Synthesis of fluoromethylated materials in ionic liquids

Article abstract of DOI:10.1016/S0022-1139(02)00006-4

Syntheses of fluoromethylated materials via Michael additions with the Baylis-Hillman type reaction and the reaction of fluoromethylated imines with enamines in ionic liquid are described.

Full text of DOI:10.1016/S0022-1139(02)00006-4

Journal of Fluorine Chemistry 115 (2002) 49±53
Synthesis of ¯uoromethylated materials in ionic liquids
Tomoya Kitazume*, Kenji Tamura, Zaiju Jiang,
Noriak Miyake, Isamu Kawasaki
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku Yokohama 226-8501, Japan
Received 17 September 2001; received in revised form 29 November 2001; accepted 9 January 2002
Abstract
Syntheses of ¯uoromethylated materials via Michael additions with the Baylis±Hillman type reaction and the reaction of ¯uoromethylated
imines with enamines in ionic liquid are described. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Micael addition; Ionic liquid; Enamine; Baylis±Hillman reaction
1. Introduction
2. Results and discussion
Extensive research has already been carried out on
incorporation of ¯uorine into molecules which can lead to
profound and unexpected results on biological activities
and/or physical properties [1,2]. Recent investigations in
this ®eld have opened up the possibility for synthesis by
employing biocatalysts [3], along with conventional chemi-
cal methods [4,5]. They are, however, commonly associated
with two major sources of waste: organic solvents and
catalysts (such as, enzyme or chemical catalyst). In synthetic
chemistry, the research regarding reusable media such as
¯uorous ¯uids [6,7] and molten salts (ionic liquids) [8,9] is
focused on the reaction media. Especially, the study of
reusable media such as molten salts (ionic liquids) is an
important for organic synthesis [8,9]. Recently, we have
reported the design and utility of a reusable reaction system
derived from an ionic liquid and tri¯uoromethane sulfonic
acid or rare earth salts for carbon±carbon bond forming
reactions, and we demonstrated the af®nity between the
ionic liquids and the catalysts [10].
2.1. Michael addition reaction in ionic liquid
While it is well known that the Baylis±Hillman reaction
[11] is a valuable synthetic reaction to obtain the functio-
nalized materials, this reaction system is limited in its
practicality by poor reaction rates. Based on the several
attempts made to increase the rate of this reaction through
either physical or chemical means [12], reaction solvents
[13] such as water or ¯uorinated solvents result in increased
rates as a result of hydrophobic and ¯uorophobic effects,
respectively. Further, it is reported that the formation of
Lewis acids±1,4-diaza-bicyclo-[2,2,2]-octane (DABCO)
complex accelerates the Baylis±Hillman reaction via the
metal complex with the reaction intermediate [14]. There-
fore, we examined the ®rst example of the Michael additions
via the Baylis±Hillman type reaction using activated ole®ns
towards a,b-unsaturated ketones as a chiral auxiliary in the
DABCO±ionic liquid system. In this reaction system, the
reaction of (4S)-3-[(E)-4,4,4-tri¯uorobut-2-enoyl]-4-isopro-
pyl-2-oxazolidinone with activated vinyl moiety proceeded
at 80 8C, giving the corresponding material as shown in
Table 1. The generally accepted mechanism [11] shown in
Scheme 1 involves the Michael addition of DABCO to the
activated carbon±carbon bond, followed by an addition to
the a,b-unsaturated ketone. Subsequent elimination releases
the catalyst, and the cycle continues. Unfortunately, these
addition reactions provide low diastereoface selectivity in
the reusable ionic liquid±DABCO system. The diastereo-
mers 1b derived from entry 6 were separated by column
chromatography, affording one diastereomer ([a]29D ‡ 85:1
For our continuous studies on the reusable reaction sys-
tem, we would like to describe the utility of ionic liquid as a
reusable medium for the synthesis of ¯uoromethylated
materials based on the Michael addition via Baylis±Hillman
reaction, and the reaction of ¯uoromethylated imines with
acetone derivatives in the L±proline±Lewis acid±ionic liquid
system.
* Corresponding author. Tel.: ‡81-45-924-5754; fax: 81-45-924-5780.
E-mail address: tkitazum@bio.titech.ac.jp (T. Kitazume).
0022-1139/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PI I : S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 0 0 6 - 4

50
T. Kitazume et al. / Journal of Fluorine Chemistry 115 (2002) 49±53
Table 1
the CF3CHXY group, and the coupling patterns of protons
C(CF3)CHaHbCO (doublet doublet, JHaÀHb ˆ 18:4 Hz,
Michael addition reaction
Ionic liquida
Yield (%) drb
JHaÀHc ˆ4:67 Hz at 3.41 ppm; JHaÀHb ˆ18:4 Hz, JHbÀHc
ˆ
Entry
Z (compound number)
10:4 Hz at 3.60 ppm) support the interaction of proton with
CHc(CF3) group. 13C NMR spectra have 15 signals contain-
ing two alkenyl carbon atoms (d 114±130 ppm), CF3 carbon
atom (d 125.856 ppm, quartet, J ˆ 279:1 Hz) and carbonyl
carbon atoms (d 153.830, 165.837, 168.819 ppm). From the
results of 1H, 19F and 13C NMR spectra, we have determined
that the structure of the obtained material is the Michael
adduct.
1
2
3
4
5
6
7
CN (1a)
[emim][OTf]
[emim][OTf]
[emim][OTf]
[bmim][BF4]
[bmim][PF6]
[emim][OTf]
[emim][OTf]
37
1:1
25c
30d
46
1:1
1:1
1:1
23
1:1
CO2Me (1b)
COMe (1c)
27
42
1:1
55:45
a Ionic liquids: [emim][OTf]; 1-ethyl-3-methyl-1H-imidazolium tri-
fluoromethane-sulfonate: [bmim[[BF4]; 1-butyl-3-methyl-1H-imidazoIium
In view of `green chemistry', reuse of the catalyst and
solvent are preferable [15]. From the results shown in Table 1
(entries 1±3), successive reuse of the recovered ionic liquid
1-ethyl-3-methyl-1H-imidozolium tri¯uoromethane-sulfo-
nate ([emim][OTf]) in the same reaction yielded amounts
of product as high as in the ®rst cycle.
tetrafluoro-borate: [bmim][PF6]; 1-butyl-3-methyl-1H-imidazolium hexa-
fluoro-phosphonate.
b Diastereomeric ratio.
c Second cycle.
d Third cycle.
2.2. The reaction using L-proline±Lewis acid±ionic liquid
system
In the next step, we have carried out the reaction of
¯uoromethylated imines with enamines generated from
acetone derivatives and L-proline in an ionic liquid. In this
reaction system, the reaction did not proceed in the absence
of Lewis acid. In the presence of Sc(OTf)3, the reaction
smoothly proceeded, giving a ¯uoromethylated carbinol.
Proposed reaction mechanism is shown in Fig. 1. At ®rst,
enamine 3 and H2O were produced from the reaction of
corresponding ketone and L-proline, and then the produced
H2O attacked on imine to produce the N,O-hemiacetal in the
presence of Lewis acid (Sc(OTf)3). The N,O-hemiacetal
reacted with enamine 3 in the presence of Lewis acid, giving
the reaction intermediate 5. This intermediate 5 was con-
verted to the b-hydroxyketone 6 with small amount of water
contained in ionic liquids Table 2.
Scheme 1. Mechanism for addition reaction.
(c 0.853, CHCl3)) and another ([a]29D ‡ 23:9 (c 0.942,
CHCl3)). The structure of compounds 1 was con®rmed by
1H, 19F and 13C NMR spectra and coupling constants (JH±H).
In the case of compound 1b (Z ˆ CO2Me, [a]29D ‡ 85:1
(c 0.853, CHCl3)), the coupling pattern of ¯uorine (doublet,
J ˆ 9:48 Hz) supports the interaction of protons with
In the case of methyl ethyl ketone, the compound 6
(X ˆ Me) was not isolated. Based on the main product
Fig. 1. Proposed reaction mechanism.

T. Kitazume et al. / Journal of Fluorine Chemistry 115 (2002) 49±53
51
Table 2
318 mg, 6 mmol) were added, and then the whole was stirred
at 60 8C. After 4 h of stirring at that temperature, the product
was extracted with diethyl ether (5Â 15 ml) and then ionic
liquid [emim][OTf] was recovered. The organic layer was
dried over anhydrous MgSO4, and then the solvent was
removed. Products were puri®ed by column chromatogra-
phy on silica gel using a mixture of hexane-ethyl acetate
(3:1) as an eluent, giving (4S)-3-[3-(tri¯uoromethyl)-
4-cyano-4-pentenoyl]-4-isopropyl-2-oxazolidinone 1a in
37% yield with diastereomeric ratio (1:1).
Synthesis of fluoromethylated carbinols 6
Entry
RF
X
Yield (%)
Diastereomeric ratio
1
2
3
4
5
6
CF3
H
37
66
25a
18
27
65
CHF2
CF3
H
Me
OH
OH
Cl
CF3
90:10
83:17
63:37
CHF2
CF3
a Yield of EtCOCH2CH(OH)CF3.
(EtCOCH2CH(OH)CF3), it seems that the regioselectivity
depends on the stability of produced enamines (enamine A is
stable more than enamine B).
3.2.2. Second cycle
Into the recovered ionic liquid, (4S)-3-[(E)-4,4,4-tri-
¯uorobut-2-enoyl]-4-isopropyl-2-oxazolidinone (756 mg,
3 mmol), DABCO (329 mg, 3 mmol) and acrylnitrile
(0.4 ml, 318 mg, 6 mmol) were added, and worked-up simi-
larly. Compound 1a was obtained in 25% yield and ionic
liquid was recovered.
Diastereomer mixture: 1H NMR (CDCl3): d 0.89 (3H, d,
J ˆ 6:86 Hz), 0.90 (3H, d, J ˆ 6:86 Hz), 2.36 (1H, heptd.,
J ˆ 7:14, 3.58 Hz), 3.38±3.71 (3H, m), 4.24±4.63 (3H, m),
6.17 (1H, d, J ˆ 2:47 Hz), 6.26 (1H, d, J ˆ 2:47 Hz). 19F
NMR (CDCl3): d 91.40 (d, J ˆ 7:76 Hz), 91.45 (d,
J ˆ 8:61 Hz). 13C NMR (CDCl3): d 14.569, 14.592,
17.798, 17.881, 28.265, 33.384 (q, J ˆ 2:0 Hz), 33.480
(q, J ˆ 2:0 Hz), 43.684 (q, J ˆ 28:63 Hz), 43.802 (q,
J ˆ 28:63 Hz), 58.427, 58.621, 63.735, 115.868, 115.937,
116.608, 116.635, 124.805 (q, J ˆ 279:7 Hz), 137.282,
137.486, 153.603, 167.975, 168.013. Anal. Calc. for
C113H15F3N2O3: C, 51.32; H, 4.97; N, 9.21. Found: C,
51.63; H, 4.71; N, 9.08. IR (KBr): 1794, 1686 cmÀ1 (C=O).
The structure of carbinols 6 was con®rmed by 1H, 19F and
13C NMR spectra and coupling constants (JH±H). In the case
of carbinol 6 (RF ˆ CF3, X ˆ H), the coupling pattern of
proton Y±CH(CF3) (doublet of quartet of doublet, J ˆ 9:16,
6.84, 2.93 Hz) supports the interaction of protons with Y±
CH(CF3)CHaHb group. 13C NMR spectra have ®ve signals
containing three alkyl carbon atoms (d 25±75 ppm), CF3
carbon atoms (d 124.467 ppm, quartet, J ˆ 280:0 Hz) and
carbonyl carbon atom (d 206.274 ppm). From the results of
13C NMR and 1H NMR spectra, we have determined that the
structure of the obtained material is carbinol with CF3 group.
In conclusion, we have shown that ionic liquids are proved
to be good alternative reaction media for the synthesis of the
¯uorinated materials.
3.3. Preparation of (4S)-3-[3-(trifluoromethyl)-4-
methoxycarbonyl-4-pentenoyl]-4-isopropyl-2-
oxazolidinone (1b)
In the above reaction, (4S)-3-[(E)-4,4,4-tri¯uorobut-2-
enoyl]-4-isopropyl-2-oxazolidinone (756 mg, 3 mmol),
DABCO (329 mg, 3 mmol) and methyl acrylate (6 mmol)
were used in ionic liquid [emim][OTf] (4 g), and then
worked-up similarly, giving (4S)-3-[3-(tri¯uoromethyl)-4-
methyloxocarbonyl-4-pentenoyl]-4-isopropyl-2-oxazolidi-
none (diastereomers) in 27% yield.
Diasteeomer A 12%: [a]29D ‡ 85:1 (c 0.853, CHCl3). 1H
NMR (CDCl3): d 0.82 (3H, d, J ˆ 6:86 Hz), 0.88 (3H, d,
J ˆ 6:87 Hz), 2.30 (1H, m), 3.41 (1H, dd, J ˆ 18:4,
4.67 Hz), 3.60 (1H, dd, J ˆ 18:4, 10.4 Hz), 3.84 (3H, s),
4.20±4.31 (4H, m), 5.94 (1H, s), 6.55 (1H, s). 19F NMR
(CDCl3): d 91.25 (d, J ˆ 9:48 Hz). 13C NMR (CDCl3): d
14.639, 17.944, 28.293, 35.364, 38.801 (q, J ˆ 28:06 Hz),
52.614, 58.559, 63.658, 114.231, 115.246 (d, J ˆ 12:31 Hz),
125.856 (q, J ˆ 279:1 Hz), 128.439, 153.830, 165.837,
168.819. IR (KBr): 1789, 1721 cmÀ1 (C=O).
3. Experimental
3.1. General
All commercially available reagents were used without
1
further puri®cation. Chemical shifts of H (300 MHz) and
13C NMR (75 MHz) spectra were recorded in ppm (d)
down®eld from the following internal standard (Me4Si, d
0.00) in CDCl3. The 19F (282 MHz) NMR spectra were
recorded in ppm down®eld from internal standard C6F6 in
CDCl3 using a VXR 300 instrument.
3.2. Preparation of (4S)-3-[3-(trifluoromethyl)-4-cyano-
4-pentenoyl]-4-isopropyl-2-oxazolidinone (1a)
3.2.1. First cycle
In the [emim][OTf] (4 g), (4S)-3-[(E)-4,4,4-tri¯uorobut-
2-enoyl]-4-isopropyl-2-oxazolidinone (756 mg, 3 mmol),
DABCO (329 mg, 3 mmol) and acrylnitrile (0.4 ml,
Diastereomer B 15%: [a]29D ‡ 23:9 (c 0.942, CHCl3). 1H
NMR (CDCl3): d 0.87 (3H, d, J ˆ 7:14 Hz), 0.90 (3H, d,
J ˆ 7:14 Hz), 2.37 (1H, m), 3.48±3.51 (2H, m), 3.84 (3H, s),

52
T. Kitazume et al. / Journal of Fluorine Chemistry 115 (2002) 49±53
4.24±4.42 (4H, m), 5.95 (1H, s), 6.57 (1H, s). 19F NMR
(CDCl3): d 91.21 (d, J ˆ 9:47 Hz). 13C NMR (CDCl3): d
14.522, 17.993, 28.137, 35.505, 38.655 (q, J ˆ 28:06 Hz),
52.618, 58.487, 63.551, 114.873 (d, J ˆ 6:87 Hz), 115.634
(d, J ˆ 12:6 Hz), 125.873 (q, J ˆ 279:1 Hz), 128.617,
153.781, 165.856, 168.804. IR (KBr): 1779, 1718 cmÀ1
(C=O).
56.0, 10.3 Hz). 13C NMR (CDCl3): d 30.467, 42.637
(t, J ˆ 2:58 Hz), 66.715 (t, J ˆ 24:3 Hz), 115.294 (t,
J ˆ 243:3 Hz), 207.177.
3.7. Preparation of 1,1,1-trifluoro-2-hydroxyhexan-
4-one (6c)
In the above reaction, imine (RF ˆ CF3, 5 mmol), L-
proline (0.25 mmol) and ethyl methyl ketone (10 mmol)
in ionic liquid ([emim][OTf], 3 g) were used, and then
worked-up similarly, giving 1,1,1-tri¯uoro-2-hydroxy-
3.4. (4S)-3-[3-(Trifluoromethyl)-4-acetyl-4-pentenoyl]-
4-isopropyl-2-oxazolidinone (1c)
1
In the above reaction, (4S)-3-[(E)-4,4,4-tri¯uorobut-2-
enoyl]-4-isopropyl-2-oxazolidinone (756 mg, 3 mmol),
DABCO (329 mg, 3 mmol) and methyl vinyl ketone
(6 mmol) were used in ionic liquid [emim][OTf] (4 g),
was used, and then worked-up similarly, giving (4S)-3-[3-
(tri¯uoromethyl)-4-acetyl-4-pentenoyl]-4-isopropyl-2-oxa-
zolidinone in 42% yield.
hexan-4-one in 25% yield. H NMR (CDCl3): d 1.09 (3H,
t, J ˆ 7:15 Hz), 2.54 (2H, q, J ˆ 7:15 Hz), 2.75 (1H, dd,
J ˆ 17:58, 3.29 Hz), 2.83 (1H, J ˆ 17:58, 9.07 Hz), 3.85
(OH), 4.51 (1H, m). 19F NMR (CDCl3): d 82.2 (d,
J ˆ 6:90 Hz). 13C NMR (CDCl3): d 7.526, 36.984, 41.408,
66.785 (q, J ˆ 32:35 Hz), 124.480 (q, J ˆ 220:28 Hz),
208.979.
1H NMR (CDCl3): d 0.83 (3H, d, J ˆ 6:90 Hz), 0.88 (3H,
d, J ˆ 7:20 Hz), 2.25 (1H, m), 2.28±2.39 (1H, m), 2.40 (3H,
s), 3.44 (2H, d, J ˆ 7:50 Hz), 4.22 (1H, dd, J ˆ 8:55,
2.70 Hz), 4.28±4.43 (1H, m), 4.36 (1H, dd, J ˆ 7:80,
3.60 Hz), 6.15 (1H, s), 6.37 (1H, s). 19F NMR (CDCl3): d
91.61 (d, J ˆ 9:31 Hz). 13C NMR (CDCl3): d 14.579,
17.712, 25.220, 28.281, 35.273, 36.425 (q, J ˆ 27:6 Hz),
58.396, 63.616, 125.797 (q, J ˆ 277:1 Hz), 127.452,
143.211, 153.739, 168.641, 196.486. IR (KBr): 1786,
1715, 1683 cmÀ1 (C=O).
3.8. Preparation of 1,1,1-trifluoro-2,3-
dihydroxypentan-4-one (6d)
In the above reaction, imine (RF ˆ CF3, 5 mmol) and
hydroxyacetone (10 mmol) were used, and then worked-up
similarly, giving 1,1,1-tri¯uoro-2,3-dihydroxypentan-4-one
in 18% yield.1H NMR (CDCl3): d 2.35 (3H, s), 4.35 (1H, qd,
J ˆ 6:84, 1.23 Hz), 4.43 (1H, d, J ˆ 1:23 Hz). 19F NMR
(CDCl3): d 84.9 (d, J ˆ 6:10 Hz). 13C NMR (CDCl3): d
25.068, 69.273 (q, J ˆ 31:5 Hz), 74.423 (q, J ˆ 1:43 Hz),
123.788 (q, J ˆ 282:9 Hz), 205.075. IR: 3418 (OH),
1719 cmÀ1 (C=O).
3.5. Preparation of 1,1,1-trifluoro-2-hydroxypentan-
4-one (6a)
A mixture of acetone (10 mmol), imine (RF ˆ CF3,
1.01 g, 5 mmol), L-proline (0.230 g, 0.25 mmol) and [emi-
m][OTf] (3 g) was stirred at room temperature. After stirring
of 48 h at that temperature, organic materials were extracted
with diethyl ether (10Â 4 ml), and ionic liquid containing
L-proline was recovered. The organic layer was dried over
anhydrous MgSO4, and then the solvent was removed. The
resultant crude product was decomposed to produce the title
material by chromatography on silica gel.
1H NMR (CDCl3): d 2.26 (3H, s), 2.79 (1H, dd, J ˆ 17:8,
2.81 Hz), 2.87 (1H, dd, J ˆ 17:8, 9.27 Hz), 3.64 (OH), 4.89
(CH, dqd, J ˆ 9:16, 6.84, 2.93 Hz). 19F NMR (CDCl3): d,
82.2 (d J ˆ 6:09 Hz) from C6F6. 13C NMR (CDCl3): d
30.770, 42.796, 66.425 (q, J ˆ 32:35 Hz), 124.467 (q,
J ˆ 280:0 Hz), 206.274. IR: 3423 (OH), 1719 cmÀ1 (C=O).
3.9. Preparation of 1,1-difluoro-2,3-dihydroxypentan-
4-one (6e)
In the above reaction, imine (RF ˆ CHF2, 5 mmol) and
hydroxyacetone (10 mmol) were used, and then worked-up
similarly, giving 1,1-di¯uoro-2,3-dihydroxypentan-4-one in
1
27% yield. Main: H NMR (CDCl3): d 2.38 (3H, s), 4.18
(1H, m), 4.40 (1H, d) 5.85 (1H, td, J ˆ 56:3, 6.04 Hz). 19F
NMR (CDCl3): d 30.85 (ddd, J ˆ 292:1, 57.7, 10.3 Hz),
33.59 (ddd, J ˆ 292:1, 55.2, 10.3 Hz). 13C NMR (CDCl3): d
25.220, 70.747 (dd, J ˆ 27:49, 23.19 Hz), 75.532, 114.724
(t, J ˆ 243:3 Hz), 207.000.
1
Minor: H NMR (CDCl3): d 2.39 (3H, s), 4.18 (1H, m),
4.38 (1H, d), 5.90 (1H, td, J ˆ 55:8, 4.39 Hz). 19F NMR
(CDCl3): d 33.53 (ddd, J ˆ 291:3, 54.3, 5.17 Hz), 28.23
(ddd, J ˆ 291:3, 56.0, 14.7 Hz). 13C NMR (CDCl3): d
26.620, 71.317 (dd, J ˆ 25:19, 22.62 Hz), 75.612,
114.450 (t, J ˆ 243:3 Hz), 207.100.
3.6. Preparationof 1,1-difluoro-2-hydroxypentan-4-one (6b)
In the above reaction, imine (RF ˆ CHF2, 5 mmol) was
used, and worked-up similarly, giving 1,1-di¯uoro-2-hydro-
xypentan-4-one in 66% yield.1H NMR (CDCl3): d 2.06 (3H,
s), 2.60 (2H, d, J ˆ 6:04 Hz), 3.25 (1H), 4.25 (1H, m),5.78
(1H, td, J ˆ 55:8, 3.57 Hz). 19F NMR (CDCl3): d 32.96
(ddd, J ˆ 288:7, 55.2, 9.18 Hz), 29.90 (ddd, J ˆ 288:7,
3.10. Preparation of 1,1,1-trifluoro-2-hydroxy-3-
chloropentan-4-one (6f)
In the above reaction, imine (RF ˆ CF3, 5 mmol) and
chloroacetone (10 mmol) were used, and then worked-up

T. Kitazume et al. / Journal of Fluorine Chemistry 115 (2002) 49±53
53
(b) B. Betzemeier, P. Knochel, Angew. Chem. Int. Ed. Engl. 36
(1997) 2623±2624;
similarly, giving 1,1,1-tri¯uoro-2-hydroxy-3-chloropentan-
4-one in 65% yield.
(c) I.T. Horvath, J. Rabai, Science 266 (1994) 72±75.
[7] (a) H. Nakano, T. Kitazume, Green Chem. 1 (1999) 21±22;
(b) H. Nakano, T. Kitazume, Green Chem. 1 (1999) 179±182;
(c) T. Kitazume, T. Ishizuka, M. Takeda, K. Itoh, Green Chem. 1
(1999) 221±224; and references cited therein.
Diastereomer mixture: 1H NMR (CDCl3): d 2.43 (3H, s),
2.45 (3H, s), 3.01, 3.49 (OH), 4.39 (1H, d, J ˆ 6:04 Hz),
4.54 (1H, d, J ˆ 2:19 Hz). 19F NMR (CDCl3): d 85.7 (d,
J ˆ 6:11 Hz), 86.7 (d, J ˆ 6:10 Hz). 13C NMR (CDCl3): d
27.678, 28.050, 55.907, 60.892, 69.034 (q, J ˆ 32:1 Hz),
71.755 (q, J ˆ 31:2 Hz), 123.310 (q, J ˆ 282:3 Hz),
123.452 (q, J ˆ 282:6 Hz), 201.217, 201.262. IR: 3431
(OH), 1723 cmÀ1 (C=O).
[8] (a) C.E. Song, F.J. Roh, Chem. Commun. (2000) 837;
(b) J.N. Rosa, C.A.M. Asonso, A.C. Santos, Tetrahedron 57 (2001)
4189;
Â
(c) V.Le. Boulaire, R. Gree, Chem. Commun. (2000) 2195;
(d) K.K. Laali, V.J. Gettwert, J. Org. Chem. 66 (2001) 35;
(e) K.K. Laali, V.J. Gettwert, J. Fluorine Chem. 107 (2001) 31;
(f) J. Peng, Y. Deng, Tetrahedron Lett. 42 (2001) 403;
(g) R.R. Deshmukh, R. Rajageopal, K.V. Srinivasan, Chem.
Commun. (2001) 1544;
References
(h) H. Hagiwara, Y. Shimizu, T. Hoshi, T. Suzuki, M. Ando, K.
Ohkubo, C. Yokoyama, Tetrahedron Lett. 42 (2001) 4349.
[9] (a) T. Kitazume, F. Zulfiqar, G. Tanaka, Green Chem. 2 (2000) 133±
136;
[1] I. Ojima, J.R. McCarthyl, J.T. Welch (Eds.), Biomedical Frontiers of
Fluorine Chemistry, ACS Symposium Series 639, ACS, Washington,
DC, 1996.
[2] P.V. Ramachandran (Ed.), Asymmetric Fluoroorganic Chemistry,
ACS Symposium Series 746, ACS, Washington, DC, 1999.
[3] T. Kitazume, T. Yamazaki, Topics Curr. Chem. 193 (1997) 91±130.
[4] (a) P. Bravo, G. Resnati, Tetrahedron: Asym. 1 (1990) 661±692;
(b) K. Iseki, Tetrahedron 54 (1998) 13887±13914; and references
cited therein;
(b) F. Zul®qar, T. Kitazume, Green Chem. 2 (2000) 137±139;
(c) T. Kitazume, G. Tanaka, J. Fluorine Chem. 106 (2000) 211±215;
(d) T. Kitazume, K. Kasai, Green Chem. 3 (2001) 30±32.
[10] Z. Jiang, T. Kitazume, in: Proceedings of the 2000 International
Symposium on Organic Reactions, Tokyo, Japan, 2000.
[11] E. Ciganek, Org. React. 51 (1997) 201±350.
[12] (a) J.S. Hill, N.S. Isaacs, J. Phys. Org. Chem. 3 (1990) 285±288;
(b) G.H.P. Roos, P. Rampersach, Synth. Commun. 23 (1993) 1261±
1266;
(c) N. Shibata, E. Suzuki, Y. Takeuchi, J. Am. Chem. Soc. 122
(2000) 10728±10729;
(d) Y. Takeuchi, E. Suzuki, A. Satoh, T. Shiragami, N. Shibata,
J. Org. Chem. 64 (1999) 5708±5711;
(c) S. Rafel, J.W. Leahy, J. Org. Chem. 62 (1997) 1521±1522.
[13] J. Auge, N. Lubin, A. Lubineau, Tetrahedron Lett. 35 (1994) 7947±
7948.
(e) L. Hintermann, A. Togni, Angew. Chem. Int. Ed. 39 (2000)
4359±4362.
[5] (a) T. Sakamoto, K. Takahashi, T. Yamazaki, T. Kitazume, J. Org.
Chem. 65 (2000) 9467±9474; and references cited therein;
(b) T. Yamazaki, M. Ando, T. Kitazume, T. Kubota, M. Omura, Org.
Lett. 1 (1999) 905±908;
[14] V.K. Aggarwal, A. Mereu, G.J. Tarver, R. McCague, J. Org. Chem.
63 (1998) 7183±7189; and references cited therein.
[15] (a) P. Tundo, P.T. Anastas, Green Chemistry: Challenging Perspec-
tives, Oxford Science, Oxford, 1999;
(c) Y. Komatsu, T. Sakamoto, T. Kitazume, J. Org. Chem. 64 (1999)
8369±9374.
[6] (a) A. Ogawa, D.P. Curran, J. Org. Chem. 62 (1997) 450±451;
(b) P. Wasserscheid, W. Keim, Angew. Chem. Int. Ed. Engl. 39
(2000) 3772±3789; and references cited therein.