible pathway for the rhodium-catalyzed reaction of (E)-1,2-
diphenylethenylboronic acid.
Recent DFT calculations demonstrated7 that the 1,4-rhodium
shift occurs via C–H oxidative addition and reductive elimination
to/from a rhodium(III)-hydride intermediate (Fig. 1). The
D
G– for
alkenylrhodation from non-rearranged intermediate A (22.1 kcal/
mol) is significantly higher than that for the 1,4-rhodium shift
(19.5 kcal/mol), which is in good agreement with the experimen-
tally observed selectivity.
alkenylrhodation
enone
oxidative
addition
reductive
enone
arylrhodation
Ga'
binding
elimination
binding
Gb'
Db'
1,4-Rh shift
20
15
10
5
Da'
A'
B'
B
H
O
O
Rh
O
O
Rh
Ph
Ga
Db
Rh
Ph
Gb
Da
Ph
reference
structure
I
Ph
F
O
Ha
0
Ia
Ib
A
C
Rh
O
Ea
Rh
Rh
-5
Hb
Rh
Fb
Fa
Ph
Eb
Ph
Ph
Ph
Ph
H
E
-10
Figure 1. Energetic diagram of the 1,4-Rh shift and the two alternative carborhodation pathways before and after 1,4-Rh shift. The preferred pathway is shown in bold
(Rh = [Rh(bod)]).

K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
375
Table 1
(HO)2B
O
Rhodium-catalyzed addition of (E)-1,2-diphenylethenylboronic acid 1 to 2-cyclo-
hexenone 2aa
O
[RhCl(diene)]2
(5 mol % Rh)
Ph
5
+
(HO)2B
Ph
2.0 equiv
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C, 4 h
O
+
O
O
Ph
Ph
Rh-catalyst
1
(5 mol % Rh)
2.0 equiv
3a
4a
+
+
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C, 4 h
diene = (R)-L3
(S,S )-Fc-tfb*
O
92% yield
0% yield
98.1% ee (R)
2a
Ph
Ph
0.20 mmol
92% yield
0% yield
3a
4a
88% ee (R)
2a
Scheme 3. Asymmetric conjugate addition of 2-((E)-2-phenylethenyl)phenylbo-
ronic acid 5 to 2-cyclohexenone 2a catalyzed by chiral diene/rhodium complexes.
0.20 mmol
PPh2
PPh2
cod
nbd
binap
F
presence of [RhCl((R)-L3)]2 (5 mol % of Rh) gave 3a in 92% yield
as an exclusive product with 98.1% ee (Scheme 3). The reaction
of 5 with [RhCl((S,S)-Fc-tfb⁄)]2 catalyst also gave 3a (92% yield,
88% ee) exclusively. This is in contrast to the reaction of alkenylbo-
ronic acid 1 with the same catalyst (Table 1, entry 15), which gave
a mixture of 3a and 4a (3a/4a = 74/26). This may indicate that the
arylrhodation of enone 2a leading to 3a is much faster than the 1,4-
rhodium shift of arylrhodium intermediate C to alkenylrhodium A
in Scheme 2. An interesting feature is that the % ee of the main
product 3a is significantly higher in the reaction of 1 than in the
reaction of 5.
F
F
R = H: tfb
R
R = Ph: (R,R)-Ph-tfb*
R = CH2Ph: (R,R)-Bn-tfb*
R = ferrocenyl: (S,S)-Fc-tfb*
R
F
R = H: bod
R = Ph: (R,R)-Ph-bod*
R = CH2Ph: (R,R)-Bn-bod*
R
R
OAr =
O
O
O
O
OAr
Me
The asymmetric tandem 1,4-shift/conjugate addition also pro-
ceeded with high selectivity (>99/1) for the reaction of (E)-1,2-
di(4-methylphenyl)ethenylboronic acid 6, which gave the aryla-
tion product 7 in 95% yield with 99.2% ee (Eq. 1).
L1
L2
L3
(R)-
(R)-
(R)-
Entry
Rh-catalyst
Yieldb (%)
3a/4ac
ee of 3ad (%)
1e
2e
3
[Rh(OH)(binap)]2
[Rh(OH)(cod)]2
[Rh(OH)(cod)]2
[RhCl(cod)]2
[RhCl(bod)]2
[RhCl(nbd)]2
[RhCl(tfb)]2
[RhCl((R,R)-Ph-bod⁄)]2
[RhCl((R,R)-Bn-bod⁄)]2
[RhCl((R)-L1)]2
[RhCl((R)-L2)]2
[RhCl((R)-L3)]2
[RhCl((R,R)-Ph-tfb⁄)]2
[RhCl((R,R)-Bn-tfb⁄)]2
[RhCl((S,S)-Fc-tfb⁄)]2
0
66
93
99
98
49
50
99
99
99
97
99
52
52
62
—
95/5
98/2
98/2
>99/1
>99/1
>99/1
>99/1
>99/1
98/2
>99/1
>99/1
96/4
O
O
[RhCl((R)-L3)]2
Me
+
4
(HO)2B
(5 mol % Rh)
5f
Me
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C, 4 h
6
Ar
ð1Þ
7
Ar
Ar = 4-MeC6H4
8f
96 (R)
95 (R)
93 (R)
98.1 (R)
98.7 (R)
94 (R)
94 (R)
97 (R)
9f
7
6
2a
0.20 mmol
2.0 equiv
95% yield
10f
11f
12f
13
14
15
99.2% ee
In the addition of alkenylboronic acid 1 to (E)-1-phenyl-2-bu-
ten-1-one 2b, the selectivity in giving the tandem 1,4-shift/aryla-
tion product 3b or direct alkenylation product 4b was strongly
dependent on the diene ligand employed (Table 2). The reaction
catalyzed by [Rh(OH)(cod)]2 at 70 °C gave a mixture of 3a and 4b
in a 1/1 ratio (entry 1). The selectivity was shifted to the side of alk-
enylation product 4b by reducing the reaction temperature; for
example, the ratio of 3b/4b was 44/56 and 28/72 at the reaction
temperatures of 50 °C and 30 °C, respectively (entries 2 and 3).
Other rhodium complexes of achiral diene ligands, bod, nbd, and
tfb, showed the same high catalytic activity as the cod complex
at 70 °C to give 3b as the major product in a 3/2 ratio (entries 4–
6). The asymmetric reaction using the chiral diene, (R,R)-Ph-bod⁄,
gave the tandem 1,4-shift/arylation product 3b with high selectiv-
ity (3b/4b = 92/8) and high enantioselectivity (89% ee) (entry 7).
Both the 3b-forming chemoselectivity and the enantioselectivity
were increased by using chiral dienes, (R)-L2 and (R)-L3, with the
latter giving 3b with 97% chemoselectivity and 95% enantioselec-
tivity (entries 8 and 9). The chemoselectivity was reversed when
using chiral tfb⁄ ligands (entries 10 and 11). Thus, the alkenylation
product 4b was formed more than the 1,4-shift/arylation product
3b. The selectivity forming 3b/4b was 32/68 and 13/87 with
(R,R)-Ph-tfb⁄ and (S,S)-Fc-tfb⁄ complexes, respectively, and the
enantioselectivity was also high for both 3b and 4b. The highest
4b-selectivity was observed in the reaction catalyzed by the
(S,S)-Fc-tfb⁄ complex at the reaction temperature of 30 °C, where
4b was formed with 98% selectivity and 94% ee (entry 12).
98/2
74/26
a
The reaction was carried out with
(0.20 mmol), Cs2CO3 (0.30 mmol), and rhodium catalyst (0.010 mmol Rh, 5 mol %)
in dioxane/H2O (20/1, 1.05 mL).
1 (0.40 mmol), 2-cyclohexenone 2a
b
Combined isolated yield of 3a and 4a.
Determined by 1H NMR of the crude products.
c
d
Determined by chiral HPLC on a Chiralcel OD-H column. The absolute config-
uration of 3a was determined by correlation with a known compound [see Eq. (5)].
e
In the absence of Cs2CO3.
Reported in Ref. 7
f
with the chiral diene (R)-L3 which has a bulky ester group (entry
12). Chiral diene ligands based on tetrafluorobenzobarrelene
(tfb),15 (R,R)-Ph-tfb⁄ and (R,R)-Bn-tfb⁄, were less effective than
the corresponding bod⁄ derivatives in terms of catalytic activity
and the 3a selectivity (entries 13 and 14). The proportion of the di-
rect alkenylation product 4a to all of the products 3a and 4a was
increased to 26% with (S,S)-Fc-tfb⁄ (Fc = ferrocenyl) as the ligand
(entry 15). Although the alkenylation product 4a was always a
minor product in the reaction of 2a, a higher selectivity in giving
the alkenylation product was observed with (S,S)-Fc-tfb⁄ ligand
in the reaction of a linear enone (vide infra).
The reaction of 2-cyclohexenone 2a with 2-((E)-2-phenylethe-
nyl)phenylboronic acid 5 instead of alkenylboronic acid 1 in the

376
K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
Table 2
intermediates present in the catalytic cycle (Eqs. (2)–(4)). The deu-
terodeborylation of boronic acid 1 in D2O in the presence of rho-
dium/(R)-L3 catalyst gave, in high yield, (E)-stilbene 8, which
was incorporated with 57% of D at the ortho-position of one of
the phenyl groups, but not at the alkenyl carbon (Eq. 2), thus indi-
cating that the alkenylrhodium intermediate A (Scheme 2) under-
goes the 1,4-rhodium shift very rapidly giving arylrhodium
intermediate C. This was in good agreement with the experimental
results observed for the reaction of 1 with 2b with the rhodium/L3
catalyst (entry 9 in Table 2) where the conjugate addition products
were mostly arylation product 3b (3b/4b = 97/3). The low content
of D in total may result from the use of H-containing boronic acid
[RB(OH)2], which makes the total concentration of D lower. The D
incorporation was observed to some extent on both the ortho-phe-
nyl and alkenyl carbons in (E)-stilbene 8 generated in the reaction
catalyzed by the rhodium/bod complex (Eq. 3), and the rhodium/
Fc-tfb⁄ catalyst gave (E)-stilbene 8, which is incorporated with D
on the alkenyl carbon more than on the ortho-phenyl carbon (Eq.
4). These deuterium incorporating proportions are in good agree-
ment with the results obtained for the addition of 1 to enone 2b
in the presence of rhodium/bod (entry 4 in Table 2) and rho-
dium/Fc-tfb⁄ catalysts (entry 11 in Table 2). With Fc-tfb⁄ as the li-
gand, the alkenylrhodium intermediate A does not readily undergo
the 1,4-rhodium shift, but it reacts with the enone or proton at the
original alkenyl position. Thus, the selectivity for the 1,4-shift or
carborhodation to the enone is strongly dependent on the ligand
on the 2-arylethenylrhodium intermediates.
Rhodium-catalyzed addition of (E)-1,2-diphenylethenylboronic acid
1
to (E)-1-
phenyl-2-buten-1-one 2ba
(HO)2B
Ph
O
1
2.0 equiv
O
Me
[RhCl(diene)]2
(5 mol % Rh)
Ph
+
+
Ph
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
14 h
O
Me
Ph
Ph
Ph
3b
4b
Me
2b
0.20 mmol
Entry
Diene
Temp. (°C)
Yieldb (%)
3b/4bc
eed (%)
3b
4b
1
2
3
4
5
6
7
8
cod
cod
cod
bod
nbd
tfb
70
50
30
70
70
70
70
70
70
70
70
30
95
97
99
98
93
96
95
96
96
62
99
99
51/49
44/56
28/72
64/36
62/38
65/35
92/8
96/4
97/3
32/68
13/87
2/98
(R,R)-Ph-bod⁄
89
92
95
89
92
(R)-L2
(R)-L3
9e
10
11
12
(R,R)-Ph-tfb⁄
(S,S)-Fc-tfb⁄
(S,S)-Fc-tfb⁄
85
91
94
a
The reaction was carried out with 1 (0.40 mmol), (E)-1-phenyl-2-buten-1-one
2b (0.20 mmol), Cs2CO3 (0.30 mmol), and rhodium catalyst (0.010 mmol Rh,
5 mol %) in dioxane/H2O (20/1, 1.05 mL).
57% D
<2% D
b
Combined isolated yield of 3b and 4b.
c
Determined by 1H NMR of the crude products.
[RhCl((R)-L3)]2
D/H
d
Determined by chiral HPLC on a Chiralpak AD-H column.
Reported in Ref. 7
(5 mol % Rh)
(HO)2B
Ph
H
ð2Þ
ð3Þ
ð4Þ
e
Cs2CO3 (1.5 equiv)
dioxane/D2O (20/1)
70 °C, 4 h
Ph
8
-d1
1
The reaction of 2-((E)-2-phenylethenyl)phenylboronic acid 5
with linear enone 2b in the presence of L3– or Fc-tfb⁄–rhodium
complex proceeded without a 1,4-shift from an arylrhodium to
an alkenylrhodium to give a high yield of the direct arylation prod-
uct 3b (Scheme 4). The same perfect arylation selectivity was also
observed in the reaction of cyclic enone 2a (see, Scheme 3). These
results indicate that the 1,4-shift from arylrhodium to alkenylrho-
dium does not take place, or is not visible in the addition products
under the present reaction conditions, while the 1,4-rhodium shift
in the other direction, from alkenylrhodium to arylrhodium inter-
mediates, is a process which does take place and decides the ratio
of the addition products.
94% yield
0.20 mmol
57% D
14% D
D/H
H/D
[RhCl(bod)]2
1 (0.20 mmol)
Ph
8-d1
84% yield
18% D
51% D
H/D
[RhCl((S,S)-Fc-tfb*)]2
D/H
1
(0.20 mmol)
Ph
8-d1
Alkenylboronic acid 1 was subjected to the present reaction
conditions in the absence of enones, which produced (E)-stilbene
by the rhodium-catalyzed protodeborylation. The reaction in D2O
gave us a significant insight into the alkenyl- and arylrhodium
94% yield
As illustrated in Table 3, the present asymmetric reaction is
applicable to a broad range of ,b-unsaturated carbonyl com-
a
pounds. In the presence of 5 mol % of the rhodium/(R)-L3 catalyst,
2-cyclopentenone 2c and 2-cycloheptenone 2d underwent the tan-
dem 1,4-shift/addition with high 3-selectivity to give the corre-
sponding arylated ketones with 95–96% enantioselectivity
(entries 2 and 3). The 3/4 selectivity and enantioselectivity were
slightly dependent on the electronic characters of the substituents
on the phenyl group of linear phenyl ketones 2b, 2e, and 2f (entries
4–6). The 3-selectivity is higher with a 4-methoxy group 2e while
the enantioselectivity is higher with a 4-trifluoromethyl group 2f.
The addition to linear enones 2g, 2h, and 2i, which possess a
methyl ketone, resulted in a low yield of the corresponding
arylation products 3 due to their low reactivity and low chemose-
lectivity, but the enantioselectivities were generally high (97–99%
ee) (entries 7–9). The present asymmetric tandem 1,4-shift/addi-
(HO)2B
Ph
O
5
[RhCl(diene)]2
(5 mol % Rh)
O
Me
2.0 equiv
Ph
+
+
Ph
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C
O
Me
Ph
Ph
Ph
3b
95% yield
4b
Me
2b
0.20 mmol
diene = cod
0% yield
0% yield
L3
(R)-
98% yield
99.3% ee (S)
96% yield
0% yield
(S,S)-Fc-tfb*
98.7% ee (S)
tion was applied to cyclic and linear
and 2k, but the enantioselectivity was slightly lower (entries 10
and 11).
a,b-unsaturated esters 2j
Scheme 4. Asymmetric conjugate addition of 2-((E)-2-phenylethenyl)phenylbo-
ronic acid 5 to (E)-1-phenyl-2-buten-1-one 2b catalyzed by chiral diene/rhodium
complexes.

K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
377
Table 3
to an ortho-alkenylphenylrhodium intermediate. In the reaction of
1 with (E)-1-phenyl-2-buten-1-one, the selectivity in forming the
tandem 1,4-shift/arylation product or the direct alkenylation prod-
uct was strongly dependent upon the chiral diene ligands em-
ployed, and either of the products could be selectively obtained
by a proper choice of the chiral diene ligand.
Rhodium/diene-catalyzed asymmetric addition of 1 to enones or enoates 2a
O
[RhCl((R)-L3)]2
(5 mol % Rh)
O
(HO)2B
Ph
+
*
Cs2CO3 (1.5 equiv)
dioxane/H2O (20/1)
70 °C, 4 h
Ph
O
1
2a-k
0.20 mmol
4. Experimental
4.1. General
3a-k
2.0 equiv
O
O
O
Ar
All anaerobic and moisture-sensitive manipulations were car-
ried out with standard Schlenk techniques under predried nitrogen
or glovebox techniques under argon. NMR spectra were recorded
on a JEOL JNM LA-500 spectrometer (500 MHz for 1H NMR and
125 MHz for 13C NMR). Chemical shifts are reported in d ppm ref-
erenced to chloroform-d (d 7.26 for 1H NMR and d 77.16 for 13C
NMR) and DMSO-d6 (d 2.50 for 1H NMR and d 39.52 for 13C
NMR): the following abbreviations are used; d: doublet, t: triplet,
q: quartet, quint: quintet, sext: sextet, oct: octet, m: multiplet.
Optical rotations were measured on a JASCO P-2200 polarimeter.
High-resolution mass spectra were obtained with a Bruker micrO-
TOF spectrometer. THF and Dioxane were purified by passing
through a neutral alumina column under nitrogen atmosphere.
Rhodium complexes, [Rh(OH)(binap)]2,10 [Rh(OH)(cod)]2,18
[RhCl(cod)]2,19 [RhCl(bod)]2,20 [RhCl(nbd)]2,21 [RhCl(tfb)]2,22 [RhCl
((R,R)-Ph-bod⁄)]2,13b [RhCl((R,R)-Bn-bod⁄)]2,23 [RhCl((R)-L1)]2,24
[RhCl((R)-L2)]2,25 [RhCl((R)-L3)]2,7 [RhCl((R,R)-Ph-tfb⁄)]2,15 [RhCl
Me
2a
2c
2d
2b: A r= Ph
2e
: Ar = 4-MeOC6H4
2f
: Ar = 4-F3CC6H4
O
O
O
Me
MeO
O
R1
Me
2g: R1 = Me
2j
2k
2h: R1 = C5H11
2i: R1 = i-Pr
Entry
2
Yield of 3b (%)
3/4c
ee of 3d (%)
1e
2e
3e
4e
5
2a
2c
2d
2b
2e
2f
2g
2h
2i
99
95
83
93
95
88
71
65
73
78
82
>99/1
98/2
98/2
97/3
98/2
90/10
79/21
83/17
98/2
>99/1
91/9
99 (R)
96 (R)
95 (R)
95 (S)
94 (S)
96 (S)
97 (S)
98 (S)
99 (R)
92 (R)
84 (S)
6
((R,R)-Bn-tfb⁄)]2,15 and [RhCl((S,S)-Fc-tfb⁄)]2 were prepared by
15
7
8f
following literature procedures. (E)-1,2-Diphenylethenylboronic
acid 19 was prepared by following the literature procedures. The
starting enone 2b was purchased and purified by column chroma-
tography on silica gel (hexane/EtOAc = 20/1). Enones 2e26 and 2f27
were prepared according to the reported procedures. All other
materials were purchased and used without purification.
9e,f
10
11f
2j
2k
a
The reaction was carried out with
1
(0.40 mmol), 2 (0.20 mmol), Cs2CO3
(0.30 mmol), and [RhCl((R)-L3)]2 (0.010 mmol Rh, 5 mol %) in dioxane/H2O (20/1,
1.05 mL) at 70 °C for 4 h.
b
Isolated yields.
Determined by 1H NMR of the crude products.
c
d
4.2. Preparation of organoboronic acids
Determined by HPLC analysis with chiral HPLC columns. The absolute config-
urations of 3a and 3c were determined by correlation with known compounds (see
(Eq. 5)), while the others are assigned by analogy of the stereochemical pathway.
4.2.1. 2-((E)-2-Phenylethenyl)phenylboronic acid 5
e
Reported in Ref. 7
f
The reaction was carried out with 0.60 mmol of 1 for 12 h.
n-BuLi
B(Oi-Pr)3
Br
(HO)2B
Ph
(1.5 equiv)
1N HCl
rt
(3.0 equiv)
THF
-78°C to rt
The absolute configurations of the asymmetric arylation prod-
ucts 3a and 3c were determined to be (R) by correlation with
known compounds (Eq. 5). Thus, the oxidative cleavage of the
ortho-styryl moiety of 3 with ozone gave aldehydes 9. The formyl
group was removed by iridium-catalyzed decarbonylation leading
to the known compounds 10a16 and 10c.17
Ph
-78 °C, 30 min
S1
5
To a solution of S128 (966 mg, 3.7 mmol) in THF (20 mL)
cooled to ꢀ78 °C, was added n-BuLi (3.5 mL, 1.62 M in hexane)
dropwise, and the reaction mixture was stirred at ꢀ78 °C for
30 min. Triisopropoxyborane (2.6 mL, 11.2 mmol) was added,
and the mixture was allowed to warm to room temperature
and stirred overnight. The reaction mixture was quenched with
1 M HCl and stirred at room temperature for 1 h, before it was
concentrated on a rotary evaporator. The residue was extracted
with CH2Cl2. The combined organic layer was washed with brine,
dried over MgSO4, filtered, and concentrated under vacuum to
give 5 (658 mg, 2.9 mmol, 79% yield). 1H NMR (DMSO-d6): d
7.12 (d, J = 16.3 Hz, 1H), 7.23 (t, J = 6.4 Hz, 1H), 7.26 (t,
J = 7.3 Hz, 1H), 7.37 (t, J = 6.8 Hz, 1H), 7.38 (t, J = 7.4 Hz, 2H),
7.51 (d, J = 7.7 Hz, 3H), 7.63 (d, J = 16.4 Hz, 1H), 7.74 (d,
O
Ph
O
O
1) O3
2) Me2S
[IrCl(cod)]2/PPh3
(10 mol % Ir)
CHO
dioxane, reflux
CH2Cl2
( )n
( )n
( )n
ð5Þ
Ph
3a (n=1): 99% ee
3c (n=0): 96% ee
9a (n=1)
9c (n=0)
10a (n=1): 99% ee (R)
10c (n=0): 96% ee (R)
3. Conclusion
We have studied the reaction of (E)-1,2-diphenylethenylboronic
acid 1 with ,b-unsaturated ketones in the presence of a chiral
J = 7.8 Hz, 1H), 8.23 (s, 2H). 13C NMR (DMSO-d6):
d 124.4,
a
126.4, 126.6, 127.6, 128.4, 128.8, 129.1, 130.1, 133.6, 137.6,
140.3. The boron-bound carbon was not detected due to quadru-
polar relaxation. HRMS (ESI) calcd for C14H13BNaO2 (M+Na)+
247.0903, found 247.0907.
diene/rhodium catalyst. The reaction with 2-cyclohexenone pro-
ceeded selectively to give a high yield of 3-[2-((E)-2-phenylethe-
nyl)phenyl]cyclohexanone with 98.7% ee, where the catalytic
cycle involved a 1,4-rhodium shift from a 2-phenylethenylrhodium

378
K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
4.2.2. (E)-1,2-Di(4-methylphenyl)ethenylboronic acid 6
4.3. Typical procedure for the rhodium-catalyzed asymmetric
1,4-addition (entry 12 in Table 1)
To a solution of [RhCl((R)-L3)]2 (5.0 mg, 10 lmol of Rh, 5 mol %
Rh), Cs2CO3 (97.7 mg, 0.30 mmol), and (E)-1,2-diphenylethenylbo-
ronic acid 1 (89.6 mg, 0.40 mmol) in dioxane (1.0 mL) was added 2-
cyclohexenone 2a (19.2 mg, 0.20 mmol) and H2O (50 lL). After
stirring at 70 °C for 4 h, the reaction mixture was diluted with
Et2O (1.0 mL), and filtered through a pad of silica gel. The plug
was washed with Et2O (30 mL) and the combined filtrates were
concentrated on a rotary evaporator. The residue was purified by
preparative TLC on silica gel with hexane/EtOAc (3/1) to give 3a
(54.5 mg, 99% yield). The data for 3a, 3b, 3c, 3d, and 3i have already
been reported.7
Br2
DBU
Br
Br
(1.1 equiv)
(2.0 equiv)
Ar
Ar
Ar
Ar
Ar
CHCl3
benzene
Ar
reflux, 1 h
0°C, 30 min
Br
S2
S3
t-BuLi
B(OMe)3
(HO)2B
(1.9 equiv)
1N HCl
(3.0 equiv)
Ar
THF
-78°C, 2 h;
rt
Ar
-78°C, 30 min;
then rt
(Ar = 4-MeC6H4)
then -40 °C, 2 h
6
At first, S2 (CAS: (E) 18869-29-9, (Z) 2510-76-1, non-specified
1588-49-4) was prepared from 4-methylbenzaldehyde via a Wit-
tig-reaction with 4-methylbenzyltriphenylphosphonium bromide
using NaHMDS29 as the base.
To a solution of S2 (3.32 g, 15.9 mmol) in CHCl3 (50 mL) was
added dropwise a solution of bromine (0.90 mL, 17.5 mmol) in
CHCl3 (10 mL) at 0 °C over a period of 30 min. The reaction mixture
was quenched with a saturated aqueous solution of Na2S2O3. The
aqueous layer was then extracted with CHCl3. The combined or-
ganic layer was washed with a saturated aqueous solution of
Na2S2O3, dried over MgSO4, filtered, and concentrated under vac-
uum. The crude product was used for the next reaction without
further purification.
To a solution of the dibromoalkane obtained above in ben-
zene (20 mL) was added DBU (1,8-diazabicyclo[5.4.0]undec-7-
ene) (4.8 mL, 31.8 mmol). The mixture was heated for 1 h
at reflux. After cooling to room temperature, the mixture
was diluted with H2O and extracted with Et2O. The combined
organic layer was washed with brine, dried over MgSO4,
filtered, and concentrated under vacuum. The residue was
subjected to column chromatography on silica gel (hexane)
to give the desired alkenyl bromide S3 (major isomer/minor
isomer = 71/29, 3.29 g, 11.4 mmol, 72% yield for 2 steps). 1H
4.3.1. (R)-3-[5-Methyl-2-((E)-2-(4-methylphenyl)ethenyl)
phenyl]cyclohexanone 7
95% yield, 99.2% ee (Eq. 1). The ee was determined on a Daicel
Chiralpak AD-H column with hexane/2-propanol = 90/10, flow =
0.5 mL/min, wavelength = 254 nm. Retention times: 15.0 min
[(S)-enantiomer], 15.7 min [(R)-enantiomer].
½
a 2D0
ꢁ
¼ þ138:9 (c
0.57, CHCl3). 1H NMR (CDCl3): d 1.81 (qdd, J = 12.4, 4.5, 3.2 Hz,
1H), 1.87 (qd, J = 12.4, 3.0 Hz, 1H), 2.04-2.08 (m, 1H), 2.16 (tt,
J = 9.6, 3.3 Hz, 1H), 2.371 (s, 3H), 2.375 (s, 3H), 2.42 (td, J = 12.0,
6.3 Hz, 1H), 2.48-2.52 (m, 1H), 2.54-2.63 (m, 2H), 3.40 (tdd,
J = 11.2, 5.0, 3.5 Hz, 1H), 6.90 (d, J = 16.0 Hz, 1H), 7.08 (d,
J = 7.8 Hz, 1H), 7.09 (s, 1H), 7.18 (d, J = 7.9 Hz, 2H), 7.27 (d,
J = 15.9 Hz, 1H), 7.39 (d, J = 8.0 Hz, 2H), 7.48 (d, J = 7.8 Hz, 1H).
13C NMR (CDCl3): d 21.4, 21.5, 25.7, 32.5, 40.2, 41.4, 48.5, 124.6,
126.2, 126.6, 126.8, 127.7, 129.6, 131.0, 133.3, 134.9, 137.70,
137.73, 141.5, 211.2. HRMS (ESI) calcd for C22H24NaO (M+Na)+
327.1719, found 327.1719.
4.3.2. (S,E)-3-Methyl-1,4,5-triphenylpent-4-en-1-one 4b
98% yield, 94% ee (entry 12 in Table 2). The ee was determined on
NMR (CDCl3): major isomer
d 2.27 (s, 3H), 2.38 (s, 3H),
a
Daicel Chiralpak AD-H column with hexane/2-propanol =
98/2, flow = 0.5 mL/min, wavelength = 254 nm. Retention times:
15.6 min [(R)-enantiomer], 17.5 min [(S)-enantiomer].
6.90 (d, J = 8.2 Hz, 2H), 6.97 (d, J = 8.2 Hz, 2H), 7.13 (s, 1H),
7.14 (d, J = 8.2 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H); minor isomer
d 2.40 (s, 3H), 2.41 (s, 3H), 7.18 (s, 1H), 7.20 (d, J = 8.0 Hz,
2H), 7.23 (d, J = 8.2 Hz, 2H), 7.57 (d, J = 8.2 Hz, 2H), 7.64 (d,
J = 8.0 Hz, 2H). 13C NMR (CDCl3): d 21.28, 21.33, 21.5, 122.9,
123.5, 127.8, 128.7, 129.0, 129.05, 129.13, 129.2, 129.27,
129.30, 129.4, 132.7, 133.5, 133.7, 136.9, 137.4, 138.0,
138.5, 138.8, 138.9 (1 carbon is missing due to overlap).
½
a 2D0
ꢁ
¼
ꢀ23:1 (c 1.13, CHCl3). 1H NMR (CDCl3): d 1.22 (d, J = 7.1 Hz, 3H),
2.85 (dd, J = 16.3, 8.0 Hz, 1H), 3.09 (dd, J = 16.3, 6.2 Hz, 1H), 3.91
(sext, J = 7.0 Hz, 1H), 6.47 (s, 1H), 7.23-7.27 (m, 1H), 7.29–7.38 (m,
11H), 7.49 (tt, J = 7.4, 1.4 Hz, 1H), 7.74 (d, J = 7.2 Hz, 2H). 13C NMR
(CDCl3): d 20.4, 31.3, 44.4, 126.8, 127.0, 128.0, 128.1, 128.4, 128.6,
128.9, 129.0, 129.9, 132.9, 137.2, 137.8, 142.5, 147.3, 199.2. HRMS
(ESI) calcd for C24H22NaO (M+Na)+ 349.1563, found 349.1564.
HRMS (APCI) calcd for
286.0350.
C
16H15Br (M)+ 286.0352, found
A solution of S3 (1.44 g, 5.0 mmol) in THF (50 mL) was cooled
to ꢀ78 °C, and t-BuLi (5.9 mL, 1.61 M in pentane) was added
dropwise. The reaction mixture was stirred at ꢀ78 °C for 1 h
and then at ꢀ40 °C for 2 h. To the reaction mixture cooled to
ꢀ78 °C, was added trimethoxyborane (1.7 mL, 15.0 mmol), and
the mixture was stirred at ꢀ78 °C for 2 h. The reaction mixture
was then allowed to warm to room temperature. The reaction
mixture was quenched with 1 M HCl, before it was stirred at
room temperature for 1 h and then concentrated on a rotary
evaporator. The residue was extracted with CH2Cl2. The combined
organic layer was washed with brine, dried over MgSO4, filtered,
and concentrated under vacuum. Re-precipitation with CH2Cl2
and hexane provided 6 (363 mg, 1.4 mmol, 29% yield). 1H NMR
(CDCl3): d 2.36 (s, 6H), 4.55 (s, 2H), 7.17 (d, J = 7.9 Hz, 4H), 7.22
(s, 1H), 7.32 (d, J = 7.9 Hz, 2H), 7.34 (d, J = 6.8 Hz, 2H). 13C NMR
(CDCl3): d 21.3, 21.4, 127.1, 128.0, 129.5, 135.5, 137.2, 138.1,
139.2, 139.4 (1 carbon is missing due to overlap). The boron-
bound carbon was not detected due to quadrupolar relaxation.
HRMS (ESI) calcd for C16H17BNaO2 (M+Na)+ 275.1217, found
275.1213.
4.3.3. (S)-1-(4-Methoxyphenyl)-3-[2-((E)-2-phenylethenyl)
phenyl]butan-1-one 3e
95% yield, 94% ee (entry 5 in Table 3). The ee was determined on
a
Daicel Chiralpak AD-H column with hexane/2-propanol
= 2/1, flow = 0.5 mL/min, wavelength = 254 nm. Retention times:
15.0 min [(R)-enantiomer], 18.8 min [(S)-enantiomer].
½
a 2D0
ꢁ
¼
ꢀ102:2 (c 1.08, CHCl3). 1H NMR (CDCl3): d 1.34 (d, J = 6.9 Hz, 3H),
3.09 (dd, J = 15.9, 8.9 Hz, 1H), 3.25 (dd, J = 15.8, 5.0 Hz, 1H), 3.83
(s, 3H), 3.94 (dqd, J = 8.7, 6.8, 5.2 Hz, 1H), 6.85 (d, J = 8.8 Hz, 2H),
6.95 (d, J = 15.8 Hz, 1H), 7.21-7.38 (m, 6H), 7.51 (d, J = 7.8 Hz,
2H), 7.55 (d, J = 16.3 Hz, 1H), 7.57 (d, J = 7.7 Hz, 1H), 7.92 (d,
J = 8.9 Hz, 2H). 13C NMR (CDCl3): d 21.3, 31.2, 46.7, 55.6, 113.9,
125.8, 126.5, 126.66, 126.73, 126.8, 127.8, 128.1, 128.8, 130.3,
130.6, 131.4, 136.1, 137.7, 144.4, 163.6, 197.8. HRMS (ESI) calcd
for C25H24NaO2 (M+Na)+ 379.1669, found 379.1665.
4.3.4. (S)-1-[4-(Trifluoromethyl)phenyl]-3-[2-((E)-2-phenyl-
ethenyl)phenyl]butan-1-one 3f
88% yield, 96% ee (entry 6 in Table 3). The ee was determined on a
Daicel Chiralpak AD-H column with hexane/2-propanol = 2/1,

K. Sasaki, T. Hayashi / Tetrahedron: Asymmetry 23 (2012) 373–380
379
flow = 0.5 mL/min,
wavelength = 254 nm.
Retention
times:
¼ ꢀ80:9
J = 15.2, 8.7 Hz, 1H), 2.70 (dd, J = 15.2, 6.1 Hz, 1H), 3.63 (s, 3H),
3.76 (dquint, J = 8.5, 6.7 Hz, 1H), 6.97 (d, J = 16.0 Hz, 1H), 7.22–7.29
(m, 4H), 7.38 (t, J = 7.7 Hz, 2H), 7.54 (d, J = 15.9 Hz, 1H), 7.55 (d,
J = 7.7 Hz, 2H), 7.58 (d, J = 7.5 Hz, 1H). 13C NMR (CDCl3): d 21.4,
31.6, 42.3, 51.7, 125.5, 126.3, 126.6, 126.7, 126.8, 127.8, 128.1,
128.8, 131.4, 136.0, 137.7, 143.3, 172.9. HRMS (ESI) calcd for
11.3 min [(R)-enantiomer], 15.5 min [(S)-enantiomer]. ½a D20
ꢁ
(c 0.92, CHCl3). 1H NMR (CDCl3): d 1.37 (d, J = 6.8 Hz, 3H), 3.16 (dd,
J = 16.3, 8.6 Hz, 1H), 3.34 (dd, J = 16.2, 5.2 Hz, 1H), 3.94 (dqd, J = 8.4,
6.9, 5.6 Hz, 1H), 6.94 (d, J = 16.0 Hz, 1H), 7.23-7.33 (m, 4H), 7.37 (d,
J = 7.6 Hz, 2H), 7.50 (d, J = 6.6 Hz, 2H), 7.51 (d, J = 16.3 Hz, 1H), 7.57
(d, J = 7.1 Hz, 1H), 7.63 (d, J = 8.0 Hz, 2H), 8.00 (d, J = 8.1 Hz, 2H). 13
C
C
19H20NaO2 (M+Na)+ 303.1356, found 303.1353.
NMR (CDCl3): d 21.2, 30.9, 47.3, 123.7 (q, J = 272 Hz), 125.7, 125.8
(q, J = 3.8 Hz), 126.4, 126.8, 126.9, 127.9, 128.2, 128.6, 128.9, 131.7,
134.4 (q, J = 32.7 Hz), 136.1, 137.6, 139.8 (q, J = 1.2 Hz), 143.8, 198.3
(1 carbon is missing due to overlap). HRMS (ESI) calcd for
4.4. Conversion of 3c into 10c by way of 9c
The experimental procedures for the conversion of 3a to 10a
have already been reported.7 In a similar manner, 3c was converted
into 10c via 9c.
C
25H21F3NaO (M+Na)+ 417.1437, found 417.1433.
4.3.5. (S)-4-[2-((E)-2-Phenylethenyl)phenyl]pentan-2-one 3g
71% yield, 97% ee (entry 7 in Table 3). The ee was determined
on a Daicel Chiralpak AD-H column with hexane/2-propanol =
98/2, flow = 0.5 mL/min, wavelength = 254 nm. Retention times:
4.4.1. (R)-2-(3-Oxocyclopentyl)benzaldehyde 9c
½
a 2D0
ꢁ
¼ þ28:3 (c 0.92, CHCl3). 1H NMR (CDCl3): d 2.02 (dtd,
J = 11.5, 9.9, 8.2 Hz, 1H), 2.32-2.49 (m, 4H), 2.70 (dd, J = 18.0,
7.9 Hz, 1H), 4.52 (tdd, J = 10.2, 7.6, 6.1 Hz, 1H), 7.45 (d, J = 7.8 Hz,
1H), 7.47 (td, J = 7.4, 1.2 Hz, 1H), 7.60 (td, J = 7.6, 1.5 Hz, 1H), 7.84
(dd, J = 7.6, 1.5 Hz, 1H), 10.23 (s, 1H). 13C NMR (CDCl3): d 30.8,
37.2, 38.7, 45.4, 126.5, 127.2, 134.0, 134.3, 135.0, 145.2, 193.2,
218.1. HRMS (ESI) calcd for C12H12NaO2 (M+Na)+ 211.0730, found
211.0734.
18.9 min [(S)-enantiomer], 20.0 min [(R)-enantiomer].
½
a 2D0
ꢁ
¼
ꢀ18:9 (c 0.83, CHCl3). 1H NMR (CDCl3): d 1.28 (d, J = 7.0 Hz, 3H),
2.09 (s, 3H), 2.68 (dd, J = 16.7, 8.4 Hz, 1H), 2.80 (dd, J = 16.7, 5.6 Hz,
1H), 3.79 (sext, J = 6.9 Hz, 1H), 6.95 (d, J = 16.1 Hz, 1H), 7.20-7.29
(m, 4H), 7.37 (t, J = 7.7 Hz, 2H), 7.52 (d, J = 16.2 Hz, 1H), 7.53 (d,
J = 7.1 Hz, 2H), 7.57 (d, J = 7.5 Hz, 1H). 13C NMR (CDCl3): d 21.5,
30.5, 30.7, 51.6, 125.6, 126.3, 126.6, 126.7, 126.8, 127.8, 128.1,
128.9, 131.4, 136.0, 137.7, 143.9, 207.7. HRMS (ESI) calcd for
4.4.2. (R)-3-Phenylcyclopentanone 10c
[CAS: 86505-44-4 for the (R)-enantiomer]: 62% yield, 96% ee. The
ee was determined on a Daicel Chiralcel OB-H column with hexane/
2-propanol = 100/1, flow = 1.0 mL/min, wavelength = 210 nm.
Retention times: 24.8 min [(S)-enantiomer], 26.3 min [(R)-enantio-
C
19H20NaO (M+Na)+ 287.1406, found 287.1410.
4.3.6. (S)-4-[2-((E)-2-Phenylethenyl)phenyl]nonan-2-one 3h
65% yield, 98% ee (entry 8 in Table 3). The ee was determined on
two Daicel Chiralcel OJ-H columns with hexane/2-propanol
= 95/5, flow = 0.5 mL/min, wavelength = 254 nm. Retention times:
mer]. ½a 2D0
ꢁ
¼ þ79:1 (c 0.40, CHCl3); cf. ½a D20
¼ þ83:9 (c 0.93, CHCl3)
ꢁ
for the (R)-enantiomer.17,30
37.8 min [(S)-enantiomer], 45.3 min [(R)-enantiomer].
½
a 2D0
ꢁ
¼
Acknowledgments
ꢀ7:4 (c 0.87, CHCl3). 1H NMR (CDCl3): d 0.78–0.81 (m, 3H), 1.12–
1.26 (m, 6H), 1.60–1.65 (m, 2H), 2.04 (s, 3H), 2.72 (dd, J = 16.5,
6.9 Hz, 1H), 2.78 (dd, J = 16.4, 7.1 Hz, 1H), 3.67 (quint, J = 6.9 Hz,
1H), 6.93 (d, J = 16.0 Hz, 1H), 7.19–7.23 (m, 2H), 7.25–7.29 (m,
2H), 7.38 (t, J = 7.7 Hz, 2H), 7.54 (d, J = 7.2 Hz, 2H), 7.56 (d,
J = 7.2 Hz, 1H), 7.58 (d, J = 15.6 Hz, 1H). 13C NMR (CDCl3): d 14.1,
22.6, 27.1, 30.7, 32.0, 35.7, 36.5, 50.8, 126.2, 126.4, 126.7, 126.8,
126.9, 127.7, 128.0, 128.8, 131.2, 136.9, 137.8, 142.7, 207.9. HRMS
(ESI) calcd for C23H28NaO (M+Na)+ 343.2032, found 343.2032.
This work has been supported by a Grant-in-Aid for Scientific
Research (S) (19105002), from the MEXT, Japan. K.S. thanks the
JSPS for a Young Scientists research fellowship.
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4.3.7. (R)-4-[2-((E)-2-Phenylethenyl)phenyl]tetrahydro-2H-
pyran-2-one 3j
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Retention
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a 2D0
ꢁ
¼
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½
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3k
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