Configurational assignments in trifluoromethylvinyl compounds using through-space carbon-fluorine coupling constants

Article abstract of DOI:10.1002/(SICI)1097-458X(1998100)36:10<761::AID-OMR370>3.0.CO;2-3

Long-range carbon-fluorine coupling constants, ⁿJ(C,F) (n ≥> 4), were observed for up to six-bond separated nuclei in some substituted trifluoromethylvinyl compounds (CF₃CX=CYZ). When the ⁿJ(C,F) in a Z-isomer are compared with those in the corresponding E-isomer, the ⁿ(C,F) in one isomer whose substituent including the coupled carbon is proximate to the trifluoromethyl group are always larger than those in the other isomer. Because the coupling constants are transmitted through space, the ⁿJ(C,F) decrease with increase in the spatial distance of the carbon and the fluorine. This relationship can be used to determine the configurational assignments in the two stereoisomers even in the case where only one isomer is obtained.

Full text of DOI:10.1002/(SICI)1097-458X(1998100)36:10<761::AID-OMR370>3.0.CO;2-3

MAGNETIC RESONANCE IN CHEMISTRY
Magn. Reson. Chem. 36, 761È765 (1998)
Conügurational assignments in triýuoromethylvinyl
compounds using through-space carbon–ýuorine
coupling constants
Koshi Matsubara,1* Ayumi Oba1 and Yoshihiro Usui2¤
1 Tsukuba Research Center, Mitsubishi Chemical Corporation, 8-3-1 Chuo, Ami, Inashiki, Ibaraki 300-0397, Japan
2 Rhoü ne-Poulenc Yuka Agro KK, 8-3-1 Chuo, Ami, Inashiki, Ibaraki 300-0397, Japan
Received 18 February 1998; revised 14 May 1998; accepted 15 May 1998
ABSTRACT: Long-range carbonÈÑuorine coupling constants, nJ(C,F) (n P 4), were observed for up to six-bond
separated nuclei in some substituted triÑuoromethylvinyl compounds (CF CXxCYZ). When the nJ(C,F) in a
3
Z-isomer are compared with those in the corresponding E-isomer, the nJ(C,F) in one isomer whose substituent
including the coupled carbon is proximate to the triÑuoromethyl group are always larger than those in the other
isomer. Because the coupling constants are transmitted through space, the nJ(C,F) decrease with increase in the
spatial distance of the carbon and the Ñuorine. This relationship can be used to determine the conÐgurational
assignments in the two stereoisomers even in the case where only one isomer is obtained. ( 1998 John Wiley &
Sons, Ltd.
KEYWORDS: NMR; 1H NMR; 13C NMR; 19F NMR; J(C,F); conÐgurational assignment; triÑuoromethylvinyl compounds
INTRODUCTION
tution pattern of the vinyl group and the type of the
substituents; the 4J(H,F) and 19F chemical shift can be
applied only to the isomers which separately possess a
triÑuoromethyl group and a proton on the two oleÐnic
carbons, and the 3J(C,F) can be applied to trisubsti-
tuted oleÐnic compounds with a triÑuoromethyl and an
alkoxy or amino group on the same oleÐnic carbon.
Therefore, it is desirable to develop a new method
which has a more general applicability to the wide
range of triÑuoromethylvinyl compounds.
Fluorine is often introduced into biologically active
compounds to improve their activity by enhancement of
the lipophilicity and the change in both steric and elec-
tronic properties.1h4 During the synthesis of tri-
Ñuoromethylvinyl compounds, both conÐgurational
isomers,
Z and E, are often produced simulta-
neously.5h7 Hence their separation and identiÐcation
are indispensable to the examination of each isomer
regarding its biological activities.
The through-space transmission of a spinÈspin coup-
ling between spatially proximate nuclei has been studied
The Z- and E-isomers of 1,2-disubstituted oleÐnic
compounds can be easily distinguished by comparing
the size of the 3J(H,H)8 for the two oleÐnic protons or
the NOE9 for the protons near the double bond; the
Z-isomer shows a smaller 3J(H,H) and a larger NOE.
In general, an increase in the number of substituents
makes the di†erentiation of the isomers difficult because
the 3J(H,H) cannot be used in tri- or tetrasubstituted
oleÐns and the NOE sharply decreases with the spatial
distance between the nuclei.
both
experimentally13,14
and
theoretically.15,16
Unusually large long-range carbonÈÑuorine coupling
constants, nJ(C,F), have been reported in molecules with
rigid chemical structures, e.g. the Ðve-bond 13CÈ19F
coupling of 24.0 Hz for the C-4 methyl carbon and the
Ñuorine in 1,4,8-trimethyl-5-Ñuorophenanthrene13 and
the six-bond 13CÈ19F coupling of 5.5 Hz for the C-1
carbon and the F-12 Ñuorine in 9,10,11,12-tetraÑuoro-5,
6-dihydrobenzo[b]naphth[2,1-f]oxepin.17
The conÐguration in substituted triÑuoromethylvinyl
compounds can be assigned by other methods using
such features as 4J(H,F),10 19F chemical shift,11 3J(C,F),
12 and heteronuclear NOE between a proton and a
Ñuorine. However, the application of these methods to
the conÐgurational assignment is limited by the substi-
We have recently found that smaller but explicit nJ(C,
F) are observed even in Ñexible molecules when the
digital resolution in their 13C NMR spectra is increased
sufficiently. In this paper, we report the nJ(C,F) in some
triÑuoromethylvinyl compounds and demonstrate that
the nJ(C,F) can be utilized to determine the E and Z
conÐguration.
* Correspondence to: K. Matsubara, Materials Characterization and
Analysis Laboratory, Tsukuba Research Center, Mitsubishi Chemical
Corporation, 8-3-1 Chuo, Ami, Inashiki, Ibaraki 300-0397, Japan
E-mail: 3709437=cc.m-kagaku.co.jp
¤ Present address: Yokohama Research Center, Mitsubishi Chemical
Corporation, 1000 Kamoshida, Aoba, Yokohama, Kanagawa 227-
8502, Japan.
RESULTS AND DISCUSSION
The 1H and 13C NMR spectra of compounds 1È5 (Fig.
1) were assigned using conventional NMR techniques
such as DQF-COSY,18 DEPT,19 HETCOR20 and
( 1998 John Wiley & Sons, Ltd.
CCC 0749-1581/98/100761È05 $17.50

762
K. MATSUBARA, A. OBA AND Y. USUI
Figure 1. Structures and numbering of the triýuoromethylvinyl compounds investigated.
COLOC.21 The assignments of Z- and E-isomers were
conÐrmed based on the several parameters listed in
Table 1 as mentioned below. The 3J(C-9,H-2) of 5.9 Hz
in 1Z is less than that of 8.2 Hz in 1E,22 and the NOE
between H-2 and H-10 was observed only in 1Z. In the
1HM19FN-NOE di†erence spectra shown in Fig. 2, the
heteronuclear NOE between F-1 and H-3 at 7.81 ppm
was observed only in 2Z and that between F-1 and
H-10 at 7.54 ppm was observed only in 2E. The smaller
3J(C-1,H-3), the larger 4J(H-3,F-1) and the larger odFo in
2Z than those in 2E are consistent with the assignment.
The conÐgurational assignments of 3Z and 3E were
conÐrmed in a way similar to that for 2Z and 2E. The
two ethoxycarbonyl substituents in 4 were di†erentiated
using the three-bond protonÈcarbon coupling; 3J(C-4,
H-2) of 6.9 Hz is less than 3J(C-7,H-2) of 11.4 Hz. The
conÐguration of 5 was determined using the 1HM19FN-
NOE di†erence technique.
The carbonÈÑuorine coupling constant can be easily
obtained in the 1H-decoupled 13C NMR spectra
because a distinct quartet is observed when a carbon is
coupled to the three equivalent Ñuorine nuclei. Table 2
shows the absolute value of the carbonÈÑuorine coup-
ling constants observed in compounds 1È5. No attempt
was made to obtain the relative sign of the coupling
constants. The 1J(C,F) are about 275 Hz, the 2J(C,F)
are in the range 30È40 Hz and the 3J(C,F) are in the
range 2È6 Hz. These coupling constants are mainly
transmitted through chemical bonds and rapidly
decrease with increase in the number of intervening
Figure 2. (a) 1HM19FN-NOE diþerence and (b) 1H NMR
spectra of 2Z and (c, d) the corresponding spectra of 2E.
Table 1. Chemical shifts (ppm), coupling constants (Hz) and NOEs for conügu-
rational assignments
Compound
d(F-1)
4J(H-3, F-1)
3J(C,H)
NOEa
1Z
1E
2Z
2E
3Z
3E
4
[53.7
[57.9
[60.3
[54.6
[65.9
[62.6
[62.1
[61.8
5.9 (C-9, H-2)
8.2 (C-9, H-2)
7.6 (C-1, H-3)
13.0 (C-1, H-3)
6.3 (C-1, H-3)
H-10MH-2N
n.o.
1.5
n.o.b
1.2
H-3MF-1N
H-10MF-1N
H-3MF-1N
n.o. HMFN
n.o. HMFN
H-8MF-1N
n.o.
12.7 (C-1, H-3)
6.9 (C-4, H-2), 11.4 (C-7, H-2)
5
a Observed NOEs are listed; the irradiated nuclei are shown in braces and the observed nucleus pre-
cedes the braces.
b Not observed.
( 1998 John Wiley & Sons, Ltd.
MAGNETIC RESONANCE IN CHEMISTRY, VOL. 36, 761È765 (1998)

CONFIGURATIONAL ASSIGNMENTS IN TRIFLUOROMETHYLVINYL COMPOUNDS
763
Table 2. Carbon–ýuorine coupling constants (Hz)a
Compound
C-1
C-2
C-3
C-4
C-5
C-7
C-8
C-9
C-10
1Z
1E
2Z
2E
3Z
3E
4
272.3
273.3
275.2
275.7
275.2
275.5
271.4
276.1
39.7
35.8
30.2
33.5
34.9
35.7
36.4
39.4
5.9
5.1
5.7
2.8
3.9
2.8
5.1
1.9
0.4
n.o.b
0.5
n.o.
0.4
0.8
1.4
0.8
2.6
n.o.
n.o.
0.4
n.o.
1.1
0.9
0.4
0.7
n.o.
2.4
1.1
5
0.7
0.5
a Absolute value is shown.
b Not observed.
chemical bonds. For further separated nuclei, smaller
nJ(C,F) can be detected. The 5J(C-4,F) and the 6J(C-5,F)
in 1Z are 0.4 and 0.5 Hz, respectively, while those in 1E
were not observed. On the other hand, the 5J(C-10,F) in
1Z is 0.8 Hz and that in 1E is 1.4 Hz. Larger nJ(C,F)
were observed in the conÐgurational isomer in which
the phenyl or 4-methylphenylsulfonyl substituent con-
taining the coupled carbons is spatially proximate to
the triÑuoromethyl group. A similar tendency was
found in the pair 2Z and 2E. The 4J(C-9,F) and 5J(C-
10,F) in 2Z were less than the corresponding coupling
constants in 2E. Further, the 5J(C-9,F) in 3Z was not
observed whereas that in 3E was 1.1 Hz. Because the
linewidths at half-height of the protonated carbons such
as C-6, C-7 and C-11 in 3Z and 3E are less than 0.5 Hz
and the linewidth of C-10 in 3E probably becomes
broader owing to the unresolved long-range carbonÈ
Ñuorine coupling, the fact that the linewidths of C-10 in
3Z and 3E are 0.5 and 0.9 Hz, respectively, are well
explained. The 4J(C-7,F) of 1.1 Hz is larger than the
4J(C-4,F) of 0.4 Hz in 4. All of the observed nJ(C,F) and
the linewidths have derived the rule that when the nJ(C,
F) are compared between Z- and E-isomers, the more
spatially proximate carbonÈÑuorine assumes larger
values. Therefore, nJ(C,F) can be used as a criterion for
the determination of the conÐgurational isomers.
Compounds 1È4 are all trisubstituted oleÐnic com-
pounds and the remaining oleÐnic proton can play a
key role in determining the conÐguration through the
measurement of 3J(C,H), 4J(F,H) and 1HM1HN-NOE.
Compound 5 is a tetrasubstituted oleÐnic compound,
and only one isomer is obtained as a major product. In
this compound, 4J(C-8,F-1), 5J(C-9,F-1) and 6J(C-10,F-
1) are 2.4, 0.7 and 0.5 Hz, respectively, and 4J(C-5,F-1),
6J(C-6,F-1) and 7J(C-7,F-1) were not observed. Because
the six-bond arrangement from F-1 to C-10 is not rigid
and also unconjugated, there must be a contribution of
the through-space transmission of the coupling. Accord-
ingly, the Z conÐguration can be determined for 5 even
though only one isomer is obtained. The 5J(H-8,F-1) of
1.1 Hz is also ascribed to the through-space transmis-
sion of the coupling.
distinguished using the 3J(C,H) and also the 4J(C,F) in
the way described before. However, the 1HM19FN-NOE
di†erence spectrum could not distinguish the two eth-
oxycarbonyl groups because the methylene protons,
H-8, are very far from the triÑuoromethyl group and the
protons are expected to relax predominantly due to the
dipoleÈdipole interaction within the methylene and the
methyl protons. This example demonstrates the
superiority of the nJ(C,F) method to the 1HM19FN-NOE
method in distinguishing the conÐgurational isomers.
The nJ(C,F) basically decrease with the increase in the
spatial distance of the two nuclei;14 therefore, the con-
formation of a compound considerably inÑuences the
size of nJ(C,F) through the change in the internuclear
distance. However, the nJ(C,F) are not only dependent
on the spatial distance of the two nuclei. The quatern-
ary carbons C-9 in 1E and C-8 in 3E did not show any
recognizable 4J(C,F), whereas 4J(C-8,F-1) in 5 is 2.4 Hz
even though the spatial distances between the carbon
and the Ñuorine are supposed to be the same for the
three compounds. This result can be ascribed to the
lack of an intermediate proton for the quaternary
carbons; the proton plays an important role in trans-
mitting the spin information.16
Besides the conÐgurational assignments in triÑuoro-
methylvinyl compounds described in this paper, the
through-space carbonÈÑuorine coupling constant may
be utilized for other purposes, e.g. the assignment of the
stereoisomers for Ñuorine-containing cyclic compounds,
the 13C NMR assignment for the carbon which is spa-
tially proximate to a Ñuorine nucleus in a Ñourine-
containing compound and even the investigation of a
conformational preference in a favorable situation.
EXPERIMENTAL
Synthesis of compounds
4-Methylphenyl(3,3,3-triýuoro-1-phenyl-1-propenyl)sulfone
(1Z, 1E) and 4-methylphenyl[2-phenyl-1-(triýuoromethyl)-1-
ethenyl]sulfone (2Z, 2E). To a suspension of NaH (60%, 0.72 g,
0.018 mol) in DMF (4 ml) was added a DMF (4 ml) solution of p-
toluenethiol (2.24 g, 0.018 mol) dropwise at room temperature. After
stirring for 30 min, this solution was added to a DMF (6 ml) solution
It is interesting to compare 1HM19FN-NOE with nJ(C,
F) as the methods to identify the conÐgurational
isomers. The two ethoxycarbonyl groups in 4 could be
( 1998 John Wiley & Sons, Ltd.
MAGNETIC RESONANCE IN CHEMISTRY, VOL. 36, 761È765 (1998)

764
K. MATSUBARA, A. OBA AND Y. USUI
of 2-chloro-1-phenyl-3,3,3-triÑuoropropene6 (3.10 g, 0.015 mol) at
60¡C and stirred for 30 min at the same temperature. The reaction
mixture was poured into iceÈwater, extracted with diethyl ether and
the ether layer was washed with 1 M NaOH solution and brine. The
extract was dried with magnesium sulfate and concentrated. The
crude material was dissolved in acetic acid (20 ml) and treated with
hydrogen peroxide (30%, 10 ml) at 70¡C and stirred at 100¡C for 3 h.
After saturated aqueous Na SO had been cautiously added to the
62.7 (C-6), 118.3 (C-4), 119.2 (C-1), 127.6 (C-12), 128.3 (C-10), 128.8 (C-
11), 134.1 (C-9), 134.9 (C-2), 136.0 (C-3), 163.1 (C-5).
NMR experiments
2
3
solution, the mixture was poured into iceÈwater. The precipitates were
Ðltered o† and dried to give the product. Each isomer was isolated by
preparative HPLC (LC-20, Japan Analytical Industry) on an octa-
decylsilylated gel column (YMC-Pack ODS/D, YMC) using
acetonitrileÈwater (65 : 35, v/v) as the mobile phase at a Ñow-rate of
9.5 ml min~1. The UV detector was set at 220 nm. 1Z: 1H NMR,
d \ 2.38 (s, 3H, H-8), 6.10 [q, 1H, J(H,F) \ 8.8 Hz, H-2], 7.19 (d, 2H,
J \ 8.4 Hz, H-6), 7.22 (d, 2H, H-10), 7.27 (t, 2H, J \ 7.3 Hz, H-11),
7.36 (tt, 1H, J \ 7.2, 2.2 Hz, H-12), 7.50 (d, 2H, J \ 8.4 Hz, H-5); 13C
NMR, d \ 21.7 (C-8), 120.2 (C-1), 127.4 (C-2), 128.3 (C-11), 129.0 (C-5),
129.5 (C-10), 129.7 (C-6), 130.0 (C-12), 133.2 (C-9), 135.2 (C-4), 145.5
(C-7), 153.3 (C-3). 1E: 1H NMR, d \ 2.41 (s, 3H, H-8), 7.00 (d, 2H,
H-10), 7.13 [q, 1H, J(H,F) \ 7.3 Hz, H-2], 7.22 (d, 2H, J \ 8.2 Hz,
H-6), 7.27 (t, 2H, J \ 7.6 Hz, H-11), 7.38 (tt, 1H, J \ 7.4, 2.0 Hz, H-12),
7.43 (d, 2H, J \ 8.4 Hz, H-5); 13C NMR, d \ 21.7 (C-8), 121.5 (C-1),
124.9 (C-2), 128.0 (C-9), 128.0 (C-11), 129.2 (C-5), 129.6 (C-10), 129.7
(C-6), 129.9 (C-12), 133.2 (C-4), 145.6 (C-7), 153.3 (C-3). 2Z: 1H NMR,
d \ 2.36 (s, 3H, H-8), 7.13 (d, 2H, J \ 8.6 Hz, H-6), 7.33 (d, 2H, H-10),
7.33 (m, 2H, H-11), 7.38 (m, 1H, H-12), 7.46 (d, 2H, J \ 8.4 Hz, H-5),
7.81 [q, 1H, J(H,F) \ 1.5 Hz, H-3]; 13C NMR, d \ 21.6 (C-8), 121.4
(C-1), 128.0 (C-11), 128.2 (C-5), 129.2 (C-10), 129.3 (C-6), 130.3 (C-12),
130.8 (C-9), 134.9 (C-2), 137.2 (C-4), 145.1 (C-7), 145.8 (C-3). 2E: 1H
NMR, d \ 2.45 (s, 3H, H-8), 7.36 (d, 2H, J \ 8.6 Hz, H-6), 7.45 (m,
2H, H-11), 7.47 (m, 1H, H-12), 7.54 (d, 2H, J \ 8.0 Hz, H-10), 7.83 (d,
2H, J \ 8.4 Hz, H-5), 8.40 (s, 1H, H-3); 13C NMR, d \ 21.7 (C-8),
121.0 (C-1), 128.4 (C-5), 128.8 (C-11), 130.0 (C-6), 130.3 (C-10), 130.7
(C-9), 131.6 (C-12), 131.7 (C-2), 136.7 (C-4), 145.2 (C-7), 148.3 (C-3).
NMR spectra were recorded at 297 K on a JEOL
JNM-GSX400 spectrometer operating at 399.8 and
100.5 MHz for 1H and 13C, respectively, and a Varian
Gemini 300 spectrometer operating at 282.3 MHz for
19F. The NMR sample was prepared by dissolving 5È50
mg of each compound in 0.6 ml of CDCl in a 5 mm
3
NMR tube. The chemical shifts are reported in parts
per million vs. internal tetramethylsilane for 1H and 13C
and external trichloroÑuoromethane for 19F. The condi-
tions for 1H NMR were a 40¡ pulse angle, a 10 s delay
between pulses, a 4.0 kHz spectral width, 32K data
points and 32 scans. The conditions for survey 13C
NMR spectra were a 60¡ pulse angle, a 3 s delay
between pulses, a 22.0 kHz spectral width, 32K data
points and more than 512 scans. For the measurement
of nJ(C,F), the spectral width was narrowed and the
number of data points was increased to give a digital
resolution of better than 0.14 Hz and no window func-
tion before Fourier transformation was employed. The
3J(C,H) were obtained from 1H-coupled 13C NMR
spectra. The conditions for 19F NMR were a 40¡ pulse
angle, a 10 s delay between pulses, a 65.4 kHz spectral
width, 64K data points and 32 scans. For the assign-
ment of 1H and 13C NMR spectra, DQF-COSY,
DEPT, HETCOR and COLOC were carried out using
standard pulse sequences. 1HM19FN-NOE di†erence
spectra with a 30 s saturation time were obtained on a
JEOL JNM-GSX270 spectrometer equipped with a 1H
(270.2 MHz) and 19F (254.2 MHz) dual probe. The dis-
solved oxygen was removed by repeating a freezeÈthaw
cycle Ðve times before the measurement.
1-(4-Chlorophenyl)-3-[ (4,6-dimethyl-2-pyrimidinyl)thio ] -4,4,4-
triýuoro-2-buten-1-one (3Z, 3E). 1-(4-Chlorobenzoyl)-3,3,3-tri-
Ñuoroacetone (3a) was prepared by Claisen condensation between
ethyl triÑuoroacetate and p-chloroacetophenone according to the
method given in the literature.23 1-(4-Chlorobenzoyl)-3,3,3-triÑuoro-2-
triÑuoromethylsulfonyloxypropene (3b) was prepared from 3a and tri-
Ñuoromethanesulfonic anhydride in the presence of NaH. A DMF (25
ml) solution of 4,6-dimethyl-2-mercaptopyrimidine (1.7 g, 0.012 mol)
was gradually added to a suspension of NaH (60%, 0.48 g, 0.012 mol)
in DMF (15 ml) under ice cooling and stirred at room temperature for
30 min followed by adding a DMF (12 ml) solution of 3b (3.8 g, 0.010
mol) and stirring the resulting mixture at room temperature for
several hours. The reacted mixture was poured into water and
extracted with ethyl acetate. The ethyl acetate layer was washed with
brine, dried with magnesium sulfate and concentrated. The mixture
was chromatographed on a silica gel column [hexaneÈethyl acetate
(4 : 1)] to a†ord 3Z (2.0 g, 53%) and 3E (0.39 g, 11%). 3Z: 1H NMR,
d \ 2.26 (s, 6H, H-7), 6.70 (s, 1H, H-6), 7.30 (d, 2H, J \ 8.6 Hz, H-11),
7.66 [q, 1H, J(H,F) \ 1.2 Hz, H-3], 7.90 (d, 2H, J \ 8.6 Hz, H-10);
13C NMR, d \ 23.4 (C-7), 117.1 (C-6), 121.9 (C-1), 128.7 (C-11), 129.6
(C-2), 130.4 (C-10), 133.9 (C-9), 139.7 (C-3), 140.5 (C-12), 167.1 (C-4),
167.5 (C-5), 188.9 (C-8). 3E: 1H NMR, d \ 2.47 (s, 6H, H-7), 6.85 (s,
1H, H-6), 7.49 (d, 2H, J \ 8.8 Hz, H-11), 7.32 (s, 1H, H-3), 8.23 (d, 2H,
J \ 8.8 Hz, H-10); 13C NMR, d \ 23.7 (C-7), 117.2 (C-6), 121.5 (C-1),
126.0 (C-2), 129.0 (C-11), 130.9 (C-10), 133.4 (C-9), 140.9 (C-12), 146.7
(C-3), 167.8 (C-5), 168.8 (C-4), 189.5 (C-8).
REFERENCES
1. G. A. Patani and E. J. LaVoie, Chem. Rev. 96, 3147 (1996).
2. R. E. Banks, B. E. Smart and J. C. Tatlow (Eds), OrganoÑuorine
Chemistry: Principles and Commercial Applications. Plenum Press,
New York (1994).
3. R. Filler (Ed.), Biochemistry Involving CarbonÈFluorine Bonds.
ACS Symposium Series No. 28, American Chemical Society,
Washington, DC (1976).
4. R. Filler and Y. Kobayashi (Eds), Biomedical Aspects of Fluorine
Chemistry. Elsevier Biomedical Press, Amsterdam (1982).
5. T. Okano, T. Uekawa and S. Eguchi, Bull. Chem. Soc. Jpn. 62,
2575 (1989).
6. M. Fujita and T. Hiyama, Bull. Chem. Soc. Jpn. 60, 4377 (1987).
7. F. Camps, F. J. Sanchez and A. Messeguer, Synthesis 823 (1988).
8. L. M. Jackman and S. Sternhell, Applications of Nuclear Magnetic
Resonance Spectroscopy in Organic Chemistry, 2nd ed. Pergamon
Press, New York (1969).
9. D. Neuhaus and M. Williamson, T he Nuclear Overhauser E†ect in
Structural and Conformational Analysis. VCH, New York (1989).
10. D. J. Burton, R. L. Johnson and R. T. Bogan, Can. J. Chem. 44,
635 (1966).
Diethyl 2-(2,2,2-triýuoroethylidene)malonate (4). Compound 4
was prepared according to the method given in the literature.24 1H
NMR, d \ 1.33 (t, 3H, H-6), 1.34 (t, 3H, H-9), 4.32 (q, 2H, H-5), 4.36
(q, 2H, H-8), 6.76 [q, 1H, J(H,F) \ 7.7 Hz, H-2]; 13C NMR, d \ 12.9
(C-6), 12.9 (C-9), 61.7 (C-8), 62.2 (C-5), 121.1 (C-1), 126.7 (C-2), 135.7
(C-3), 160.9 (C-4), 161.9 (C-7).
Ethyl (Z)-2-benzyl-4,4,4-triýuoro-3-triýuoromethylsulfonyloxy-
2-butenoate (5). To a suspension of NaH (60%, 2.64 g, 0.066 mol) in
pentane (120 ml) at room temperature was added ethyl 2-benzyl-4,4,4-
triÑuoroacetoacetate25 (16.44 g, 0.060 mol) dropwise. After stirring for
30 min, triÑuoromethanesulfonic anhydride (18.62 g, 0.066 mol) was
added dropwise at 0¡C. The reaction mixture was stirred for 30 min at
room temperature, then Ðltered and the Ðltrate was concentrated.
Compound 5 (14.9 g, 61%) was isolated by column chromatography
(hexaneÈethyl acetate). 1H NMR, d \ 1.15 (t, 3H, H-7), 3.97 [q, 2H,
5J(H,F) \ 1.1 Hz, H-8], 4.18 (q, 2H, H-6), 7.19 (d, 2H, H-10), 7.29 (t,
2H, H-11), 7.31 (t, 1H, H-12); 13C NMR, d \ 13.5 (C-7), 34.2 (C-8),
11. F. Camps, R. Canela, J. Coll, A. Messeguer and A. Roca, T etra-
hedron 34, 2179 (1978).
12. J. P. Begue, D. Bonnet-Delpon, D. Mesureur and M. Ourevitch,
Magn. Reson. Chem. 29, 675 (1991).
13. F. R. Jerome and K. L. Servis, J. Am. Chem. Soc. 94, 5896 (1972).
( 1998 John Wiley & Sons, Ltd.
MAGNETIC RESONANCE IN CHEMISTRY, VOL. 36, 761È765 (1998)

CONFIGURATIONAL ASSIGNMENTS IN TRIFLUOROMETHYLVINYL COMPOUNDS
765
14. L. C. Hsee and D. J. Sardella, Magn. Reson. Chem. 28, 688 (1990).
20. A. Bax and G. A. Morris, J. Magn. Reson. 42, 501 (1981).
15. R. H. Contreras, C. G. Giribet, M. A. Natiello, J. Perez, I. D. Rae
21. H. Kessler, C. Griesinger, J. Zarbock and H. R. Loosli, J. Magn.
Reson. 57, 331 (1984).
and J. A. Weigold, Aust. J. Chem. 38, 1779 (1985).
16. I. D. Rae, A. Sta†a, A. C. Diz, C. G. Giribet, M. C. Ruiz de Azu

a
22. U. Vogeli and W. von Philipsborn, Org. Magn. Reson. 7, 617
and R. H. Contreras, Aust. J. Chem. 40, 1923 (1987).
(1975).
17. C. R. Jones, J. J. Parlow and D. M. Schnur, J. Heterocycl. Chem.
33, 1835 (1996).
23. J. C. Reid and M. Calvin, J. Am. Chem. Soc. 72, 2948 (1950).
24. C. Ates, Z. Janousek and H. G. Viehe, T etrahedron L ett. 34, 5711
(1993).
18. U. Piantini, O. W. SÔrensen and R. R. Ernst, J. Am. Chem. Soc.
104, 6800 (1982).
25. J. P. Begue, M. Charpentier-Morize and G. Nee, J. Chem. Soc.,
19. D. M. Doddrell, D. T. Pegg and M. R. Bendall, J. Magn. Reson.
48, 323 (1982).
Chem. Commun. 83 (1989).
( 1998 John Wiley & Sons, Ltd.
MAGNETIC RESONANCE IN CHEMISTRY, VOL. 36, 761È765 (1998)