Synthesis and Reactions of (2,2,2-Trifluoroethyl)triphenylphosphonium Trifluoromethanesulfonate

Article abstract of DOI:10.1002/ejoc.200300395

(2,2,2-Trifluoroethyl)triphenylphosphonium trifluoromethanesulfonate (triflate) (1) was readily synthesized in high yield from triphenylphosphane and 2,2,2-trifluoroethyl triflate. The Wittig olefination of 1 with aromatic aldehydes bearing electron-withdrawing groups with CsF as a base in DMF proceeded cleanly, producing the corresponding 3,3,3-trifluoropropenylidene compounds in good yields. On the other hand, the hydrolysis of 1 in methanol containing sodium hydroxide gave (2,2-dimethoxyvinyl)triphenylphosphonium triflate (6a) in high yield instead of the corresponding (2,2,2-trifluoroethyl)diphenylphosphane oxide. Furthermore, reactions between 1 and secondary amines exclusively gave the novel (Z)-(2-amino-2-fluorovinyl)triphenylphosphonium triflates (10) in high yields. Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300395

FULL PAPER
Synthesis and Reactions of (2,2,2-Trifluoroethyl)triphenylphosphonium
Trifluoromethanesulfonate
Takeshi Hanamoto,*[a] Noriko Morita,[a] and Keiko Shindo[a]
Keywords: Aldehydes / Synthetic methods / Triflates / Wittig reactions / Fluorine
(2,2,2-Trifluoroethyl)triphenylphosphonium
trifluorome- dium hydroxide gave (2,2-dimethoxyvinyl)triphenylphos-
thanesulfonate (triflate) (1) was readily synthesized in high
yield from triphenylphosphane and 2,2,2-trifluoroethyl tri-
phonium triflate (6a) in high yield instead of the correspond-
ing (2,2,2-trifluoroethyl)diphenylphosphane oxide. Further-
flate. The Wittig olefination of 1 with aromatic aldehydes more, reactions between 1 and secondary amines exclusively
bearing electron-withdrawing groups with CsF as a base in
DMF proceeded cleanly, producing the corresponding 3,3,3-
trifluoropropenylidene compounds in good yields. On the
other hand, the hydrolysis of 1 in methanol containing so-
gave the novel (Z)-(2-amino-2-fluorovinyl)triphenylphos-
phonium triflates (10) in high yields.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
Results and Discussion
Organofluorine compounds bearing trifluoromethyl
groups continue to be of great interest, due to their poten- 1. Preparation of (2,2,2-Trifluoroethyl)triphenylphos-
tial for materials science and biological science.[1] The devel- phonium Triflate (1)
opment of new methods through which to introduce the
The reported synthesis of 1 by Umemoto et al. suffered
from serious drawbacks such as operational difficulty, re-
trifluoromethyl group into organic compounds therefore re-
mains an important task. An attractive method for the
quirement for a multistep sequence, and the use of hazard-
preparation of such compounds is to use suitable building
ous reagents.[3a] Since this was not acceptable for use as
blocks bearing the trifluoromethyl group.[2] Although much
a general synthetic reagent, a new convenient method was
effort towards the preparation of such new building blocks
required. Previously we had developed an efficient method
has been made, few studies have been devoted to the syn-
for the synthesis of (1-fluorovinyl)triphenylphosphonium
thesis and applications of (2,2,2-trifluoroethyl)triphenyl-
triflate, using the quaternization of the corresponding (1-
phosphonium salts.[3] One of their attractive potential appli-
fluorovinyl)diphenylphosphane with diphenyliodonium
cations should be the Wittig olefination with aldehydes to
triflate in the presence of CuI.[4] This method was applied
introduce the 3,3,3-trifluoropropenyl moiety into organic
to the preparation of 1, but our attempt to carry out the
molecules, but related studies were not explored in detail.[3a]
quaternization of (2,2,2-trifluoroethyl)diphenylphosphane[6]
This lack of attention might be due to the difficulty encoun-
with diphenyliodonium triflate under similar conditions
tered in the preparation of these salts.
turned out not to be readily applicable for 1. The best effort
As part of our ongoing research in the development of
afforded 1 only in low yield (ഠ22%), as a sticky brown oil
(equation 1 in Scheme 1).
new fluorinating systems,[4] we became interested in de-
veloping a facile synthetic route to (2,2,2-trifluoroethyl)tri-
phenylphosphonium triflate (1), with the goal of examining
its large potential for the construction of trifluoromethyl-
ated organic compounds. This paper describes the facile
preparation of 1 and its related Wittig olefination as a use-
ful reaction for introduction of the 3,3,3-trifluoropropenyl-
idene moiety into aldehydes.[5] In addition, the different re-
activity of 1 with alkoxides and amines is demonstrated.
[a]
Department of Chemistry and Applied Chemistry, Saga
University,
Honjyo-machi, Saga 840-8502, Japan
Fax: (internat.) ϩ81-(0)952-288548
E-mail: hanamoto@cc.saga-u.ac.jp
Scheme 1. Preparation of 1
Eur. J. Org. Chem. 2003, 4279Ϫ4285
DOI: 10.1002/ejoc.200300395
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4279

T. Hanamoto, N. Morita, K. Shindo
FULL PAPER
We then turned out attention to an ordinary preparation lary GC-MS analysis, and the geometrical isomers were
with triphenylphosphane and 2,2,2-trifluoroethyl triflate. characterized by their 1H NMR spectra. A factor of slightly
To our delight, this method worked well without any diffi- preferential formation of the Z isomers might be attribu-
culties. The reaction between 2,2,2-trifluoroethyl triflate table to the lack of stabilizing effects on the generated beta-
and triphenylphosphane in dry toluene at 100 °C for 2 days ines, in comparison with the generated β-oxide diphenyl-
afforded 1 as a white solid in 85% yield (equation 2 in phosphane reported by Ishibashi et al.[5] However, the ef-
Scheme 1). Its 1H NMR spectrum shows methylene proton fects of the reaction conditions on these relative E/Z ratios
signals at δ ϭ 4.83 (ppm) as a double quadruplet attribu- have not been studied in detail, due to their low selectivity
table to one phosphane and three fluorines. It is also note- (Scheme 2).
worthy that 1 is very stable and easy to handle under stand-
ard conditions, in contrast to the corresponding phos-
phonium iodide described previously.[3b]
2. Wittig Olefination with Aromatic Aldehydes
Although Umemoto et al. had already very briefly re-
ported the Wittig olefination of 1 with benzaldehyde,[3a] we
initially performed the Wittig reaction between 1 and 4-
methoxybenzaldehyde. The use of conventional bases such
as tBuOK, LDA, nBuLi, and NaH resulted in no formation
of olefinic product and the decomposition of 1, but the use
of CsF for this olefination gave some, albeit low, level of
success.[3a,7] We therefore conducted the reaction with 2.3
equivalents of CsF both as base and as fluoride ion source
in DMF at room temperature to obtain 2 as a mixture of
the E and Z isomers in poor yield.[8] As one solution to this
Scheme 2. Possible mechanism of Wittig olefination of 1
problem, we assumed that certain electronic requirements
in the benzene ring might have to be fulfilled for this Wittig
These results suggested the following considerations con-
reaction. As might be expected, the reaction with aromatic
cerning a possible reaction mechanism:
aldehydes bearing strongly electron-withdrawing groups
i. Neither ylide 3 nor phosphorane 4 had lifetimes long
proceeded smoothly, affording the corresponding 3,3,3-tri-
enough to react with aldehydes.
fluoropropenylidene compounds as mixtures of E and Z
ii. As a result, rapid dehydrofluorination (ϪHF) from 3
isomers in high yields.[9] These results are summarized in
or 4 afforded the corresponding (2,2-difluorovinyl)tri-
Table 1. As some of these products are quite volatile, small
phenylphosphonium salt 5, which could not be isolated
losses of material cannot be avoided during the workup and
from the reaction mixture. However, if 5 were to be attacked
purification. The reaction with benzaldehyde, bearing no
again by a fluoride anion at the β-position, 3 or 4 should
electron-withdrawing group on the benzene ring, resulted in
be regenerated in situ. The regenerated species reacted with
a low yield (entry 7), while Wittig olefination with an ordi-
aldehydes to give the olefinic products.
nary aliphatic aldehyde afforded no olefinic product (entry
9). The E/Z ratios in the products were determined by capil-
3. Reactivity of 1 in Aqueous Alcohols Containing Sodium
Hydroxide
Table 1. Wittig reactions between 1 and various aldehydes
In order to examine other reaction behavior of 1, we next
performed the hydrolysis of 1 with excess sodium hydroxide
in methanol. Addition of an excess of aqueous NaOH solu-
tion to 1 in methanol afforded not the corresponding (2,2,2-
trifluoroethyl)diphenylphosphane oxide, but the (2,2-di-
Entry Aldehyde
Product Yield (%)[a] E/Z[b]
methoxyvinyl)triphenylphosphonium triflate (6a) in 95%
yield.[10] This finding suggested that the hydroxide or me-
thoxide did not directly attack the phosphorus atom, but
abstracted the acidic α proton of 1. Similar reactions were
also observed in alcohols other than methanol, the product
yields depending on the alcohols used. These results are
shown in Table 2. Ordinary primary aliphatic alcohols gave
the (2,2-dialkoxyvinyl)triphenylphosphonium triflates in
good yields, but the more acidic 2,2,2-trifluoroethanol gave
no corresponding phosphonium salt. The reaction in ethyl-
ene glycol, containing a dihydroxy moiety, gave a decreased
product yield, while the reaction in bulkier secondary and
1
2
3
4
5
6
7
8
9
4-CF3-C6H4CHO
2a
2b
2c
2d
2e
2f
76
86
74
64
90
85
16
8
41:59
39:61
40:60
25:75
39:61
32:68
58:42
55:45
Ϫ
4-CN-C6H4CHO
4-Cl-C6H4CHO
2-Cl-C6H4CHO
4-NO2-C6H4CHO
2-PyCHO[c]
C6H5CHO
4-MeO-C6H4CHO
C6H5CH2CH2CHO
2g
2h
Ϫ
0
[a]
Isolated yield. [b] Determined by capillary GC-MS analysis. [c] 2-
Pyridinecarboxyaldehyde.
4280
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(2,2,2-Trifluoroethyl)triphenylphosphonium Trifluoromethanesulfonate
FULL PAPER
Scheme 3. Plausible reaction mechanism for the formation of 6
tertiary alcohols gave only triphenylphosphane oxide. On flected in single or double addition to fluorinated olefins.
the basis of these observations, we considered that good The reaction between 1 and diisopropylamine in 1,1,2,2-
nucleophilicity is essential to the preparation of the (2,2- tetrachloroethane thus proceeded smoothly, exclusively af-
dialkoxyvinyl)triphenylphosphonium triflates.
fording the corresponding (Z)-(2-fluoro-2-diisopropylami-
novinyl)triphenylphosphonium triflate (10a) in high yield.
The geometric isomer was characterized by its 1H NMR
spectrum. As the coupling constant between fluorine and
vinyl proton has a value of 42 Hz, we assigned the Z form
to the isomer. The reason for the exclusive formation of the
Z isomer could be attributed to the contribution of the
stable conformer (13) prior to the elimination reaction (Fig-
ure 1).
Table 2. Preparation of 2,2-dialkoxyvinyl phosphonium salts
[a]
[b]
Isolated yield. Triphenylphosphane oxide was obtained.
Although the detailed reaction path was not clear, we
propose the path shown in Scheme 3. As discussed above,
the generated salt 5 was attacked by alkoxide to give the
new ylide 7 or phosphorane 8. Subsequently, a second elim-
ination of fluoride ion gave the (2-alkoxy-2-fluorovinyl)tri-
phenylphosphonium triflates (9). Repetition of the same
process afforded the (2,2-dialkoxyvinyl)triphenylphosphon-
ium triflate (6). In consideration of this pathway, we in-
ferred that 5 should be isolable from the reaction between
1 and an equal amount of methoxide. However, treatment
of 1 with an equal amount of sodium hydroxide (1  so-
dium hydroxide solution in methanol) gave three com-
pounds: 1, 6, and 9, assigned by their 1H NMR spectra. On
the basis of these results, we assumed that attack of the
methoxide on 5 is faster than abstraction of the α-proton
on 1.
Figure 1. Newman projection of 13
The reactions between the secondary cyclic alkylamine or
the secondary alkyl-arylamines and 1 also worked well to
give the corresponding products 10b؊10f in good yields
(Table 3). In the case of piperidine (entry 4 in Table 3), the
products consisted of the desired fluorinated vinylphos-
phonium salt 10d and its hydrolyzed product. Since these
two products could not be separated, we isolated them as
an amide derivative after subjection to acidic hydrolysis
conditions. In further exploration of the scope of this reac-
tion with respect to the primary amine and tertiary amines,
we obtained a complex mixture containing none of the de-
sired product in the former case, and the triphenylphos-
4. Treatment of 1 with Secondary Amines
We next considered that the difference in the nucleophil- phane oxide in the latter. We have formulated a plausible
icity between the alkoxides and the amines might be re- reaction mechanism, shown in Scheme 4.
Eur. J. Org. Chem. 2003, 4279Ϫ4285
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T. Hanamoto, N. Morita, K. Shindo
FULL PAPER
Table 3. Preparation of (Z)-2-amino-2-fluorovinyl phosphonium
salts
Table 4. Hydrolysis of (Z)-2-amino-2-fluorovinyl phosphonium
salts
[a]
[b]
Isolated yield. The overall yield from 1. See text.
Conclusion
We have developed a new and facile synthetic route to
the preparation of (2,2,2-trifluoroethyl)triphenylphosphon-
ium triflate (1), which should be utilizable for the prep-
aration of various 3,3,3-trifluoropropenyl compounds. We
have also demonstrated the different reactivity of 1 toward
alkoxides and amines.
[a]
[b]
Isolated yield.
The product 10d was contaminated with the
corresponding amide 14d. These two compounds could not be
separated. See text. Triphenylphosphane oxide was obtained.
[c]
As mentioned above, we noticed that the fluorinated vi-
nylphosphonium salts 10 are easily susceptible to acidic hy-
drolysis reactions because of the favorable release of the
fluorine atom. Thus, after the CDCl3 solution containing
10 had stood at room temperature for several hours, the
solvent was removed to afford the corresponding (2-car-
bamoylmethyl)triphenylphosphonium triflate (14) in good
yields.[11] We considered that a trace amount of DCl (or
HCl) and H2O in the CDCl3 solution caused this trans-
formation. These results are shown in Table 4.
Experimental Section
General: Melting point: Yanako micro melting point apparatus
MP-S3. NMR: JEOL JNM-GX 270 and AL-300. Chemical shifts
were reported as δ values (ppm) relative to internal tetramethylsil-
ane (1H) or (trifluoromethyl)benzene (19F) in CDCl3 unless other-
wise noted. GC-MS: JEOL JMS-AMII15 mass spectrometer.
HRMS and FAB-MS: JEOL JMS-HA100A mass spectrometer at
the Institute for Fundamental Research in Organic Chemistry,
Scheme 4. Plausible reaction mechanism for the formation of 10
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(2,2,2-Trifluoroethyl)triphenylphosphonium Trifluoromethanesulfonate
FULL PAPER
Kyushu University. IR: PerkinϪElmer SPECTRUM 2000 FT-IR.
Elemental analysis: the Service Center for Elemental Analysis of
Organic Compounds affiliated to the Faculty of Science, Kyushu
University. Analytical thin-layer chromatography (TLC) and col-
umn chromatography were performed on silica gel 60 F254 (Merck)
and silica gel 60 (40Ϫ63 µm), respectively. Toluene, 1,1,2,2-tetra-
chloroethane, and DMF were used after distillation from CaH2.
8.8 Hz, 1 H), 6.96 (d, J ϭ 12.7 Hz, 1 H), 7.47 (d, J ϭ 8.3 Hz, 2 H),
7.67 (d, J ϭ 8.3 Hz, 2 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ59.0
(3 F, d, J ϭ 8.8 Hz) ppm. IR (neat): ν˜ ϭ 3059, 2232, 1659, 1608,
1508, 1405, 1278, 1225, 1189, 1172, 1130, 1021, 883, 837, 753 cmϪ1
.
GC-MS: m/z ϭ 197 (100) [Mϩ], 196 (23), 176 (20), 147 (74), 128
(53), 127 (32), 101 (25), 75 (34), 51 (23). C10H6F3N (197.16): calcd.
C 60.92, H 3.07, N 7.10; found C 61.07, H 3.12, N 7.29.
(2,2,2-Trifluoroethyl)triphenylphosphonium Triflate (1):[3a] Tri-
phenylphosphane (3.19 g, 12.1 mmol) was added at room tempera-
ture under an argon atmosphere to a solution of 2,2,2-trifluoroe-
(E)- and (Z)-1-(4-Chlorophenyl)-3,3,3-trifluoro-1-propene (2c): Yield
74%. E/Z mixture: Rf ϭ 0.68, 0.54; hexane/ethyl acetate (20:1), col-
orless oil. H NMR (270 MHz): δ ϭ 5.79 (dq, J ϭ 12.5, 8.8 Hz, 1
1
thyl triflate (1.88 g, 8.11 mmol) in dry toluene (10 mL). The mix- H), 6.18 (dq, J ϭ 16.1, 6.3 Hz, 1 H), 6.88 (d, J ϭ 12.5 Hz, 1 H),
ture was heated at 100 °C for 2 days. The precipitate was collected, 7.11 (dq, J ϭ 16.1, 2.4 Hz, 1 H), 7.34 (s, 4 H), 7.38 (s, 4 H) ppm.
washed with diethyl ether, and dried in vacuo. The solid was pure
enough for microanalysis. Yield 3.39 g (85%). M.p. 205.7Ϫ206.6
°C. 1H NMR (270 MHz): δ ϭ 4.83 (dq, J ϭ 13.7, 9.8 Hz, 2 H),
19F NMR (283 MHz): δ ϭ Ϫ58.9 (3 F, d, J ϭ 8.8 Hz), Ϫ64.7 (3 F,
ddd, J ϭ 6.3, 2.4, 1.2 Hz) ppm. IR (neat): ν˜ ϭ 1666, 1597, 1494,
1410, 1332, 1316, 1276, 1225, 1180, 1130, 1015, 973, 877, 831, 809
7.69Ϫ7.86 (m, 15 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ54.7 (3 F, cmϪ1. GC-MS: E isomer m/z ϭ 206 (80) [Mϩ], 171 (32), 151 (100),
dt, J ϭ 7.9, 9.8 Hz), Ϫ79.7 (3 F, s) ppm. IR (KBr): ν˜ ϭ 2957, 2917,
102 (34), 101 (43), 75 (39). Z isomer m/z ϭ 206 (72) [Mϩ], 171 (31),
1589, 1440, 1333, 1290, 1242, 1150, 1130, 1091, 1033, 998, 753,
151 (100), 102 (34), 101 (43), 75 (41). C9H6ClF3 (206.59): calcd. C
722, 689 cmϪ1. FABMS: m/z ϭ 345 [Mϩ Ϫ OTfϪ]. C21H17F6O3PS 52.32, H 2.93; found C 52.71, H 3.03.
(494.39): calcd. C 51.01, H 3.47; found C 51.14, H 3.47.
(E)- and (Z)-1-(2-Chlorophenyl)-3,3,3-trifluoro-1-propene (2d): Yield
Wittig Reactions between 1 and Aldehydes. General Procedure
(Table 1). (E)- and (Z)-3,3,3-Trifluoro-1-[4-(trifluoromethyl)phenyl]-
1-propene (2a) (Table 1, entry 1): CsF (116 mg, 0.76 mmol) was ad-
64%. E/Z mixture: Rf ϭ 0.54, 0.69; hexane/ethyl acetate (20:1), col-
orless oil. H NMR (270 MHz): δ ϭ 5.90 (dq, J ϭ 12.7, 8.8 Hz, 1
1
H), 6.21 (dq, J ϭ 16.1, 6.3 Hz, 1 H), 7.07 (d, J ϭ 12.7 Hz, 1 H),
ded at room temperature to a solution of 1 (162 mg, 0.33 mmol) 7.23Ϫ7.61 (m, 9 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ59.2 (3 F,
and 4-(trifluoromethyl)benzaldehyde (49 µL, 0.36 mmol) in dry
d, J ϭ 8.8 Hz), Ϫ64.9 (3 F, dd, J ϭ 6.3, 2.2 Hz) ppm. IR (neat):
ν˜ ϭ 1664, 1476, 1439, 1412, 1315, 1275, 1220, 1188, 1130, 1054,
DMF (3 mL). After stirring for 8 h, the solution was quenched
with H2O. The mixture was extracted twice with hexane/diethyl 1037, 970, 771, 747 cmϪ1. GC-MS: E isomer m/z ϭ 206 (82) [Mϩ],
ether (3:1), and the combined organic layer was dried over Na2SO4.
The solution was concentrated in vacuo and the residue was puri-
fied by silica gel column chromatography (pentane) to give 2a
(60.1 mg) as a colorless oil.
171 (52), 151 (100), 102 (42), 101 (57), 75 (58), 51 (30). Z isomer
m/z ϭ 206 (78) [Mϩ], 171 (51), 151 (100), 102 (35), 101 (49), 75
(41). C9H6ClF3 (206.59): calcd. C 52.32, H 2.93; found C 52.64,
H 3.03.
(E)- and (Z)-3,3,3-Trifluoro-1-[4-(trifluoromethyl)phenyl]-1-propene (E)- and (Z)-3,3,3-Trifluoro-1-(4-nitrophenyl)-1-propene (2e): Yield
(2a): Yield 76%. E isomer: Rf ϭ 0.68; hexane/ethyl acetate (20:1);
90%. E isomer: Rf ϭ 0.74; hexane/ethyl acetate (3:1), yellow solid.
M.p. 84.0Ϫ85.8 °C. H NMR (270 MHz): δ ϭ 6.37 (dq, J ϭ 16.1,
1
colorless oil. 1H NMR (270 MHz): δ ϭ 6.29 (dq, J ϭ 16.1, 6.3 Hz,
1 H), 7.19 (dq, J ϭ 16.1, 2.0 Hz, 1 H), 7.57 (d, J ϭ 8.3 Hz, 2 H), 6.3 Hz, 1 H), 7.23 (dq, J ϭ 16.1, 2.4 Hz, 1 H), 7.63 (d, J ϭ 8.8 Hz,
7.66 (d, J ϭ 8.3 Hz, 2 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ64.2 2 H), 8.27 (d, J ϭ 8.8 Hz, 2 H) ppm. 19F NMR (283 MHz): δ ϭ
(3 F, s), Ϫ65.0 (3 F, dt, J ϭ 6.3, 2.0 Hz) ppm. IR (neat): ν˜ ϭ 1669,
Ϫ65.3 (3 F, dd, J ϭ 6.3, 2.4 Hz) ppm. IR (neat): ν˜ ϭ 1668, 1652,
1621, 1584, 1420, 1327, 1316, 1286, 1210, 1172, 1127, 1109, 1068,
1601, 1568, 1557, 1539, 1505, 1417, 1090, 958, 868, 822, 747, 687
1018, 974, 860, 840, 819, 690 cmϪ1. GC-MS: m/z ϭ 240 (23) [Mϩ], cmϪ1. GC-MS: m/z ϭ 217 (18) [Mϩ], 151 (100), 109 (44), 102 (32),
171 (53), 151 (100), 150 (12), 75 (11), 69 (11). C10H6F6 (240.04): 101 (23), 75 (20), 51 (20). HRMS: C9H6F3NO2: calcd. 217.0351;
calcd. C 50.02, H 2.52; found C 50.31, H 2.67. Z isomer: Rf ϭ
found 217.0361. Z isomer: Rf ϭ 0.56; hexane/ethyl acetate (3:1),
0.49; hexane/ethyl acetate(20:1), colorless oil. 1H NMR (270 MHz):
colorless oil. 1H NMR (270 MHz): δ ϭ 5.98 (dq, J ϭ 12.7, 8.8 Hz,
δ ϭ 5.90 (dq, J ϭ 12.7, 8.8 Hz, 1 H), 6.98 (d, J ϭ 12.7 Hz, 1 H), 1 H), 7.02 (d, J ϭ 12.7 Hz, 1 H), 7.53 (d, J ϭ 8.8 Hz, 2 H), 8.24
7.49 (d, J ϭ 8.3 Hz, 2 H), 7.64 (d, J ϭ 8.3 Hz, 2 H) ppm. 19F NMR (d, J ϭ 8.8 Hz, 2 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ59.0 (3 F,
(283 MHz): δ ϭ Ϫ58.9 (3 F, d, J ϭ 8.8 Hz), Ϫ64.1 (3 F, s) ppm. d, J ϭ 8.8 Hz) ppm. IR (neat): ν˜ ϭ 3083, 2859, 1661, 1601, 1524,
IR (neat): ν˜ ϭ 1661, 1621, 1407, 1329, 1282, 1227, 1180, 1129, 1497, 1423, 1403, 1348, 1313, 1281, 1227, 1180, 1129, 1016, 976,
1068, 1019, 883, 839, 731 cmϪ1. GC-MS: m/z ϭ 240 (23) [Mϩ], 171 888, 857, 783, 766, 747, 726, 688 cmϪ1. GC-MS: m/z ϭ 217 (19)
(53), 151 (100), 150 (12), 75 (11), 69 (11). HRMS (C10H6F6): calcd.
240.0373; found 240.0360.
[Mϩ], 151 (100), 109 (42), 102 (21), 101 (21), 75 (21), 51 (17).
HRMS (C9H6F3NO2): calcd. 217.0351; found 217.0347. C9H6ClF3
(217.15): calcd. C 49.78, H 2.78, N 6.45; found C 50.05, H 2.88,
N 6.65.
(E)- and (Z)-1-(4-Cyanophenyl)-3,3,3-trifluoro-1-propene (2b): Yield
86%. E isomer: Rf ϭ 0.70; hexane/ethyl acetate (4:1), white solid.
1
M.p. 45.2Ϫ46.2 °C. H NMR (270 MHz): δ ϭ 6.31 (dq, J ϭ 16.1,
(E)-and (Z)-3,3,3-Trifluoro-1-(2-pyridyl)-1-propene (2f): Yield 85%.
6.3 Hz, 1 H), 7.17 (dq, J ϭ 16.1, 2.4 Hz, 1 H), 7.56 (d, J ϭ 8.3 Hz, E isomer: Rf ϭ 0.61; hexane/ethyl acetate (3:1), colorless oil. 1H
2 H), 7.70 (d, J ϭ 8.3 Hz, 2 H) ppm. 19F NMR (283 MHz): δ ϭ NMR (270 MHz): δ ϭ 6.82 (dq, J ϭ 15.6, 6.8 Hz, 1 H), 7.18 (dq,
Ϫ65.2 (3 F, dd, J ϭ 6.3, 2.4 Hz) ppm. IR (neat): ν˜ ϭ 3066, 2228, J ϭ 15.6, 2.0 Hz, 1 H), 7.29 (ddd, J ϭ 7.8, 4.9, 1.0 Hz, 1 H), 7.35
1668, 1609, 1564, 1510, 1416, 1339, 1317, 1279, 1210, 1115, 980,
(d, J ϭ 7.8 Hz, 1 H), 7.73 (dt, J ϭ 2.0, 7.8 Hz, 1 H), 8.61Ϫ8.67
879, 840, 815, 660 cmϪ1. GC-MS: m/z ϭ 197 (100) [Mϩ], 196 (24), (m, 1 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ65.1 (3 F, dd, J ϭ 6.8,
176 (21), 147 (72), 128 (58), 127 (37), 101 (28), 75 (37), 51 (25), 50 2.0 Hz) ppm. IR (neat): ν˜ ϭ 2928, 1672, 1590, 1471, 1435, 1334,
(22). C10H6F3N (197.16): calcd. C 60.92, H 3.07, N 7.10; found C
1307, 1267, 1204, 1124, 1092, 994, 973, 879, 846, 767, 742, 694
61.26, H 3.16, N 7.06. Z isomer: Rf ϭ 0.53; hexane/ethyl acetate cmϪ1. GC-MS: m/z ϭ 173 (25) [Mϩ], 104 (100), 79 (20), 51 (21). Z
1
(4:1), colorless oil. H NMR (270 MHz): δ ϭ 5.93 (dq, J ϭ 12.7,
isomer: Rf ϭ 0.39; hexane/ethyl acetate (3:1), colorless oil. 1H
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T. Hanamoto, N. Morita, K. Shindo
FULL PAPER
NMR (270 MHz): δ ϭ 5.96 (dq, J ϭ 12.9, 8.8 Hz, 1 H), 7.02 (d, column chromatography (CH2Cl2, then CH2Cl2/acetone, 3:1) to
J ϭ 12.9 Hz, 1 H), 7.26 (ddd, J ϭ 7.8, 4.9, 1.0 Hz, 1 H), 7.50 (d, give 10a (101 mg) as a solid.
J ϭ 7.8 Hz, 1 H), 7.72 (dt, J ϭ 2.0, 7.8 Hz, 1 H), 8.62Ϫ8.69 (m, 1
H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ59.2 (3 F, d, J ϭ 8.8 Hz)
ppm. IR (neat): ν˜ ϭ 1662, 1588, 1569, 1470, 1438, 1411, 1281, 1220,
1196, 1127, 1093, 994, 874, 803, 746 cmϪ1. GC-MS: m/z ϭ 173
(20) [Mϩ], 104 (100), 78 (21), 51 (22). HRMS (C9H6F3NO2): calcd.
173.0452; found 173.0459.
(Z)-(2-Fluoro-2-diisopropylaminovinyl)triphenylphosphonium
Tri-
flate (10a): Yield 90%, white solid. M.p. 128.5Ϫ129.2 °C. 1H NMR
(270 MHz): δ ϭ 1.309 (d, J ϭ 6.8 Hz, 6 H), 1.313 (d, J ϭ 6.8 Hz,
6 H), 3.90Ϫ4.10 (m, 2 H), 4.35 (dd, J ϭ 43.0, 8.8 Hz, 1 H),
7.58Ϫ7.76 (m, 15 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ60.0 (1 F,
br. d, J ϭ 43.0 Hz), Ϫ79.4 (3 F, s) ppm. IR (KBr): ν˜ ϭ 3094, 3058,
2986, 2940, 2880, 1600, 1575, 1440, 1266, 1150, 1107, 899, 846,
749, 717, 693 cmϪ1. C27H30F4NO3PS (555.56): calcd. C 58.37, H
5.44, N 2.52; found C 58.77, H 5.42, N 2.40.
Preparation of (2,2-Dialkoxyvinyl)triphenylphosphonium Triflate.
General Procedure (Table 2). (2,2-Dimethoxyvinyl)triphenylphos-
phonium Triflate (6a): NaOH solution (1 , 10 mL) was added
slowly at 0 °C to a solution of 1 (101 mg, 0.2 mmol) in methanol
(2 mL). The mixture was stirred for 12 h at ambient temperature.
The organic layer was separated, and the remaining aqueous layer
was extracted with CH2Cl2 (5 mL ϫ 2). The combined organic
layer was dried over Na2SO4 and the solution was concentrated in
vacuo. The residue was purified by silica gel (containing 6% H2O)
column chromatography (CH2Cl2/acetone, 3:1) to give 6a as a
sticky oil. The oil was allowed to stand at room temperature to
form the corresponding solid.
(Z)-(2-Fluoro-2-molphorylaminovinyl)triphenylphosphonium Triflate
(10b): Yield 77%, white solid. M.p. 137.8Ϫ139.9 °C. 1H NMR
(270 MHz): δ ϭ 3.58 (t, J ϭ 5.4 Hz, 4 H), 3.81 (t, J ϭ 5.4 Hz, 4
H), 4.69 (dd, J ϭ 42.0, 7.3 Hz, 1 H), 7.61Ϫ7.77 (m, 15 H) ppm.
19F NMR (283 MHz) δ ϭ Ϫ70.0 (1 F, br. d, J ϭ 42.0 Hz), Ϫ79.5
(3 F, s) ppm. IR (KBr): ν˜ ϭ 3589, 3518, 3067, 2920, 2857, 1615,
1452, 1438, 1367, 1253, 1164, 1106, 1033, 878, 836, 756, 722, 692
cmϪ1. C25H24F4NO4PS (541.49): calcd. C 55.45, H 4.47, N 2.59;
found C 55.30, H 4.50, N 2.61.
(2,2-Dimethoxyvinyl)triphenylphosphonium Triflate (6a): Yield 95%,
1
white solid. M.p. 132.2Ϫ133.2 °C. H NMR (270 MHz): δ ϭ 3.52
(Z)-(2-Diethylamino-2-fluorovinyl)triphenylphosphonium
Triflate
(s, 3 H), 4.21 (s, 3 H), 4.41 (d, J ϭ 10.7 Hz, 1 H), 7.62Ϫ7.74 (m,
15 H) ppm. IR (KBr): ν˜ ϭ 3109, 3063, 1583, 1475, 1436, 1360,
1266, 1149, 1113, 1034, 928, 753, 724, 693 cmϪ1. C23H22F3O5PS
(498.44): calcd. C 55.42, H 4.45; found C 55.18, H 4.42.
(10c): Yield 88%, white solid. M.p. 114.2Ϫ115.8 °C. 1H NMR
(270 MHz): δ ϭ 1.27 (t, J ϭ 7.2 Hz, 6 H), 3.49 (q, J ϭ 7.2 Hz, 4
H), 4.13 (dd, J ϭ 42.0, 8.1 Hz, 1 H), 7.58Ϫ7.91 (m, 15 H) ppm.
19F NMR (283 MHz): δ ϭ Ϫ68.0 (1 F, dd, J ϭ 42.0, 8.3 Hz), Ϫ79.4
(3 F, s) ppm. IR (KBr): ν˜ ϭ 3072, 2984, 1615, 1574, 1480, 1440,
(2,2-Diethoxyvinyl)triphenylphosphonium Triflate (6b): Yield 88%.
1H NMR (300 MHz): δ ϭ 0.73 (t, J ϭ 7.2 Hz, 3 H), 1.48 (t, J ϭ 1258, 1109, 1032, 967, 856, 756, 719, 693 cmϪ1. C25H26F4NO3PS
7.2 Hz, 3 H), 4.00 (q, J ϭ 7.2 Hz, 2 H), 4.24 (dd, J ϭ 1.5, 11.4 Hz,
1 H), 4.46 (q, J ϭ 7.2 Hz, 2 H), 7.69Ϫ7.86 (m, 15 H) ppm. Since
this compound was not easily solidified, we attempted the following
procedure. The CH2Cl2 solution containing 6b was slowly added to
diethyl ether while being stirred vigorously. A precipitate generally
formed with progressing dropwise addition of the CH2Cl2 solution,
but we found that the generated solid was not 6b but the corre-
sponding hydrolysis product (6bЈ, see below).
(527.51): calcd. C 56.92, H 4.97, N 2.66; found C 56.92, H 5.00,
N 2.61.
4.5.4. (Z)-(2-Fluoro-2-N-methylanilinovinyl)triphenylphosphonium
Triflate (10e): Yield 93%, white solid. M.p. 159.5Ϫ161.2 °C. 1H
NMR (300 MHz): δ ϭ 3.56 (d, J ϭ 2.0 Hz, 3 H), 4.30 (dd, J ϭ
39.6, 7.8 Hz, 1 H), 7.31Ϫ7.46 (m, 5 H), 7.62Ϫ7.77 (m, 15 H) ppm.
19F NMR (283 MHz): δ ϭ Ϫ65.2 (1 F, br. d, J ϭ 39.6 Hz), Ϫ79.4
(3 F, s) ppm. IR (KBr): ν˜ ϭ 3060, 2291, 1816, 1634, 1615, 1590,
1574, 1557, 1494, 1464, 1394, 1316, 1265, 1222, 1185, 1153, 1110,
1027, 997, 977, 841, 777, 747, 723, 691 cmϪ1. C28H24F4NO3PS
(561.53): calcd. C 59.89, H 4.31, N 2.49; found C 59.88, H 4.35,
N 2.48.
(Ethoxycarbonylmethyl)triphenylphosphonium Triflate (6bЈ):[12]
1
White solid. M.p. 135.2Ϫ137.6 °C. H NMR (300 MHz): δ ϭ 1.09
(t, J ϭ 7.2 Hz, 3 H), 4.07 (q, J ϭ 7.2 Hz, 2 H), 4.83 (dd, J ϭ 13.6,
1.1 Hz, 2 H), 7.53Ϫ7.84 (m, 15 H) ppm. IR (KBr): ν˜ ϭ 3060, 2944,
2885, 1748, 1588, 1475, 1442, 1368, 1258, 1151, 1110, 1031, 756,
722, 692 cmϪ1. C23H22F3O5PS (498.44): calcd. C 55.42, H 4.45;
found C 55.47, H 4.23.
(Z)-(2-Fluoro-2-indolinylvinyl)triphenylphosphonium Triflate (10f):
Yield 70%, white solid. M.p. 151.0Ϫ152.0 °C. 1H NMR
(300 MHz): δ ϭ 3.36 (t, J ϭ 8.3 Hz, 2 H), 4.38 (t, J ϭ 8.3 Hz, 2
H), 4.76 (dd, J ϭ 40.7, 7.2 Hz, 1 H), 7.01Ϫ7.23 (m, 4 H), 7.47Ϫ7.78
(m, 15 H) ppm. 19F NMR (283 MHz): δ ϭ Ϫ71.5 (1 F, br. d, J ϭ
40.7 Hz), Ϫ79.5 (3 F, s) ppm. IR (KBr): ν˜ ϭ 3423, 3064, 2960,
2853, 1990, 1907, 1823, 1574, 1488, 1471, 1441, 1417, 1369, 1259,
([1,3]Dioxolan-2-ylidenemethyl)triphenylphosphonium Triflate (6c):
Yield 22%, white solid. M.p. 134.7Ϫ136.8 °C. 1H NMR
(300 MHz): δ ϭ 4.16 (d, J ϭ 10.3 Hz, 1 H), 4.60 (t, J ϭ 7.3 Hz, 2
H), 4.76 (t, J ϭ 7.3 Hz, 2 H), 7.54Ϫ7.79 (m, 15 H) ppm. IR (KBr):
ν˜ ϭ 3049, 2926, 1615, 1259, 1151, 1110, 1061, 911, 755, 734, 692
cmϪ1. C23H20F3O5PS (496.44): calcd. C 55.65, H 4.06; found C
55.50, H 4.05.
1224, 1189, 1147, 1109, 1032, 997, 844, 753, 722, 693, 669 cmϪ1
.
C29H24F4NO3PS (573.54): calcd. C 60.73, H 4.22, N 2.44; found C
60.82, H 4.23, N 2.40.
Preparation of (Z)-(2-Amino-2-fluorovinyl)triphenylphosphonium
Triflate. General Procedure (Table 3). (Z)-(2-Fluoro-2-diisopro-
Preparation of [(Carbamoyl)methyl]triphenylphosphonium Triflate ؊
pylaminovinyl)triphenylphosphonium Triflate (10a): Diisopropylam- General Procedure (Table 4). [(Diisopropylcarbamoyl)methyl]tri-
ine (43 µL, 0.31 mmol) was added slowly at room temperature to phenylphosphonium Triflate (14a): CDCl3 (500 µL) was added
a solution of 1 (100 mg, 0.20 mmol) in 1,1,2,2-tetrachloroethane
(3 mL). The mixture was stirred for 12 h at ambient temperature.
The organic layer was separated, and the remaining aqueous layer
slowly at room temperature to a solution of 10a (51.8 mg,
0.09 mmol) in CH2Cl2 (3 mL). The mixture was stirred for 12 h at
ambient temperature. After the solution had been concentrated in
was extracted with CH2Cl2 (5 mL ϫ 2). The combined organic vacuo, the residue was purified by silica gel (containing 6% H2O)
layer was dried over Na2SO4 and the solution was concentrated in column chromatography (CH2Cl2 then CH2Cl2/acetone, 3:1) to give
vacuo. The residue was purified by silica gel (containing 6% H2O) 14a (46.5 mg) as a white solid.
4284
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Eur. J. Org. Chem. 2003, 4279Ϫ4285

(2,2,2-Trifluoroethyl)triphenylphosphonium Trifluoromethanesulfonate
FULL PAPER
[(Diisopropylcarbamoyl)methyl]triphenylphosphonium Triflate (14a):
Yield 90%, white solid. M.p. 157.6Ϫ158.8 °C. 1H NMR
(300 MHz): δ ϭ 1.17 (d, J ϭ 6.8 Hz, 6 H), 1.26 (d, J ϭ 6.4 Hz, 6
H), 3.34Ϫ3.48 (m, 1 H), 4.32Ϫ4.41 (m, 1 H), 4.94 (d, J ϭ 13.0 Hz,
2 H), 7.58Ϫ7.79 (m, 15 H) ppm. IR (KBr): ν˜ ϭ 2937, 1634, 1440,
[1] [1a]
T. Hiyama, Organofluorine Compounds, Springer, Berlin,
2000.[1b] M. Hudlicky, A. E. Pavlath, Chemistry of Organic Flu-
orine Compounds II; ACS Monograph 187; Washington DC,
1995.
[2] [2a]
J. M. Percy, Top. Curr. Chem. 1997, 193, 131Ϫ195. [2b] D. J.
1374, 1344, 1261, 1225, 1156, 1112, 1031, 742, 721, 690 cmϪ1
.
Burton, Z. Y. Yang, W. Qiu, Chem. Rev. 1996, 96, 1641Ϫ1715.
C27H31F3NO4PS (553.58): calcd. C 58.58, H 5.64, N 2.53; found C
58.56, H 5.70, N 2.47.
[2c]
D. L. S. Brahms, W. P. Dailey, Chem. Rev. 1996, 96,
1585Ϫ1632. [2d] D. J. Burton, Z. Y. Yang, P. A. Morken, Tetra-
hedron 1994, 50, 2993Ϫ3063.
(2-Morpholino-2-oxoethyl)triphenylphosphonium Triflate (14b):
Yield 73%, white solid. M.p. 198.2Ϫ200.0 °C. 1H NMR
(300 MHz): δ ϭ 3.48 (t, J ϭ 4.2 Hz, 2 H), 3.61 (t, J ϭ 4.6 Hz, 2
H), 3.75Ϫ3.78 (4 H, br. s), 4.95 (d, J ϭ 13.2 Hz, 2 H), 7.62Ϫ7.80
(m, 15 H) ppm. IR (KBr): ν˜ ϭ 3440, 2935, 2892, 1645, 1441, 1388,
[3] [3a]
T. Umemoto, Y. Gotoh, Bull. Chem. Soc. Jpn. 1991, 64,
[3b]
2008Ϫ2010.
503Ϫ504.
R. A. Henry, J. Chem. Eng. Data 1976, 21,
[4] [4a]
T. Hanamoto, K. Nishiyama, H. Tateishi, M. Kondo, Syn-
[4b]
lett 2001, 1320Ϫ1322.
uoka, Y. Kiguchi, M. Kondo, J. Chem. Soc., Perkin Trans. 1
2000, 103Ϫ107.
T. Hanamoto, K. Shindo, M. Mats-
1259, 1224, 1154, 1115, 1070, 1030, 998, 869, 749, 718, 690 cmϪ1
.
[4c]
C25H25F3NO5PS (539.51): calcd. C 55.66, H 4.67, N 2.60; found C
55.44, H 4.74, N 2.50.
T. Hanamoto, Y. Kiguchi, K. Shindo, M.
Matsuoka, M. Kondo, Chem. Commun. 1999, 151Ϫ152.
In the course of our study, a similar Wittig olefination with
the aid of (2,2,2-trifluoroethyl)diphenylphosphane oxide was
independently reported: T. Kobayashi, T. Eda, O. Tamura, H.
Ishibashi, J. Org. Chem. 2002, 67, 3156Ϫ3159.
J. Ichikawa, H. Jyono, S. Yonemaru, T. Okauchi, T. Minami,
J. Fluorine Chem. 1999, 97, 109Ϫ114.
N. Ishikawa, T. Yokozawa, Bull. Chem. Soc. Jpn. 1983, 56,
724Ϫ726.
Use of TBAF in place of CsF was not effective for this Wit-
tig reaction.
[5]
(Diethylcarbamoylmethyl)triphenylphosphonium Triflate (14c):
Yield 84%, white solid. M.p. 159.8Ϫ162.1 °C. 1H NMR
(300 MHz): δ ϭ 1.00 (t, J ϭ 7.2 Hz, 3 H), 1.23 (t, J ϭ 7.2 Hz, 3
H), 3.28 (q, J ϭ 7.2 Hz, 2 H), 3.63 (q, J ϭ 7.2 Hz, 2 H), 4.89 (d,
J ϭ 13.2 Hz, 2 H), 7.61Ϫ7.80 (m, 15 H) ppm. IR (KBr): ν˜ ϭ 2977,
2926, 2891, 1633, 1469, 1436, 1393, 1259, 1161, 1111, 1029, 997,
957, 914, 872, 751, 717, 691 cmϪ1. C25H27F3NO4PS (525.52): calcd.
C 57.14, H 5.18, N 2.67; found C 57.23, H 5.12, N 2.67.
[6]
[7]
[8]
[9]
(2-Oxo-2-piperidine-1-yl-ethyl)triphenylphosphonium Triflate (14d):
Yield 88%, white solid. M.p. 166.2Ϫ167.2 °C. 1H NMR
(300 MHz): δ ϭ 1.47Ϫ1.50 (m, 2 H), 1.60Ϫ1.68 (m, 4 H), 3.42 (t,
J ϭ 5.7 Hz, 2 H), 3.68 (t, J ϭ 5.7 Hz, 2 H), 4.92 (d, J ϭ 13.0 Hz,
2 H), 7.60Ϫ7.80 (m, 15 H) ppm. IR (KBr): ν˜ ϭ 3855, 3448, 2928,
A facile synthesis of a trans-#?#-(trifluoromethyl)styrene de-
rivative has been reported: T. Fuchikami, M. Yatabe, I. Ojima,
Synthesis 1981, 365Ϫ366. See also: S. Furuta, M. Kuroboshi,
M. T. Hiyama, Bull. Chem. Soc. Jpn. 1999, 72, 805Ϫ819.
(2,2-Diethoxyvinyl)triphenylphosphonium tetrafluoroborate,
as a similar salt, has been prepared from the corresponding
[(ethoxycarbonyl)methylidene]triphenylphosphorane and tri-
ethyloxonium tetrafluoroborate: H. J. Bestmann, R. Saalfrank,
J. P. Snyder, Angew. Chem. Int. Ed. Eng. 1969, 8, 216Ϫ217.
[(Diisopropylcarbamoyl)methyl]triphenylphosphonium
mide has been reported: H. J. Bestmann, L. Kisielowski, Chem.
Ber. 1983, 116, 1320Ϫ1326.
[(Ethoxycarbonyl)methyl]triphenylphosphonium chloride, as a
similar salt, has been prepared from the corresponding ethyl
chloroacetate and triphenylphosphane: W. J. Considine, J. Org.
Chem. 1962, 27, 647Ϫ649.
[10]
1634, 1437, 1393, 1259, 1159, 1031, 870, 752, 717, 691 cmϪ1
.
C26H27F3NO4PS (537.53): calcd. C 58.10, H 5.06, N 2.61; found C
57.88, H 4.99, N 2.56.
[11]
[12]
bro-
Acknowledgments
We are grateful to Professors Hiroyuki Ishibashi and Osamu
Tamura at Kanazawa University for their valuable discussions and
comments. We also thank Central Glass Co., Ltd., for a gift of
2,2,2-trifluoroethyl triflate and Chemetall Japan Co., Ltd., for a
gift of CsF.
Received June 27, 2003
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