Highly regio- and stereoselective hydrosilylation of β-fluoroalkylated α,β-unsaturated ketones

Article abstract of DOI:10.1016/j.jfluchem.2015.02.010

Treatment of β-fluoroalkylated α,β-unsaturated ketones with 10.2 equiv of triethylsilane in the presence of 3 mol% of Co₂(CO)₈ in dichloroethane at the reflux temperature for 4 h gave 1,4-hydrosilylated adducts in a highly regio- and

Full text of DOI:10.1016/j.jfluchem.2015.02.010

Journal of Fluorine Chemistry 173 (2015) 69–76
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Highly regio- and stereoselective hydrosilylation of
-unsaturated ketones
b-fluoroalkylated
a,b
*
Natsumi Ikeda, Tsutomu Konno
Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
A R T I C L E I N F O
A B S T R A C T
Treatment of
Article history:
b
-fluoroalkylated a,b-unsaturated ketones with 10.2 equiv of triethylsilane in the
Received 19 January 2015
Received in revised form 6 February 2015
Accepted 7 February 2015
Available online 28 February 2015
presence of 3 mol% of Co2(CO)8 in dichloroethane at the reflux temperature for 4 h gave 1,4-
hydrosilylated adducts in a highly regio- and stereoselective manner. Thus-obtained silyl enol ethers
underwent a smooth Mukaiyama aldol reaction with benzaldehyde in the presence of 1.2 equiv of TiCl4
in CH2Cl2 at À78 8C for 1 h, affording the corresponding
high syn stereoselectivity in good yields.
a
-(2,2,2-trifluoroethyl)-
b-hydroxy ketones with
Keywords:
ß 2015 Elsevier B.V. All rights reserved.
Hydrosilylation
b-Fluoroalkylated a,b-unsaturated ketones
Dicobalt octacarbonyl
Regioselective
Stereoselective
Aldol reaction
1. Introduction
b-fluoroalkylated a,b-unsaturated ketones 1 in the presence of
relatively inexpensive cobalt catalyst in detail (Scheme 2).
Moreover, we wish to disclose the highly syn-selective aldol
reactions using thus-obtained hydrosilylated adducts 2.
Transition metal-catalyzed hydrosilylation of
a,b-unsaturated
carbonyl compounds has been recognized as one of the most
important and valuable synthetic methods for the preparation of
silyl enol ethers [1]. This is because the reaction generally proceeds
in a 1,4-addition manner to produce the corresponding silyl enol
ethers, which can participate well in the subsequent various
reactions, such as Mukaiyama aldol reaction [2], Michael addition
[3], alkylation [4], halogenation [5], oxidation [6], and so on [7]
(Scheme 1). Therefore, it is not surprising that there have been
voluminous researches on hydrosilylation reactions of nonfluori-
2. Results and discussion
2.1. Preparation of
b-fluoroalkylated a,b-unsaturated ketones
Initially, we began with the preparation of various
b-
fluoroalkylated -unsaturated ketones 1A–H. As shown in
a,b
Scheme 3, 1A–C were easily prepared from commercially available
fluorinated hemiacetals 3, 4 or hydrate 5 and the enamine
6 according to the literature (Scheme 3, eq. 1) [11]. On the other
hand, 1D–H were prepared with slight modifications of the
reported procedure (Scheme 3, eq. 2) [12]. Thus, treatment of
2-bromo-3,3,3-trifluoropropene 7 (1.0 equiv) with LDA (2.2 equiv)
in THF at À78 8C for 5 min, followed by the addition of various
aldehydes (1.0 equiv) into the resultant reaction mixture, gave the
nated a,b-unsaturated carbonyl compounds. However, most of the
researches are concerned with the hydrosilylation catalyzed by
very expensive rhodium, palladium, platinum, or gold catalysts,
and little attention has been paid to inexpensive transition metal-
catalyzed hydrosilylation thus far [8]. In addition, to the best of our
knowledge, hydrosilylations of fluorinated
a,b-unsaturated car-
bonyl compounds have hardly been reported [9].
As a part of our research project on hydrometallation reactions of
various fluorinated substances [10], herein is described the highly
regio- and stereoselective hydrosilylation reaction of various
corresponding
g-fluoroalkylated propargyl alcohols 8 [12,13].
Without purification, thus-obtained propargyl alcohols 8 were
subjected to an excess amount of NaBH4 in ethanol at room
temperature for 14 h, affording the corresponding
g-fluoroalky-
lated allylic alcohols 9 in good yields. Finally, the allylic alcohols
were easily oxidized by MnO2 at the reflux temperature to provide
*
Corresponding author. Tel.: +81 75 724 7517.
E-mail address: konno@kit.ac.jp (T. Konno).
the desired b-fluoroalkylated a,b-unsaturated ketones 1.
http://dx.doi.org/10.1016/j.jfluchem.2015.02.010
0022-1139/ß 2015 Elsevier B.V. All rights reserved.

70
N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
Scheme 1. Hydrosilylation of
a,b-unsaturated carbonyl compounds and the synthetic applications.
desired product in only 61% yield (Entry 3), prolonged reaction
under 3 mol% loading of the catalyst afforded the desired product
quantitatively (Entry 4). At lower temperature, the reaction hardly
proceeded (Entry 5). Very interestingly, rhodium or platinum
catalysts, very frequently employed for hydrosilylation of the
nonfluorinated substances, were found not to be suitable for this
reaction (Entries 6–9).
Scheme 2. Present work.
2.2. Hydrosilylation of
b
-fluoroalkylated
a
,
b
-unsaturated ketones
We next examined a series of silanes as summarized in
Table 2. In the case of PhMe2SiH, the desired 2Ab was obtained
in only 54% yield though the starting material was completely
consumed (Entry 2). Additionally, the stereoselectivity of 2Ab still
remainedveryhigh, but theregioselectivity significantly decreased.
It was also revealed that use of (EtO)2MeSiH and (EtO)3SiH caused a
significant decrease of the regioselectivity (Entries 3 and 4) [15].
With the best reaction conditions in hand, we next tested a
With various types of substrates in hand, our attention was
directed toward the examination of the hydrosilylation reaction of
1A–H. First of all, we started the exploitation of the optimum
reaction conditions by using 1A, as shown in Table 1. Thus,
treatment of 1A with 1.2 equiv of Et3SiH in the presence of 5 mol%
of Co2(CO)8 in dichloroethane at the reflux temperature for 12 h
resulted in a complete consumption of the starting ketone,
affording the 1,4-hydrosilylated adduct 2Aa with high Z selectivity
in 78% yield, together with 7% of the 1,2-hydrosilyated adduct
10Aa [14]. It was also revealed that the reaction completed within
2 h without any decrease of the yield and the stereoselectivity
(Entry 2). Although a lower loading of the catalyst afforded the
variety of
b-fluoroalkylated a,b-unsaturated ketones for the
hydrosilylation reaction. The results are summarized in Table 3.
As shown in Entries 2–4, the position of a substituent on the
benzene ring in the substrate did not influence on the reaction at
all, providing the corresponding silyl enol ethers 2Da, 2Ea, 2Fa in a
highly regio- and stereoselective manner. Additionally, the ketones
Scheme 3. Preparation of various
b-fluoroalkylated a,b-unsaturated ketones.

N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
71
Table 1
Investigation of the reaction conditions.
.
Entry
Catalyst
X/mol%
Temp.
Time/h
Yielda/% of 2Aa + 10Aa
Ratio 2Aa/10Aa
Ratio of 2Aaa E/Z
Recoverya/% of 1A
1
2
3
4
5
6
7
8
9
Co2(CO)8
5
5
3
3
3
3
3
3
3
Reflux
Reflux
Reflux
Reflux
50 8C
Reflux
Reflux
Reflux
Reflux
12
2
85 (78 +7)
91 (87 +4)
61 (57 +4)
99 (94 +5)
17 (15 +2)
11 (11 +0)
15 (15 +9)
58 (58 +0)
13 (13 +0)
92/8
5/95
0
0
Co2(CO)8
96/4
2/98
Co2(CO)8
2
93/7
0/100
1/99
39
0
Co2(CO)8
4
95/5
Co2(CO)8
4
88/12
100/0
100/0
100/0
100/0
0/100
26/74
40/60
36/64
0/100
81
80
25
0
[Rh(cod)Cl]2/2PPh3
RhCl(PPh3)3
[Rh(cod)2]BF4/2PPh3
H2PtCl6Á6H2O
4
4
4
4
0
a
Determined by 19F NMR. The former and the latter values in parentheses are 19F NMR yields of 2Aa and 10Aa, respectively.
Table 2
Hydrosilylation using various silanes.
.
Entry
Silane Si-H
Yielda/% of 2A + 10A
Ratioa 2A/10A
Ratio of 2Aa E/Z
Recoverya/% of 1A
1
2
3
4
Et3SiH (a)
99 (94 + 5)
73 (54 + 19)
93 (62 + 31)
46 (26 + 20)
95/5
1/99
7/93
3/97
0/100
0
PhMe2SiH (b)
(EtO)2MeSiH (c)
(EtO)3SiH (d)
74/26
69/31
57/43
0
0
33
a
Determined by 19F NMR. The former and the latter values in parentheses are 19F NMR yields of 2A and 10A, respectively.
Scheme 4. Determination of the stereochemistry.
having an heteroaromatic ring or a naphthyl group were found to
be good substrates as well (Entries 5 and 6) [16]. Changing a
fluoroalkyl group from a CF3 to a C3F7 group did not bring about any
dramatic change in the reaction (Entry 7). Although use of a CHF2
group as Rf retarded the reaction proceeding (Entry 8), increasing
the amount of the catalyst from 3 to 5 mol% led to a satisfactory
result (Entry 9).
On the other hand, 2Ba was also found to be a Z isomer because
the 19F NMR signal of the Z isomer appears at lower field than the
one of the E isomer. In a manner similar to 2Ba, the stereochemis-
try of 2Ca was determined as Z based on the 19F NMR signals for the
CF2 group adjacent to the CH2 group (À128.33 for E isomer,
À128.14 for Z isomer) (Fig. 1).
2.4. Synthetic application of fluorinated silyl enol ethers
2.3. Determination of the stereochemistry
As synthetic application, we attempted the Mukaiyama aldol
reaction using the above-obtained silyl enol ethers. Thus,
treatment of 2Aa (1.0 equiv) with 1.2 equiv of benzaldehyde in
the presence of 1.2 equiv of TiCl4 in CH2Cl2 at À78 8C for 1 h gave
The stereochemical assignment of 2 was made as follows
(Scheme 4). In general, it has been well known that treatment of
alkyl phenyl ketones with a slight excess of LDA gives the
corresponding Z-silyl enol ethers preferentially [17]. Then, 4,4,4-
trifluoro-1-phenyl-1-butanone 11 was subjected to the enolization
using LDA/Et3SiCl. Thus, on treating 11 with 1.1 equiv of LDA in
THF at À78 8C for 0.5 h, followed by the addition of 1.1 equiv of
Et3SiCl and the stirring of the reaction mixture at room
temperature, the corresponding Z-silyl enol ether was obtained
as a single isomer. On the other hand, the silyl enol ether 2Aa,
prepared through the hydrosilylation of 1A with Et3SiH in the
presence of Co2(CO)8, was found to be completely identical to
the product derived from 11, indicating unambiguously that the
hydrosilylated adduct 2Aa was a Z isomer.
the corresponding a-hydroxy-b-(2,2,2-trifluoroethyl)ketone 12Aa
with high syn selectivity in 67% isolated yield (Scheme 5) [18]. In
terms of efficiency, we also carried out the one-pot procedure for
The stereochemistry of other hydrosilylated products 2Da–2Ha
was determined as Z based on the analogy of the chemical shifts
between 2Aa and 2Da–2Ha.
Scheme 5. Mukaiyama aldol reaction of 2Aa with benzaldehyde.

72
N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
Table 3
Hydrosilylation of various
b-fluoroalkylated
a,
b-unsaturated ketones.
.
Entry
1
Product
Yielda/% of 2 + 10
Ratiob 2/10
Ratio of 2b E/Z
2Aa
94 (90)
95/5
0/100
2
3
2 Da
98 (95)
92/8
94/6
3/97
5/95
2Ea
2Fa
93 (87)
92 (90)
4
93/7
6/94
5
6
2Ga
2Ha
88 (82)
93 (87)
96/4
96/4
10/90
2/98
7
2Ca
91 (87)
100/0
9/91
8
9c
2Ba
2Ba
41
95/5
96/4
5/95
2/98
96 (92)
a
Determined by 19F NMR. Values in parentheses are of isolated yield.
Determined by 19F NMR.
b
c
Five mol% of Co2(CO)8 was used.
Scheme 6. One-pot procedures for the hydrosilylation of 1A, 1E and the subsequent aldol reaction.

N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
73
Fig. 1. Comparison of chemical shifts in 19F NMR.
the hydrosilylation and the following aldol reaction (Scheme 6,
eq. 1). In consequence, the desired aldol adduct 12Aa was obtained
without loss of diastereoselectivity in approximately the same
yield as shown in Scheme 5. In addition, changing the substrate
from 1A to 1E did not influence on the yield as well as the
diastereoselectivity (Scheme 6, eq. 2).
To this reaction mixture was dropwise added 2-bromo-3,3,3-
trifluoropropene (3.49 g, 20 mmol) at À78 8C. After stirring of the
reaction mixture for 5 min, 4-methoxybenzaldehyde (1.26 mL,
20 mmol) was added into the mixture, and then the whole was
stirred at that temperature for 2 h. The mixture was quenched with
saturated NH4Cl aq., and then the whole was extracted with AcOEt
threetimes. The combinedorganiclayers weredriedoveranhydrous
Na2SO4, then filtered and concentrated in vacuo. The residue was
dissolved in ethanol, and to this reaction mixture was added NaBH4
(0.380 g, 10 mmol) at 0 8C. The solution was warmed to room
temperature, and stirred for 14 h. The reaction was quenched with
saturated NH4Cl aq. and the whole was extracted with AcOEt three
times. The combined organic layers were dried over anhydrous
Na2SO4, then filtered and concentrated in vacuo. The resulting
yellow liquid was purified by silica gel column chromatography
(Hexane/EtOAc = 5/1) to give the corresponding (E)-4,4,4-trifluoro-
1-(4-methoxyphenyl)-2-buten-1-ol (9D).
3. Conclusion
In summary, we have developed the novel Co2(CO)8-catalyzed
hydrosilylation reaction of various
b-fluoroalkylated a,b-unsatu-
rated ketones. It was revealed that this reaction proceeded in a
highly Z-selective manner to give the corresponding silyl enol
ethers in good to high yields. We have also demonstrated the
following highly syn-selective aldol reaction using thus-obtained
hydrosilylated adducts with benzaldehyde. It should be noted that
one-pot method for the hydrosilylation of the
b-fluoroalkylated
a,b
-unsaturated ketones and the following aldol reaction also
afforded the coupling products in good yields without loss of
diastereoselectivity.
4.2.1. (E)-4,4,4-Trifluoro-1-(4-methoxyphenyl)-2-buten-1-ol (9D)
Yield 70%; Yellow liquid; IR (neat) 3408, 1683, 1611, 1514,
1465, 1305, 1254, 1176, 1121, 1081, 1034, 977, 834 cmÀ1: HRMS
(FAB) Calcd for (M+) C11H11F3O2: 232.0711, Found 232.0710; 1H
4. Experimental
NMR (CDCl3)
J = 16.58, 2.00, 6.79 Hz, 1H), 6.51 (ddq, J = 16.58, 3.60, 1.79 Hz, 1H),
6.89–6.93 (m, 2H), 7.23–7.28 (m, 2H); 13C NMR (CDCl3)
= 55.2,
d = 2.07 (m, 1H), 3.83 (s, 3H), 5.28 (m, 1H), 6.03 (ddq,
4.1. General
d
Infrared spectra (IR) were recorded on a Shimadzu FTIR-8200A
(PC) spectrophotometer and Thermo Electron Corp AVATAR
370DTGS spectrophotometer. 1H NMR (500.13 MHz) and 13C
72.2, 114.4, 117.5 (q, J = 34.7 Hz), 123.3 (q, J = 268.7 Hz), 128.0,
132.7, 141.2 (q, J = 6.1 Hz), 158.7; 19F NMR (CDCl3, CFCl3)
d
= À64.41 (d, J = 6.79 Hz, 3F).
NMR (125.75 MHz) spectra were measured with
a Bruker
DRX500 spectrometer or a JEOL JNM-AL400 spectrometer in a
chloroform-d (CDCl3) solution with tetramethylsilane (TMS) as an
internal reference. 19F NMR spectra were measured with a Bruker
4.2.2. (E)-4,4,4-Trifluoro-1-(3-methoxyphenyl)-2-buten-1-ol (9E)
Yield 69%; Yellow liquid; IR (neat) 3410, 2954, 1682, 1603,
1489, 1457, 1438, 1266, 1046, 977, 862, 786, 699 cmÀ1: HRMS
(FAB) Calcd for (M+) C11H11F3O2: 232.0711, Found 232.0705; 1H
DPX300 (282.38 MHz) spectrometer or
a JEOL JNM-AL400
spectrometer (376.05 MHz) in a CDCl3 solution containing CFCl3
as an internal reference. A JEOL JNM-EX90A (84.21 MHz, FT)
spectrometer was used for determining the yields of the products
with internal hexafluorobenzene (C6F6), trifluoromethylbenzene
(BTF), or ethyl trifluoroacetate (TFA). It was also used for the
determining regioselectivity and stereoselectivity. High-resolution
mass spectra (HRMS) were measured with a JEOL JMS-700 mass
spectrometer by electron impact (EI), chemical ionization (CI), or
fast atom bombardment (FAB) method.
NMR (CDCl3)
(m, 1H), 6.49–6.54 (m, 1H), 6.87–6.93 (m, 3H), 7.29–7.33 (m, 1H);
13C NMR (CDCl3)
= 55.16–55.18 (m), 72.50–72.51 (m), 112.1,
113.4, 117.6 (q, J = 33.9 Hz), 118.7, 123.2 (q, J = 269.5 Hz), 130.0,
141.0 (q, J = 5.8 Hz), 142.2, 159.9; 19F NMR (CDCl3, CFCl3)
d = 2.31 (m, 1H), 3.82 (s, 3H), 5.31 (m, 1H), 6.02–6.07
d
d
= À64.49 (d, J = 4.89 Hz, 3F).
4.2.3. (E)-4,4,4-Trifluoro-1-(2-methoxyphenyl)-2-buten-1-ol (9F)
Yield 69%; Yellow liquid; IR (neat) 3411, 2955, 1681, 1603,
1489, 1457, 1266, 1117, 1046, 977, 862, 699 cmÀ1: HRMS (FAB)
Calcd for (M+) C11H11F3O2: 232.0711, Found 232.0720; 1H NMR
4.1.1. Materials
All chemicals were reagent-grade, and if necessary, were
purified in the usual manner prior to use. Thin layer chromatogra-
phy (TLC) was done with Merck 25 aluminium sheets (silica gel
60 F254). Column chromatography was carried out with Wakogel
C-200. All reactions were carried out under argon atmosphere.
(CDCl3)
J = 16.58, 2.00, 6.79 Hz, 1H), 6.60 (ddq, J = 16.58, 5.60, 2.40 Hz, 1H),
6.92–7.01 (m, 2H), 7.26–7.34 (m, 2H); 13C NMR (CDCl3)
= 55.2,
68.63–68.66 (m), 110.8, 117.2 (q, J = 33.9 Hz), 121.0, 123.4 (q,
J = 268.9 Hz), 127.2, 128.6, 129.4, 140.9–141.0 (m), 156.4; 19F NMR
d = 2.89 (m, 1H), 3.87 (s, 3H), 5.55 (m, 1H), 5.99 (ddq,
d
(CDCl3, CFCl3)
d
= À64.21 (d, J = 6.79 Hz, 3F).
4.2. Preparation of
g-fluoroalkylated allylic alcohol derivatives
4.2.4. (E)-4,4,4-Trifluoro-1-(2-furyl)-2-buten-1-ol (9G)
Typical procedure: Diisopropylamine (6.78 mL, 44 mmol) was
dissolved in THF (40 mL), and the whole was cooled to À78 8C. Then
to this mixture was added n-BuLi (1.6 M in n-hexane, 27.5 mL,
44 mmol) at that temperature, and the whole was stirred for 30 min.
Yield 62%; Yellow liquid; IR (neat) 3408, 1683, 1611, 1514,
1466, 1305, 1254, 1176, 1121, 1080, 1034, 977, 834 cmÀ1: HRMS
(FAB) Calcd for (M+Na) C8H7F3O2Na: 215.0288, Found 215.0296;
1H NMR (CDCl3)
d = 2.25 (d, J = 5.20 Hz, 1H), 5.39–5.39 (m, 1H),

74
N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
6.10 (ddq, J = 15.59, 2.00, 6.79 Hz, 1H), 6.59 (ddq, J = 15.59, 4.00,
10 Da: 19F NMR (CDCl3, CFCl3)
d
= À64.24 (d, J = 4.89 Hz, 3F)
2.00 Hz, 1H), 6.36–6.38 (m, 1H), 6.57–6.62 (m, 1H), 7.425–7.430
(m, 1H); 13C NMR (CDCl3)
d
= 65.92–65.95 (m), 107.8, 110.5, 119.4
4.4.3. 4,4,4-Trifluoro-1-(3-methoxyphenyl)-1-triethylsilyloxy-1-
butene (2Ea) and (E)-1,1,1-Trifluoro-4-(3-methoxyphenyl)-4-
triethylsilyloxy-2-butene (10Ea)
The products were obtained as an inseparable mixture;
Combined yield: 87%; Isomeric ratio: 2Ea:10Ea = 94:6; E:Z of
2Ea = 5:95.
(q, J = 34.2 Hz), 123.0 (q, J = 269.2 Hz), 138.0 (q, J = 6.3 Hz), 143.03–
143.07 (m), 152.76–152.79 (m); 19F NMR (CDCl3, CFCl3)
(d, J = 6.79 Hz, 3F).
d
= À64.71
4.3. Preparation of
b-fluoroalkylated a,b-unsaturated ketones
Colorless liquid; IR (neat) 2958, 2879, 1655, 1581, 1488, 1433,
1362, 1330, 1266, 1249, 1213, 1138, 1093, 1052, 1006, 846,
745 cmÀ1: HRMS (FAB) Calcd for (M+) C17H25F3O2Si: 346.1576,
Found 346.1574.
Typical procedure: A stirred solution of (E)-4,4,4-Trifluoro-1-(4-
methoxyphenyl)-2-buten-1-ol (1.16 g, 5.0 mmol, 1.0 equiv) with
MnO2 (0.87 g, 10 mmol, 2.0 equiv) in ClCH2CH2Cl (25 mL) was
heated at the reflux temperature for 16 h. The reaction was cooled
to room temperature, and the reaction mixture was passed
through the silica gel, then concentrated in vacuo. The resulting
yellow solid was purified by silica gel column chromatography
(Hexane/EtOAc = 10/1) to give the corresponding (E)-4,4,4-Tri-
fluoro-1-(4-methoxyphenyl)-2-buten-1-one (1D).
2Ea (Z isomer): 1H NMR (CDCl3)
d = 0.60 (q, J = 7.99 Hz, 6H), 0.93
(t, J = 7.99 Hz, 9H), 3.03 (dq, J = 7.09, 10.99 Hz, 2H), 3.82 (s, 3H),
5.06 (t, J = 7.09 Hz, 1H), 6.84–6.87 (m, 1H), 6.98–6.99 (m, 1H),
7.04–7.06 (m, 1H), 7.22–7.25 (m, 1H); 13C NMR (CDCl3)
d = 5.2, 6.5,
31.2 (q, J = 30.1 Hz), 55.05–55.11 (m), 98.1–98.2 (m), 111.4, 114.2,
118.6, 126.5 (q, J = 276.4 Hz), 129.2, 140.2, 154.3, 159.4; 19F NMR
(CDCl3, CFCl3)
(E isomer): 19F NMR (CDCl3, CFCl3)
3F).
10Ea: 19F NMR (CDCl3, CFCl3)
d
= À66.52 (t, J = 10.99 Hz, 3F).
4.4. Hydrosilylation of
b
-fluoroalkylated
a
,
b
-unsaturated ketones
d
= À67.09 (t, J = 12.03 Hz,
Typical procedure: A stirred solution of (Z)-1,1,1-trifluoro-4-
phenyl-2-buten-1-one (1A, 0.10 g, 0.5 mmol, 1.0 equiv) with
triethylsilane (0.1 mL, 0.6 mmol, 1.2 equiv) and Co2(CO)8 (5 mg,
3 mol%) in ClCH2CH2Cl (5 mL) was heated at the reflux temperature
for 4 h. The reaction was cooled to room temperature, and the
reaction mixture was passed through the silica gel, then concen-
trated in vacuo. The resulting yellow liquid was purified by silica gel
column chromatography (Hexane/EtOAc = 20/1) to give the corre-
d
= À64.24 (d, J = 7.14 Hz, 3F).
4.4.4. 4,4,4-Trifluoro-1-(2-methoxyphenyl)-1-triethylsilyloxy-1-
butene (2Fa) and (E)-1,1,1-Trifluoro-4-(2-methoxyphenyl)-4-
triethylsilyloxy-2-butene (10Fa)
The products were obtained as an inseparable mixture;
Combined yield: 90%; Isomeric ratio; 2Fa:10Fa = 93:7; E:Z of
2Fa = 6:94.
sponding
(2Aa).
4,4,4-trifluoro-1-phenyl-1-triethylsilyloxy-1-butene
Colorless liquid; IR (neat) 2958, 2915, 2879, 1661, 1600, 1491,
1464, 1436, 1415, 1361, 1329, 1254, 1135, 1091, 1052, 1029, 1007,
833, 788, 752 cmÀ1: HRMS (FAB) Calcd for (M+) C17H25F3O2Si:
346.1576, Found 346.1567.
4.4.1. 4,4,4-Tifluoro-1-phenyl-1-triethylsilyloxy-1-butene (2Aa) and
(E)-1,1,1-trifluoro-4-phenyl-4-triethylsilyloxy-2-butene (10Aa)
The products were obtained as an inseparable mixture;
Combined yield: 90%; Isomeric ratio: 2Aa:10Aa = 95:5; E:Z of
2Aa = 0:100.
2Fa (Z isomer): 1H NMR (CDCl3)
(t, J = 8.03 Hz, 9H), 3.06 (dq, J = 7.19, 11.12 Hz, 2H), 3.83 (s, 3H),
4.88 (t, J = 7.19 Hz, 1H), 6.85–6.93 (m, 2H), 7.27–7.29 (m, 2H); 13
NMR (CDCl3) = 5.0, 6.4, 30.5–31.4 (m), 55.1, 100.09–100.13 (m),
110.6, 120.1, 126.6 (q, J = 276.0 Hz), 127.7, 129.8, 130.3, 151.7,
157.0; 19F NMR (CDCl3, CFCl3)
= À66.59 (t, J = 11.12 Hz, 3F);
(E isomer): 19F NMR (CDCl3, CFCl3)
= À67.10 (t, J = 12.40 Hz, 3F).
10Fa: 19F NMR (CDCl3, CFCl3)
= À64.02 (m, 3F).
d = 0.48 (q, J = 8.03 Hz, 6H), 0.88
C
d
Colorless liquid; IR (neat) 3063, 2959, 2914, 2879, 1654, 1458,
1447, 1414, 1362, 1331, 1286, 1258, 1137, 1092, 1005, 828, 767,
731, 698 cmÀ1: HRMS (FAB) Calcd for (M+) C16H23F3OSi: 316.1470,
Found 316.1480.
d
d
d
2Aa (Z isomer): 1H NMR (CDCl3)
d = 0.59 (q, J = 8.09 Hz, 6H),
0.92 (t, J = 8.09 Hz, 9H), 3.04 (dq, J = 6.99, 10.95 Hz, 2H), 5.05 (t,
J = 6.99 Hz, 1H), 7.31–7.33 (m, 3H), 7.44–7.47 (m, 2H); 13C NMR
4.4.5. 4,4,4-Trifluoro-1-(2-furyl)-1-triethylsilyloxy-1-butene (2Ga)
and (E)-1,1,1-Trifluoro-4-(2-furyl)-4-triethylsilyloxy-2-butene
(10Ga)
The products were obtained as an inseparable mixture;
Combined yield: 82%; Isomeric ratio: 2Ga:10Ga = 96:4; E:Z of
2Ga = 10:90.
(CDCl3)
J = 276.1 Hz), 128.1, 128.5, 128.6, 138.7, 154.6; 19F NMR (CDCl3,
CFCl3)
= À66.54 (t, J = 10.95 Hz, 3F).
10Aa: 19F NMR (CDCl3, CFCl3)
= À64.24 (d, J = 4.89 Hz, 3F).
d = 5.3, 6.5, 30.8–31.7 (m), 98.0–98.1 (m), 126.6 (q,
d
d
Colorless liquid; IR (neat) 2959, 2880, 1686, 1468, 1335, 1258,
1139, 1099, 1012, 805, 740 cmÀ1: HRMS (FAB) Calcd for (M+)
4.4.2. 4,4,4-Trifluoro-1-(4-methoxyphenyl)-1-triethylsilyloxy-1-
butene (2 Da) and (E)-1,1,1-trifluoro-4-(4-methoxyphenyl)-4-
triethylsilyloxy-2-butene (10 Da)
C
14H21F3O2Si: 306.1263, Found 306.1266.
2Ga (Z isomer): 1H NMR (CDCl3)
d
= 0.71 (q, J = 7.99 Hz, 6H),
The products were obtained as an inseparable mixture;
Combined yield: 95%; Isomeric ratio: 2Da:10Da = 92:8; E:Z of
2Da = 3:97.
0.98 (t, J = 7.99 Hz, 9H), 3.00 (dq, J = 7.34, 10.72 Hz, 2H), 5.26 (t,
J = 7.34 Hz, 1H), 6.38–6.40 (m, 2H), 7.35 (m, 1H); 13C NMR (CDCl3)
d
= 5.2, 6.6, 30.7 (q, J = 30.29 Hz), 96.45–96.54 (m), 107.2, 111.1,
Colorless liquid; IR (neat) 2958, 2880, 2839, 1893, 1655, 1577,
1464, 1442, 1415, 1333, 1255, 1137, 1092, 1005, 974, 940, 863,
126.3 (q, J = 276.10 Hz), 142.2, 145.2, 151.5; 19F NMR (CDCl3, CFCl3)
d
= À66.52 (t, J = 10.72 Hz, 3F).
787, 729 cmÀ1
:
HRMS (FAB) Calcd for (M+) C17H25F3O2Si:
(E isomer): 19F NMR (CDCl3, CFCl3)
d
= À67.35 (t, J = 12.40 Hz, 3F).
346.1576, Found 346.1579.
10Ga: 19F NMR (CDCl3, CFCl3)
d
= À64.42 (d, J = 7.14 Hz, 3F).
2 Da (Z isomer): 1H NMR (CDCl3)
d = 0.59 (q, J = 8.09 Hz, 6H),
0.92 (t, J = 8.09 Hz, 9H), 3.01 (dq, J = 7.19, 10.99 Hz, 2H), 3.82 (s,
3H), 4.94 (t, J = 7.19 Hz, 1H), 6.83–6.87 (m, 2H), 7.36–7.40 (m, 2H);
4.4.6. 4,4,4-Trifluoro-1-(1-naphthyl)-1-triethylsilyloxy-1-butene
(2Ha) and (E)-1,1,1-Trifluoro-4-(1-naphthyl)-4-triethylsilyloxy-
2-butene (10Ha)
The products were obtained as an inseparable mixture;
Combined yield: 87%; Isomeric ratio: 2Ha:10Ha = 96:4; E:Z of
2Ha = 2:98.
13C NMR (CDCl3)
d
= 5.2, 6.5, 31.2 (q, J = 30.1 Hz), 55.2, 96.5–96.6
(m), 113.4, 126.5 (q, J = 276.0 Hz), 127.4, 131.2, 154.2, 159.8; 19F
NMR (CDCl3, CFCl3)
= À66.60 (t, J = 10.99 Hz, 3F).
(E isomer): 19F NMR (CDCl3, CFCl3)
= À67.14 (t, J = 9.78 Hz, 3F).
d
d

N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
75
Colorless liquid; IR (neat) 3058, 2958, 2914, 2879, 1662, 1366,
1342, 1320, 1289, 1268, 1250, 1184, 1137, 1106, 1074, 1003, 842,
794, 778, 746 cmÀ1; HRMS (FAB) Calcd for (M+) C20H25F3OSi:
366.1627, Found 366.1634.
were dried over anhydrous Na2SO4, then filtered and concentrated
in vacuo. The resulting yellow liquid was purified by silica gel
column chromatography (Hexane/EtOAc = 5/1) to give the corre-
sponding 3-hydroxy-1,3-diphenyl-2-(2,2,2-trifluoroethyl)propan-
1-one (12Aa).
2Ha (Z isomer): 1H NMR (CDCl3)
d = 0.33 (q, J = 8.03 Hz, 6H),
0.76 (t, J = 8.03 Hz, 9H), 3.15 (dq, J = 7.04, 10.92 Hz, 2H), 4.94
(t, J = 7.04 Hz, 1H), 7.41–7.51 (m, 4H), 7.82–7.85 (m, 2H), 8.15–8.17
4.5.1. 3-Hydroxy-1,3-diphenyl-2-(2,2,2-trifluoroethyl)propan-1-one
(12Aa)
(m, 1H); 13C NMR (CDCl3)
d = 5.0, 6.4, 30.9 (q, J = 30.0 Hz), 100.6–
100.8 (m), 124.9, 126.0, 126.2, 126.3, 126.4, 126.6 (q, J = 276.1 Hz),
Yield: 59%; Diastereomeric ratio = 94:6.
Yellow liquid; IR (neat) 3464, 1670, 1600, 1512, 1456, 1421,
128.1, 129.0, 131.4, 133.5, 136.8, 154.2; 19F NMR (CDCl3, CFCl3)
d
= À66.60 (t, J = 10.92 Hz, 3F);
1369, 1311, 1261, 1207, 1173, 1145, 1108, 1027, 979, 771 cmÀ1
:
(E isomer): 19F NMR (CDCl3, CFCl3)
d
= À67.16 (t, J = 12.03 Hz,
HRMS (FAB) Calcd for (M+Na) C17H15F3O2Na: 331.0922, Found
331.0916.
3F);
10Ha: 19F NMR (CDCl3, CFCl3)
d
= À64.14 (d, J = 7.52 Hz, 3F).
Syn isomer: 1H NMR (CDCl3)
d
= 2.06–2.14 (m, 1H), 2.66–2.75
(m, 1H), 3.25–3.56 (m, 1H), 4.10 (ddd, J = 2.90, 7.54, 10.49 Hz, 1H),
4.85 (d, J = 7.54 Hz, 1H), 7.19–7.51 (m, 8H), 7.85–7.86 (m, 2H); 13
NMR (CDCl3) = 34.2 (q, J = 28.9 Hz), 46.31–46.33 (m), 76.4, 126.2
(q, J = 276.0 Hz), 126.3, 128.5, 128.7, 130.1, 133.5, 137.5, 140.9,
171.3, 202.4; 19F NMR (CDCl3, CFCl3)
= À64.94 (t, J = 9.78 Hz, 3F);
Anti isomer: 1H NMR (CDCl3)
= 2.45–2.56 (m, 1H), 2.82–2.95
(m, 1H).
4.4.7. 4,4,5,5,6,6,6-Heptafluoro-1-phenyl-1-triethylsiloxy-1-hexene
(2Ca)
The products were obtained as an inseparable mixture;
Combined yield: 87%; E:Z = 9:91.
Colorless liquid; IR (neat) 3063, 2960, 2916, 2881, 1655, 1494,
1460, 1447, 1415, 1354, 1325, 1199, 1045, 1006, 857, 809,
698 cmÀ1 HRMS (FAB) Calcd for (M+) C18H23F7OSi: 416.1406,
Found 416.1406.
C
d
d
d
4.5.2. syn-3-Hydroxy-1-(3-methoxyphenyl)-3-phenyl-2-(2,2,2-
trifluoroethyl)propan-1-one (12Ea)
Yield 58%; Yellow liquid; IR (neat) 3472, 2961, 2839, 1682,
1587, 1257, 1145, 945, 878, 830, 793, 681 cmÀ1: HRMS (FAB) Calcd
for (M+) C18H17F3O3: 338.1137, Found 338.1130; 1H NMR (CDCl3)
2Ca (Z isomer): 1H NMR (CDCl3)
0.91 (t, J = 7.79 Hz, 9H), 3.05 (dt, J = 6.96, 18.88 Hz, 2H), 5.08 (t,
J = 6.96 Hz, 1H), 7.38 (m, 5H); 13C NMR (CDCl3)
= 5.3, 6.4, 28.3 (t,
d = 0.58 (q, J = 7.79 Hz, 6H),
d
J = 22.3 Hz), 96.5–96.6 (m), 106.0–112.3 (m), 114.3–120.0 (m),
126.2, 126.3–128.6 (m), 128.2, 128.5, 138.8, 155.2; 19F NMR
d
= 2.04–2.10 (m, 1H), 2.64–2.73 (m, 1H), 3.19 (m, 1H), 3.74 (s, 3H),
4.09 (m, 1H), 4.81 (m, 1H), 7.03–7.05 (m, 1H), 7.21–7.31 (m, 5H),
7.40 (s, 1H), 7.48–7.49 (m, 2H); 13C NMR (CDCl3)
= 34.1 (q,
(CDCl3, CFCl3)
d
= À128.14 (s, 2F), À114.54 to À114.35 (m, 2F),
À81.08 (t, J = 9.78 Hz, 3F).
d
(E isomer): 19F NMR (CDCl3, CFCl3)
d
= À128.33 (s, 2F), À113.89
J = 28.9 Hz), 46.49–46.51 (m), 55.2, 76.4, 112.6, 119.9, 121.2, 126.2
(q, J = 276.3 Hz), 126.3, 128.4, 128.7, 129.5, 138.8, 140.9, 159.6,
to À112.12 (m, 2F), À80.88 (t, J = 9.78 Hz, 3F).
202.1; 19F NMR (CDCl3, CFCl3)
d
= À64.94 (t, J = 10.90 Hz, 3F).
4.4.8. 4,4-Difluoro-1-phenyl-1-triethylsilyloxy-1-butene (2Ba) and
(E)-1,1-difluoro-4-phenyl-4-triethylsilyloxy-2-butene (10Ba)
The products were obtained as an inseparable mixture;
Combined yield: 92%; Isomeric ratio: 2Ba:10Ba = 96:4; E:Z of
2Ba = 2:98.
References
[1] (a) Q. Chen, S. Tanaka, T. Fujita, L. Chen, T. Minato, Y. Ishikawa, M. Chen, N. Asao, Y.
Yamamoto, T. Jin, Chem. Commun. 50 (2014) 3344–3346;
(b) T. Matsumoto, T. Sasamori, H. Miyake, N. Tokitoh, Organometallics 33 (2014)
1341–1344;
Colorless liquid; IR (neat) 3060, 3027, 2960, 2914, 2878, 1652,
1493, 1459, 1414, 1393, 1242, 1179, 1117, 1068, 1006, 974, 834,
742, 698, 649 cmÀ1; HRMS (FAB) Calcd for (M+) C12H24F2OSi:
298.1564, Found 298.1572.
(c) G. Onodera, R. Hachisuka, T. Noguchi, H. Miura, T. Hashimoto, R. Takeuchi,
Tetrahedron Lett. 55 (2014) 310–313;
(d) A.J. Huckaba, T.K. Hollis, S.W. Reilly, Organometallics 32 (2013) 6248–6256;
(e) M. Rubio, J. Campos, E. Carmona, Org. Lett. 13 (2011) 5236–5239;
(f) M. Benohoud, S. Tuokko, P.M. Pihko, Chem. Eur. J. 17 (2011) 8404–8413;
(g) J.J. Dunsford, K.J. Cavell, B. Kariuki, J. Organomet. Chem. 696 (2011) 188–194;
(h) T. Sasamori, T. Matsumoto, N. Tokitoh, Polyhedron 29 (2010) 425–433;
(i) Y. Sumida, H. Yorimitsu, K. Oshima, J. Org. Chem. 74 (2009) 7986–7989;
(j) K. Okamoto, T. Hayashi, Org. Lett. 9 (2007) 5067–5069;
(k) M. Anada, M. Tanaka, K. Suzuki, H. Nambu, S. Hashimoto, Chem. Pharm. Bull.
54 (2006) 1622–1623.
2Ba (Z isomer): 1H NMR (CDCl3)
d = 0.62 (q, J = 7.83 Hz, 6H),
0.95 (t, J = 7.83 Hz, 9H), 2.80 (tdd, J = 17.58, 7.33, 4.50 Hz, 2H), 5.10
(t, J = 7.33 Hz, 1H), 5.87 (tt, J = 57.1, 4.50 Hz, 1H), 7.29–7.49 (m,
5H); 13C NMR (CDCl3)
d
= 5.3, 6.6, 31.6 (t, J = 22.3 Hz), 100.0 (t,
J = 7.0 Hz), 116.5 (t, J = 240.1 Hz), 125.9, 128.1, 128.2, 138.8, 153.6;
19F NMR (CDCl3, CFCl3)
d
= À115.61 to À115.37 (m, 2F);
[2] (a) J. Matsuo, M. Murakami, Angew. Chem. Int. Ed. 52 (2013) 9109–9118;
(b) B. Plancq, L.C. Justafort, M. Lafantaisie, T. Ollevier, Eur. J. Org. Chem. (2013)
6525–6529;
(E isomer): 19F NMR (CDCl3, CFCl3)
d
= À116.43 (dt, J = 56.03,
16.92 Hz, 2F).
10Ba: 19F NMR (CDCl3, CFCl3)
d
= À111.25 to À111.08 (m, 2F).
(c) T. Ollevier, B. Plancq, Chem. Commun. 48 (2012) 2289–2291;
(d) Y. Mei, D.J. Averill, M.J. Allen, J. Org. Chem. 77 (2012) 5624–5632;
(e) W. Wang, Q.-Y. Chen, Y. Guo, Synlett (2011) 2705–2708;
(f) Y. Mei, P. Dissanayake, M.J. Allen, J. Am. Chem. Soc. 132 (2010) 12871–12873;
(g) H. Yanai, Y. Yoshino, A. Takahashi, T. Taguchi, J. Org. Chem. 75 (2010)
5375–5378;
4.5. Aldol reaction of the silyl enol ethers with benzaldehyde in the
presence of TiCl4
(h) J. Jankowska, J. Paradowska, B. Rakiel, J. Mlynarski, J. Org. Chem. 72 (2007)
2228–2231;
(i) M.B. Boxer, H. Yamamoto, J. Am. Chem. Soc. 128 (2006) 48–49;
(j) T. Mukaiyama, Angew. Chem. Int. Ed. 43 (2004) 5590–5614;
(k) T. Hamada, K. Manabe, S. Ishikawa, S. Nagayama, M. Shiro, S. Kobayashi, J. Am.
Chem. Soc. 125 (2003) 2989–2996;
Typical procedure: A stirred solution of (Z)-1,1,1-trifluoro-4-
phenyl-2-buten-1-one (0.10 g, 0.5 mmol, 1.0 equiv) with triethyl-
silane (0.1 mL, 0.6 mmol, 1.2 equiv) and Co2(CO)8 (5 mg, 3 mol%) in
ClCH2CH2Cl (5 mL) was heated at the reflux temperature for 4 h.
Then the mixture was cooled to room temperature and then CH2Cl2
(5 mL) was added into the mixture. The whole was cooled to
À78 8C, and then TiCl4 (0.07 mL, 0.6 mmol, 1.2 equiv) and PhCHO
(0.06 mL, 0.6 mmol, 1.2 equiv) were added into the reaction
mixture at that temperature. After being stirred at À78 8C for
1 h, the reaction was quenched with H2O and the whole was
extracted with CH2Cl2 three times. The combined organic layers
(l) T.H. Chan, T. Aida, P.W.K. Lau, V. Gorys, D.N. Harpp, Tetrahedron Lett. (1979)
4029–4032;
(m) T. Mukaiyama, K. Banno, K. Narasaki, J. Am. Chem. Soc. 96 (1974) 7503–7509.
[3] (a) S. Basu, V. Gupta, J. Nickel, C. Schneider, Org. Lett. 16 (2014) 274–277;
(b) V. Gupta, V. Sai Sudhir, T. Mandal, C. Schneider, Angew. Chem. Int. Ed. 51
(2012) 12609–12612;
(c) Y. Inamoto, Y. Nishimoto, M. Yasuda, A. Baba, Org. Lett. 14 (2012) 1168–1171;
(d) A. Livieri, M. Boiocchi, G. Desimoni, G. Faita, Chem. Eur. J. 18 (2012)
11662–22668;

76
N. Ikeda, T. Konno / Journal of Fluorine Chemistry 173 (2015) 69–76
(e) H. Tamagaki, Y. Nawate, R. Nagase, Y. Tanabe, Chem. Commun. 46 (2010)
[10] (a) T. Konno, Synlett (2014) 1350–1370;
5930–5932;
(b) T. Nihei, T. Hoshino, T. Konno, Org. Lett. 16 (2014) 4170–4173;
(c) T. Konno, M. Kishi, T. Ishihara, S. Yamada, Tetrahedron 70 (2014) 2455–2463;
(d) T. Konno, M. Kishi, T. Ishihara, T. Beilstein, J. Org. Chem. 8 (2012) 2207–
2213;
(e) T. Konno, K. Taku, S. Yamada, K. Moriyasu, T. Ishihara, Org. Biomol. Chem. 7
(2009) 1167–1170;
(f) Y. Liu, Y. Zhang, N. Jee, M.P. Doyle, Org. Lett. 10 (2008) 1605–1608;
(g) W. Wang, H. Li, J. Wang, Org. Lett. 7 (2005) 1637–1639.
[4] (a) L. Li, Q.-Y. Chen, Y. Guo, J. Org. Chem. 79 (2014) 5145–5152;
(b) P.V. Pham, D.A. Nagib, D.W.C. MacMillan, Angew. Chem. Int. Ed. 50 (2011)
6119–6122;
(c) R. Heng, S.Z. Zard, Chem. Commun. 47 (2011) 3296–3298.
[5] (a) X.-H. Duan, H. Mayr, Org. Lett. 12 (2010) 2238–2241;
(b) K. Shibatomi, H. Yamamoto, Angew. Chem. Int. Ed. 47 (2008) 5796–5798;
(c) S. Hajra, M. Bhowmick, B. Maji, D. Sinha, J. Org. Chem. 72 (2007) 4872–4876;
(d) T. Shimada, M. Yoshioka, T. Konno, T. Ishihara, Org. Lett. 8 (2006) 1129–1131;
(e) M. Kimura, T. Yamazaki, T. Kitazume, T. Kubota, Org. Lett. 6 (2004) 4651–4654.
[6] (a) L. Zhu, C. Zhou, W. Yang, S. He, G.J. Cheng, X. Zhang, C.S. Lee, J. Org. Chem. 78
(2013) 7912–7929;
(f) T. Konno, A. Morigaki, K. Ninomiya, T. Miyabe, T. Ishihara, Synthesis (2008)
564–572;
(g) T. Konno, J. Chae, T. Tanaka, T. Ishihara, H. Yamanaka, J. Fluor. Chem. 127
(2006) 36–43;
(h) T. Konno, J. Chae, T. Tanaka, T. Ishihara, H. Yamanaka, Chem. Commun.
(2004) 690–691;
(i) J. Chae, T. Konno, M. Kanda, T. Ishihara, H. Yamanaka, J. Fluor. Chem. 120
(2003) 185–193.
(b) M.J. Schnermann, N.L. Untiedt, G. Jime´nez-Oseˆs, Angew. Chem. Int. Ed. 51
(2012) 9581–9586;
[11] K. Funabiki, K. Matsunaga, M. Nojiri, W. Hashimoto, H. Yamamoto, K. Shibata, M.
Matsui, J. Org. Chem. 68 (2003) 2853–2860.
(c) M.E. Jung, J.J. Chang, Org. Lett. 14 (2012) 4898–4901;
(d) T. Arai, T. Sato, H. Kanoh, K. Kaneko, K. Oguma, A. Yanagisawa, Chem. Eur. J. 14
(2008) 882–885;
[12] T. Yamazaki, K. Mizutani, T. Kitazume, J. Org. Chem. 60 (1995) 6046–6056.
[13] T. Konno, J. Chae, M. Kanda, G. Nagai, K. Tamura, T. Ishihara, H. Yamanaka,
Tetrahedron 59 (2003) 7571–7580.
(e) R. Sedrani, J. Kallen, L.M.M. Cabrejas, C.D. Papageorgiou, F. Senia, S. Rohrbach,
D. Wagner, B. Thai, J.A.M. Eme, J. France, L. Oberer, G. Rihs, G. Zenke, J. Wagner, J.
Am. Chem. Soc. 125 (2003) 3849–3859.
[14] The hydrosilylation of (E)-1-phenyl-2-buten-1-one under the same reaction con-
ditions (Co2(CO)8: 3 mol%, Et3SiH: 1.2 equiv, 1,2-dichloroethane, reflux, 4 h) took
placeverysmoothlytogivethecorresponding(Z)-silylenoletherin97%yield. (Z)-1-
phenyl-1-triethylsilyloxy-1-butene: known compound, 1H NMR (CDCl3) d 0.60 (q,
J = 8.19 Hz, 6H), 0.93 (t, J = 8.19 Hz, 9H), 1.04 (t, J = 7.19 Hz, 3H), 2.24 (dq, J = 7.39,
7.19 Hz, 2H), 5.12 (t, J = 7.39 Hz, 1H), 7.23–7.31 (m, 3H), 7.44–7.47 (m, 2H).
[15] The reaction mechanism of the hydrosilylation has been pooly understood at
present. Therefore the high stereoselectivity as well as the low regioselectivity of
the hydrosilylation using various silanes also remain unclear.
[16] In the case of the substrates having an alkyl side chain as R, the reaction
proceeded in a very low regio- and stereoselective manner to afford the mixture
of regioisomers, stereoisomers, and their desilylated compounds.
[17] (a) M.V. Vita, J. Waser, Org. Lett. 15 (2013) 3246–3249;
(b) L.C. Konkol, B.T. Jones, R.J. Thomson, Org. Lett. 11 (2009) 5550–5553;
(c) M. Anada, M. Tanaka, T. Washio, M. Yamawaki, T. Abe, S. Hashimoto, Org. Lett.
9 (2007) 4559–4562.
[7] (a) M.V. Vita, J. Waser, Org. Lett. 15 (2013) 3246–3249;
(b) M. Anada, M. Tanaka, T. Washio, M. Yamakawa, T. Abe, S. Hashimoto, Org. Lett.
9 (2007) 4559–4562;
(c) Y. Sato, H. Fujisawa, T. Mukaiyama, Chem. Lett. 34 (2005) 588–589;
(d) V. Russo, J. Allen, Z.T. Ball, Chem. Commun. (2009) 595–596;
(e) M. Turks, X. Huang, P. Vogel, Chem. Eur. J. 11 (2005) 465–476.
[8] (a) T.W. Lyons, M. Brookhart, Chem. Eur. J. 19 (2013) 10124–10127;
(b) X. Ping, Z. Wei, H. Zuo-gang, Z. Yue-xiong, Z. Chuan-jun, J. Biao, Synlett (2012)
2269–2273;
(c) T. Watanabe, H. Hashimoto, H. Tobita, J. Am. Chem. Soc. 129 (2007) 11338–
11339;
(d) D. Lee, J. Yun, Tetrahedron Lett. 46 (2005) 2036–2039;
(e) B.H. Lipshutz, W. Chrisman, K. Noson, P. Papa, J.A. Sclafani, R.W. Vivian, J.M.
Keith, Tetrahedron 56 (2000) 2779–2788.
[18] In general, it has been well known that the Mukaiyama aldol reaction of (E)- or
(Z)-silyl enol ether with aldehydes in the presence of Lewis acid provides the
corresponding syn adducts preferentially via open transition-state models. See,
Ref. [2a] and references cited therein.
[9] There have been quite limited studies on the hydrosilylation of fluorinated a,b-
carbonyl compounds. For example, see M.J. Burk, J.C. Calabrese, F. Davidson, R.L.
Harlow, D.C. Roe, J. Am. Chem. Soc. 113 (1991) 2209–2222.