Toward the synthesis of novel fluorinated building blocks: 3,4-difluorothiophene-1,1-dioxide

Article abstract of DOI:10.1016/S0022-1139(98)00252-8

Addition of elemental fluorine to 2,5-dihydrothiophene-1,1-dioxide (4) provided a mixture of isomeric 3,4-difluoro-2,3,4,5-tetrahydrothiophene-1,1-dioxides (5) in moderate yield. Photochemical chlorination of each of these isomers gave the same product mixture consisting mainly of trans-3-chloro-3,4-difluoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide (9a) and trans-3,4-dichloro-3,4-difluoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide (11b). Dehydrohalogenation of the former gave 3,4-difluoro-4,5-dihydrothiophene-1,1-dioxide (12) as the main product, whereas dehydrohalogenation of the latter gave 3,4-difluorothiophene-1,1-dioxide (3) as the main product.

Full text of DOI:10.1016/S0022-1139(98)00252-8

Journal of Fluorine Chemistry 93 (1999) 27±31
Toward the synthesis of novel ¯uorinated building blocks:
3,4-di¯uorothiophene-1,1-dioxide
Ireneusz Nowak*, Lillian M. Rogers, Robin D. Rogers, Joseph S. Thrashe1
Department of Chemistry, The University of Alabama, P.O. Box 870336, Tuscaloosa, AL 35487-0336, USA
Received 13 May 1998; accepted 29 June 1998
Abstract
Addition of elemental ¯uorine to 2,5-dihydrothiophene-1,1-dioxide (4) provided a mixture of isomeric 3,4-di¯uoro-2,3,4,5-
tetrahydrothiophene-1,1-dioxides (5) in moderate yield. Photochemical chlorination of each of these isomers gave the same product
mixture consisting mainly of trans-3-chloro-3,4-di¯uoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide (9a) and trans-3,4-dichloro-3,4-di¯uoro-
2,3,4,5-tetrahydrothiophene-1,1-dioxide (11b). Dehydrohalogenation of the former gave 3,4-di¯uoro-4,5-dihydrothiophene-1,1-dioxide
(12) as the main product, whereas dehydrohalogenation of the latter gave 3,4-di¯uorothiophene-1,1-dioxide (3) as the main product.
# 1999 Elsevier Science S.A. All rights reserved.
Keywords: Chlorination; Dehydrohalogenation; Di¯uorothiophene dioxide; Fluorodiene; Elemental ¯uorine; Fluorination
1. Introduction
possible to saturate smoothly the double bond with elemen-
tal ¯uorine. Thus, ¯uorine diluted with nitrogen was slowly
passed through a vigorously stirred, aqueous solution of 2,5-
dihydrothiophene-1,1-dioxide (4) at ambient temperature.
Since the use of water caused foaming and the formation of a
®lm on the surface of the solution, a mixture of water and
acetonitrile (4:1) was used instead. The reaction was halted
after the complete consumption of the starting material,
Although the parent thiophene dioxide 1 is an unstable
material [1±3], more substituted derivatives can be isolated
as stable, crystalline compounds. Most of the chemistry of
substituted thiophene dioxides has been focused on their use
in cycloaddition reactions. A great range of such adducts
was prepared [4±8] most notably by the Raasch [4] and
Nakayama groups [7,8].
1
which was monitored by H NMR spectroscopy. A variety
In a recent paper, one of us (I.N.) described the synthesis
and reactivity of 3-chloro-4-¯uorothiophene-1,1-dioxide (2)
[9]. As a part of our continuing interest in the synthesis of
¯uorinated thiophene dioxides which may have potential as
useful ¯uorinated building blocks, we describe herein the
synthesis of 3,4-di¯uorothiophene-1,1-dioxide (3).
of products was isolated from the reaction mixture; 3-¯uoro-
2,3-dihydrothiophene-1,1-dioxide (6) [10] and 3,4-epoxy-
2,3,4,5-tetrahydrothiophene-1,1-dioxide (7) [11] were
formed along with the expected cis- and trans-di¯uoroad-
ducts 5a and 5b, respectively (see Scheme 1). In an attempt
to minimize the formation of epoxide 7, a ¯uorination was
carried out in acetonitrile at 308C, but the presence of
considerable amounts of compound 7 was again detected
spectroscopically.
2. Results and discussion
The assignment of the cis structure to adduct 5a was based
on a single-crystal X-ray analysis 2. As can be seen in Fig. 1,
the ®ve-membered ring is distorted considerably from pla-
narity with the C±F bonds being in a synclinal (gauche)
The compound 2,5-dihydrothiophene-1,1-dioxide (4 or 3-
sulfolene) served as a cheap and readily accessible starting
material for the syntheses reported herein. Since the methy-
lene hydrogen atoms adjacent to a sulfonyl group are
reluctant to be involved in a radical process, it appeared
2Crystal data for 5a, C4H6F2O2S: M ˆ 156.15; triclinic, space group
Ê
P1; a ˆ 5.6334(8), b ˆ 6.3970(9), c ˆ 9.3893(13) A, ꢀ ˆ 82.278(3),
3
Ê
ꢁ ˆ 78. 067(3), ꢂ ˆ 65. 062(2)8, V ˆ 299. 76(7) A ; Z ˆ 2;
3
1
*Corresponding authors.
1Also an corresponding co author.
ꢃcalc ˆ 1.730 Mg m
wR2 ˆ 0.162.
;
ꢄ(MoKꢀ) ˆ 0.500 mm
;
R1 ˆ 0.065 and
0022-1139/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
P I I : S 0 0 2 2 - 1 1 3 9 ( 9 8 ) 0 0 2 5 2 - 8

28
I. Nowak et al. / Journal of Fluorine Chemistry 93 (1999) 27±31
Scheme 1.
with sulfur tetra¯uoride [10]. Although Yagupol'skii and
co-workers did not assign the stereochemistry (cis or trans)
of their product, the reaction of epoxides with DAST (and
thus presumably with SF4) is reported to give vicinal cis-
di¯uorides [12]. In addition, Yagupol'skii reported a melting
point of 1298C for 5a versus 131±1338C found herein, both
of which are in stark contrast to the 89±918C melting point
found for the trans-isomer 5b.
Photochlorination of either the cis or trans isomer of 5 in
carbon tetrachloride, after 7 h, gave the same mixture of
mono and dichloro products. This result strongly suggests
that the same intermediate, presumably radical 8 is involved
in the reaction pathway. After removal of the solvent and
subsequent puri®cation over a silica gel column, compounds
9 and 11 were isolated as 9a : 9b ˆ 30:10% and 11a :
11b ˆ 5:30% mixtures, respectively (see Scheme 2). Pure
isomers 9a and 11b were isolated after several additional
recrystallizations of the obtained fractions. Reasonably pure
(85%) isomer 9b was recovered unchanged after reacting a
mixture of isomers 9 with triethylamine (see Scheme 3); this
reaction also resulted in the formation of 3,4-di¯uoro-4,5-
Fig. 1. ORTEP diagram of 5a. Displacement ellipsoids are drawn at 50%
probability level and hydrogen atoms have been given arbitrarily reduced
radii for clarity.
arrangement. This assignment is also consistent with the
previous work of Yagupol'skii et al. where compound 5a
was prepared from the ring opening reaction of epoxide 7
Scheme 2.
Scheme 3.

I. Nowak et al. / Journal of Fluorine Chemistry 93 (1999) 27±31
29
Fig. 2. ORTEP diagram of 11b. Displacement ellipsoids are drawn at 50%
probability level and hydrogen atoms have been given arbitrarily reduced
radii for clarity.
Fig. 3. ORTEP diagram of 9a. Displacement ellipsoids are drawn at 50%
probability level and hydrogen atoms have been given arbitrarily reduced
radii for clarity.
Scheme 4.
dihydrothiophene-1,1-dioxide (12) in 53% yield. Irradiation
of the sulfones 5 for a longer period of time (24 h) was
necessary to complete the chlorination, thereby giving
dichlorosulfones 11a and 11b in a total yield of 68% and
a ratio of 1:5, respectively.
A well-established method for the generation of thio-
phene dioxide and its derivatives involves the double dehy-
drohalogenation of dihalothiolane dioxides [13,14]. In the
case of compounds 11a and 11b the possibility of obtaining
a mixture of both ¯uorinated as well as chlorinated products
was quite obvious. However, our previous experience with
selective elimination of hydrogen chloride in preference to
hydrogen ¯uoride [9] gave us some hope that such a
selectivity might be obtained again. Indeed, we have found
that the addition of triethylamine to a diethyl ether solution
of 11b gave the expected 3,4-di¯uorothiophene-1,1-dioxide
(3) and 3-chloro-4-¯uorothiophene-1,1-dioxide (2) [9] as a
minor product, in a ratio of 4:1 (Scheme 4). The reaction
proceeds smoothly at room temperature within minutes. The
elimination can also be carried out in other solvents like
ethyl acetate, benzene or tetrahydrofuran, with the ratio of
elimination products 3 and 2 being unchanged. This dehy-
drohalogenation reaction was also carried out on a mixture
of isomers 11a and 11b (both analytical and laboratory
scales), and no discernible difference in the ratio of products
3 and 2 was observed versus starting with just isomer 11b. It
is remarkable that the dehydrohalogenation proceeds with
high chemoselectivity producing di¯uorinated compound 3
as a main product.
Due to uncertainty in the stereochemical assignments of
compounds 9 and 11 based solely on the NMR data, the
stereochemistry of the dominating isomers 9a and 11b was
established by single-crystal X-ray analysis (see Figs. 2 and
3). Compound 11b (Fig. 2) is the trans isomer with C±F
3
bonds directed to opposite sides of the ring . In contrast,
X-ray analysis for the major isomer 9a (Fig. 3) revealed that
a cis arrangement of ¯uorine atoms is present 4. The change
of stereochemistry at the carbon atom after the introduction
of second chlorine can be attributed to the existence of
radical intermediate 10. Once formed, radical 10 can com-
bine with a chlorine atom under formation of the more stable
trans isomer 11b (see Scheme 3).
3Crystal data for 11b, C4H4Cl2F2O2S: M ˆ 225.03; monoclinic, space
Ê
group P21/c; a ˆ 11.839(2), b ˆ 5.9558(8), c ˆ 10.9294(14) A,
Ê 3
ꢁ ˆ 99.404(2)8, V ˆ 760.3(2) A ; Z ˆ 4; ꢃcalc ˆ 1.966 Mg m 3; ꢄ(Mo
Ka) ˆ 1.107 mm 1; R1 ˆ 0.057 and wR2 ˆ 0.141.
4Crystal data for 9a, C4H5ClF2O2S: M ˆ 190.59; monoclinic, space
Ê
group P21/c; a ˆ 5.7182(2), b ˆ 10.9121(4), c ˆ 10.8784(3) A,
Ê 3
The considerable volatility of 3,4-di¯uorothiophene-1,1-
dioxide (3) makes it possible to isolate it simply by sub-
ꢁ ˆ 95.910(2)8, V ˆ 675.18(4) A ; Z ˆ 4; ꢃcalc ˆ 1.875 Mg m 3; ꢄ(Mo
Ka) ˆ 0.845 mm 1; R1 ˆ 0.056 and wR2 ˆ 0.134.

30
I. Nowak et al. / Journal of Fluorine Chemistry 93 (1999) 27±31
limation under reduced pressure followed by recrystalliza-
tion. The structure of compound 3 was con®rmed by the
presence of a single vinylic hydrogen signal in the 1H NMR
spectrum and a single vinylic ¯uorine signal in the 19F NMR
spectrum. The mass spectrum exhibited strong peaks for the
2H, CHF), 3.60 (m, 4H, CH2); 19F NMR (470 MHz, CDCl3)
ꢅ: 199.3 (m). GC-MS (m/z) [relative intensity, ion]: 156
‡
‡
‡
[3%, M ], 77 [15, (C3H3F2) ], 46 [100, (C2H3F) ].
Trans-3,4-di¯uoro-2,3,4,5-tetrahydrothiophene-1,1-dio-
xide (5b): m.p. 89±918C. Anal. Found: C, 30.90; H, 3.99; F,
21.86; S, 20.54%. C4H6F2SO2 requires: C, 30.77; H, 3.87; F,
24.33; S, 20.54%. 1H NMR (500 MHz, CDCl3) ꢅ: 5.45 (m,
2H, CHF), 3.55 (m, 4H, CH2); 19F NMR (470 MHz, CDCl3)
ꢅ: 186.8 (m). GC-MS (m/z) [relative intensity, ion]: 156
‡
molecular ion as well as the ions (M±CHO) and (M±CHO±
‡
F) , which are also characteristic for 3-chloro-4-¯uorothio-
phene-1,1-dioxide (2) [9].
‡
‡
‡
[3%, M ], 77 [15, (C3H3F2) ], 46 [100, (C2H3F) ].
3-Fluoro-2,3-dihydrothiophene-1,1-dioxide (6): m.p. 66±
688C ([10], 68±698C). Anal. Found: C, 35.36; H, 3.82; F,
13.36; S, 23.76%. C4H5FSO2 requires: C, 35.29; H, 3.70; F,
13.95; S, 23.55%. 1H NMR (500 MHz, CDCl3) ꢅ: 6.85 (ddd,
1H vinylic, 3JHH ˆ 6.8 Hz, 4JHF ˆ 2.8 Hz, 4JHH ˆ 0.9 Hz);
3. Experimental
Melting points were determined in open capillaries and
are uncorrected. 1H, 13C, and 19F NMR spectra were
recorded in CDCl3 or DMSO, with Bruker AM360 and
AM500 spectrometers at the frequency indicated. Chemical
shifts are quoted in ppm from internal TMS for 1H (positive
down®eld; same for 13C) and from internal CFCl3 for 19F
(positive down®eld). Preliminary 13C NMR spectra were
taken to assure consistency with the structures proposed
herein, but high quality spectra were not recorded; this
may be the subject of a future study. GC-MS analyses
were performed with a Hewlett-Packard 5890 GC-MS
(70 eV) using a 30 m capillary column coated with HP1
oil. Column chromatography was carried out on 70±
230 mesh silica gel.
Crystals of compounds 5a, 9a, and 11b were mounted on
®bers, transferred to the goniometer, and cooled to 1008C
using a stream of nitrogen gas. Crystallographic data were
collected using a Siemens CCD area detector-equipped
diffractometer, and all calculations were performed using
the SHELXTL suite of programs [15]. All crystallographic
data, including structure factor tables, have been submitted
as supplementary information and can be obtained by
following the instructions on the current masthead page
of this journal.
3
4
6.81 (ddd, 1H vinylic, JHH ˆ 6.8 Hz, JHF ˆ 4.5 Hz,
3JHH ˆ 3.0 Hz); 5.81 (ddddd, 1H, CHF, JHF ˆ 50.3 Hz,
2
3JHH ˆ 7.3 Hz, JHH ˆ 3.0 Hz, JHH ˆ 2.8 Hz, JHH
ˆ
ˆ
3
3
4
2
3
0.9 Hz); 3.64 (ddd, 1H, CH2, JHH ˆ 14.4 Hz, JHF
12.1 Hz, 3JHH ˆ 7.3 Hz); 3.36 (ddd, 1H, CH2,
3JHF ˆ 22.8 Hz, JHH ˆ 14.4 Hz, JHH ˆ 2.8 Hz). 19F
2
3
NMR (470 MHz, CDCl3) ꢅ:
3
171.5 (ddddd, CHF,
4
2JHF ˆ 50.3 Hz, JHF ˆ 22.8 Hz, JHF ˆ 12.1 Hz, JHF
ˆ
3
4
4.5 Hz, JHF ˆ 2.8 Hz). GC-MS (m/z) [relative intensity,
‡
‡
ion]: 136 [10%, M ], 107 [20, (M±CHO) ], 64 [45,
‡
‡
SO2 ], 46 [100, C2H3F ].
3,4-Epoxy-1,2,3,4-tetrahydrothiophene-1,1-dioxide (7):
1
m.p. 159±1618C ([11], 157±1598C). H NMR (360 MHz,
CDCl3) ꢅ: 3.92 (m, 2H), 3.65 and 3.46 (AB pattern, 4H,
2JAB ˆ 14.4 Hz). GC-MS (m/z)) [relative intensity, ion]: 70
‡
‡
‡
[30%, (M±SO2) ], 64 [20, (SO2) ], 42 [100, (C2H2O) ].
3.2. Photochemical chlorination of 3,4-difluoro-2,3,4,5-
tetrahydrothiophene-1,1-dioxides (5)
Method A: A 3 l, four-necked ¯ask equipped with a re¯ux
condenser (protected from atmospheric moisture with a
bubbler containing concentrated sulfuric acid), a Te¯on-
coated stirring bar, and a chlorine gas inlet valve, was
charged with either di¯uorosulfone 5a or 5b (8 g,
0.05 mol) and carbon tetrachloride (1500 ml). Elemental
chlorine was slowly passed through this vigorously stirred
mixture. The resulting solution was subsequently irradiated
with a Hanau Heraeus (15 W) immersion lamp (UV) for 7 h
while monitoring the progress of the reaction by GC-MS.
The solvent was removed on a rotary evaporator, and the
residue was separated by column chromatography (100 g
silica, toluene as eluent). Fractions containing mixtures of
9a, 9b and 11a, 11b were collected. Analytically pure
samples of 9a and 11b were obtained after recrystallization
of the collected fractions from methanol. Yields: 30% and
30%, respectively.
3.1. Reaction of 2,5-dihydrothiophene-1,1-dioxide (4) with
fluorine
Elemental ¯uorine (ca. 30 g, 0.79 mol) diluted with
nitrogen (1:3 ratio) was passed very slowly through a
vigorously stirred solution of 2,5-dihydrothiophene-1,1-
dioxide (4) (30 g, 0.25 mol) in a mixture with water
(200 ml) and acetonitrile (50 ml) at ambient temperature.
The reaction mixture was then evaporated in vacuo until
aqueous hydrogen ¯uoride started to distill. The organic
material was subjected to column chromatography on silica
with chloroform as an eluent. Analytical samples of 5a, 5b,
6 and 7 were obtained after recrystallization of collected
fractions from methanol. Yields: 18%, 13%, 15%, and 6%,
respectively.
Cis-3,4-di¯uoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide
(5a): m.p. 131±1338C. Anal. Found: C, 30.84; H, 4.00; F,
21.86; S, 20.72%. C4H6F2SO2 requires: C, 30.77; H, 3.87; F,
24.33; S, 20.54%. 1H NMR (500 MHz, CDCl3) ꢅ: 5.46 (m,
Method B: The procedure described above was used, but
the time of irradiation was prolonged to 24 h. After column
chromatography, a mixture of compounds 11a and 11b (1:5
ratio) was obtained in a 68% yield.

I. Nowak et al. / Journal of Fluorine Chemistry 93 (1999) 27±31
31
Trans-3-chloro-3,4-di¯uoro-2,3,4,5-tetrahydrothiophene-
1,1-dioxide (9a): m.p. 64±668C. Anal. Found: C, 25.17; H,
2.67; F, 13.15; Cl, 19.29; S, 16.79%. C4H5ClF2SO2 requires:
C, 25.21; H, 2.64; F, 19.94; Cl, 18.60; S, 17.01%. 1H NMR
(500 MHz, CDCl3) ꢅ: 5.48 (dm, 2JHF ˆ 49.6 Hz, 1H, CHF);
3.70±4.17 (m, 4H, 2ÂCH2). 19F NMR (470 MHz, CDCl3) ꢅ:
3.4. Elimination of hydrogen chloride from 3,4-dichloro-3,4-
difluoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide (11)
To a solution of trans-3,4-dichloro-3,4-di¯uoro-2,3,4,5-
tetrahydrothiophene-1,1-dioxide 11b (3.0 g, 0.013 mol) in
diethyl ether (100 ml) was added triethylamine (3.0 g,
0.030 mol), and the mixture was stirred at room tempera-
ture. The progress of the reaction was monitored by GC-MS,
which indicated that the elimination was complete in ca.
30 min. The reaction mixture was then ®ltered, the preci-
pitate washed with ether (3Â30 ml), and the combined
®ltrates were concentrated (30% of the starting volume).
This mixture was passed through silica with ether as an
eluent. Evaporation of the solvent gave a red oil (2.5 g).
Subsequent sublimation (708C @20 Torr) and recrystalliza-
tion from methanol gave 3,4-di¯uorothiophene-1,1-dioxide
(3) as a colorless solid in 53% yield. Reactions with a
mixture of 11a and 11b were done on both an analytical and
laboratory scale with no discernible difference between the
ratio of products 3 and 2 [9].
2
120.6 (m, 1F, CFCl); 183.6 (ddddd, JHF ˆ 49.6 Hz,
J ˆ 29.3, 18.3, 16.2, 2.7 Hz, 1F, CHF). GC-MS (m/z)
‡
‡
[relative intensity, ion]: 190 [2, M ], 80 [100, (C2H2FCl) ].
Trans-3,4-dichloro-3,4-di¯uoro-2,3,4,5-tetrahydrothio-
phene-1,1-dioxide (11b): m.p. 150±1528C. Anal. Found: C,
21.55; H, 1.91; Cl, 31.99; S, 14.30%. C4H4Cl2F2SO2
requires: C, 21.35; H, 1.79; Cl, 31.51; S, 14.22%. 1H NMR
(360 MHz, CDCl3) ꢅ: 3.88±4.18 (m). 19F NMR (470 MHz,
DMSO-d6) ꢅ: 110.1 (m). GC-MS (m/z) [relative intensity,
‡
‡
ion]: 224 [2, M ], 160 [5, (M±SO2) ], 125 [30, (M±SO2-
‡
‡
‡
Cl) ], 111 [35, C3H2F2Cl ], 80 [100, C2H2FCl ].
Cis-3,4-dichloro-3,4-di¯uoro-2,3,4,5-tetrahydrothio-
phene-1,1-dioxide (11a): 19F NMR (470 MHz, DMSO-d6)
ꢅ: 111.8 (m).
3,4-Di¯uorothiophene-1,1-dioxide (3): m.p. 107±1098C.
Anal. Found: C, 31.55; H, 1.32; F, 24.40; S, 21.14%.
C4H2F2SO2 requires: C, 31.58; H, 1.31; F, 24.98; S,
21.08%. 1H NMR (500 MHz, CDCl3) ꢅ: 6.31 (m). 19F
NMR (470 MHz, CDCl3) ꢅ: 128.8 (m). GC-MS (m/z)
3.3. Reaction of a mixture of 3-chloro-3,4-difluoro-2,3,4,5-
tetrahydrothiophene-1,1-dioxides (9) with
triethylamine
‡
To a solution of 3-chloro-3,4-di¯uoro-2,3,4,5-tetrahy-
drothiophene-1,1-dioxide (9) (3 g, 0.016 mol) in diethyl
ether (100 ml) was added triethylamine (3 g, 0.030 mol),
and the mixture was stirred at room temperature. The
progress of the reaction was monitored by GC-MS, which
indicated that the elimination was complete after 15 min.
The reaction mixture was then ®ltered, the precipitate
washed with ether, and the ®ltrate concentrated. The
remaining yellow residue was subjected to column chro-
matography using toluene as an eluent. Compounds 9b and
12 were isolated in 20% and 53% yield, respectively.
Cis-3-chloro-3,4-di¯uoro-2,3,4,5-tetrahydrothiophene-
[relative intensity, ion]: 152 [50, M ], 123 [40, (M±
‡
‡
CHO) ], 104 [100, (M±CHO±F) ].
Acknowledgements
We thank Prof. Wojciech Dmowski of the Polish Acad-
emy of Sciences for helpful discussions. The Siemens CCD
area detector-equipped diffractometer was purchased with
support from the U.S. National Science Foundation (Grant
CHE-9626144).
1
1,1-dioxide (9b): (oil, 85% purity); H NMR (500 MHz,
CDCl3) ꢅ: 3.6±4.1 (m, 4H); 5.35 (dm, 1H, 2JHF ˆ 47.8 Hz).
References
19F NMR (470 MHz, CDCl3) ꢅ: 114.0 (m, 1F, CFCl);
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2
3
180.4 (dddddd, 1F, JHF ˆ 47.8 Hz, JFF ˆ 35.4 Hz,
J ˆ 19.7, 16.6, 2.1, 0.5 Hz, CHF). GC-CIMS (CH4, m/z)
‡
[relative intensity, ion]: 191 [100, (M‡H) ], 171 [10,
[5] K. Beck, S. Hunig, Angew. Chem., Int. Ed. Engl. 25 (1986) 187.
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(1961) 346.
‡
(M±HF) ].
3,4-Di¯uoro-4,5-dihydrothiophene-1,1-dioxide (12): m.p.
67±698C. Anal. Found: C, 31.08; H, 2.66; F, 23.16; S,
21.06%. C4H4F2SO2 requires: C, 31.17; H, 2.61; F,
24.65; S, 20.76%. 1H NMR (500 MHz, CDCl3) ꢅ: 3.70
(ddm, 1H, 3JHF ˆ 22.5 Hz, 2JHH ˆ 14.7 Hz); 3.90 (ddd, 1H,
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Â
[10] V.I. Golikov, A.M. Aleksandrov, L.A. Alekseeva, T.E. Bezmenova,
2
3
3JHF ˆ 15.2 Hz, JHH ˆ 14.7 Hz, JHH ˆ 7.5 Hz); 5.73
L.M. Yagupol'skii, Zh. Org. Khim. 9 (1973) 2428.
[11] J.D. McClure, J. Org. Chem. 32 (1967) 3888.
[12] M. Hudlicky, J. Fluor. Chem. 36 (1987) 373.
[13] H.A. Bates, S. Smilowitz, J. Lin, J. Org. Chem. 50 (1985) 899.
[14] C.S.V. Houge-Frydrych, W.B. Motherwell, D.M. O'Shea, J. Chem.
Soc., Chem. Commun. (1987) 1819.
2
3
(ddt, 1H, JHF ˆ 52.7 Hz, JHH ˆ 7.5 Hz, J ˆ 2.1 Hz);
7.20 (m, 1H). 19F NMR (470 MHz, CDCl3) ꢅ: 111.3
3
2
(dm, 1F, JFF ˆ 30.2 Hz); 181.1 (ddddd, 1F, JHF
ˆ
ˆ
52.1, 3JFF ˆ 30.2 Hz, 3JHF ˆ 22.8, 15.2 Hz, JHF
3.4 Hz). GC-MS (m/z) [relative intensity, ion]: 154 [45,
[15] SHELXTL PLUS, Siemens Analytical X-ray Instruments, Madison, WI
(1990).
‡
‡
‡
M ], 125 [100, (M±CHO) ], 106 [100, (M±F±CHO) ].