Rhodium-catalyzed asymmetric 1,4-addition of alkenylsilanes generated by hydrosilylation of alkynes: A one-pot procedure where a rhodium/(S)-binap complex catalyzes the two successive reactions

Article abstract of DOI:10.1016/j.tetasy.2004.07.003

A rhodium complex [Rh((S)-binap)(MeCN)₂]BF₄ (3 mol %) catalyzes successively hydrosilylation of 1-alkynes with triethoxysilane and asymmetric 1,4-addition of the resulting alkenylsilanes to cyclic α,β-unsaturated ketones. This one-pot procedure gave high yield of the corresponding 1,4-addition products with over 90% enantioselectivity.

Full text of DOI:10.1016/j.tetasy.2004.07.003

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 2647–2651
Rhodium-catalyzed asymmetric 1,4-addition of
alkenylsilanes generated by hydrosilylation of alkynes: a
one-pot procedure where a rhodium/(S)-binap complexcatalyzes
the two successive reactions
Yusuke Otomaru and Tamio Hayashi*
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
Received 18 June 2004; accepted 5 July 2004
Available online 3 August 2004
Abstract—A rhodium complex [Rh((S)-binap)(MeCN)2]BF4 (3mol%) catalyzes successively hydrosilylation of 1-alkynes with tri-
ethoxysilane and asymmetric 1,4-addition of the resulting alkenylsilanes to cyclic a,b-unsaturated ketones. This one-pot procedure
gave high yield of the corresponding 1,4-addition products with over 90% enantioselectivity.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
cyclohexenone 1a proceeds in dioxane/H2O at 90°C in
the presence of a cationic binap–rhodium catalyst gener-
ated in situ from [Rh(cod)(MeCN)2]BF4 (4mol%) and
binap (6mol%) to give 85% yield of the 1,4-addition
product 3am with 91% ee. In our hands, the use of iso-
lated phosphine–rhodium complex [Rh((S)-bin-
ap)(MeCN)2]BF4 (3mol%) gave slightly higher
enantioselectivity (94% ee), although the yield of 3am
was lower (70% yield). Higher yields (89%) of 3am with
the same enantioselectivity were obtained in the reaction
carried out in the presence of 1mol% of (S)-binap ligand
and 3mol% of [Rh((S)-binap)(MeCN)2]BF4 (Scheme 1).
Rhodium-catalyzed asymmetric 1,4-addition of organo-
metallic reagents provides an efficient method of intro-
ducing aryland aklenylgroups at the
b-position of
electron deficient olefins with high enantioselectivity.1
The organometallic reagents first used for the catalytic
asymmetric 1,4-addition are organoboronic acids,2,3
and then they are extended to organotitanium,4 -sili-
con,5,6 and -tin7 reagents. We have previously reported
that (alkenyl)catecholboranes generated by hydrobora-
tion of alkynes with catecholborane can be used, with-
out isolation or purification, for the rhodium-catalyzed
asymmetric 1,4-addition to a,b-unsaturated ketones giv-
ing b-alkenyl ketones with over 90% enantioselectivity.8
The hydroboration and 1,4-addition can be carried out
successively in one-pot. Herein we report another one-
pot reaction system where hydrosilylation of alkynes
with triethoxy(hydro)silane followed by asymmetric
1,4-addition of the resulting alkenylsilane is catalyzed
by a single chiral phosphine–rhodium complex.
It was found that the cationic rhodium/(S)-binap system
used for the 1,4-addition catalyzes the hydrosilylation of
phenylacetylene 4m with triethoxysilane.9 The reaction
with 1.5equiv of the hydrosilane in dioxane was com-
pleted in 1h at room temperature to give a quantitative
yield of a mixture of (E)-2-phenylethenyl(triethoxy)-
silane 2m, its Z isomer and the regioisomer 1-phenyl-
ethenyl(triethoxy)silane 5m in a ratio of 74:1:25. The
use of this hydrosilylation mixture, which contains
remaining triethoxysilane and the rhodium–binap cata-
lyst, for the next 1,4-addition step by the addition of
enone 1a and water and heating the mixture at 90°C
did not give a satisfactory yield of the 1,4-addition prod-
uct 3am. It is mainly due to the reduction of enone 1a
with the hydrosilane giving cyclohexanone. This prob-
lem was solved by treatment of the hydrosilylation mix-
ture with water for 0.5h at room temperature before the
2. Results and discussion
Oi and Inoue reported5 that the asymmetric 1,4-addi-
tion of (E)-2-phenylethenyl(triethoxy)silane 2m to 2-
*
Corresponding author. Tel.: +81-75-753-3983; fax: +81-75-753-
3988; e-mail: thayashi@kuchem.kyoto-u.ac.jp
0957-4166/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.07.003

2648
Y. Otomaru, T. Hayashi / Tetrahedron: Asymmetry 15 (2004) 2647–2651
O
O
[Rh((S)-binap)(MeCN)2]BF4
(3 mol %)
(S)-binap (1 mol %)
Ph
+
Si(OEt)3
(E )-2m
O (10/1)
dioxane/H2
Ph
90oC, 20 h
1a
3am
Scheme 1.
addition of enone 1a, which probably decomposes the
remaining hydrosilane by the rhodium-catalyzed hydrol-
ysis of hydrosilane.10 Thus, the rhodium-catalyzed
hydrosilylation and 1,4-addition in one-pot was realized
according to the following procedures: to a solution of
[Rh((S)-binap)(MeCN)2]BF4 (12lmol) and (S)-binap
(4lmol) in dioxane (2mL) was added phenylacetylene
4m (1.0mmol) and triethoxysilane (1.5mmol), and the
mixture was stirred at room temperature for 1h. Water
(0.2mL) was added and the mixture was stirred at room
temperature for 0.5h. To the resulting reaction mixture
was added 2-cyclohexenone 1a (0.4mmol) and it was
heated at 90°C for 20h. Addition of hexane to remove
precipitates followed by chromatography on silica gel
gave 89% yield of the 1,4-addition product, which con-
sists of (S)-3-((E)-2-phenylethenyl)cyclohexanone 3am
(93% ee) and its Z isomer in a ratio of 99:1 (entry 1 in
Table 1). It is remarkable that the formation of 1,4-addi-
tion product resulting from 1-phenylethenyl(trieth-
oxy)silane 5m was not observed under the reaction
conditions. It is probably due to the much lower reactiv-
ity of the sterically more bulky 1-phenylethenyl group.
Unfortunately, the (Z)-alkenylsilane was as reactive as
the E isomer towards the 1,4-addition, resulting in the
formation of the 1,4-addition product with the same
E,Z ratio as the alkenylsilane.
The one-pot procedure starting from phenylacetylene 4m
was successfully applied to the asymmetric 1,4-addition
to cyclic enones, 2-cyclopentenone 1b and 2-cyclohepte-
none 1c giving the corresponding (S)-3-(E)-2-phenyl-
ethenylcycloalkanes 3bm and 3cm with high (90–93%)
enantioselectivity (entries 2 and 3). For the linear enone
1d, the enantioselectivity was lower (entry 4). The regio-
selectivity in forming linear or branch alkenylsilane by
the rhodium-catalyzed hydrosilylation is dependent on
the substituents on the alkyne 4. Arylacetylenes 4m–4q
gave the hydrosilylation products containing 12–25%
of branch alkenylsilanes 5 (entries 5–8), while the lin-
ear/branch ratio for 1-octyne 4r was about one to one
(entry 9). In any cases, however, the 1,4-addition prod-
ucts were not contaminated with those resulting from
the branch alkenylsilanes. The highest regioselectivity
in forming linear alkenylsilane (E)-2 was observed in
the hydrosilylation of triethylsilylacetylene 4s, whose
reaction with 2-cyclohexenone 1a gave 85% yield of
the corresponding 1,4-addition product with 98% enan-
tioselectivity (entry 10) (Scheme 2).
O
H
R
[Rh((S)-binap)(MeCN)2]BF4
(12µmol)
O
4m-s
1a-d
(1.0 mmol)
(0.4, mmol)
H2O
(S)-binap (4 µmol)
R
Si(OEt)3
(E )-2
+
rt, 0.5 h
dioxane
rt, 1-3 h
90oC, 20 h
HSi(OEt)3
(1.5 mmol)
R
3
Si(OEt)3
(Z )-2
R
PPh2
PPh2
R
Si(OEt)3
(S)-binap
5
O
O
O
H
OMe
H
H
Ph
H
Me
4p
4n
4m
4q
4o
1b
1a
1c
O
H
H
SiEt3
H
4r
4s
1d
Scheme 2.

Y. Otomaru, T. Hayashi / Tetrahedron: Asymmetry 15 (2004) 2647–2651
2649
Table 1. Rhodium-catalyzed asymmetric 1,4-addition of alkenylsilanes 2 generated by hydrosilylation of alkynes 4a
Entry
Acetylene 4
Time (h) of
hydrosilylation
Ratiob of
(E)-2/(Z)-2/5
Enone 1
Yield (%)c
of 3
% Ee of 3d
(config)e
Ratiof of
(E)-3/(Z)-3
1
2
3
4
5
6
7
8
9
10
4m
4m
4m
4m
4n
4o
4p
4q
4r
1
1
1
1
1
2
2
3
1
3
74:1:25
74:1:25
74:1:25
74:1:25
85:0:15
72:12:16
80:8:12
76:0:24
53:2:45
98:0:2
1a
1b
1c
1d
1a
1a
1a
1a
1a
1a
89 (3am)
74 (3bm)
79 (3cm)
76 (3dm)
66 (3an)
65 (3ao)
67 (3ap)
70 (3aq)
73 (3ar)
85 (3as)
93 (S)
90 (S)
93 (S)
78 (S)
92 (S)
92 (S)
90 (S)
92 (S)
98h (S)
98h (S)
99:1
99:1
98:2g
100:0
100:0
91:9
99:1
100:0
97:3
100:0
4s
a A typicalexperimentalprocedure is shown in the text. The ratio of 4/HSi(OEt)3/[Rh((S)-binap)(MeCN)2]BF4/(S)-binap/1=100:150:1.2:0.4:40.
b Determined by 1H NMR and/or GC of the crude hydrosilylation product.
c Isolated yield of 1,4-addition product 3 based on enone 1.
d Determined by HPLC analysis with a chiral stationary phase column (Chiralcel AS). Eluent: hexane/2-propanol=90:10 for 3am, 3cm, 3an, 3ao, 3ap
and 3aq. 98:2 for 3bm. 100:1 for 3dm.
e The absolute configuration of 3am was determined by comparison of its opticalrotation with that reported in Ref. 8. The others were assigned to
have (S)-configuration by consideration of stereochemicalpathway of the asymmetric 1,4-addition reactions cataylzed by a ( S)-binap/rhodium
complex (Ref. 2).
f Determined by 1H NMR of the 1,4-addition product 3.
g Contaminated with ca. 10% of 3-(2-phenylethylidene)cycloheptanone.
h Determined by 13C NMR of diastereomeric cyclic ketals obtained with (2R,3R)-(ꢀ)-2,3-butanediol.
3. Conclusion
4.2.1. [Rh((S)-binap)(MeCN)2]BF4.
A
mixture of
2g
[RhCl((S)-binap)]2 (381mg, 0.25mmol) and AgBF4
(97.3mg, 0.50mmol) in acetonitrile was stirred at room
temperature for 1h. Removalof the precipitates fo-l
lowed by recrystallization (acetonitrile/hexane/diethyl
ether) gave 310mg (69% yield) of [Rh((S)-binap)-
(MeCN)2]BF4. 1H NMR (CDCl3, 55°C): d 1.76 (s,
6H), 6.54 (d, J=8.7Hz, 2H), 6.67 (t, J=7.3Hz, 4H),
6.78 (t, J=7.4Hz, 2H), 6.97 (t, J=7.8Hz, 2H), 7.28
(t, J=7.5Hz, 2H), 7.39 (ddd, J=9.0, 4.7, and 4.3Hz,
2H), 7.43–7.46 (m, 6H), 7.48 (d, J=8.8Hz, 2H),
7.51 (d, J=8.2Hz, 2H), 7.58–7.68 (br m, 4H), 7.76–
7.82 (m, 4H). 31P NMR (CDCl3, 55°C): d 46.2 (d,
J=176Hz).
In summary, we reported a one-pot reaction procedure
where a rhodium/(S)-binap complex catalyzes the two
successive reactions, that is, hydrosilylation of 1-alkynes
with triethoxysilane and the asymmetric 1,4-addition of
the resulting alkenylsilanes to a,b-unsaturated ketones.
Although the regioselectivity at the hydrosilylation is
not always high, the linear alkenylsilanes are much more
reactive than the branch isomers giving the linear 1,4-
addition products with high chemoselectivity. The enan-
tioselectivity is all high (>90% ee) for cyclic enones.
4. Experimental
4.1. General
4.3. General procedure of rhodium-catalyzed hydrosilyl-
ation of alkynes and subsequent asymmetric 1,4-addition
of alkenylsilanes to a,b-unsaturated ketones
All anaerobic and moisture-sensitive manipulations were
carried out with standard Schlenk technique under pre-
dried nitrogen or glovebox techniques under prepurified
argon. NMR spectra were recorded on a JEOL JNM
LA-500 spectrometer (500MHz for 1H, 125MHz for
13C, and 202MHz for 31P). Chemicalshifts are reported
in d ppm referenced to an internalSiMe 4 standard for 1H
NMR, chloroform-d (d 77.05) for 13C NMR and external
85% H3PO4 standard for 31P NMR. Opticalrotations
were measured on a JASCO DIP-370 polarimeter.
To a solution of [Rh((S)-binap)(MeCN)2]BF4 (10.7mg,
12l mol) and (S)-BINAP (2.5mg, 4.0lmol) in dioxane
(2mL) was added a terminalalkyne 4 (1.0mmol) and tri-
ethoxysilane (246mg, 1.5mmol), and the mixture was
stirred at room temperature for 1–3h. After the addition
of H2O (0.2mL), the mixture was stirred at room tem-
perature for 30min. An a,b-unsaturated ketone 1
(0.40mmol) was added at room temperature, and the
mixture was stirred at 90°C for 20h. The reaction mix-
ture was added to hexane and the resulting precipitates
were removed by filtration. The solution was dried over
MgSO4 and concentrated under reduced pressure. The
residue was purified by preparative TLC (silica gel, benz-
ene) to give the 1,4-addition product 3. The results are
summarized in Table 1.
4.2. Materials
Dioxane was distilled from sodium benzophenone-ketyl
under nitrogen. Arylacetylenes were prepared by palla-
dium-catalyzed coupling reaction of 2-methyl-3-butyn-
2-olwith arylbromides according to the procedures
reported by Sonogashira et al.,11 followed by removal
of acetone by heating with KOH in toluene.12
4.3.1. 3-((E)-2-Phenylethenyl)cyclohexanone 3am.8 1H
NMR (CDCl3): d 1.58–1.66 (m, 1H), 1.70–1.80 (m,

2650
Y. Otomaru, T. Hayashi / Tetrahedron: Asymmetry 15 (2004) 2647–2651
1H), 1.98–2.04 (m, 1H), 2.07–2.14 (m, 1H), 2.28–2.35
(m, 2H), 2.38–2.43 (m, 1H), 2.50–2.56 (m, 1H), 2.63–
2.72 (m, 1H), 6.16 (dd, J=16.0 and 6.9Hz, 1H), 6.39
(d, J=16.0Hz, 1H), 7.22 (t, J=7.4Hz, 1H), 7.30 (t,
J=7.4Hz, 2H), 7.35 (d, J=7.4Hz, 2H). 13C NMR
(CDCl3): d 24.96, 31.36, 41.24, 41.91, 47.32, 126.09,
41.26, 42.22, 47.46, 125.39, 126.04, 126.99, 127.25,
130.22, 134.32, 135.21, 136.22, 210.91. Anal. Calcd for
C15H18O: C, 84.07; H, 8.47. Found: C, 84.20; H,
20
8.53. ½aŠ ¼ ꢀ13:0 (c 0.88, CHCl3) for S isomer of
D
92% ee.
127.32, 128.53, 129.06, 132.88, 137.06, 210.85.
4.3.7. 3-{(E)-2-(1-Naphthyl)ethenyl}cyclohexanone 3ap.
1H NMR (CDCl3): d 1.64–1.72 (m, 1H), 1.74–1.83 (m,
1H), 2.05–2.15 (m, 2H), 2.30–2.45 (m, 3H), 2.59–2.63
(m, 1H), 2.75–2.83 (m, 1H), 6.15 (dd, J=15.7 and
6.8Hz, 1H), 7.13 (d, J=15.7Hz, 1H), 7.42 (t,
J=7.9Hz, 1H), 7.45–7.54 (m, 3H), 7.76 (d, J=8.1Hz,
1H), 7.84 (d, J=7.9Hz, 1H), 8.06 (d, J=8.3Hz, 1H).
13C NMR (CDCl3): d 24.93, 31.37, 41.26, 42.20, 47.33,
123.61, 123.68, 125.54, 125.72, 125.96, 126.40, 127.69,
128.47, 131.07, 133.53, 134.89, 136.21, 210.84. Anal.
20
D
½aŠ ¼ þ5:2 (c 1.02, CHCl3) for S isomer of 93% ee.
4.3.2. 3-((E)-2-Phenylethenyl)cyclopentanone 3bm.13
1H NMR (CDCl3): d 1.79–1.86 (m, 1H), 2.13 (ddd,
J=18.2, 10.4 and 1.2Hz, 1H), 2.19–2.30 (m, 2H),
2.35–2.42 (m, 1H), 2.49 (dd, J=18.2 and 7.5Hz, 1H),
2.98–3.06 (m, 1H), 6.22 (dd, J=15.9 and 7.3Hz, 1H),
6.46 (d, J=15.9Hz, 1H), 7.23 (t, J = 7.4Hz, 1H), 7.31
(t, J=7.4Hz, 2H), 7.36 (d, J=7.4Hz, 2H). 13C NMR
(CDCl3): d 29.89, 38.21, 40.24, 44.80, 126.08, 127.38,
Calcd for C18H18O: C, 86.36; H, 7.25. Found: C,
20
D
20
D
128.57, 129.76, 132.00, 136.93, 218.57. ½aŠ ¼ ꢀ77:7 (c
86.30; H, 7.25. ½aŠ ¼ ꢀ12:4 (c 0.54, CHCl3) for S iso-
0.78, CHCl3) for S isomer of 90% ee.
mer of 90% ee.
1
4.3.8. 3-{(E)-2-(2-Naphthyl)ethenyl}cyclohexanone 3aq. H
4.3.3. 3-((E)-2-Phenylethenyl)cycloheptanone 3cm. 1H
NMR (CDCl3): d 1.45–1.58 (m, 2H), 1.62–1.71 (m,
1H), 1.88–2.05 (m, 3H), 2.50–2.70 (m, 5H), 6.15 (dd,
J=15.9 and 7.5Hz, 1H), 6.39 (d, J=15.9Hz, 1H), 7.21
(t, J=7.3Hz, 1H), 7.30 (t, J=7.3Hz, 2H), 7.33 (d,
J=7.3Hz, 2H). 13C NMR (CDCl3): d 24.00, 28.37,
37.11, 39.45, 44.04, 49.43, 126.05, 127.18, 128.42,
128.50, 134.25, 137.21, 213.51. Anal. Calcd for
NMR (CDCl3): d 1.60–1.68 (m, 1H), 1.70–1.80 (m,
1H), 2.00–2.06 (m, 1H), 2.08–2.14 (m, 1H), 2.28–2.44
(m, 3H), 2.53–2.59 (m, 1H), 2.68–2.75 (m, 1H), 6.27 (dd,
J=15.9 and 6.9Hz, 1H), 6.54 (d, J=15.9Hz, 1H), 7.40–
7.47 (m, 2H), 7.56 (dd, J=8.6 and 1.6Hz, 1H), 7.69 (s,
1H), 7.75–7.80 (m, 3H). 13C NMR (CDCl3): d 24.95,
31.37, 41.25, 41.99, 47.32, 123.35, 125.70, 125.89, 126.21,
127.59, 127.83, 128.13, 129.17, 132.80, 133.27, 133.56,
C15H18O: C, 84.07; H, 8.47. Found: C, 84.12; H, 8.44.
20
D
½aŠ ¼ ꢀ11:3 (c 0.84, CHCl3) for S isomer of 93% ee.
134.49, 210.83. Anal. Calcd for C18H18O: C, 86.36;
20
D
H, 7.25. Found: C, 86.09; H, 7.26. ½aŠ ¼ þ6:1 (c
4.3.4.
5-Methyl-4-((E-2-phenylethenyl)hexan-2-one
1.05, CHCl3) for S isomer of 92% ee.
3dm. 1H NMR (CDCl3): d 0.90 (d, J=6.9Hz, 3H),
0.93 (d, J=6.9Hz, 3H), 1.69–1.75 (m, 1H), 2.12 (s,
3H), 2.50–2.62 (m, 3H), 6.03 (dd, J=15.9 and 8.9Hz,
1H), 6.37 (d, J=15.9Hz, 1H), 7.20 (t, J=7,3Hz, 1H),
7.29 (t, J=7.3Hz, 2H), 7.33 (d, J=7.3Hz, 2H). 13C
NMR (CDCl3): d 18.98, 20.53, 30.64, 32.00, 45.12,
46.76, 126.09, 127.09, 128.44, 130.83, 131.28, 137.33,
4.3.9. 3-((E)-2-Octenyl)cyclohexanone 3ar. 1H NMR
(CDCl3): d 0.88 (t, J=7.0Hz, 3H), 1.23–1.36 (m, 8H),
1.44–1.52 (m, 1H), 1.63–1.73 (m, 1H), 1.87–1.92 (m,
1H), 1.95–2.07 (m, 3H), 2.15–2.30 (m, 2H), 2.32–2.49
(m, 3H), 5.36 (dd, J=15.5 and 6.2Hz, 1H), 5.43 (dt, J
= 15.5 and 6.4Hz, 1H). 13C NMR (CDCl3): d 14.05,
22.58, 24.94, 28.72, 29.32, 31.57, 31.65, 32.44, 41.25,
41.56, 47.70, 129.97, 132.89, 211.45. Anal. Calcd for
208.39. Anal. Calcd for C15H20O: C, 83.28; H, 9.32.
20
D
Found: C, 83.44; H, 9.53. ½aŠ ¼ ꢀ35:2 (c 1.00, CHCl3)
for S isomer of 78% ee.
C14 H24O: C, 80.71; H, 11.61. Found: C, 80.45; H,
20
D
of 98% ee. The enantiomeric purity of this ketone was
11.48. ½aŠ ¼ ꢀ17:7 (c 1.00, CHCl3) for S isomer
4.3.5. 3-{(E)-2-(4-Methoxyphenyl)ethenyl}cyclohexanone
3an. 1H NMR (CDCl3): d 1.55–1.64 (m, 1H), 1.68–
1.77 (m, 1H), 1.96–2.02 (m, 1H), 2.05–2.12 (m, 1H),
2.27–2.33 (m, 2H), 2.36–2.41 (m, 1H), 2.49–2.53 (m,
1H), 2.60–2.68 (m, 1H), 3.79 (s, 3H), 6.01 (dd, J=15.9
and 6.9Hz, 1H), 6.33 (d, J=15.9Hz, 1H), 6.84 (d,
J=8.8Hz, 2H), 7.28 (d, J=8.8Hz, 2H). 13C NMR
(CDCl3): d 24.92, 31.45, 41.21, 41.87, 47.43, 55.21,
113.90, 121.17, 128.36, 129.80, 130.73, 158.95, 210.92.
determined by 13C{1H} NMR spectra of a mixture of
diastereomeric ketals obtained with (2R,3R)-(ꢀ)-2,3-but-
2
anediol.14 The resonances of octenylsp
carbons (d
128.31 vs 128.36, 134.86 vs 134.95) were used for the
determination of % ee.
4.3.10. 3-((E)-2-Triethylsilylethenyl)cyclohexanone 3as.
1H NMR (CDCl3): d 0.55 (q, J=8.0Hz, 6H), 0.92 (t,
J=8.0Hz, 9H), 1.48–1.56 (m, 1H), 1.65–1.75 (m, 1H),
1.92–1.97 (m, 1H), 2.02–2.08 (m, 1H), 2.21–2.31 (m,
2H), 2.34–2.39 (m, 1H), 2.42–2.47 (m, 1H), 2.49–2.56
(m, 1H), 5.57 (dd, J = 18.9 and 1.5Hz, 1H), 5.98 (dd,
J=18.9 and 5.8Hz, 1H). 13C NMR (CDCl3): d 3.36,
7.30, 24.92, 30.91, 41.29, 44.67, 46.81, 124.87, 150.06,
Anal. Calcd for C15H18O2: C, 78.23; H, 7.88. Found:
20
D
C, 78.13; H, 7.91. ½aŠ ¼ ꢀ4:4 (c 0.87, CHCl3) for S iso-
mer of 92% ee.
4.3.6. 3-{(E)-2-(2-Methylphenyl)ethenyl}cyclohexanone
3ao. 1H NMR (CDCl3): d 1.59–1.67 (m, 1H), 1.71–
1.81 (m, 1H), 2.00–2.05 (m, 1H), 2.08–2.14 (m, 1H),
2.32 (s, 3H), 2.29–2.45 (m, 3H), 2.52–2.56 (m, 1H),
2.67–2.75 (m, 1H), 6.02 (dd, J=15.8 and 7.0Hz, 1H),
6.60 (d, J=15.8Hz, 1H), 7.12–7.18 (m, 3H), 7.39–7.41
(m, 1H). 13C NMR (CDCl3): d 19.75, 24.96, 31.47,
211.35. Anal. Calcd for C14 H26OSi: C, 70.52; H,
20
D
10.99. Found: C, 70.60; H, 11.14. ½aŠ ¼ ꢀ8:1 (c 0.35,
CHCl3) for S isomer of 98% ee. In a similar manner
to 3ar, the ketone 3as was converted into the diastereo-
meric ketals of (2R,3R)-(ꢀ)-2,3-butanediol. The

Y. Otomaru, T. Hayashi / Tetrahedron: Asymmetry 15 (2004) 2647–2651
2651
2
44, 6505; (j) Boiteau, J.-G.; Imbos, R.; Minnaard, A. J.;
Feringa, B. L. Org. Lett. 2003, 5, 681 and Org. Lett. 2003,
5, 1385 for corrections; (k) Boiteau, J.-G.; Minnaard, A.
J.; Feringa, B. L. J. Org. Chem. 2003, 68, 9481; (l) Ma, Y.;
Song, C.; Ma, C.; Sun, Z.; Chai, Q.; Andrus, M. B. Angew.
Chem., Int. Ed. 2003, 42, 5871.
resonances of ethenylsp carbons (d 112.02 vs 112.06,
143.30 vs 143.39) were used for the determination of
% ee.
Acknowledgements
4. (a) Hayashi, T.; Tokunaga, N.; Yoshida, K.; Han, J. W. J.
Am. Chem. Soc. 2002, 124, 12102; (b) Yoshida, K.;
Hayashi, T. J. Am. Chem. Soc. 2003, 125, 2872.
5. Oi, S.; Taira, A.; Honma, Y.; Inoue, Y. Org. Lett. 2003, 5,
97.
This work was supported in part by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Sci-
ence, Sports and Culture, Japan.
6. For the nonasymmetric version of rhodium-catalyzed 1,4-
addition: (a) Mori, A.; Danda, Y.; Fujii, T.; Hirabayashi,
K.; Osakada, K. J. Am. Chem. Soc. 2001, 123, 10774; (b)
Huang, T.-S.; Li, C.-J. Chem. Commun. 2001, 2348; (c)
Koike, T.; Du, X.; Mori, A.; Osakada, K. Synlett 2002,
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667; (e) Murata, M.; Shimazaki, R.; Ishikura, M.;
Watanabe, S.; Masuda, Y. Synthesis 2002, 717.
7. Hayashi, T.; Ueyama, K.; Tokunaga, N.; Yoshida, K.
J. Am. Chem. Soc. 2003, 125, 11508.
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