Ring-closing metathesis of vinyl fluorides towards α-fluorinated α,β-unsaturated lactams and lactones

Article abstract of DOI:10.1002/ejoc.201402535

Ring-closing olefin metathesis reactions (RCM) using Grubbs II or Hoveyda's catalysts have been applied to a series of N-alkenyl-N-benzyl-α-fluoroacrylamides. α-Fluoro-α,β-unsaturated γ- or δ-lactams incorporating a fluorinated double bond were obtained in moderate to good yields, depending on the nature of substituents on the benzyl ring. The corresponding seven- and eight-membered lactams were not formed under similar conditions. When the N-benzyl group was replaced by an N-tosyl group, the corresponding ε-lactam was also formed in 38% yield. When N-(2-fluoroallyl) derivatives were used instead of fluoroacryloyl derivatives, six-, seven-, and eight-membered N-heterocycles were obtained in low yields. This method was also used to synthesize fluorinated α,β-unsaturated analogues of pyrrolizidine and indolizidine alkaloids from prolinol, and also to synthesize N-benzyl-3-fluoroquinolone in three steps from commercially available 2-vinylaniline in 44% overall yield. Also 3-fluorocoumarin and 3-fluorochromene were prepared from ovinylphenol, and 3-fluoro-benzoxepine was available from o-allylphenol.

Full text of DOI:10.1002/ejoc.201402535

FULL PAPER
DOI: 10.1002/ejoc.201402535
Ring-Closing Metathesis of Vinyl Fluorides towards α-Fluorinated
α,β-Unsaturated Lactams and Lactones
Michael Marhold,[a] Christian Stillig,[a] Roland Fröhlich,[a] and Günter Haufe*[a]
Keywords: Homogeneous catalysis / Cyclization / Metathesis / Fluorine / Lactams / Lactones / Nitrogen heterocycles
Ring-closing olefin metathesis reactions (RCM) using
Grubbs II or Hoveyda’s catalysts have been applied to a
series of N-alkenyl-N-benzyl-α-fluoroacrylamides. α-Fluoro-
α,β-unsaturated γ- or δ-lactams incorporating a fluorinated
double bond were obtained in moderate to good yields, de-
pending on the nature of substituents on the benzyl ring. The
corresponding seven- and eight-membered lactams were not
formed under similar conditions. When the N-benzyl group
was replaced by an N-tosyl group, the corresponding ε-
lactam was also formed in 38% yield. When N-(2-fluoroallyl)
derivatives were used instead of fluoroacryloyl derivatives,
six-, seven-, and eight-membered N-heterocycles were ob-
tained in low yields. This method was also used to synthesize
fluorinated α,β-unsaturated analogues of pyrrolizidine and
indolizidine alkaloids from prolinol, and also to synthesize N-
benzyl-3-fluoroquinolone in three steps from commercially
available 2-vinylaniline in 44% overall yield. Also 3-fluoro-
coumarin and 3-fluorochromene were prepared from o-
vinylphenol, and 3-fluoro-benzoxepine was available from
o-allylphenol.
Introduction
Since the development of well-defined active catalysts by
Schrock and Grubbs in the 1990s, olefin metathesis took a
giant leap forward to become one of the most important
tools for C–C bond formation.[1] This reaction has been
applied successfully to a wide variety of substrates,[2] which
shows its huge versatility and benefit. The importance of
this new tool for synthetic chemistry was acknowledged by
the Nobel Prize committee in 2005, when Chauvin, Grubbs,
and Schrock were rewarded for the discovery and mechan-
istic investigations of the method.[3]
The reaction is widely adaptable for fluorine-free com-
pounds, and there are also many examples of the synthesis
of unsaturated carbocycles and heterocycles bearing fluor-
ine substituents away from the double bonds.[4] In contrast,
to date, there are only few reports of metathesis reactions
involving a fluorinated double bond. A couple of years ago,
we reported preliminary results on the ring-closing metathe-
sis (RCM) reactions of N-benzyl-protected N-alkenyl-N-
fluoroacrylamides 1 to give α,β-unsaturated N-benzyllact-
ams 2 bearing a fluorine in the α position (Scheme 1).[5]
Independently, and almost simultaneously, Brown et al.[6]
and Rutjes et al.[7] published similar examples of ring-clos-
ing metathesis with vinyl fluorides.
Scheme 1. Synthesis of substituted N-benzyl α,β-unsaturated α-
fluoro γ- and δ-lactams 2 starting from benzylamines 3 via second-
ary amines 4 and acrylamides 1. EDC = N-1-ethyl-NЈ-(3-dimethyl-
aminopropyl)carbodiimide hydrochloride; HOBt = 1-hydroxy-1H-
benzotriazole.
In this study, we have extended the scope of this reaction
and, we have used Grubbs II catalyst (A) and Hoveyda’s
catalyst (B) (Figure 1) to synthesize fluorinated analogues
of natural N- and O-heterocyclic compounds.
[a] Organisch-Chemisches Institut, Westfälische Wilhelms-
Universität Münster,
Corrensstr. 40, 48149 Münster, Germany
E-mail: haufe@uni-muenster.de
http://www.uni-muenster.de/Chemie.oc/haufe/haufe.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201402535.
Figure 1. Grubbs II (A) and Hoveyda’s (B) catalysts.
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M. Marhold, C. Stillig, R. Fröhlich, G. Haufe
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1q (Table 1, entries 3, 4, and 17). Similar non-fluorinated
medium-sized rings have been obtained in reasonable
yields.[9]
The structures of compounds 2i and 2p were proved by
X-ray diffraction (Figure 2).
Results and Discussion
Unsaturated Fluorinated N-Benzyl Lactams by RCM of
N-Alkenyl-N-benzyl-2-fluoroacrylamides
First, we prepared substituted N-alkenyl-N-benzyl-N-(2-
fluoroacryl)amides 1 as RCM precursors from the corre-
sponding benzylamines (i.e., 3) and ω-haloalkenes via 4.
Then, various substituted N-benzyl-substituted α,β-unsatu-
rated α-fluoro-γ-lactams 2 were synthesized using 2–4 mol-
% of the highly active[8] Grubbs II catalyst (A), as shown in
Figure 1, Scheme 1, and Table 1.
Table 1. Synthesized fluorinated α,β-unsaturated N-benzyl γ- and
δ-lactams 2.
Entry
R1 R2
R3
R4
n
Products Yield of Yield
1 [%] of 2 [%]
1
2
3
4
5
6
7
8
H
H
H
H
H
H
H
Cl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
H
F
H
H
CF3
H
H
H
H
H
H
H
H
Cl
H
H
F
F
H
CF3
NO2
H
tBu
OMe
OMe
OMe
H
H
H
H
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1
2
3
4
1
1
1
1
1
2
1
1
1
1
1
2
3
1
0
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
70[a]
48[a]
52[a]
52[a]
41[a]
30
79[a]
86[a]
0[a,b]
0[a,c]
46[a]
73
40
43
65
76
9
66
70
10
11
12
13
14
15
16
17
18
19
57[a]
40
76[a]
77
44
46
55
44
33
77
93[d]
73[a]
80
86
81[a]
0
Figure 2. X-ray crystal structures of compounds 2i and 2p.
OMe H
H
42
78
34
0
In 2003, Osipov and Dixneuf synthesized a wide variety
of non-fluorinated lactams and other N-heterocycles with
different substituents on nitrogen using RCM.[10] Hoveyda
et al. assembled five- to eight-membered N-tosyl heterocy-
cles in good to excellent yields using one of his catalysts.[11]
With their work as a basis, we went on to investigate the
synthesis of fluorinated analogues of five- to eight-mem-
bered N-tosyl heterocycles using RCM. The synthetic path-
way is shown in Scheme 2, the yields are given in Table 2
and the X-ray structure of compound 7c is shown in Fig-
ure 3. Similar compounds have recently been made by ring-
closing metathesis by Rutjes et al.[7]
OMe OMe
s
[a] Ref.[5] [b] The “homodimer” incorporating non-fluorinated
double bonds was isolated (40%). [c] The “homodimer” incorpo-
rating non-fluorinated double bonds was identified by HRMS, but
was not isolated. [d] Crude product.
RCM reactions leading to γ- and δ-lactams generally
gave yields ranging from 65 to 77%. Attempted cyclization
reactions to form seven- or eight-membered lactams
(Table 1, entries 3, 4, and 17) failed. Electron-donating sub-
stituents like tert-butyl (Table 1, entry 15) or para-methoxy
(Table 1, entry 16) groups increased the yield to 81 or 86%,
while substrates with electron-deficient substituents like tri-
fluoromethyl (Table 1, entry 12) or nitro (Table 1, entry 13)
groups in the para position gave significantly lower yields
of 44 or 33%, respectively. Surprisingly, the RCM reaction
of a meta-trifluoromethyl-substituted precursor (Table 1,
entry 14) performed well to give a 77% yield, while a sub-
strate with methoxy substituents in both the ortho and para
positions (Table 1, entry 18) gave a dramatically reduced
yield of 34%, and compound 1s, with methoxy groups in
the meta and para positions (Table 1, entry 19), did not give
any RCM product.
Scheme 2. RCM of monofluorinated N-tosyl-substituted aza-α,ω-
diene systems.
Starting from N-alkenyl-N-tosylamides 5, the corre-
The results also show that six-membered rings were sponding N-alkenyl-N-(2-fluoroacryl)-N-tosylamides (i.e.,
formed in slightly higher yields (Table 1, entries 2, 10, and 6a–6d) or N-alkenyl-N-(2-fluoroallyl)-N-tosylamides (i.e.,
16) than their five-membered analogues (Table 1, entries 1 7a–7d) were synthesized (Table 2). These compounds were
and 9), and that cyclization to seven- and eight-membered then used for RCM reactions. For acrylamides 6, Grubbs II
rings did not work at all, even with p-methoxy precursor catalyst (A) was useful. It gave γ- and δ-lactams 8a and 8b
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Ring-Closing Metathesis of Vinyl Fluorides
Table 2. Synthesis from 6 or 7 of fluorinated α,β-unsaturated N-tosyl γ- and δ-lactams 8, and fluorinated N-tosyl heterocycles 9.
Entry
Z
n
Products
Yield of 6/7 [%]
Catalyst (mol-%)
Yield of 8/9 [%]
Homodimer [%]
1
2
3
4
5
6
7
8
O
O
O
O
H2
H2
H2
H2
0
1
2
3
0
1
2
3
a
b
c
68
85
59
83
92
70
74
74
A (4)
A (2)
A (2)
A (2)
B (4)
B (4)
B (4)
B (4)
58
0
0
78
38[a]
39
6 (GC)
d
a
b
c
0
0
23
0
0
0
32
d
18 (GC)
5 (GC)
[a] In addition, ring-contracted product 8b (23%) was isolated.
material, was isolated in 23% yield.[12] Moreover, 39% of
the non-fluorinated “homodimer” was also formed by cross
metathesis. From 6d, only a minor amount of the “homodi-
mer” was formed; no lactams could be identified.
Hoveyda’s catalyst (B) was shown to be useful for the
formation of fluorinated dihydropyridine sulfonamides 9,
for which the Grubbs II catalyst (A) failed in our hands.
However, N-tosylpyrroline 9a was not formed at all, and
the yields of compounds 9b–9d were very low (Table 2, en-
tries 5–8). An 80% yield of 9c was obtained with the
Grubbs II catalyst.[7c]
The X-ray structures of fluorinated γ-lactam 8a and fluo-
rinated dihydropyridine derivative 9b are shown in Figure 4.
Figure 3. X-ray structure of compound 6c.[13]
Synthesis of Fluorinated Analogues of Bicyclic Alkaloids
in moderate or good yields, but the yield of ε-lactam 8c was
low. In the latter case, besides 8c, the δ-lactam (i.e., 8b),
formed by isomerization of the double bond in the starting
Natural products very frequently feature N-heterocycles.
Alkaloids like pyrrolizidines and indolizidines are particu-
larly interesting due to their biological activity (Fig-
ure 5).[14,15]
Figure 5. Basic skeletons of pyrrolizidine and indolizidine alka-
loids.
Non-fluorinated bicyclic nitrogen-containing systems
have been synthesized by RCM before,[16] and this area was
reviewed a couple of years ago.[17] Subjecting vinyl fluorides
to RCM would allow the formation of fluorinated alkaloid
scaffolds.
Based on a route towards pyrrolizidines published by
Nakagawa,[18] (S)-2-fluoro-5,6,7,7a-tetrahydropyrrolizin-3-
one (13), a fluorinated analogue of pyrrolactam A, was syn-
thesized from Boc-protected (S)-2-vinylpyrrolidine 10
(Scheme 3; Boc = tert-butoxycarbonyl), which is available
from (S)-prolinol in three known steps.[18]
Boc-deprotection with trifluoroacetic acid to form 11
(43% yield), followed by attachment of the fluoroacryloyl
moiety, gave metathesis precursor 12 in 42% yield. Ring-
closing metathesis using Hoveyda’s catalyst (5 mol-%) led
to a compound tentatively assigned as the desired product,
(S)-2-fluoro-5,6,7,7a-tetrahydropyrrolizin-3-one (13), in
39% yield (based on GC–MS and accurate mass data). Un-
Figure 4. X-ray crystal structures of compounds 8a and 9b.[13]
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M. Marhold, C. Stillig, R. Fröhlich, G. Haufe
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Therefore, 4-allylazetidin-2-one (18a)[20] and 5-allylpyr-
rolidinone (18b)[21] were prepared following known pro-
cedures. Treatment with 2-fluoroacrylic acid chloride gave
metathesis precursors 19a and 19b. Unfortunately all
attempts to cyclize 19a and 19b to give imides 20a and 20b
failed (Scheme 5). The corresponding fluorine-free β-lact-
ams were obtained in good yields 15 years ago.[20] Attempts
to facilitate the RCM of 19b by addition of titanium iso-
propoxide[22] were unsuccessful.
Scheme 3. Formation of (S)-6-fluoro-2,3-dihydro-1H-pyrrolizin-
5(7aH)-one (15) using RCM as key step. TFA = trifluoroacetic
acid.
fortunately, due to its instability during chromatography on
silica gel, it was not possible to isolate a pure sample.
Indolizidines are one of the most common substructures
found in alkaloids. More than 15000 compounds contain
this skeleton.[15] Non-fluorinated indolizidines, such as a
derivative of (–)-coniceine, have already been prepared
using RCM.[19] Considering these results, we planned a syn-
thesis of fluorinated derivative 17. Starting from Boc-pro-
tected (S)-2-allylpyrrolidine (14),[19] nitrogen deprotection
and subsequent attachment of the 2-fluoroacrylic moiety at
the nitrogen of 15 led to metathesis precursor 16. The RCM
reaction was carried out with Grubbs II catalyst (A; 2 mol-
%) to give target compound (S)-6-fluoro-2,3,8,8a-tetra-
hydroindolizin-5(1H)-one (17) in 71% yield (Scheme 4, Fig-
ure 6).
Scheme 5. Attempts to synthesize 3-fluoro-1-azabicycloalk-3-ene-
diones (23a and 23b) by RCM.
In our preliminary communication, we tried to synthe-
size the regioisomer (i.e., 25) of (S)-6-fluoro-2,3,8,8a-tetra-
hydroindolizin-5(1H)-one (17) with the carbonyl function-
ality in the 9-position instead of the 2-position, but got a
yield of the target product of only 1% (by GC)
(Scheme 6).[5] All our subsequent attempts to improve this
cyclization, even under harsh conditions (110 °C), have
failed. A low yield was also observed in the synthesis of the
non-fluorinated analogue of 25 using Schrock’s catalyst.[16c]
Scheme 4. Synthesis of (S)-6-fluoro-2,3,8,8a-tetrahydroindolizin-
5(1H)-one (17).
Scheme 6. Formation of 6-fluoro-1,2,8,8a-tetrahydro-indolizin-
3(5H)-one (25) by RCM of compound 24.[5]
Synthesis of 3-Fluoroquinolone
Fluoroquinolones are appealing targets for synthesis by
RCM. N-Benzyl-3-fluoroquinolone (28) was previously syn-
thesized by Schlosser et al. in an eight-step sequence.[23] We
approached the synthesis of 28 using a three-step sequence
starting from commercially available 2-vinylaniline, which
was first benzylated by reductive amination of benzalde-
hyde according to Schellenberg[24] to give 26.[25] Subsequent
Figure 6. X-ray crystal structure of compound 17.[13]
The successful preparation of pyrrolizidine analogue 13 acylation with α-fluoroacrylic acid chloride gave N-benzyl-
and indolizidine derivative 17 led us to attempt the synthe- N-(2-vinylphenyl)fluoroacrylamide (27). This compound
sis of α-fluorinated α,β-unsaturated azabicyclic imides, i.e., was then subjected to RCM to give N-benzyl-3-
1-azabicyclo[4.2.0]oct-3-ene and 1-azabicyclo-[4.3.0]non-3- fluoroquinolone (28) in 79% yield (Scheme 7). The struc-
ene derivatives.
ture was confirmed by X-ray analysis, as shown in Figure 7.
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Ring-Closing Metathesis of Vinyl Fluorides
phenol derivative 30c failed to form seven-membered ring
31c (Table 3, entry 3). In this case, a “homodimeric” prod-
uct was isolated in 57% yield; isomerization of the double
bond of 30c followed by formation of 31a was not ob-
served.[12]
Scheme 7. Synthesis of N-benzyl-3-fluoroquinolone (28).
Table 3. Synthesized O-heterocycles 31 and 33.
Entry
X
n
R
Catalyst (mol-%) Product Yield [%]
1
2
3
4
5
O
O
O
H2
H2
0
1
0
0
1
H
H
Me
H
A (2)
A (2)
A (2)
B (2)
B (5)
31a
31c
31a
33a
33b
16[a]
0[b]
79
31
H
85[c]
[a] In addition, “homodimeric” product (40%) was observed.[5]
[b] “homodimeric” product (57%) was isolated.[27] [c] Contains im-
purities.
The corresponding benzo-condensed cyclic ethers were
formed with variable levels of success. First, RCM precur-
sors 32 were prepared from 29 with 2-fluoroallyl tosylate.[28]
2-Fluorochromene (33a) was obtained in 31% yield from
32a using Hoveyda’s catalyst (B), and fluorinated benzoxep-
ine derivative 33b was isolated in 85% yield from 32b under
the same conditions. Earlier attempts by Brown to prepare
33b by RCM with Grubbs II catalyst (A) were not entirely
successful. The molecule was formed under harsh condi-
tions, but it could not be isolated or completely charac-
terized.[6]
Figure 7. X-ray crystal structure of N-benzyl-3-fluoroquinolone
(28).[13]
Conclusions
Synthesis of Fluorinated O-Heterocycles
In conclusion, this study shows that Grubbs’s 2nd genera-
tion catalyst (A) and Hoveyda’s catalyst (B) do catalyse
ring-closing metathesis reactions of azadiene systems bear-
ing a fluorine atom on one of the double bonds. Terminal
N-alkenyl-N-benzyl-N-(α-fluoroacryl)amides (1) are cy-
clized to give α-fluoro-α,β-unsaturated γ- and δ-lactams 2
in moderate to good yields, but seven- or eight-membered
lactams were not formed. The cyclization of the analogous
toluenesulfonamides using catalyst A (2 mol-%) was also
successful for γ- and δ-lactams. A 38% yield of the ε-lactam
was even obtained, but the eight-membered lactam was not
formed under the same conditions. Starting from the corre-
sponding N-(2-fluoroallyl)amines instead of the amides in
the presence of catalyst B (4 mol-%), the expected 3-fluoro-
3-pyrrolines were not formed. Even the corresponding six-,
Several RCM-mediated syntheses of non-fluorinated O-
heterocycles are known in the literature.[26] Inspired by
these results, we explored the scope of the formation of
fluorinated analogues of coumarin, chromene, and 1-di-
hydrobenzoxepine derivatives (Scheme 8).
Scheme 8. Formation of O-heterocycles 32 or 34 by RCM.
Starting from 2-(alken-1-yl)phenols 29, RCM precursors seven-, and eight-membered heterocycles were difficult to
30 and 32 that would lead to six- and seven-membered O- access, and were only formed in low yields. Grubbs II cata-
heterocycles 31 or 33 were prepared. These precursors were lyst A failed completely to catalyse the latter cyclizations.
used for RCM with differing degrees of success. A poor Furthermore, a pyrrolizidine derivative, an analogue of
result was obtained for the conversion of o-vinylphenol de- pyrrolactam A, containing an α-fluoro-α,β-unsaturated γ-
rivative 30a into coumarin derivative 31a using Grubbs II lactam, was formed in a low yield. On the other hand, a
catalyst (A), as described in our earlier paper[5] (Table 3, fluorinated indolizidine derivative, i.e., an analogue of con-
entry 1). Starting from 30b, in which the vinyl group is re- icein, was formed from prolinol in five steps in a good over-
placed by a prop-1-en-1-yl group, the yield of 31a was sig- all yield. We do not yet have an explanation as to why the
nificantly higher (Table 3, entry 2). This method minimized RCM of the fluorinated analogue of indolizidine alkaloid
“homodimerization”, which was the main process in the re- 17 worked, while the reaction was unsuccessful with similar
action of 30a.[5] However, attempted cyclization of allyl- systems. We continue to work with other catalysts. Finally,
Eur. J. Org. Chem. 2014, 5777–5785
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M. Marhold, C. Stillig, R. Fröhlich, G. Haufe
FULL PAPER
was washed with water and brine (10 mL each), and dried with
magnesium sulfate. The solvent was removed in vacuo, and the
crude product was purified by column chromatography.
3-fluorocoumarin was prepared using Grubbs II catalyst
(A), and 3-fluorochromene and 3-fluoro-benzoxepine were
synthesized using Hoveyda’s catalyst (B).
Olefin Metathesis (General Procedure 4): The α,ω-diene (0.7 mmol)
was dissolved in dry toluene (1.25 mL) under an argon atmosphere
in a Schlenk flask, and then Grubbs II catalyst (A; 11.89 mg,
0.014 mmol, 2 mol-%) or Hoveyda’s catalyst (B; 8.78 mg,
0.014 mmol, 2 mol-%) was added. The reaction mixture was stirred
at 80 °C for 16 h. The solvent was removed in vacuo, and the crude
product was purified by column chromatography, eluting with an
appropriate solvent.
Experimental Section
General Methods: 1H, 13C, and 19F NMR spectra were recorded
with Bruker DPX300, ARX300, and AV400, and Varian INOVA
(500 MHz) and Unity plus (600 MHz) spectrometers. Spectra were
recorded in solution in CDCl3, CD3CN, or [D6]DMSO, and tetra-
methylsilane was used as an internal standard. CFCl3 was used as
the internal standard for 19F NMR spectra. Chemical shifts are
expressed as δ [ppm] values relative to the internal standard. Mass
spectrometry was carried out with Waters-Micromass GCT or
Quattro LCZ, Bruker Daltronics MicroTof, and Thermo-Fisher
Scientific LTQ Orbitrap LTQ XL mass spectrometers. Merck silica
gel 60 (230–400 mesh) was used for column chromatography. Ana-
lytical and preparative HPLC was carried out with a Knauer RP-
HPLC instrument with K-1800 pumps and an S-2500 UV detector.
Elemental analyses were carried out at the Organisch-Chemisches
Institut, University of Münster using Foss Heraeus CHN-O-Rapid
and Elementar-Analysesystem VarioEL III analysers. Unless other-
wise specified, starting materials were purchased from commercial
suppliers and used without further purification. Solvents were puri-
fied by distillation and, if necessary, dried according to standard
procedures. Starting materials were synthesized according to pub-
lished protocols as reported in the Supporting Information.
Typical Examples – Metathesis Precursors
N-Allyl-N-(4-fluorobenzyl)-2-fluoroacrylamide (1i): According to
General Procedure 1, N-(4-fluorobenzyl)prop-2-en-1-yl-amine (4i;
3.3 g, 20 mmol) was treated with α-fluoroacrylic acid chloride
(2.17 g, 22 mmol) to give 1i (3.12 g, 66%) as a colourless oil after
column chromatography. 1H NMR (300 MHz, CDCl3): δ = 3.89
3
2
3
(d, JH,H = 5.7 Hz, 2 H), 4.55 (s, 2 H), 5.13 (dd, JH,H = 3.5, JH,F
2
3
= 16.9 Hz, 1 H), 5.18 (m, 2 H), 5.34 (dd, JH,H = 3.5, JH,F
=
47.4 Hz, 1 H), 5.77 (m, 1 H), 6.96–7.28 (m, 4 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 47.7, 49.8, 99.7 (2JC,F = 15.0 Hz), 115.6
(3JC,F = 22.1 Hz), 118.5, 130.4, 132.1, 132.6, 158.3 (d, JC,F
=
1
1
2
272.7 Hz), 161.7 (d, JC,F = 245.6 Hz), 162.4 (d, JC,F = 30.9 Hz)
ppm. 19F NMR (CDCl3, 282 MHz): δ = –105.2 (m) –115.5 (m)
ppm. MS (GC–MS, 70 eV): m/z (%) = 237.2 (20) [M]+, 196.2 (100)
[M– C3H5]+, 125.2 (35)[C6H4FCH2NH2]+, 109.2 (55)[C6H4FCH2]+,
95.2 (15) [C6H4F]+, 83.1 (25) [C4H5NO]+, 73.1 (75) [C3H2FO]+,
45.1 (20) [CH2CF]+.
General Procedures
N-(But-3-enyl)-N-(4-fluorobenzyl)-2-fluoroacrylamide (1j): Accord-
ing to General Procedure 2, α-fluoroacrylic acid (360 mg,
4.0 mmol) was treated with N-but-3-enyl-N-(4-fluorobenzyl)amine
(4j; 716 mg, 4.0 mmol) in the presence of EDC (791 mg, 4.0 mmol)
and HOBt (541 mg, 4.0 mmol) to give 1j (575 mg, 57%) as a
Synthesis of Substituted N-Allyl-N-benzyl-α-fluoroacrylamides
A. Coupling of Amines with α-Fluoroacrylic Acid Chloride (General
Procedure 1): The amine was dissolved in dry dichloromethane
(10 mL) and dry DMF (2.5 mL), and the solution was stirred for
1 h. α-Fluoroacrylic acid chloride (108 mg, 1.0 mmol) was then
added, and the solution was stirred at room temperature for 20 h.
Diethyl ether (25 mL) was added, and the mixture was washed with
hydrochloric acid (5%), saturated NaHCO3 solution, and brine
(25 mL). The organic layer was dried with magnesium sulfate, and
the solvent was removed in vacuo. The crude product was purified
by column chromatography, eluting with dichloromethane.
1
colourless oil after column chromatography. H NMR (300 MHz,
3
3
CDCl3): δ = 2.32 (dt, JH,H = 7.5, JH,H = 7.2 Hz, 2 H), 3.36 (dt,
3JH,H = 7.2, 2JH,H = 2.1 Hz, 2 H), 4.58 (s, 2 H), 5.05 (m, 2 H), 5.12
(dd, 2JH,H = 3.0, 3JH,F = 17.1 Hz, 1 H), 5.32 (dd, 2JH,H = 3.0, 3JH,F
3
3
= 47.7 Hz, 1 H), 5.72 (m, 1 H), 7.02 (dd, JH,H = JH,F = 8.7 Hz,
3
2 H), 7.23 (dd, JH,H
=
3JH,F = 7.5 Hz, 2 H) ppm. 13C NMR
2
(75 MHz, CDCl3): δ = 32.9, 46.9, 48.2, 99.5 (d, JC,F = 20.0 Hz),
115.5 (2JC,F = 21.5 Hz, 2 C), 117.2, 129.4 (2 C), 132.2, 134.3, 157.8
1
1
2
B. Coupling of Amines with α-Fluoroacrylic Acid (General Procedure
2): N-Ethyl-NЈ-(3-dimethylaminopropylcarbodiimide) hydrochlor-
ide (EDC; 198 mg, 1.0 mmol) and 1-hydroxy-1H-benzotriazole
hydrate (HOBt; 135 mg, 1.0 mmol) were dissolved in dry dichloro-
methane (10 mL) and dry DMF (2.5 mL), and the mixture was
stirred for 1 h. α-Fluoroacrylic acid (90 mg, 1.0 mmol) and the
amine (1.0 mmol) were then added, and the was stirred at room
temperature for 20 h. Diethyl ether (25 mL) was added, and the
solution was washed with hydrochloric acid (5%), saturated
NaHCO3 solution, and brine (25 mL). The organic layer was dried
with magnesium sulfate, and the solvent was removed in vacuo.
The crude product was purified by column chromatography, eluting
with an appropriate solvent.
(d, JC,F = 270.6 Hz), 162.2 (d, JC,F = 244.0 Hz), 162.4 (d, JC,F
= 29.8 Hz) ppm. 19F NMR (282 MHz, CDCl3): δ = –104.4 (d, 3JF,H
= 35.5 Hz), –105.9 (d, 3JF,H = 35 Hz), –114.9 (m), –121.2 (dd, 3JF,H
= 47.9, 3JF,H = 15.2 Hz) ppm. MS (GC–MS, 70 eV): m/z (%) = 251
(2) [M]+, 210 (14) [M – C3H5]+, 196 (2) [M – C4H7]+, 142 (2) [M –
FC6H5CH2]+, 110 (10) [FC7H8]+, 109 (100) [FC6H5CH2]+, 83 (11)
[FC5H5]+, 73 (10) [CH2CFCO]+, 45 (5) [CH2CF]+. C14H15F2NO
(251.27): calcd. C 66.92, H 6.02, N 5.57; found C 66.69, H 6.14, N
5.57.
N-Allyl-N-(2-fluoroacryl)-4-tosylamide (6a): According to General
Procedure 3, N-allyl-4-tosylamide (5a; 386 mg, 1.8 mmol) was
treated with α-fluoroacrylic acid chloride (198 mg, 1.8 mmol) and
triethylamine (185 mg, 257 μL, 1.8 mmol). Purification by column
chromatography (cyclohexane/ethyl acetate, 5:1) gave target com-
pound 6a (346 mg, 68%) as a white solid, m.p. 62 °C. 1H NMR
Synthesis of N-Alkenyl-N-(2-fluoroallylic)-N-tosyl Amides (General
Procedure 3): The amine (4.0 mmol) was dissolved in dry DMF
(20 mL), and 2-fluoroallyl tosylate (0.92 g, 4.0 mmol) and potas-
sium carbonate (1.19 g, 4.0 mmol) were added at room temp. The
mixture was then heated at reflux for 48 h. The mixture was al-
lowed to cool to room temperature, then diethyl ether (20 mL) and
water (20 mL) were added. The aqueous phase was separated and
extracted with diethyl ether (10 mL). The combined organic phase
4
2
(300 MHz, CDCl3): δ = 2.44 (s, 3 H), 4.45 (ddd, JH,H = 1.6, JH,H
3
2
= 3.1, JH,H = 5.7 Hz, 2 H), 5.17–5.29 (m, 3 H), 5.42 (dd, JH,H
=
3
3
3
3.6, JH,F = 45.2 Hz, 1 H), 5.82 (ddt, JH,H = 5.6, JH,H = 10.6,
3JH,H = 16.6 Hz, 1 H), 7.33 (d, 3JH,H = 8.1 Hz, 2 H), 7.88 (d, 3JH,H
= 8.4 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 21.6, 49.1,
2
102.3 (d, JC,F = 15.2 Hz), 118.7, 128.6 (2 C), 129.5 (2 C), 132.4,
5782
www.eurjoc.org
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 5777–5785

Ring-Closing Metathesis of Vinyl Fluorides
1
3
3
135.7, 145.1, 156.1 (d, JC,F = 271.1 Hz), 162.0 (2JC,F = 33.3 Hz)
CDCl3): δ = –116.8 (dd, JF,H = 8.3, JF,H = 41.7 Hz) ppm. MS
(GC–MS, 70 eV): m/z (%) = 206 (46) [M]+, 186 (8) [M – HF]+, 133
(100) [M – CH2CFCO]+, 131 (62), 115 (17), 105 (74), 91 (3)
[C6H5CH2]+, 89 (10) [CH2CFCO2]+, 77 (31) [C6H5]+, 73 (58)
[CH2CFCO]+, 65 (3) [C5H5]+, 45 (3) [CH2CF]+. HRMS (ESI):
calcd. for C12H11FO2 206.0743; found 206.0734.
ppm. 19F NMR (282 MHz, CDCl3): δ = –108.8 (dd, JH,F = 15.4,
3
3JH,F = 43.7 Hz) ppm. MS (GC–MS, 70 eV): m/z (%) = 283 (0.2)
[M]+, 219 (12), 156 (1) [CH3C6H5SO2H]+, 155 (13) [CH3C6H5SO2]+,
128 (6) [M – CH3C6H5SO2]+, 112 (83) [C6H7NF]+, 91 (100) [C7H7]+,
73 (53) [C3H2OF]+, 65 (45) [C5H5]+, 41 (384) [C3H5]+.
Typical Examples – Metathesis Products.
(S)-1-(2-Allylpyrrolidin-1-yl)-2-fluoroprop-2-en-1-one (16): Accord-
ing to General Procedure 2, EDC (1.27 g, 6.40 mmol) and HOBt
(0.86 g, 6.40 mmol) were dissolved in dry dichloromethane (64 mL)
and DMF (16 mL). After 1 h, amine (S)-15 (0.71 g, 6.40 mmol) and
fluoroacrylic acid (0.58 g, 6.40 mmol) were added, and the mixture
was stirred overnight. Purification by column chromatography gave
compound 16 (936 mg, 80%) as a colourless oil. 1H NMR
(300 MHz, CDCl3): δ = 1.72–1.96 (m, 4 H, 5-H/6-H), 2.16–2.44 (m,
2 H, 3-H), 3.62 (m, 2 H, 7-H), 4.23 (m, 1 H, 4-H), 5.08 (m, 2 H,
1-H), 5.11 (m, 1 H, 10-Hcis), 5.44 (dd, 2JH,H = 2.2, 3JH,F = 47.0 Hz,
1 H, 10-Htrans), 5.75 (m, 1 H, 2-H) (broad signals because of dy-
namic effects of the fluoroacrylate group) ppm. 13C NMR
(75 MHz, CDCl3): δ = 24.6 (t, C-6), 28.5 (t, C-5), 36.9 (t, C-3), 48.2
(d, C-7), 57.8 (s, C-4), 99.5 (dt, 2JC,F = 15.8 Hz, C-10), 117.5 (t, C-
3-Fluoro-1-(4-fluorobenzyl)-1H-pyrrol-2(5H)-one (2i): The synthesis
was carried out according to General Procedure 4, starting from N-
allyl-N-(4-fluorobenzyl)-2-fluoroacrylamide (1i; 237 mg, 1.0 mmol)
with either Grubbs II catalyst (A; 18 mg, 0.021 mmol, 2 mol-%) or
Hoveyda catalyst (B; 12 mg, 0.020 mmol, 2 mol-%). Compound 2i
was obtained (144 mg, 70% with Grubbs II catalyst; 146 mg, 71%
with Hoveyda’s catalyst) as colourless crystals, m.p. 77 °C (diethyl
ether). 1H NMR (300 MHz, CDCl3): δ = 3.78 (dd, JH,H = 2.2,
3
2JH,F = 5.8 Hz, 2 H), 4.69 (s, 2 H), 6.29 (dt, JH,H = 2.2, JH,F
=
3
3
0.8 Hz, 1 H), 7.34–7.64 (m, 4 H, 7-H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 45.2 (d, 3JC,F = 5.7 Hz), 46.1, 112.8 (d, 2JC,F = 6.5 Hz),
115.7 (d, 2JC,F = 21.6 Hz), 129.8 (d, 3JC,F = 8.2 Hz), 132.1 (d, 4JC,F
1
1
= 3.2 Hz), 152.7 (d, JC,F = 276.3 Hz), 162.4 (d, JC,F = 246.7 Hz),
1
1), 134.3 (s, C-2), 158.2 (d, JC,F = 273.3 Hz, C-9), 160.2 (s, C-8)
2
162.8 (d, JC,F = 31.2 Hz) ppm. 19F NMR (282 MHz, CDCl3): δ =
3
ppm. 19F NMR (282 MHz, CDCl3): δ = –109.5 (dd, JF,H = 16.4,
3
–114.5 (m), –136.6 (d, JH,F = 0.8 Hz) ppm. MS (GC–MS, 70 eV):
3JF,H = 46.9 Hz) ppm. Because of the hindered rotation of the
fluoroacrylamide group, a second set of minor signals is present in
13C and 19F NMR spectra (see Supporting Information). MS (GC–
MS, 70 eV): m/z (%) = 183 (0) [M]+, 142 (95) [M – CH2CHCH2]+,
106 (3), 73 (100) [COCFCH2]+, 70 (48) [142 – COCFCH2]+, 68 (6),
55 (4), 45 (41) [CFCH2]+, 41 (38) [CH2CHCH2]+.
m/z (%) = 209.2 (65) [M]+, 208.2 (55) [M – H]+, 109.2 (100)
[C6H4FCH2]+ 86.1 (25) [C4H3FO]+, 58.1 (10) [C3H3F]+, 45.1 (15)
[CH2CF]+. C11H9ClFNO (225.65): calcd. C 63.16, H 4.34, N 6.70;
found C 63.14, H 4.05, N 6.50.
3-Fluoro-1-(4-fluorobenzyl)-5,6-dihydropyridin-2(1H)-one (2j): The
synthesis was carried out according to General Procedure 4, start-
ing from N-(but-3-enyl)-N-(4-fluorobenzyl)-α-fluoroacrylamide (1j;
175.7 mg, 0.7 mmol) and catalyst A (2 mol-%). Compound 2j was
obtained (119 mg, 76%) as a brownish solid, m.p. 69 °C (diethyl
ether). 1H NMR (300 MHz, CDCl3): δ = 2.37 (m, 2 H), 3.32 (t,
N-Benzyl-2-fluoro-N-(2-vinylphenyl)acrylamide (27): According to
General Procedure 1, amine 26 (469 mg, 2.24 mmol) was treated
with fluoroacrylic acid chloride (243 mg, 2.24 mmol) in the pres-
ence of Et3N (226 mg, 2.24 mmol) in dichloromethane (15 mL) to
give compound 27 (482 mg, 76%). 1H NMR (300 MHz, CDCl3): δ
3JH,H = 7.2 Hz, 2 H), 4.57 (s, 2 H), 5.98 (dt, JH,H = 4.5, JH,F
=
3
3
2
2
3
15.0 Hz, 1 H), 6.99 (m, 2 H), 7.26 (m, 2 H) ppm. 13C NMR
= 4.33 (d, JH,H = 13.8 Hz, 1 H), 4.90 (dd, JH,H = 3.0, JH,F
=
2
3
3
15.9 Hz, 1 H), 5.30 (dd, JH,H = 3.0, JH,F = 47.3 Hz, 2 H), 5.71
(d, JH,H = 17.5 Hz, 2 H), 6.62 (dd, JH,H = 11.0, JH,H = 17.5 Hz,
(75 MHz, CDCl3): δ = 21.1 (dt, JC,F = 6.4 Hz), 44.5, 49.0, 112.8
3
3
3
2
2
(dd, JC,F = 15.2 Hz), 115.4 (2 dd, JC,F = 21.4 Hz), 129.7 (2 dd,
3
3JC,F = 7.6 Hz), 132.4 (d, JC,F = 4.1 Hz), 149.6 (d, JC,F
=
4
1
1 H), 6.72 (d, JH,H = 7.8 Hz, 1 H), 7.09–7.30 (m, 7 H), 7.56 (d,
3JH,H = 7.8 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 53.7,
2
1
253.3 Hz), 159.7 (d, JC,F = 31.6 Hz), 162.2 (d, JC,F = 244.4 Hz)
ppm. 19F NMR (282 MHz, CDCl3): δ = –114.9 (m), –127.5 (m)
ppm. MS (GC–MS, 70 eV): m/z (%) = 223 (41) [M]+, 222 (5) [M –
H]+, 123 (13) [FC6H5CH2N]+, 110 (10) [FC7H8]+, 109 (100)
[FC6H5CH2]+, 95 (15) [FC6H6]+, 83 (33) [FC5H5]+, 57 (24)
[FC3H2]+, 51 (21) [C4H3]+.
100.7 (dt, 2JC,F = 15.4 Hz), 117.0, 126.3, 127.7, 128.2, 128.3, 128.4,
1
129.0, 129.6, 131.6 (2 C), 135.2, 135.9, 138.7, 157.2 (d, JC,F
=
272.3 Hz), 161.7 (d, JC,F = 28.2 Hz) ppm. 19F NMR (282 MHz,
2
3
3
CDCl3): δ = –106.65 (dd, JH,F = 45.7, JH,F = 15.9 Hz) ppm. MS
(GC–MS, 70 eV): m/z (%) = 281/282 (4/0.5) [M]+, 261 (1) [M – HF]+,
235 (1) [261 – C2H2]+, 208 (4) [M – C2H2CFCO]+, 190 (26) [M –
C6H5CH2]+, 178 (2) [M – C6H4CHCH2]+, 118 (3) [C8H7NH]+, 103
(2) [C8H7]+, 91 (100) [C6H5CH2]+, 77 (5) [C6H5]+, 73 (8)
[CH2CFCO]+, 65 (9) [C5H5]+.
3-Fluoro-N-tosyl-1H-pyrrol-2(5H)-one (8a): The synthesis was car-
ried out according to General Procedure 4, but with 2 mol-%
Grubbs II catalyst (15 mg, 0.024 mmol), starting from N-allyl-N-(2-
fluoroacryl)-N-tosylamide (6a; 346 mg, 1.2 mmol). The metathesis
product was separated by column chromatography (Et2O), and
purified by crystallization (CH2Cl2) to give 8a (180 mg, 58%) as
white crystals, m.p. 151 °C (CH2Cl2). 1H NMR (300 MHz, CDCl3):
2-Prop-1-enylphenyl-α-fluoroacrylate (30b): The synthesis was car-
ried out according to General Procedure 1, starting from (E/Z)-2-
prop-1-enylphenol (29b; 2.68 g, 20.0 mmol) and α-fluoroacrylic
acid chloride (2.10 g, 23.0 mmol). The crude product was purified
by chromatography (toluene/ethyl acetate, 4:1) to give an (E/Z)-
mixture of 30b (3.20 g, 78%) as a colourless liquid. 1H NMR
(300 MHz, CDCl3): δ = 1.75 (dd, 3JH,H = 1.6, 4JH,H = 1.6 Hz, 3 H,
3
4
δ = 2.44 (s, 3 H), 4.35 (dd, JH,H = 2.4, JH,F = 6.0 Hz, 2 H) 6.51
(dt, 3JH,F = 0.9, 3JH,H = 2.4 Hz, 1 H) 7.35 (d, 3JH,H = 8.1 Hz, 2 H),
3
7.95 (d, JH,H = 8.7 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ
2
= 21.6, 45.3, 117.2 (d, JC,F = 7.5 Hz), 128.0 (2 C), 129.9 (2 C),
3
3
1-Htrans), 1.87 (dd, JH,H = 6.6 Hz, 3 H, 1-Hcis), 5.03 (dm, JH,H
=
134.6, 145.7, 150.7 (d, 1JC,F = 277.8 Hz), 160.1 (d, 2JC,F = 30.5 Hz)
ppm. 19F NMR (282 MHz, CDCl3): δ = –135.2 (d, 3JH,F = 8.3 Hz)
ppm. MS (GC–MS, 70 eV): m/z (%) = 255 (0) [M]+, 191 (100),
155 (9) [CH3C6H5SO2]+, 100 (8) [M – CH3C6H5SO2]+, 91 (96)
2
8.7 Hz, 1 H, 2-Htrans), 5.08 (m, 1 H, 2-Hcis), 5.49 (dd, JH,H = 3.3,
3JH,F = 12.9 Hz, 1 H, 12-Hcis), 5.88 (dd, JH,H = 3.3, JH,F
=
2
3
42.9 Hz, 1 H, 12-Htrans), 5.88 (m, 1 H, 3-H), 7.05–7.51 (m, 4 H,
5-H–8-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.4/18.8, 104.0/ [C7H7]+, 65 (45) [C5H5]+, 41 (5) [C3H5]+. HRMS (ESI): calcd. for
2
104.2 (t, JC,F = 15.3 Hz), 121.8/122.1, 123.7/126.1, 123.9/126.6,
C11H10FNO3SNa [M
+
Na]+ 278.0263; found 278.0258.
126.7/128.0, 127.7/129.0, 129.6/130.6, 146.7/147.7, 152.8 (d, 1JC,F
=
C11H10FNO3S (255.27): calcd. C 51.76, H 3.95, N 5.49; found C
51.86, H 3.93, N 5.37.
2
262.0 Hz), 158.3/158.8 (d, JC,F = 36.2 Hz). 19F NMR (282 MHz,
Eur. J. Org. Chem. 2014, 5777–5785
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5783

M. Marhold, C. Stillig, R. Fröhlich, G. Haufe
FULL PAPER
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(S)-6-Fluoro-2,3,8,8a-tetrahydroindolizin-5(1H)-one (17): According
to General Procedure 4, (S)-16 (117 mg, 0.64 mmol) was dissolved
in dry toluene (1.2 mL) and treated with Grubbs II catalyst (A;
1
11.0 mg) to give (S)-17 (71 mg, 71%) as white crystals. H NMR
(300 MHz, CDCl3): δ = 1.65 (m, 1 H), 1.86 (m, 1 H), 2.07 (m, 1
H), 2.25 (m, 1 H), 2.31 (m, 1 H), 2.46 (m, 1 H), 3.49 (m, 1 H), 3.66
(m, 1 H), 3.82 (m, 1 H), 5.94 (m, 1 H) ppm. 13C NMR (75 MHz,
3
CDCl3): δ = 23.6, 27.6 (dt, JC,F = 5.9 Hz), 33.0, 44.3, 56.9, 111.4
2
1
2
(dd, JC,F = 14.8 Hz), 151.5 (d, JC,F = 255.7 Hz), 157.9 (d, JC,F
= 28.6 Hz) ppm. 19F NMR (282 MHz, CDCl3): δ = –130.5 (t, 3JF,H
= 9.2 Hz) ppm. MS (ESI): m/z (%) = 178 [M + Na]+.
1-Benzyl-3-fluoroquinolin-2(1H)-one (28): The synthesis was carried
out according to General Procedure 4 (16 h at 80 °C), starting from
27 (482 mg, 1.71 mmol). Chromatographic purification gave com-
1
pound 28 (342 mg, 79%) as a brownish oil. H NMR (300 MHz,
3
[3]
[4]
a) Y. Chauvin, Angew. Chem. Int. Ed. 2006, 45, 3740–3747;
Angew. Chem. 2006, 118, 3824–3831; b) R. R. Schrock, Angew.
Chem. Int. Ed. 2006, 45, 3748–3759; Angew. Chem. 2006, 118,
3832–3844; c) R. H. Grubbs, Angew. Chem. Int. Ed. 2006, 45,
3760–3765; Angew. Chem. 2006, 118, 3845–3850.
CDCl3): δ = 5.58 (s, 2 H), 7.18–7.45 (m, 9 H), 7.51 (d, JH,H
=
7.8 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 46.3, 115.1,
2
118.5 (d, JC,F = 17.4 Hz), 123.1, 126.6, 127.4, 128.4, 128.5, 128.8,
1
2
129.5, 135.6, 136.4, 150.4 (d, JC,F = 252.0 Hz), 156.6 (d, JC,F
=
25.6 Hz) ppm. 19F NMR (282 MHz, CDCl3): δ = –128.20 (d, JF,H
= 10.6 Hz) ppm. MS (GC–MS, 70 eV): m/z (%) = 253/254 (28/3)
[M]+, 252 (9) [M – H]+, 176 (3) [M – C6H5 + H]+, 162 (1) [M –
C7H6]+, 146 (19) [M – C7H8N]+, 91 (100) [C7H7]+, 77 (2) [C6H5]+,
65 (13).
3
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3-Fluorocoumarin (31a): According to General Procedure 4, 2-prop-
1-enylphenyl α-fluoroacrylate (30b; 206 mg, 1.0 mmol) was treated
with Grubbs II catalyst (A; 17 mg, 0.02 mmol, 2 mol-%). Purifica-
tion by chromatography with diethyl ether, followed by recrystalli-
zation from toluene gave compound 31a (130 mg, 79%), m.p.
1
147 °C (toluene). H NMR (300 MHz, CDCl3): δ = 7.13–7.65 (m,
5 H, 2-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 116.7, 118.0 (d,
3JC,F = 3.7 Hz), 121.1 (dd, 2JC,F = 16.4 Hz), 125.2, 127.7 (dd, 4JC,F
= 6.2 Hz), 130.7, 146.5 (d, 1JC,F = 259.1 Hz), 147.66, 154.2 (d, 2JC,F
= 32.9 Hz) ppm. 19F NMR (282 MHz, CDCl3): δ = –129.9 (d, 3JF,H
= 8.2 Hz) ppm. MS (GC–MS, 70 eV): m/z (%) = 164 (82) [M]+, 136
(55) [M – CO]+, 108 (100), 107 (75), 81 (25), 63 (35).
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Received: May 4, 2014
Published Online: August 5, 2014
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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