Domino reactions with 2-fluoro-3-trifluoromethylfurans and -thiophenes [1]

Article abstract of DOI:10.1007/s007060170056

The single fluorine atom of 2-fluoro-3-trifluoromethylfurans and -thiophenes can be readily replaced by various nucleophiles. Depending on the substituent pattern, certain products obtained upon nucleophilic substitution with benzyl alcohols are susceptible to [1,3]- and [1,5]-benzyl group migrations under very mild conditions. Therefore, these rearrangements can be integrated into domino reactions.

Full text of DOI:10.1007/s007060170056

Monatshefte fuÈr Chemie 132, 929±945 (2001)
Domino Reactions with 2-Fluoro-3-
tri¯uoromethylfurans and -thiophenes [1]
Klaus Burger1;Ã, Annett Fuchs1, Lothar Hennig1, Brigitte Helmreich1,
and Dieter Greif2
1
È
Institut fuÈr Organische Chemie der Universitat Leipzig, D-04103 Leipzig, Germany
È
Hochschule Zittau/Gorlitz, Fachbereich Mathematik und Naturwissenschaften, D-02763 Zittau,
2
Germany
Summary. The single ¯uorine atom of 2-¯uoro-3-tri¯uoromethylfurans and -thiophenes can be
readily replaced by various nucleophiles. Depending on the substituent pattern, certain products
obtained upon nucleophilic substitution with benzyl alcohols are susceptible to [1,3]- and [1,5]-benzyl
group migrations under very mild conditions. Therefore, these rearrangements can be integrated into
domino reactions.
Keywords. 2-Fluoro-3-tri¯uoromethylfurans; 2-Fluoro-3-tri¯uoromethylthiophenes; 3-Tri¯uoromethyl-
2(3H)-furanones; 3-Tri¯uoromethyl-2(3H)-thiophenones; 3-Tri¯uoromethyl-2(5H)-furanones; 3-Tri-
¯uoromethyl-2(5H)-thiophenones; [1,3]- and [1,5]-benzyl group migrations; Domino reactions.
Introduction
Due to their large abundance [2] and their broad biological activities, butenolides
have been studied extensively and still constitute an area of current interest.
Consequently, numerous synthetic pathways to this class of compounds have been
developed [3,4]. Recently, we have demonstrated that 5-¯uoro-4-tri¯uoromethyl-
1,3-azoles [5], 2-¯uoro-3-tri¯uoromethylfurans [6], and 2-¯uoro-3-tri¯uoromethyl-
thiophenes [7] are valuable building blocks for the synthesis of partially ¯uorinated
heterocycles [8]. The single ¯uorine atom adjacent to the tri¯uoromethyl group can
be replaced by various nucleophiles under relatively mild reaction conditions. This
strategy provides ready access to tri¯uoromethyl substituted heterocycles with
interesting substituent patterns [9].
In this paper we report on the synthesis of tri¯uoromethyl substituted butenolides
and their thioanalogues via domino reactions [10] starting from 2-¯uoro-3-tri¯uoro-
methylfurans and -thiophenes, respectively.
Results and Discussion
Already at room temperature, the ¯uorine atom at C-2 of 2-¯uoro-3-tri¯uoromethyl-
furans 1 and -thiophenes 2 is susceptible to nucleophilic displacement reactions, e.g.
by benzyl alcohols in the presence of sodium hydride, in high yields.
Ã
Corresponding author. E-mail: burger@organik.chemie.uni-leipzig.de

930
K. Burger et al.
Scheme 1
Under these conditions the substitution products 3 are capable to react further.
The reaction rate of the subsequent rearrangement depends strongly on the sub-
stituent pattern of the aromatic ring of the benzyl alcohol. Derivatives of 3,4,5-
trimethoxy benzyl alcohol exhibit the strongest tendency to rearrange. In the case of
the thioanalogues 4, the rearrangement only occurs at elevated temperatures.
When a solution of compounds 3 and 4 in xylene is heated to 120ꢀC (method
A), after three hours no starting material can be detected by 19F NMR spectroscopy.
Two new products are formed. The compounds generated from 3 give rise to
1
absorptions at ꢀ ˆ 1810 and 1765 cm in their IR spectra which we assign to an
isolated and a conjugated lactone moiety. The carbon atom C-3 bearing the tri-
¯uoromethyl group resonates at 60 ppm in the main product and at 125 ppm in the
by-product, indicating that in the ®rst case the tri¯uoromethyl group is bonded to a
sp3 carbon atom and in the latter case to an sp2 hybridized carbon atom. The
spectroscopic data of the products formed from 3 are in agreement with structures
represented by formulae 5 and 7, respectively. Analogously, the products of the
rearrangement of the thioanalogues 4 can be identi®ed as tri¯uoromethyl-2(3H)-
thiophenones 6 and tri¯uoromethyl-2(5H)-thiophenones 8.
Although compounds 3 and 4 can be classi®ed as Claisen systems, no [3,3]-
sigmatropic process can be observed. The isolated products are the result of
[1,3]- and [1,5]-benzyl group migrations. Since a subsequent transformation of
compounds 5 into 7 and compounds 6 into 8 cannot be achieved, the benzyl group
migrations are obviously competing reactions. In all cases studied so far, the rate of
the [1,3]-benzyl group migration is faster than the rate of the [1,5]-group migration.
However, at elevated temperatures the yields of the by-products 7 and 8 increase.
A photochemically induced rearrangement of 3-benzyloxycholesta-3,5-diene to
give 4-benzylcholest-4-en-3-one described in 1968 represents the ®rst example of a

Reactions of Fluorinated Furans and Thiophenes
931
Scheme 2
[1,3]-benzyl group migration from oxygen to carbon [12]. Furthermore, [1,3]-
benzyl group migrations have been observed in anionic systems [13]. Examples for
a competition of [1,3]- and [1,5]-migrations have been described by W. Steglich et al.
in the 5-benzyloxyoxazole series [14].
Performing the rearrangement of compounds 3 at room temperature (method
B),19F NMR analysis revealed that extremely long reaction times are necessary (6±8
weeks). Surprisingly, 3-tri¯uoromethyl-2(3H)-furanones 5 are only formed as by-
products in this case, and 3-tri¯uoromethyl-2(5H)-furanones 7 cannot be detected
even spectroscopically. For the new main product, IR absorptions at ꢀ ˆ 1737 and
1
1680 cm are recorded, which are in agreement with the presence of a conjugated
ester and a conjugated keto function. The 13C NMR spectrum of compound
9a shows absorptions at 128.6 ꢁq; 2JCF ˆ 32:2 Hz; ˆCCF3† and 141.5 ppm
ꢁq; 3JCF ˆ 4:9 Hz; ˆCH†, which is characteristic for a -CH=CCF3-substructure.
Resonance lines at 160.2 and 189.9 ppm con®rm the information already extracted
from the IR spectra, i.e. that both ester and keto function are in conjugation with a
C=C double bond. The spectroscopic data are in agreement with a structure
depicted by formula 9. ꢁ,ꢂ-Unsaturated ꢃ-keto acid derivatives of type 9 represent
valuable tri¯uoromethyl substituted building blocks with a multifunctional array of
functional groups [15]. Their formation can be explained via a hydrolytic ring
opening of substitution products 3 followed by oxidation on air. Detailed
mechanistic studies are in progress. In contrast, the corresponding 2-benzyloxy-3-
tri¯uoromethylthiophenes 4 are stable under similar reaction conditions. Hydrolysis

932
K. Burger et al.
Scheme 3
of 5e results in the formation of the aryl substituted 3,3,3-tri¯uoromethylpropionic
acid 10. Compounds of type 10 represent interesting building blocks; they can
be used as starting materials for the synthesis of GABA derivatives [15].
ꢁ-Arylpropionic acids (e.g. ibuprofen) are a class of non-steroid antiin¯ammatories
which exhibit growing potential in treatment of polyarthritis, arthrosis, and
rheumatic diseases [16]. Because of the structural similarity, modi®cation of
compounds 10 could be of interest in developing new selective COX-2 inhibitors
[17].
Reactions of 2-¯uoro-3-tri¯uoromethylfurans 1 and -thiophenes 2 with second-
ary benzyl alcohols, e.g. 4,40-di¯uorobenzhydrol, in the presence of sodium hydride
are complete within a few hours at room temperature (19F NMR analysis). The
second aryl group lowers the activation barrier of the rearrangement. When 1 was
reacted, the successive [1,3]- and [1,5]-rearrangements are fast compared to the
nucleophilic substitution process. Therefore, the intermediacy of 11 could not be
proved even by 19F NMR spectroscopy. Similar benzhydryl group migrations have
been described in the literature: 4-benzhydryloxy-5-methoxy[1,2]benzoquinone
Scheme 4

Reactions of Fluorinated Furans and Thiophenes
933
Scheme 5
! 3-benzhydryl-2-hydroxy-5-methoxy[1,4]benzoquinone [18] and 4-bromo-3-
benzhydryloxy-1,5-diphenyl-2,5-dihydropyrrol-2-one ! 4-benzhydryl-1,5-diphenyl-
2,3-dihydro-2,3-pyrroldione [19].
When thiophene 2b was reacted with 4,40-di¯uorobenzhydrol, we were able to
isolate and characterize the substitution product 14 which at room temperature
slowly rearranges (2 ! 14 ! 15). A competition of a [1,5]-migration could not be
detected under the reaction conditions applied. Compounds 12, 13, and 15 show two
sets of signals for two diastereotopic 4-¯uorophenyl groups in their 13C and 19F
NMR spectra.
Repeatedly, [1,3]-benzyl group migrations from oxygen to carbon have been
classi®ed as sigmatropic processes [20]. In earlier investigations on the mechanism
of benzyl group migrations we could prove that in the case of 5-benzyloxy-4-
tri¯uoromethyloxazoles a multi-step procedure is operating, consisting of a separate
bond-breaking and bond-forming process [21]. To clarify the mechanism of the
above discussed [1,3]- and [1,5]-benzyl group migrations, we performed inter-
crossing experiments.
A mixture of equimolar amounts of the two substitution products 3b and 3d was
heated to 120ꢀC in xylene. Then, the composition of the reaction mixture obtained
was analyzed by GC/MS. In the case of a multi-step procedure, the formation of
four products should be expected (AA, BB, AB, BA), whereas for a concerted
process only the products AA and BB should be obtained.
Unequivocally, four compounds could be detected and characterized by mass
spectrometry via mol peak and base peak. The intercrossing products AB and BA
are only formed in minor amounts and could not be isolated. As an additional
argument for a multi-step procedure we interprete the formation of products 7 and 8

934
K. Burger et al.
Scheme 6
via a [1,5]-benzyl group migration. For this process, a sequence of two [1,3]-
migration steps can be ruled out.
The formation of only small amounts of the intercrossing products suggests that
the rearrangement proceeds via close radical or ion pairs. Experiments to trap the
radical species were unsuccessful so far as were ESR experiments. On the other
hand, the rate of the rearrangements turned out to be independent of the polarity of
the solvents used. As a strong argument against an ionic pathway we interpret the
fact that no degradation products of the tri¯uoromethyl group could be detected
which should be expected if anionic intermediates of type 16 are formed. Detailed
mechanistic studies are in progress.
Scheme 7

Reactions of Fluorinated Furans and Thiophenes
935
Scheme 8
Upon reaction of 1e with benzyl mercaptane and benzylamine, stable substitution
products 17 and 18 are formed. Experiments to initiate [1,3]- and [1,5]-benzyl group
migrations by heating have been unsuccessful so far. The compounds are stable up
to 140ꢀC; above this temperature an unde®ned decomposition process starts. Similar
reaction behaviour is exhibited by compounds 19, readily obtainable from 1e and
2-hydroxymethyl pyridine.
In contrast, 1b reacts with 2-hydroxymethyl thiophene in the presence of sodium
hydride already at 0ꢀC. We were not able to isolate the expected substitution
product 20. Under the reaction conditions applied, 20 reacts further to give 21, the
product of a [1,3]-thenyl group migration, which turned out to be unstable even at
0ꢀC and slowly rearranges to give a Cope product which spontaneously undergoes
heteroaromatization (21 ! 22). The domino reaction, the transformation of 2-¯uoro-
3-tri¯uoromethylfurans into 3-tri¯uoromethylbutenolides includes four separate
steps:
1) a nucleophilic substitution,
2) a [1,3]-thenyl group migration,
3) a Cope rearrangement, and
4) ®nally a rearomatization process
The complete reaction sequence can be performed already at 0ꢀC. Compounds of
type 22 represent preparatively interesting Michael systems.

936
K. Burger et al.
Scheme 9
To the best of our knowledge this is the ®rst example of a domino reaction including
a thenyl group migration.
Experimental
General
Solvents were puri®ed and dried prior to use. Reagents were used as purchased. Melting points
(uncorrected) were determined on a Boetius heating table. Mass spectra were recorded on a VG
12-250 and a MAT 212 (Masslab) electron ionization spectrometer (EI-MS, EI ˆ 70 eV). IR spectra
were obtained with a FTIR spectrometer (Genesis ATI Mattson/Unicam) and a Specord M 80 (Fa.
Carl Zeiss, Jena). 1H (200 MHz), 13C (50 MHz), and 19F (188 MHz) NMR spectra were recorded on a
Varian Gemini 2000 spectrometer. TMS was used as reference for 1H and 13C NMR spectra (internal),
and CF3CO2H for 19F NMR spectra (external). Flash chromatography was performed using silica gel
(32±63 mm). Elemental analyses were performed with a CHNO-S-Rapid apparatus (Fa. Heraeus).
1 ! 3 and 2 ! 4; general procedure
To an ice cold solution of 1 [6] or 2 [7] (2 mmol) and of the corresponding benzyl alcohol (4 mmol) in
THF (5 cm3), NaH (0.12 g, 5 mmol) was added. Then the reaction mixture was stirred at room
temperature until the starting material was consumed (19F NMR analysis). The reaction mixture was
treated with an ice/water mixture and extracted with ether. After drying the organic phase with
MgSO4, the solvent was evaporated in vacuo. The remaining crude product was puri®ed by column
chromatography (eluent: CH2Cl2/petrol ether).
2-Benzyloxy-5-phenyl-3-tri¯uoromethylfuran (3a; C18H13F3O2)
Yield: 77%; colourless oil; 1H NMR (CDCl3): ꢄ ˆ 5.22 (s, 2H, OCH2), 6.50 (s, 1H, CHfuran), 7.29 (m,
2
10H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 74.0 (OCH2), 93.7 (q, J ˆ 39:0 Hz, C-3furan), 103.5 (q,
1
3J ˆ 2:0 Hz, C-4furan), 122.6 (q, J ˆ 266:0 Hz, CF3), 122.9, 127.4, 128.1, 128.6, 128.7 (2x), 129.4,

Reactions of Fluorinated Furans and Thiophenes
937
134.9 (arom.), 144.6 (C-5furan), 156.2 (q, 3J ˆ 4:0 Hz, C-2furan) ppm; 19F NMR (CDCl3): ꢄ ˆ 20.7 (s,
‡
3F, CF3) ppm; IR (®lm) ꢀ ˆ 1675, 1600, 1500, 1455, 1445 cm 1; MS (EI): m=z ˆ 318 [M] , 228
‡
‡
‡
‡
‡
‡
[M±C7H6] , 208 [M±C7H7, ±F] , 107 [C7H7O] , 105 [C6H5CO] , 91 [C7H7] , 77 [C6H5] .
2-Benzyloxy-5-(4-chlorophenyl)-3-tri¯uoromethylfuran (3b; C18H12ClF3O2)
1
Yield: 93%; mp.: 47ꢀC; H NMR (CDCl3): ꢄ ˆ 5.32 (s, 2H, OCH2), 6.56 (s, 1H, CHfuran), 7.35 (m,
9H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 74.3 (OCH2), 94.1 (q, 2J ˆ 39 Hz, C-3furan), 104.1 (q,
1
3J ˆ 2 Hz, C-4furan), 122.4 (q, J ˆ 266 Hz, CF3), 124.2, 127.9, 128.0, 128.2, 128.9, 129.0, 133.2,
3
134.9 (arom.), 143.6 (C-5furan), 156.4 (q, J ˆ 4 Hz, C-2furan) ppm; 19F NMR (CDCl3): ꢄ ˆ 20.4 (s,
3F, CF3) ppm; IR (KBr): ꢀ ˆ 1640, 1600, 1580, 1555, 1455, 1445, 1405 cm 1; MS (EI):
‡
‡
‡
‡
m=z ˆ 354=352 [M] , 263/261 [M±C7H7] , 141/139 [C7H4ClO] , 91 [C7H7], 77 [C6H5] .
2-(4-Chlorobenzyloxy)-5-(4-¯uorophenyl)-3-tri¯uoromethylfuran (3c; C18H11ClF4O2)
1
Yield: 65%; mp.: 56ꢀC; H NMR (CDCl3): ꢄ ˆ 5.33 (s, 2H, OCH2), 6.55 (s, 1H, CHfuran), 7.09 (m,
3H, arom.), 7.38 (m, 3H, arom.), 7.49 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 73.7 (OCH2),
94.5 (q, 2J ˆ 38:2 Hz, C-3furan), 103.2 (q, 3J ˆ 2:1 Hz, C-4furan), 115.8 (d, 2J ˆ 22:3 Hz, C-3,
C-5fluorophenyl), 122.3 (q, 1J ˆ 266:0 Hz, CF3), 124.9 (d, 3J ˆ 8:0 Hz, C-2, C-6fluorophenyl), 125.8
4
(d, J ˆ 3:3 Hz, C-1fluorophenyl), 128.9, 129.5, 129.8, 134.9 (arom.), 144.1 (C-5furan), 155.9 (C-2furan),
162.3 (d, 1J ˆ 247:5 Hz, C-4fluorophenyl) ppm; 19F NMR (CDCl3): ꢄ ˆ 35.7 (m, 1F, p-FC6H4), 20.1
(s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1650, 1610, 1590, 1450, 1360 cm 1; MS (EI): m=z ˆ 370=372
‡
‡
‡
‡
‡
[M] , 245 [M±C7H6Cl] , 226 [M±C7H6Cl, -F] , 197 [M±C7H6Cl, ±F, ±CO] , 125/127 [C7H6Cl]
(100).
5-(4-Bromophenyl)-2-(4-chlorobenzyloxy)-3-tri¯uoromethylfuran (3d; C18H11BrClF3O2)
1
Yield: 87%; mp.: 65ꢀC; H NMR (CDCl3): ꢄ ˆ 5.33 (s, 2H, OCH2), 6.63 (s, 1H, CHfuran), 7.38 (m,
5H, arom.), 7.51 (m, 3H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 73.6 (OCH2), 94.5 (q, 2J ˆ 39:6 Hz,
C-3furan), 104.2 (q, 3J ˆ 2:3 Hz, C-4furan), 121.4 (arom.), 122.2 (q, 1J ˆ 266:2 Hz, CF3), 124.5, 128.3,
3
129.0, 129.5, 132.0, 133.2, 134.9 (arom.), 143.8 (C-5furan), 156.2 (q, J ˆ 4:6 Hz, C-2furan) ppm; 19F
NMR (CDCl3): ꢄ ˆ 20.1 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1650, 1600, 1580, 1450, 1360 cm 1; MS
‡
‡
‡
(EI): m=z ˆ 430=432=434 [M] , 305/307 [M±C7H6Cl] , 125/127 [C7H6Cl] (100).
2-(4-Chlorobenzyloxy)-5-(2-¯uorophenyl)-3-tri¯uoromethylfuran (3e; C18H11ClF4O2)
1
5
Yield: 81%; mp.: 48ꢀC; H NMR (CDCl3): ꢄ ˆ 5.36 (s, 2H, OCH2), 6.84 (d, J ˆ 3 Hz, CHfuran),
7.21 (m, 4H, arom.), 7.39 (m, 3H, arom.), 7.60 (m, 1H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 73.5
(OCH2), 94.5 (q, 2J ˆ 39:2 Hz, C-3furan), 108.9 (d, 4J ˆ 10:3 Hz, C-4furan), 116.1 (d, 2J ˆ 21:3 Hz, C-
2
1
3
3fluorophenyl), 117.9 (d, J ˆ 12:2 Hz, C-1fluorophenyl), 122.4 (q, J ˆ 266:2 Hz, CF3), 124.4 (d, J ˆ
4
3
3:4 Hz, C-6fluorophenyl), 125.1 (d, J ˆ 2:8 Hz, C-5fluorophenyl), 128.6 (d, J ˆ 8:3 Hz, C-4fluorophenyl),
129.0, 129.5, 133.3, 134.9 (arom.), 139.3 (d, 3J ˆ 2:3 Hz, C-5furan), 156.0 (C-2furan), 158.5
(1J ˆ 250:7 Hz, C-2fluorophenyl) ppm; 19F NMR (CDCl3): ꢄ ˆ 36.6 (m, 1F, o-FC6H4), 20.1 (s, 3F,
CF3) ppm; IR (KBr): ꢀ ˆ 1650, 1620, 1580, 1480, 1470, 1430, 1360 cm 1; MS (EI): m=z ˆ 370=372
‡
‡
‡
[M] , 245 [M±C7H6Cl] , 125/127 [C7H6Cl] (100).
2-(4-Bromobenzyloxy)-5-(4-¯uorophenyl)-3-tri¯uoromethylfuran (3f; C18H11BrF4O2)
1
Yield: 82%; mp.: 58ꢀC; H NMR (CDCl3): ꢄ ˆ 5.31 (s, 2H, OCH2), 6.55 (s, 1H, CHfuran), 7.08 (m,
2H, arom.), 7.31 (m, 2H, arom.), 7.51 (m, 4H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 73.7 (OCH2),

938
K. Burger et al.
94.5 (q, 2J ˆ 38:9 Hz, C-3furan), 103.2 (m, C-4furan), 115.8 (d, 2J ˆ 22:4 Hz, C-3, C-5fluorophenyl), 122.3
(q, 1J ˆ 265:9 Hz, CF3), 123.0 (arom.), 124.9 (d, 3J ˆ 8 Hz, C-2, C-6fluorophenyl), 125.8 (d,
4J ˆ 3:3 Hz, C-1fluorophenyl), 129.8, 131.9, 133.9 (arom.), 144.2 (C-5furan), 159.9 (C-2furan), 162.3 (d,
1J ˆ 248 Hz, C-4fluorophenyl) ppm; 19F NMR (CDCl3): ꢄ ˆ 35.6 (m, 1F, p-FC6H4), 20.1 (s, 3F, CF3)
‡
ppm; IR (KBr): ꢀ ˆ 1650, 1600, 1590, 1450, 1360 cm 1; MS (EI): m=z ˆ 414=416 [M] , 245 [M±
‡
‡
‡
‡
C7H6Br] , 217 [M±C7H6Br, ±CO] , 197 [M±C7H6Br, ±CO, ±HF] , 169/171 [C7H6Br] (100).
2-(4-Bromobenzyloxy)-5-(4-chlorophenyl)-3-tri¯uoromethylfuran (3g; C18H11BrClF3O2)
1
Yield: 62%; mp.: 63ꢀC; H NMR (CDCl3): ꢄ ˆ 5.32 (s, 2H, OCH2), 6.62 (s, 1H, CHfuran), 7.40 (m,
6H, arom.), 7.55 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 73.6 (OCH2), 94.5 (q, 2J ˆ 38:3 Hz,
1
C-3furan), 104.1 (C-4furan), 123.1, 124.3 (arom.), 125.8 (q, J ˆ 264:7 Hz, CF3), 127.9, 129.1, 129.8,
131.9, 133.4, 133.8 (arom.), 143.9 (C-5furan), 156.1 (q, 3J ˆ 3:9 Hz, C-2furan) ppm; 19F NMR
(CDCl3): ꢄ ˆ 20.3 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1650, 1600, 1580, 1450, 1360 cm 1; MS (EI):
‡
‡
‡
m=z ˆ 430=432=434 [M] , 261/263 [M±C7H6Br] , 242/244 [M±C7H6Br, ±F] , 213/215
‡
‡
[M±C7H6Br, ±HF, ±CO] , 169/171 [C7H6Br] (100).
5-(4-Chlorophenyl)-2-(3,4,5-trimethoxybenzyloxy)-3-tri¯uoromethylfuran (3h; C21H18ClF3O5)
Yield: 81%; mp.: not detectable due to rearrangement; 1H NMR (CDCl3): ꢄ ˆ 3.85 (s, 9H,
3 Â OCH3), 5.30 (s, 2H, OCH2), 6.61 (s, 1H, CHfuran), 6.67 (s, 2H, arom.), 7.33 (m, 2H, arom.), 7.43
(m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 56.1 (2  OCH3), 60.8 (OCH3), 74.4 (OCH2), 94.2 (q,
2J ˆ 38:7 Hz, C-3furan), 104.0 (q, 3J ˆ 2:4 Hz, C-4furan), 105.3 (arom.), 122.4 (q, 1J ˆ 266:6 Hz,
CF3), 124.2, 127.9, 129.0, 130.3, 133.3, 138.5 (arom.), 143.7 (C-5furan), 153.5 (arom.), 156.3 (q,
3J ˆ 4:6 Hz, C-2furan) ppm; 19F NMR (CDCl3): ꢄ ˆ 20.2 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1633,
‡
‡
1600, 1462, 1453, 1369 cm 1; MS (EI): m=z ˆ 441=443 [M] , 260/262 [M±C7H4(OCH3)3] , 181
‡
[C7H4(OCH3)3] (100).
2-(4-Chlorobenzyloxy)-5-(4-chlorophenyl)-3-tri¯uoromethylthiophene (4; C18H11Cl2F3OS)
Yield: 80%; mp.: 120ꢀC; 1H NMR (CDCl3): ꢄ ˆ 5.18 (s, 2H, OCH2), 7.06 (s, 1H, CHthiophene),
7.36 ppm (m, 8H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 76.6 (OCH2), 113.5 (q, 2J ˆ 34:8 Hz,
3
1
C-3thiophene), 118.7 (q, J ˆ 3:2 Hz, C-4thiophene), 122.0 (q, J ˆ 270:2 Hz, CF3), 126.3, 129.0, 129.1,
129.2 (arom.), 129.5 (C-5thiophene), 131.8, 133.2, 133.5, 134.8 (arom.), 163.3 (q, 3J ˆ 3:4 Hz,
C-2thiophene) ppm; 19F NMR (CDCl3): ꢄ ˆ 19.5 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1579, 1512, 1421,
‡
‡
‡
1374 cm 1; MS (EI): m=z ˆ 403=405 [M] , 276/278 [M±C7H6Cl] , 125/127 [C7H6Cl] (100).
3 ! 5 ‡ 7 and 4 ! 6 ‡ 8; general procedure
Method A: A solution of 3 (2 mmol) or 4 (2 mmol) in xylene (5 cm3) was heated to 120ꢀC until the
starting material was consumed (19F NMR analysis). The reaction mixture was poured into an ice/
water mixture and extracted with ether. After drying the organic phase with MgSO4, the solvent was
evaporated in vacuo. Finally, the crude product was puri®ed by column chromatography (eluent:
petrolether/CH2Cl2, elution sequence: 5, 7 and 6, 8, respectively).
3 ! 5 ‡ 9; general procedure
Method B: A solution of 3 (2 mmol) in CHCl3 (5 cm3) or in xylene (5 cm3) was stirred at room
temperature until the starting material was completely consumed (19F NMR analysis). Work-up: see
above; elution sequence: 5, 9.

Reactions of Fluorinated Furans and Thiophenes
939
3-Benzyl-5-phenyl-3-tri¯uoromethyl-2(3H)-furanone (5a; C18H13F3O2); 5-Benzyl-5-phenyl-
3-tri¯uoromethyl-2(5H)-furanone (7a; C18H13F3O2)
5a: yield: 70%; mp.: 84ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.18 (d, 2J ˆ 13 Hz, 1H, CHa2), 3.42 (d,
2J ˆ 13 Hz, 1H, CHb2), 5.66 (s, 1H, CHfuranone), 7.12 (m, 5H, arom.), 7.34 (m, 5H, arom.) ppm; 13C
NMR (CDCl3): ꢄ ˆ 37.3 (CH2), 60.2 (q, 2J ˆ 28 Hz, C-3furanone), 98.0 (C-4furanone), 123.9 (q,
1J ˆ 283 Hz, CF3), 125.3, 126.9, 127.8, 128.5, 128.7, 130.0, 130.7, 132.7 (arom.), 155.7 (C-5furanone),
171.4 (C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 6.2 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1805, 1660,
‡
‡
‡
1500, 1455 cm 1; MS (EI): m=z ˆ 318 [M] , 227 [M±C7H7] , 179 [M±C7H7, ±CO, ±HF] , 91
‡
‡
[C7H7] , 77 [C6H5] .
7a: yield: 14%; mp.: 133ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.38 (d, 2J ˆ 14:0 Hz, 1H, CHa2), 3.47 (d,
2J ˆ 14:0 Hz, 1H, CHb2), 7.05 (m, 2H, arom.), 7.24 (m, 3H, arom.), 7.40 (m, 5H, arom.), 8.03 (q,
4J ˆ 2:0 Hz, 1H, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 46.5 (CH2), 89.4 (C-5furanone), 119.3 (q,
2
1J ˆ 270 Hz, CF3), 124.5 (q, J ˆ 37:0 Hz, C-3furanone), 125.2, 127.2, 128.5, 129.0, 129.1, 130.3,
132.6, 136.7 (arom.), 158.7 (q, 3J ˆ 4:0 Hz, C-4furanone), 164.8 (C-2furanone) ppm; 19F NMR (CDCl3):
‡
ꢄ ˆ 13.0 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1765, 1500, 1455 cm 1; MS (EI): m=z ˆ 227 [M±C7H7] ,
‡
‡
91 [C7H7] , 77 [C7H7] .
3-(4-Chlorobenzyl)-5-(2-¯uorophenyl)-3-tri¯uoromethyl-2(3H)-furanone (5b; C18H11ClF4O2);
5-(4-Chlorobenzyl)-5-(2-¯uorophenyl)-3-tri¯uoromethyl-2(5H)-furanone (7b; C18H11ClF4O2)
1
2
5b: yield: 52% (method A), 14% (method B); oil; H NMR (CDCl3): ꢄ: 3.27 (d, J ˆ 13:4 Hz, 1H,
CHa2), 3.48 (d, J ˆ 13:4 Hz, 1H, CHb2), 6.02 (d, J ˆ 2:5 Hz, CHfuranone), 7.14 (m, 4H, arom.) 7.20
(m, 2H, arom.) 7.40 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 36.4 (CH2), 60.1 (q, 2J ˆ 28:2 Hz,
C-3furanone), 103.5 (d, 4J ˆ 13:6 Hz, C-4furanone), 115.1 (d, 2J ˆ 11:3 Hz, C-1fluorophenyl), 116.1 (d,
2
5
2J ˆ 20:7 Hz, C-3fluorophenyl), 123.7 (q, J ˆ 283:0 Hz, CF3), 124.5 (d, J ˆ 3:9 Hz, C-6fluorophenyl),
127.7 (C-5fluorophenyl), 128.7, 131.1, 131.5 (arom.), 132.0 (q, 3J ˆ 9:0 Hz, C-4fluorophenyl), 133.9
(arom.), 150.3 (d, 3J ˆ 2:3 Hz, C-5furanone), 160.6 (d, 1J ˆ 252:5 Hz, C-2fluorophenyl), 170.3 (q,
3J ˆ 2:3 Hz, C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 33.3 (m, 1F, o-FC6H4), 6.0 (s, 3F, CF3)
1
4
ppm; IR (Film): ꢀ ˆ 1813, 1649, 1493, 1453 cm 1; MS (EI): m=z ˆ 370=372 [M] , 246 [M±
‡
‡
‡
‡
C7H6Cl] , 217 [M±C7H6Cl, -CO] , 125/127 [C7H6Cl] (100).
7b: yield: 6%; mp.: 111ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.33 (d, 2J ˆ 14:0 Hz, 1H, CHa2), 3.46 (d,
2J ˆ 14 Hz, 1H, CHb2), 7.01 (m, 2H, arom.), 7.18 (m, 4H, arom.), 7.37 (m, 2H, arom.), 8.25 (q,
4J ˆ 1:6 Hz, 1H, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 43.8 (CH2), 87.4 (d, 3J ˆ 4:2 Hz,
C-5furanone), 116.1 (d, 2J ˆ 21:7 Hz, C-3fluorophenyl), 119.3 (1J ˆ 270:3 Hz, CF3), 123.8 (d, 2J ˆ 12:2 Hz,
2
C-1fluorophenyl), 124.7 (q, J ˆ 38:0 Hz, C-3furanone), 125.4 (d, 3J ˆ 3:3 Hz, C-6fluorophenyl), 127.7 (d,
4J ˆ 3:2 Hz, C-5fluorophenyl), 128.6, 131.2 (arom.), 131.2 (d, 3J ˆ 8:4 Hz, C-4fluorophenyl), 131.6, 133.8
(arom.), 158.5 (d, 1J ˆ 244:9 Hz, C-2fluorophenyl), 164.3 (C-2furanone) ppm; 19F NMR (CDCl3):
ꢄ ˆ 36.9 (m, 1H, o-FC6H4), 12.9 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1775, 1489, 1361 cm 1; MS
‡
‡
‡
‡
(EI): m=z ˆ 370=372 [M] , 245 [M±C7H6Cl] , 197 [M±C7H6Cl, ±CO] , 125/127 [C7H6Cl] (100).
3-(4-Chlorobenzyl)-5-(4-¯uorophenyl)-3-tri¯uoromethyl-2(3H)-furanone (5c; C18H11ClF4O2);
5-(4-Chlorobenzyl)-5-(4-¯uorophenyl)-3-tri¯uoromethyl-2(5H)-furanone (7c; C18H11ClF4O2)
5c: yield: 60% (method A), 18% (method B); mp.: 73ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.22 (d,
2
2J ˆ 13:5 Hz, 1H, CH2a), 3.45 (d, J ˆ 13:5 Hz, 1H, CH2b), 5.65 (s, 1H, CHfuranone), 7.09 (m, 4H,
arom.), 7.22 (m, 2H, arom.), 7.48 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 36.5 (CH2), 60.1 (q,
2
2J ˆ 27:6 Hz, C-3furanone), 97.1 (C-4furanone), 116.2 (d, J ˆ 22:4 Hz, C-3, C-5fluorophenyl), 122.9 (d,
4J ˆ 3:2 Hz, C-1fluorophenyl), 123.8 (q, 1J ˆ 283:1 Hz, CF3), 127.5 (d, 3J ˆ 8:5 Hz, C-2, C-6fluorophenyl),
128.8, 131.2, 131.3, 133.9 (arom.), 155.1 (C-5furanone), 164.1 (d, 1J ˆ 252 Hz, C-4fluorophenyl), 170.8 (q,
3J ˆ 2:3 Hz, C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 30.3 (m, 1F, p-FC6H4), 5.9 (s, 3F, CF3)

940
K. Burger et al.
‡
ppm; IR (KBr): ꢀ ˆ 1811, 1659, 1601, 1508, 1493 cm 1; MS (EI): m=z ˆ 370=372 [M] , 245
‡
‡
‡
[M±C7H6Cl] , 217 [M±C7H6Cl, ±CO] , 125/127 [C7H6Cl] (100).
7c: yield: 15%; mp.: 148ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.29 (d, 2J ˆ 14:1 Hz, 1H, CHa2), 3.39
(d; J ˆ 14:1 Hz, 1H, CH2b), 6.95 (m, 2H, arom.), 7.09 (m, 2H, arom.), 7.28 (m, 4H, arom.), 7.99 (q,
4J ˆ 1:5 Hz, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 45.9 (CH2), 88.7 (C-5furanone), 116.2 (d,
2J ˆ 22:1 Hz, C-3, C-5fluorophenyl), 119.2 (q, J ˆ 271 Hz, CF3), 125.0 (q, J ˆ 37:8 Hz, C-3furanone),
127.2 (d, 3J ˆ 8:1 Hz, C-2, C-6fluorophenyl), 128.7, 130.9, 131.6 (arom.), 132.2 (d, 4J ˆ 3:4 Hz,
C-1fluorophenyl), 134.0 (arom.), 158.1 (q, 3J ˆ 3:5 Hz, C-4furanone), 162.9 (d, 1J ˆ 249:6 Hz, C-4fluorophenyl),
164.5 (C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 33.9 (m, 1F; p-FC6H4), 13.0 (s, 3F, CF3) ppm; IR
1
2
‡
‡
(KBr): ꢀ ˆ 1765, 1513, 1491, 1368 cm 1; MS (EI): m=z ˆ 370=372 [M] , 245 [M±C7H6Cl] , 197
‡
‡
[M±C7H6Cl, ±F, ±CO] , 125/127 [C7H6Cl] (100).
5-(4-Bromophenyl)-3-(4-chlorobenzyl)-3-tri¯uoromethyl-2(3H)-furanone (5d; C18H11BrClF3O2);
5-(4-Bromophenyl)-5-(4-chlorobenzyl)-3-tri¯uoromethyl-2(5H)-furanone (7d; C18H11BrClF3O2)
1
2
5d: yield: 50% (method A), 20% (method B); mp.: 92ꢀC; H NMR (CDCl3): ꢄ ˆ 3.22 (d, J ˆ
13:5 Hz, 1H, CHa2), 3.46 (d, J ˆ 13:5 Hz, 1H, CH2b), 5.73 (s, 1H, CHfuranone), 7.08 (m, 2H, arom.),
2
7.22 (m, 2H, arom.), 7.34 (m, 2H, arom.), 7.53 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 36.5
2
1
(CH2), 60.1 (q, J ˆ 27:6 Hz, C-3furanone), 98.1 (C-4furanone), 123.6 (q, J ˆ 282:9 Hz, CF3), 125.4,
125.5, 126.8, 128.8, 131.0, 131.1, 132.2, 134.0 (arom.), 155.1 (C-5furanone), 170.7 (C-2furanone) ppm;
19F NMR (CDCl3): ꢄ ˆ 6.0 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1811, 1652, 1592, 1490 cm 1; MS (EI):
‡
‡
‡
m=z ˆ 430=432=434 [M] , 305/307 [M±C7H6Cl] , 257/259 [M±C7H6Cl, ±CO, ±HF] , 125/127
‡
[C7H6Cl] (100).
7d: yield: 6%; mp.: 172ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.28 (d, 2J ˆ 14:2 Hz, 1H, CHa2), 3.39 (d,
2J ˆ 14:2 Hz, 1H, CHb2), 6.95 (m, 2H, arom.), 7.20 (m, 2H, arom.), 7.24 (m, 2H, arom.), 7.53 (m, 2H,
arom.), 7.98 (q, 4J ˆ 1:4 Hz, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 45.7 (CH2), 88.7 (C-5furanone),
119.2 (q, 1J ˆ 270:5 Hz, CF3), 123.4 (arom.), 125.0 (q, 2J ˆ 37:8 Hz, C-3furanone), 126.9, 128.8,
130.8, 131.7, 132.4, 134.0, 135.4 (arom.), 157.9 (q; J ˆ 3:6 Hz, C-4furanone), 164.3 (C-2furanone) ppm;
19F NMR (CDCl3): ꢄ ˆ 13.0 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1766, 1491, 1367 cm 1; MS (EI):
‡
‡
‡
m=z ˆ 430=432=434 [M] , 305/307 [M±C7H6Cl] , 257/259 [M±C7H6Cl, ±HF, ±CO] , 183/185
‡
‡
[C6H4BrCO] , 125/127 [C7H6Cl] (100).
3-(4-Bromobenzyl)-5-(4-¯uorophenyl)-3-tri¯uoromethyl-2(3H)-furanone (5e; C18H11BrF4O2);
5-(4-Bromobenzyl)-5-(4-¯uorophenyl)-3-tri¯uoromethyl-2(5H)-furanone (7e; C18H11BrF4O2)
5e: yield: 60% (method A), 34% (method B); mp.: 91ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.20 (d,
2
2J ˆ 13:5 Hz, 1H, CH2a), 3.44 (d, J ˆ 13:5 Hz, 1H, CH2b), 5.65 (s, 1H, CHfuranone), 7.06 (m, 4H,
arom.), 7.37 (m, 2H, arom.), 7.48 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 36.5 (CH2), 59.9 (q,
2J ˆ 27:6 Hz, C-3furanone), 97.0 (C-4furanone), 116.1 (d, 2J ˆ 22:3 Hz, C-3, C-5fluorophenyl), 122.0
(arom.), 122.9 (d, 4J ˆ 3:3 Hz, C-1fluorophenyl), 123.8 (q, 1J ˆ 283:3 Hz, CF3), 127.5 (d, 3J ˆ 8:9 Hz,
1
C-2, C-6fluorophenyl), 131.7, 131.8 (arom.), 155.1 (C-5furanone), 162.6 (d, J ˆ 251 Hz, C-4fluorophenyl),
170.8 (q, 3J ˆ 2:3 Hz, C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 30.3 (m, 1F, p-FC6H4), 5.9 (s, 3F,
‡
CF3) ppm; IR (KBr): ꢀ ˆ 1810, 1650, 1600, 1500, 1480 cm 1; MS (EI): m=z ˆ 414=416 [M] , 245
‡
‡
‡
‡
[M±C7H6Br] , 197 [M±C7H6Br, ±CO, ±F] , 169/171 [C7H6Br] (100), 123 [FC6H4CO] .
7e: yield: 16%; mp.: 152ꢀC; 1H NMR (CDCl3): ꢄ ˆ 3.28 (d, 2J ˆ 14:0 Hz, 1H, CHa2), 3.37 (d,
2J ˆ 14:0 Hz, 1H, CHb2), 6.88 (m, 2H, arom.), 7.09 (m, 2H, arom.), 7.34 (m, 2H, arom.), 7.40 (m, 2H,
arom.), 8.01 (q, 4J ˆ 1:8 Hz, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 45.9 (CH2), 88.7 (C-5furanone),
2
1
116.2 (d, J ˆ 21:9 Hz, C-3, C-5fluorophenyl), 119.2 (q, J ˆ 270 Hz, CF3), 122.0 (arom.), 124.8 (q,
2J ˆ 37:8 Hz, C-3furanone), 127.2 (d, J ˆ 8:2 Hz, C-2, C-6fluorophenyl), 131.5, 131.7, 132.0 (arom.),
3
4
3
1
132.2 (d, J ˆ 3:3 Hz, C-1fluorophenyl), 158.3 (q, J ˆ 3:2 Hz, C-4furanone), 162.9 (d, J ˆ 249:6 Hz,

Reactions of Fluorinated Furans and Thiophenes
941
C-4fluorophenyl), 164.4 (C-2furanone) ppm; 19F NMR (CDCl3): ꢄ ˆ 33.9 (m, 1F, p-FC6H4), 13.0 (s, 3F,
‡
CF3) ppm; IR (KBr): ꢀ ˆ 1764, 1512, 1367 cm 1; MS (EI): m=z ˆ 415=417 [M] , 245 [M±
‡
‡
‡
‡
C7H6Br] , 197 [M±C7H6Br, ±CO, ±HF] , 169/171 [C7H6Br] (100), 123 [FC6H4CO] .
3-(4-Chlorobenzyl)-5-(4-chlorophenyl)-3-tri¯uoromethyl-2(3H)-thiophenone (6; C18H11Cl2F3OS);
5-(4-Chlorobenzyl)-5-(4-chlorophenyl)-3-tri¯uoromethyl-2(5H)-thiophenone (8; C18H11Cl2F3OS)
1
2
2
6: yield: 48%; oil; H NMR (CDCl3): ꢄ ˆ 3.22 (d, J ˆ 13:2 Hz, 1H, CHa2), 3.46 (d, J ˆ 13:2 Hz,
1H, CHb2), 6.07 (s, 1H, CHthiophenone), 7.09 (m, 2H, arom.) 7.22 (m, 4H, arom.), 7.34 (m, 2H, arom.)
ppm; 13C NMR (CDCl3): ꢄ ˆ 37.6 (CH2), 70.5 (q, 2J ˆ 25:2 Hz, C-3thiophenone), 114.5 (C-4thiophenone),
123.8 (q, 1J ˆ 284:7 Hz, CF3), 127.6, 128.5, 129.3, 130.4, 131.0, 131.5, 133.7, 136.2 (arom.), 142.6
(C-5thiophenone), 200.0 (C-2thiophenone) ppm; 19F NMR (CDCl3): ꢄ ˆ 7.0 (s, 3F, CF3) ppm; IR (Film):
ꢀ ˆ 1713, 1491 cm 1; MS (EI): m=z ˆ 402=404=406 [M] , 278 [M±C7H6Cl] , 214 [M±C7H6Cl,
‡
‡
‡
‡
±HF, ±CS] , 125/127 [C7H6Cl] (100).
1
8: yield: 6%; mp.: 130ꢀC; H NMR (CDCl3): ꢄ ˆ 3.55 (s, 2H, CH2), 6.88 (m, 2H, arom.), 7.22
4
(m, 2H, arom.), 7.27 (m, 2H, arom.), 7.37 (m, 2H, arom.), 7.99 (q, J ˆ 1:2 Hz, 1H, CHthiophenone
)
ppm; 13C NMR (CDCl3): ꢄ ˆ 46.9 (CH2), 65.2 (C-5thiophenone), 119.7 (1J ˆ 273 Hz, 3F, CF3), 128.2,
128.5, 129.3, 131.7 (arom.), 132.3 (arom.), 133.3 (q, 2J ˆ 33:3 Hz, C-3thiophene), 134.0, 134.9, 136.6
(arom.), 160.5 (q, 3J ˆ 3:8 Hz, C-4thiophenone), 189.5 (C-2thiophenone) ppm; 19F NMR (CDCl3): ꢄ ˆ 13.7
(s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1679, 1491, 1345 cm 1; MS (EI): m=z ˆ 402=404=406 [M] , 278/
‡
‡
‡
‡
280 [M±C7H6Cl] , 214/216 [M±C7H6Cl, ±HF, ±CS] , 125/127 [C7H6Cl] (100).
4-(4-Fluorophenyl)-4-oxo-2-tri¯uoromethyl-2-butenoic acid (4-chlorobenzyl)-ester
(9a; C18H11ClF4O3)
Yield: 40% (method B); mp.: 38ꢀC; 1H NMR (CDCl3): ꢄ ˆ 5.06 (s, 2H, CH2), 7.06 (m, 2H, arom.),
4
7.14 (m, 2H, arom.), 7.24 (m, 2H, arom.), 7.44 (q, J ˆ 1:5 Hz, 1H, ˆ CH), 7.80 (m, 2H, arom.)
2
ppm; 13C NMR (CDCl3): ꢄ ˆ 67.3 (OCH2), 116.2 (d, J ˆ 22:0 Hz, C-3, C-5fluorophenyl), 120.9 (q,
1J ˆ 273:9 Hz, CF3), 128.6 (q, 2J ˆ 32:2 Hz, C-2), 128.7 (arom.), 128.9 (C-1fluorophenyl), 129.8
3
3
(arom.), 131.4 (d, J ˆ 10:3 Hz, C-2, C-6fluorophenyl), 132.4, 134.6 (arom.), 141.5 (q, J ˆ 4:9 Hz,
ˆ CH), 160.2 (COester), 166.4 (d, J ˆ 258:1 Hz, C-4fluorophenyl), 188.9 (COketone) ppm; 19F NMR
1
(CDCl3): ꢄ ˆ 24.2 (m, 1F, p-FC6H4), 12.7 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1737, 1681, 1597,
1507, 1494 cm 1; MS (EI): m=z ˆ 386=388 [M] , 246 [M±OCH2C6H4Cl] , 226 [M±OCH2C6H4Cl,
‡
‡
‡
‡
‡
±HF] , 141/143 [OCH2C6H4Cl] , 125/127 [C7H6Cl] (100).
4-(4-Bromophenyl)-4-oxo-2-tri¯uoromethyl-2-butenoic acid (4-chlorobenzyl)-ester
(9b; C18H11BrClF3O3)
Yield: 21% (method B); oil; 1H NMR (CDCl3): ꢄ ˆ 5.05 (s, 2H, CH2), 7.05 (m, 2H, arom.), 7.24 (m,
2H, arom.), 7.41 (q, 4J ˆ 1:5 Hz, 1H, =CH), 7.45 (m, 2H, arom.), 7.71 (m, 2H, arom.) ppm; 13C NMR
(CDCl3): ꢄ ˆ 67.4 (CH2), 120.9 (q, 1J ˆ 274:3 Hz, CF3), 128.6 (q, 2J ˆ 29:6 Hz, C-2), 128.7, 129.0,
129.8, 129.9, 132.3, 132.5, 133.6, 134.7 (arom.), 141.4 (q, 3J ˆ 4:7 Hz, =CH), 160.1 (COester), 189.5
(COketone) ppm; 19F NMR (CDCl3): ꢄ ˆ 12.7 (s, 3F, CF3) ppm; IR (®lm): ꢀ ˆ 1737, 1679, 1586,
‡
‡
‡
1494, 1384, 1366 cm 1; MS (EI): m=z ˆ 446=448=450 [M] , 305/307 [M±C7H6ClO] , 285/287
‡
[M±C7H6ClO, ±HF] , 183/185 [C7H6BrO], 125/127 [C7H6Cl] (100).
4-(4-Chlorophenyl)-4-oxo-2-tri¯uoromethyl-2-butenoic acid (4-bromobenzyl)-ester
(9c; C18H11BrClF3O3)
Yield: 47% (method B); mp.: 82ꢀC; 1H NMR (CDCl3): ꢄ ˆ 5.03 (s, 2H, CH2), 6.98 (m, 2H, arom.),
7.37 (m, 2H, arom.), 7.41 (m, 3H, arom., =CH), 7.68 (m, 2H, arom.) ppm; 13C NMR (CDCl3):

942
K. Burger et al.
ꢄ ˆ 67.4 (OCH2), 120.9 (q, 1J ˆ 273:9 Hz, CF3), 128.6 (q, 2J ˆ 33:0 Hz, C-2), 122.8, 129.3, 129.9,
130.1, 131.7, 132.8, 133.1, 141.1 (arom.), 141.5 (q, 3J ˆ 4:7 Hz, =CH), 160.1 (COester), 189.3
(COketone) ppm; 19F NMR (CDCl3): ꢄ ˆ 12.7 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1738, 1667, 1587,
‡
‡
1489, 1348 cm 1; MS (EI): m=z ˆ 446=448=450 [M] , 261/263 [M±C7H6BrO] , 241/243 [M±
‡
‡
‡
C7H6BrO, ±HF] , 185/187 [C7H6BrO] , 169/171 [C7H6Br] (100).
2-(4-Bromobenzyl)-4-(4-¯uorophenyl)-4-oxo-2-tri¯uoromethyl butanoic acid (10; C18H13BrF4O3)
To a solution of 5e (0.83 g, 2 mmol) in dioxane (5 cm3), an aqueous solution of KOH (5 cm3,
pH ˆ 10) was added. The mixture was stirred at room temperature until the starting material was
completely consumed (19F NMR analysis). Then, diluted HCl was added with ice cooling until the
reaction mixture attained pH 1. The mixture was extracted with CH2Cl2, and the organic phase was
dried over MgSO4. Finally, the solvent was evaporated in vacuo, and the remainig crude material was
puri®ed by column chromatography (eluent: CHCl3:CH3OH:CH3COOH ˆ 85:10:5).
Yield: 35%; oil; 1H NMR (CDCl3): ꢄ ˆ 3.18 (d, 2J ˆ 13:5 Hz, 1H, CH2a), 3.46 (d, 2J ˆ 10:5 Hz, 1H,
2
2
CHa2), 3.63 (d, J ˆ 10:5 Hz, 1H, CH2b), 3.70 (d, J ˆ 13:5 Hz, 1H, CHb2), 6.95 (m, 2H, arom.), 7.14
(m, 2H, arom.), 7.31 (m, 2H, arom.), 7.92 (m, 2H, arom.), 9.52 (s, br, COOH) ppm; 13C NMR
2
2
(CDCl3): ꢄ ˆ 34.4 (CH2), 37.8 (CH2CO), 54.3 (q, J ˆ 23:4 Hz, C-2), 116.1 (d, J ˆ 22:6, C-3,
C-5fluorophenyl), 121.5 (arom.), 125.5 (q, 1J ˆ 285:7 Hz, CF3), 130.7 (d, 3J ˆ 9:2 Hz, C-2, C-6fluorophenyl),
1
3
131.5, 132.4, 134.0 (arom.), 166.2 (d, J ˆ 256:4 Hz, C-4fluorophenyl), 173.9 (q, J ˆ 2:1 Hz, COacid),
194.3 (COketone) ppm; 19F NMR (CDCl3): ꢄ ˆ 25.7 (m, 1F, p-FC6H4), 8.7 (s, 3F, CF3) ppm.
3-(4,40-Di¯uorobenzhydryl)-5-(2-¯uorophenyl)-3-tri¯uoromethyl-2(3H)-furanone
(12; C24H14F6O2); 5-(4,40-Di¯uorobenzhydryl)-5-(2-¯uorophenyl)-3-tri¯uoromethyl-
2(5H)-furanone (13; C24H14F6O2)
To a solution of 1d (0.49 g, 2 mmol) or 2b (0.52 g, 2 mmol) and 4,40-di¯uoro-benzhydrol (0.88 g,
4 mmol) in THF (5 cm3), NaH (0.12 g, 5 mmol) was added at 0ꢀC. The reaction mixture was stirred at
room temperature until complete conversion of the starting materials (19F NMR analysis), poured into
ice/water, and extracted with ether. The organic phase was separated and dried over MgSO4. The
crude material remaining after evaporation of the solvent in vacuo was puri®ed by column
chromatography (eluent: petrolether: CH2Cl2 ˆ 1:1; elution sequence: 12, 13 and 14, 15, respectively.
12: yield: 47%; mp.: 117ꢀC; 1H NMR (CDCl3): ꢄ ˆ 4.86 (s, 1H, CH), 6.40 (d, 5J ˆ 2:4 Hz,
CHfuranone), 6.90 (m, 2H, arom.), 7.06 (m, 3H, arom.), 7.25 (m, 2H, arom.), 7.50 (m, 2H, arom.) ppm;
13C NMR (CDCl3): ꢄ ˆ 52.6 (CH), 63.9 (q, 2J ˆ 26:2 Hz, C-3furanone), 102.4 (d, 4J ˆ 14:9 Hz,
2
2
C-4furanone), 115.2 (d, J ˆ 10:7 Hz, C-12-fluorophenyl), 115.7 (d, J ˆ 21:4 Hz, C-34-fluorophenyl), 115.9
2
2
1
(d, J ˆ 21:4 Hz, C-34-fluorophenyl), 116.3 (d, J ˆ 21:1 Hz, C-32-fluorophenyl), 123.4 (q, J ˆ 284:5 Hz,
CF3), 124.8 (d, 3J ˆ 3:7 Hz, C-62-fluorophenyl), 127.9 (d, 4J ˆ 2:0 Hz, C-52-fluorophenyl), 130.5 (d,
3J ˆ 8:0 Hz, C-24-fluorophenyl), 130.6 (d, 3J ˆ 5:8 Hz, C-24-fluorophenyl), 132.4 (d, 3J ˆ 8:9 Hz,
C-42-fluorophenyl), 133.2 (d, 4J ˆ 3:2 Hz, C-14-fluorophenyl), 133.7 (d, 4J ˆ 3:5 Hz, C-14-fluorophenyl),
151.5 (d, 3J ˆ 3:3 Hz, C-5furanone), 160.8 (d, 1J ˆ 254:5 Hz, C-22-fluorophenyl), 162.3 (d, 1J ˆ 247:7 Hz,
C-44-fluorophenyl, 2x) 170.1 (d, 5J ˆ 2:3 Hz, C-2furanone) ppm; 19F- NMR (CDCl3): ꢄ ˆ 36.5 (m, 1F,
p-FC6H4), 36.2 (m, 1F, p-FC6H4), 33.5 (m, 1F, o-FC6H4), 10.0 (s, 3F, CF3) ppm; IR (KBr):
‡
ꢀ ˆ 1815, 1646, 1605, 1509 cm 1; MS (EI): m=z ˆ 245 [M±CH(C6H4F)2] , 225 [M±CH(C6H4F)2,
‡
‡
±HF] , 203 [CH(C6H4F)2] (100).
1
13: yield: 16%; mp.: 174ꢀC; H NMR (CDCl3): ꢄ ˆ 4.95 (s, 1H, CH), 6.82±7.09 (m, 6H, arom.),
7.24±7.45 (m, 6H, arom.), 8.18 (q, J ˆ 1:6 Hz, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 56.4 (d,
4
4J ˆ 4:3 Hz, CH), 89.5 (d, J ˆ 5:1 Hz, C-5furanone), 115.5 (d, J ˆ 21:0 Hz, C-34-fluorophenyl), 115.8
3
2
2
2
1
(d, J ˆ 21:5 Hz, C-34-fluorophenyl), 116.1 (d, J ˆ 22:6 Hz, C-32-fluorophenyl), 119.1 (q, J ˆ 270:6 Hz,
CF3), 123.4 (d, 2J ˆ 11:9 Hz, C-12-fluorophenyl), 124.5 (q, 2J ˆ 37:9 Hz, C-3furanone), 125.2 (d,

Reactions of Fluorinated Furans and Thiophenes
943
3J ˆ 3:2 Hz, C-62-fluorophenyl), 127.8 (d, 4J ˆ 3:3 Hz, C-52-fluorophenyl), 131.0 (d, 3J ˆ 8:0 Hz,
C-24-fluorophenyl), 131.1 (d, 3J ˆ 10:8 Hz, C-42-fluorophenyl), 132.3 (d, 4J ˆ 3:4 Hz, C-14-fluorophenyl),
133.4 (d, 4J ˆ 3:4 Hz, C-14-fluorophenyl), 158.3 (d, 1J ˆ 244:1 Hz, C-22-fluorophenyl), 158.3 (m, C-4furanone),
162.0 (d, 1J ˆ 247:0 Hz, C-44-fluorophenyl), 162.4 (d, 1J ˆ 248:5 Hz, C-44-fluorophenyl), 164.7 (C-2furanone
)
ppm; 19F NMR (CDCl3): ꢄ ˆ 36.9 (m, 1F, p-FC6H4), 36.8 (m, 1F, p-FC6H4), 35.9 (m, 1F,
‡
o-FC6H4), 12.8 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1790, 1508, 1361 cm 1; MS (EI): m=z ˆ 429 [M±F] ,
‡
‡
245 [M±CH(C6H4F)2] , 203 [CH(C6H4F)2] (100).
2-(4,40-Di¯uorobenzhydryloxy)-5-(4-¯uorophenyl)-3-tri¯uoromethylthiophene (14; C24H14F6OS)
Yield: 62%; oil; 1H NMR (CDCl3): ꢄ ˆ 6.14 (s, 1H, CH), 7.0 (s, 1H, CHthiophene), 7.02±7.15 (m, 6H,
2
arom.), 7.31±7.45 (m, 6H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 87.8 (CH), 114.4 (q, J ˆ 34:7 Hz,
2
2
C-3thiophene), 115.8 (d, J ˆ 21:6 Hz, C-3, C-5fluorophenyl), 116.0 (d, J ˆ 21:9 Hz, C-3, C-5fluorophenyl),
1
3
117.8 (C-4thiophene), 122.2 (d, J ˆ 270:3 Hz, CF3), 127.0 (d, J ˆ 8:0 Hz, C-2, C-6fluorophenyl), 129.0
3
4
(d, J ˆ 8:5 Hz, C-2, C-6fluorophenyl), 129.5 (d, J ˆ 3:3 Hz, C-1fluorophenyl), 130.7 (C-5thiophene), 135.0
(d, 4J ˆ 3:0 Hz, C-1fluorophenyl), 161.9 (q, 3J ˆ 3:5 Hz, C-2thiophene), 162.5 (d, 1J ˆ 248:0 Hz,
C-4fluorophenyl), 162.9 (d, J ˆ 248 Hz, C-4fluorophenyl) ppm; 19F NMR (CDCl3): ꢄ ˆ 36.0 (m, 1F,
1
p-FC6H4), 34.9 (m, 2F, p-FC6H4), 19.8 (s, 3F, CF3) ppm; IR (®lm): ꢀ ˆ 1604, 1575, 1515, 1421,
1400 cm 1; MS (EI): m=z ˆ 464 [M] , 261 [M±CH(C6H4F)2] , 203 [CH(C6H4F)2] (100), 183
‡
‡
‡
‡
[CH(C6H4F)2, ±HF] .
3-(4,40-Di¯uorobenzhydryl)-5-(4-¯uorophenyl)-3-tri¯uoromethyl-2(3H)-thiophenone
(15; C23H14F6OS)
1
Yield: 8%; mp.: 129ꢀC; H NMR (CDCl3): ꢄ ˆ 4.84 (s, 1H, CH), 6.41 (s, 1H, CHthiophenone), 6.86±
7.25 (m, 6H, arom.), 7.34±7.53 (m, 6H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 53.7 (CH), 74.2 (q,
2
2J ˆ 23:6 Hz, C-3thiophenone), 112.5 (C-4thiophenone), 115.7 (d, J ˆ 21:1 Hz, C-3, C-5fluorophenyl), 115.8
(d, 2J ˆ 21:7 Hz, C-3, C-5fluorophenyl), 116.5 (d, 2J ˆ 22:5 Hz, C-3, C-5fluorophenyl), 123.6 (q, 1J ˆ
286:7 Hz, CF3), 128.4 (d, 4J ˆ 3:2 Hz, C-1fluorophenyl), 128.5 (d, 3J ˆ 8:8 Hz, C-2, C-6fluorophenyl),
130.5 (d, 3J ˆ 8:0 Hz, C-2, C-64-fluorophenyl), 130.8 (d, 3J ˆ 8:0 Hz, C-2, C-6fluorophenyl), 133.5 (d,
4J ˆ 3:6 Hz, C-1fluorophenyl), 134.5 (d, 4J ˆ 3:4 Hz, C-1fluorophenyl), 144.7 (C-5thiophenone), 162.2 (d,
1J ˆ 247:8 Hz, C-4fluorophenyl), 163.9 (d, 1J ˆ 252:5 Hz, C-4fluorophenyl), 199.9 (C-2thiophenone) ppm;
19F NMR (CDCl3): ꢄ ˆ 36.4 (m, 2F, p-FC6H4), 31.1 (m, 1F, p-FC6H4), 10.7 (s, 3F, CF3) ppm;
‡
‡
IR (KBr): ꢀ ˆ 1716, 1604, 1508 cm 1; MS (EI): m=z ˆ 464 [M] , 261 [M±CH(C6H4F)2] , 203
‡
‡
[CH(C6H4F)2] (100), 183 [CH(C6H4F)2, ±HF] .
2-Benzylmercapto-5-(4-chlorophenyl)-3-tri¯uoromethylfuran (17; C18H12ClF3OS)
To a solution of 1e (0.53 g, 2 mmol) and benzyl mercaptane (0.50 g, 4 mmol) in THF (5 cm3) at 0ꢀC,
NaH (0.12 g, 5 mmol) was added. The mixture was stirred at 0ꢀC until complete conversion of 1e (19F
NMR analysis), treated with ice/water, and extracted with ether. The organic phase was dried over
MgSO4. After evaporation of the solvent, the remaining crude product was puri®ed by column
chromatography (eluent: CH2Cl2/petrol ether).
1
Yield: 91%; oil; H NMR (CDCl3): ꢄ ˆ 4.15 (s, 2H, CH2), 6.73 (s, 1H, CHfuran), 7.27 (m, 5H,
arom.) 7.37 (m, 2H, arom.), 7.49 (m, 2H, arom.) ppm; 13C NMR: ꢄ ˆ 40.4 (CH2), 104.8 (q,
3J ˆ 2:4 Hz, C-4furan), 122.0 (q, 1J ˆ 268:5 Hz, CF3), 123.1 (q, 2J ˆ 37:6 Hz, C-3furan), 125.3, 127.6,
127.7, 128.6, 128.9, 129.1, 134.6, 136.7 (arom.), 145.9 (C-2furan), 155.2 (C-5furan) ppm; 19F NMR
(CDCl3): ꢄ ˆ 19.4 (s, 3F, CF3) ppm; IR (®lm): ꢀ ˆ 1536, 1480, 1396 cm 1; MS (EI):
‡
‡
‡
‡
m=z ˆ 368=370 [M] , 277/279 [M±C7H7] , 246 [M±C7H7S] , 91 [C7H7] (100).

944
K. Burger et al.
2-(Benzylamino)-5-(4-chlorophenyl)-3-tri¯uoromethylfuran (18; C18H13ClF3NO)
A solution of 1e (0.53 g, 2 mmol) and benzyl amine (0.43 g, 4 mmol) in THF (5 cm3) was stirred at
room temperature until 1e was completly consumed (19F NMR analysis), treated with ice/water, and
extracted with ether. The organic phase was separated, dried over MgSO4, and evaporated to dryness.
The remaining crude product was recrystallized from petrol ether.
Yield: 81%; mp. 79ꢀC; 1H NMR (CDCl3): ꢄ ˆ 4.57 (d, 3J ˆ 5:7 Hz, 2H, CH2), 4.74 (s, br, 1H, NH),
6.60 (s, 1H, CHfuran), 7.26±7.41 (m, 9H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 47.6 (CH2), 89.2 (q,
2J ˆ 37:8 Hz, C-3furan), 104.6 (C-4furan), 123.6 (arom.), 124.0 (1J ˆ 264:4 Hz, CF3), 127.5, 127.8,
3
128.6, 128.8, 128.9, 132.1, 138.3 (arom.), 143.5 (C-5furan), 154.5 (q, J ˆ 3:5 Hz, C-2furan) ppm; 19F
NMR (CDCl3): ꢄ ˆ 21.6 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 3485, 1637, 1603, 1472 cm 1; MS (EI):
‡
‡
‡
‡
m=z ˆ 351=353 [M] , 332/334 [M±F] , 260/262 [M±C7H7] , 91 [C7H7] (100).
5-(4-Methylphenyl)-2-(2-pyridylmethoxy)-3-tri¯uoromethylfuran (19; C18H14F3NO2)
To a solution of 1b (0.49 g, 2 mmol) and 2-hydroxymethyl pyridine (0.44 g, 4 mmol) in THF (5 cm3)
at 0ꢀC, NaH (0.12 g, 5 mmol) was added. Stirring was continued at 0ꢀC until the reaction was
complete (19F NMR analysis). The reaction mixture was treated with ice/water and extracted with
ether. The organic phase was dried over MgSO4, evaporated to dryness, and the residue was puri®ed
by column chromatography (eluent: CH2Cl2/petrol ether).
Yield: 78%; mp.: 84ꢀC; 1H NMR (CDCl3): ꢄ ˆ 2.35 (s, 3H, CH3), 5.52 (s, 2H, CH2), 6.58 (s, 1H,
CHfuran), 7.16 (m, 2H, arom.) 7.29 (m, 1H, H-5pyridine), 7.40 (m, 2H, arom.), 7.56 (m, 1H, H-3pyridine),
7.78 (m, 1H, H-4pyridine), 8.60 (m, 1H, H-6pyridine) ppm; 13C NMR (CDCl3): ꢄ ˆ 21.2 (CH3), 74.1
3
(CH2), 93.5 (q, 2J ˆ 38:9 Hz, C-3furan), 102.7 (q, J ˆ 2:3 Hz, C-4furan), 121.3 (arom.), 122.5 (q,
1J ˆ 265:7 Hz, CF3), 123.0, 123.2, 126.7, 129.5, 137.0, 137.6 (arom.), 145.2 (C-5furan), 149.3, 155.3
(arom.), 155.6 (C-2furan) ppm; 19F NMR (CDCl3): ꢄ ˆ 20.3 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1649,
‡
‡
‡
1443 cm 1; MS (EI): m=z ˆ 333 [M] , 241 [M±C6H6N] (100), 221 [M±C6H6N, ±HF] , 214
‡
‡
‡
‡
[M±CH3C6H4CO] , 193 [M±C6H6N, ±HF, ±CO] , 119 [CH3C6H4CO] , 92 [C6H6N] .
5-(4-Methylphenyl)-3-(2-thienyl)-3-tri¯uoromethyl-2(3H)-furanone (21; C17H13F3O2S);
5-(4-Methylphenyl)-5-(2-methylthien-3-yl)-3-tri¯uoromethyl-2-(5H)-furanone (22; C17H13F3O2S)
To a stirred solution of 1b (0.49 g, 2 mmol) and 2-hydroxymethyl thiophene (0.46 g, 4 mmol) in
THF, NaH (0.12 g, 5 mmol) was added at 0ꢀC. Stirring was continued until the reaction was
complete (19F NMR analysis). The reaction mixture was treated with ice/water and extracted with
ether. The organic phase was dried over MgSO4 and evaporated to dryness. Compound 21 can be
separated from the reaction mixture by column chromatography with a cooled column (eluent:
CH2Cl2/petrol ether). Compound 21 rearranges upon standing at room temperature to give
quantitatively 22.
21: yield: 5%; mp.: 90ꢀC; 1H NMR (CDCl3): ꢄ ˆ 2.37 (s, 3H, CH3), 3.43 (d, 2J ˆ 14:0 Hz, 1H,
2
CHa2), 3.75 (d, J ˆ 14:0 Hz, 1H, CHb2), 5.73 (s, 1H, CHfuranone), 6.88 (m, 2H, arom.), 7.18 (m, 3H,
3
arom.), 7.42 (m, 2H, arom.) ppm; 13C NMR (CDCl3): ꢄ ˆ 21.5 (CH3), 31.4 (q, J ˆ 2:4 Hz, CH2),
2
1
60.0 (q, J ˆ 27:4 Hz, C-3furanone), 96.8 (C-4furanone), 123.7 (q, J ˆ 282:9 Hz, CF3), 124.1, 125.4,
125.7, 127.0, 128.1, 129.5, 133.9, 141.2 (arom.), 156.7 (C-5furanone), 171.1 (C-2furanone) ppm; 19F NMR
‡
(CDCl3): ꢄ ˆ 6.0 (s, 3F, CF3) ppm; IR (KBr): ꢀ ˆ 1804 cm 1; MS (EI): m=z ˆ 338 [M] , 241 [M±
‡
‡
‡
‡
C5H5S] , 221 [M±C5H5S, ±HF] , 193 [M±C5H5S, ±CO] , 97 [C5H5S] (100).
22: yield: 46%; oil; 1H NMR (CDCl3): ꢄ ˆ 2.38 (s, 3H, CH3), 2.44 (s, 3H, CH3), 6.64 (d,
3J ˆ 3:2 Hz, 1H, CHthiophene), 6.70 (d, 3J ˆ 3:2 Hz, 1H, CHthiophene), 7.23 (m, 2H, arom.) 7.33 (m, 2H,
3
arom.), 8.20 (q, J ˆ 1:6 Hz, 1H, CHfuranone) ppm; 13C NMR (CDCl3): ꢄ ˆ 15.3 (CH3), 21.2 (CH3),
1
2
87.9 (C-5furanone), 119.7 (q, J ˆ 270:4 Hz, CF3), 123.2 (q, J ˆ 37:4 Hz, C-3furanone), 125.3, 126.0,
127.6, 129.7, 133.9, 137.8, 139.7, 143.0 (arom.), 158.1 (C-4furanone), 164.9 (q, 3J ˆ 2:8 Hz, C-2furanone
)

Reactions of Fluorinated Furans and Thiophenes
945
ppm; 19F- NMR (CDCl3): ꢄ ˆ 13.4 (s, 3F, CF3) ppm; IR (®lm): ꢀ ˆ 1786, 1359 cm 1; MS (EI):
‡
‡
m=z ˆ 338 [M] , 119 [CH3C6H4CO] (100).
Acknowledgements
The authors are grateful to Deutsche Forschungsgemeinschaft (Bu 277/20-1) and the Fonds der
Chemischen Industrie for ®nancial support.
References
[1] Part 2; Part 1: Burger K, Fuchs A, Hennig L, Helmreich B (2001) Tetrahedron Lett 42: 1657
[2] a) Rao YS (1964) Chem Rev 64: 353; b) Rao YS (1976) Chem Rev 76: 625; c) Knight DW (1994)
Contemp Org Synth 1: 287
[3] Tyvorskii VI, Kukharev AS, Kulinkovich OG, De Kimpe N, Abbaspour-Tehrani K (1998)
Tetrahedron 54: 1801
[4] Shengming M, Zhangjie S (1998) J Org Chem 63: 6387 and literature cited therein
[5] a) Ottlinger R, Burger K, Goth H, Firl J (1978) Tetrahedron Lett 50: 5003; b) Burger K, Ottlinger
R, Goth H, Firl J (1982) Chem Ber 115: 2494
[6] Burger K, Helmreich B (1992) J Prakt Chemie 334: 311
[7] Burger K, Helmreich B, Popkova VY, German LS (1994) Heterocycles 39: 819
[8] Burger K, Wucherpfennig U, Brunner E (1994) Fluoro Heterocycles with Five-Membered Rings.
In: Katritzky AR (ed) Advances of Heterocyclic Chemistry, vol 60. Academic Press, p1
È
È
[9] a) Burger K, Hoû E, Geith K (1990) Synthesis 360; b) Hubl D, Ganzer M, Arndt F, Rees R, Ger
Offen DE (1988) 3 614 229; (1988) CA 109: 12441c
[10] Tietze L (1996) Chem Rev 96: 115 and literature cited therein
È
[11] Fuchs A (1999) PhD Thesis, Universitat Leipzig
[12] Pinhey JT, Schaffner K (1968) Aust J Chem 21: 2265
[13] Arnold RT, Kulenovic ST (1980) J Org Chem 45: 891
È
[14] a) Steglich W, personal communication; b) Lomar R (1980) PhD Thesis, Universitat Bonn
[15] Unpublished results
[16] Beuck M (1999) Angew Chem 111: 663; (1999) Angew Chem Int Ed 39: 631
[17] Zhao D, Xu F, Chen C, Tillyer RD, Grabowski EJJ, Reider PJ (1999) Tetrahedron 55: 6001
[18] Reinaud O, Capdevielle P, Maumy M (1987) Tetrahedron 43: 4167
[19] Andreichikov YS, Gein VL, Ivanenko OI, Brigadnova EV, Maslivets AN (1988) J Org Chem
USSR (Engl Transl) 24: 1007
[20] Gilchrist TL, Storr R (1979) Organic Reactions and Orbital Symmetry, 2nd ed. Cambridge
University Press, Cambridge, p 257 and literature cited therein
[21] Burger K, Gaa K, Geith K, Schierlinger C (1989) Synthesis 850
Received March 9, 2001. Accepted April 2, 2001