Synthesis and cycloaddition reactions of ethyl 3-aryl-2- (perfluoroalkanesulfonyl)propenoates - A revised stereochemistry of the cyclopentadiene adducts

Article abstract of DOI:10.1002/(sici)1099-0690(199911)1999:11<2969::aid-ejoc2969>3.0.co;2-u

Ethyl 3-aryl-2-(perfiuoroalkanesulfonyl)propenoates were prepared by the Knoevenagel reaction from various aldehydes and ethyl (trifluoromethanesulfonyl)acetate or ethyl (nonafluorobutanesulfonyl)acetate. These deactivated olefins were used in Dials-Alder

Full text of DOI:10.1002/(sici)1099-0690(199911)1999:11<2969::aid-ejoc2969>3.0.co;2-u

FULL PAPER
Synthesis and Cycloaddition Reactions of Ethyl
3-Aryl-2-(perfluoroalkanesulfonyl)propenoates –
A Revised Stereochemistry of the Cyclopentadiene Adducts
[a]
[a]
[a]
[b]
[a]
´
´
Regis Goumont,* Karine Magder, Marc Tordeux, Jerome Marrot, Francois Terrier,
¸
and Claude Wakselman*[a]
Keywords: Vinyl triflones / Vinyl nonaflones / Knoevenagel reaction / Diels–Alder reaction
Ethyl 3-aryl-2-(perfluoroalkanesulfonyl)propenoates were
prepared by the Knoevenagel reaction from various
aldehydes and ethyl (trifluoromethanesulfonyl)acetate or
ethyl (nonafluorobutanesulfonyl)acetate. These deactivated
cyclopentadiene. The reactions occurred at room
temperature to give [4+2] cycloadducts as racemates. The
endo stereochemistry of the carboxylic ester and aryl groups
was unambiguously assigned by NOE experiments and X-
olefins were used in Diels–Alder cycloaddition reactions with ray analysis.
purpose. The formation of a condensation product derived
Introduction
from p-dimethylaminobenzaldehyde in acetic anhydride was
described by YagupolЈskii.[19] However, Hanack was unable
to reproduce this method with other aromatic aldehydes.[15]
As a result, new reaction conditions were developed in
which catalytic amounts of piperidine and acetic acid in
benzene are used to prepare 3-aryl-2-(nonafluorobutanesul-
fonyl)propenoates.
In this paper, we report the preparation of vinyl triflones
4 by the condensation of ethyl (trifluoromethanesulfonyl)-
acetate (2)[6,20Ϫ21] with various aldehydes 3a؊d (Schemes 1
and 2). The precursor 2 was prepared by the reaction of
sodium triflinate (1) with ethyl bromoacetate.[6,20Ϫ21]
[1Ϫ6]
Perfluoroalkanesulfonyl groups RFSO2
are of special
interest in organic chemistry because of their manifold reac-
tivity Ϫ they may function either as electrophiles or as nu-
cleofugic leaving groups, carrying away the electron pair to
form a sulfinate anion.[7Ϫ8] These powerfully electron-with-
[1,9Ϫ10]
drawing
groups can stabilize negatively charged car-
banions[11][12] or activate olefins in nucleophilic addition[1]
or cycloaddition reactions.[1,13Ϫ15] Vinyl triflones, although
structurally simple, are not widely available. Some examples
were prepared by isomerization of allylic triflones[1] (mi-
gration into conjugation of the carbonϪcarbon double
bond) (Equation 1). Condensation of styrenes with trifluor-
omethanesulfonyl chloride, catalysed by a ruthenium com-
plex (Equation 2), was found to give the corresponding vi-
nyl triflones, but only as secondary products because the
reaction proceeds mainly with extrusion of sulfur diox-
ide.[16]
Interestingly, the preparation of unsaturated sulfonyl
esters is well known, and the Knoevenagel condensation re-
action[14Ϫ15,17Ϫ18] is the most convenient method for this
Scheme 1. Knoevenagel condensations of simple aromatic aldehy-
des with ethyl (trifluoromethanesulfonyl) acetate
[a]
ˆ
Laboratoire SIRCOB, ESA CNRS 8086, Batiment Lavoisier,
´
Universite de Versailles,
45, avenue des Etats-Unis, F-78035 Versailles Cedex, France
Institut Lavoisier, Laboratoire IREM, CNRS CO173, Univer-
[b]
The esters 4 were used in DielsϪAlder condensation re-
actions with cylopentadiene (5). These reactions occurred
smoothly within 2Ϫ5 d at room temperature in carbon
tetrachloride to give the [4ϩ2] cycloadducts 6 in fair to
good yields. The structure of 6 and, thus, the presence of a
´
site de Versailles,
45, avenue des Etats-Unis, F-78035 Versailles Cedex, France
E-mail: goumont@chimie.uvsq.fr
Supporting information for this article is available on the
WWW under http://www.wiley-vch.de/home/eurjoc or from
the author.
Eur. J. Org. Chem. 1999, 2969Ϫ2976
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ193X/99/1111Ϫ2969 $ 17.50ϩ.50/0
2969

R. Goumont, K. Magder, M. Tordeux, J. Marrot, F. Terrier, C. Wakselman
FULL PAPER
3J(COϪHα) coupling constant of 11.3 Hz, measured in the
proton-coupled 13C-NMR spectra, was in agreement with
a trans coupling and an (E) configuration[22][23] of the Cϭ
C double bond. The NMR data of 4b were similar to that
of 4a [δ(Hα) ϭ 7.97], therefore the (E) configuration could
also be assigned to 4b [3J(COϪHα) ϭ 11.3 Hz].[22][23]
IR data[24] agreed with vinylic structures [ν(CO) ϭ 1729
and 1734 cmϪ1, for 4a and 4b, respectively; ν(CϭC) ϭ 1607
for 4a and ν(CϭC) ϭ 1612 cmϪ1 for 4b]. Mass spec-
trometry[24] also agreed well with the above structures. Be-
side base peaks (m/z ϭ 349 and 331 [M ϩ Na]ϩ for 4a and
4b, respectively), the mass spectra also exhibited other
peaks (m/z ϭ 675 for 4a and 639 for 4b) corresponding to
[2 M ϩ Na]ϩ.
Scheme 2. Knoevenagel condensation of salicylaldehyde with ethyl
(trifluoromethanesulfonyl) acetate
DielsϪAlder addition product, was clearly established from
NMR data, especially with the aid of NOE experiments.
The stereochemistry of the cycloaddition was unambigu-
ously assigned by an X-ray analysis of 6a. The reaction ap-
peared to be highly stereoselective and, in all cases, only the
endo isomer was observed and isolated.
Vinyl triflone 4c was obtained as a pale yellow solid from
trans-cinnamaldehyde in quantitative yield. Its 1H-NMR
spectra appeared to be similar to those of 4a and 4b, with
two new second-order signals for the ethylenic protons Hα
(δ ϭ 7.42) and Hβ (δ ϭ 7.96).
Results and Discussion
1. Synthesis of Vinyl Triflones 4a؊d
The Knoevenagel condensation reaction between acti-
vated aldehydes 3a؊d and sulfonyl ester 2 led to the forma-
tion of only the (E) isomers 4a؊d in good yields. These
compounds were characterized by their spectral data
(Table 1).
Treatment of salicylaldehyde (3d) with ethyl (trifluorome-
thanesulfonyl)acetate (2) did not result in the expected vinyl
triflone 4dЈ, which was not isolable. Instead, a coumarin
derivative 4d was obtained as a pale yellow solid in 70%
yield. Formation of 4d may be explained by an intramolecu-
lar cyclization of 4dЈ with concomitant elimination of an
ethanol molecule (Scheme 2).[25] The absence of the signals
due to the ethyl group, in both the 1H- and 13C-NMR spec-
tra, provide strong support for the formation of this com-
The 1H- and 13C-NMR spectra recorded in CDCl3 for 4a
were in agreement with the vinyl triflone structure. Besides
1
the signals of the aromatic protons, the H-NMR spectra
contained triplet and quadruplet peaks (δ ϭ 1.35/4.42 )
typical for the ethyl group, as well as a characteristic Hα
(δ ϭ 7.93) singlet which was deshielded by the electron-
withdrawing ester and triflyl groups. Each carbon atom of
1
pound. H- and 13C-NMR data are collected in Table 1.
As we will describe later in this paper, these vinyl triflones
the aromatic ring gave rise to a doublet [δ(C-1) ϭ 126.72, reacted readily with cyclopentadiene to give cycloadducts
3
4J(C-1ϪF) ϭ 3.4 Hz; δ(C-2) ϭ 133.71, J(C-2ϪF) ϭ 9.3 6a؊d with high stereoselectivity. However, the endo stereo-
Hz; δ(C-3) ϭ 116.68, 2J(C-3ϪF) ϭ 22.3 Hz; δ(C-4) ϭ chemistry of these adducts contrasted with the exo stereo-
1
165.53, J(C-4ϪF) ϭ 258.0 Hz] in the 13C-NMR spectrum. chemistry of the adducts derived from vinyl nonaflones[15]
The coupling between the fluorine atom and the aromatic as previously reported by Hanack and co-workers. To
carbon atoms made the unambiguous assignment of the understand and explain this difference of stereoselectivity,
other carbon resonances possible (Table 1). The the vinyl nonaflones 8a؊d were prepared.
Table 1. NMR data of the vinyl triflones 4a؊d
Product
1H NMR
13C NMR
19F NMR
4a
7.93 (s. 1 H. Ηα), 7.64 (dd, J ϭ 8.5 Hz, J ϭ 165.53 (d, J ϭ 258.0 Hz, C-4), 160.99 (CO), Ϫ75.8 (s,
3 F, SO2CF3),
8.43 Hz, 2 H, 2-H), 7.17 (dd, J ϭ 5.5 Hz, J ϭ 151.15 (Cα), 133.71 (d, J ϭ 9.3 Hz, C-2), Ϫ103.3 (m, 1 F, C6H4ϪF)
8.43 Hz, 2 H, 3-H), 4.42 (q, J ϭ 7 Hz, 2 H, 126.72 (d, J ϭ 3.4 Hz, C-1), 126.30 (Cβ),
CH2), 1.35 (t, J ϭ 7 Hz, 3 H, CH3)
119.75 (q, J ϭ 327.2 Hz, CF3), 116.68 (d, J ϭ
22.3 Hz, C-3), 63.45 (CH2), 13.62 (CH3)
4b
4c
7.97 (s, 1 H, Ηα), 7.56 (m, 2-H, 3 H, 4-H), 161.08 (CO), 152.77 (Cα), 133.31 (C-4), 130.88 Ϫ76.0 (s, SO2CF3)
7.47 (m, 2 H, 3-H), 4.42 (q, J ϭ 7.2 Hz, 2 H, (C-2), 130.36 (C-1), 129.19 (C-3), 126.22 (Cβ),
CH2), 1.34 (t, J ϭ 7.2 Hz, 3 H, CH3)
119.75 (q, J ϭ 327.2 Hz, CF3), 63.33 (CH2),
13.54 (CH3)
8.03 (d, J ϭ 11.4 Hz, 1 H, Ηα), 7.96 (dd, J ϭ 160.43 (CO), 158.73 (Cα), 154.26 (Ca), 134.57 Ϫ75.8 (s, SO2CF3)
14.3 Hz, J ϭ 11.4 Hz, 1 H, Hb), 7.63Ϫ7.47 (C-1), 131.98 (C-4), 129.25 (C-3), 129.17 (C-
(m, 5 H, 2-H, 3-H, 4-H), 7.42 (d, J ϭ 14.3 2), 122.57 (Cβ), 122.60 (Cb), 119.67 (q, J ϭ
Hz, 1 H, Ha), 4.42 (q, J ϭ 7 Hz, 2 H, CH2), 327.2 Hz, CF3), 62.54 (CH2), 13.85 (CH3)
1.41 (t, J ϭ 7 Hz, 3 H, CH3)
4d
8.84 (s, 1 H, 4-H), 7.86 (t, J ϭ 7.9 Hz, 1 H, 156.21 (C-9), 155.13 (C-4), 153.66 (C-2), Ϫ75.7 (s, SO2CF3)
7-H), 7.79 (d, J ϭ 8.2 Hz, 1 H, 5-H), 7.50 (d, 137.69 (C-5), 131.16 (C-7), 126.02 (C-6), 123.1
J ϭ 6.7 Hz, 1 H, 6-H), 7.49 (t, J ϭ 7.9 Hz, 1 (q, J ϭ 324.3 Hz, CF3), 120.15 (C-3), 117.45
H, 8-H)
(C-8), 116.77 (C-10)
2970
Eur. J. Org. Chem. 1999, 2969Ϫ2976

Synthesis and Cycloaddition Reactions of Ethyl 3-Aryl-2-(perfluoroalkanesulfonyl)propenoates
FULL PAPER
2. Synthesis of Vinyl Nonaflones 8a؊d
and 13C) for 8a؊d were simply assigned by comparison
with the data of 4a؊d. The nonaflone[15] 8b was previously
described by Hanack, and our spectral and experimental
data for this compound agree with the reported data.[15]
Finally, in the 19F-NMR spectra, four signals, which are
typical for the nonaflyl group, were observed [for 8a: δ ϭ
Ϫ81.0 (CF3), Ϫ109.1 (CF2ϪSO2), Ϫ121.2 (CF2ϪCF2Ϫ
SO2), Ϫ126.2 (CF2ϪCF3)].
These compounds were prepared by the Knoevenagel
condensation reaction of ethyl (nonafluorobutanesulfonyl)-
acetate (7) and the aldehydes 3a؊d (Schemes 2 and 3) by
the previously established reaction conditions (catalytic
amounts of piperidine and glacial acetic acid in toluene).[15]
The nonaflyl ester 7 was prepared by condensation of non-
aflyl fluoride with sodium malonate, followed by a decar-
boxylation step.[19][26] The precursor 7 could also be pre-
pared by the reaction of nonaflylmethane with butyllithium
in tetrahydrofuran, followed by the addition of diethyl car-
bonate.[26][27]
3. Preparation of the Cycloadducts
a. Reaction of Triflones 4a؊d with Cyclopentadiene
The deactivated vinyl triflones reacted as dienophiles in
DielsϪAlder reactions with cyclopentadiene (5) giving
DielsϪAlder cycloadducts 6a؊d in modest to good yields
(Schemes 4 and 5).
Scheme 3. Knoevenagel condensations of aromatic aldehydes with
ethyl (nonafluorobutanesulfonyl) acetate
The products 8a؊d were obtained as single (E) isomers
1
in fair to good yields. H- and 13C-NMR spectra of 8a؊d
were found to be very similar to those obtained for the tri-
Scheme 4. DielsϪAlder reactions of cyclopentadiene with simple
flones 4a؊d (Tables 1 and 2), therefore the resonances (1H vinyl triflones and nonaflones
Table 2. NMR data for the vinyl nonaflones 8a؊d
Product
1H NMR
13C NMR
19F NMR
8a
7.97 (s, 1 H, Hα), 7.63 (dd, J ϭ 8.6 Hz, J ϭ 165.57 (d, J ϭ 257.7 Hz, C-4), 161.0 (CO), Ϫ126.2 (m, 2 F, CF2CF3),
5.5 Hz, 2 H, 2-H), 7.18 (“t”, J ϭ 8.4 Hz, 2 H, 151.94 (Cα), 133.68 (d, J ϭ 9.6 Hz, C-2), Ϫ121.2
(m, F,
2
3-H), 4.42 (q, J ϭ 7 Hz, 2 H, CH2), 1.35 (t, 127.41 (Cβ), 126.73 (d, J ϭ 3.4 Hz, C-1), CF2CF2ϪSO2), Ϫ109.1 (m,
J ϭ 7 Hz, 3 H, CH3)
116.73 (d, J ϭ 22 Hz, C-3), 63.46 (CH2), 2 F, CF2ϪSO2), Ϫ103.2 (s,
13.63 (CH3)
1 H, C6H4ϪF), Ϫ81.0 (m, 3
F, CF3)
8b
8c
8d
7.91 (s, 1 H, Hα), 7.5 (m, 5 H, 2-H, 3-H, 4- 161.09 (CO), 153.25 (Cα), 133.35 (C-4), 130.86 Ϫ126.2 (m, 2 F, CF2CF3),
H), 4.42 (q, J ϭ 7 Hz, 2 H, CH2), 1.34 (t, J ϭ (C-2), 130.43 (C-1), 129.20 (C-3), 127.77 (Cβ), Ϫ121.3
(m,
2
F,
7.3 Hz, 3 H, CH3)
63.28 (CH2), 13.39 (CH3)
CF2CF2ϪSO2), Ϫ109.3 (m,
2 F, CF2ϪSO2), Ϫ81.2 (m, 3
F, CF3)
8.02 (d, J ϭ 11.4 Hz, 1 H, Hα), 7.99 (dd, J ϭ 160.44 (CO), 159.27 (Cα), 154.47 (Ca), 134.52 Ϫ126.2 (m, 2 F, CF2CF3),
11.4 Hz, J ϭ 14.3 Hz, 1 H, Hb), 7.43 (d, J ϭ (C-1), 132.02 (C-4), 129.23 (C-3), 129.18 (C- Ϫ121.2
(m,
2
F,
16.5 Hz, 1 H, Ha), 7.64Ϫ7.47 (2 m, 2 H, 3 H, 2), 123.63 (Cβ), 122.54 (Cb), 62.52 (CH2), CF2CF2ϪSO2), Ϫ108.8 (m,
2-H, 3-H, 4-H), 4.42 (q, J ϭ 7.3 Hz, 2 H, 13.84 (CH3)
CH2), 1.41 (t, J ϭ 7 Hz, 3 H, CH3)
2 F, CF2ϪSO2), Ϫ81.2 (m, 3
F, CF3)
8.82 (s, 1 H, 4-H), 7.86 (t, J ϭ 8.5 Hz, 1 H, 156.34 (C-9), 155.50 (C-4), 153.49 (C-2), Ϫ126.1 (m, 2 F, CF2CF3),
7-H), 7.78 (d, J ϭ 8.1 Hz, 1 H, 5-H), 7.50 (d, 137.77 (C-5), 131.25 (C-7), 126.0 (C-6), 121.06 Ϫ121.4
(m,
2
F,
J ϭ 6.6 Hz, 1 H, 6-H), 7.49 (t, J ϭ 8.1 Hz, 1 (C-3), 117.46 (C8), 116.81 (C-10)
CF2CF2ϪSO2), Ϫ109.7 (m,
2 F, CF2ϪSO2), Ϫ81.0 (m, 3
F, CF3)
H, 8-H)
Eur. J. Org. Chem. 1999, 2969Ϫ2976
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R. Goumont, K. Magder, M. Tordeux, J. Marrot, F. Terrier, C. Wakselman
FULL PAPER
Scheme 5. DielsϪAlder reactions of cyclopentadiene with cyclic
unsaturated triflones and nonaflones
Adduct 6a was obtained as a yellow solid in 45% yield.
It was structurally analysed by X-ray crystallography, and
as shown by its ORTEP view (Figure 1), an endo cycload-
duct resulted from the condensation reaction, i.e., the aro-
matic ring and the ester group are located “under” the nor-
bornene skeleton.
Figure 1. ORTEP view of adduct 6a
The DielsϪAlder reaction was clearly indicated by the
spectral data (Table 3), especially by the disappearance of to appear diastereotopic. The signals of protons 7-H and
1
the signal from the deshielded proton Hα in the H-NMR 7Ј-H of the methylene bridge were two doublets [J(7-HϪ7Ј-
1
spectra. Concomitantly, in the H-NMR spectra of 6a, res- H) ϭ 9.6 Hz] at δ ϭ 2.46 and 1.63. Finally, three other
onances appeared for two ethylenic protons in the form of broad signals (δ ϭ 4.18, 3.88, 3.12) may be attributed to
two doublets of doublets (δ ϭ 6.67, 6.55) of an ABX3 sys- protons 1-H, 3-H and 4-H.
tem characteristic for an ethyl group. The asymmetric car-
Two-dimensional homonuclear chemical shift correlation
bon atom C-2 causes the two protons of the ester function (COSY) showed that there is a three-bond coupling be-
Table 3. NMR data for the adducts 6a؊d
Product
1H NMR
13C NMR
19F NMR
6a
7.08 (dd, J ϭ 5.2 Hz, 2 H, 2Ј-H), 6.94 (m, 3 164.16 (CO), 162.09 (d, J ϭ 247.0 Hz, C-4Ј), Ϫ70.0 (s,
3 F, SO2CF3),
H, 3Ј-H), 6.67 (dd, J ϭ 5.5 Hz, J ϭ 3.7 Hz, 138.81 (C-5), 138.67 (C-6), 134.26 (d, J ϭ 3.4 Ϫ115.4 (m, 1 F, C6H4ϪF)
1 H, 6-H), 6.55 (dd, J ϭ 5.5 Hz, J ϭ 3.3 Hz, Hz, C-1Ј), 130.55 (d, J ϭ 13.9 Hz, C-2Ј),
1 H, 5-H), 4.18 (d, J ϭ 2.9 Hz, 1 H, 3-H), 120.47 (q, J ϭ 332.3 Hz, CF3), 114.77 (d, J ϭ
3.88 (m, 1 H, 1-H), 3.86 (ABX3, 2 H, CH2), 20.9 Hz, C-3Ј), 86.61 (C-2), 62.75 (CH2),
3.12 (m, 1 H, 4-H), 2.46 (d, J ϭ 9.6 Hz, 1 H, 52.23 (C-3), 51.23 (C-1), 49.19 (C-4), 48.10
7-H), 1.63 (dt, J ϭ 9.6 Hz, J ϭ 1.9 Hz, 1 H, (C-7), 12.80 (CH3)
7Ј-H), 0.84 (t, J ϭ 7.3 Hz, 3 H, CH3)
6b
6c
7.25 (m, 3 H, 3Ј-H,4Ј-H), 7.10 (dd, 2 H, 2Ј- 164.29 (CO), 139.01 (C-2Ј), 138.61 (C-1Ј), Ϫ69.9 (s, SO2CF3)
H), 6.74 (dd, J ϭ 5.3 Hz, J ϭ 3.3 Hz, 1 H, 6- 138.40 (C-4Ј), 128.96 (C-3Ј), 127.94 (C-5),
H), 6.58 (dd, J ϭ 5.3 Hz, J ϭ 3.0 Hz, 1 H, 5- 127.38 (C-6), 120.52 (q, J ϭ 332.3 Hz, CF3),
H), 4.17 (d, J ϭ 2.6 Hz, 1 H, 3-H), 3.88 (m, 87.06 (C-2), 62.62 (CH2), 53.59 (C-3), 51.25
1 H, 1-H), 3.82 (ABX3, J ϭ 7.2 Hz, 2 H, (C-1), 49.34 (C-4), 48.13 (C-7), 12.62 (CH3)
CH2), 3.14 (m, 1 H, 4-H), 2.48 (d, J ϭ 9.5 Hz,
1 H, 7-H), 1.63 (dt, J ϭ 9.5 Hz, J ϭ 1.7 Hz,
1 H, 7Ј-H), 0.75 (t, J ϭ 7.2 Hz, 3 H, CH3)
7.34Ϫ7.25 (m, 5 H, 2Ј-H, 3Ј-H,4Ј-H), 6.54 163.81 (CO), 128.58 (C-2Ј), 136.87 (C-1Ј), Ϫ71.1 (s, SO2CF3)
(dd, J ϭ 5.5 Hz, J ϭ 2.9 Hz, 1 H, 6-H), 6.53 131.58 (Cb), 128.78 (Ca), 127.55 (C-4Ј),
(d, J ϭ 15.3 Hz, 1 H, Hb), 6.41 (dd, J ϭ 5.5 126.29 (C-3Ј), 140.12 (C-5), 137.67 (C-6),
Hz, J ϭ 3.3 Hz, 1 H, 5-H), 5.74 (dd, J ϭ 15.3 120.88 (q, J ϭ 331.4 Hz, CF3), 83.12 (C-2),
Hz, J ϭ 9.8 Hz, 1 H, Ha), 4.20 (ABX3, 2 H, 62.82 (CH2), 51.91 (C-3), 50.86 (C-1), 49.40
CH2), 3.91 (m, 1 H, 1-H), 3.84 (dd, J ϭ 9.5 (C-4), 46.28 (C-7), 13.61 (CH3)
Hz, J ϭ 2.6 Hz, 1 H, 3-H), 3.06 (m, 1 H, 4-
H), 2.36 (d, J ϭ 9.5 Hz, 1 H, 7-H), 1.58 (dt,
J ϭ 9.5 Hz, J ϭ 1.7 Hz, 1 H, 7Ј-H), 1.21 (t,
J ϭ 7.2 Hz, 3 H, CH3)
6d
7.17Ϫ7.34 (m, 3 H, 2Ј-H, 3Ј-H,4Ј-H), 6.99 (d, 159.59 (C-9), 153.59 (C-1Ј), 141.15 (C-5), Ϫ71.4 (s, SO2CF3)
J ϭ 8.1 Hz, 1 H, 5Ј-H), 6.30 (dd, J ϭ 5.5 Hz, 136.34 (C-6), 129.10 (C-2Ј), 128.19 (C-4Ј),
J ϭ 3.3 Hz, 1 H, 6-H), 6.22 (dd, J ϭ 5.5 Hz, 125.46 (C-3Ј), 120.04 (q, J ϭ 320.1 Hz, CF3),
J ϭ 2.9 Hz, 1 H, 5-H), 4.30 (d, J ϭ 3.3 Hz, 1 119.65 (C-6Ј), 117.17 (C-5Ј), 74.78 (C-2),
H, 3-H), 4.21 (s, 1 H, 1-H), 3.52 (s, 1 H, 4- 53.76 (C-1), 51.23 (C-4), 45.92 (C-7), 44.44
H), 2.33 (d, J ϭ 9.9 Hz, 1 H, 7-H), 1.70 (d, (C-3)
J ϭ 9.6 Hz, 1 H, 7Ј-H)
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Synthesis and Cycloaddition Reactions of Ethyl 3-Aryl-2-(perfluoroalkanesulfonyl)propenoates
FULL PAPER
˚
˚
˚
tween the two ethylenic protons and the signals at δ ϭ 3.88 d[H(3)ϪH(2Ј)] ϭ 2.225 A, d[H(7)ϪH(7Ј)] ϭ 1.684 A and
and 3.12, which are obviously the two bridgehead protons d[H(5)ϪH(2Ј)] ϭ 2.593 A. The resonances of the carbon
1-H and 4-H. The signal at δ ϭ 4.18, corresponding to 3- atoms (Table 3) were assigned unambiguously on the basis
H, exhibited a three-bond coupling response with the signal of two NMR experiments, J modulation and two-dimen-
at δ ϭ 3.12 which may be attributed to 4-H. Finally, the sional heteronuclear chemical shift correlation (HETCOR).
chemical shifts of the two ethylenic protons could be readily IR data and MS experiments[24] also confirmed that vinyl
assigned to be δ(6-H) ϭ 6.67 and δ(5-H) ϭ 6.55. NOE triflone 4a underwent addition with one equiv. of cyclopen-
experiments allowed us to confirm the endo stereochemistry tadiene.
and to discriminate between the two bridge protons 7-H
and 7Ј-H. Saturation of 3-H showed a positive response
1
The H- and 13C-NMR data of 6b resemble those of 6a.
with 2Ј-H (δ ϭ 7.07), 4-H (δ ϭ 3.12) and 7-H (δ ϭ 2.46). Assignments were made by comparison and only the com-
Saturation of 7-H gave two positive NOEs, with 7Ј-H (δ ϭ plex second-order signals of the protons of the aromatic
1.63) and 3-H (δ ϭ 4.18); saturation of 2Ј-H resulted in ring could not be accurately assigned. NOE experiments
responses from 5-H (δ ϭ 6.55) and 3-H (δ ϭ 4.18) (Figure confirmed the endo stereochemistry: Saturation of 3-H re-
2). These NOE results are in agreement with the distances sulted in a positive response from 4-H (δ ϭ 3.14) and 7-H
between these atoms measured by X-ray crystallography: (δ ϭ 2.48); saturation of 5-H caused a positive NOE with
˚
˚
d[H(7)ϪH(3)] ϭ 2.409 A, d[H(3)ϪH(4)] ϭ 2.385 A, 2Ј-H (δ ϭ 7.10).
Figure 2. NOE spectra of adduct 6a in CDCl3
Eur. J. Org. Chem. 1999, 2969Ϫ2976
2973

R. Goumont, K. Magder, M. Tordeux, J. Marrot, F. Terrier, C. Wakselman
FULL PAPER
Cycloadduct 6c was obtained as an oil in quantitative
Comparison of the cyclopentadiene adducts 6a؊d and
1
yield upon treatment of 4c with cyclopentadiene. The H- 9a؊d showed that the triflone derivatives are clearly more
NMR spectra appeared to be similar to those of 6a and 6b, stable than the nonaflones ones. This higher stability al-
and contained signals for two new ethylenic protons Ha lowed us to study the structure of 6a in great detail by
(δ ϭ 5.74) and Hb (δ ϭ 6.53) as a doublet of doublets [3J(3- NMR and X-ray analysis. Both methods showed that Diel-
HϪHa) ϭ 9.8 Hz and 3J(HaϪHb) ϭ 15.2 Hz] and a doublet sϪAlder cycloaddition resulted in endo isomers of 6a؊d.
[3J(HaϪHb) ϭ 15.2 Hz], respectively.
The NMR data of compounds 6a؊d and 9a؊d are also
Treatment of 4d with cyclopentadiene 5 led, after purifi- very similar. It can therefore be concluded that the stereo-
cation, to a 50% yield of adduct 6d. Detailed NMR analysis chemistry of the nonaflones derivatives 9a؊d is also endo,
in CDCl3 solution (Table 3), including NOE experiments, whereas they were previously considered to be exo cycload-
identified the stereochemistry as endo. Saturation of 3-H ducts.[15] Addition of (E)-4a؊d or (E)-8a؊d to cyclopen-
resulted in a positive NOE with the bridge proton 7-H (δ ϭ tadiene involves secondary orbital interactions with the aro-
2.33) and saturation of 2Ј-H gave rise to two positive re- matic ring and the ester group. That no trace of the exo
sponses, with 3-H (δ ϭ 4.30) and 4-H (δ ϭ 3.52).
diastereoisomer could be detected in the present study may
be due to the larger steric constraints of the nonafluorobut-
anesulfonyl or trifluoromethanesulfonyl group in the exo
approach.
b. Reaction of Nonaflones 8a؊d with Cyclopentadiene
As described by Hanack,[15] vinyl nonaflones reacted
with dienes like cyclopentadiene to give cycloadducts 9a؊d
(Schemes 4 and 5). These adducts[15] were obtained in good
yields, but they appeared to be somewhat less stable than
Conclusion
We have shown that vinyl triflones may be prepared easily
6a؊d. However, their spectral data (Table 4) agree well with and in good yields by the Knoevenagel condensation reac-
the data collected for compounds 6a؊d. NOE experiments tion. These esters may be dealkylated/decarboxylated by an-
were carried out, showing that the stereochemistry of ad- hydrous lithium iodide in dimethylformamide to produce a
ducts 8a؊d is endo. Moreover, saturation of 3-H showed in new series of vinyl triflones. Alternatively, these compounds
all cases a positive NOE with the bridge proton 7-H.
may be used in the Michael condensation reaction[1] be-
Table 4. NMR data for the adducts 9a؊d
Product
1H NMR
13C NMR
19F NMR
9a
7.10 (dd, J ϭ 7.9 Hz, J ϭ 5.3 Hz, 2 H, 2Ј-H), 164.12 (CO), 162.11 (d, J ϭ 246.9 Hz, C-4Ј), Ϫ126.1 (m, 2 F, CF2CF3),
6.95 (“t”, J ϭ 8.7 Hz, 2 H, 3Ј-H), 6.68 (dd, 138.88 (C-6), 138.65 (C-5), 134.24 (d, J ϭ 3.3 Ϫ121.3 (m, F,
2
J ϭ 5.3 Hz, J ϭ 3.2 Hz 1 H, 6-H), 6.54 (dd, Hz, C-1Ј), 130.61 (d, J ϭ 8.2 Hz, C-2Ј), 114.78 CF2CF2ϪSO2), Ϫ115.4 (s, 1
J ϭ 5.3 Hz, J ϭ 3.4 Hz, 1 H, 5-H), 4.18 (m, (d, J ϭ 21.3 Hz, C-3Ј), 89.23 (C-2), 62.67 F, C6H4ϪF), Ϫ105.3 (m, 2
1 H, 3-H), 3.87 (m, 1 H, 1-H), 3.86 (ABX3, 2 (CH2), 53.0 (C-3), 51.66 (C-1), 48.95 (C-4), F, CF2SO2), Ϫ81.1 (m, 3 F,
H, J ϭ 10.8 Hz, CH2), 3.10 (m, 1 H, 4-H), 48.20 (C-7), 12.83 (CH3)
2.48 (d, J ϭ 9.5 Hz, 1 H, 7-H), 1.65 (d, J ϭ
9.5 Hz, 1 H, 7Ј-H), 0.85 (t, J ϭ 6.9 Hz, 3
H, CH3)
CF3)
9b
9c
7.31 (m 1H, 4Ј-H), 7.26 (m, 2 H, 3Ј-H), 7.13 164.27 (CO), 138.87 (C-2Ј), 138.59 (C-4Ј), Ϫ126.1 (m, 2 F, CF2CF3),
(m, 2 H, 2Ј-H), 6.69 (m, 1 H, 6-H), 6.56 (m, 138.52 (C-1Ј), 129.01 (C-3Ј), 127.94 (C-5), Ϫ121.4
1 H, 5-H), 4.17 (m, 1 H, 3-H), 3.89 (m, 1 H, 127.38 (C-6), 89.68 (C-2), 62.55 (CH2), 53.81 CF2CF2ϪSO2), Ϫ103.3 (m,
1-H), 3.8 (ABX3, 2 H, J ϭ 11.8 Hz, CH2), (C-3), 51.70 (C-1), 49.06 (C-4), 48.24 (C-7), 2 F, CF2ϪSO2), Ϫ81.1 (m, 3
(m,
2
F,
3.13 (m, 1 H, 4-H), 2.5 (d, J ϭ 9.6 Hz, 1 H, 12.67 (CH3)
7-H), 1.65 (d, J ϭ 9.5 Hz, 1 H, 7Ј-H), 0.77 (t,
J ϭ 7.2 Hz, 3 H, CH3)
F, CF3)
7.33Ϫ7.30 (m, 5 H, 2Ј-H, 3Ј-H, 4Ј-H), 6.56 163.66 (CO), 140.57 (C-5), 137.38 (C-6), Ϫ126.2 (m, 2 F, CF2CF3),
(dd, J ϭ 5.6 Hz, J ϭ 3.3 Hz, 1 H, 5-H), 6.53 136.94 (C-1Ј), 132.24 (Cb), 129.22 (Ca), 128.55 Ϫ121.6
(m,
2
F,
(d, J ϭ 15.4 Hz, 1 H, Hb), 6.39 (d, J ϭ 5.6 (C-2Ј), 127.48 (C-4Ј), 126.27 (C-3Ј), 85.52 (C- CF2CF2ϪSO2), Ϫ108.9 (m,
Hz, 1 H, 6-H), 5.78 (dd, J ϭ 15.8 Hz, J ϭ 9.8 2), 62.7 (CH2), 52.01 (C-1), 51.58 (C-4), 49.47 2 F, CF2ϪSO2), Ϫ81.9 (m, 3
Hz, 1H, Ha), 4.20 (ABX3, J ϭ 11.2 Hz, 2 H, (C-3), 46.22 (C-7), 13.63 (CH3)
CH2), 3.96 (m, 1 H, 1-H), 3.85 (d, J ϭ 9.8 Hz,
F, CF3)
1 H, 3-H), 3.06 (m, 1 H, 4-H), 2.36 (d, J ϭ
9.8 Hz, 1 H, 7-H), 1.57 (dd, J ϭ 9.5 Hz, J ϭ 1
Hz, 1 H, 7Ј-H), 1.22 (t, J ϭ 7.2 Hz, 3 H, CH3)
9d
7.32 (dd, J ϭ 7.6 Hz, J ϭ 1 Hz, 1 H, 2Ј-H), 159.12 (CO), 148.61 (C-1Ј), 141.75 (C-5), Ϫ126.3 (m, 2 F, CF2CF3),
7.26 (t, J ϭ 7.7 Hz, 1 H, 4Ј-H), 7.19 (t, J ϭ 135.93 (C-6), 129.01 (C-2Ј), 128.03 (C-4Ј), Ϫ121.3
(m,
2
F,
7.6 Hz, 1 H, 3Ј-H), 6.97 (dd, J ϭ 8.1 Hz, J ϭ 125.42 (C-3Ј), 119.90 (C-6Ј), 117.02 (C-5Ј), CF2CF2ϪSO2), Ϫ107.1 (m,
1.5 Hz, 1 H, 5Ј-H), 6.28 (dd, J ϭ 5.6 Hz, J ϭ 75.80 (C-2), 54.93 (C-1), 51.81 (C-4), 46.12 2 F, CF2ϪSO2), Ϫ81.2 (m, 3
2.9 Hz, 1 H, 6-H), 6.23 (dd, J ϭ 5.6 Hz, J ϭ (C-7), 44.74 (C-3)
3 Hz, 1 H, 5-H), 4.30 (m, 1 H, 1-H), 4.27 (d,
J ϭ 3.6 Hz, 1 H, 3-H), 3.51 (m, 1 H, 4-H),
2.33 (d, J ϭ 9.8 Hz, 1 H, 7-H), 1.66 (dt, J ϭ
9.8 Hz, J ϭ 1.4 Hz, 1 H, 7Ј-H)
F, CF3)
2974
Eur. J. Org. Chem. 1999, 2969Ϫ2976

Synthesis and Cycloaddition Reactions of Ethyl 3-Aryl-2-(perfluoroalkanesulfonyl)propenoates
FULL PAPER
cause conjugate additions to vinyl triflones are favourable Table 5. Crystal and structure refinement data for the adduct 6a
reactions, proceeding with a variety of common nucleo-
philes under mild conditions. In this paper, it was shown
6a
that vinyl triflones are active dienophiles in DielsϪAlder
Empirical formula
Molecular mass
Crystal system
Space group
Z
C17H16F4O4S
392.36
cycloaddition reactions. This reaction occurred highly ster-
eoselectively and led to the formation of only the endo iso-
mer.
monoclinic
P21/c
4
˚
a [A]
11.0910(3)
9.3056(3)
16.8955(5)
98.9070(10)
1722.73(9)
0.18 ϫ 0.54 ϫ 0.78
296(2)
˚
b [A]
˚
c [A]
Experimental Section
β [°]
3
˚
V [A ]
Melting points were determined with a Reichert microscope (hot-
stage type) and are uncorrected. Ϫ 1H-, 13C- and 19F-NMR spectra
were recorded with a Bruker AC300 instrument; internal standards
were tetramethylsilane (TMS) for 1H and 13C NMR, and CFCl3
for 19F NMR; 1H-, 13C- and 19F-NMR spectra were recorded at
300 MHz, 75.5 MHz and 282.3 MHz, respectively. Chemical shifts
are reported in parts per million (ppm) and coupling constants J in
Hertz (Hz). Ϫ Column chromatography was performed with Merck
silica gel (70Ϫ230 mesh) using various ratios of ethyl acetate/pen-
tane as eluent. TLC was carried out on Merck 60F-254 precoated
silica gel plates (0.25 mm). Ϫ Sodium trifluoromethanesulfinate
(1),[21] ethyl (trifluoromethanesulfonyl)acetate (2),[20] ethyl (non-
afluorobutanesulfonyl)acetate[19][26] (7) were prepared according to
standard procedures. Cyclopentadiene (5) was obtained by heating
bicyclopentadiene and was used without further purification. Alde-
hydes 3a؊d were freshly distilled before use. When needed, reac-
tions were carried out under argon and dry conditions.
Crystal size [mm]
T [K]
Goodness-of-fit on F2
1.059
sorption by the SADABS[28] program specific to the CCD detector.
The structure was solved by direct methods with SHELX-TL[29]
and the hydrogen atoms were located by the use of geometrical
constraints. Refinement (300 parameters) was performed by full-
matrix least-squares analysis of SHELX-TL up to R1(Fo) ϭ 0.0503
and wR2(Fo2) ϭ 0.1063. Crystallographic data for the structure 6a
reported in this paper were deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication no. CCDC-
114256. Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. [Fax:
(internat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
General Procedures
Preparation of Ethyl 3-Aryl-2-(trifluoromethane)sulfonylpropenoates
4a؊d and Ethyl 3-Aryl-2-(nonafluorobutane)sulfonylpropenoates
8a؊d: 1 equiv. of ethyl (trifluoromethanesulfonyl)acetate (2) or
ethyl (nonafluorobutanesulfonyl)acetate (7) and 1 equiv. of alde-
hyde 3a؊d were dissolved in toluene (20 mL). Then, piperidine
(0.05 mL) and glacial acetic acid (0.1 mL) were added. The mixture
was refluxed for 3Ϫ4 h with a water trap (DeanϪStark), until no
further water separated. The solvent was removed under reduced
pressure and the residue was taken up in Et2O. The Et2O was
washed with HCl (50 mL, 5%), then washed several times with
water, followed by drying (MgSO4). The solvent was evaporated
and the residue was purified by recrystallization from pentane/ethyl
acetate or by column chromatography.
Acknowledgments
This work enters partly in the frame of the European TMR pro-
gramme ERB FMRX-CT97.0120, entitled: “Fluorine As a Unique
Tool for Engineering Molecular Properties”.
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´
R. Goumont, M. Tordeux, C. Beguin, M. Gromova, F. Terrier,
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oil; 6d, 50%, oil; 9a, 38%, oil; 9b, 70%, oil; 9c, 50%, oil; 9d, 40%,
150Ϫ152°C.
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with a Siemens SMART three-circle diffractometer equipped with
a two-dimensional CCD detector. The exposure time was 10 s per
frame. A total of 11425 reflections corresponding to the whole re-
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[19]
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ϭ
0.0214) with I > 2σ(I). The data (Table 5) were corrected for ab-
Eur. J. Org. Chem. 1999, 2969Ϫ2976
2975

R. Goumont, K. Magder, M. Tordeux, J. Marrot, F. Terrier, C. Wakselman
FULL PAPER
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Details on the IR and MS data, together with the various data
obtained for our compounds, are available as Supporting Infor-
mation (Tables S1ϪS3).
R. J. Koshar, R. A. Mitsch, J. Org. Chem. 1973, 38, 3358.
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Received March 15, 1999
[23]
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[29]
[O99164]
2976
Eur. J. Org. Chem. 1999, 2969Ϫ2976